JPH0481521B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a mixed powder of boron nitride and other ceramic powder. For more details,
A non-oxide ceramic powder other than boron nitride and boron or a boron compound are mixed so that the mixed powder of boron nitride and non-oxide ceramic powder contains 95 to 10% by weight of the non-oxide ceramic powder. production of a mixed powder of boron nitride and other non-oxide ceramics, characterized in that the mixture is brought into contact with nitrogen or a nitrogen compound to nitride boron or a boron compound and convert it into boron nitride. Regarding the method. (Conventional technology) Boron nitride has heat resistance, electrical insulation, lubricity,
Because it has excellent properties such as chemical resistance and thermal conductivity, it is used in powder form or in the form of molded bodies such as crucibles in various fields that utilize these properties. Attempts have been made to improve the characteristics of various ceramics by mixing such boron nitride with the ceramics. For example, attempts have been made to improve the friction and wear characteristics of silicon nitride sintered bodies by mixing boron nitride with silicon nitride. In this way, mixed powders of boron nitride and various ceramic powders are beginning to be used in various ways, including as raw materials for composite sintered bodies. The above-mentioned mixed powder of boron nitride and various ceramic powders is conventionally produced by separately synthesizing boron nitride powder and various ceramic powders, and then combining the obtained boron nitride powder and various ceramic powders using known methods. A manufacturing method that involves mixing by means is generally used. (Problem to be solved by the invention) However, commercially available boron nitride powders are generally crystal grains with a developed hexagonal crystal habit, and their shape is irregular because they are plate-like particles reflecting the crystal shape. The orientation is very large. Further, the above-mentioned boron nitride powder generally has the property that the primary particles tend to aggregate to form large aggregate particles. Therefore, it has been difficult to obtain a mixed powder in which boron nitride powder and various ceramic powders are uniformly dispersed by mixing the boron nitride powder and various ceramic powders. If both boron nitride powder and various ceramic powders are not uniformly dispersed, depending on each case, the sinterability of the mixed powder may be poor or
Various disadvantages occur, such as the physical properties of the composite sintered body obtained by sintering the mixed powder are not improved to that extent. (Means for Solving the Problems) In view of the above circumstances, the present inventors conducted intensive research to obtain a mixed powder in which boron nitride powder and various ceramic powders were uniformly dispersed, and as a result, various ceramic powders were obtained. Boron nitride synthesized in the presence of
We have discovered that the boron nitride powder of various ceramic powders is uniformly dispersed or the surface of the ceramic powder is coated with boron nitride,
We have now completed the present invention. That is, in the present invention, a non-oxide ceramic powder other than boron nitride and boron or a boron compound are mixed in a mixed powder of boron nitride and non-oxide ceramic powder so that the non-oxide ceramic powder is 95 to
Boron nitride and other non-oxides are mixed to contain 10% by weight, and the mixture is brought into contact with nitrogen or a nitrogen compound to nitride boron or the boron compound and convert it to boron nitride. This is a method for producing a mixed powder with ceramics. The present invention will be explained in more detail below. One of the raw materials used in the present invention is boron or a boron compound. Among these, boron is a simple substance of boron, and both crystalline and amorphous forms can be used. Moreover, any known substance can be used as the boron compound without particular limitation. In general, boron, boron oxide, borates, boron halides, metal borides, etc. can be suitably used in the present invention. Among these, as the borate, ammonium borate, borax, potassium borate, lithium borate, calcium borate, magnesium borate, etc., ammonium salts of boric acid, alkali metal salts, alkaline earth metal salts, zinc borate, etc. can be preferably used. . As the boron halide, boron trichloride, boron trifluoride, boron tribromide, etc. can be suitably used, and as the metal boride, calcium boride, etc. can be suitably used. As the nitrogen and nitrogen-containing compound which are one of the raw materials used in the present invention, known substances used in the production of boron nitride can be used without particular limitation. Among these, ammonia, urea, ammonium chloride, dicyandiamide, melamine, etc. can be preferably used as the nitrogen-containing compound. The ceramic powder used in the present invention is not particularly limited as long as it is a non-oxide ceramic powder other than boron nitride, and any known ceramic powder can be used. The non-oxide ceramic powder preferably used in the present invention has the following general formula MmXn (where X is one selected from the group consisting of boron, nitrogen, silicon and carbon, and M is aluminum, boron 1 selected from the group consisting of elemental elements, silicon, beryllium, rare earth elements, and refractory transition metals.
