DE1417713B - Process for the production of finely divided carbides, borides and silicides - Google Patents

Description

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Known processes for the production of carbides, material in a percentage, based on the borides and silicides of refractory metals and the total weight of the mass,
of carbides of boron and silicon and of silicon

ciumboriden give products that have a massive form 18 Z) ² + YlD + 2

exhibit. Such products are obtained by 5 5Z) (o Z) ² 4- 1 8Z) + 12) ' ^S

Grinding into a so-called "finely divided" form
led, but the size of the most discreet, smallest

Particles of such metal-like compounds are where D equals the average part approximately in the size range in which the particle size in millimicrons and ρ equals the density of the rial passes through a 325-mesh sieve (0.044 mm). It is io metal-like compound in g / ml.
It is generally known that even in the best case by the invention, the hard substances, such as metal-like reactants selected in redu compounds, cannot be comminuted to a grain size in the sub- zing conditions and in an inert atmospheric micron range. It is also known in a sphere, such as argon, under agitation in a salt, that the hardness disperses in the hard metal, such as a tungsten molten bath, at 200 to 1200 ° C. This carbide increases with decreasing grain diameter. Reactants contain the essential EIe sintered bodies, which are made from the finest, previously available metal-like compounds and are produced in barren metal-like powders, so that each has a different essential element and has the disadvantage of poor impact strength in the metal-like compound to be produced sensitive to heat shocks to 20 holds. One works with such proportions of reactivity. These products completely lack the ductility, the atomic ratio of the essential components and no method has yet become known to overcome the brittleness problem of the elements in the separate reaction part. the same as the one in the desired metal

The invention relates to a process for the production of a similar compound, and at least one of finely divided carbides of boron or silicon, of 25 reactants is a compound in which silicon boride, borides, silicides or carbides the essential element has a positive valence. of titanium, zirconium, hafnium, vanadium, niobium, the reducing conditions are made by the tantalum, chromium, molybdenum or tungsten with a presence of that amount of an alkali or earth particle size of 1 to 250 millimicrons, the alkali metals obtained thereby, the stoichiometrically necessary is characterized in that one is the reactants 30, in order to reduce the element having a positive valence of which at least one contains the essential element ment to the zero valued state, ie to the elein of a positive valency level, in the mental state. A chemically desired quantity ratio occurs in a molten salt reaction with the formation of the divided metal bath at 200 to 1200 ⁰ C in the presence of an alkali-like compound, and heating is continued in this way or alkaline earth metal as a reducing agent for a long time until the particles of the metal-like inert atmosphere during such a period of time will flocculate compound. These flocculated particles converts that the product flocculates, which are separated from the melt, e.g. B. filtered off. Reducing agent is used in an amount that it is sometimes advantageous to expose the particles to an element with the positive valence up to an oxygen-containing environment, from which speed is reduced to zero, and that they then absorb oxygen until the oxygen content in separating the flocculated product from the salt bath. is in the above range.

The particles obtained have a spread - Da is the size of the minute particles in the area

coefficient of diffraction of the X-ray diffraction line, K ', of, in which they show colloidal activity,

9 · 10 ~ ^a to 3.6 · 10 ~ ⁴ , which from the equation have the new, according to the invention produced pro-

o / f 45 product properties that are essential and not particularly

g, __ p cos (y in a predictable way from the properties of the

λ speaking massive metal-like compounds

differ. So you can compact the powder and

is calculated, where β is the pure angular width in sinter, and the sintered products resist radians of a powder reflection, which on 50 a grain growth at high temperatures and due to the method of determination used have impact strength values that are free from any broadening, λ the wavelength in the properties of the previously available metal-like Angstrom of monochromatic CuK «X-ray compounds cannot be predicted,
ment and 2Θ is equal to the deflection angle of the The new process products are finely divided diffracted beam. 55 species, that is, they are made up of tiny particles from 1 to

The present invention makes it possible for the first time to form 250 millimicrons of average size,

the metal-like compounds mentioned in the form of very small particles are the finest particles

obtained from powders in which the smallest, degree of distribution. They can of course be aggregated

discrete particles can range in size from 1 to, but the aggregates are loosely bound and let go

250 millimicrons. Easily redisperse in the new products 60. The products can

are particulate metal-like compounds in the form of fine powders, in which the smallest

from the carbides of boron and silicon, particles only due to surface forces.

Silicon borides or the borides, silicides and Car- are held, or in the form of dispersions in

from titanium, zirconium, hafnium, vanadium, niobium, aqueous or organic liquids

Tantalum, chromium, molybdenum or tungsten are formed 65. For example, the particles can be in water

will. or organic liquids, such as lower alcohol

In certain embodiments of the invention, e.g. B. methanol, ethanol, propanol, butanol, or

lies in the products of chemically bound acid glycols or glycol derivatives such as ethylene glycol

or diethylene glycol monoethyl ether and glycol monoethyl ether.

The minute particles have an average size in the range of 1 to 250 millimicrons, preferably 10 to 200 millimicrons, especially 10 to 100 millimicrons. The size mentioned is an average dimension, but usually all three dimensions of the particles present here are about the same, so that for practical purposes the Dimension can address as the diameter of a spherical particle.

Preferably, the production of particles with a size of 10 to 200 millimicrons is carried out at 400 to HOO ⁰ C with agitation of the molten salt bath and the concentration of the essential elements in the molten salt bath is kept at least 100 times the concentration due to the solubility product of the compound to be prepared necessary is.

The reactants of the salt bath melt are preferably during the course of the reaction added continuously or in periodic, stoichiometric equivalent proportions.

The size of the very small particles can be determined by any method known to the person skilled in the art. The determination can be made directly on electron micrographs. The grain size can also can be calculated from the nitrogen adsorption (cf. P. H. Emmett, “A New Method for Measuring the Surface Area of Finely Divided Materials and for Determining the Size of the Particles "in" Symposium on New Methods for Particle Size Determination and the Subsieve Range ", Washington Spring Meeting der A. S. T. M., March 4, 1941).

The surface area of the particles in m ² / g, A, is related to the average diameter D (in millimicrons) according to the equation

D =

6000 πιμ
Qa

in which ρ means the density of the metal-like compound when the particles are approximately spherical Have shape, or according to the equation

D =

4000
Qa

when the particles are in fibrous form.

The metal-like compounds produced according to the invention are microcrystalline and can be easily identify by an X-ray analysis of the powder. A given metal-like compound is made by comparing the measured “g?” value identified with the "^" literature value of this compound in macrocrystalline form. The diffraction diagram enables this to be carried out Identification, but the inflection lines of the new products give way in both width and width relative intensity depends significantly on that which is found in the corresponding macrocrystalline substances receives. The reason for this is in the extraordinary The fineness of the fabrics as well as the presence of lattice defects can be seen. The nature and distribution of lattice disturbances are closely related to the amount of oxygen in the compounds and the way in which the oxygen is assigned to the lattice in the microcrystalline substances.

The pure width of a diffraction line can easily be determined by methods such as those described in detail at Standard tests such as the "X-ray Diffraction Procedures" by Klug and Alexander, John Wiley and Sons, Inc. (1956). Using this size, according to the invention manufactured products by the equation

K ' =

β cos Θ

describe. Here, β denotes the pure angular width (in microns) of a powder reflection, which is free of any broadening due to the method of determination used, λ the wavelength of the X-ray radiation in angstroms and 20 the deflection angle of the diffracted beam.

K ', the line broadening coefficient, is a function that is characteristic of the new products and the nature of the radiation used. Thus, for CuKa radiation made monochromatic, the range of permissible values is from K ' 9 ^{· 10 ~ 2} to 3.6 · 10 ~ ⁴ . Similarly, for ΜοΚα radiation made monochromatic, the range of permissible values from K ' 1.84 · ΙΟ " ¹ to 7.35 · ΙΟ" ⁴ . The metal-like compounds obtainable according to the invention exist in a variety of crystalline forms and in many cases various stoichiometric compositions. For example, silicon carbide is obtained as -form in which it has a hexagonal shape or rhombohedral cell structure, and also as / 5-shape of face-centered cubic lattice arrangement. As is known, the α-form itself exists in at least twelve crystalline forms, which differ only in the arrangement and the number of layers in the cell unit.

