JPH07310239A - Preparation of ceramic fiber and preparation of metal oxide fiber - Google Patents

Abstract

PURPOSE: To obtain a uniform and high-density ceramic coated fiber by electrochemically depositing a metal hydride material on an electric conductive fiber core with an electrophoretic method and then changing the hydride to a metal oxide by drying. CONSTITUTION: This method for producing a ceramic fiber is provided by housing a sol 10 containing a metal hydride having <=150 Å, preferably 10-15 Åparticle size selected from an aluminum hydride, yttrium hydride and their mixture with an alcohol having 50-70 molecular ratio in a sol vessel 12, feeding an electric conductive fiber core 16 consisting of a group of a carbon, glass, silicone carbide and silicon nitride, Al, Fe, Ni, Ta, Ti, W, Nb and their alloy from a spool body 18, also charging direct potential of 0.1-100 v, preferably 1-50 v and more preferably 35-50 v between the fiber core 16 and a cathode 26 to electrochemically deposit the metal hydride to increase more than the diameter of the fiber core 16 by an electrophoresis and also remove the co- generated hydrogen gas, then heating for drying at least at >=850 deg.F in an oven 28 to change the hydride to a metal oxide and winding up on a spool 32 to obtain the ceramic fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ceramic materials in general, and more particularly to the formation of filaments from oxides or mixed oxides by electrophoretically depositing a colloidal material from a sol.
It relates to a method of thickly coating a wire or tow to form ceramic fibers.

Further, by using aluminum oxide, ceramic materials such as yttrium, and a sol such as yttrium-alumina-garnet (YAG) which is a mixture thereof, and by electrodeposition of these on the substrate by electrophoresis. It relates to high density and uniform fiber formation without bias. The present invention does not require the costly preparatory steps for electrodepositing the ceramic on the substrate associated with the prior art.

[0003]

2. Description of the Related Art It is well known that a surface coating on a base material gives a surface characteristic different from that of the original base material, and has increased strength, adaptability to high temperature, oxidation resistance, wear resistance and It is used to obtain various effects such as corrosion resistance.

By providing a surface coating with suitable properties, the cost of obtaining a substance configured to obtain the required moderate properties can be substantially reduced. For example, ceramics are frequently used as surface coatings to make metals with relatively low heat resistance usable in high temperature environments.

Ceramic materials are also often used in the form of powders, fibers, or whiskers to increase the strength of metal composites. Ceramic fibers are particularly needed in metal composites, especially those consisting of oxides, mixed oxides or doped oxides, to act as reinforcing elements.

[0006]

In the past, for example, glazes, enamel, coatings (high pressure compression of materials), as well as vapor deposition, cathode sputtering, chemical vapor deposition, flame spraying and plasma spraying for fixing ceramic materials to the substrate. Various methods such as vapor deposition such as spraying have been tried. Electrophoresis was also tried, like any other expertise, but with limited success.

For example, electrodeposition of ceramic materials has often been performed in the enamel industry. In ceramic coatings by this technique, the ceramic material is ground to a fine particle or powder size, ground, transferred into a suspension and electrophoretically deposited on the substrate. Other well known methods include depositing the ceramic coating from a slurry of powder in suspension (usually an aqueous medium). However, these methods make it difficult to obtain powder particle sizes of less than about 2 microns, thus limiting the quality of the coatings formed and their potential application to wire or fibrous substrates. Accompany.

Sol-gel technology has recently evolved as a source of good submicron ceramic particles with excellent uniformity. This sol-gel technique fundamentally produces ceramics by low temperature hydrolysis and peptization of the metal oxide precursors in solution rather than sintering the compacted powder at high temperature.

In the prior art, hydrolysis and peptization of a corresponding metal alkoxide such as secondary butoxylated alumina [Al (OC ₄ H ₉ ) ₃ ] is carried out in water with an acid peptizer such as hydrochloric acid, acetic acid or nitric acid. Attention was directed to producing a sol of a metal oxide (actually a metal hydroxide or a metal hydrate) by carrying out. Hydrolysis of alumina alkoxide is described by Jordas in "A Method for Producing Alumina Sol from Alkoxide" 54th volume (1975) by the Ceramic Society of America.
(Published annually), pages 3 to 290 to 290. According to this, in the hydrolysis of the alumina alkoxide precursor, the molar ratio of water to the precursor is 100.
In pair 1, peptization is carried out at 90 degrees Celsius using 0.07 mole of acid per mole of precursor. After gelling and drying, the dried gel is calcined to form alumina powder.