It is a species other than X, m represents the valence of X, and n represents the valence of M. ). The term "refractory transition metal" as used herein refers to transition metals in Groups 4, 5, and 6 of the periodic table, namely titanium, zirconium, hafnium, thorium, vanadium, niobium, and tantalum. , meaning protactinium, chromium, molybdenum, tungsten and uranium. Suitable ceramic powders in the present invention include, for example, aluminum nitride, silicon nitride, silicon carbide, titanium boride, aluminum boride,
Zirconium boride, titanium nitride, boron carbide,
etc. can be suitably used. It is desirable that these ceramic powders have small particle sizes and high purity. Generally, it is preferable that the average particle diameter of the ceramic powder is 5 μm or less, and that the content of impurities (including anion and cation impurities) is 5% by weight or less. When such a ceramic powder is used, the boron nitride mixed powder containing the ceramic powder obtained by the present invention has good sinterability. Alternatively, the effects of the present invention can be clearly exhibited, such as the composite sintered body obtained from the boron nitride mixed powder has excellent properties. In particular, it is preferable to use aluminum nitride powder as the ceramic powder because the composite sintered body obtained using the boron nitride mixed powder as a raw material has excellent thermal conductivity. Preferred aluminum nitride powders include the following. The average particle diameter (refers to the average particle diameter of aggregated particles measured using a centrifugal particle size distribution analyzer, for example, CAPA500 manufactured by Horiba) is 5 μm or less, and preferably
Powders of 3 μm or less, most preferably 2 μm or less are preferred. Particularly suitable is a powder containing 70% by volume or more of particles of 3 μm or less. In addition, when obtaining a composite sintered body with high thermal conductivity, aluminum nitride powder with an AlN content (calculated from the nitrogen content of AlN powder) of 90% by weight or more is preferably used, and even 94% by weight or more is used. weight%
As mentioned above, powder of 97% by weight or more is more preferably employed. The aluminum nitride powder preferably used in the present invention has an average particle diameter of 2 μm or less, contains 70% by volume or more of particles of 3 μm or less, has an oxygen content of 3.0% by weight or less, and has an aluminum nitride composition. When is AlN, the cationic impurity contained is
Aluminum nitride powder containing 0.5% by weight or less. When such aluminum nitride powder is used, it is preferably used in the present invention because it can improve the thermal conductivity of the resulting composite sintered body and suppress a decrease in mechanical strength at high temperatures. In particular, powders with an average particle diameter of 2 μm or less, and particles of 3 μm or less
Contains 70% by volume or more, oxygen content 1.5% by weight or less,
In addition, when using aluminum nitride powder containing 0.3% by weight or less of cationic impurities when the aluminum nitride composition is AlN, the resulting composite sintered body has improved thermal conductivity and mechanical strength at high temperatures. It is particularly preferably used in the present invention because it has a remarkable effect of suppressing the decrease in . As a method for reacting boron or a boron compound with nitrogen or a nitrogen-containing compound described above, any known method can be employed without any restriction.