The following table lists known forms of metal-like connections, which can be produced in a modified form according to the present invention.

Boron carbide
Silicon carbide
Titanium carbide
Zirconium carbide
Hafnium carbide
Vanadium carbide
Niobium carbide

Tantalum carbide
Chromium carbide

Molybdenum carbide
Tungsten carbide

Table I.

Carbides

Well-known composition
B ₄ C; B ₆ C
SiC *)
TiC
ZrC
HfC

VC; V ₂ C; V ₄ C ₃ ; VC ₂
NbC; Nb ₂ C
TaC; Ta ₂ C *)

Cr ₂₃ C ₈ ; Cr ₇ C ₃ ; Cr ₃ C ₂ ; CrC;
Cr ₅ C ₂ ; Cr ₄ C

Mo ₂ C; MoC *)
W ₂ C *); WC

*) In these cases two or more crystalline forms are reported been.

Table II Boride Known compositions Silicon boride SiB ₃ ; SiB ₆ Titanium boride Ti ₂ B; TiB; TiB ₂ ; Ti ₂ B ₅ Zirconium boride ZrB; Zr ₃ B ₄ ; ZrB ₂ ; ZrB ₄ ; ZrB ₁₂ Hafnium boride HfB; HfB ₂ Vanadium boride V ₂ B; VB; V ₃ B ₄ ; VB ₂ ; V ₂ B ₅ ; VB ₃ Niobium boride Nb ₃ B; Nb ₂ B; NbB; Nb ₃ B ₄ ; NbB ₂ Tantalum boride Ta ₃ B; Ta ₂ B; Tab; Ta ₃ B ₄ ; TaB ₂ Chromium boride Cr ₄ B; Cr ₂ B; Cr ₅ B ₃ ; Cr ₃ B ₂ ; CrB; Cr ₃ B ₄ ; CrB ₂ ; Cr ₂ B ₅ Molybdenum boride Mo ₂ B; Mo ₃ B ₂ ; Mob*); Mo ₃ B ₄ ; MoB ₂ ; Mon ₂ B ₅ *) Tungsten boride W ₂ B; WB *); WB ₂ ; W ₂ B ₅ *) In these cases ti are two or more crystalline forms b been judged. Table III Silicides Known compositions Titanium silicide Ti ₂ Si; Ti ₅ Si ₃ ; TiSi; Ti ₂ Si ₃ ; TiSi ₂ Zircon silicide Zr ₄ Si; Zr ₂ Si; Zr ₅ Si ₃ ; Zr ₃ Si ₂ ; Zr ₄ Si ₃ ; Zr ₆ Si ₅ ; ZrSi; ZrSi ₂ Hafnium silicide HfSi; HfSi ₂ Vanadium silicide V ₃ Si; V ₂ Si; V ₅ Si ₃ ; V ₃ Si ₂ ; VSi ₂ Niobium silicide Nb ₄ Si; Nb ₂ Si *); Nb ₅ Si ₃ ; Nb ₃ Si ₂ ; NbSi ₂ Tantalum silicide Ta ₅ Si; Ta ₂ Si; Ta ₅ Si ₂ ; Ta ₅ Si ₃ ; Ta ₃ Si ₂ ; TaSi ₂ Chromium silicide Cr ₃ Si; Cr ₂ Si; Cr ₅ Si ₃ ; Cr ₃ Si ₂ ; CrSi; Cr ₂ Si ₃ ; CrSi ₂ ; Cr ₂ Si ₇ Molybdenum silicide Mo ₃ Si; Mo ₅ Si ₃ ; Mo ₃ Si ₂ ; Mo ₂ Si ₃ ; MoSi ₂ Tungsten silicide W ₃ Si; W ₅ Si ₃ ; W ₃ Si ₂ ; W ₂ Si ₃ ; WSi ₂

The percentage of bound oxygen in the products according to this embodiment of the invention is generally in a range, the upper limit of which is 25% (based on the total weight of the composition) and its lower limit from the equation

18 D ² + 12D + 2

1.8 £> + 1.2)

*) In this case two crystalline forms have been reported.

The reactants are preferably used in stoichiometric proportions.

The invention also extends to mixtures of the various metal-like compounds mentioned above applicable. One can produce these mixtures directly by simultaneously using two or more metal-like Forms compounds in the molten salt bath, or by mixing two or more independently win mutually produced metal-like connections.

As already mentioned, the process according to the invention can be modified in such a way that the Exposing process products to an oxygen-containing environment; the oxygen content of the thus obtained Products is made according to ordinary analytical methods by analyzing the total product definitely.

expressed in%, is calculated, where D is the average grain size in millimicrons and ρ is the density of the metal-like compound in g / ml. The densities of the metal-like compounds are already known and are in the range from about 2 to 10. Thus, the lower limit for the oxygen content is generally 1.0% when ρ = 2 and D = 1. For ρ = 10 and D = 1 the oxygen content is 0.5%, for ρ = 2 and D = 200 it is 0.09 ° / ₀ and for ρ = 10 and D = 250 it is 0.015%.

A preferred grain size range of the particles of the metal-like compound is 10 to 200 millimicrons. Particles whose particle size is in this range, preferably have an oxygen content in the range of 30 / o D to 10%.

If the masses are in the form of brines, the concentration of the modified metal-like compound have very different values and up to 50 percent by volume mean. A solids content of the brine of at least 10% is often preferred. The solid content in the dispersed phase is at least 40 and preferably at least 50%, in other words it dense particles are preferred.

The percentage solids content in the dispersed phase is determined viscometrically (cf. M ο ο η e y, J. Colloid Sc, 6 [1951], pp. 162 to 170).

The modified metal-like compounds,

which are obtained by the process according to the invention are in general in their physical form isotropic, roughly spherical particles, but it is possible to use colloidal particles a variety of shapes such as acicular and plate-like particles.

The size of the microcrystalline products is determined by the reaction time and temperature and by the solubility of the reactants and products in the melt system. For a given product, the particulate size increases with time and temperature, but this effect is kept to a minimum in the case of those products that have poor melt solubility. In general, solubility is related to melting point, and for the same melting temperature, the size of the minute particles is an inverse function of the melting point of the product. For example, molybdenum disilicide has made at 880-900 ⁰ C, an average grain size of 100 to 125 millimicrons, while silicon carbide, which is made at the same temperature, has an average particle size of 10-12 millimicrons. In addition, increasing the temperature of the melt by 100 ^° C. doubles the average grain size in the case of molybdenum disilicide, but does not change the grain size of the silicon carbide significantly. The reaction time has a similar influence, namely in such a way that products with greater solubility in the melt have a tendency

I 7 8

¹ I show. with prolonged exposure to high temperature in participants in the bath is soluble. The nature and the

' \ your molten system to larger particles too degree of bath movement should be sufficient to the

^: ■ grow. The time and temperature conditions, the reactants so quickly, essentially the same.

■ ί to achieve a desired average to disperse moderately in the bath when their addition is done.

^: Grain size required are therefore inherent in nature 5 Such a dispersion is naturally facilitated,

■ of the product dependent, as well as in the following by keeping the reactants continuously

; Examples further described. or in small proportions and in the stoichiometric

A growth of the particles in the melt is added to the ratio.

