JPS62278166A - Manufacture of composite metal carbide sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Prior Art] The present invention relates to a novel method for producing a composite metal carbide sintered body. More specifically, the present invention relates to a method for manufacturing a composite metal carbide sintered body mainly composed of silicon carbide.

[Cost technology]

Ceramic sintered bodies obtained from fine powdered silicon carbide have superior mechanical strength at high temperatures compared to conventional metal materials, and are therefore expected to be used in engines, gas turbines, etc.

Such a sintered body of silicon carbide is produced by adding a small amount of a sintering agent such as boron or carbon to a fine powder of silicon carbide, uniformly mixing the mixture, cold-opening it, and then heating it for 1900 minutes in a non-oxidizing atmosphere. A method of heating to ~2200°C is known (for example, Japanese Patent Publication No. 5.7-32035, Japanese Patent Publication No. 57, No. 57).
-40109, Special Publication No. 59-34147).

However, the ceramic sintered bodies obtained by such a method have too large a variation in mechanical strength and lack complete reliability, which is an obstacle to industrial practical application.

[Disclosure of the invention]

As a result of extensive research aimed at solving the above problems and manufacturing ceramic sintered bodies with high mechanical strength (and small variations in strength), the inventors of wood have developed a method for producing ceramic sintered bodies with a specific amount of carbonization in silicon carbide as a raw material. The present invention has been completed based on the discovery that the above object can be achieved by using a composite metal carbide fine powder containing titanium, adding and mixing a sintering aid thereto, and then sintering the powder.

That is, the method for producing a ceramic or resintered body of the present invention is a metal carbide fine powder (hereinafter referred to as composite metal carbide) containing 70% by weight or more and less than 95% by weight of silicon carbide and 5% by weight or more and less than 30% by weight of titanium carbide. 0.1 to 4.0 parts by weight of elemental boron or a boron compound corresponding to elemental boron and 0.5 to 4.0 parts by weight of elemental carbon were added to 100 parts by weight (referred to as fine powder). In particular, fine powder of composite metal carbide is injected with decomposable silicon compounds, decomposable titanium compounds, and decomposable carbon compounds into hot gas containing water vapor and decomposed. C/(Si
+4i) A composite metal carbide sintered body obtained by heating a carbon-containing composition having a formula weight ratio of greater than 3.5.

In the present invention, silicon carbide and titanium carbide in the composite metal carbide fine powder are, of course, preferably mixed uniformly and in a state that corresponds to a "composition" as defined in the "General Examination Standards", and their specific surface area is preferably a fine powder of about 3 to 50 m/g. If the specific surface area of the composite metal carbide fine powder is less than 3 m/g, the sintering driving force of the composite metal carbide fine powder will be insufficient, making it difficult to obtain a dense sintered body. On the other hand, if the powder is very fine and has a specific surface area of more than 50 i/g, a problem arises in that it is difficult to increase the density of the cold-formed product before sintering. Note that the specific surface area referred to herein is the nitrogen adsorption specific surface area (measured by the so-called BET method), and it goes without saying that a large value generally indicates a small particle size. The composite metal carbide fine powder in the present invention can also be obtained by mixing or pulverizing powders of fil silicon carbide and titanium carbide in a ball mill, vibration mill, etc.; A carbon-containing composition obtained by the method proposed by the present inventors in JP-A-59-49828, that is, a decomposable metal compound (i.e., a decomposable silicon compound and a decomposable titanium compound) in a hot gas containing water vapor. A decomposable carbonized compound is injected and decomposed to generate a mixed aerosol dispersoid containing aerosols of the metal oxide and elemental carbon, and the carbon composition obtained by collecting the nucleated dispersoid is heated. It is also possible to obtain a composite metal carbide. And the latter is more preferred.

Application of the method for producing a carbon-containing composition disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-49828 to the method for obtaining a composite metal carbide in the present invention will be described in detail.

Steam To obtain the composite metal carbide of the present invention by the method disclosed in JP-A-59-49828, it is first necessary to obtain a carbon-containing composition, which is decomposable in hot gas containing water vapor. Injecting and decomposing a silicon compound, a decomposable titanium compound, and a decomposable carbon compound to generate a mixed aerosol containing silicon oxide, titanium oxide, and elemental carbon,
It can be obtained by collecting the generated dispersoids.