Examples of such known reaction methods include the following methods. 1 A method of directly reacting elemental boron with nitrogen or ammonia. In this case, in order to make the reaction proceed quickly,
It is best to heat it to 1500℃ or higher. 2. A method of heating raw materials such as boric acid, boron oxide, or borate in a nitrogen or ammonia stream. In this case, boric acid, etc. dissolves when heated and becomes a viscous liquid, which inhibits the reaction with ammonia gas. Therefore, in an industrial setting, a filler such as calcium phosphate is usually added to boric acid, etc., and the boric acid, etc. melts and becomes a viscous liquid. React with ammonia gas in such a way that it thinly covers the surface. After the reaction is completed, the filler is dissolved and removed using hydrochloric acid or the like to separate boron nitride. 3. A method in which a mixture of borate or boric acid, etc. and a nitrogen-containing compound such as urea is heated in a nitrogen or ammonia stream. 4. A method in which a reducing agent such as carbon or magnesium is added to boric acid or boron oxide, and the mixture is reacted in ammonia or nitrogen. 5. A method of obtaining boron nitride by synthesizing a compound such as an imide from a boron halide such as boron trichloride and ammonia and thermally decomposing the compound. Among these methods, methods 1) to 4) and 5)
This method will be divided into two methods and will be explained in more detail below. To explain methods 1) to 4), first, boron or a boron compound and non-oxide ceramic powder are mixed. This mixing ratio can be selected from a wide range depending on the properties required of the boron nitride mixed powder containing the non-oxide ceramic powder produced according to the present invention. In order for the effect of the uniformity of the boron nitride mixed powder obtained by the method of the present invention to clearly appear, generally, boron or a boron compound must be contained in an amount of 5 to 95% by weight in terms of boron nitride, and non-oxide ceramics Preferably, the powder is in the range 95-5% by weight. Furthermore, it is more preferable that the boron or boron compound is 10 to 90% by weight in terms of boron nitride, and the non-oxide ceramic powder is 90 to 10% by weight. However, when using method 2) or 4),
In order to improve the air permeability of nitrogen or nitrogen-containing compounds in the raw material mixture and to advance the nitriding reaction of boron or boron compounds, the amount of non-oxide ceramic powder is preferably 40% by weight or more. In the present invention, components such as a predetermined nitrogen-containing compound or reducing agent are further mixed according to methods 1) to 4). In addition, in method 2), boron or a boron compound is dissolved by heating and turns into a liquid, which inhibits the reaction with nitrogen or nitrogen-containing compounds, so a filler such as calcium phosphate is usually added to carry out the reaction. However, in the case of the present invention, the added non-oxide ceramic powder plays the role of a filler, so it is not necessarily necessary to add a filler such as calcium phosphate. The method of mixing boron or a boron compound, non-oxide ceramic powder, and nitrogen-containing compound or reducing agent added as necessary is not particularly limited, and may be any known method such as dry mixing or wet mixing in a liquid dispersion medium. You can use this method. A particularly preferred embodiment is wet mixing. The liquid dispersion medium is not particularly limited, and generally water, alcohols, hydrocarbons, or mixtures thereof are preferably used. In particular, lower alcohols having 4 or less carbon atoms, such as methanol, ethanol, and butanol, are most preferably employed industrially. Further, the mixing conditions and equipment are not particularly limited, and any suitable one can be used as long as it can suppress unavoidably mixed impurity components. The mixture thus obtained may be used as it is or, if necessary, dried. The shape of the mixture when subjected to the next nitriding reaction may be in powder form, or may be formed into pellet form or block form. The mixture thus obtained is then calcined in an atmosphere of nitrogen or a nitrogen-containing compound. The firing temperature varies depending on the type of ceramic powder, but is generally preferably in the range of 700°C to 1500°C. It is usually sufficient to select the firing time from the range of 2 to 12 hours. During the firing, it is preferable to take care to ensure that the materials of the firing furnace and the firing boat do not cause impurities. In addition, the firing atmosphere is preferably an atmosphere containing ammonia, usually pure ammonia gas or a gas in which nitrogen gas is added to it.Usually, these reaction gases are added continuously or in an amount sufficient for the nitriding reaction to proceed. It is best to bake while feeding intermittently. Next, method 5) will be explained. Add non-oxide ceramic powder to liquid ammonia. The amount of non-oxide ceramic powder added is such that the proportion of the resulting boron nitride mixed powder is 5 to 95%.
The weight percent is preferably selected to be 10 to 90 weight percent. A boron halide such as boron trichloride is added dropwise while uniformly dispersing the non-oxide ceramic powder by a method such as stirring. The resulting slurry of boron imide and non-oxide ceramic powder is filtered with stirring and dried.