! kept to a minimum by maintaining a strong over- According to a preferred embodiment of the invention

saturation of the reacting substances is maintained. This io training is at least one of the reactants in

'· Leads to the continuous production of fresh, soluble cores of the salt bath. The reaction rate

during the process and limited the growth speed, the decreasing particle size of the reac-

or the accumulation of microcrystallites, which are higher in participants, and the highest reaction

the earlier stage of the reaction. speed is achieved when both reaction parts

In preferred embodiments of the invention, they are molecularly dispersed; H. in solution

should be the concentration of the reaction participants.

drew on their essential elements, at least that of at least one of the reactants should 100 times the concentrations that are thermodynamically less stable than a product of the Be the solubility product of the metal-like reaction to be formed. So either the metal connection to be formed should are required. 20 similar compound or a metathetic reac- Specifically, it is desirable to make the speed with ionization product more thermally stable than one of the reaction softeners the respondents are added, so be a participant. With what type and variety of to direct that in the melt the above supersaturation reactants one can work, arises on the reacting essential elements of the metal from the following examples.

similar connections are maintained. 25 Alkali or earth leaves are used as reducing agents can be conveniently realized by using the reactive alkali metals. The metal can thus, for. B. tion participants with a sufficiently high initial sodium, potassium, lithium, calcium, or barium concentration mixes and this concentration can be strontium, with sodium or calcium predominating of the proceedings. To be oversaturated.

degree of melting of the melt at a given point in time 30 In the method according to the invention

can be easily determined by taking a sample. Conversions carried out at very high temperatures.

and the concentration of the essential elements in men will be. In certain preferred embodiments

one can theoretically conclude that the

analytical chemistry. Elements of the metal-like connection in the

The maintenance of supersaturation in the reaction mixture in a nascent, highly reactive

Melt will be formed at higher temperatures and also in a form capable of movement. The reaction tem-

important in the lower-melting products, temperature is in the range from 200 to 1200 ⁰ C. It

so that a growth of the particles to a minimum works preferably in the range from 400 to 1100 ° C,

brought and the emergence of a wide grain size - in particular 600 to 1000 ° C.

area is avoided in the end product. 40 With the addition of the reactants and the For some uses of the reducing agent according to the invention, be it continuously or in small amounts Custom made products can, however, take a targeted approach, it is important to use the stoichiometric proportions Particle size distribution can be advantageous. The invention of the elements in the desired product so precisely Proper procedures can be followed by careful steering as possible. The way in which The above-mentioned reaction variables how this is easily achieved is described in detail in the explanatory notes customize such products. tion serving examples. Are correct The salt of the molten salt can be a single salt or those stoichiometric proportions of the reaction Be salt mixture. In general, you can talk to any participant who will explain the essential elements in the working with salts, which are at the same atomic ratio at the same temperature as in the desired meder Do not decompose reaction. Molten halides 50 give a tall-like compound. The right stoichiowden preferred, as it is desirable, in the reactive portion of the metallic reducing agent tion system to maintain a reducing environment is that part that is responsible for transforming the one receive. The essential elements having a positive valence are particularly preferred Alkali or alkaline earth metals and eutectics form in the reacting compound (s) end mixtures of these salts. At temperatures above 55 it becomes an elementary one with the valence zero halfway through 600 ° C are lithium chloride, sodium chloride and form is required. Of course you can Calcium chloride works best, and between 300 parts of the desired compound even without one and 600 ° C you can form such stoichiometric steering with mixtures of aluminum, but that chloride work with lithium or sodium chloride. The product then contains impurities.

In order to stimulate the reaction, the reaction compounds are dispersed in the molten salt bath with movement in the molten salt bath. The dispersion can be of a molecular nature, allowing values to grow as high as possible, but in practice, as in an actual solution of the reaction part, a value of 30 ° / _{0 is} rarely exceeded,
In order to prevent excessive oxidation, the reaction in an inert atmosphere, such as helium, should form carbides. The dispersion can be carried out particles or argon, from which have acids, the size of which exceeds the colloidal area even by passing the gas over to 700 to 800 ° C, especially when the other reaction-heated titanium sponge has been removed.

9 ίο

Of 15O ⁰ C is important flowable and using herkömmli material, the apparatus for the judgments Verwen- rather Glasfrittefilter filterable with respect to the purity of the product. With regard to the dung that comes into contact with the melt, the tendency of the ammonium chloride to sublimate. The corrosion problems become increasingly necessary, however, to work with pressure filters. If a salt-free product does not suffer from the mechanical strength of the material under anhydrous conditions, the corrosion products contaminate the melt well and without the influence of the atmosphere, one can do this from the settled and accordingly the product. The most satisfactory in terms of layer or filter cake using a volatile molten salt such as titanium materials in terms of corrosion resistance are the non-metallic materials such as io tetrachloride, phosphorus trichloride, stannous chloride, bis-graphite, impermeable alumina and zirconium mother tetrachloride , Aluminum chloride or molybdenum dioxide, and silicon pentachloride bound with silicon nitride, residual salts of low volatility from carbide. In spite of the fact that these materials are washed and finally the volatile solvent used, they are relatively difficult to distil from the metal-like compound.
Let it be done that their mechanical strength is not good and that in most cases they are sensitive to heat or filtered residue, also from salt impacts. These shortcomings will be remedied by taking the salt from the solidified a careful construction of apparatus to a product using anhydrous solvents, minimum brought. such as methanol or ethylene glycol, extracted. For this

At the highest temperatures used, make 20 is repeated with the extracted solvent

most metals and alloys in terms of slurried and the desired product through

Corrosion and strength properties no longer gained by filtration or centrifugation.

satisfied, and above 1000 ⁰ C become non-metal ^ The metal-like compound is indeed of the

see materials preferred. Refractory metals in the salt bath melt at this point in a

or alloys flocculated with ceramics or others, d. H. loosely aggregated state separated,

ren non-metallic materials by flame spraying is not as strongly aggregated to a renewed

or are coated by sintering, are particularly well suited to provide dispersion resistance. The product is

For the implementation of the invention at the higher it is rather so loosely agglomerated that it is easily under

Temperatures. Below 1000 ° C in most cases suspensions or brines are formed in liquids

Cases of high temperature-resistant alloys, such as alloy media can be peptized,

of 61 ° / o Ni, 26 to 30 ° / ₀ Mo, 4 to 7 ° / ₀ Fe and The metal-like compound can be used in the

up to 0.12% C; or from 51% Ni, 15.5 to 17.5 ° / ₀ go according to the invention after its formation a

Cr, 16 to 18% Mo, 4 to 5% W, 4 to 7% Fe and to oxygenated environments. This

0.15% C; or from 19 to 21% Cr, 14 to 16% W, exposure to such an atmosphere can be a part

9 to 11% Ni, maximum 2% Fe. form a maximum of 0.15% C, 35 of the stage in which the product of the

Remainder Co; or from 80% Ni, 13% Cr and 7% Fe, to salt bath melt. e.g. by a

pacifying. aqueous extraction. Water is called oxygenated

During the reaction, the surrounding metal-like connection is considered, since the metal-like connection is initially formed in the form of extremely small, discrete end divisions due to its high and very reactive nature. As the reaction progresses and the surface is able to react with the water and the heating continues, these tiny particles with the oxygen contained therein are subject to formation of either the oxide or the hydrate oxide of the metal flocculation, forming particles in the molten salt. Heating is continued until this similar compound can combine.
Flocculation has reached a substantial level. This reaction with water is a surface. Such flocculation of the particles is naturally reactive and at such a pH value that it is not equivalent to the growth of massive crystals, since oxidation products are insoluble, rapidly slower, and the smallest particles in the flocculated product the surface of the metal-like connectors are still distinguishable. formation with oxides or oxide hydrates of the elements in

With the exception of boron carbide, the density of the metal-like compound is covered. Is carried difference between the metallähnJichen Verbindun- 50, the aqueous extraction at low Tempe Ragen and the molten salt phase of so doors, for example in the range from 0 to 10 ⁰ C by the flocculated particles of metal-like comparison to excessive attack on If preventing the metalloids from concentrating on binding at the bottom of the melt. The pH is stopped while stirring is stopped. This makes it possible to keep tion between about 4 and 10, the choice of a fraction rich in the metal-like compound 55 of the pH in a given case being dependent on the stability of the oxide formed by adding the upper layer of the salt. In the case of expires. The recovered salt can, if silicon carbide or molybdenum disilicide e.g. B. If one is desired, it can be used again. pH of 7 to 8 preferred, while at

On the other hand, most of the zirconium carbide can also be used, preferably with a pH of

Salt phase by filtration using 60 4 to 5 works. The aim of pH control is to

remove ceramic or metal frit filters. This on the surface of the particles of the metal-like

In the case of the high-melting salts, a stable oxide layer can be maintained

by creating a mixable lower melting point and in this way preventing further attack.

