WO1997012406A1 - Method for producing and/or treating refractory filaments, especially superconductive filaments - Google Patents

Abstract

A process is disclosed for producing fibers of refractory material. In one embodiment, first, a dispersion of particles of refractory material is prepared. The dispersion is then mixed with a carrier solution of a salt of cellulose xanthate to form a spin mix. From the spin mix, a filament of regenerated cellulose is formed using general wet spinning techniques. The filament has the particle dispersed therein. The filament is heated to sufficient temperatures and over sufficient durations to remove substantially all of the regenerated cellulose and to sinter the particles to thereby form the fibers of refractory material.

Description

METHOD FOR PRODUCING AND/OR TREATING REFRACTORY FILAMENTS, ESPECIALLY SUPERCONDUCTIVE FILAMENTS

REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of co- pending U.S. Application No. 08/470,291, filed June 6, 1995, which is a continuation-in-part of co-pending U.S. Application No. 08/197,673, filed February 17, 1994, now abandoned, which is a continuation of U.S. Application No. 07/914,996, filed July 16, 1992, now abandoned, which, in turn, is a continuation of Application No. 07/580,132, filed on September*10, 1990, now abandoned, which is a continuation-in-part of U.S. Application No. 07/398,895, filed August 28, 1989, now abandoned.

BACKGROUND OF THE INVENTION The ability to produce refractory filaments of substantial length and useful flexibility is desirable for many applications. Among these applications are fiber reinforcement for composite ceramic and metal matrix composites. In a more specialized field, relatively long and flexible refractory filaments of superconductive material having relatively high critical current density (especially with critical temperatures Tc greater than 77K) would make it possible to produce cables or wires of high-temperature superconductive material which may be wound, for example, into the coils of electromagnets.

Unfortunately, such filaments have been extremely difficult to fabricate into wire or tape shapes of the desired strength and flexibility. Production of superconductors is further complicated due to difficulties in achieving the desired critical current density. Additionally, previously known ceramic fiber production methods are material specific. Among the methods for making such filaments which have been previously explored for making superconductive filaments are the following: (1) Methods based on certain advanced ceramic forming methods, such as extrusion and tape casting. These typically result in a product having low mechanical strength after it is fired; (2) Extension of the metal-working and diffusion/oxidation techniques originally developed for the low-temperature alloy superconductors, such as NbTi and Nb3Sn. Typical of these processes is the so-called "powder-in-tube" process in which a high-temperature superconductive ceramic powder is packed into a silver tube, which is then rolled or drawn into a wire configuration. The wire is generally cracked by the tensile stress either during annealing or during subsequent testing due to the differences in thermal expansion between the silver sheath and the oxide core; (3) Organic intermediary methods such as colloidal, sol-gel, and metallo-organic polymer. Each of these results in low-density products, due to the very low level of refractory material present in the green body, i.e., prior to heat treatment. Also, the colloidal and sol-gel approaches are very slow and hence unlikely to offer commercially satisfactory processes; (4) Melting-solidification methods, such as melt-textured growth. These have the potential of obtaining dense, oriented crystal wire, but are inherently slow since they are limited by the dynamics of single-point crystal formation and growth; and (5) Alloy oxidation-diffusion methods which, because of the good ductility of amorphous alloy wire and easy control of oxygen concentration in the material through change in sample weight upon oxidation, have attracted attention for producing oxide-type ceramic superconductive wire. However, the process is limited by difficulties in the mixing of immiscible Y-Ba-Cu alloy stoichiometrically. (6) Conventional ceramic melt drawing methods are difficult to use due to the incongruent melting of 1-2-3 phase materials. Furthermore, the melting is not practical for high temperature ceramic.

Therefore, a need exists for a process of manufacturing ceramic fiber that provides control and flexibility over the material and configuration of the fiber made. The present invention fulfills this need.

SUMMARY OF THE INVENTION The present invention provides a process of producing fibers of refractory material. In one embodiment, first, a dispersion of particles of refractory material is prepared. The dispersion is then mixed with a carrier solution of a salt of cellulose xanthate to form a spin mix. Form the spin mix, a filament of regenerated cellulose is formed using general wet spinning techniques. The filament has the particle dispersed therein. The filament is heated to sufficient temperatures and over sufficient durations to remove substantially all of the regenerated cellulose and to sinter the particles to thereby the fibers of refractory material.

The present invention provides a method for producing a wide variety of refractory ceramic filaments, including both conductive and high-temperature superconductive filaments having improved properties.

The present invention also provides a method for manufacturing such filaments which have high flexibility, high strength, high current density, and high temperature capability, making them especially suitable for use in magnet coils, motor windings, sensors, data transmission wires, and all other applications in which it is desirable to have refractory material in fibrous form.

The present invention also provides such method which is easy and reliable to use, and which employ as components known types of steps and equipment that are themselves readily available in commercial form.

The present invention also provides such method which enables continuous and fast production of high-density grain-oriented filaments with relatively great strength, flexibility, and chemical stability. BRIEF DESCRIPTION OF THE DRAWINGS The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements, and wherein: Figure 1 is a schematic diagram of one preferred embodiment of the invention using a wet spinning technique; and Figures 2 is a block diagram illustrating a possible embodiment of the process of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION Referring now to the drawings, the general process is illustrated in block form in Figure 2. Block 201 depicts the first step in which a dispersion of particles of refractory material is prepared. Aside from the dispersion medium and the refractory material, the dispersion may also contain a dispersing agent and other constituents. The dispersing agent should be compatible with both the refractory powder and the viscose. In Block 202, the dispersion is mixed with a carrier solution or dispersion of a salt of cellulose xanthate to form a spin mix. Using wet spinning techniques, a filament of regenerated cellulose is formed from the spin mix as shown in Block 203. The cellulose filament has the powder dispersed therein. Next, in Block 204, the filament is heat treated which involves passing it through a firing furnace to pyrolize the carrier and to sinter the remaining refractory material particles to form a ceramic fiber. Through-out these steps, it is preferred that measures be taken to reduce the reaction of the refractory material with the other substances used in the process as shown in Block 205. The measures include reducing the reactivity of the refractory powder, reducing the reactivity of the other substances, and reducing the reaction time between the powder and the substances, or combinations thereof. In Block 206, subsequent processing steps are depicted which include annealing, metal impregnation, and coating. Each of these process blocks are discussed in greater detail below.

Preparation of Powder Dispersion The process begins by preparing a dispersion of particles of refractory material. In this disclosure, the term "powder" is used interchangeably with particles and refractory material particles. Furthermore, the term "dispersion" is intended to have broad meaning and is used to describe a particles of refractory material dispersed, suspended, or even dissolved in any manner in a liquid. The liquid or dispersion medium is usually water, but it can be nonaqueous or even a mixture of water and nonaqueous solvents. In order to avoid complications from impurities, the water should generally be deionized or distilled

The powder used must be a refractory material. As used herein, the terms "refractory material" means any material able to withstand the heat necessary to pyrolize the regenerated cellulose fibers without undergoing significant change such as oxidation or melting. The powder should also be capable of being converted to ceramic or metallic structures by sintering at temperatures above about 350 ^*C in oxygen, hydrogen, nitrogen or other environments. It is also desirable that the powder be able to withstand relatively high concentrations of water, acids and bases for periods of at least a few minutes to several hours or longer. Although desirable, it should be understood that by reducing the reactivity of the powder with the other substances used in the process, this resiliency is not required (discussed below) . The actual powder used is dictated by the type of fiber desired. The chemistry of the powder is selected such that the fiber will have the desired properties after the powder is sintered.

Suitable non-superconducting powders include ceramic and elemental metal powders. In this disclosure, the term ceramic refers to oxides, nitrides, carbides, and borides of metals or semi-metals and combinations thereof. Examples of such suitable materials include, but are not limited to, silicon carbide, aluminum nitride, silicon nitride, aluminum oxide, titanium carbide, hafnium oxide and zirconium oxide, titanium dioxide, molybdenum disilicide, lithium aluminate, ferrite, PZT (leadzirconium titanate) , elemental metals, and any other powdered refractory material having the general properties listed above.

Titanium suboxides are among the preferred non- superconducting powders. One such suboxide is a powdered, electrically conductive substoichiometric titanium dioxide having uniformly distributed within its molecular structure chemically combined metal selected from the group consisting of chromium, copper, nickel, platinum, tantalum, zinc, magnesium, ruthenium, iridium, niobium, vanadium, tin, and combinations thereof. Another preferred titanium suboxide is a powdered, electrically conductive substoichiometric titanium dioxide having the basic formula TiO_x, wherein x is a number in the region of about 1.55 to about 1.95, and preferably between about 1.65 to about 1.9, and more preferably between about 1.7 to about 1.8. The titanium oxide may predominantly be Ti40₇ and/or Ti₅0₉. The bulk titanium oxide may be in coherent or particulate form, and include a range of titanium oxide compositions. For solid material x should be greater than 1.67 for strength reasons. Additionally, an electrocatalytically active surface may be on at least a portion of its surface. The electrocatalytically active surface may includes a material selected from the group consisting of platinum group metals or alloys, platinum group metal oxides, lead and lead dioxide.

Regarding superconductive filaments, the method is applicable, but not limited, to making Y-Ba-Cu-O superconductor. Other rare earth (Re) elements (except Ce, Pr, and Tb) can be used instead of yttrium to form Re-Ba-Cu-0 compounds. Still other ceramic materials, for example Bi-Sr-Ca-Cu-O, may also be used, with or without doping elements such as lead, tin, and antimony. One such example is (Bi,Pb)2Sr2Ca2Cu30x. It also should be understood that the basic material from which the superconductive filaments are made need not be of the specific types enumerated above, and that other ceramic materials or even non-ceramic materials may be utilized in certain cases.

The metal oxide (e.g., Y-Ba-Cu-O) powder can be of either needle-shaped (tetragonal crystal structure) or spherical (orthorhombic crystal structure) . The use of the needle-shaped tetragonal crystals has advantages and disadvantages, both related to physical shape. The advantage is that there will be better mechanical alignment of the crystals during the extrusion process. The disadvantage is that more carrier is required to allow easy flow during that extrusion process. It should be mentioned that the use of the non-superconductive, needle-shaped tetragonal crystal particles in the spinning process instead of the superconductive, spherical orthorhombic crystal particles does not necessarily affect adversely the superconductivity of the final product; the final annealing of the filaments ensures that the final product is of the superconductive crystal structure. The duration of the final annealing step may be affected by the degree to which the stoichiometry of the material needs to be altered to achieve the desired superconductive crystal structure. For example, a suitable superconductive material is YBa₂Cu307-x (e.g., SC5-P, manufactured by HiTc Superconco of Lambertville, New Jersey) . When x is between 0.3 and 0.5, the ceramic particles are composed of needle-shaped, tetragonal crystals which are non-superconductive. When x is less than 0.2, the ceramic particles are composed of spherical, orthorhombic crystals which are superconductive. Either variety may be used. After the final annealing step, all of the material in the final product is of the superconductive structure.

The size of the particles plays a major role in the characteristics of the final product. Generally, the larger the particle size, the harder it is to extrude the powder/carrier spin mix in the wet spinning process, thereby requiring a higher ratio of carrier to powder. The more carrier, the more pores are left in the filaments after the carrier is removed during firing, which may adversely affect the current carrying capacity of the resulting filaments. On the other hand, larger particles will tend mechanically to align themselves along the filament axis during spinning to a greater degree than will smaller particles, especially the needle-shaped tetragonal crystal particles. The greater the degree of such alignment, the greater the resulting current carrying capacity. Thus, there are advantages and disadvantages with both large particle powders and small particle powders.

The average particle size and particle size distribution is generally limited on the high side by the size of the hole that the dispersion will be passed through to form a filament and the degree of stability of the dispersion, particularly in regard to settling of the larger particles. Due to filtration steps in the filament forming process, and, generally, to obtain a uniform dispersion, the particle size distribution should be as low as possible. In regard to average particle size that can be used, it should be possible to make larger filaments using powders of even over one hundred micrometers, but preferably less than forty micrometers, and more preferably less than ten microns, and even more preferably around one micrometer or less. In general, smaller particle size powders can mix more uniformly and intimately with the cellulose xanthate molecules, presumably resulting in fewer holes in the sintered fiber, better fiber physical properties and other advantages. However too small particle size can present other problems such as overly viscous dispersions.

The amount of refractory material in the dispersion should generally be as high as possible to obtain a fluid dispersion so that an excessive amount of water or other liquid is not added to the fiber formation process. Generally concentrations of around 50 percent by weight of the refractory material give suitable fluid dispersions, but higher or lower concentrations can be used as necessary. In general, more fluid dispersion mix better with the cellulose xanthate solutions, so the limits of excess water and fluidity must be balanced for the particular conditions.