As degradable silicon compounds and degradable titanium compounds,
Among silicon or titanium halogen compounds, alkyl compounds, alkoxide compounds, acid ester metals, etc., those that easily undergo thermal decomposition, oxidation, or hydrolysis in hot gas containing water vapor to become silicon oxides or titanium oxides. It is.

Examples of such decomposable compounds include: 5iC1a, CH35iC1
z, (CHz)i, 5ich, (CH3)zsicl
, (CHz)zsiSH5iCh, HzSiCh,
)13SiC1-SiH4, SiF4.5iHzF2.
5iJ6, SiJ, etc., and decomposable titanium compounds include; TiC1n, TiBr4, Ti1a, TiF
a, TiH4, Ti(OCzHs)*, (I(3TiC
Preferred examples include compounds such as h, CJzTiCIz, but as mentioned above, the compound is not limited to these as long as it is decomposable in hot gas containing water vapor.

The decomposable carbon compound used in the practice of the present invention is one that can easily decompose and produce elemental carbon (soot) when charged into a hot gas as described later, and can be left in the gas phase as it is. Alternatively, those in a liquid phase state or those that can be easily turned into a liquid phase state by increasing temperature can be suitably used.6 For example, LPG,
Petroleum products such as naphtha, gasoline, fuel oil, kerosene, light oil, heavy oil, lubricating oil, liquid paraffin; methane, ethane,
Propane, butane, pentane, methanol, ethanol, proptool, ethylene, acetylene, n-paraffin, butadiene, isoprene, isobutylene, benzene, toluene, xylene, cyclohexane, cyclohexene, dicyclopentadiene, ethylbenzene, styrene, cumene, pseudocumene , mesitylene, alkylbenzene, α, methylstyrene, dicyclododecatriene, diisobutylene, vinyl chloride, chlorobenzene, C
Petrochemical products such as 9 distillate mixtures and ethylene bottoms; Tar products such as tar, pitch, creosote oil, naphthalene, anthracene, carbazole, tar acid, phenol, cresol, xylenol, pyridine, picoline, and quinoline; soybean oil, Coconut oil, linseed oil, cottonseed oil,
Preferred examples include oils and fats such as rapeseed oil, tung oil, castor oil, whale oil, beef tallow, squalane, oleic acid, and stearic acid, but are not limited thereto.

Since the decomposable carbon compound used in carrying out the present invention has the purpose of supplying carbon, it can be selected from a wide range of options, such as those listed above.However, from the viewpoint of ease of handling and carbon yield, Toluene, which has a relatively high carbon content,
Particularly preferred are xylene, Hensen, kerosene, light oil, heavy oil, C9 distillate mixture, ethylene bottoms, and the like.

Hot gas containing water vapor can also be obtained by injecting water vapor into hot gas obtained by an electric heating method, a high frequency heating method, or a discharge method. The method of using air to combust combustible materials that produce water vapor when burned, such as hydrocarbons used as raw materials, can obtain hot gas containing water vapor in one step, making it simple in terms of equipment and economical in terms of thermal efficiency. It is.

In order to obtain the carbon-containing composition, it is convenient to use a furnace as shown in FIG.

The mixed aerosol dispersed in the hot gas thus obtained is guided outside the furnace, and the solids contained are separated into solids and gases using a known collection device such as a barb filter, cyclone, or electrostatic precipitator. Collect by operation.

In the present invention, the content of silicon carbide in the composite metal carbide fine powder may be 70% by weight or more and less than 95% by weight Mχ (hereinafter, % by weight is expressed as %), and the content of titanium carbide may be 5% or more and less than 30% by weight. Preferably, when the composite metal carbide fine powder is obtained from the carbon-containing composition, the amount of the content can be adjusted by
This can be easily carried out by adjusting the amounts of the decomposable silicon compound and the decomposable titanium compound injected into the hot gas containing water vapor.