Salt or, preferably, a eutectic-forming dem.

Salt is added, which makes the filtration 65 During the initial stages of the extraction in at a considerably lower temperature allows the presence of relatively large amounts of salt under light. So are aluminum chloride-sodium chloride or are the particles of the metal-like compound Aluminum chloride-lithium chloride mixtures in the event of flocculation and the product easily pours off

11 12

separate from the solvent by filtration. pour and subsequent sintering. The lower ones With the removal of more salt, the product becomes sintering temperatures, at which solid materials are more difficult to disperse and can best be obtained through fusible articles, make a wide-spinning process at high speed gained advantage in using the new merging. The residues obtained in this way represent 5 settlements as binders are not completely free from traces of salt, but manufactured products can also be used as materials for comfortably easily dispersible by using one for the purposes of powder metallurgy. Colloid mill works and adjusts the pH value so that it can be hot-pressed, compressed under pressure that adequately stable dispersions are obtained and sinter or by flame techniques to be processed into new high-melt melts in order to produce bodies of any desired shape Can use fabrics. put. Such bodies are characterized by an un-

Such higher stability can be achieved by having high impact strength and resistance to soluble salts through dialysis or treatment with against heat shocks.
Ion exchangers, such as polystyrene resin ion exchange. -I ₁
the quaternary benzylammonium groups
have, or nucleus sulfonated polystyrene resin ions- This example describes the preparation of titanium exchangers more completely removed and then carbide using calcium carbide as the pH value of the sol so that the most stable carbonaceous reactant, titanium dioxide dispersion is obtained. Such sols are usually considered to be the titanium-containing reactant and metal-diluted, with the concentration of the dispersed calcium as the reducing agent,
metal-like compound has the order of magnitude of To carry out this reaction serves as 1 ° / ₀ or below. By carefully setting up a cylinder 10.2 cm in diameter to evaporate the solvent, the brine can be concentrated, and 27.9 cm high, from a 1.6 mm sheet metal to obtain stable brine, the concentration of which is from an 80 lies ° / ₀ Ni, 13 ° / o Cr, 7% Fe existing the desired range. 25 alloy is worked. The cylinder is

If the metal-like compound of the salt in a container made of an alloy of 65 ° / ₀ Fe, 20 ° / ₀ Cr, 15 ° / ₀ Ni, without the action of an oxygen-containing environment, is obtained from a wall, be it due to an extrac - has a thickness of 6.4 mm and is provided with a tion with anhydrous solvents or by flange, which is bolted with a tight-fitting filtration and washing with volatile salts, so can 30 head. Two connecting points are attached to the head, which are connected to the oxygen-containing environment. In which are exposed to retort-shaped connection to form an oxide coating on the particles of the metal-like tapered joints. Glass flasks can be used for this, and the solid powdery ones can be made by simply removing the particles with a reactant from these flasks containing oxygen or a humid atmosphere by bringing them together in the connection points in which the atmosphere contains water, allowing them to rotate so that the Powder into the reaction vessel the amount of oxygen or the oxygen-containing overflows. The apparatus is further provided with a stirrer component not exceeding the amount to be incorporated from a 12.7 mm tube of metal-like joint. Alloy of 80 ° / ₀ Ni, 13 ° / o Cr and 7 ° / ₀ Fs with Man further provides means to direct the temperature during such a 40 flat blades of an alloy of about 66 treatment because the reaction or 67% Ni, 28 to 34% Cu, remainder Fe, Mu, C, Si tion is produced exothermically with the metal-like connection, which are welded to the tube, and runs and you do not let them get too quickly into the reaction vessel via a bearing with asbestos should. After the particle of the metal-like packing is introduced. The temperature in the reac product with oxygen in the desired degree 45 tion device is converted by means of a thermocouple, the product is recorded against a further reaction introduced into the hollow stirrer shaft is relatively insensitive and can itself. The container is exposed to an electrically heated air without being surrounded by adverse result- furnace, the temperature of which occurs by means of an andenisse. ren thermocouple is recorded.

The new metal-like, inventively produced 50 The reaction device is watered with 500 parts

The products presented are loaded with valuable binders for serfree calcium chloride; the air in the

refractory bodies. They can be proportionately planted by introducing argon beforehand

moderately coarse powders of other difficult to melt over finely divided titanium metal at 800 ° C of disruptive

Incorporate masses and thereby products with very much the gases have been released into the reaction process

achieve improved properties. Many difficult directions, with the gas outlet at one

fusible substances that is also attached to a very desirable wash bottle. With good movement

Have high temperature resistance, have a mechanical stirrer will make the calcium

insufficient mechanical strength and resistance chloride melted and the melt reduced to 875 ° C

against intermittent thermal and mechanical loads. brings.

These deficiencies are associated with a poor bond in 5 minute intervals between the particles of the refractory material by appropriate handling of the additional rial and the difficulty in obtaining flasks with aliquots of the mixed reac compositions, their density tion participant, consisting of 16 parts of colloidal the theoretical value for the material forming them titanium dioxide powder, 8 parts of calcium carbide des Hannahert. The fine particles of the mass according to the 65 dels (80% CaC ₂ ) and 12 parts calcium, charged, invention allow a great deal to be achieved, while the additional speed is guided by the better bonding and higher densities on the conventional heat generation generated by the Thermocouple borrowed ways as recorded by dry pressing or sliding in the stirrer. The temperature will

maintained in the range from 875 to 925 ^° C. during the reaction, the addition being completed in the course of 80 minutes and a total of 240 parts of titanium dioxide, 120 parts of commercially available calcium carbide and 180 parts of calcium being added. The melt is held at 875 to 900 ° C. with stirring for a further hour. The salt is then allowed to cool to room temperature under argon after the stirrer has been withdrawn from the melt. The solidified salt cake is broken up and pulverized.

The crushed salt cake is stirred with ice water, the calcium oxide by-product is created by adding glacial acetic acid dissolved and the pH is finally adjusted to 8.0. One wins the insoluble one Spin residue and repeat washing process to remove soluble salts and calcium oxide with subsequent spinning three times, adding acetic acid to the Adjust the final pH value of each item to be washed to 7.0. The last items to be washed are free of chloride and calcium, and the residue, which consists of finely divided titanium carbide, is dried in a vacuum oven at 100 ° C.

The X-ray analysis using CuKa radiation made monochromatic gives a clear diagram with "d" values corresponding to TiC, and the line broadening coefficient K 'is calculated to be 9.4 · 10 " ^4. Measurements of the nitrogen surface area give a value of 16 m ² / g which corresponds to an average particle size of 75 millimicrons, calculated using the above relationship for surface particle size.

The emission spectrograph shows that the product contains small amounts of calcium, nickel, iron, and chromium Contains silicon as impurities.

Example 2

This example describes the manufacture of particulate silicon carbide, with calcium carbide as the carbonaceous reactant and colloidal silica as the siliconous one Reactant is used and the elements of the components by reduction with calcium metal be released.

A device similar to that in Example 1 is used to carry out the reaction.

The reaction device is charged with 1000 parts of anhydrous calcium chloride, 120 parts of powdered colloidal silica are placed in one of the flasks, and the other flask is charged with a mixture of 120 parts of calcium pellets with 80 parts of commercial calcium carbide (80% CaC ₂ ), which is crushed to a particle size where it will pass through a 20 mesh (0.84 mm) sieve. The air in the system is displaced into the reaction device by introducing argon, which has previously been freed from reactive gases over finely divided titanium metal at 800 ° C., the gas outlet being connected to a washing bottle. The calcium chloride is melted with good agitation by means of the mechanical stirrer and the melt is brought to 900 ° C.