In addition to refractory powder and a dispersing medium, the dispersion medium usually contains dispersing agents to uniformly disperse or suspend the refractory material. These dispersing agents can be one or a mixture of any chemical which exhibits surface activity at the interface of the refractory material and the liquid. Such dispersing agents, include but are not limited to various nonionic, anionic, cationic and amphoteric amphiphilic compounds which act as dispersants, emulsifiers, stabilizers, wetting agents, hydrotropes, coupling agents and the like, salts of inorganic acids, particularly various forms of phosphoric acid and silicic acid, salts of organic monomeric and polymeric acids, amines, aminoalcohols. When a salt is used as a dispersing agent, that salt is usually the sodium salt, particularly when the dispersion will be mixed with a dispersion of the sodium salt of cellulose xanthate. However, other salts such as ammonium, organic amine, alkali metal and alkaline earth can be used alone or in combination as necessary. Some particularly useful dispersing agents for the refractory materials of this invention are sodium silicate, sodium polymethacrylate, sodium polyacrylate, sodium alginate, the sodium salt of copolymers of acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like, aminopropanol, triethanolamine, ethoxylated and/or propoxylated alkyl amines, carboxylic acids, alcohols or phenols, ethoxylated and/or propoxylated tristyrylphenol, ethoxylated and/or propoxylated castor oil, sorbitan or glycerin, polyethylene glycols, polypropylene glycols, random or block copolymers of ethylene and/or propylene oxide having hydroxyl, methoxy or other capped end groups, phosphate and sulfate esters of the ethoxylated and propoxylated adducts previously mentioned, sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, sodium alpha olefin sulfonates, sodium alkyl naphthalene sulfonates, sodium naphthalene formaldehyde sulfates, amine oxides, pendant amide, such as acrylamide, vinyl pyrrolidone and 2-acrylamido methyl sulfonic acid, homopolymers and copolymers, alkanolamides, ethoxylated alkanolamides, guar derivatives, sodium arboxmethylcellulose, hydroxyethyl cellulose, and methyl cellulose. Ammonium, amine and other methyl salts of the above dispersing agents can be used as appropriate. It is not uncommon to use several dispersing agents, each with their particular contribution to dispersing the refractory material, if the dispersion will encounter harsh demands in the process.

The dispersion can also contain other materials such as stabilizers and fiber formation modifiers, which will be discussed in more detail later. In addition, if the dispersion is to be mixed with a salt of cellulose xanthate dissolved or dispersed in water or another liquid containing excess sodium hydroxide or another base, then the dispersion may need to contain from about 0.1 to several per cent by weight of sodium hydroxide or other base, depending on the concentration of the base in the cellulose xanthate solution or dispersion, to prevent coagulation or precipitation of the cellulose xanthate.

The amount of dispersing agent(s) also varies widely as necessary to achieve a good dispersion without the refractory material settling. Generally, about one to ten per cent by weight of dispersing agent(s) , based on the weight of the refractory material, are used, but lower or higher amounts can be used as necessary.

The dispersion can be prepared by different procedures, but one particularly effective procedure is to mix the refractory material with the dispersing agents and other additives in water or other dispersing liquid in a ball milling jar with nonreactive milling media and mill for a period of time. The milling time is usually over night, but it can vary from a few minutes to several hours to several day depending on the particle size of the powder and its tendency to agglomerate and to react or interact with the dispersing liquid. The size of the jar and the number, shape and size of milling media depend on the milling action required and can be determined by one skilled in the art.

After the milling process, other materials may be added to the dispersion, for example, dispersing agents, especially post stabilizers. Sodium hydroxide or other base is generally added after the milling process and just prior to preparation of the spin mix, but it can be added at other times if it does not interact either chemically or physically with any of the components of the spinmix.

Preparation of Spin Mix The next step involves mixing the dispersion of refractory material with a carrier solution or dispersion of a salt of cellulose xanthate. This carrier solution is commonly referred to as viscose, and typically comprises sodium cellulose xanthate dissolved in aqueous sodium hydroxide solution. Viscose provides the basis for viscose rayon fiber formation using wet spinning techniques and is well known in the art (references listed under Filament Formation section below) . In the preparation of viscose, cellulose is soaked or steeped with sodium hydroxide or another aqueous base, pressed to remove excess base, shredded and then reacted with carbon disulfide in a reactor to form an alkali cellulose xanthate, usually sodium cellulose xanthate (sodium cellulose dithiocarbonate) . This cellulose xanthate derivative is then dissolved in aqueous base, typically sodium hydroxide, to form a viscous solution or dispersion commonly called viscose. The viscose may contain other chemicals or polymers known in the art, such as amines, polyglycols, hydrophilic polymers, flame retardants and the like, to improve fiber processing or properties. Other variations of preparing viscose can be practiced within in the scope of the present invention. For example, salts of cellulose xanthate other than sodium can be used, excess NaOH can be eliminated from the viscose, and a non- aqueous medium can be used. Moreover, the present invention is a applicable to alternative methods of producing rayon such as the lyocell process.

The powder dispersion and the carrier solution are then mixed to form the spin mix. The ratio of the powder to the cellulose in the viscose determines the composition of the resulting filament of cellulose containing the refractory material. If there are no losses of either material during the filament formation and purification process, then the weight ratio of refractory material to cellulose should be the same in the fiber as in the spin mix. The powder should generally constitute at least about 30% by weight of the total fiber forming material and preferably over 50% and more preferably over 80%. A major limiting factor in the weight ratio of refractory material to cellulose is the strength of the green or organic/inorganic filaments. Another factor is the volume ratio of the powder to the refractory material to cellulose. The volume ratio can differ widely from the weight ratio due to the large difference in specific gravities of refractory materials and cellulose.

The method of mixing the powder dispersion and viscose should generally be such that the powder and cellulose xanthate molecules are intimately mixed to avoid heterogeneous domains of the two materials in the filaments. This if a process of mixing particles with long polymer molecules. Although velocity of mixing generally gives better mixing of two materials, the mixing velocity is limited by introducing of air into the viscous viscose. Reducing viscosity by increasing the amount of water in the powder dispersion and/or the viscose dilutes the spin mix, resulting in more water to be disposed of in the filament formation process. Although other factors such as the amounts of sodium hydroxide in the powder dispersion and the viscose, the amounts and types of dispersants and other additives in the powder dispersion and even the addition of dispersing agents to the viscose may be utilized, a preferred method of preparing the spin mix is to add the selected amount of viscose to the powder dispersion of 50% by weight of the powder dispersed in water and stirring vigorously by hand until any color striations are no longer visible and the color is uniform. The resulting spin mix is deareated by placing it under vacuum, using regular viscose preparation techniques, for as long as necessary to remove the air that was introduced during the mixing process.

Although it is preferred to prepare a powder dispersion and mix it with viscose, filaments of the invention can be obtained by dispersing the powder directly in the viscose by selection of the proper dispersing agents. In this case the dispersing agents may be blended with the powder, premixed with the viscose or a combination of the two. If the powder is not destroyed in the process, it can also be added, with the necessary dispersing agents, to the alkali cellulose either before or after it is reacted with carbon disulfide but before it is dissolved or dispersed in aqueous alkali or other liquid medium. This procedure should give the best mixing of the two materials.

After deareation of the spin mix, it can now be "spun" to form filaments, ripened by conventional viscose techniques to the proper "spinning" condition or frozen for a period of approximately 18 hours or longer and then thawed to a liquid to "spin" to form filaments. The latter two procedures, particularly freezing, can give better fiber formation, presumably by better mixing of the two separate dispersions and consequently the two different materials.

Filament Formation Regenerated cellulose filaments are formed from the spin mix using wet spinning techniques. These techniques are known in the art. Reviews and descriptions of the art and viable commercial processes and reviews include: John Lundberg and Albin Turbak, "Rayon" in Kirk-Othmer Encyclopedia of Chemical Technology 3rd ed. , Vol. 19, pp. 855-880, John Wiley & Sons, Inc. (1982), R. L. Mitchell; G. C. Daul, "Rayon," in Encyclopedia of Polymer Science and Technology, Vol. 11, pp. 810-847, Interscience Publishers, a division of John Wiley & Sons, Inc., (1969); Joseph W. Schappel, "Rayon" in Chemical and Process Technology Encyclopedia, pp. 969-975, (1973); and H. Peter von Bucher, "Viscose Rayon Textile Fibers," pp. 7-42 and W. J. McGarry and M. H. Priest, "Viscose Rayon Tire Yarns," in H. F. Mark, S. M. Atlas and E. Cernia eds., Man-Made Fibers, Science and Technology, Vol. 2, Interscience Publishers, a division of John Wiley & Sons, New York, 1968.) E il Kline, "Xanthates" in Cellulose and Cellulose Derivatives, Part II, Second Edition, pp. 959-1018, Emil Ott and Harold M. Spurlin Coeditors, Volume V of High Polymers Series, Interscience Publishers, New York, 1954. It should therefore be obvious to someone skilled in the art that the present invention may be practice within the scope of the claims using a variety of different wet spinning techniques.

The following is an overview of using one wet spinning technique of viscose rayon:

Wood pulp cellulose is soaked or steeped in approximately 18% by weight sodium hydroxide solution at 25 degrees C for approximately 25 minutes and then pressed under high pressure to a pressed weight ratio of 2.6-3.0 to give an alkali cellulose which is approximately 34 wt. % cellulose, 15.3 wt. % NaOH and the remainder water. This alkali cellulose is then shredded to produce a "white crumb" which now has a more uniform distribution of sodium hydroxide. The shredding also heats the alkali crumbs to about 30 to 32 "C, which is a temperature for the next step of aging. In the aging process, which decreases and controls the cellulose DP (degree of polymerization) , the alkali crumbs stand in covered containers in a temperature controlled room for about 24 to 40 hours. The aged crumbs are then added to a churn where about 32 wt. % carbon disulfide is added and the temperature maintained at approximately 32'C for about 75 to 90 minutes while the exothermic reaction to form sodium cellulose xanthate takes place. Typically only about 75% of the CS2 reacts with the alkali cellulose while the remainder is consumed in forming by-product trithiocarbonate through side reactions. The xanthate crumb is then dumped into large, stirred tanks containing sodium hydroxide solution to dissolve the sodium cellulose xanthate to result in a honey-like, viscous solution called viscose. The viscose is then filtered to remove fibers and gelled and then ripened so that it will coagulate readily in spinning. During ripening, the xanthate concentration drops significantly. The xanthate groups are also redistributed more uniformly throughout the cellulose molecules. The ripening process generally takes place at about 18^βC for about 24 to 40 hours. Readiness for spinning is determined by a salt test, generally measured by the weight percentage concentration of a NaCl solution required to coagulate a drop of viscose. The viscose now typically consists of about 9.5 wt. % cellulose, about 6 wt. % NaOH and has about 0.9 to 1.1 wt. % xanthate sulfur. During ripening, the viscose is subjected to a deaeration process, usually about 22 in. of Hg for about 12 hours or more to remove dissolved air that was introduced during the various steps of viscose preparation.

The refractory material dispersion is usually mixed with the viscose just prior to spinning and subjected to another deaeration process to remove air that was introduced during the mixing step. However, the refractory material dispersion can be mixed with viscose just after dissolving and filtering, at some point in the ripening step or even in the dissolving step. The major objective in spinning is to control coagulation versus regeneration rates and the use of the differences in these rates to optimize stretching, which aligns the cellulose molecules along the fiber axis to impart strength and other desired physical properties to the filaments. In the spinning process, viscose is extruded into a bath containing both salt and acid. The salt is usually sodium sulfate at a concentration high enough so that the cellulose xanthate molecules coagulate and water is removed from the entering viscose. The concentration of sulfuric acid relative to the concentration of sodium sulfate is critical in controlling the amount of water removed from the newly formed filaments before the system is rigidly fixed by the acid removing the solubilizing xanthate groups. Stretching must be balanced in these transformations. When the refractory material is added to the viscose, it then becomes suspended and locked in the newly formed cellulose as these various steps are taking place.

The filaments are next purified with water and other chemicals as necessary, either continuously or in a batch process, and then dried. A finish to impart lubricity to the filaments for further processing or other chemicals (to hold the filaments together or for subsequent processing) may also be applied to the filaments.

Spinnerets used in wet spinning can vary widely, having nozzle holes of varying number (ranging from 1 to 20,000), size (ranging from about 18 to 400 microns or more) , and shape can be employed depending on the desired characteristics of the final product. Combinations of two or more spinnerets, either the same or different, in the spinbath can also be used. The shapes of the holes can vary widely to produce round, ribbon, lobate, hollow tube-like, triangular, trilobal, "Y", snowman, kidney bean or any other shape filament. The shape of the filaments in the wet spinning process, however, is dependent on other factors, such as regeneration and coagulation conditions (e.g., viscose composition and temperature, spinbath composition and temperature, spinning speed and other factors) . Again, it should be understood that any known technique to affect filament shape and size may be practiced within the scope of the present invention.

The spin bath, also referred to as an acid or coagulation bath, generally is aqueous, and contains both salt and acid. There are specialty situations in the literature where two baths are used, the first being a spin bath containing salt and some acid and the second being a regeneration bath containing acid and some salt. Another specialty spinning situation that has been used extensively commercially and could have advantages here is "tube spinning". It is described in the references. The most common example of a spin bath is an aqueous solution of sulfuric acid (H₂S0₄) and sodium sulfate salt (Na2S04) , the latter ensuring that the sulfate solution behaves as a dehydrating system that removes water from the viscose. Sodium sulfate, potassium sulfate or another salt can be used as the salt for controlling the extent of water removal from the viscose before the filaments are made rigid by the acid, which removes the solubilizing xanthate groups.

