JPH0772084B2 - New carbon-containing composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel carbon-containing composition containing a metal oxide and elemental carbon, which is in a state of being extremely finely mixed as never before.

[Background technology]

Conventionally SiC, TiC, WC, B ₄ C, ZrC, HfC, NbC, Mo ₂ C, Ta
Metal carbides such as C, Cr ₃ C ₂ and VC are obtained by reacting these simple metals or metal oxides with simple carbons such as coke and carbon black in an inert gas such as argon or helium under strong heat. Are manufactured.

Further, metal nitrides such as Si ₃ N ₄ , TiN, BN, ZrN, AlN, HfN, and NbN are strong metal oxides of these metals and elemental carbon under a nitrogen-containing compound gas atmosphere such as nitrogen and ammonia. It is manufactured by reacting under heat.

The powder (powder) of such metal carbide or metal nitride is
The finer the particles, the greater the strength of the molded body obtained by sintering and processing the same, and the faster the sintering rate. Therefore, it is inevitable that fine particles are uniformly mixed as a simple substance metal as an intermediate raw material or a mixture of these metal oxides and a simple substance carbon.

As a method for obtaining a uniform mixture of these fine particles, conventionally,
Usually, a method of mechanically pulverizing coarse particles or lumps of a simple metal or metal oxide and a simple carbon in a batch system has been adopted. However, such a mechanical batch method is complicated in workability such as charging raw materials into a crusher, taking out crushed products, and excessive generation of dust, noise at the time of crushing, and long time crushing for producing fine powder. There are various problems such as the necessity and mixing of impurities due to abrasion of the crusher itself, and it is theoretically and essentially impossible to obtain an ultrafine mixture of 1 μm or less.

Therefore, as a further improved method, Japanese Patent Publication No. 50-12790
As described in Japanese Patent Publication No. 0, as described in JP-B-51-13262, a method of dispersing two or more kinds of fine powder in water in a colloidal form and spray-drying using a spray dryer. A method has also been proposed in which two carrier gases, each containing a fine powder, are combined, and the two are mixed in a gas phase to mix the two powders in a gas phase.

However, even in this method, it is difficult to obtain a completely mixed state from a microscopic point of view. Bare silicon oxide powder,
In powders such as titanium oxide powder and carbon powder particles, a strong secondary agglomerate, which is usually an aggregate of 20 to 100 single particles, is already formed. There is a fundamental and essential problem that it is difficult to form a homogeneous mixture that exists independently of each other.

On the other hand, as described in U.S. Pat.No. 3,123,567, aluminum oxide, beryllium oxide, metal oxides such as titanium oxide, and for the purpose of obtaining a fine mixture of elemental carbon, these metal oxides 900 There is also known a method of precipitating elemental carbon on the surface of particles of a metal oxide by heating at a temperature of ℃ or higher and bringing it into contact with a C _{1 to} C ₄ hydrocarbon to thermally decompose it.

However, this method is also an ideal mixed state in which the state of simple carbon covering the surface of the secondary aggregate of the metal oxide is fine, and in practice, more than 100 secondary aggregates are usually collected. There is an essential problem that the state where carbon covers the surface of the apparent powder particles becomes the minimum unit of the mixed state.

[Object of the Invention]

An object of the present invention is to provide a carbon-containing composition in which a metal oxide and elemental carbon are in a state in which they are significantly more uniformly and finely mixed than the mixed state obtained by these conventional methods. More specifically, a single particle of a carbon-containing composition composed of fine particles of a micron size or less is present in a uniform and fine particle size such that both metal oxide finer than that particle and elemental carbon coexist. Another object of the present invention is to provide a carbon-containing composition exhibiting a state that can be said to be the limit of proper mixing.