According to Segell, US Pat. No. 4,532,072, cold water and alumina alkoxide are mixed in stoichiometric proportions to react them to form a peptizable alumina hydrate, which is then hydrated. An alumina sol is produced by peptizing the material with a peptizer in an aqueous medium to form a sol of the alumina mixture.

US Pat. No. 4,801,399 to Clark et al.
The publication discloses a method of obtaining a metal oxide sol. According to this, the metal alkoxide is hydrolyzed in an excessive amount of an aqueous medium, and peptization is performed in a metal salt such as nitrate to obtain particles of 0.0001 micron to 10 micron.

US Pat. No. 4,921,731 to Clark et al. Discloses a method of ceramic coating a substrate such as a wire by thermophoresis with a sol of the type produced by the method taught in US Pat. No. 4,801,399. .
Also abandoned Clark et al. US patent application 06/84
According to No. 1,089 (filed February 25, 1986),
A method of forming a ceramic coating on a base material such as a filament, a ribbon or a wire by electrophoresis of these sols is disclosed. However, according to the usage example of this method, the coating obtained by using electrophoresis is non-uniform, and cracks, no plating, generation of air bubbles, peeling, and peeling occur. During the electrophoresis, formation of hydrogen bubbles was observed at the cathode.

Therefore, there is a need for an electrophoretic electrodeposition method used to form thick ceramic coatings on filaments, fiber tows, wires, etc. for the production of ceramic fibers. There is a need for a method of making ceramic fibers for use as reinforcing elements, especially in metal composites.

[0014]

The present invention is a unique fixing method,
In particular, the present invention provides a method for producing a defect-free ceramic fiber obtained by research on a fixing method suitable for producing a metal oxide fiber.

In the present application, "filament" means one fiber material, "fiber tow" means an array of multifilament yarns or filaments, "wire" generally means a metal filament or tow, and "fiber". "Core" means a filament, fiber tow, or wire suitable for coating by the method of the present invention. Also, "ceramic coated fiber" or "coated fiber" means a fiber core of conductive material anchored on a uniform ceramic layer, such that the diameter of the fiber core is greater than the thickness of the applied ceramic, or It means a fiber core made of a material that becomes conductive due to a carbon flash coat or a plating layer. On the contrary, "ceramic fibers" or "fibers" are intended to mean, for convenience, conductive fiber cores fixed on a uniform ceramic layer such that the thickness of the ceramic layer is greater than the diameter of the fiber core. Generally, in the art, the above distinction of relative thicknesses of surface layer and core is to limit the boundaries between coated fibers. In both cases,
The fiber core material can be removed by a technique such as acid dissolution and combustion, and after the removal, it becomes a hollow ceramic cylinder, that is, a ceramic fiber.

The object of the present invention is to provide a sol electrophoresis method which can be used for the formation of ceramic fibers and which can also be used for the formation of defect-free ceramic fibers having excellent homogeneity.

According to the present invention, there is obtained a ceramic fiber manufacturing method characterized by comprising the following steps.

A) Providing a sol having metal hydrate particles selected from the group consisting of aluminum hydrate, yttrium hydrate, and mixtures thereof. The size of the particles is less than 150 Å, the sol contains alcohol, and the molecular ratio of the alcohol to the metal hydrate is approximately 50-70.

B) By applying a DC potential between the fiber core and the anode, particles from the sol are electrodeposited on the conductive fiber core by electrophoresis, and the potential is about 0.1 to 100. The metal hydrate is applied with a bolt for a time sufficient to uniformly electrodeposit the metal hydrate, the thickness of the electrodeposition is greater than the diameter of the fiber core, and hydrogen generated by the electrical induction is used. Supply gas removal method.

C) The metal hydrate coated fibers are removed from the sol.

D) The coating is dried and the metal hydrate is converted into the corresponding metal oxide.

E) Recoating with ceramic fibers.

According to the present invention, a) The conductive fiber core is continuously passed through an electrophoretic electrolytic cell containing a sol produced by the following steps: 1) Hydrolysis of an organometallic compound and alcohol Oxidation is carried out simultaneously in an aqueous medium consisting of water and alcohol.

2) Peptization of the reaction mixture according to the above with a monoacid or acid source.

3) Dehydration and dealcoholation of the reaction mixture by removing excess water phase.

4) The unreacted alcohol is evaporated and dehydrated, and further removed.

5) The secondary alcohol is added to the concentrated sol so that the molecular ratio of alcohol to metal hydrate is about 50 to 70 and the particle size of the metal hydrate is about 10.
Alcoholize again to ~ 150 Å.