In the present invention, C/(Si+Ti in the carbon-containing composition)
) bulk ratio, i.e. C(g-atm)/(Si+Ti
) The ratio of (g-atm) is desirably greater than 3.5 (0M), and the carbon-containing composition containing an excess of carbon is better than the composite metal carbon compound fine powder obtained by heating it. This is based on the inventors' experimental findings that the average particle diameter of the particles becomes smaller. However, if the value of and is too large, such as exceeding 20, no more significant effect can be obtained, and the result is only a mere loss of the carbon compound. C/(Si+Ti) mass ratio is preferably 3.5
It is 4 or more and less than 10, more preferably 4 or more and less than 10.

The thus obtained carbon-containing composition consisting of a silicon compound, a titanium compound, and elemental carbon is heated as it is or in an inert gas such as argon or helium in a high-frequency heating furnace, an Acheson type direct current resistance furnace, etc. ,1
600-2100℃, preferably 1700-1900℃
If heat is generated to a certain extent, composite metal carbide fine powder can be obtained using the following equations (1) and (2).

SiO□+3C= SiC+ 2CO−・−・・・・
−・il+TiO□+3C→ TiC÷2CO−・・−
---- (2) However, the elemental carbon contained in the carbon-containing composition has a C/(Si+Ti) formula weight ratio of 3.5
Since a larger amount is desirable, a stoichiometric excess of carbon is included over the amount that would produce silicon carbide and titanium carbide according to the above formula. Therefore, an excess of elemental carbon remains in the composite metal carbide fine powder produced here.
By heating to 00°C, elemental carbon can be easily burned off.

Next, a method for manufacturing a ceramic sintered body from the composite metal carbide fine powder thus obtained will be described.

As described in the background art section, the method for producing a composite metal carbide sintered body from composite metal carbide fine powder in the present invention can be applied to methods commonly used in the ceramic industry and known per se.

That is, a fine powder obtained by mixing a small amount of elemental boron or a boron compound corresponding to elemental boron and elemental carbon with a composite metal carbide fine powder is formed into a desired shape by a method such as pressure molding or casting, and then 1900~ 2200°
A sintered body can be obtained by heating to about C. As a sintering method, methods such as hot pressing, hot isostatic pressing (HIP), etc. can of course be adopted, but the method of heating at a pressure below atmospheric pressure, the so-called atmospheric pressure sintering method, is the most widely used in the industry. It is advantageous. The atmosphere during heating is preferably an inert gas such as argon or nitrogen, or a vacuum.

In the present invention, the specific surface area of the composite metal carbide fine powder is 3 to 5.
As mentioned above, fine powder of about 0 m/g is preferable.

In the present invention, there are basically two methods for obtaining the composite metal carbide fine powder as described above.

That is, the first method is to mix or pulverize powders of silicon carbide and titanium carbide in a ball mill, vibration mill, etc., and the second method is to obtain decomposable metals in hot gas containing water vapor. A compound (i.e., a decomposable silicon compound and a decomposable titanium compound) and a decomposable carbon compound are charged and decomposed to produce an aerosol dispersoid containing an aerosol of each of the metal oxide and elemental carbon, and This method collects the dispersoids and heats the carbon-containing composition.

The present inventors have confirmed that the effects of the present invention are even more remarkable when the composite metal carbide fine powder obtained by the second method of these two methods is used. The composite metal carbide fine powder of the present invention has a composition mainly composed of silicon carbide and also contains a specific titanium carbide. % or more and less than 30χ as described above. The reason for this is that if the titanium carbide content is less than 5χ, the state will be similar to that of a fine powder of silicon carbide alone, making it impossible to obtain the effects of the present invention, while if it is more than 30%, it will be difficult to obtain a delicate sintered body. To become.

In the present invention, prior to sintering, it is preferable to add and mix a small amount of elemental boron or a boron compound corresponding to elemental boron and elemental carbon to the composite metal carbide fine powder as a sintering aid to promote sintering. The amount of the former is approximately 0.1 to 4.0 parts, and the latter is approximately 0.1 to 4.0 parts by weight, per 100 parts by weight of the composite metal carbide fine powder (hereinafter, parts by weight are referred to as parts).
It is about 5 to 4.0 parts. For its purpose, it is desirable that the sintering aid be mixed with the composite metal fine powder as uniformly as possible. Therefore, the specific surface area of the car body boron or boron compound should be 3 m/g or more, and the specific surface area of the elemental carbon should be 30 m/g. For example, fine powders such as carbon black, resin, and acetylene black are preferred.