In order to increase the strength of the filament, which is quite desirable when forming the mixed fibers of the invention, the regeneration rate can be increased by as much as 400 to 500% or more by the use of additives, both in the viscose and in the spinbath. This retardation of the regeneration rate allows much greater stretching, imparting significantly higher stretch to the filaments. The most common additive is the use of zinc sulfate in the spinbath. In addition, hundreds of combinations of additives to the viscose and the spinbath have been investigated, but commercial systems usually use an amine, particularly dimethylamine or the ethylene oxide adduct of an alkyl amine such as cocoa amine, and polyethylene glycol, particularly of ca 1500 molecular weight or an ethylene oxide adduct of phenol or an alkyl phenol. The amines are usually added to viscose. The polyether glycol can be added to viscose or the spinbath or both. The concentrations of these additives are typically less than about 5% on the weight of cellulose in the viscose and usually only from about 1% to about 2% on the weight of the spinbath when added to the spinbath.

Other modifications of the process usually involve the addition of modifiers in regard to achieving higher strength and higher modulus fibers, namely higher DP and higher purity cellulose in the viscose, higher degrees of xanthation, lower amount of sodium sulfate in the spinbath, lower spinbath temperature, slower spinning speed and other modifications. Other compositions of acid baths and wash baths, such as mild acid phosphoric acid, hydrochloric acid, acetic acid and the like, water and salt solutions, or nonaqueous compositions, such as ethylene glycol and the like, can also be employed.

Varying the concentrations and compositions as well as the temperature of these baths will affect the durations for which the filaments need to be exposed. The temperature of the baths can vary from ambient temperature, or cooler, to 100 degrees Celsius, or higher in the case of nonaqueous baths. It should be understood that just as one balances variables in the viscose process for pure rayon fibers, such as decreasing the acid concentration in the spinbath and or decreasing the spinbath temperature if the viscose contains less sodium hydroxide or if the viscose has a lower salt index and is more mature, the same type of balance is required when making the ceramic fibers of this invention. However, the particular conditions are likely to be different when forming the fibers of this invention than when forming 100 per cent rayon fibers. For example, the spinbath acid and possibly other component concentration will usually be lower for the fibers of this invention than for pure rayon, presumably because of dilution of the viscose. Yet this reduction in concentration may not necessarily be proportional to the dilution of the viscose.

Although it has generally been found with 100% cellulose fibers in the viscose rayon process that very low amounts of amine and ethoxylated adduct modifiers are effective and larger amounts may even be harmful, it has surprisingly been found that with the mixed organic/inorganic fibers of this invention, that the addition of a large amount of amines, particularly amines that can also serve as dispersants, and/or polyethylene oxide or similar chemicals to the spin mix allow higher stretch, resulting in significantly higher fiber strength. These additives have been found to be most effective when they are incorporated into the preparation of the refractory material dispersion before it is mixed with viscose. The additives are also more effective when the spin mix is aged for at least several hours and even overnight. Freezing the spin mix overnight or longer, even for several days or weeks is also quite effective. This use of additives is surprisingly also effective when the viscose contains the usual amine and polyether additives used commercially, at lower concentrations, for improving the strength of 100% cellulose fibers.

Fiber strength can be quite significant in the fibers of this invention since the very high amount of non-load bearing material in the form of the refractory material and the very low amount of load bearing material in the form of cellulose gives fibers of significantly lower strength than fibers of 100% cellulose or fibers of high amounts of cellulose and low amounts of non-load bearing inorganic material. Therefore the unexpected advantage of stronqer fibers by the use of these extra additives.

Particularly effective additives are 2-amino-l-propanol and polyethylene glycol with a molecular weight of approximately 1500. These additives are effective when used separately but are particularly effective when used in combination, usually in ratios of from about 75:25 to 25:75. The concentration of total additives can vary widely and should be at least in the range of that used in the 100% cellulose fiber art. However, these additives are particularly effective when used at concentrations of from about 2 to 10%, and preferably from about 4 to 8%, by weight on the weight of the refractory material in the refractory material dispersion. When the refractory material dispersion is mixed with viscose to give a ratio of 80:20 by weight refractory material to cellulose, 6% on the weight of the refractory material is 24% by weight on the weight of cellulose, far above the amount used with commercial viscose rayon fibers.

Other aminoalcohols such as triethanolamine, diethanolamine, monoethanolamine, ethoxylated and/or propoxylated amines, aminomorpholine, aminophenol, aminopropanediol, aminomethyl propanol, aminomethylpropanediol, diethylethanolamine, amino pyridine, 2-(2-aminoethylanino)ethanol, (2-(2-aminoethoxy) ethanol, aminoethylpropanediamine, aminomethylbutanol, amino- carboxylic, sulfuric, sulfonic and phosphoric acids, di-, tri- and tetra-amines, polyamines, copolymers of ethylene oxide and propylene oxide, polypropylene glycol and propylene oxide and other alkylene oxide adducts as well as other viscose modifiers as reported in the literature can be used.

Heat Treatments After being formed, the cellulose filaments with the powder dispersed therein are heated. The heating serves to pyrolize the filaments and sifter the remaining refractory powder to produce a ceramic fiber. Prior to heating, the filaments may be woven, braided, knitted, tufted, wrapped or wound.

The techniques used for pyrolizing and sintering are known in the art. A tubular furnace or a box furnace can be used for heating the filaments. During the initial stages of firing, at temperatures around 200°C to 600°C, the carrier is driven out of the filaments. Sintering of the ceramic particles occurs at higher temperatures of about 750°C to about 2200°C, and higher as needed, according to a standard sintering curve in air, or, on occasion, in a controlled atmosphere, e.g., hydrogen, nitrogen or argon. After firing, the filaments are ready for further processing.

Stabilization of Powder Although most aspects of the viscose rayon process as used commercially or as described in the prior art may be practiced with the present invention, steps should be taken to reduce the reaction of the powder with the other substances. In this context, the term reaction refers to the powder's chemical interaction or physical reaction with other substances that diminishes the desired properties of the ceramic fiber. The terms "stabilization," "stabalize," and "chemically stable" refer to or otherwise concern the powder's low reactivity with another substance(s) . Without such measures, many powders, especially superconductive materials or precursors, will tend to react thereby hampering the desired filament formation. For example, just adding Y-Ba-Cu-O or similar superconductors to viscose will not produce the fibers of this invention. First, Y-Ba-Cu-0 is extremely sensitive to water, presumably because of reaction or interaction. Water is very abundant in the viscose rayon process. Y-Ba-Cu-0 is also quite reactive with sodium hydroxide and sulfuric acid as well as other chemicals used in the viscose rayon process. Moreover, a suspension of Y-Ba-Cu-O in water will gel essentially immediately when mixed with viscose, presumably by the reaction of barium and possibly copper with the cellulose xanthate groups to render the cellulose derivative insoluble. Therefore, different measures must be taken in order to produce Y-Ba-Cu-O and other reactive superconductive and even reactive non-superconductive fibers of this invention by the viscose rayon process.

Reducing the reaction of the powder and the other substances used in the process may be accomplished in Process Blocks 201-203 (Figure 2) by reducing the reactivity of the powder, reducing the reactivity of the substances, replacing the reactive substances in the process, reducing the reaction time between the powder and the substances, and combinations thereof.

The refractory material may be modified either chemically or physically to protect it from the other substances. For example, this can be done by forming an organic barrier or coating around the powder particles which would be pyrolized during heating. The barrier coating forms a hydrophobic barrier around the reactive powder particles to prevent or delay reactions with cellulose xanthate, sodium hydroxide, sulfuric acid, water and other viscose rayon chemicals. Chemicals that may be used as barriers include, but are not limited to, ethylene, propylene and other olefin homopolymers and copolymers, especially with functional monomers such as acrylic acid, maleic acid, maleic anhydride, hydroxyethyl methacrylate, vinyl pyrrolidone and the like, hydrocarbon waxes, fluorocarbon polymers such as polytetrafluoroethylene, polyvinylidene fluoride, perfluorinated acrylates and methacrylates, urethanes and other polymers, polyamides, polyurethanes, polyesters, polyethers, polyvinyl chloride, acrylate and methacrylate ester homo and copolymers and other polymers and oligomers that will form a coating or barrier around the powder particles to protect the powder from the reactive chemicals in the process. Furthermore, it has been found that plasticizers, particularly hydrophobic plasticizers such as dioctyl adipate, dioctyl phthalate and dioctyl terephlalate and the like and more hydrophobic amphiphilic compounds enhance and maybe even extend the barrier effect, allowing less coating material to be used. The barrier or coating is preferably applied to the powder from a nonreactive organic solvent, preferably hydrocarbons, but also esters, amides, and even certain alcohols. The solvent can be removed or left with the powder. The coated powder is then dispersed in water, with the proper dispersants, as described previously. The amount of coating can vary from less than one per cent of the weight of the powder to 50% or more and preferably from about 3% to about 15%. In general, lower amounts of protective barrier or coating are preferred. The protective barrier or coating is then generally removed in the heat treatment process.

Furthermore, an inorganic compound may be added to the refractory material to stabilize it. Yet another method of reducing the powders reactivity is by using a less reactive form of the powder. This can be accomplished by using a precursor of the desired refractory material. This precursor is then converted to the desired refractory material during the process. For example, the dispersion may comprise a raw mix of yttrium oxide, barium carbonate, and cupric oxide. During heating, the raw mix is converted to the superconductive Y-Ba-Cu-O.

Ractivity may also be lowered by modifying the dispersion and/or spin mix. In preparing the dispersion, a medium can be used that has relatively low reactivity with the refractory powder. The refractory material, for example, may be dispersed in an aqueous solution that has some type of protective action, such as an aqueous salt and/or a cheelant solution with and without certain amphilphilic compounds. It has been found that reactions of Y-Ba-Cu-O and similar materials are delayed significantly by suspending them in salt solutions, such as sodium, potassium and similar halide, sulfates, phosphates, acetates, citrates, EDTA (ethylene diamine tetraacetic acid) and other organic and inorganic salts. Specifically, reduced reactivity is noticed when suspending Y-Ba-Cu-O in ISOTON (see Example 5C) . Another alternative is to disperse the refractory material in non- aqueous mediums such as alcohols, ketones, esters, amides, ethers, chlorinated solvents, or, more preferably, aromatic and aliphatic hydrocarbons without functional groups.

In preparing the spin mix, a carrier solution can be used that has relatively low reactivity with the refractory powder. For example, alternative salts of cellulose can be used in the carrier solution, or excess hydroxide can be removed from the solution by ion exchange. Additionally, the alkali cellulose xanthate can be dispersed in a non-aqueous medium as described above. Stabalizers such as aminopropanol and other additives may also be added to the spin mix, particularly if Ti02 and titanium suboxides (described above) are used.

In regenerating the cellulose, a spinbath can be used that has relatively low reactivity with the refractory powder. This includes using mild phosphoric acid, hydrochloric acid, acetic acid and the like, water and salt solutions, or nonaqueous compositions, such as ethylene glycol and the like. Additionally, less reactive modifiers can be used.

Viscose can be coagulated with alcohols, salts or a weak acid, or a combination of these agents, to give a reasonably stable precipitate of sodium cellulose xanthate. This precipitate can be purified, dried and then mixed with the refractory powder and redispersed in water or another liquid. Aminopropanol and other additives also stabalize the spin mix, particularly Ti02 and Conduxites, and allows for improved spinning.

Another way of reducing the powder's reaction during the regeneration stage is to reduce the reaction time. This can be done by preparing and de-aerating the viscose and the powder dispersion separately, and to mix the two in-line just before the spinneret.

Subsequent Processing Annealing: After sintering, the ceramic fibers may be annealed using traditional annealing processes. Although not always necessary, annealing improves the mechanical and electrical properties of the fibers. Moreover, it often completes the process of transforming all of a non-superco/nductive tetragonal lattice in the filaments to the superconductive orthorhombic crystal structure. The filaments are typically annealed in an oxygen atmosphere. In one particular annealing processs, the fiber is soaked at 950°C for 1 to 10 hours, then cooled at 25°C/hr. to 800°C, then cooled at 5°C/hr. to 400°C, and finally at 25°C/hr. to room temperature. If any weaving or braiding of the filaments is desired, it may be performed after this annealing step.

Metal Impregnation: There are many advantages to impregnating the fibers with metal such as silver. The metal increases the strength and flexibility of the filaments by inhibiting crack propagation along grain boundaries, and provides very low contact resistance and lower overall resistivity at temperatures above the superconductive critical temperature. The metal, particularly silver, also improves stability by protecting the ceramic crystals from contamination and atmospheric attack, promotes grain growth and alignment of superconductive crystals, and cleans the grain boundaries of contaminants such as barium carbonate, thereby increasing current carrying capacity.

Regarding superconductors specifically, metal impregnation, particularly silver, improves not only the superconductive properties, but also the production process. The region of superconductivity extends into the silver itself, which makes possible continuous conductivity across connections between superconductive filaments. Silver also acts as a coolant media for heat transfer from the ceramic material to the coolant during superconducting implementations. Additionally, silver typically includes at least some silver oxide, which provides additional oxygen to the ceramic material during the final annealing process. It is during this step that the stoichiometry of the crystalline structure is changed from the non-superconductive tetragonal phase to the superconductive orthorhombic phase. The advantages to performing silver impregnation (and metal impregnation in general) exist for the treatment of all superconductive filaments, and not just those produced under the specific conditions described in the manufacturing procedure presented herein.