The reactants are introduced into the reaction device by means of the auxiliary flasks in equal aliquots, the addition being made alternately and the rate of addition being controlled with regard to the heat development, which is indicated by a thermocouple in the melt. By this procedure, one can remain close to the stoichiometric reaction ratios for the reduction of the silicon dioxide and the conversion to silicon carbide. The temperature is maintained during the reaction in the range of 900 to 950 ° C, wherein the additive in the course of 1 ¹ J ₄ hours is completed, and during the process an argon atmosphere

ίο is maintained. Keeping the melt further 1V ₂ hours with stirring to 940 to 950 ° C and then pulls stirrer and thermocouple to a height above the melt is allowed to cool under argon to room temperature. The solidified salt cake is then broken up and pulverized.

The crushed salt cake is treated with a 20% solution of acetic acid in methanol under argon Stirred at 0 ° C and spun to recover the insoluble material. After two extractions with methanolic acetic acid and two extractions using methanol is the supernatant Well free of chloride.

The residue, which consists of particulate silicon carbide, is placed in a vacuum furnace dried.

The X-ray analysis using CuKa radiation made monochromatic shows that the product is mainly formed by ^ -silicon carbide, and K 'is calculated to be 1.1 · ΙΟ " ^2. The surface area determined by the nitrogen ^{adsorption method gives a value of 180 m a} / g, which corresponds to an average particle size of 10.5 millimicrons, calculated from the above relationship for the surface particle size.

The emission spectrograph shows that the product contains less than 0.1% iron, chromium and nickel. The analysis values for silicon, carbon and oxygen match a mixture of 70% silicon carbide and 25 ° / ₀ silica with those.

Example 1 3

Following the procedure of Example 2 280 parts by weight of boron oxide with 450 parts of calcium and 67 parts of calcium carbide are (/ ₀ CaG ₂ 96 °) is reacted in the course of 2 hours at 780 to 83O ⁰ C in a melt consisting of 1000 parts of calcium chloride, whereupon the mixture is stirred at 780 to 800 ° C. for 30 minutes.

The product is recovered from the salt cake by following the procedure of Example 2 using methanolic acetic acid, followed by extraction with methanol to remove the soluble salts. The dry product is a black powder with a surface area, determined by nitrogen adsorption, of 42 m ² / g, which corresponds to a grain size of 75 millimicrons. is equivalent to. The X-ray diagram shows that the main crystalline phase present is B ₄ C at a value of K ' CuKa = 1.2 · ΙΟ ^-3 .

B e i s ρ i e 1 4

Following the procedure of Example 2, 123 parts by weight of powdered colloidal zirconium dioxide with 120 parts of calcium and 80 parts of commercial calcium carbide (80% CaC ₂ ) are reacted in a melt containing 1000 parts of calcium chloride at 1050 to HOO ^{0 C.} crushed by passing through a 20-mesh (0.84 mm) sieve.

The salt cake is extracted with methanolic

15 16

Acetic acid and methanol to remove soluble salts in an amount of 0.5 to 1%. The surface, remove, and recover a black powder. This is true by nitrogen adsorption, is found to be material gives a clear X-ray diagram of 8.5 m ² / g, when calculated using the zirconium having a value of K CuKa = 6 x 10 ~. ⁴ average density of a mixture consisting of the main metallic impurities 5 35% Mo ₂ C and 65 MoC, an average, as the electron spectrograph shows, iron, giving a grain size of 85 millimicrons. Chrome and nickel. The electron micrographs

show that the average particle size under Example 8

half a millimicron.

ίο Following the procedure in example 2, in

Example 5 of a melt containing 1500 parts of calcium chloride,

at 950 to 1000 ⁰ C 450 parts by weight of colloidal

Following the procedure of Example 2, in chromium (III) oxide with 160 parts of calcium carbide, a melt containing 750 parts of a eutectic trade (80% CaC ₂ ) and 160 parts of calcium mixed from lithium chloride and potassium chloride is released. The container according to the device is maintained at 650 to 700 ^° C. over the course of I ¹ J ₂ hours. Example 2 through a container made of impermeable 150 parts by weight of colloidal vanadium trioxide with 92 parts of graphite of 10.2 cm diameter, 30.5 cm Height and len sodium and 70 parts of sodium carbide implemented, 6.4 mm wall thickness replaced. The lower, in the melt, the melt is followed for an additional hour at 650 immersed portion of the stirrer is stirred for from one to 700 ⁰ C. 20 graphite tube 2.54 cm in diameter worked and

As in Example 1, the salt cake is extracted and provided with flat graphite scoops, and won the product. The product is obtained by using metha-

The X-ray diagram of the product corresponds to nolian acetic acid as in Example 2 up to the chloride crystallites of submicron size of the VC extracted with a freedom and finally in a vacuum furnace value of K ' CuKa = 3.2 · ΙΟ ^-3 . 25 dries to target the particles of the product

to give the oxygen content. The X-ray analysis

Example 6 does not give a clean diagram, although it does

present main phase is Cr ₃ C ₂ . The product

Repeating the procedure of Example 5 appears to be a mixture of several carbides, colloidal using 250 parts by weight 30 The calculated for different diffraction lines of niobium dioxide in place of 150 parts Vanadinchlorid and values of TTCuKa range from 4.9 x 10- ⁴ to 6, l · ΙΟ " ⁴ , of 46 parts of sodium instead of 92 parts of sodium
and isolate the product as above. Example 9

Through chemical analysis and X-ray analysis it becomes

the product identified as NbC, oxygen content 35 After the procedure of Example 2, the 1.5% content of metallic impurities in less than 3 hours 450 parts by weight of colloidal less than 1% and K ' CuKa = 1.5 · IO- ³ . Tungsten trioxide with 80 parts calcium carbide (80%

CaC ₂ ) and 200 parts of calcium implemented, the

Example 7 Melted reactants to 1000 parts

40 calcium chloride from 1000 to 1040 ⁰ C added. The reaction device is charged with a.

Mixture of 1000 parts by weight of sodium chloride and To obtain the product, methanol is

225 parts of molybdenum dichloride and displaced the air shear acetic acid extracted until it was free of chloride by introducing argon, which was previously finely crushed and dried.

split titanium metal at 800 ⁰ C of reactive gases 45 The gray "powder obtained provides a clear liberated, in the reaction device. An X-ray diagram for tungsten carbide at K ' CuKa melts the salts and brings the melt under good = 3.4 · 10 ~ ^3. The analysis shows 92% tungsten carbide agitation by stirring to 850 ^° C. The melt and an oxygen content of 1.6% are made according to the procedure of Example 1 in the course

one hour slowly a mixture of 50 parts by weight 50 B e i s ρ i e 1 10

len sodium carbide and 65 parts sodium added,

the temperature being in the range from 850 to 900 ° C. This example explains the production of oxide

t is held. If the addition of Reaktionsteil-, particulate form containing aufweisendem titanium boride according to participants complete, the melt is further one embodiment of the method according to the ι is stirred for 30 minutes at 850 to 88O ⁰ C. 55 Invention. It becomes that described in Example 1

The crushed salt cake is used under argon with a reaction device.

Ethylene glycol slurried to by-product

To remove sodium chloride formed, and centrifuged to separate 1000 parts by weight of lithium chloride and remove the insoluble material. After 360 parts by weight of titanium dichloride and displaced the four extractions, the supernatant ethylene glycol is 60 air by passing in argon, which was previously ^a chloride-free. The residue is washed with anhydrous divided titanium metal at 800 ° C from reactive gases ether and has been freed in a vacuum oven at 80, in the reaction device. Dried below ^s up to 90 ° C. good agitation by stirring the salts

X-ray analysis reveals the presence of both melted and the melt brought to 650 ° C. The Mo ₂ C as well as MoC and a K ' CuKa = 9.3 · ΙΟ " ^4. 65 melt are continuously for 70 minutes ^s The oxygen content is 1.8%, and the metallic sodium and sodium borohydride are impurities with speed Emissionsspektro- speeds of 1 part or 1.6 part / min, fed WO ^r determined chromatography, mainly chromium and nickel · at the temperature in the range of 650 to 670 ° C

is held. When the addition of the reactants is complete, the melt is ^{stirred at 640 to 660 °} C. for a further 30 minutes. The outflowing gases, argon and hydrogen, carry a fine black powder with them, which is removed in ethylene glycol washing bottles.