B) An electric potential is applied between the fiber core immersed in the sol and the other electrode, and metal hydrate particles are continued on the fiber core until their thickness is greater than the diameter of the fiber core. Electrolysis, c) operating the electrolysis cell at a potential of about 1 to 50 volts to reduce hydrogen formation, and d) providing a method for dispersing and removing hydrogen gas from the electrolysis cell. And e) a metal, characterized in that the fiber core and the metal hydrate particles electrodeposited on the fiber core are heated after the fiber core comes out of the sol to form a metal oxide fiber. A method for continuously producing oxide fibers is obtained.

[0029]

[Function] The metal precursor is hydrolyzed in an organic solvent having an excess amount of molecule, and after deflocculation, dehydration and dealcoholation steps, water is removed by a method such as evaporation, and the sol is concentrated and then alcohol is added again. By adding, colloidal particles having an extremely small particle size can be obtained.

[0030]

EXAMPLES The present invention is suitable for use in forming ceramic fibers. The sols disclosed herein can also be used to form multilayer ceramic coatings on fibers, and it is possible to obtain mixture coatings by using a filler together with the gel prior to electrophoresis. .

The sols used in the process of the present invention are various organometallic compounds, namely alumina, chromium ion-doped alumina, yttria, and mixtures thereof, yttria-alumina-garnet (3Y _2).
O ₃ · Al ₂ O ₃₎ is formed from a yield metal oxides such as. However, in the present application, U.S. Pat.
Alumina, chromium ion-doped alumina, yttriasol and the like described in Nos. 7,716 and 07 / 637,717 are specifically described. While the above patents are filed with this application and described herein by reference, it is believed that the present invention is not limited thereto and is applicable to prior art sols, with certain modifications if necessary. obtain.

Electrophoresis is an electrodeposition technique in which a normally non-conductive material in a colloidal suspension moves to a specific electrode when it is exposed to the outside of an electric field. Colloids in solution are known to form surface charges associated with suspension media as a result of a variety of possible mechanisms such as lattice defects, ionization, ion absorption, ion dissolution. For metal oxides such as alumina, the surface charge is a result of ionization and is generally positive and below about 7 in the preferred pH range.

During electrophoresis, the positively charged colloids migrate to the cathode and form a compacted layer of particles on the cathode.
The physical properties of the electrodeposited coating are related to compression and adhesion on the substrate. Generally, the stronger the compression and solidification of the colloidal particles electrodeposited on the substrate, the higher the mechanical properties of the coating and the stronger the protective power.

The present invention can be used for electrophoretic electrodeposition coatings on a variety of substrates, which can be metallic or non-metallic. Examples of materials that can be used for the fiber core material include carbon, glass, silicon carbide, silicon nitride, and metals such as aluminum, iron, nickel, tantalum, titanium, molybdenum, tungsten, remium, niobium, and alloys thereof. To be Any material that is normally conductive or that becomes conductive can be used. The diameter of the fiber core is not critical and can be selected depending on the desired diameter of the fibers to be formed and its end use. Considering the removal of the ceramic layer thicker than the fiber core and the core, the diameter of the core is 0.
1 mil to 3 mils is preferred. The final diameter of the fibers formed is about 7.6 x 10 depending on the strength required and other properties.
^-3 (mm) (= 0.3 mil) (or less) to about 0.23 (mm)
(= 10 mils) (or more) is preferred.

According to the present invention, a sol having colloidal particles of about 10 to 150 angstrom can be obtained by hydrolyzing an organometallic compound and peptizing it. A preferred particle size is about 50-100 angstroms, and if the particle size is within this range, the coating material and the fiber core make good contact, so that the coated particle is very well in the coating layer. Cohesive, filling and thus excellent properties of the coating with abrasion resistance and high temperature compatibility are obtained.

Sols suitable for use in the present invention are prepared by hydrolyzing and peptizing the corresponding organometallic compound in an aqueous medium. Suitable organometallic compounds are metal alkoxides, especially metal secondary butoxys, ethoxides and methoxides of aluminum, yttrium,
And mixtures thereof. Suitable electrophoretic electrodeposition techniques for sol preparation of the present invention are described in co-pending U.S. patent application Ser. No. 07 / 637,717, which is filed with and is incorporated herein by reference.

However, it is also possible to use other sols in the process according to the invention. The method of the present invention comprises a sol electrophoresis method suitably formed for a particular purpose.
To achieve the object of the invention, very small particles,
That is, it is desirable to use colloidal sols having a diameter of less than about 150 Å.

Therefore, the above object can be achieved by using a sol whose manufacturing method is different from that of the prior art. That is, the metal precursor is hydrolyzed in an excess amount of an organic solvent, and then deflocculation, dehydration and dealcoholization are performed, water is removed by a method such as evaporation, and the sol is concentrated, and then metal water is added. 70 moles of alcohol per mole of Japanese food
Alcohol is added to give a molar molecular ratio.