Coating: In lieu of or in addition to metal impregnation, a coating can be applied to the filaments to provide superior environmental stability. Suitable coatings include polymers such as textile sizing agents, including but not limited to polyvinyl alcohol, starch and starch derivatives cellulose esters, esters and other derivatives, acrylic and methacrylic acid and ester homopolymers and copolymers, polyesters with hydrophilic groups such as sulfonic acid and plyethylene oxide and the like , other polymers such as polyurethanes, polyamides, polyesters and the like. This coating should be applied after the final annealing step.

Schem ie BYawpie of Process Referring now to the schematic depiction of the process, without thereby limiting the scope of the invention, Figure 1 shows one preferred embodiment of the process for use in manufacturing high temperature ceramic superconductive filaments. Cellulose saturated with a base is reacted with carbon disulfide in reactor 1 to form sodium cellulose xanthate. The cellulose xanthate derivative is then dissolved in aqueous sodium hydroxide or another aqueous base to form a viscous solution or dispersion commonly called viscose. A dispersion of refractory material particles is mixed with the viscose.

This mixture is pumped by a metering pump 2 through a spinneret 3 directly into a spin bath 5 also known as the acid bath or spinbath at a rate of about 1 to 50 meters per minute or higher. The spinneret 3 comprises, in this example, a nozzle with 750 holes, each 80 microns in diameter. However the number, size, shape and distribution of the holes in the spinneret and the number, size and shape of the spinneret(s) can vary widely, depending on the specific conditions. A draw godet roll 6 pulls on the filaments 4 to draw the spun fiber through the spin bath. The bundle of parallel filaments 4 stays in the spin bath 5 for a period of from 1 second to about 3 minutes (or longer) , and then goes through a second hot aqueous acid bath at temperatures generally around 90 degrees Celsius to complete regeneration. The filaments are then purified with water and other chemicals as necessary (7) , either continuously or in a batch process and dried (8) . A finish to impart lubricity to the filaments for further processing or other chemicals may be applied to the filaments before they are wound onto a package (10) for subsequent processing. After passing through a dryer 8 to evaporate the water, the dried rayon cellulose-ceramic composite filaments 4 are fed over a drawing element 9 and wound onto a take-up reel 10 to await further processing.

The take-up reel 10 wound with filaments can be transported and used as the feed reel 11 for the pyrolizing and sintering step or subsequent weaving, braiding, tufting or winding prior to sintering. The filaments 14 are unwound from the feed reel 11 past the drawing elements 12 into the tubular firing furnace 13. Alternatively, furnace 13 can be a periodic furnace rather than a tubular one. During the initial stages of firing, at temperatures around 200°C to 400°C, the carrier is driven out of the filaments 14. Sintering of the ceramic particles occurs lower in the furnace, at higher temperatures of about 750°C to 1250°C depending upon the type of refractory powder (e.g., superconductive/non-superconductive) . After firing, the filaments 14 are again wound onto a take-up reel 15 to await further processing.

The take-up reel 15 then becomes the feed reel 16 for the next step of processing, which may be metal or other infilling material impregnation, or annealing. In annealing, the filaments 27 are fed from the reel 25 into the annealing furnace 26, where the filaments 37 are annealed. When producing superconducting filaments, this annealing completes the process of transforming all of the non-superconductive tetragonal lattice in the filaments to the superconductive orthorhombic crystal structure. The superconductive filaments 27 are then wound onto a take-up reel 28 for storage. If any weaving or braiding of the filaments is desired, it may be performed anytime after this annealing step.

In metal impregnation, the filaments 17 are preheated in the pre-heating furnace 18 at temperatures around 600°C to 2200°C, and then passed through the line guider 19 into a rough vacuum chamber 20 (mechanically pumped by pump 21 to a pressure of a few torr) to remove the air from the pores in the sintered filaments and thereby make room for infill solution (e.g., silver or other metal solution) to enter the pores. Since the unsintered fibers are inherently porous, a similar infilling can be performed on unsintered filaments to impart different pre-sifter or post-sifter properties to the fiber. The pre-heating in the pre-heating furnace 18 is not essential; however, pre-heating should be used if metal impregnation is performed on filaments that have not previously been fired to remove the carrier material.

To apply a silver coating, the filaments 17 are then passed through a room-temperature bath 22 containing a metallo-organic solution of 8% to 30% by weight Ag concentration for from about 6 minutes to about 1 hour. One possible solution is prepared by mixing Flexible Silver Coating SC4005 (produced by the Engelhard Corporation of Edison, New Jersey) with Thinner SC9025 (also produced by Engelhard) . After the filaments have passed through the bath, the silver solution has filled the pores and coated the surfaces and grain boundaries of the filaments 17.

The thickness of the silver layer can be controlled by changing such parameters as the silver concentration of the solution, the viscosity of the solution, and the duration for which the filaments are exposed to the solution. The greater the silver concentration, the thicker the silver layers. The more viscous the solution, the slower the impregnation and the longer the duration of exposure of the filaments in the solution required to achieve satisfactory impregnation. The greater the concentration of thinner, the less viscous the silver solution, the faster the impregnation. The longer the exposure of the filaments in the solution, the greater the thickness of the silver layer.

The filaments 17 are then drawn over the take-up godet 23 into the oxygen-filled post-heating furnace 24 in which temperatures of from 450°C to 750°C are maintained to drive off all of the metallo-organic solution except the silver. The filaments 17 are wound onto a take-up reel 25 to await further processing.

The metal impregnation (items 16 to 25 of Figure 1) can also be performed in alternative ways. Instead of a metallo-organic solution, a AgN03/EDTA aqueous ammonia solution could be employed. Silver is not the only metal which can be used either; metals such as gold, indium, lead, or tin could used instead. Depending on the application, impregnation with metals of low melting point or high thermal and electrical conductivity may be desired.

Metal impregnation (items 16 to 25 of Figure 1) is optional. If silver impregnation is omitted, such a procedure would start with powder suspension preparation, followed by spinning and pyrolizing/sintering, and then proceed directly to annealing. Consequently, items 16 to 25 of Figure 1 can be eliminated and the firing furnace 13 can be combined with the annealing furnace 26.

Each of the processing steps as generally described above ends up with the filaments being wound onto a take-up reel to await further processing. The primary reason for this step is the general incompatibility of consecutive steps in the manufacturing process, primarily due to the different rates at which the filaments can be fed during the different processing steps. The collection of filaments onto a take-up reel can be omitted anytime it becomes practical and more efficient to combine two consecutive steps into one continuous step. Thus, in many cases, it is possible to create one continuous process for the manufacture of refractory filaments.

Referring to Figure 1, the winding of the filaments 4 onto the take-up reel 10 at the end of wet spinning and the subsequent unwinding of the filaments 14 from the feed reel 11 at the beginning of pyrolizing and sintering can be eliminated, if the rate of filament spinning and the rate of travel of the filaments through the firing furnace are the same. Under similar conditions, the take-up reel 15 at the end of pyrolizing and sintering and the feed reel 16 at the beginning of silver impregnation can be eliminated. This will create the possibility of combining the firing furnace 13 and the pre-heating furnace 18 into a single furnace with varying temperature along its length. Similarly, the post-heating furnace 24 at the end of silver impregnation can be combined with the annealing furnace 26.

The detailed example described immediately above is just one possible procedure for making one type of superconductive ceramic fiber. Many of the steps in the procedure can be implemented in alternative ways which may prove advantageous for the particular application or result desired.

Product from Process The process described above can be used to produce both superconductive and non-superconductive ceramic fibers. Generally, it is preferable to produce ceramic fibers which are both strong and flexible, and, for superconductors, achieve as high a current carrying capacity and as high a critical temperature as possible. In particular, it is preferable to produce superconductive fibers having critical temperatures of 90°K or higher, critical current densities of over 1,000 A/cm2, and preferably over 7,500A/cm2, and more preferrably over 10,000 A/cm2 at 77K, and tensile strengths of 6,500 psi or greater. The ceramic fibers produced from this method find numerous applications. For example, conducting fibers such as titanium suboxides (described above) , PZT, and tin oxide, are useful as a fiber material composite in electrochemical, electromagnetic or electrorestrictive applications, wherein the fiber is present as continuous filament, a woven, felted or tufted mat, or as chopped filament sections. Such a material is useful, for example, as an active material support in batteries, a sensor, a smart structure, electromagnetic shielding, an electrode, an electrode in an electrochemical apparatus comprising means for recovering magnesium from sea water and any place that a material's resistance to corrosion and/or electrical properties need to be improved.

EXAMPLES Example 1 Production of a conductive titanium oxide ceramic fiber 1.75 grams of cupric chloride intercalated graphite was added to 50 grams of Ti02 from Tioxide Ltd. , England, mean particle size approximately one micrometer to introduce 0.72% cupric chloride into the structure of the titania after heat processing. The graphite was burned out per the procedures of U.S. Patent No. 4,931,213. 50 grams of deionized water containing 37 by weight of D,L-l-amino-2-propanol dispersant Aldrich Chemical, catalog # 11,024-8 were added to the resulting mixture and the combination ball milled for 16 hours using balls having a diameter of 0.5 to 2.5 inches to reduce/eliminate agglomerates. Approximately two milliliters of IN NaOH solution was pipetted into the milled mixture to raise the pH into the 11.0 to 12.0 range. To the mixture was added approximately 116 cubic centimeters 132 grams of viscose, containing 9.45% by weight of cellulose, 6.10% by weight unreacted NaOH, and 32% carbon disulfide by weight on the weight of cellulose, reacted with sodium hydroxide and the cellulose. This mixture was stirred for approximately one-half hour in a an ice bath at approximately 3j||c to avoid adding significant energy to the chemically unstable viscose. A high shear mixer was used in order to mix the components, to break up agglomerates and to further eliminate agglomerates. The stirred mixture then was filtered through a 25-40 mm cloth under <10 psi air pressure, then stored in a refrigerator for one hour at lOJjjC to deaerate the mixture and then allowed to equilibrate just before spinning at lδjjjC. The ceramic/viscose mixture was fed into a spinning machine through an enclosed and air pressured chamber feeding a constant pressure, variable volume "Zenith" metering pump. The pump forced the mixture through a conventional rayon spinnerette containing 100 round, of 89 mm diameter into a 43JjlC coagulatio and regeneration bath spinbath, flowing gently countercurrent to the discharging precursor, composed of 7.5% by weight of sulfuric acid (H2S04) , and 22.0% by weight of sodium sulfate (Na2S04) , with the remainder being deionized water. As in conventional viscose rayon technology, the sodium cellulose xanthate portion of the precursor first coagulated and precipitated, encapsulating the suspended inorganic compound, in the high salt spinbath and then reacted with the spinbath acid and regenerated the cellulose xanthate to cellulose to form approximately 20% by weight of cellulose and approximately 80% by weight of ceramic. Precursor was fed into the spin bath at a rate of approximately 16.0 grams per minute, and the spun fiber was drawn away from the spinnerette face by a take-up godet operating at a linear speed of approximately 6.0 meters per minute. The fibers were pulled from the first take-up godet by a second, faster paced godet, operating at a linear speed of approximately 7.0 meters per minute, thereby applying a 17.5% extension to the fiber to align both the rayon molecules and the ceramic particles along the longitudinal axis of the fiber. In its passage from first to second godet, the fiber was immersed in a boiling deionized water bath. This bath, continued the regeneration process started in the spinbath and began a cleansing/washing process. The fibers were wound continuously on a take up reel moving at the same linear speed as the second godet. The fibers were cleaned of sulfuric acid residue and other impurities by dipping the fibers, cut from the take up reel into 6 inch lengths, into two consecutive clean 95°C deionized water baths for two minutes each. The fibers were then allowed to air dry for approximately 24 hours. The diameters of the dried fibers were approximately 25 μm as determined using the micrometer scale on an Olympus microscope. The dried fibers were then filled with titanium isopropoxide by submersion for 5 minutes in a solution of titanium isopropoxide (containing 33% by weight titanium dioxide) in ethanol, followed by heating at 110°C to drive off the ethanol solvent. The immersion and heating steps were conducted a total of three times (i.e., repeated twice). Then the fibers were heat-treated as follows. In stage one. the fibers were heated in air to llOOJjjC by slowly increasing the temperature (60°C/hour) in the furnace. As the temperature reached approximately 400ij|C, the rayon component of the fiber burned off as carbon dioxide (C02) and water. In the second stage, the now inorganic fiber was heated to 1080°C with Argon gas being fed into the furnace, and when the temperature reached 1100°C, hydrogen was fed to the furnace and the heating rate was increased to 85°C/hour until the furnace temperature was 1200°C. After remaining at 1200°C for approximately one hour to sinter the ceramic particles, in the third stage, the fibers were cooled at the rate of 100°C/hour until the temperature reached approximately 1000°C, and thereafter cooled more gradually at the rate of 60°C/hour until they returned to ambient temperature. Visual inspection revealed distinct fibers which retained their individual character in mild handling. Fiber length after firing was approximately 3 inches, the diameter was approximately 15 mm and the strength appeared to be approximately 138 Mpa as measured by the bending test method. Reduction in hydrogen at 1200°C for one hour created conductivity through the presence of both the sub-oxide cupric oxide and the sub-oxide titania, as described in U.S. Patent No. 4,931,213. These fibers are useful as conductors in alkaline and solid state batteries, and structural supports to permit building large ceramic electrodes for use in chrome plating, magnesium recovery from seawater, electro-winning, and electro-chlorination. Example IA Production of a conductive titanium oxide ceramic fiber 2.7 grams of cupric chloride intercalated graphite was added to 77.3 grams of Ti02 from Diamond Metals, Japan, with a mean particle size of approximately 0.5 micrometers to introduce 0.72% cupric chloride into the structure of the titania after heat processing. The graphite was burned out at 800°C for 2 hrs. . 160.0 grams of this modified titanium dioxide powder was added slowly to the vortex of a solution, stirred in a beaker on a magnetic stirrer, of 2.4 grams of a 30% aqueous solution of sodium polymethacrylate of an average molecular weight of about 10,000 (Colloid™ 225 from Rhone-Poulenc Surfactants and Specialties), 2.4 grams of a 90% powder of sodium methyl-naphthalene formaldehyde sulfonate (Supragil™ MNS/90 from Rhone-Poulenc Surfactants and Specialties), 1.6 grams of l-amino-2-propanol and 3.2 grams of polyethylene glycol of an average molecular weight of approximately 1300 to 1600 (Carbowax^* PEG 1450 from Union Carbide Corporation) plus 150.4 grams of water, deionized by passing through an ion exchange resin. The Colloid™ 225 and Supragil MNS/90 served as dispersants for the modified titanium dioxide. The aminopropanol and PEG 1450 may have also acted as dispersants, but it is believed that they acted as viscose modifiers to allow higher stretch and consequently higher fiber strength, as is common for amines and polyglycols. After all the modified titanium dioxide was added to the aqueous solution, the thick dispersion was stirred by hand to give a less thick pasty dispersion. This dispersion was added to a porcelain milling jar having a capacity of approximately one liter of water containing approximately 35 alumina balls having various diameters ranging from 0.5 to 2.5 inches. The jar was then sealed with a cap and a clamp. This combination was ball milled overnight for approximately 18 hours to reduce/eliminate agglomerates. The dispersion was then thin and uniform. Then, 5.0 grams of IN NaOH solution was added to 143.1 grams of this dispersion and mixed well. The purpose of the additional sodium hydroxide was to provide sufficient alkalinity to the dispersion to prevent "shock" or polymer precipitation upon mixing with the highly alkaline viscose. To this mixture was added 189.3 grams of "viscose", or a solution of sodium cellulose xanthate, or cellulose sodium dithiocarbonate in aqueous sodium hydroxide. This particular viscose solution contained approximately 9.45% by weight of cellulose with a DP of approximately 400. Therefore, the weight ratio of modified titanium dioxide to cellulose was approximately 83.5:16.5. The particular viscose used was a commercial viscose with a starting composition by weight of 9.45% cellulose and 6.10% NaOH based on the aqueous solution and 32 wt. per cent carbon disulfide based on cellulose (boc) . This viscose had been aged by conventional procedures to a salt index (sodium chloride coagulation) of approximately 4 to 5. The ceramic dispersion - viscose mixture, or spin mix, was stirred vigorously by hand with a wide plastic spatula after each addition of four increments of the viscose to the inorganic dispersion. The final mixture was then stirred vigorously by hand with the same spatula for approximately 15 minutes at ambient temperature. The stirred mixture then was filtered through a 25-40 mm cloth under <10 psi air pressure, transferred to a plastic bottle and then placed in the freezer of a refrigerator to be stored frozen overnight. The next day, after approximately 18 hours in the freezer, the container of spin mix was returned to ambient temperature for thawing. After thawing for two to three hours, the spin mix was deaired in a glass desiccator, containing no desiccant, connected to a vacuum pump at approximately 24 inches of mercury until there were no visible signs of air. The deaired ceramic/viscose mixture was then spun at a rate of approximately 16 grams per minute by conventional viscose rayon techniques (same reference) through a spinneret containing 100 round, conventional rayon holes of 88.9 μm diameter into a spinbath of approximately 7.5 %(wt.) sulfuric acid, 22.0 % (wt.) sodium sulfate and 1.5% (wt.) zinc sulfate in deionized water at approximately 45° C , through a second bath of approximately 2.5 % (wt.) sulfuric acid in deionized water at approximately 95°C and wound onto a winding tube. The organic/inorganic fibers were purified and converted into inorganic fibers as in Example 1.