[Disclosure of Invention]

The present invention is a carbon-containing composition containing a metal oxide and elemental carbon, wherein the carbon-containing composition comprises fine particles having an average particle diameter of 0.5 μ or less, and the carbon-containing composition has a specific surface area (a). Is 5 m ² / g or more, both the carbon specific surface area (b) and the metal oxide equivalent specific surface area (c) are 100 m ² / g or more,
The carbon specific surface area (b) and the metal oxide specific surface area (c) are both larger than the specific surface area (a) of the carbon-containing composition, and the metal oxide is defined by the following formula (1). A contact ratio α is 0.5 or more, In particular, when the metal oxide is an oxide of silicon, boron or aluminum, both the carbon specific surface area (b) and the metal oxide specific surface area (c) are 150 m ² / g or more. .

Hereinafter, the present invention will be described in detail.

The metal oxides of the present invention include Group IA metals such as lithium, sodium, potassium, rubidium and cesium; Group IIA metals such as beryllium, magnesium, calcium, strontium and barium; Group IVA groups such as titanium, zirconium and hafnium. Metals such as vanadium, niobium and tantalum
Group VA metals; VI A such as chromium, molybdenum, tungsten
Group metals; manganese, technetium, rhenium, etc. VII A
Group metals; iron group metals such as iron, ruthenium and osmium; cobalt group metals such as cobalt, rhodium and iridium; nickel group metals such as nickel and palladium; group IB metals such as copper, silver and gold; zinc, cadmium and mercury. Group II B metals such as;
Boric acid, aluminum, potassium, indium, etc. III
Group B metal: Group IVB metal such as silicon, germanium, tin, lead; Group VB metal such as phosphorus, arsenic, antimony, bismuth; Group VIB metal such as sulfur, selenium, tellurium; Cerium, praseodymium, neodymium, thorium , Oxides of a wide range of metals such as uranium and other basic earth metals,
Among them, oxides of silicon, titanium, tungsten, boron, aluminum, zirconium, hafnium, niobium, molybdenum, tantalum, chromium and vanadium are suitable as raw materials for carbides and nitrides of these metals which are heat and corrosion resistant ceramic materials. It can be used and has high industrial utility value. In addition, the metal oxide shall include a metal hydroxide here.

The first feature of the carbon-containing composition of the present invention is that it comprises fine particles having an average particle diameter of 0.5 μm or less. The average particle size here is defined as the arithmetic mean value of the particle sizes of the single particles, and the particle size of the single particles is defined as the average value of its maximum length and minimum length.

Next, the carbon-containing composition of the present invention has a specific surface area (a) of 5 m ²
The second feature is that the powder is at least / g. The specific surface area mentioned here means a nitrogen adsorption specific surface area (a value measured by a so-called BET method). Nitrogen adsorption specific surface area is used as a simple measure of the average particle size of the powdery solid,
A large nitrogen adsorption specific surface area means that the average particle diameter is small.

Furthermore, the third feature of the carbon-containing composition of the present invention is that the carbon-specific surface area (b) is 100 m ² / g or more, preferably 150 m ² / g or more. Here, the carbon-specific surface area (b) is defined as the specific surface area of the elemental carbon remaining after removing the metal oxide from the carbon-containing composition without changing the form of the elemental carbon. Defined as a measurement method, in the present invention, is defined as the specific surface area of elemental carbon remaining after the metal oxide is dissolved and removed by an acid or an alkali. As a method of dissolving and removing with an acid or the like, for example, SiO ₂ ,
Ta ₂ O ₅ etc. is hydrofluoric acid, TiO ₂ , ZrO ₂ , MoO ₂ , WO ₂ etc. is sulfuric acid, V ₂ O ₅ , CrO ₃ , H ₃ BO ₃ , Al (OH) ₃ etc. is hydrochloric acid, WO ₃ etc. can be dissolved and removed with aqueous ammonia.