Although the phase conversion reaction that occurs during a given sequence of this manufacturing process has not been completely elucidated, it results in a bridge of the Al00H species during the dehydration and dealcoholation after electrophoresis according to the invention. It is theorized that the bonding is less likely to occur, tear, peel, and peel.

After the sol is concentrated, alcohol is added again, that is, re-alcoholization forms extremely small colloidal particles, and a highly stable sol which has long-term storability and favorable characteristics for electrophoresis is obtained. be able to. The sols can be formulated with the respective organic solvent, peptizer and alcohol added. Generally, a method for producing a sol suitable for electrophoresis has the following steps.

A) In an aqueous medium containing water and an organic solvent, the organometallic compound is simultaneously hydrolyzed and alcoholized.

B) Peptization of the above reaction mixture with a monovalent acid or acid source.

C) Dehydration and dealcoholation of the reaction mixture is carried out by removing excess water phase, ie by decanting or pipetting.

D) Removal of unreacted alcohol by evaporation. Concentration and / or weight reduction is generally performed by boiling strongly.

E) Re-alcoholizing the concentrated sol or adding alcohol to form a sol suitable for electrophoresis.

In the above production, it is necessary to very accurately adjust the molecular ratios of the materials used and the various stages of production. Table 1 below shows
A general range, a preferable range, and a most preferable range of the molecular ratio of the materials in the above manufacturing process, and the dehydration / dealcoholization and weight loss ratios of the sol are shown.

[0047]

[Table 1]

The present invention is based on several principles not used in the prior art.

First of all, it is known in the prior art that the evaporation of hydrogen during electrophoretic electrodeposition causes various problems and defects in the resulting coating. In fact, application of a DC voltage of about 3 V or more causes hydrogen vaporization. The present invention overcomes the above problems by using various techniques such as suppressing the generation of hydrogen gas to some extent and supplying a means for dispersing and removing this actually generated hydrogen.

This is because the water content in the sol is exchanged with an organic solvent, that is, alcohol as much as possible, and the fiber core is moved at a suitable speed while utilizing a low potential to form an electrodeposition layer having a desired thickness. And at the same time let the hydrogen escape,
The hydrogen bubbles formed by electrophoretic electrodeposition provide a means to prevent them from being embedded in the material layer, and the components and concentration of the sol are precisely adjusted to keep the concentration of water in the electrode to a minimum, In addition, generally, a suitable electrodeposition voltage and electrodeposition ratio are used throughout, and hydrogen gas-free electrodeposition can be realized by operating with a fiber core.

Sols suitable for use in the present invention are prepared by the following method, but particular care should be taken not to expose the reaction mixture to air. In the examples of the present application, the alumina-forming sol formed from the second aluminum butoxyxide precursor was specifically described, but the present invention is not limited thereto.

Example 1 For the production of alumina sol, a 4000 ml glass reaction vessel, various heating mantle glasses and a laboratory mixer with a stir bar made of Teflon with variable speed control,
An inlet equipped with a Teflon tube for inserting a liquid into the bottom of the reaction vessel and a water cooling condenser were used in combination. Cooling water was run through the condenser and 2500 grams (corresponding to 138.8 moles or 2500 ml) of non-ionized water was weighed and poured into the closed reaction vessel, after which the heating mantle was activated to bring the water temperature up to 88 ° C. Heat to 93 ° C. This temperature was then maintained. After the water reaches this temperature,
The motor of the mixer was operated and the water was stirred vigorously. In an individually sealable glass transfer container, 357.5 grams (corresponding to 1.5 moles or 357.5 ml) of secondary butoxylated alumina [Al (OC ₄ H ₉ ) ₃ ] 288.
86 (corresponding to 3.897 mol or 357.5 ml) of 2-butanol was mixed.

Experience has shown that exposure of this mixture or secondary aluminum butoxyxide to air for a minimum amount of time has a deleterious effect on the sol formed. Therefore, great care must be taken to prevent this.
After the water reached the desired temperature, the mixture of secondary butoxy and butanol in the transfer container was connected to the inlet of the reaction vessel. It was then slowly metered directly into the non-ionized hot water over 5 minutes. Once the mixture was all poured into the water, the inlet was closed with a valve and the transfer container was removed. The mixture of water, secondary buttocks and butanol is then hydrolyzed for 1 hour at constant temperature while stirring vigorously. After one hour, the mixture was still vigorously stirred at constant temperature and the solution of the sol mixture was dissolved by connecting a glass syringe containing 8.18 grams (0.224 mol or 6.875 ml) of hydrochloric acid to the container inlet. I did this. The inlet valve was opened and the acid was metered directly into the sol mixture.