Note that the above reaction operation is desirably carried out in a dry atmosphere, for example in a nitrogen gas atmosphere. This is because boron halides such as boron trichloride and boron imide which is a reaction product easily react with water and decompose. The mixture of boron imide and non-oxide ceramic powder obtained as described above is heated at a temperature of 800 to 1200°C in a nitrogen or ammonia gas atmosphere,
A mixture of boron nitride and non-oxide ceramic powder is obtained by thermally decomposing boron imide. If necessary, the crystallinity of boron nitride can be increased by further heating the boron nitride mixed powder obtained as above at a temperature of 1200 to 1700°C in a non-oxidizing atmosphere such as nitrogen gas. be able to. In the manner described above, a boron nitride mixed powder in which various non-oxide ceramic powders and boron nitride powder are uniformly dispersed can be obtained. The boron nitride mixed powder containing various non-oxide ceramic powders obtained by the present invention can be used as it is by adding it to other substances in powder form, and can also be used as a raw material for composite sintered bodies. can. When used as a raw material for a composite sintered body, the boron nitride mixed powder containing various ceramic powders obtained by the present invention can be used as it is or mixed with a sintering aid and sintered to form a composite sintered body. Obtainable. Hereinafter, the case where the boron nitride mixed powder of the present invention is used as a raw material for a composite sintered body will be explained in more detail. First, the sintering aid is not particularly limited and any known one may be used, but it may generally be selected from boron nitride and materials suitable for sintering the ceramic powder used. For example, when the ceramic powder is aluminum nitride powder, a compound of a metal of group a or group a of the periodic table is suitable as the sintering aid. More specifically, nitrates, carbonates, halides, aluminates of beryllium, calcium, strontium, barium, yttrium, lanthanum, cerium, neodymium, etc.
Oxides and the like are preferably used. Further, when the ceramic powder is silicon nitride, an oxide of a metal of group a or group a of the periodic table such as magnesia, alumina, or ittria, and when the ceramic powder is silicon carbide,
Carbon and metallic boron are preferably used as sintering aids. Furthermore, the amount of the sintering aid used varies depending on the composition of the composite sintered body, the properties required of the composite sintered body, etc., and the appropriate amount to be used in each case must be determined in advance. All you have to do is decide. Generally, it is suitable to use the sintering aid in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the ceramic powder. Further, sintering aids such as boron oxide and calcium oxide, which are preferably used for sintering boron nitride, are also preferably used in the same range as above for boron nitride. The method of mixing the boron nitride mixed powder and the sintering aid is not particularly limited, and any known method may be used. For example, a wet mixing method can be suitably used,
It is also possible to employ a dry mixing method that does not use a liquid dispersion medium. Further, the mixing device is not particularly limited, and any known mixing device may be used as is. As a method for dispersing the sintering aid into the boron nitride mixed powder, in addition to the method described above, the sintering aid is mixed with the raw material before synthesizing the boron nitride mixed powder, and then the nitriding It is also possible to adopt a method of synthesizing a boron mixed powder and dispersing it into a boron nitride mixed powder. Sintering can be carried out in vacuum or under non-oxidizing atmosphere under pressure or normal pressure. When applying pressure, it is preferable to select a pressure of 20 to 500 kg/cm ² . As the non-oxidizing atmosphere, for example, nitrogen gas, argon gas, hydrogen gas, or a mixed gas atmosphere thereof is used. The sintering temperature varies depending on the composition of the composite sintered body, so it is best to determine the optimal sintering temperature for each case in advance, but generally it is between 1500 and 2300℃.
temperature is adopted. (Effects) According to the manufacturing method of the present invention, a mixed powder in which boron nitride and non-oxide ceramic powder are uniformly dispersed, which cannot be achieved by the conventional method of mixing boron nitride powder and non-oxide ceramic powder, can be obtained. In this method, a ceramic powder whose surface is coated with boron nitride is obtained. The boron nitride mixed powder obtained by the present invention is a uniformly dispersed mixture of boron nitride powder and non-oxide ceramic powder. It has an effective action as a powder for composites. Further, the boron nitride mixed powder has good sinterability and provides a composite sintered body with excellent properties. In particular, since the boron nitride mixed powder obtained by the present invention is a mixed powder in which boron nitride powder and non-oxide ceramic powder are uniformly dispersed, it can be obtained by sintering the powder. A boron nitride-based composite sintered body having a uniform structure can be obtained. Therefore, the composite sintered body has various aspects compared to a composite sintered body obtained by a conventionally known method, that is, by sintering a simple mixture of boron nitride powder and non-oxide ceramic powder. For example, they generally have high bending strength. In addition, the composite sintered body contains 5 to 40% by weight of boron nitride and 95 to 40% by weight of non-oxide ceramic powder.