The fourth characteristic is that the specific surface area (c) corresponding to the metal oxide is 100 m ² / g or more, preferably 150 m ² / g or more.
Here, the metal oxide-equivalent specific surface area (c) means the specific surface area of the metal oxide remaining after removing the elemental carbon, which is the opposite of the carbon-equivalent specific surface area. As a method for removing carbon, the carbon-containing composition is 600 ± 5 in air.
A method of heating at 0 ° C. and removing by combustion is adopted. The fifth feature is that both the carbon-specific surface area (b) and the metal oxide-specific surface area (c) are larger than the specific surface area (a) of the carbon-containing composition. The fifth characteristic is that, in its physical meaning, the state in which the metal oxide contained in the carbon-containing composition of the present invention and the elemental carbon coexist are such that they are in contact with each other and the nitrogen adsorption specific surface area is measured. It means that the surface of the carbon-containing composition is formed in a state where the surfaces that can be adsorbed are canceled each other. That is, in a single particle of the carbon-containing composition, there exists a state where the metal oxide is surrounded by the elemental carbon or a state where the elemental carbon is surrounded by the metal oxide.

Furthermore, the sixth feature of the present invention is that the metal oxide contact ratio defined by the above formula (1) is required to be 0.5 or more. Here, a is the specific surface area of the carbon-containing composition, b is the specific surface area corresponding to carbon, and c is the specific surface area corresponding to the metal oxide. The metal oxide content rate and the carbon content rate are 1 and 1 respectively, based on the weight of the carbon-containing composition. It means the weight ratio of them. The meaning of the equation (1) will be described below with reference to a schematic diagram. FIG. 1 shows a model of one state of particles forming the carbon-containing composition. x represents the exposed area of the metal oxide, that is, the portion that appears in the specific surface area of the carbon-containing composition (that is, the portion that is measured as the specific surface area), and y is the exposed surface of elemental carbon (that is, the measured value as the specific surface area). Part).
z represents the area of the portion where the metal oxide and the elemental carbon contact each other in a single particle. As is clear from the figure, such a portion is a portion that appears in the carbon-equivalent specific surface area by removing the metal oxide, and a portion that appears in the metal oxide-equivalent specific surface area by removing elemental carbon. Therefore, the ratio of the portion of the surface of the metal oxide that is in contact with elemental carbon is α =
It is represented by z / (x + z), and this value is what the metal oxide contact ratio α means. What happens is that the metal oxide content, carbon content and a, b, c, x, y, z have the following relationship: x + y = a y + z = carbon content × b x + z = metal oxide Content xc Substituting these into α = z / (x + z) to obtain α, the formula (1) is derived.

The metal oxide contact ratio of 0.5 or more, which is the sixth feature of the present invention, means that 50% or more of the surface of the metal oxide is covered with elemental carbon. If the contact ratio α is 0, the particles of the metal oxide and the elemental carbon are independent without contacting each other, and if the contact ratio α is 1, the particles of the metal oxide are completely covered with the elemental carbon. Needless to say.

A carbon-containing composition that satisfies these above characteristics or requirements is
A single particle of fine powder with an average particle size of 0.5μ or less and a specific surface area of 5m ² / g or more, in which metal oxides of even finer size and elementary carbon coexist. Is understood. No such powder having a uniform and fine mixed state, which can be said to be the ultimate, has been known at all.

As a method for producing such a carbon-containing composition, for example, the method previously proposed by the present inventors in JP-A-59-49828, that is, a decomposable metal compound and decomposition in hot gas containing steam It can be basically obtained by charging a functional carbon compound to generate a mixed aerosol containing a metal oxide and a simple substance, and collecting the dispersoid.