The valve was closed and the syringe was removed and filled with air. The syringe was then reconnected to the entrance. All acid was injected into the system by injecting air into the container. The valve was closed and the syringe was removed.

Heating and stirring is about 16 until the sol becomes transparent.
It continued for hours. After that, the heating was stopped and the stirrer and motor equipment were removed. After the mixture had cooled, the sol and alcohol were separated and the alcohol was removed by pipetting.

At this time, it was found that even if a small amount of alcohol remained in the sol, it did not adversely affect the sol. The pH value of the sol was measured to be pH 3.90. It has been found that this initial sol has good storage stability and can be stored before further production to obtain a sol suitable for electrophoresis.

The sol after this is specially formulated for the specific purpose of forming coated fibers in the continuous process.
This particular formulation is also suitable for coating metal or other material substrates in alumina composites with fiber cores, or composites (composites are chopped fibres, platelets, powders, particles, etc.). is there.

This sol was obtained from the first sol produced above. 390 ml of the sample sol prepared above was heated at about 93 ° C in an open glass beaker.
It is heated to evaporate volatile substances, ie alcohol, excess water. The sol was reduced to 250 ml, or 64 percent of the original volume, and heated until the viscosity increased.

Thereafter, the heating of the reduced sol was stopped,
Cooled to room temperature. 750 ml of reduced sol
(63 of 1 mol of alcohol in aluminum hydrate
Mol) ethyl alcohol. The sol and alcohol were vigorously stirred and sealed in an airtight container for storage. The pH value of this sol was pH 3.8. Further, in order to prove that the sol can be stored for a long period of time, the sol was left as it was for 5 months, and then used for electrophoresis electrodeposition.

To thickly electrophoretically deposit a ceramic oxide coating onto filaments, fiber tows, or wires, and hereinafter fiber cores, an apparatus as shown in FIG. 1 can be used. According to the present invention, any fiber core can be coated as long as it is a conductive material or a material that can be made conductive. For example aluminum,
Fibers such as carbon, copper, silver and platinum are conductive, but cotton,
Fibers such as polyester must be electrically conductive for use in the present invention. These fibers may be coated with a conductive metal, carbon or the like by conventional techniques such as flame spraying or plasma spraying.

By supplying an adjusted electric potential in a colloidal solution having charged particles, that is, by moving the colloid to the fiber at a specific ratio adjusted by sol chemistry and supplying an electric potential between the metal electrodes, It can be electrophoretically coated. Metallic anodes include copper, aluminum, silver, gold, platinum, or other conductive metals, with platinum being preferred.

The fiber core is electrically conductive and provides the cathode surface for the purpose of electrophoresis of positively charged sols. When using a basic peptizer for sol production, the electrodes are, of course, reversed. The colloidal particles are uniformly gathered around the fiber core, along the fiber core, to form a thick, dense, uniform adhesive coating, having chemical and mechanical properties defined by sol chemistry, After being applied, coating is followed by heat treatment.

Since the continuous major axis of the fiber core extends through the sol, the coating treatment can be effectively and continuously repeated. After the fiber core has been coated with the desired coating structure, it may be heated at a suitable temperature with a furnace, laser, or other heat source. This processing step will be described with reference to FIG.

The sol or colloidal solution 10 is contained in a sol tank 12 having a thin film 14 at the lower end. The conductive fiber core 16 supplied by the bobbin 18 first passes through a single or a set of rollers or pulleys 22 connected to various DC power sources 24, first in a cleaner 20, a heat source such as a laser or a furnace, Clean with a chemical bath or other suitable cleaning means.

From here, the fiber core is the sealing thin film 14,
It passes through the sol 10 and the annular anode 26. Vertical anode /
Although the sol baths are shown, they can be configured in parallel or at any suitable angle. The length of the anode can be increased by this positioning, and can be increased to 6.096 meters (20 feet) or more.

After passing the annular anode 26 for electrophoretic coating, the coated fibers pass through one or more furnaces 28 for drying and phase conversion. Although the furnace is illustrated as being electrical with an AC power supply 30, it may be any form of heat source.

The ceramic coated fiber core is then collected on the spool 32. When the coating material is electrodeposited thicker than the fiber core, this is called a ceramic fiber. Such a device is useful for forming ceramic fibers by adjusting variable factors such as the ratio of the fiber core passing through the annular anode, the potential provided at the anode, the sol concentration, the effectiveness of the hydrogen gas removal process.