In the range of 60% by weight, more preferably boron nitride is 10
~30% by weight and non-oxide ceramic powder in the range of 90 to 70% by weight, it exhibits properties as so-called machinable ceramics that can be cut with ordinary tools. A mixed powder in which boron nitride powder and various non-oxide ceramic powders are uniformly dispersed can be easily obtained by a simple means such as the present invention, and by using the powder, the characteristics of boron nitride ceramics can be improved. The industrial value of the present invention is extremely large because it can significantly improve the performance. EXAMPLES The present invention will be specifically illustrated below with reference to Examples, but the present invention is not limited to these Examples. Example 1 The content of particles with an average particle size of 1.31 μm and 3 μm or less was 90% by volume, and 160 parts by weight of aluminum nitride with the composition shown in Table 1 and boric acid (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.)
100 parts by weight were uniformly mixed in a ball mill by wet mixing using a nylon pot and a nylon-coated ball with ethanol as a liquid dispersion medium. The mixture thus obtained was dried and then dry-pulverized using a nylon-coated ball in a nylon pot. After pulverization, this mixture is placed in an alumina boat, and pure ammonia gas is added to the electric furnace at 200ml/min.
The mixture was heated at a temperature of 1000° C. for 6 hours while being continuously fed with water. The resulting powder was white. The nitrogen content of this powder was 37.5%, and the conversion rate of boric acid to boron nitride, that is, the yield of boron nitride, was 95%. It is also believed that unreacted boric acid has become boron oxide. Therefore, the composition of the powder is considered to be 80% aluminum nitride, 19% boron nitride, and 1% boron oxide. Ma

[Table] As a result of X-ray diffraction analysis of the powder, only the diffraction peak of aluminum nitride was observed, and no clear diffraction peak of hexagonal boron nitride was observed. Therefore, the powder is believed to be a mixture of aluminum nitride and amorphous boron nitride. Observation using a scanning electron microscope revealed that the majority of the primary particles in this powder had an average size of about 0.7 μm, and these particles, which appeared to be aluminum nitride, were covered with an amorphous substance that appeared to be amorphous boron nitride. 12g of the above powder was placed in a graphite die coated with boron nitride with a diameter of 40mm, and then pressure-sintered at a temperature of 2000℃ for 3 hours under a pressure of 200Kg/cm ² in nitrogen gas of 1 atm using a high-frequency induction heating furnace. concluded. The obtained sintered body was white. It was found by X-ray diffraction that this sintered body consisted of two phases: aluminum nitride and hexagonal boron nitride. The density measured by the Archimedes method was 2.98 g/cm ³ . A test piece approximately 3 mm square and approximately 40 mm long was cut out from the sintered body, polished with No. 1500 sandpaper, and its bending strength was measured. The measurement conditions were three-point bending with a crosshead speed of 0.5 mm/min and a span of 20 mm. The bending strength calculated from the measured values is 52Kg/
It was warm in ^mm2 . Further, when the workability of the above-mentioned sintered body was investigated, it was found that it was easy to drill holes with a carbide drill and cut with a carbide cutting tool, and was free-cutting. Furthermore, the thermal conductivity at room temperature of a sintered body with a diameter of 10 mm and a thickness of 2.5 mm, which was produced by pressure sintering a mixed powder of aluminum nitride and boron nitride under the same conditions as above, was measured using a Rigaku Laser Flash. Measurement was performed using a method for measuring thermal constants, PS-7. the result,
The thermal conductivity was found to be 75 W/m·K. Further, the obtained boron nitride mixed powder containing aluminum nitride was brought into contact with a 2% aqueous solution of a silane coupling agent (A-172, manufactured by Nippon Unicar Co., Ltd.), filtered, and dried under reduced pressure at room temperature. After dissolving 100 g of heat-curable silicone rubber in 700 g of trichloroethane, 600 g of the boron nitride mixed powder treated with the silane coupling agent was added thereto, and vacuum defoaming was carried out while stirring uniformly. The obtained slurry was applied onto a polyethylene sheet, and after drying, it was press-vulcanized at a temperature of 165° C. for 40 minutes. The thermal conductivity of the obtained sheet with a thickness of 0.6 mm is 0.009 cal/cm・
It was sec.K. Comparative Example 1 The aluminum nitride powder used in Example 1 was simply mixed with boron nitride having a purity of 99.5% and a proportion of particles of 5 μm or less at 95% by volume. This was sintered in the same manner as in Example 1 to obtain a composite sintered body. The density of the composite sintered body is 2.75 g/cm ³ and the bending strength is 34
Kg/mm ² and thermal conductivity was 73 W/m·K. Examples 2 to 3 In Example 1, an experiment was conducted in exactly the same manner as in Example 1 except that the mixing ratio of aluminum nitride powder and boric acid was changed. The results are summarized in Table 2.