The deaired ceramic/viscose mixture was added to a stainless steel conical container connected by directly to a Zenith^* gear pump. The pump was connected to a plastic tube with a flanged ferrule on the end. Attached to this ferrule was a plastic assembly holding a viscose rayon spinneret containing 100 round holes of 89 mm diameter. The spin mix was pumped at a rate of approximately 16 grams a minute into a spinbath composed of approximately 7.5% by weight of sulfuric acid (H2S04) , approximately 22.0% by weight of sodium sulfate (Na2S04) and approximately 1.5% by weight of zinc sulfate (ZnS04) , with the remainder being deionized water at approximately 45 degrees Celsius. The filaments were collected at the end of the bath, which was approximately 30 cm. in length and held approximately 1900 grams of the above spinbath solution, and passed around a godet at 40 RPM (linear speed of 6.1 m/min.), into a hot bath containing approximately 2.5% by weight H2S04 at approximately 95°C, over a second godet at 66RPM (a linear speed of 10 m/min.) to give a godet stretch of approximately 65%. The filaments were then wound onto a paper tube purified, removed from the paper tube and converted into inorganic fibers by heating to at a rate of 60°C per hour. At 1080°C argon was introduced, followed by hydrogen at 1100°C. The heating rate was then increased to 85°C per hour (remped § 85°C per hr. and held at 1230°C for 2.5 hrs. (2.5 hr. soak), then cooled at the rate of 100°C per hr. to ambient temperature. The fiber had a resistivity of 0.53 Ω cm.

Example 1B-1 Production of a conductive titanium oxide ceramic fiber Example IA was repeated except that no Supragil MNS/90 and Carbowax PEG 1450 were added and 2.4 grams of l-amino-2- propanol were added along with 2.4 grams of Colloid™ 225 and 75.2 grams of deionized water with 80.0 grams of modified titanium dioxide. The viscose had a sodium chloride salt index of approximately 7.5. The spin mix was not frozen but was spun in about 4 hours on the same day it was mixed. The zinc sulfate in the spin bath was approximately 2.5 wt. %, the spinbath temperature was approximately 43 degrees Celsius and the sulfuric acid in the hot second bath was approximately 2.0 wt. %. The maximum godet stretch obtained was about 62.5%, corresponding to a second godet speed of 65 RPM. The filaments were then wound, purified, and converted into inorganic fibers by the same procedure as in Example IA.

Example 1B-2 Production of a conductive titanium oxide ceramic fiber When the same spin mix was spun into a spinbath of approximately 7.0 wt.% H2S04, 22.0 wt. % Na2S04 and 1.5 wt. % ZnS04 at approximately 45 degrees C. , the maximum stretch obtainable was approximately 47.5%, corresponding to a second godet speed of approximately 59 RPM. The filaments were then wound, purified, and converted into inorganic fibers by the same procedure as in Example IA.

Example 1B-3 Production of a conductive titanium oxide ceramic fiber A change of the spinbath composition to approximately 7.55 wt.% H2S04, 22.85 wt. % Na2S04 and 1.5 wt. % ZnS04 and a hot second bath of approximately 2.5 wt.% H2S04 gave poor spinning with a maximum stretch of only about 32.5%, corresponding to a second godet speed of approximately 53 RPM.

Example lC-1 Production of a conductive titanium oxide ceramic fiber Example IA was repeated except that the modified titanium dioxide was made by adding 5.25 parts of cupric chloride intercalated graphite was added to 50 parts of a mixture of 75% by weight of Ti0₂ from Diamond Metals, Japan, with a mean particle size of approximately 0.5 micrometers and 25% by weight of Heavy Grade Ti02 from TAM Ceramics Inc. having an average particle size of 2-3 micrometers and mixed in a V-blender for 2 hours to introduce 2.16% cupric chloride into the structure of the titania after heat processing. The graphite was burned out at 800°C for 2 hours. 100 grams of this higher copper mixed particle size powder was added to a solution of 1.5 grams of Colloid™ 225, 1.5 grams of Supragil™ MNS/90, 1.0 g l-amino-2-propanol and 2.0 g Carbowax^* PEG 1450 in 94.0 grams of deionized water. This dispersion was milled over a week end (Friday to Monday) and then mixed with a viscose containing approximately 7.75 % by weight cellulose and approximately 5.69% by weight sodium hydroxide at a sodium chloride salt index of approximately 5 to 6. The modified titanium dioxide dispersion was mixed with the viscose so as to give a spin mix of approximately 83.5 to 16.5 weight ratio of modified titanium dioxide to cellulose. The spin mix was frozen over night, thawed and spun as in Example 1 into a spinbath of approximately 7.0 wt.% H2S04, 22.0 wt. % Na2S04 and 1.5 wt. % ZnS04 at approximately 45 degrees C. The maximum stretch obtainable was approximately 47.5%, corresponding to a second godet speed of approximately 59 RPM.

Example 1C-2 Production of a conductive titanium oxide ceramic fiber A change of the spinbath composition to approximately 7.3 wt.% H2S04, 20.6 wt. % Na2S04 and 3.3 wt. % ZnS04 produced a maximum stretch of approximately 57.5%, corresponding to a second godet speed of approximately 63 RPM.

Example 1D-1 Production of a conductive titanium oxide ceramic fiber Example 1 was repeated except that 100 grams of the modified titanium dioxide as in Example 1-C-l was added to a solution of 1.5 grams of Colloid™ 225, 1.5 grams of Supragil MNS/90 in 97.0 grams of deionized water. This dispersion was milled over night and then mixed with an industrial yarn viscose containing approximately 7.35 % by weight cellulose and approximately 5.60 % by weight sodium hydroxide and containing amine, ethoxylated amine and polyethylene oxide modifiers at a total concentration of less than 2.5% based on the weight of the cellulose. This dispersion was milled over night. After adding 2 drops of IN NaOH to the modified titanium dioxide dispersion, it was mixed with the viscose so as to give a spin mix of approximately 80 to 20 weight ratio of modified titanium dioxide to cellulose. The spin mix was frozen overnight for approximately 20 hours, thawed at ambient temperature and spun as in Example 1 but at a rate of 8 g/min. into a spinbath of approximately 4.0 wt.% H₂S0₄, 13.5 wt. % Na₂S0₄ and 4.25 wt.% ZnS0₄ at approximately 35 degrees C and a second bath of approximately 2% H₂S0₄ at a temperature of approximately 95 degrees C. The maximum stretch obtainable was approximately 102.5%, corresponding to a first godet speed of approximately 40 RPM and a second godet speed of approximately 81 RPM. The filaments were then wound onto a paper tube, purified, removed from the tube and converted into inorganic fibers as in Example 1.

Example 1D-2 Production of a conductive titanium oxide ceramic fiber Example 1D-1 was repeated except that 75 grams of the modified titanium dioxide was added to a solution of 0.75 grams of Colloid™ 225, 0.75 grams of Supragil MNS/90, 0.75 grams of l-amino-2-propanol and 1.5 grams of Carbowax PEG 1450 in 71.5 grams of deionized ,ater. This dispersion was milled over night and then mixed with the same industrial yarn viscose as in Example 1D-1 in the same manner and the same ratios. The spin mix frozen for six days, thawed and spun as in Example 1D-1 but at a first godet speed of 21 RPM into a spinbath of approximately 4.5 wt.% H₂S0₄, 13.5 wt. % Na₂S0₄ and 4.25 wt. % ZnS0₄ at approximately 36 degrees C and a second bath of approximately 2% H₂S0₄ at a temperature of approximately 95 degrees C. The maximum stretch obtainable was approximately 128%, a second godet speed of approximately 41 RPM. The filaments were then wound onto a paper tube, purified, removed from the tube and converted into inorganic fibers as in Example 1. Example 2 Production of a second conductive titanium oxide ceramic fiber Following the procedure of Example 1, 0.75 grams of tin oxide (Sn02) powder was used to introduce 1.5% by weight of tin oxide into 50 grams of Ti0₂ (same as in Example 1) . 33% by weight of water was added, and the mixture then mixed in a ball mill for twenty hours. After mixing, the powder was oven dried, calcined in air at 1400°C, reground, and returned to the process of Example 1 at the point of adding water containing 3 wt.% of D,L-l-amino-2-propanol dispersant Aldrich Chemical, catalog # 11,024-8 dispersant to create a dispersion of ceramic powder in water for ball milling to eliminate or reduce agglomerates. The remaining procedures were identical to those described in Example 1, and the fibers produced and test results were comparable. These fibers are useful as current path enhancers in both the plates and paste of lead acid batteries.

Example 3 Production of a third conductive titanium oxide ceramic fiber Following the procedure of Example 2, 1.6 grams of niobium oxide were added to 50 grams of Ti02 (from Diamond Metals, Japan, with a mean particle size of approximately 0.5 micrometers) . The powders were mixed dry for 2 hours in a V-blender and then calcined in air for two hours at 15 0°C, to create a slight oxygen deficiency (from stoichiometric) , reground and returned to the process of Example 1 at the point of adding water containing 3% by weight of and about 2 ml of Triton^* X-100 surfactant from Union Carbide Corporation to create a dispersion of ceramic powder in water for ball milling so as to eliminate/reduce agglomerates. Five drops of tri-butyl-phosphate were added to reduce foaming. Spinnerette size and firing parameters varied from Examples 1 and 2 as specified below, but, other than as specified below, the remainder of the procedures were identical to those described in Examples 1 and 2. The spinnerette contained 100 holes of 89 M5μm diameter each, which produced ceramic/cellulose mixture fibers mm in diameter and sintered fibers μm in diameter. Conductivity was created by reduction while sintering for one hour in hydrogen at 1215°C. These fibers are useful as structural supports to permit building large ceramic electrodes for use in high temperature applications like aluminum and magnesium refining and magneto-hydro-dynamic (MHD) power generation.