More specifically, the novel carbon-containing composition of the present invention is produced by using a reaction furnace as shown in FIG. 2 to obtain SiCl ₄ , CH ₃ SiCl ₃ , TiC.
l _4, BF _3, B etc. _{(OCH 3) 3, AlCl 3} , Al (OCH 3) 3, easily hydrolyzed in hot gas containing water vapor, causing a reaction such as thermal decomposition, oxides of the metals And a decomposable carbon compound such as toluene, xylene, gas oil, heavy oil, and ethylene bottom that can easily decompose when charged in hot gas to form simple carbon (soot). Can be simultaneously charged into hot gas containing water vapor, and the dispersoid can be separated and collected from the aerosol produced by these chemical reactions to produce the product. The carbon-containing composition obtained by this method exhibits an extremely uniform and fine mixed state of metal oxide and elementary carbon. The reason for this is that the decomposable metal compound and the decomposable carbon compound as raw materials are simultaneously decomposed in a hot gas containing steam to first generate a metal oxide and a simple substance carbon of a molecular level. It is possible to produce a metal oxide and elemental carbon, and at the same time, to mix them both at the molecular level, so it is presumed that a mixed state that can be said to be extremely uniform and perfect in principle can be obtained. To be done.

The average particle size of the carbon-containing composition, the carbon content, the metal oxide content, the specific surface area, the carbon-specific specific surface area, the metal oxide-equivalent specific surface area, the metal compound charging amount is a manufacturing condition of the carbon-containing composition, In order to obtain a carbon-containing composition which can be operated depending on the amount of carbon compound charged, the type of charging nozzle, the amount of fuel for hot air, etc. The conditions may be adopted.

(1) The maximum temperature in the reactor is 600 ℃ or higher, preferably 700
~ 1600 ℃

(2) The amount of the metal compound charged is 0.5 to the ratio of the g-atomic weight of the metal to be charged and the molar molecular weight of water vapor contained in the hot gas (mol-molecular weight H ₂ O / g-atomic metal). It is set to 20, preferably 1 to 7.

(3) The charging amount of carbon compound is 0.05 per 1 m ^{3 of} hot gas.
~ 0.6 kg, preferably 0.1-0.4 kg.

(4) The charging ratio of the carbon compound to the metal compound is 5 to 50, preferably 8 in terms of the formula weight ratio of carbon in the carbon compound to metal in the metal compound (g-atom C / g-atom metal). Set to ~ 30.

(5) The carbon compound and the metal compound may be charged into the reaction furnace through separate nozzles, but it is preferable to raise the temperature (if necessary) to a gas state or a liquid state. A premixed product is charged into the furnace through a single nozzle.

[Advantageous effects of the invention]

INDUSTRIAL APPLICABILITY The present invention is far more than a mixture of metal oxide and elemental carbon obtained by physically mixing fine powders in a gas phase, as in the conventional method of spray drying or combining two kinds of carrier gases. To provide a carbon-containing composition that is homogeneously and finely mixed, and the essential difference in the mixing form lies in the following points.

That is, in the conventional method of physically mixing the fine powder in the gas phase by the spray drying method or the like, the secondary agglomerates of the powders of the respective particles are actually used, even if seemingly complete mixing appears. Is only the minimum unit for mixed content.

This is because the particles of the respective fine powders to be sprayed are welded to each other and already form the secondary aggregates in the form of grapes each having a unit of 20 to 100, and in order to evenly mix the particles, It is necessary to break the secondary agglomerate into individual particles that are its constitutional units and decompose them into pieces, but the binding of the agglomerate is extremely strong, and the usual means is to cut this. Is extremely difficult.

However, the carbon-containing composition of the present invention comprises one particle of the fine powder itself in a state where finer metal oxide fine particles and elementary carbon fine particles are coexistent than the above-mentioned conventional method. It is understood that even if the units of the secondary agglomerates obtained by the method can be decomposed into pieces by some special method, the carbon-containing composition is much more excellent in terms of uniformity and fineness.