[Table] Example 4 A mixture of 195 parts by weight of aluminum nitride powder with the same properties as used in Example 1, 100 parts by weight of borax, and 80 parts by weight of urea was placed in an alumina boat, and pure ammonia gas was introduced into an electric furnace. It was heated at a temperature of 800° C. for 4 hours while continuously feeding at 150 ml/min.
After the reaction was completed, the product was allowed to cool and was quickly washed with water, then with ethanol, and dried. The resulting powder was white. Analysis of the powder by X-ray diffraction revealed that the powder was a mixed powder of aluminum nitride and boron nitride, and chemical analysis revealed that it was aluminum nitride.
80.3% and boron nitride 19.7%. Observation using a scanning electron microscope revealed that the powder was a mixed powder in which aluminum nitride and boron nitride were mutually uniformly dispersed, and no agglomeration of boron nitride was observed. 100 parts by weight of the thus obtained mixed powder and 1 part by weight of yttrium oxide were uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the obtained slurry, it was sintered under pressure in the same manner as in Example 1. The obtained sintered body was white and had a density of 2.98 g/cm ³ . The physical properties of the sintered body were measured in the same manner as in Example 1, and the bending strength was 50 Kg/m ² . The thermal conductivity at room temperature was 112 W/m·K. On the other hand, as in Example 1, the workability of the sintered body was examined, and it was found that it had the same free machinability as that obtained in Example 1. Example 5 160 parts by weight of silicon nitride (TS-7 manufactured by Toyo Soda Kogyo Co., Ltd.) with an average particle diameter of 0.6 μm and an α phase content of 90% by weight, and 100 parts by weight of boric acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent). were mixed and fired in the same manner as in Example 1. The resulting powder was light gray in color. The yield of boron nitride is
It was 96%, and it is thought that unreacted boric acid has become boron oxide. Therefore, the composition of the powder is 80% silicon nitride, 19.2% boron nitride,
It is thought to be 0.8% boron oxide. Further, as a result of X-ray diffraction analysis of the powder, only the diffraction peak of α-type silicon nitride was observed, and no clear diffraction peak of hexagonal boron nitride was observed. Therefore, the powder is
It is thought to be a mixture of α-type silicon nitride and amorphous boron nitride. Observation using a scanning electron microscope revealed that the silicon nitride particles were uniformly covered with an amorphous substance believed to be amorphous boron nitride. 100 parts by weight of the above mixed powder and 5 parts by weight of magnesium oxide were uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the obtained slurry, it was pressure sintered at a temperature of 1750° C. for 3 hours under a pressure of 200 kg/cm ² in nitrogen gas of 1 atm. The obtained sintered body was light gray in color.
It was found by X-ray diffraction that this sintered body consisted of two phases: β-type silicon nitride and hexagonal boron nitride. The density measured by Archimedes method is
It was 2.93g/ ^cm3 . The bending strength of the sintered body was measured in the same manner as in Example 1, and was found to be 75 Kg/mm ² . On the other hand, as in Example 1, the workability of the sintered body was examined, and it was found that it had the same free machinability as that obtained in Example 1. Example 6 160 parts by weight of silicon carbide (manufactured by IBIDEN, trade name Beta Random) with an average particle size of 0.3 μm and a SiC content of 98% by weight and boron (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent)
100 parts by weight were mixed and fired in the same manner as in Example 1. The resulting powder was gray in color. The yield of boron nitride was 95%. It is also believed that unreacted boric acid has become boron oxide. Therefore, the composition of the powder is 80% silicon carbide, 19% boron nitride,
It is believed to be 1% boron oxide. Furthermore, as a result of X-ray diffraction analysis of the powder, it is considered to be a mixture of β-type silicon carbide and amorphous boron nitride.