Mixing is carried out using a ball mill, vibration mill, etc., but in order to obtain a more homogeneous mixture, water or an organic solvent such as methanol or ethanol is added and a wet steam ball mill, vibration mill, etc. is used. A method of mixing is preferred. That is, one method is to disperse and suspend elemental boron or a boron compound fine powder in water or an organic solvent, mix this suspension with a composite metal carbide fine powder, and then remove the water or the III-i8 medium by evaporation. There is a way.

Another method is to add and mix water or an organic solvent to elemental boron or boron compound fine powder, elemental carbon fine powder, and composite metal carbide fine powder, and then remove the water or organic solvent by evaporation. In the present invention, either method can be adopted. In addition, the above-mentioned boron compounds corresponding to elemental boron that can be used in the present invention include BtC-BN,
A4B, etc. are mentioned as preferred bases.

[Function and effect of the invention]

As explained in detail above, the method for producing a composite metal carbide sintered body of the present invention is a method for producing a metal carbide mainly composed of silicon carbide and to which a specific amount of titanium carbide is added (composite metal carbide@ff
) A method in which fine powder is sintered in the presence of a sintering aid, and in particular, the composite metal carbide fine powder is mixed with decomposable silicon compounds, decomposable titanium compounds, and C/(
Composite metal carbide obtained by heating a carbon-containing composition whose formula weight ratio (Si+Ti) is greater than 3.5! Although it is a fine powder, the ceramic sintered body obtained by practicing the present invention has high mechanical strength and has extremely small variations in strength. The detailed reason why such an excellent sintered body can be obtained is, of course, not clear at present, but the inventors of the present invention speculate as follows.

According to the theory or common theory currently generally believed in the ceramic industry, in order for a ceramic sintered body to have high mechanical strength and small variation in strength, (1
) It is required that there are no defects left during molding inside the sintered body, and (2) that the size of each particle constituting the sintered body is uniform and fine. Ru.

It is presumed that the effect of the present invention is mainly due to the latter, and this can also be confirmed by examining the structure of the particles constituting the sintered body using an S8M photographic image. That is, when comparing the 52M images of the sintered body obtained by the method of the present invention and the sintered body obtained by the conventional manufacturing method, it is found that the sintered body obtained by the present invention is superior to the conventional sintered body. It is confirmed that the sintered body has a much finer structure than that of the sintered body. Although it is not necessarily clear why such a fine structure is formed, the present inventors speculate as follows.

Therefore, as mentioned above, the ceramic sintered body obtained by the present invention is not only a single fine powder of silicon carbide, but also a composite metal carbide fine powder made mainly of silicon carbide with the addition of titanium carbide. During the sintering process, the composite metal carbide is heated and the single particles are combined and densified, and the evenly dispersed titanium carbide particles are mixed with the Tohoku silicon particles. It is presumed that this is not because it has a so-called pinning effect to prevent enlargement. In addition, in the present invention, the composite metal carbide fine powder contains silicon oxide, titanium oxide, and carbon by injecting and decomposing decomposable silicon compounds, decomposable titanium compounds, and decomposable carbon compounds into hot gas containing water vapor. A composite metal carbide fine powder produced by generating a mixed aerosol and heating a carbon-containing composition having a C/(Si+Ti) formula weight ratio of greater than 3.5, which was obtained by heating the dispersoid. At times, the effects of the present invention are even more remarkable. The reason is that the composite metal carbide fine powder obtained by the above method has silicon carbide powder and titanium carbide powder mixed evenly, so that the dispersion of titanium carbide in the composite metal carbide fine powder is reduced. This is thought to be due to the fact that it is even better.

[Preferred Mode for Carrying Out the Invention] The present invention will be explained in more detail with reference to Examples below.