Example 4 Production of a lithium aluminate ceramic fiber 80 grams of deionized water were added to 50 grams of a mixture of 90% by weight of LiA102 (obtained from Aldrich Chemical, having a mean particle size of approximately one micrometer and) 10% of LiA102 (obtained from a confidential source) which comprised particles of submicron size. The combination was then ball milled for sixteen hours to further reduce particle size and reduce/eliminate agglomerates. Approximately one milliliter of caustic soda (NaOH) was (pipetted) into the milled mixture to raise the pH into the 11.0 to 12.0 range. To the suspension was added approximately 116 cubic centimeters (132 grams) of viscose containing 9.45% by weight of cellulose. This mixture was treated, through the deaeration step, according to the procedures described in Example 1. The stirred mixture then was filtered through 25-40 mm cloth under <10 psi air pressure, and then stored for two hours at 18l|:C. The ceramic/viscose mixture then was fed into a spinning machine through an enclosed and air pressured chamber using a constant pressure, variable volume "Zenith" metering pump. The pump forced the precursor through a spinnerette containing 100 round, straight sided holes of 89 μm diameter into a 43J|iC coagulation bath. The bath was flowing gently countercurrent to the discharging precursor, and was composed of 7.5% by weight of sulfuric acid (H2S04) , and 22.0% by weight of sodium sulfate (Na2S04) , with the remainder being deionized water. The viscose portion of the precursor precipitated and reacted with the spinbath to produce fibers of approximately 20% by weight of rayon and approximately 80% by weight of ceramic with approximately. Precursor was fed into the spin bath at a rate of approximately 16.0 grams per minute and the spun fiber was drawn away from the spinnerette face by a take-up godet operating at a linear speed of approximately 6.0 meters per minute. The fibers were pulled from the first take-up godet by a second, faster paced godet, operating at a linear speed of approximately 7.0 meters per minute, thus applying a 17.5% extension to the fiber to align both the cellulose molecules and the ceramic particles along the longitudinal axis of the fiber. In their passage from first to second godet, the fibers were immersed in a boiling, deionized water bath containing a small amount, <1% by weight of H2S04. This bath continued the regeneration started in the spinbath and began a cleansing/washing process. The fibers were wound continuously onto a take up reel moving at the same linear speed as the second godet. The fibers were cut to lengths of about 6 inches and cleaned of sulfuric acid residue by dipping consecutively into two clean 95JIJC water baths for approximately two minutes each, and allowed to dry for approximately 24 hours. The dried fibers were sintered in air in a tube furnace. First, the fibers were pushed to the edge of the first heater in the furnace, where the temperature was approximately 400:IJC, where they remained for about five minutes until the rayon in the fiber burned off as carbon dioxide (C02) and water. Second, the fibers were pushed to the center of the heating zones of the furnace, where the temperature was about 1500lj:C, and allowed to remain for five minutes to sinter the ceramic particles. Third, the furnace temperature was then reduced to 90θljjC for one hour to return the ceramic fibers to the LiA102 gamma phase. Fourth, the fiber was pushed out of the hot zone into an area where the temperature was approximately 25θijjC and allowed to cool gradually over another five minute period, Finally, the fibers were removed and allowed to cool gradually to ambient temperature. Visual and microscopic inspection revealed distinct fibers which retained their individual character in mild handling. After firing, fiber length was broken to approximately 1/8 inch and the diameter was approximately 15 mm. These fibers are useful in carbonate based fuel cells.

Example 5 Production of a superconducting 1-2-3 YBCO ceramic fiber A 50 gram batch of 95% (by weight) YBa2Cu307/5% (by weight) Y2BaCu05 was prepared by mixing and firing in air for sixteen hours at 82θij:C, reground and refired in air at 920°C for ten hours. The powder was then melt texture growth processed at 1210°C for 5 minutes and then rapidly cooled naturally to 1010°C in air and then slow cooled at 5°C/hour in air to ambient temperature. The particles were reground and magnetically classified under cryogenic conditions (in liquid nitrogen) to select only the superconducting, high purity components of the powder, and finally ground to 5 mm diameter in a mortar and pestle. (The phase pure particles thus produced were found to be non-reactive with water.) 20tgrams of deionized water were added to 20 grams of the reground, phase pure YBCO and the combination mixed at a controlled temperature of lojjic for approximately thirty minutes. To the suspension was added approximately 175 cubic centimeters (200 grams) of viscose, containing 9.45% cellulose. This mixture was stirred for one hour in a temperature controlled environment at approximately 3°C to minimize addition of energy to the chemically unstable viscose. Mixer speed deliberately was kept low to avoid excessive agitation and addition of excess air. The stirred mixture then was filtered through 25-40 mm cloth under <10 psi air pressure. (During the filtration step, the mixture gelled, producing an unfilterable and unspinnable material.)

YBCO fibers can be used in wires, cables, sensors, electronic devices, coils, and connectors in cryogenic electrical apparatus applications.]

Example 5A (prophetic) Production of a superconducting 1-2-3 YBCO ceramic fiber YBa2Cu307 was fired in air for approximately fifteen hours at 960'C, cooled and refired in air at 920"C for approximately two hours then heated to 1170'C as rapidly as possible and held at this temperature for 15 to 20 minutes and then cooled at a rate of 10'C per minute to approximately 1020"C and then slow cooled at 1- 2'C/hour in air to 960^*C, then cooled at a rate of 10'C per hour to approximately 880^*C, then cooled at a rate of 6'C per hour to approximately 400'C and finally cooled at a rate of approximately 20'C per hour to ambient temperature. The particles were ground to 5 mm diameter and magnetically classified under cryogenic conditions (in liquid nitrogen) to select only the superconducting, high purity components of the powder, and finally ground to 2 mm diameter in a mortar and pestle and again magnetically classified under cryogenic conditions (in liquid nitrogen) to select only the superconducting, high purity components of the powder. The powder was then jet pulverized to particles of average diameter of 1-2 μm. This jet pulverized powder is added to a solution of 5.0 parts of the reaction product of 30 moles of ethylene oxide with castor oil (Alkamuls^* EL-620 from Rhόne-Poulenc Surfactants and Specialties), 5.0 parts of the reaction product of propylene oxide and ethylene oxide with p-phenyl phenol (Antarox^* WA-1 from Rhone-Poulenc Surfactants and Specialties), 1.0 parts of a 75% solution of sodium dioctyl sulfosuccinate (Geropon™ SS-O-75 from Rhόne-Poulenc Surfactants and Specialties) and 1.0 parts sodium hydroxide in 88.0 parts deionized water and agitated to form a suspension. This suspension is immediately pumped by metering pump into a stream of deaired viscose as in Example IA, pumped by a Zenith® pump as in Example IA, both flows metered so as to give a weight ratio of 80 parts of the superconductive powder to 20 parts of cellulose. The mixture immediately goes through an in-line static tube or pipe mixer to form a homogeneous spin mix and then through a spinneret and through other viscose rayon processing as in Example 5. The resulting fiber is then sintered in air by heating at a rate of 100°C/hr. to 960°C , holding at this temperature for 5 minutes and then cooling at a rate of 25°C/hr. to 900°C. Oxygen is then added at a rate of 10 cubic feet per minute and the cooling is continued at a rate of 25°C/hr. to 800°C. The fiber is then annealed by changing the cooling rate to 4°C/hr. to 400°C and then to 25°C/hr. to 200°C and then to 100°C/hr. to ambient temperature. Example 5B (prophetic) Production of a superconducting 1-2-3 YBCO ceramic fiber Example 5A is repeated except that the deaerated viscose is metered into the stream of the superconductor dispersion.

Example 5C (Prophetic) Production of a superconducting 1-2-3 YBCO ceramic fiber Example 5A is repeated except that Isoton^* II, a solution of 0.793% sodium chloride, 0.038% disodium EDTA (ethylenediaminetetraacetic acid), 0.040% potassium chloride, 0.019% sodium dihydrogen phosphate, 0.195% disodium phosphate and 0.030% sodium fluoride, all by weight in distilled water from Coulter Corporation is used in place of deionized water.

Example 5D (Prophetic) Production of a superconducting 1-2-3 YBCO ceramic fiber Example 5A is repeated except that a 5% sodium chloride on the weight of the superconductor is added to the distilled water - dispersant combination.

Example 5E (Prophetic) Production of a superconducting 1-2-3 YBCO ceramic fiber Example 5D is repeated except that sodium chloride is replaced by sodium sulfate.

Example 5E1 5.0 grams of the powder from Example 5A was added to 5.0 grams of deionized water and dispersed with agitation. 13.2 grams of viscose as in Example IA was added to this dispersion and mixed by hand with a spatula. The mixture gelled before it could be mixed completely. Example 5E2 Example 5E1 was repeated except that the superconductor was added to a solution composed of 4.41 grams of deionized water, 0.1 grams of Alkamuls EL-620, 0.1 grams of Antarox WA- 1, 0.15 grams of Geropon SS-O-75, and 0.24 grams of the components of Isoton II solution as described in Example 5C. The mixture with viscose was fluid without gelation at ambient temperature for approximately 58 minutes.

Example 5E3 Example 5E2 was repeated except that the superconductor was added to a solution composed of 4.275 grams of deionized water, 0.1 grams of Alkamuls EL-620, 0.1 grams of Antarox WA-1, 0.15 grams of Geropon SS-0-75, and 0.125 grams of NaCl. The mixture with viscose was fluid without gelation at ambient temperature for approximately 92 minutes.

Example 5E4 Example 5E3 was repeated except that the supercondutor wasadded to a solution composed of 3.93grams of deionizedwater, 0.1 grams of Alkamuls EL-620, 0.1 grams, of AntaroxWA-1, 0.15 grams of Geropon SS-0-75, and 0.72 grams ofCheelox 354, which is a 36% aqueous solution of sodiumglucoheptonate from Rhόne-Poulenc Surfactants andSpecialties. The mixture with viscose was fluid withoutgelation at ambient temperature for approximately 77 minutes.

Example 5E5 Example 5E3 was repeated except that the superconductor wasadded to a solution composed of 4.41 grams of deionizedwater, 0.1 grams of Alkamuls EL-620, 0.1 grams of AntaroxWA-1, 0.15 grams of Geropon SS-0-75, and 0.24 grams ofsodiu borate hydrate (Na₂B₄O₇*10H₂O) . The mixture withviscose was fluid without gelation at ambient temperaturefor approximately 72 minutes.

Example 5E6 50.0 grams of the powder from Example 5A was added to asolution composed of 44.1 grams of deionized water, l.Ograms of Alkamuls EL-620, 1.0 grams of Antarox WA-1, 1.5grams of Geropon SS-0-75, and 2.4 grams of NaCl. 132.3grams of viscose as in Example IA was added to thisdispersion and mixed by hand with a spatula. The fluidmixture was deareated under vacuum for 5 to 10 minutes. Themixture was fluid for approximately two hours or longer atambient temperature.

Example 5N-l (T1130A, 12/1/95) Production of a superconducting 1-2-3 YBCO ceramic fiber 75 grams of a mixture by weight of 15.1% yttrium oxide (Y₂0₃) , 52.9% barium carbonate (Ba(C0₃)₂) and 32.0% cupric oxide (CuO) , mixed by first blending the proper amounts of Y₂0₃ and CuO in a V-blender for 1 hr., adding the Ba(C0₃)₂ and blending for an additional two hours, was added to a solution of 4.5 grams of a 25 wt. % of the sodium salt of an acrylic copolymer (Colloid™ 111 from Rhόne-Poulenc Surfactants and Specialties) and 61.5 grams of deionized water as in Example IA and milled overnight as in Example IA. After adding 5.0 grams of IN NaOH and 4.0 grams of deionized water to the dispersion, it was mixed with a viscose of the same composition and in the same manner, deaired and spun into fiber in the same manner as in Example IA. The spinbath composition was by weight 7.5% H2S04, 22.0% Na2S04, and 2.5% ZnS04 at a temperature of about 45 degrees Celsius and a hot second bath of approximately 2.0% H2S04. A small amount of fiber was obtained to be converted to a superconductive fiber.

Example 5N-2 (T1130A, 12/1/95) Production of a superconducting 1-2-3 YBCO ceramic fiber Example 5M-2 was repeated except the spinneret used was a single hole assembly of approximately 3 mm diameter. The spin mix was fed by gravity to the spinneret and into the spinbath. About 4 feet of the monofilament was obtained to be converted to a superconductive fiber.