These factors are decisive in the production of defect-free, uniform, dense, strongly adherent ceramic fibers. The removal of hydrogen from electrodeposition is particularly important as the presence of hydrogen during the heating and drying steps results in the formation of escape pathways and hence cracks.

An effective way to reduce hydrogen formation during electrophoresis is to limit the amount of water in the sol for electrophoresis. The non-association of water with hydrogen and oxygen provides a source of bubbles that cause defects in the electrodeposited metal oxide layer. As a method of solving this, dehydration or concentration of the sol during sol production by evaporation is performed as much as possible to the extent that the sol does not become a gel, and then this water content in the sol is removed with an alcohol such as methanol, ethanol, isopropyl, or butanol. There is a method of exchanging by adding.

It has been found that the molecular ratio of alcohol to metal hydrate in the sol prepared in Example 1 is desired to be greater than 50 and the formation of hydrogen during electrophoresis is significantly reduced. In general, it has been found that an alcohol molecular ratio of about 50 to 70 is effective, about 55 to 69 is even better, and about 58 to 67 is most effective.

An alternative method for removing hydrogen is to continuously flow bubbles or a bubble of inert gas to sweep the surface of the fiber core and the coating electrodeposited thereon. These bubbles are somewhat larger than the hydrogen bubbles formed by electrophoresis and the flow velocity of these bubbles must be greater than the speed at which the fiber core moves through the sol.

Any hydrogen formed thereby is swept by air or inert gas. Therefore, hydrogen is carried to the surface of the sol or the upper layer of the electrophoresis tank, and is released into the atmosphere or evacuated. Such bubbles may be generated by conventional methods or from a compressed gas source, thus forming an escape path for hydrogen gas at the interface between the sol and the coated fibers.

In order to obtain a coating of the desired thickness, the potential has to be adjusted in consideration of the throughput rate of the fiber core. Although hydrogen formation can be suppressed by using a low voltage, electrophoresis must take more time to obtain thick electrodeposition. This can be achieved by reducing the fiber core passage speed or lengthening the anode itself.

On the contrary, when the voltage is increased, hydrogen formation is promoted. It is therefore necessary to adjust the fiber core throughput rate and coating voltage depending on the desired coating thickness and the particular sol and fiber core used. The potential used is about 0.1
Potentials of from volt to 100 volts or higher are good, with about 1 volt to 50 volt being more preferred, and about 35 volt to 50 volt being best.

The electrodeposition period of the fiber core, that is, the time for a specific point on the fiber core to pass through the length of the annular anode depends on the conductivity of the specific fiber core, the composition of the specific sol, and the applied voltage. . Therefore, the coverage varies greatly. For example, when the fiber core is coated with YAG sol, the moving speed of the fiber is much faster and the voltage is much lower than when the similar fiber is coated with alumina sol.

As described above, the variation in the length of the anode affects these factors, that is, if the anode is long, the moving speed of the fiber core is increased and / or the voltage is decreased to obtain the same result. .

In order to obtain a defect-free, uniform, high-strength fiber, the throughput rate is about 365.8 to 487.7 meters (about 1200) while sweeping by continuous flow of bubbles. .About.1600 feet) and a voltage of 35 to 50 volts is desirable for operation. This suppresses formation of cracks and no plating during electrodeposition due to the presence of hydrogen.

In order to obtain the highest quality fiber, electrophoresis at 50 V or less is desirable, but it causes a flow of air bubbles, and depending on the type of sol and the passing speed of the fiber core passing through the sol, a potential up to 100 V can be obtained. If you can, you can get a fairly good quality fiber.

The method of removing hydrogen from the surface of the fiber core can also be realized by mechanical means such as vibration including ultrasonic vibration of the sol.

The concentration of metal hydrate in the sol, ie the applicability of the material used for electrodeposition, is one additional factor in the success of electrodeposition. This depends on whether the sol can be recirculated to maintain a nearly uniform concentration. A large tank (not shown) containing the sol can be provided with a recirculation pump for passing the sol stream through the sol tank 12. It is also necessary to add new sol necessary to maintain the desired degree of concentration.

After passing through the sol bath, the metal hydrate electrodeposited freshly coated fiber core needs to be dried. Air drying may be used, however, it is too time consuming to limit continuous processing and results in a hydrate coating rather than an oxide. The coated fiber core is preferably passed through a heating and drying zone, such as a furnace, to remove water and / or alcohol trapped in the electrodeposited particulate matter during electrophoresis.

Further, this makes it possible to convert the phase from the hydrate to the oxide. When the thickness of the coating layer is larger than the diameter of the fiber core, it is possible to reliably obtain the ceramic fiber. By this heating or curing step, it is possible to control the degree of phase conversion and obtain a desired phase such as Allumina, yttria, or alumina-yttria-garnet in the surface layer.