After completion of the reaction, the stirrer and the thermocouple are at a height above the melt is drawn, which is then allowed to cool to room temperature, by introducing argon an inert atmosphere is maintained in the head of the reaction apparatus. The one on this Well-formed, solidified salt cake is broken up and pulverized.

The crushed salt cake is slurried with ethylene glycol under argon and used for recovery of the insoluble material. After four extractions the supernatant is ethylene glycol chloride free; the residue is washed with anhydrous ether.

The finely divided titanium boride is dried in a vacuum oven, the partial pressure of the present Oxygen is only sufficient to produce the subsequent degree of oxidation of the product.

X-ray analysis shows that the product is mainly titanium boride, TiB ₂ , at K ' CuKa = 2.1 x 10 " ^3. Surface area determination by nitrogen adsorption gives an average grain size of 30 millimicrons calculated from the above relationship for surface particle size .

The emission spectrography shows that the product contains less than 1.0 ° / ₀ of metallic impurities, and these impurities are mainly iron, chromium and nickel contents of the alloy. The oxygen content is determined as 1.5 ° / _0, which corresponds to a titanium dioxide content of 3.8 ° / _0th

The black suspension obtained from the glycol washers is spun; the residue will washed with ethylene glycol until no more chloride can be found in the extraction solvent. The end product is washed with anhydrous ether and dried. It is mainly made from titanium boride a titanium oxide content of 5.4%. The yield of product from this source is 10% Total titanium boride yield.

The excess glycol scrubber product in the centrifuge contains 0.8% suspended Titanium boride in the form of a stable black sol. This sol is by vacuum evaporation on a Brought solids content of 11.5%, and the average particle size of the dispersed titanium boride results, estimated from electron micrographs, to about 20 millimicrons. The dispersed Particles are in the form of dense, essentially spherical, and largely non-aggregated Particle.

Example 11

This example illustrates the preparation of oxide-containing zirconium boride from solid reactants according to an embodiment of the invention. The reaction device used is that described in Example 2 is described.

The reaction device is charged with 1000 parts of anhydrous calcium chloride, 250 parts of powdered colloidal zirconium dioxide in one of the auxiliary flasks, and a mixture of 400 parts of calcium pellets and 200 parts of calcium tetraborate crushed to a size where a 20-mesh sieve (0 , 84 mm) happens in the other additional flask. The air in the system was replaced by introducing into the reaction apparatus argon, which has been freed beforehand about finely divided titanium metal at 800 ⁰ C of relative gases, wherein the gas outlet is connected to a washing device. With good agitation by means of the stirrer is melted ίο the calcium chloride and the melt brought to 900 ⁰ C.

With the aid of the additional flasks, the reaction participants are entered into the reaction device in small aliquots, the addition being made alternately and the additional speed being controlled on the basis of the heat generated, which is indicated by the thermocouple in the reaction device. This procedure allows one to stay close to the stoichiometric reactant proportions which are necessary for the reduction of the zirconium dioxide and the conversion to zirconium boride. The temperature is kept in the range from 870 to 910 ^° C. during the reaction, the addition being completed in the course of 3 hours and an argon atmosphere being maintained during the reaction. The melt is kept with stirring for a further 1V ₂ hours at 870 to 910 ^° C. and then the stirrer and the thermocouple are pulled to a height above the melt, which is allowed to cool to room temperature under argon. The solidified salt cake obtained in this way is broken up and pulverized.

The crushed salt cake is mixed with a 20% solution of acetic acid in methanol under argon stirred at 0 ° C and centrifuged to recover the insoluble material. After two extractions with methanolic acetic acid and two extractions using methanol is the supernatant Well chloride-free, and the residue is dried in a vacuum oven, the partial pressure of the Oxygen in the furnace atmosphere is only sufficient to achieve the desired oxygen content of the product result.

The X-ray diagram corresponds to the zirconium boride, ZrB ₂ , with K ' CuKoc = 8.5 · 10- ". The analysis values for zirconium, boron and oxygen correspond to those of a mixture of 94% zirconium boride and 3% zirconium dioxide. The emission spectrograph shows that the product contains less than 1% iron, chromium, nickel and calcium.

The last methanol wash contains 1.5% product in the form of a stable dispersion, which is concentrated to a solids content of 17%. Electron micrographs of the resulting stable sol indicate that the dispersed particles are dense, largely non-aggregated, substantially spherical particles with an average grain size of 20 to 35 millimicrons. The solids content in the disperse phase is 80%.
60

Example 12

The reaction system described in Example 2 is used except that only one the feed piston is used. The method of operation corresponds to example 10. In the course of a Hour are a melt, which consists of 700 parts of lithium chloride and 330 parts of niobium dichloride, 80 parts by weight of sodium borohydride and 50 parts of sodium

trium added. The temperature during the addition is in the range from 600 to 630 ° C, and the bath is after the addition of the sodium borohydride for a further hour with stirring at this temperature held. The product is obtained from the salt cake as in Example 10.

The X-ray diagram corresponds to the niobium boride, NbB, at K ' CuKa = 7.2 · 10 " ^3. The analysis values for niobium, boron and oxygen correspond to a mixture of 94% niobium boride and 3.5% niobium oxide. The emission spectrograph shows that the product contains less than 0.5% iron, chromium, nickel and calcium.

Example 13

After the procedure of Example 10 are in a melt consisting of 1000 parts of calcium chloride consists, at 950 to 1000 ° C 245 parts by weight of vanadium dichloride with 120 parts of calcium and 62 parts Calcium boride implemented.

The solidified salt cake is broken up, pulverized and ^{slurried with 3% hydrochloric acid at 0 °} C., working in an argon atmosphere. The resulting suspension is filtered using a medium fritted glass filter. The residue is washed again with 3% hydrochloric acid and then extracted three more times with water. After the first aqueous extraction, part of the product is in the form of a stable aqueous dispersion which is centrifuged to recover the product.

The supernatant material from the last two extractions is made up of dilute brines. The excess material from the last spin has a pH of 6.5 and a solids content of 0.8%. Electron micrographs show that the dispersed material is in the form of essentially spherical, non-aggregated particles ranging in size from 20 to 300 millimicrons. The sol is concentrated to a solids content of 20%. The pH is 9.5.

A sample of the dried solids from the sol gives a good X-ray diagram for vanadium boride, CE ₂ . The solids content in the dispersed phase is 70%.

The centrifugal residue, which is obtained from the salt cake in the manner described above after repeated Wash obtained is dried in a vacuum oven and consists of 87% vanadium boride and 10.5% vanadium oxide.

Example 14

Following the procedure of Example 11, in a melt containing 1000 parts of calcium chloride, at 1000 to 1050 ° C 200 parts by weight of calcium tetraborate with 400 parts of calcium molybdate and 500 parts of calcium reacted, the addition of the reactants taking place over the course of 3 hours.

The product is obtained from the salt cake by extracting with methanolic acetic acid as in Example 11 and drying in a vacuum oven. The X-ray analysis shows that the main component is B-MoB, with one or more of the higher borides of molybdenum also being present. The oxygen content of 3.5% corresponds to the presence of 10.5% higher value molybdenum oxide. K ' CuKa is calculated to be 1.4 · 10 ^-3 to 2.2 · " ³ for various lines. Determination of the surface by nitrogen adsorption gives an average size of the smallest particles below 50 millimicrons.