Example 1 90 g of silicon carbide with a specific surface area of 1.2i/H and a specific surface area of 0
．． 9 m/g of titanium carbide was pulverized and mixed for 50 hours using a vibration mill to obtain 100 g of composite metal carbide fine powder with a specific surface area of 15.1' m 7 g. In this composite metal carbide fine powder, B, C fine powder 1 with a specific surface area of 5.3 m/g is added.
, 5g and a carbon block with a specific surface area of 120.5 resistance/g.
2.0 g of YTSU and 50 cc of ethanol were added and mixed under wet conditions for 20 hours to obtain composite metal carbide fine powder and a mixture thereof. The resulting mixture was heated to remove ethanol by evaporation, and 80 g of the fine powder obtained was placed in a cylindrical container.
After being compressed on the l-axis under a load of 0.57/d, it was rubber pressed and molded under a hydrostatic pressure of 2 T/cJ. Next, ``10 pieces of this molded body
-1 to 2050°C in a nitrogen atmosphere under a true room of Toor
, and heated for 30 minutes to obtain a composite metal carbide sinter. The density of this sintered body was measured and was found to be 3.30 g/cc φ Next, this sintered body was cut with a diamond cutter to create 20 test pieces, which were bent at room temperature according to the method of JIS R-1601. The strength was measured. As a result, the average value of bending strength was 63Kg/+n+'' and the standard deviation was 4.6Kg/mm.
”Azuta.

Comparative Example 1 Silicon carbide 1
00g was ground in a vibration mill for 50 hours and the specific surface area was 16.
3rd7g of silicon carbide fine powder was obtained.

B-C, carbon blank, and ethanol were added and mixed to this fine powder in exactly the same manner as in Example 1.

This mixture was molded and heated in the same manner as in Example 1.
．． A silicon carbide sintered body having a density of 14 g/cc was obtained. Twenty test pieces were made from this sintered body and the bending strength was measured in exactly the same manner as in Example 1. As a result, the average value was 57 kg/1
The lI112 standard deviation was 5.0 Kg/approximately 1. The internal structure of this sintered body was analyzed using Sεh photographic images.

Example 2 Using the carbon-containing composition manufacturing apparatus 2 shown in FIG.
Burn more air than burner 3 and propane each 11
A flame was generated by charging at a flow rate of 00 N'/h and 2 Nm/h. Also, as a decomposable silicon compound, SiC'l
TiCl4 was selected as the decomposable titanium compound, and heavy oil was selected as the decomposable carbon compound, and these were mixed in advance at a weight ratio of 1:0.084:2, and 30
It was injected into the furnace at a flow rate of Kg/h.

The obtained aerosol was guided to the outside of the thread through the duct 6, and the dispersoids in the aerosol were collected to obtain a carbon-containing composition consisting of silicon oxide and titanium oxide at a production rate of 10.61 g/h. The carbon-containing composition is SiO□32.2'g, T10
□3.2χ, carbon 64.1χ, and the carbon (Si+Ti) weight ratio was 9.3.
g was heated at 1750°C for 2 hours using a high-frequency heating furnace,
Once cooled, it was heated to 600° C. in air to burn off the remaining carbon, and then washed with an aqueous hydrofluoric acid solution to obtain 115 g of composite metal carbide.

This composite metal carbide contained 89x silicon carbide and 11x titanium carbide, and had a specific surface area of 14.7 m7g. To 100 g of this composite metal carbide, add 1.5 g of B and C fine powders, 2.0 g of carbon blank, and 50 cc of ethanol in exactly the same manner as in 1] and heat them under wet conditions for 20 hours. R matched.

This mixture was heated to remove ethanol, molded, and burned in exactly the same manner as in Example 1, and the density was 3.31 g/c.
A sintered body of composite metal carbide of c was obtained.

Twenty test pieces were made from this sintered body in exactly the same manner as in the example work, and the bending strength was measured, and the average value was 721.
[g/mm", standard deviation was 3.0 Kg/mm". The internal ML texture of this sintered body was analyzed using Sεi photographic images, and it was found that the sintered structure was much finer than that of Comparative Example 1. It was confirmed that it was a solid body.