[Industrial availability]

If the metal oxide contained in the carbon-containing composition is an oxide of silicon, titanium, tungsten, boron, aluminum, zirconium, hafnium, niobium, molybdenum, tantalum, chromium, vanadium, these carbon-containing compositions are strongly Thermal reaction of SiC, TiC, WC, B ₄ C, ZrC, HfC, Nb
It is possible to obtain metal carbides such as C, Mo ₂ C, TaC, Cr ₃ C ₂ and VC, and to carry out ignition reaction under a nitrogen-containing compound gas atmosphere such as nitrogen and ammonia to produce Si ₃ N ₄ , TiN, BN, ZrN, A
It is possible to obtain metal nitrides such as lN, HfN and NbN.

These metal carbides and metal nitrides obtained by using the carbon-containing composition of the present invention as raw materials are metal carbides obtained by using a mixture of a metal oxide and elemental carbon mixed by a conventional spray drying method as a raw material. Compared to the above, it has a feature of being extremely fine and can be suitably used as a raw material powder for a ceramic sintered body.

Incidentally, when the metal oxide is an oxide of silicon, boron, or aluminum, the experimental findings of the present inventors indicate that the carbon-specific composition has a carbon-equivalent specific surface area and a metal oxide-equivalent specific surface area of 150 m ² / g. More than that, SiC, B ₄ C, Si ₃ N ₄ , B
It is easy to obtain finer N and AlN powders.

In addition to the use for these ceramic materials, paints, lacquers, printing inks and other pigments, synthetic resins,
It can also be used for applications such as filling reinforcing agents such as rubber and adhesives.

Manufacture example 1 Using the reactor shown in FIG.
m ³ / h charging, hydrogen 10Nm ³ / h supply from combustion burner 3,
The hot gas containing water vapor was obtained by burning. At the same time, a mixture of toluene as a decomposable carbon compound and SiCl ₄ as a decomposable metal compound in a weight ratio of 1: 1 was charged from the nozzle 4 into the furnace at a flow rate of 30 kg / h. The inside of the furnace was maintained at 1050 ° C. at the position shown in FIG. The aerosol generated in the furnace was extracted from the duct 6, cooled, and then the dispersoid was collected by a bag filter to obtain a carbon-containing composition of 9.8 kg / h. Under these operating conditions, the ratio of the g-atomic weight of the charged metal to the molar molecular weight of water vapor contained in the hot gas, the charged amount of the carbon compound per 1 m ³ of the hot gas, the carbon in the carbon compound and the metal compound The formula weight ratios of the metals were 5.05, 0.143 and 12.9, respectively.

Example 1 The results of measuring the average particle size, carbon content, SiO ₂ content, and specific surface area (a) of the carbon-containing composition obtained in Production Example 1 are:
It was 0.015μ, 46%, 53% and 45 m ² / g, respectively.

Further, 5 g of the carbon-containing composition was added with 100 c of HF aqueous solution having a concentration of 45% by weight.
c) SiO ₂ was dissolved and removed, and the specific surface area (b) of the remaining elemental carbon was measured to be 233 m ² / g, while the carbon-containing composition was heated in air at 600 ° C. Was removed by burning and the specific surface area (c) of the remaining SiO ₂ was measured, and the result was 362 m ² / g. The metal oxide SiO ₂ contact ratio α calculated from these values using the formula (1) was 0.66.

30 g of the carbon-containing composition obtained in Production Example 1 was charged into a graphite crucible, heated in an argon atmosphere at 1700 ° C. for 2 hours, cooled once, and then heated in air to 600 ° C. Was removed by burning to obtain 10.2 g of SiC powder. Got
As a result of analyzing the X-ray diffraction spectrum of the SiC powder, it was observed that the crystal shape was cubic, its average particle diameter by electron microscope image analysis was 0.16 μ, and the particle shape was a uniform spherical shape. Permeation of carbon-containing composition in FIG. 3, carbon single substance remaining after removing SiO ₂ from the carbon-containing composition in FIG. 4, and SiC powder obtained by heating the carbon-containing composition in FIG. A type electron microscope image is shown.