Example 50 Coating of a superconductor 1-2-3 YBCO powder The superconducting powder from Example 5A was coated with by suspending 25.0 grams of the powder in a mixture of 40.0 grams of a 15 weight per cent nonaqueous dispersion of polypropylene containing pendant carboxylic acid groups in a hydrotreated light petroleum distillates solvent and 1.6 grams of Eastman PA-6 plasticizer. The uniform suspension was left in an open beaker for two days and then poured onto a watch glass on a hot plate to evaporate the high boiling solvent at approximatly 150 degrees C and to form a film around the superconductor particles. 15 grams of this dry coated powder was added to 15 grams of deionized water containing 0.6 grams Geropon SS-0-75, 0.4 grams of Alkamuls EL-620 nd 0.4 grams of Antarox WA-1 dispersants and milled with 24 zirconia media in a small plastic jar for 40 minutes. Addition of 10.0 grams of deionized water to the thick grease that resulted gave a good fluid dispersion. 20.5 grams of viscose as in Example 5E1 was added to 31.0 grams of this dispersion and mixed by hand with a spatula to give a fluid mixture which was fluid for over one hour and still fluid after freezing overnight and thawing. This spin mix can be converted into a superconductive fiber by the procedure of Example IA or 5A or B. Example 5P Coating of a superconducting 1-2-3 YBCO powder The superconductor precursor powder from Example 5N-lwas converted to YBCO superconductor by a three stepheating process in which the first step was 860 degrees Cfor 30 hours, the second step was 900 degrees for 15 hoursand the third step was two parts of 920 degrees C for 15hours and then 950 degrees C for 15 hours. Thissuperconductor powder was seived to approximately 41micrometers particle size and then coated micrometers particle size and then coated by suspending 10.0 grams of the powder in a mixture of 4.7 grams of a 15 weight per cent nonaqueous dispersion of polypropylene containing pendant carboxylic acid groups in a hydrotreatedlight petroleum distillates solvent, 0.4 grams of EastmanPA-6 plasticizer and 5.0 grams of toluene. The uniformsuspension was rapidly heated left in an open crystallizingdish on a hot plate to approximately 150 to 160 degrees Cto evaporate the solvent and to form a film around thesuperconductor particles. 5.0 grams of this dry coatedpowder was added to 5.0 grams of deionized water containingθ.3 grams Geropon SS-0-75, 0.2 grams of Alkamuls EL-620 andθ.2 grams of Antarox WA-1 dispersants and dispersed withhand agitation. 13.2 grams of viscose as in Example 5Elwas added to this dispersion and mixed by hand with aspatula to give a mix which was fluid for over one hour.This spin mix can be converted by the procedure of Example IA or 5A or B.

Example 50 Example 5P was repeated except the superconductorpowder used in Example 5A was used and only 2.0 grams oftoluene was added to the coating dispersion. Essentiallythe same results were obtained.

Example 5R Example 5P was repeated except that 0.3 grams ofAlkamuls EL-620 and only 2.0 grams of toluene were added tothe coating dispersion. Essentially the same results wereobtained. Example 6 Production of a lead-zirconia-titanate (PZT) ceramic fiber 45 grams of deionized water containing 2 ml of Triton X-100 surfactant were added to 45 grams of lead-zirconia-titanate (PZT) powder. To the mixture was added approximately 41 cubic centimeters (47 grams) of viscose, containing 9.45% by weight of cellulose. This mixture was stirred for one-half hour with a high shear mixer to mix the components, to break up agglomerates and to further eliminate agglomerates. The stirred mixture then was filtered through 25-40 mm cloth under <10 psi air pressure, and the mixture was then stored for one hour at 10°C to deaerate, and allowed to equilibrate at 18°C for 30 minutes prior to spinning. The ceramic/viscose mixture then was fed into a spinning machine through a constant pressure, variable volume "Zenith" metering pump. The pump forced the precursor through a viscose rayon spinnerette containing 350 round, holes of 64 μm diameter into a 53°C spinbath, flowing gently countercurrent to the direction as the discharging precursor, and composed of 7.5% by weight of sulfuric acid (H₂S0₄) , and 22.0% by weight of sodium sulfate (Na₂S0₄) , with the remainder being deionized water. The viscose portion of the precursor precipitated the mixture into fibers and reacted with the acid in the spinbath and to give fibers of 10% by weight of rayon and 90% by weight of ceramic having diameters of approximately 35 μm. Precursor was fed into the spin bath at a rate of approximately 20.0 grams per minute and the spun fiber drawn away from the spinnerette face by a take-up godet operating at a linear speed of approximately 6.2 meters per minute. The fibers were pulled from the first take-up godet by a second, faster paced godet, operating at a linear speed of approximately 7.0 meters per minute, which applied a 12.9% extension to the fiber to align both the cellulose molecules and the ceramic particles along the longitudinal axis of the fiber. In its passage from first to second godet, the fiber was immersed in a boiling deionized water bath containing a low concentration (<1% by weight) of H2S04. This bath continued the regeneration reaction started in the coagulating bath and began the cleansing/washing process. The fibers were wound continuously on a take up reel moving at the same linear speed as the second godet. The fibers were removed from the take up reel in a continuous >50 meter length and then cleaned of sulfuric acid residue by dipping the fibers consecutively into at least two clean 95li|C water baths for two minutes each. The fibers were then allowed to air dry for approximately 24 hours. Visual and microscopic inspection revealed distinct fibers which retained their individual character in mild handling. The fibers retained continuous form. Fiber diameter was approximately 45 mm, and strength appeared to be approximately 140 Mpa as measured by the bending test method. PZT fibers are useful in sensing and actuating applications such as vibration damping, noise reduction, etc.

Example 6A Production of a lead-zirconia-titanate (PZT) ceramic fiber 100 grams of lead-zirconia-titanate (Pb,Zr,Ti03) (PZT)powder, burned out at 500°C, was added to 100 grams of deionized water and milled overnight as in Example IA. The next day, this PZT dispersion was mixed with viscose and spun into fiber as in Example IA. The maximum stretch obtained through a 3% H2S04 second bath at a temperature of approximately 95°C was 37% at 53RPM. The continuous filament fiber was then washed through a large crystallizing dish containing deionized water at approximately 95°||C and then dried at ambient temperature for two hours.

Example 7 Production of a molybdenum di-silicide ceramic fiber 40 grams of MoSi2 powder were ball milled for 16 hours in 40 grams of deionized water containing 3% by weight of 2- amino-1-propanol to reduce particle size, and then pipetted with about 1 ml of 1.0 N NaOH to a pH of 11-12. To this mixture was added approximately 90 cubic centimeters (106 grams) of viscose containing 9.45% by weight of cellulose. This mixture was stirred for twenty minutes under high shear to further eliminate agglomerates. The stirred mixture then was filtered through 25-40 μm cloth under <10 psi air pressure, deaerated and then equilibrated at 18jjic as described in Example 6. The ceramic/viscose mixture was fed into a spinning machine through a constant pressure, variable volume "Zenith®" metering pump. The pump forced the precursor through a spinnerette containing 350 round, holes of 64 μm diameter into a 47ij:C coagulation bath, flowing gently in the same direction as the discharging precursor, composed of 7.5% by weight of sulfuric acid (H2S04) , and 22.0% by weight of sodium sulfate (Na2S04) , with the remainder being deionized water. The viscose portion of the precursor reacted with the coagulating bath acid and precipitated the mixture into fibers of 20% by weight of rayon and 80% by weight of ceramic having approximately 40 mm diameters. Precursor was fed into the spin bath at a rate of approximately 21.0 grams per minute and the spun fiber drawn away from the spinnerette face by a take-up godet operating at a linear speed of approximately 6.1 meters per minute. The fibers were pulled from the first take-up godet by a second, faster paced godet, operating at a linear speed of approximately 7.5 meters per minute, which applied a 22.9% extension to the fiber to align both the cellulose molecules and the ceramic particles along the longitudinal axis of the fiber. In its passage from first to second godet, the fiber was immersed in a boiling water bath containing H2S04 in a concentration of <1% by weight. This bath continued the regeneration started in the coagulating bath and began a cleansing/washing process. The fibers were wound continuously on a take up reel moving at the same linear speed as the second godet. The fibers were cleaned of any sulfuric acid residue by dipping the fibers, still on the take up reel, into two consecutive clean water 95°C baths for two minutes each. The fibers were removed continuously from the take up reel and air dried for approximately 24 hours. The continuous, dried fibers were sintered in an atmospherically controlled furnace in two distinct stages. First, the fibers were prefired in argon at 800°C to drive off the rayon. Then the temperature gradually was raised (100°C/hour) to 1800°C and the fiber allowed to remain at that temperature for one minute. Thereafter, the furnace was naturally cooled to ambient temperature in argon and the fibers removed. Visual and microscopic inspection revealed distinct fibers which retained their individual character in mild handling. Continuous length was retained after firing with individual fiber diameter of approximately 11 mm. Molybdenum disilicide fibers are useful as high temperature conductors and reinforcements.

Example 8 Production of a fourth conductive titanium oxide ceramic fiber Following the procedure of Example 7, 30 grams of titania, reduced in hydrogen to Ti407, were reground to approximately 10 mm particle size, and mixed with 30 grams of deionized water and titrated with 1.0 N NaOH to a pH of 11-12. To the mixture was added approximately 71.5 cubic centimeters (80 grams) of viscose, containing 9.45% by weight of cellulose. This mixture was stirred for ten minutes with mixing speed deliberately low to avoid excessive agitation and addition of excess air. The stirred mixture then was filtered through 25-40 mm cloth under <10 psi air pressure. The filtered mixture was then deaerated and equilibrated at 18lj|C as described in Example 6. The ceramic/viscose mixture was fed into a spinning machine through a constant pressure, variable volume "Zenith" metering pump. The pump forced the precursor through a spinnerette containing 100 round, holes of 89 μm diameter into a 45i!iC coagulation bath, flowing gently in the same direction as the discharging precursor, and composed of 8.0% by weight of sulfuric acid (H2S04) , and 22.0% by weight of sodium sulfate (Na2S04) , with the remainder being deionized water. The viscose portion of the precursor reacted with the coagulating bath acid and precipitated the mixture into fibers of 50% by weight of rayon and 50% by weight of ceramic with approximately 60 mm diameter. Precursor was fed into the spin bath at a rate of approximately 15.0 grams per minute and the spun fiber drawn away from the spinnerette face by a take-up godet operating at a linear speed of approximately 6.0 meters per minute. The fibers were pulled from the first take-up godet by a second, faster paced godet, operating at a linear speed of approximately 7.0 meters per minute, which applied a 12.9% extension to the fiber to align both the cellulose molecules and the ceramic particles along the longitudinal axis of the fiber. In its passage from first to second godet, the fiber was immersed in a near boiling deionized water bath. This bath completed the precipitation reaction (continued the regeneration) started in the coagulating bath and began the cleansing/washing process. The fibers were wound continuously onto a take up reel moving at the same linear speed as the second godet. The fibers were cleaned of sulfuric acid residue by dipping the fibers, still on the take up reel, consecutively into two clean 95°C water baths for two minutes each. The fibers were removed from the take up reel in a continuous >50 meter length and allowed to air dry for approximately 24 hours. The continuous, dried fibers were slowly heated in air in a furnace to a temperature of about 28θ||!c and maintained at that temperature for about thirty minutes until the rayon in the fiber burned off as carbon dioxide (C02) and water. Then the temperature was again increased. At about 300°C, the furnace air was evacuated and hydrogen introduced into the furnace, while the heating continued to slowly increase the temperature to 1175°C. That temperature was maintained for 30 minutes to sinter the reduced ceramic particles. Then, the fibers were cooled gradually to ambient temperature, maintaining the hydrogen atmosphere until the temperature was reduced to below 300°C. Visual and microscopic inspection revealed distinct fibers which retained their individual character in mild handling. After firing, the fiber retained continuous form, fiber diameter was approximately 10 mm, and strength appears to be approximately 180 Mpa as measured by the bending test method. These fibers are useful as conductors in alkaline and solid state batteries, electromagnetic shielding and absorption, and structural supports to permit building large ceramic electrodes for use in chrome plating, magnesium recovery from seawater, electro-winning, electro-chlorination and any other electrochemical process.

Example 9 Production of a conductive tin/ antimony oxide ceramic fiber 80.0 grams of a mixture of approximately 90:10 by weight of stannic oxide (Sn02) and antimony oxide (Sb203) (Stanostat CP15G from Magnesium Elektron Industries) added to 80.0 grams of deionized water and milled overnight in a plastic jar. The next day, the very thick dispersion was thinned by adding 2 ml of sodium silicate solution (Aldrich Chemical Catalog # 1344-09-8, "27% Si02 & 14% NaOH) and milling for an additional 1 hour. After adding 2.0 grams of IN NaOH solution, the thin dispersion was mixed with the same type of viscose to give a ratio of approximately 70:30 by weight of inorganic compound to cellulose, deareated and converted into fiber in the same manner as in Example IA. The spinbath was composed of approximately 7.5% H2S04, 22.0% Na2S04, and 2.5% ZnS04 by weight at a temperature of about 45 degrees Celsius and a hot second bath of approximately 2.0% H2S04. A maximum stretch of 70% was achieved, fiber The collected was purified as in Example IA, but further purification by dipping in approximately 1% NaOH solution, then deionized water two times, then 2.5% acetic acid solution, then deionized water three times was needed.