A comparison of Example 1 and Comparative Example 1 shows that a sintered body with high strength and small variation can be obtained by following the method of the present invention, and a comparison between Example 1 and Example 2 shows that a composite metal carbide It can be seen that the effect of the present invention becomes even more remarkable when a fine powder obtained by heating a carbon-containing composition obtained via an aerosol is used. Furthermore, as mentioned above, from the comparison of the Sε gate photographic images, it was found that the internal structure of the sintered body obtained in Example 2 was much finer than that of the sintered body obtained in Comparative Example 1. It is presumed that the fineness of this internal M weave causes a significant difference in the strength and variation of the sintered bodies.

Production Examples 1 to 4 Four types of composite carbide fine powders were produced by the following method. That is, in the same manner as in Example 2, the manufacturing 'AK' shown in FIG.
air from duct 2 and propane from combustion burner 3 at 10100N/h and 2Nll+3/h, respectively.
A flame was generated by charging at a flow rate of . The decomposable silicon compounds, decomposable titanium compounds, and carbon compounds shown in Table 1 were used, and were injected into the furnace at the injection amounts and nozzle positions shown in Table 1. Here, the same injection nozzle number means that the ingredients are mixed in advance and injected from the same nozzle. That is, in Production Example 1, 5icl# was injected from the nozzle 4, and Tt(OC
Hs)- and ethylene bottoms mean that they were mixed in advance and injected from the nozzle 5, and in Production Example 2, it means that the three types of compounds were mixed in advance and injected from the same nozzle 4.

The obtained aerosol was guided to the outside of the yarn through the duct 6, and carbon-containing compositions having the production amounts and composition C/(Si+Ti) weight ratio shown in Table 1 were obtained. 500 g of each of these carbon-containing compositions was heated at 1750°C for 2 hours using a high-frequency heating furnace in the same manner as in Example 1, and composite metal carbide fine powders having the compositions and specific surface areas shown in Table 1 were obtained. Each product was obtained in the amount shown in Table 1.

Examples 3 to 10 Using the composite metal carbide fine powders obtained in Production Examples 1 to 4, to 100 g of each of these, boron compounds and car body carbon having the name, specific surface area, and amount shown in Table 2 were added, Furthermore, 50 cc of Kotanol was added and mixed in a vibration mill for 20 hours. Each of these mixtures was heated to remove ethanol, and 80 g of fine powder was molded and heated in exactly the same manner as in Example 1.
A sintered body with a density shown in was obtained.

Using the obtained sintered body, the bending strength was measured in exactly the same manner as in Example 1. The results were as shown in Table 2.

From the bending strength shown in Table 2, it can be seen that if the zero-starting method is followed, a sintered body with high strength and small variation can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an apparatus for producing a carbon-containing composition used in Example 2 and Production Examples 1 to 4. In the figure, 1, ...------- ... Furnace material 2. ---
-------Duct 3,...--1---Combustion burner 4. −・−・・−・−・−Nozzle 5,・
・−・・−−−−−−Nozzle 6.・・・－・・
......indicates a duct.

Claims (2)

[Claims] (1) 100 parts by weight of metal carbide fine powder (hereinafter referred to as composite metal carbide fine powder) consisting essentially of 70% by weight or more and less than 95% by weight of silicon carbide and 5% by weight and less than 30% by weight of titanium carbide, 0.1 to 4.0 parts by weight of elemental boron or a boron compound equivalent to elemental boron and 0.5 parts by weight
1. A method for producing a composite metal carbide sintered body, which comprises adding 4.0 parts by weight of elemental carbon and then sintering. (2) A composite metal carbide fine powder consisting essentially of silicon carbide and titanium carbide is made by injecting and decomposing a decomposable silicon compound, a decomposable titanium compound, and a decomposable carbon compound into hot gas containing water vapor, and A mixed aerosol containing oxide, titanium oxide, and elemental carbon was generated, and the generated dispersoid was collected to obtain a C/(Si+Ti) formula weight ratio of 3.
Claim 1, characterized in that it is a composite metal carbide fine powder obtained by heating a carbon-containing composition having a carbon content larger than 5.
The method described in section.