The temperature for hardening the hydrate can be readily determined by the skill of the operator, but the preferred temperature for forming the oxide from the metal hydrate is 850 to 12 degrees Fahrenheit.
It is 00 degrees or more.

In some cases, the fiber core itself becomes exhausted during the curing process after being exposed to elevated temperatures for an extended period of time, resulting in a ceramic cylinder, tube or jacket referred to as "freestanding," ie, ceramic fibers. Becomes The flexibility of the ceramic fiber varies depending on the concentration of the filler, the degree of phase conversion, the thickness of the ceramic, and the like.

In most cases, however, it will be wound on a hoist spool having a diameter of about 4 inches or more. Such flexibility is very important for the use of such fibers. In accordance with the present invention, various fiber cores have been coated to form ceramic fibers suitable for use in metal composites. In this case, the oxide fibers act as a reinforcing material and / or a reinforcing material.

Example 2 The alumina sol formed in Example 1 was used to electrophoretically deposit a 4 mil coating on a 0.5 mm diameter tungsten wire. A strongly adherent coating was obtained by electrodeposition using the method described above. Also, after curing, Al ₂ O ₃ fibers with a cross section of about 8 mils were obtained.

Example 3 According to Example 1, 3 weight percent (weight percentage) chromium doped alumina was formed. A thick layer of ion-chromium doped alumina was electrophoretically electrodeposited onto a 2 mil diameter Incoloy 909 alloy wire using the electrodeposition method of the present invention. After curing, alumina fibers with a diameter of about 6 mils were obtained.

Example 4 Alumina sol was used for electrophoresis at 35 volts as described above. Using 12.5 micron tungsten-3rhenium wire, 457.2 meters (150
It went at a speed of 0 feet. A 6-8 micron thick coating was applied to form fibers about 25-28 microns in diameter. When the fiber core throughput rate was reduced to 228.6 meters (750 feet) per hour, the coating thickness was 2
Doubling, forming about 40 micron alumina fibers, indicating a direct relationship between feed rate and results.

Example 5 A thick coating of hydrated alumina was electrodeposited on the niobium fiber core by the above treatment. When cured at 1200 degrees Fahrenheit, the niobium nuclei were oxidized to form hollow alumina cylinders.

The present invention has been shown to be useful for electrophoretic electrodeposition of ceramic fibers. Such fibers have found great potential for use as reinforcing fibers in various composite materials.

The present invention disclosed above is subject to alterations, changes and modifications that can be considered by those skilled in the art. Further, changes, changes and modifications are made within the scope of the present invention described in the attached claims.

[0092]

The electrophoretic method of the present invention forms colloidal particles of extremely small size by re-alcoholization of the sol,
A sol manufacturing method with high stability and capable of long-term storage. The sol produced by this method is also used to provide a uniform and dense ceramic coating. Furthermore, by providing a means for dispersing and removing hydrogen, which causes various defects in the coating, it is possible to further improve the quality of the ceramic coating produced.

[Brief description of drawings]

FIG. 1 is a simplified diagram of an apparatus suitable for use in applying a ceramic coating to a fiber core by electrophoresis from a sol according to the present invention.

[Explanation of symbols]

 10 ... Sol or colloid solution 12 ... Sol tank 14 ... Thin film 16 ... Conductive fiber core 18 ... Thread winding 20 ... Cleaner 22 ... Pulley 24 ... DC power supply 26 ... Annular anode 28 ... Furnace 30 ... Power supply 32 ... Winding thread winding

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Robert Jay. Wright United States, Florida, Tekester, Willow Road 23 (72) Inventor Jarrett El. Spence USA, Florida, Jupiter, North 182 Nd Place 12319

Claims (21)