Production Examples 2 to 12 In the same manner as in Production Example 1, using the compounds shown in Table 1 as the fuel, decomposable metal compound and decomposable carbon compound for obtaining hot gas containing water vapor, the conditions shown in Table 1 were used. A carbon-containing composition was obtained.

The decomposable metal compound and the decomposable carbon compound are produced in Production Example 2
In Nos. 7 and 9 to 12, they were premixed and charged into the furnace through a nozzle. Further, in Production Example 8, the decomposable metal compound and the decomposable carbon compound were separately charged into the furnace from the nozzle 4 and the nozzle 5, respectively.

Examples 2 to 7 and Comparative Examples 1 to 5 Average particle size, carbon content, SiO ₂ content, specific surface area (a), carbon equivalent specific surface area (b) of the carbon-containing compositions obtained in Production Examples 2 to 12 ), SiO ₂ equivalent specific surface area (c) and SiO ₂ contact ratio α are shown in Table 2. The measuring method is the same as in Example 1.

Using 30 g of each of the carbon-containing compositions obtained in Production Examples 2 to 12, powders of carbides or nitrides were obtained under the conditions shown in Table 2. Table 2 shows the amount of the produced carbide or nitride powder and the average particle size. In Table 2, Example 2 is the result obtained by using the carbon-containing composition obtained in Production Example 2. In the following, Production Example 3 is Example 3 and Production Example 4 is Example 4. Production Example 5 is Example 5, Production Example 6 is Example 6, Production Example 7 is Example 7, Production Example 8 is Comparative Example 1, Production Example 9 is Comparative Example 2, and Production Example 10 is Comparative. Production Example 11
Corresponds to Comparative Example 4, and Production Example 12 corresponds to Comparative Example 5.

The crystal shape of the generated carbide or nitride was as shown in Table 2. Further, the average particle diameters of carbides and nitrides obtained by electron microscope image analysis are the values shown in Table 2, and the carbides obtained in Examples 2 and 3 are spherical particles with uniform particle diameters. Was observed,
In Examples 5 to 7, it was observed that the particles were slightly aggregated with each other, and in Comparative Examples 1 to 5, in addition to the particles being significantly aggregated with each other, coarse particles having a particle diameter of 1 μm or more were observed. It was observed to contain 15-20% by weight. FIG. 6 shows a transmission electron micrograph of the carbide (SiC) obtained in Comparative Example 1.

Comparative Example 6 Commercially available carbon powder (carbon black, specific surface area 118 m ² /
g) and SiO ₂ fine powder (Aerosil, specific surface area 205 m ² / g) in a weight ratio of 0.46: 0.54 so as to match the carbon content and SiO ₂ content of the carbon-containing composition of Example 1. The mixture was mixed for 10 hours using a wet vibration mill and then dried using a spray dryer to obtain a mixture of carbon and SiO ₂ . The average particle size of the obtained mixture was 0.019μ, the specific surface area (a) was 149 m ² / g,
Carbon specific surface area (b) measured in exactly the same manner as in Example 1
Was 118 m ² / g and the specific surface area (c) corresponding to SiO ₂ was 205 m ² / g. From these, the SiO ₂ contact ratio (metal oxide contact ratio) α was calculated to be zero. From 30 g of this mixture, exactly the same as in Example 1, after heating at 1700 ° C. for 2 hours, the remaining elemental carbon was burned and removed to obtain 6.8 g of SiC powder. The crystal shape of the obtained SiC powder was cubic. Its average particle size is 3.4μ by electron microscope image analysis, and almost all particles have particle size of 1
It was observed that the particles were coarse particles of μ or more.