Example 15

Using the apparatus and procedure of Example 8, one of 1500 parts Calcium chloride existing melt at 1000 to 1050 ° C with 305 parts by weight of colloidal chromium oxide 140 parts of boron oxide and 480 parts of calcium reacted.

The product is obtained by extraction with methanolic acetic acid and finally dried in a vacuum oven. Analytically it gives 93% chromium boride, composition CrB _li42 . X-ray analysis does not give a pure diagram and the product appears to be a mixture of several chromium borides. The range of K ' CuKa for various lines is calculated to be 4.2x10 " ⁴ to ^{6.4x10" 4} .

Example 16

Following the procedure of Example 11, 450 parts by weight of colloidal tungsten trioxide are reacted with 100 parts of calcium boride and 200 parts of calcium in 1000 parts of molten calcium chloride in the course of 3 hours at 1050 to HOO ^{0 C.}

To obtain the product, it is extracted with methanolic acetic acid until it is free of chloride and dried. The X-ray diagram resulting W ₂ B ₅ as the main component at K 'CuKa = 3.9 x 10 ^"4 ± 0.5 × 10. ⁴ The chemical analysis shows 95% W ₂ B _4I5, indicating the presence of lower borides, and the oxygen content is 1.2% The emission spectrograph shows the upper limit for metallic impurities, mainly chromium and nickel, to be 0.5%.

Example 17

This example illustrates the preparation of an oxide-containing, particulate titanium silicide according to one embodiment of the invention. It becomes the reaction apparatus used in Example 1 used.

The reaction device is charged with a mixture consisting of 700 parts by weight of calcium chloride and 480 parts by weight of titanium dichloride, and the air is displaced through the reaction device by passing argon, which has previously been freed from reactive gases over finely divided titanium metal at 800 ° C. With good agitation by the stirrer, the salts are melted and the melt at 83O ⁰ C. The melt is in the course of 2 ¹ I ₂ hours slowly added to a mixture of 240 parts by weight of colloidal silica and 580 parts of calcium. The temperature of the melt increases to 890 ⁰ C and is maintained during the reaction, 850-890 ° C.

After stirring the melt for a further 30 minutes at 850 to 870 ^° C., the stirrer and the thermocouple are pulled to a height above the melt and the melt is allowed to cool to room temperature, an inert atmosphere being maintained by introducing argon into the head of the reaction device. The solidified salt cake thus obtained is broken up and pulverized.

The crushed salt cake is slurried with methanolic acetic acid, which takes place under argon, to prevent oxidation and centrifuged to recover the insoluble material. After four

Extractions, the supernatant methanol is chloride-free, and the residue is anhydrous Ether washed and dried in a vacuum oven, with the oxygen content of the oven atmosphere is only sufficient to give the desired oxide content of the product, which is described below.

On the basis of the X-ray analysis, the product is the titanium silicide, TiSi, and the average value of K ' CuKa is calculated to be 1.9 · 10 " ³ for various lines. The analysis values of the chemical analysis for titanium and silicon correspond to a composition with a content of TiSi _{1 # 1} of 94 ° / ₀ , indicating the presence of minor amounts of higher silicides The surface area measured by nitrogen adsorption gives an average particle size of about 35 millimicrons.

The emission spectrography shows that the product contains less than 1.0 ° / ₀ of metallic impurities, and these impurities are mainly iron, chromium and nickel. The oxygen content of the product is determined to be 1.25%, which corresponds to a titanium dioxide content of 3.1 ° / _0th

The material from the glycol extraction that protrudes during the spinning process contains 0.4% suspended titanium silicide in the form of a stable black sol. This sol is concentrated to a solids content of 16 ° / ₀ by evaporation in vacuo, and the average particle size of the dispersed titanium silicide, estimated from electron micrographs, is about 20 millimicrons. The dispersed particles are in the form of dense, substantially spherical and largely non-aggregated particles.

Example 18

This example illustrates the preparation of an oxide-containing, particulate titanium silicide according to the invention from solid reactants. It becomes the reaction apparatus described in Example 2 used.

The reaction apparatus is charged with 1000 parts of anhydrous calcium chloride, one of which is Additional flask with 160 parts powdery colloidal titanium dioxide and the other flask with a mixture of 80 parts calcium pellets with 192 parts calcium silicide cut to such a size is crushed so that it passes through a 20 mesh (0.84 mm) sieve. The air in the system is displaced by argon is introduced into the reaction device,

35

40

45 and maintains an argon atmosphere during the reaction. ^{The melt is kept at 950 to 1000 °} C. for a further hour with stirring, whereupon the stirrer and the thermocouple are pulled to a height above the melt, which is allowed to cool to room temperature under argon. The solidified salt cake thus obtained is broken up and pulverized.

The crushed salt cake is slurried with a 20 ° / ₀ solution of acetic acid in methanol at ⁰ ° C, operating under argon, to prevent oxidation, and spun for the recovery of the insoluble material. After two extractions with methanolic acetic acid and two extractions using methanol, the supernatant is chloride-free; the residue is dried in a vacuum oven.

X-ray analysis shows that the product is mainly titanium disilicide at K ' CuKct = 3.3 x 10 ^-3 . The surface area determined by nitrogen adsorption gives an average particle size of about 20 millimicrons, calculated from the above relationship for the surface particle size.

The emission spectrograph shows that the product contains less than 0.4% iron, chromium and nickel. The analysis values for titanium, silicon and oxygen are consistent with a mixture of 93.5 ° / ₀ TiSi _LR9 and 5.3 correspond ° / o titanium oxide.

Example 19

Following the procedure of Example 1, 123 parts by weight of colloidal zirconium dioxide are reacted with 116 parts of calcium metasilicate and 160 parts of calcium in a melt consisting of 800 parts of calcium chloride, working at 900 to 950 ° C, which is carried out according to the procedure of Example 2. The reactants are introduced over the course of 2 hours, the temperature being maintained between 900 and 950 ° C. during the addition. The mixture is stirred for a further hour at 850 to 900 ^° C., then the thermocouple is pulled out of the melt and the reaction device is allowed to cool to room temperature under argon.

The solidified "salt cake is broken up, pulverized and slurried with an aqueous 5 ° / _o by weight hydrochloric acid at 0 ° C, which is carried out under argon. The resulting suspension is nitrated using a medium Glasfrittefilters. The residue is

the previously finely divided titanium metal at 800 ° C 50 has been again with 5 ° / _o hydrochloric acid, washed, and then freed of reactive ingredients, wherein further extracted three times with water. After

the gas outlet is connected to a washing device. With good agitation by the stirrer, the calcium chloride is melted and the melt at 950 ⁰ C is placed.

By means of the additional flasks, the reactants are introduced into the reaction device in small, aliquot portions, the addition taking place alternately and the additional rate being controlled with regard to the development of heat, which is indicated by the thermocouple in the reaction device. In this way, the proportions of the reactants can be kept close to the values which are stoichiometrically necessary for the reduction of the titanium dioxide and its conversion into titanium silicide. The temperature is maintained during the reaction in the range from 950 to 1000 ^° C., the addition being completed in the course of 2 hours. In the first aqueous extraction, part of the product is in the form of a stable aqueous dispersion which is centrifuged to obtain the product .

The supernatant material from the last two extractions is made up of dilute brines. The Projecting material from the last spin has a pH of 7.3 and a solids content of 0.8%. Electron micrographs show that the dispersed material is in the form of spherical, for largely non-aggregated particles ranging in size from 20 to 30 millimicrons. The sol is concentrated by evaporation under reduced pressure to a solids content of 18%.

The solids content in the dispersed phase is 79%.

The residue from the centrifugation is dried in a vacuum oven and analyzed, whereby one

87 ° / o zirconium silicide, ZrSi ₀ ", and 11.3 ° / ₀ zirconia obtained.