[Claims] 1. A method for producing a ceramic fiber, comprising the steps of: a) supplying a sol having metal hydrate particles selected from the group consisting of aluminum hydrate, yttrium hydrate, and mixtures thereof; Particle size of less than 150 angstroms, the sol contains an alcohol having a molecular ratio of the alcohol to the metal hydrate of about 50-70, and b) applying a DC potential between the fiber core and the anode. By this, the particles are electrophoretically deposited on the fiber core having conductivity higher than that of the sol, and the potential is about 0.1 to 100 V, and the metal hydrate is uniformly deposited on the fiber core. Is applied for a sufficient time so that the thickness of the electrodeposition is larger than the diameter of the fiber core, and the hydrogen gas generated by the electrical induction is C) removing the metal hydrate coated fiber from the sol, d) drying the coating, converting the metal hydrate to the corresponding metal oxide, and e) coating the ceramic fiber again. A method for producing a ceramic fiber, comprising the steps of: 2. The method for producing a ceramic fiber according to claim 1, wherein the method of removing the hydrogen gas includes a method of removing bubbles from the fiber core by generating bubbles during electrophoresis. Method. 3. The method for producing a ceramic fiber according to claim 2, wherein the electric potential is about 1 to 50 volts. 4. The method of claim 3, wherein the electric potential is about 35 to 50 volts. 5. The fiber core comprises the group consisting of carbon, glass, silicon carbide, silicon nitride, and metals such as aluminum, iron, nickel, tantalum, titanium, tungsten, rhenium, niobium and alloys thereof. The method for producing a ceramic fiber according to claim 1, which is characterized in that. 6. The method of claim 5, wherein the ceramic is alumina and the fiber core is an iron-based alloy. 7. The method for producing a ceramic fiber according to claim 5, further comprising a sol recycling step for maintaining the concentration of the sol. 8. The method according to claim 5, wherein the fiber core coated with the metal hydrate is heated at a temperature of at least 850 degrees Fahrenheit. 9. The method for producing a ceramic fiber according to claim 8, wherein the metal hydrate is an aluminum hydrate. 10. The method for producing a ceramic fiber according to claim 9, wherein the fiber core is selected from carbon, silicon carbide, iron, molybdenum, tungsten, rhenium, niobium, and alloys thereof. 11. The method for producing a ceramic fiber according to claim 8, wherein the metal hydrate is yttrium hydrate. 12. The method for producing a ceramic fiber according to claim 11, wherein the fiber core is selected from carbon, silicon carbide, iron, molybdenum, tungsten, rhenium, niobium and alloys thereof. 13. The method for producing a ceramic fiber according to claim 8, wherein the metal hydrate is chromium ion-doped aluminum hydrate. 14. The method for producing a ceramic fiber according to claim 8, wherein the metal hydrate is a mixture of aluminum hydrate and yttrium hydrate. 15. A method for producing a metal oxide fiber by a series of steps, which comprises: a) the following steps, ie, 1) simultaneously hydrolyzing and alcoholizing an organometallic compound in an aqueous medium consisting of water and alcohol. 2) Peptization of the reaction mixture according to the above with the monovalent acid or acid source is performed, 3) Dehydration and dealcoholation of the reaction mixture by removing the excess amount of aqueous phase, 4) Unreacted alcohol 5) Add secondary alcohol to the concentrated sol to give a molecular ratio of alcohol to metal hydrate of about 50.
˜70, the conductive fiber core is continuously passed through an electrophoretic cell having a sol prepared by alcoholizing again so that the particle size of the metal hydrate is about 10˜150 Å. B) applying an electric potential between the fiber core immersed in the sol and the other electrode to continuously bring the metal hydrate particles onto the fiber core until their thickness is greater than the diameter of the fiber core. C) operating the electrolysis cell at a potential of about 1 to 50 volts to reduce hydrogen formation, d) dispersing and removing hydrogen gas from the electrolysis cell, and e) fibers. A metal oxide fiber characterized by forming a metal oxide fiber by heating the core and the metal hydrate particles electrodeposited on the fiber core after the fiber core comes out of the sol. Manufacturing method. 16. The fiber core comprises carbon, glass,
The group consisting of silicon carbide, silicon nitride, nitrogen, and aluminum, iron, tantalum, titanium, nickel,
2. A material selected from molybdenum, tungsten, rhenium, niobium and alloys thereof.
5. The method for producing the metal oxide fiber according to 5. 17. The method for producing a metal oxide fiber according to claim 16, wherein the metal oxide is selected from alumina, chromium ion-doped alumina, yttria, and yttria-alumina-garnet. 18. The thickness of the coating is greater than or equal to the diameter of the fiber core.
The method for producing a metal oxide fiber according to. 19. The alcohol is selected from methanol, ethanol, isopropanol, and butanol, and the organometallic compound is secondary butoxy, ethoxide,
19. The method for producing a metal oxide fiber according to claim 18, wherein the metal oxide fiber is selected from the group consisting of aluminum methoxide, yttrium, and a mixture thereof. 20. The metal according to claim 15, wherein the hydrogen gas is diffused and removed by introducing a bubble flow of inert gas into the vicinity of the fiber core while the fiber core passes through the electrolytic cell. Oxide fiber manufacturing method. 21. The diameter of the fibers is about 7.6 × 10 ⁻³ (mm)-
The method for producing a metal oxide fiber according to claim 20, wherein the metal oxide fiber has a thickness of about 0.23 (mm).