Comparative Example 7 TiC according to the method disclosed in US Pat. No. 3,123,567
A powder was produced. Commercially available TiO ₂ fine powder (specific surface area 60 m ² / g)
100 g of the above was molded into a granule having a diameter of 4 to 6 mm was charged into a heating furnace of a gas combustion system, and the inside of the furnace was heated by hot gas obtained by burning hydrogen. When the furnace temperature rises to 1200 ° C, the hot gas supply is stopped and methane is replaced instead.
It was charged into the heating furnace at a flow rate of 1.0 Nm ³ / h for 1 hour. After cooling
In the TiO ₂ granules taken out from the heating furnace, 125 g of elemental carbon was deposited by thermal decomposition of methane, and 225 g was obtained as a mixture of TiO ₂ and elemental carbon. The average particle size of the obtained mixture was 0.48 μm, the specific surface area (a) was 120 m ² / g, and Example 5 was used.
Carbon equivalent specific surface area (b) measured in exactly the same manner as
The specific surface area (c) corresponding to 0 m ² / g and TiO ₂ was 52 m ² / g, and the TiO ₂ contact ratio was calculated to be 0.08 from these.

From 30 g of this mixture, 1800 ° C. exactly as in Example 3.
After heating for 3 hours, the remaining elemental carbon is burned and removed to remove TiC.
9.9 g of powder was obtained. The crystal form of the obtained TiC powder was cubic, and its average particle size was 3.2 μm by electron microscope image analysis.
It was observed that almost all the particles were coarse particles having an average particle size of 1 μm or more.

From the above Examples and Comparative Examples, from the carbon-containing compositions satisfying all the requirements characteristic of the present invention as in Examples 1 to 4, it is considered fine as a powder for a sintered body raw material,
It is understood that a nearly spherical carbide or nitride powder with a uniform particle size is obtained. From Examples 5 to 7, when the carbon specific surface area (b) and the metal oxide specific surface area (c) are 100 m ² / g or more and less than 150 m ² / g,
The obtained carbide or nitride powder tends to be in a state of slightly secondary aggregation, more preferably 150 m.
It is understood that it is desirable that it is ² / g or more.

From Comparative Examples 1 to 5, fine carbon particles having a uniform particle size, which are preferable as a raw material powder for a sintered body, should be used as a raw material without using a carbon-containing composition satisfying all of the six characteristics of the present invention, or In order to obtain a nitride powder, and to obtain such a carbon-containing composition, (1) the maximum temperature in the reaction furnace is 600 ° C or higher, preferably 700 ° C.
~ 1600 ℃

(2) The charging amount of the metal compound is 0.5 to the ratio of the g-atomic weight of the metal to be charged and the molar molecular weight of water vapor contained in the hot gas (mol-molecular H ₂ O / g-atomic metal). It is set to 20, preferably 1 to 7.

(3) The charging amount of carbon compound is 0.05 per 1 m ^{3 of} hot gas.
-0.6 kg, preferably 0.1-0.4 kg.

(4) The ratio of the charging amounts of the carbon compound and the metal compound is 5 to 50, preferably the formula weight ratio (g-atom C / g-atom metal) of carbon in the carbon compound and metal in the metal compound. 8 to 30.

(5) The carbon compound and the metal compound may be charged into the reaction furnace through separate nozzles, but preferably (if necessary).
By raising the temperature, all are in a gas state or both are in a liquid state, and a mixture of these in advance is charged into the furnace through a single nozzle.

It is understood that the adoption of the above five conditions is essential.

In Comparative Example 6, even if the elemental carbon and the metal oxide SiO ₂ are fine powders, the metal oxide contact ratio α is zero by the method of mechanically mixing, and the obtained carbide or nitride is the same as that of the present invention. It is understood that the particle diameter is as much as one digit larger than that of the carbide or nitride obtained from the carbon-containing composition, and from Comparative Example 7, the thermal decomposition of hydrocarbons was observed on the surface of the particles of the metal oxide TiO _2. In the method of precipitating elemental carbon, the metal oxide TiO ₂ contact ratio α is 0.08, which is only 20% or less of the metal oxide TiO ₂ contact ratio α of the carbon-containing composition of the present invention. It is clear that the obtained TiC also has an average particle size one digit larger than that of the TiC obtained from the carbon-containing composition of the present invention.