By X-ray analysis, is identified as a main crystalline phase present ZrS wherein K 'is CuKa = 1.2 x 10-. ³

Example 20

96 parts by weight calcium silicide crushed to a size that would fit a 20 mesh (0.84 mm) sieve happens, and 40 parts of calcium are in the course of 2 hours in a melt of 700 parts Calcium chloride and 328 parts of niobium dichloride entered. The temperature is during the addition Range from 800 to 850 ° C, and the bath becomes another after the addition of the calcium silicide and calcium Maintained at this temperature for an hour with stirring. The product is made from the salt cake in the example 18 described way.

The X-ray analysis of the product gives a good diagram for niobium silicide, where K ' CuK «= 2.6 · 10" ^3. The analysis values for niobium, silicon and oxygen are correct with a mixture of 95% niobium disilicide and 2.7% niobium oxide, Nb ₂ O _3, the same. the emission spectrography shows that the product contains less than 1.0 ° / ₀ iron, chromium, nickel and CaI-cium. the surface area as determined by nitrogen adsorption, an average particle size of about 40 millimicrons is equivalent.

Example 21

30th

Following the procedure of Example 17, a Mixture of 180 parts by weight of colloidal silica and 360 parts of calcium in the course of 2 hours at 800 to 850 ° C to a melt of 366 parts of vanadium dichloride and 1000 parts of calcium chloride added. The product is, as described in Example 18, by extraction with methanolic Acetic acid obtained.

The X-ray diagram shows vanadium silicide, V ₂ Si, as the main component at a K ' CuK "= 7.2 · 10 ^-3 . The analysis for vanadium and silicon shows a composition of 96% V ₁₁₈ Si, which also shows the presence of lower vanadium silicides. The oxygen content is 2.1% and the amount of other metallic impurities, chromium, nickel and iron, is less than 0.5% (emission spectrograph).

The last methanol wash contains 1.3% of the product in the form of a stable dispersion, which one by evaporating the solvent to a solids content of 15%. Electron micrographs of the stable sol obtained show that the dispersed particles are dense and largely are not aggregated and are substantially spherical in shape, being the average particle size is about 10 millimicrons. The solids content in the dispersed phase is 65%.

Example 22

60

Following the procedure of Example 2, 140 parts by weight of powdered colloidal silica at 880 to 900 ° C in the course of 2 ¹ J ₂ hours in a melt of 1000 parts of calcium chloride with 235 parts of calcium molybdate and 330 parts of calcium to be implemented. The melt is another 1 alb; Stirred at 880 to 900 ° C. for an hour. The product is obtained in the manner described in Example 19 by aqueous extraction, using acetic acid instead of hydrochloric acid.

100 parts by weight of the dry powder are refluxed with 2000 parts of 1 η sodium hydroxide solution for 1 hour, filtered and washed free of alkali. The residue is oven in a vacuum at 80 to 9O ⁰ C dried.

The product analytically gives 91% MoSi ₂ with an oxygen content of 3.5%. Emission spectrography reveals the presence of less than 1% calcium and less than 2% iron, chromium and nickel in the product. The X-ray analysis gives a good map for MoSi _2, and K 'CuK "is 8.6 x 10 ~ ^4th The surface area, determined by nitrogen ^{adsorption, is 10 m 2} / g, which corresponds to an average particle size of 80 millimicrons.

The last aqueous wash contains 0.5% of the product in the form of a stable dispersion, which one concentrated by evaporation in vacuo to a solids content of 11%. The particle size gives on the basis of an electron micrograph, to 80 to 130 millimicrons, and the solids content in the dispersed phase is 70%. A sample of the dried solid gives a clear X-ray diagram for molybdenum disilicide.

Example 23

Following the procedure of Example 1, 456 parts by weight of colloidal chromium oxide, Cr ₂ O ₃ , are reacted at 900 to 95O ° C. over the course of 5 hours in 1000 parts of calcium chloride with 96 parts of calcium silicide and 320 parts of calcium. The product is obtained by aqueous extraction.

The product yields analytically 92% Cr _{2> e} Si, and the X-ray analysis shows mainly Cr ₃ Si, where K 'CuK "is = 2-10. ³ The oxygen content is 2.8%.

Example 24

Following the procedure of Example 1, 232 parts by weight of colloidal tungsten trioxide, WO ₃ , are reacted at 1050 to HOO ⁰ C in 750 parts of calcium chloride with 96 parts of calcium silicide and 80 parts of calcium over the course of 3 hours. The product is obtained by aqueous extraction.

The product yields analytically 96% WSi _{1, 8,} and X-ray analysis shows mainly tungsten disilicide, wherein K 'CuKa = 5.6 x 10 ~ ⁴ is (average of two lines). The oxygen content is 1.4%.

B e i s ρ i e 1 25

A reaction device made of an alloy of about 66 to 67% Ni, 28 to 34% Cu, remainder Fe, Mn, C and Si is charged with 125 parts by weight of sodium molybdate dihydrate, 220 parts of sodium silicate pentahydrate and 1000 parts of sodium chloride, the mixture is subjected to slow dehydration heating and finally brings the melt to 915 ° C. with thorough stirring, working under argon. The temperature is maintained at 915 to 925 ° C. and ^{210 parts of metallic calcium are added in small aliquots over the course of 5 1 1} ₂ hours, the sodium formed as a by-product being distilled off from the reaction device. The product will

009 551/366

obtained in the manner described in Example 20 by aqueous extraction, using acetic acid works in place of hydrochloric acid.

The product analytically gives 91% MoSi ₂ with an oxygen content of 3.2%. The emission spectrograph shows less than 1% calcium and less than 2% iron, chromium and nickel in the product. X-ray analysis gives a strong, sharp MoSi ₂ diagram, and the surface area, as determined by nitrogen adsorption, is 22 m ² / g.

40 parts by weight of the above product are refluxed with 1000 parts of normal sodium hydroxide solution for 1 hour, whereupon the mixture is filtered and the residue is rendered alkali-free. The residue is dried in a vacuum oven at 80 to 90 ^° C .; analytically it gives 94% MoSi ₂ with an oxygen content of 1.5%. The surface area, determined by nitrogen ^{adsorption, is 5 m 2} / g, which corresponds to an average particle size of 200 millimicrons. A clear, clear MoSi ₂ X-ray diagram is obtained, and the measured line broadening gives K ' CuKoc to 4.1 · 10 ^-4 .

Claims (6)

Patent claims: 1. Process for the production of finely divided carbides of boron or silicon, of silicon boride, of borides, silicides or carbides of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum or tungsten with a particle size of 1 to 250 millimicrons, characterized that the reactants, of which at least one contains the essential element in a positive valence stage, in the desired proportions in a molten salt bath at 200 to 1200 ⁰ C in the presence of an alkali or alkaline earth metal as a reducing agent in an inert atmosphere during such Time span converts that the product flocculates, the reducing agent being used in an amount that the element with the positive valence is reduced to zero valency, and that the flocculated product is then separated from the salt bath. 2. The method according to claim 1, characterized in that one works to produce particles with a size of 10 to 200 millimicrons at 400 to HCO ⁰ C while moving the molten salt bath and the concentration of the essential elements in the molten salt bath at least 100 times the concentration holds, which is necessary due to the solubility product of the compound to be established. 3. The method according to claim 2, characterized in that the reactants of the salt bath melt continuously or periodically, stoichiometrically, during the course of the reaction equivalent proportions are added. 4. The method according to claim 1, characterized in that after the separation of the flocculated metal-like compound from the salt bath, this compound of an oxygen-containing environment exposes until it is bound to oxygen in an amount based on the total weight of the Composition, of ISD ² + 12D + 2
5 D (qD ² + 1.8 D + 1.2) up to 25% contains, where D is the average particle size, determined by the BET method, in millimicrons and ρ is the density of the metal-like compounds g / ml. 5. The method according to claim 4, characterized in that the flocculated metal-like compound, after separation from the salt bath, is exposed to an oxygen-containing environment until it contains oxygen in bound form in an amount, based on the total weight of the composition, of 30 / qD to Contains 10%. 6. The method according to any one of claims 1 to 5, characterized in that the obtained Product suspended in a liquid.