Example 9A Production of a conductive tin/antimony oxide ceramic fiber 210.0 grams of a mixture of approximately 90:10 by weight of stannic oxide (Sn02) and antiminy oxide (Sb203) (Stanostat CP15G from Magnesium Elektron Industries) was added to a solution of 12.6 grams of a 30% aqueous solution of sodium polymethacrylate of an average molecular weight of about 10,000(Colloid™ 225 from Rhόne-Poulenc Surfactants and Specialties), and 12.6 grams of sodium silicate solution (Aldrich Chemical Catalog # 1344-09-8, ^"27% Si02 & 14% NaOH) in 184.8 grams of deionized water and milled overnight in a plastic jar. The mixture was very thick when it was added to the mill and was still thick, but uniform and thinner the next day. After adding 5.0 grams of IN NaOH solution, the dispersion was mixed with the same type of viscose at the same ratio as in Example 9 and deareated in the same manner as in Example IA. The spin mix was then converted into fiber as in Example IA except the immersion of the filaments in the spinbath was approximately 40 cm. and the spinbath, which was composed of approximately 7.5% H2S04, 22.0% Na2S04, and 2.5% ZnS04 by weight at a temperature of about 45 degrees Celsius had a volume of approximately 20 liters, replenished from a reservoir of approximately 20 gallons with a flow of about 1 gallon per minute countercurrent to the direction of the filaments. The filaments emerged from the spinbath and were wrapped three times around two godets of 0.628 meters circumference each, both rotating clockwise at 24.6 RPM and then into a hot second bath of approximately 4.0% H2S04 solution at approximately 90°C with an immersion length of approximately 25 cm. The filaments emerged from this hot second bath and were wrapped approximately 26 times around a wash drum of approximately 0.840 meters circumference rotating clockwise at a speed of approximately 27.6 RPM to give a godet stretch of approximately 50%. While around this drum, the filaments were washed with deionized water at approximately 57°||C falling on the filaments from holes in two tubes suspended above the wash drum. The filaments then left the wash drum to be wrapped about 15 times around a dryer drum of 0.678 meters circumference rotating clockwise at a speed of approximately 33.2 RPM at approximately 105°c. The relative speeds of the dryer drum and the wash drum imparted a relaxation of approximately 3% to the filaments. The dried filaments were then wound onto a tube onto a Leesona modified Model 959 winder.

While the invention has been shown and described with particular reference to specific embodiments thereof in the interest of complete definiteness, it will be understood that it may be embodied in other forms diverse from those specifically shown and described, without departing from the scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A process of producing fibers of refractory material, comprising: preparing a dispersion of particles of refractory material; mixing said dispersion with a carrier solution of a salt of cellulose xanthate to form a spin mix; forming a filament of regenerated cellulose from said spin mix using general wet spinning techniques, said filament having said particles dispersed therein; and heating said filament to sufficient temperatures and over sufficient durations to remove substantially all of said regenerated cellulose and to sinter said particles to thereby form said fibers of refractory material.

2. The process of claim 1, wherein said particles are low-reactivity particles selected from the group consisting of particles coated with an organic barrier, particles combined with an inorganic compound, precursor particles that convert to the desired refractory material during said process, or combinations thereof.

3. The process of claim 2, wherein said organic barrier is selected from the group consisting of ethylene, propylene, olefin and diene homopolymers and copolymers, olefin and diene homopolymers and copolymers having functional monomers including acrylic acid, maleic acid, maleic anhydride, hydroxyethyl methacrylate, and vinyl pyrrolidone, hydrocarbon waxes, fluorocarbon polymers including polytetrafluoroethylene, polyvinylidene fluoride, perfluorinated acrylates and methacrylates, urethanes, polyamides, polyurethanes, polyesters, polyethers, polyvinyl chloride, acrylate and methacrylate ester homo and copolymers.

4. The process of claim 1, wherein a low-reactivity dispersion medium is used in said dispersion to reduce reactivity, said low-reactivity dispersion medium selected from the group consisting of an aqueous salt, a cheelant solution, a non-aqueous medium, and combinations thereof.

5. The process of Claim 1, wherein a low-reactivity carrier solution is used in said spin mix to reduce reactivity, said low-reactivity carrier solution selected from the group consisting of a carrier solution with substantially no excess hydroxide, and a carrier solution with said salt of a cellulose xanthate dispersed in a non¬ aqueous medium, and combinations thereof.

6. The process of Claim 1, wherein the contact time between said particles and said carrier solution is minimized by mixing said dispersion with said carrier solution immediately before spinning.

7. The process of Claim 1, wherein a low-reactivity component is used in a spin bath to reduce reactivity, said low-reactivity component selected from the group consisting of phosphoric acid or its partial salts, partial salts of sulfuric acid, cheelants, pahydrochloric acid, organic acids, saline solution, nonaqueous compositions, and combinations thereof.

8. The process of Claim 1, wherein said refractory powder is a ceramic material.

9. The process of Claim 7, wherein said ceramic material is a precursor for a superconductive ceramic.

10. The process of Claim 9, which further includes the step of magnetically classifying the particles under cryogenic conditions, prior to mixing thereof in said carrier solution, thereby selecting only the superconductive, high purity components of the superconductive powder, which particles are less reactive with water.

11. The process of Claim 1, wherein said powder comprises particles each having a maximum dimension of from less than 1 to about 5 microns.

12. The process of claim 1, wherein said refractory powder is a material selected from the group consisting of oxides, nitrides, suicides, ferrites, carbides and elemental metals.

13. The process of claim 11, wherein said refractory material is selected from the group consisting of silicon carbide, aluminum nitride, silicon nitride, aluminum oxide, tin oxide, titanium carbide, hafnium oxide, zirconium oxide, titanium dioxide, molybdenum disilicide, lithium aluminate, ferrite, PZT (leadzirconium titanate), antimony oxide.

14. The process of claim 1, wherein said refractory material particles is a powdered, electrically conductive substoichiometric titanium dioxide having uniformly distributed within its molecular structure chemically combined metal selected from the group consisting of chromium, copper, nickel, platinum, tantalum, zinc, magnesium, ruthenium, iridium, niobium, vanadium, tin, and combinations thereof.

15. The process of claim 1, wherein said refractory material particles are powdered, electrically conductive, electrically conductive substoichiometric titanium dioxide having the basic formula TiO_x wherein x is a number in the region of about 1.55 to about 1.95.

16. The process of claim 15, wherein said substoichiometric titanium dioxide has an electrocatalytically active surface on at least part of the surface of the titanium oxide.

17. The process of claim 16, wherein said electrocatalytically active surface includes a material selected from the group consisting of platinum group metals or alloys, platinum group metal oxides, lead and lead dioxide.

18. The process of claim 15, wherein said x is about 1.65 to about 1.9.

19. The process of claim 18, wherein said x is about 1.7 to about 1.8.

20. The process of Claim 1 wherein the filaments of refractory material have one or more defined properties selected from current carrying capacity, range of physical or mechanical properties, electrochemical properties, electrorestrictive properties or other properties which are substantially the same as the corresponding properties of said refractory material from which said filaments are prepared.

21. The process of Claim 1, wherein said powder is greater than about 50% by weight of said cellulose xanthate.

22. The process of Claim 21, wherein said powder is greater than about 70% by weight of said cellulose xanthate.

23. The process of claim 1, wherein said particles are greater than about 20 percent by weight of said cellulose xanthate.

24. The process of claim 23, wherein said particles are greater than about 50 percent by weight of said cellulose xanthate.

25. The process of claim 1, wherein said spin mix contains a dispersant.

26. The process of claim 25, wherein said dispersant is selected from the group consisting of sodium silicate, sodium polymethacrylate, sodium polyacrylate, sodium alginate, the sodium salt of copolymers of acrylic acid, methacrylic acid, maleic acid, and itaconic acid, aminopropanol, triethanolamine, ethoxylated and/or propoxylated alkyl amines, carboxylic acids, alcohols or phenols, ethoxylated and/or propoxylated tristyrylphenol, ethoxylated and/or propoxylated castor oil or sorbitan, glycerin, polyethylene glycols, polypropylene glycols, random or block copolymers of ethylene and/or propylene oxide having hydroxyl, methoxy or other capped end groups, phosphate and sulfate esters of the ethoxylated and propoxylated alkyl amines, carboxylic acids, alcohols, phenols and phenol adducts, tristyrylphenol, castor oil or sorbitan, sodium dioctylsulfosuccinate, sodium dodecylbenzene sulfonate, sodium alpha olefin sulfonates, sodium alkyl naphthalene sulfonates, sodium naphthalene formaldehyde sulfates, amine oxides, pendant amide, such as acrylamide, vinyl pyrrolidone and aerylamido-2-methyl propane sulfonic acid homopolymers and copolymers, alkanolamides, ethoxylated alkanolamides, guar derivatives, sodium carboxmethylcellulose, hydroxyethyl cellulose, and methyl cellulose, and combinations thereof.

27. The process of Claim 1, wherein said spin mix contains a modifier.

28. The process of claim 27, wherein said modifier is incorporated into said dispersion before said dispersion is mixed with said carrier solution.

29. The process of claim 27, wherein said spin mix ages from about one hour to about 72 hours before spinning.

30. The process of claim 27, wherein said spin mix is frozen for a certain duration before spinning.

31. The process of claim 27, wherein at least one modifier is selected from the group consisting of 2-amino-l- propanol, polyethylene glycol, aminoalcohols including triethanolamine, diethanolamine, monoethanolamine, ethoxylated and/or propoxylated amines, aminomorpholine, aminophenol, aminopropanediol, aminomethyl propanol, aminomethylpropanediol, diethylethanolamme, amino pyridine, 2-(2-aminoethylanino)ethanol, (2-(2-aminoethoxy) ethanol, aminoethylpropanediamine, aminomethylbutanol, amino¬ carboxylic, sulfuric, sulfonic and phosphoric acids, di-, tri- and tetra-amines, polyamines, copolymers of ethylene oxide and propylene oxide, polypropylene glycol and propylene oxide and alkylene oxide adducts, and combinations thereof.

32. The process of claim 27, wherein said modifier is a combination of 2-amino-l-propanol and polyethylene glycol with a molecular weight of approximately 1500 in ratios of about 75:25 to about 25:75.

33. The process of claim 27, wherein said modifier is an amine that also serves as a dispersing agent.

34. The process of claim 27, wherein said spin mix contains from about 2% to about 10% by weight of modifier based on the weight of said cellulose xanthate.

35. The process of claim 27, wherein said spin mix contains from about 4% to about 8% by weight of modifier based on the weight of said cellulose xanthate.

36. The process of Claim 1, wherein said carrier solution comprises sodium cellulose xanthate.

37. The process of claim 36, wherein said carrier solution contains an excess of a strong base.

38. The process of Claim 37, wherein said strong base is NaOH.

39. The process of Claim 1, wherein said spinneret contains from 1 to about 20,000 holes each having a diameter of from about 18 to about 400 microns.

40. The process of claim 1, wherein said spin mix is spun into a acidic bath.

41. The process of claim 30, wherein said bath contains an inorganic acid.

42. The process of claim 41, wherein said inorganic acid is selected from the group consisting of sulfuric acid, hydrochloric acid, and phosphoric acid.

43. The process of claim 40, wherein said bath contains an inorganic salt derived from a strong base and a strong acid.

44. The process of Claim 43, wherein said salt is selected from sodium sulfate, ammonium sulfate and potassium sulfate.

45. The process of Claim 1, wherein said heating of said filaments to drive off said carrier is conducted in an oxygen-containing environment at a temperature of from about 200°C to about 600°C.

46. The process of Claim 1, wherein said sintering of said refractory powder particles is conducted in a furnace at a temperature of from about 750°C to about 2200°C.

47. The process of Claim 1, wherein said sintering of said refractory powder particles is conducted under a hydrogen atmosphere.

48. A filament of refractory material produced by the process of Claim 1.

49. A filament of Claim 1 that is electrically conductive.

50. An electrically conductive, corrosion-resistant article comprising a filament of Claim 49.

51. An electrode in accordance with Claim 50.

52. An electrochemical apparatus comprising means for recovering magnesium from sea water and including an electrode in accordance with Claim 51.

53. A fuel cell or battery including an electrode in accordance with Claim 51.

54. Electromagnetic shielding comprising a filament of Claim 49.

55. The process of claim 1, wherein said dispersion contains a dispersant.

56. The process of claim 27, wherein said spin mix contains above about 2.5% of said modifier based on the weight of said cellulose xanthate.

57. The process of claim 1, wherein said spin bath contains zinc sulfate.

58. A process of producing fibers of refractory material, comprising: preparing a dispersion of particles of refractory material; mixing said dispersion with a carrier solution of a salt of cellulose xanthate to form a spin mix, wherein said particles comprise greater than about 20% by weight of said cellulose xanthate forming a filament of regenerated cellulose from said spin mix using wet spinning techniques, said filament having said powder dispersed therein; and heating said filament to sufficient temperatures and over sufficient durations to remove substantially all of said regenerated cellulose and to sinter said particles of refractory material to thereby form said fibers of refractory material.

59. A process of producing fibers of refractory material, comprising: preparing a dispersion of particles of refractory material, wherein said particles are low-reactivity particles selected from the group consisting of particles coated with an organic barrier, particles combined with an inorganic compound, precursor particles that convert to the desired refractory material during said process, particles dispersed in a low-reactivity dispersion medium or combinations thereof; mixing said dispersion with a carrier solution of a salt of cellulose xanthate to form a spin mix; forming a filament of regenerated cellulose from said spin mix using wet spinning techniques, said filament having said powder dispersed therein; and heating said filament to sufficient temperatures and over sufficient durations to remove substantially all of said regenerated cellulose and to sinter said particles of refractory material to thereby form said fibers of refractory material.