Here, electron microscope images shown in FIGS. 3 to 9 will be described.

FIG. 3 is a photographic image of a composition containing SiO ₂ and elemental carbon of Production Example 1, and FIG. 4 is a photographic image of carbon remaining after the SiO ₂ was dissolved and removed from the composition. When these two are compared, it is observed that the morphology is changed in FIGS. 3 and 4, and shell-shaped particles lacking the central part of the particles are observed in FIG. This indicates that the carbon-containing composition has a state in which SiO ₂ is surrounded by simple carbon in a single particle.

The same thing is compared between FIG. 7 which is a photographic image of the carbon-containing composition of Production Example 3 and FIG. 8 which is a photographic image of elemental carbon remaining after TiO ₂ is dissolved and removed from the carbon-containing composition. Even in
It shows that TiO ₂ is surrounded by elemental carbon.

FIG. 5 and FIG. 9 are photographic images of SiC and TiC particles obtained from the carbon-containing compositions of Examples 1 and 3, respectively, and it can be seen that they have a spherical shape with a narrow particle size distribution. In comparison with these, in the photographic image of the SiC powder obtained in Comparative Example 1 in FIG. 6, it can be seen that secondary aggregation and coarse particles in which the particles are bound to each other are included in large amounts.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a mixed state of a metal oxide and elementary carbon in one particle forming a carbon-containing composition. In the figure, x is the area of the exposed part of the metal oxide, y is the area of the exposed part of the elemental carbon, z is the area of the part where the metal oxide and the elemental carbon are in contact in one particle. Show. FIG. 2 is a cross-sectional view showing an example of a reaction furnace for obtaining the carbon-containing composition of the present invention. In the drawing, 1 .... Furnace material, 2 .... Duct, 3 .... Combustion burner, 4 ....
… Nozzle, 5 ... Nozzle, 6 ... Shows duct. FIG. 3 to FIG. 9 are photographs showing the crystal state of various powder particles, which are taken with a transmission electron microscope. Here, FIG. 3 shows the carbon-containing composition obtained in Production Example 1, and FIG. 4 shows the elemental carbon remaining after dissolving and removing SiO ₂ from the composition. FIG. 5 shows the SiC obtained in Example 1, and FIG. 6 shows the SiC obtained in Comparative Example 1. FIG. 7 shows the carbon-containing composition obtained in Production Example 3, FIG. 8 shows the elemental carbon remaining after the removal of TiO ₂ from the composition, and FIG. 9 shows the TiC obtained in Example 3. The magnifications are 40,000 times in FIGS. 3, 4, 7, and 8 and 20,000 times in FIGS. 5, 6, and 9.

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Claims (3)

[Claims] 1. A carbon-containing composition containing a metal oxide and elementary carbon, the carbon-containing composition comprising fine particles having an average particle size of 0.5 μ or less, and a specific surface area of the carbon-containing composition ( a) is 5 m ² / g or more, carbon specific surface area (b) and metal oxide equivalent specific surface area (c) are both 100 m ² / g or more, carbon equivalent specific surface area (b) and metal oxide equivalent Each of the specific surface areas (c) is larger than the specific surface area (a) of the carbon-containing composition, and the metal oxide contact ratio α defined by the following formula (1) is 0.5 or more. A novel carbon-containing composition that does. 2. The method according to claim 1, wherein the metal oxide is an oxide selected from silicon, titanium, tungsten, boron, aluminum, zirconium, hafnium, niobium, molybdenum, tantalum, chromium and vanadium. Carbon composition. 3. The metal oxide is selected from oxides of silicon, boron and aluminum, and the specific surface area (b) corresponding to carbon and the specific surface area (c) corresponding to metal oxide are both 150 m ² / g or more. The carbon-containing composition according to claim 1.