Observation using a scanning electron microscope revealed that the silicon carbide particles were uniformly covered with an amorphous substance believed to be amorphous boron nitride. 100 parts by weight of the powder thus obtained, 1 part by weight of metallic boron, and 1 part by weight of carbon black were uniformly mixed in a ball mill using hexane as a dispersion medium. After drying the obtained slurry, it was filled into a 40 mmφ graphite mold and heated by high frequency induction heating.
In argon gas at atmospheric pressure, under a pressure of 200Kg/ ^cm2 ,
Pressure sintering was performed at a temperature of 2000°C for 1 hour. The obtained sintered body was black and had a density of 2.92 g/cm ³ . As a result of X-ray diffraction analysis of this sintered body, boron nitride was transformed into hexagonal boron nitride. The physical properties of the sintered body were measured in the same manner as in Example 1, and the bending strength was 51 Kg/mm ² . The thermal conductivity at room temperature was also found to be 70 W/m·K. On the other hand, as in Example 1, the workability of the sintered body was investigated, and it was found that it had poor machinability similar to that obtained in Example 1. Example 7 A mixture of 100 parts by weight of aluminum nitride powder having the same properties as used in Example 1 and 11 parts by weight of boron powder with a purity of 99% (manufactured by Wako Pure Chemical Industries, Ltd.) was placed in a boron nitride crucible and placed in an electric furnace. 500ml/min of nitriding gas
The mixture was heated at a temperature of 1500° C. for 6 hours while being continuously supplied with water. The resulting powder was white. The yield of boron nitride was 99%, and the composition of the powder was 80% by weight of aluminum nitride, 19.8% by weight of boron nitride, and 0.2% of unreacted boron (possibly partially converted to boron oxide). It was in weight%. Observation using a scanning electron microscope revealed that the powder was a mixed powder in which aluminum nitride and boron nitride were mutually uniformly dispersed, and no agglomeration of boron nitride was observed. 100 parts by weight of the powder obtained in this example and 1 part by weight of yttrium oxide were uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the obtained slurry, it was sintered under pressure in the same manner as in Example 1. The obtained sintered body was white and had a density of 2.97 g/cm ³ . The physical properties of the sintered body were measured in the same manner as in Example 1, and the bending strength was 49 Kg/mm ² . Moreover, the thermal conductivity at room temperature was 110 W/m·K. On the other hand, as in Example 1, the workability of the sintered body was examined, and it was found that it had the same free machinability as that obtained in Example 1. Example 8 20 g of aluminum nitride powder having the same properties as used in Example 1 was added to 150 ml of liquid ammonia and stirred. While stirring the above suspension, add boron trichloride.
Add a solution containing 25g in n-hexane. After completion of the reaction, the obtained reaction product is filtered, washed, and dried.
It was heated at 1500°C for 4 hours in an electric furnace while flowing nitrogen gas. Note that all of the above reaction operations and handling of the reaction products were performed under a nitrogen atmosphere. The obtained powder was white, and analysis by X-ray diffraction revealed only diffraction peaks due to aluminum nitride and boron nitride. As a result of chemical analysis, the composition of the powder was 80% by weight of aluminum nitride and 19.9% by weight of boron nitride.
It was in weight%. Observation of the powder using a scanning electron microscope revealed that it was a mixed powder in which aluminum nitride particles and boron nitride particles were mutually uniformly dispersed. 100 parts by weight of the thus obtained mixed powder and 1 part by weight of yttrium oxide were uniformly mixed in a ball mill using ethanol as a dispersion medium. After drying the obtained slurry, it was sintered under pressure in the same manner as in Example 1. The obtained sintered body was white and had a density of 2.99 g/cm ² . The physical properties of the sintered body were measured in the same manner as in Example 1, and the bending strength was 54 Kg/mm ² . The thermal conductivity at room temperature was 120 W/m·K. On the other hand, as in Example 1, the workability of the sintered body was investigated, and it was found that it had free machinability similar to that obtained in Example 1.

Claims (1)

[Claims] 1 A non-oxide ceramic powder other than boron nitride and boron or a boron compound are contained in a mixed powder of boron nitride and non-oxide ceramic powder in an amount of 95 to 10% by weight. A mixed powder of boron nitride and other non-oxide ceramics, characterized in that the mixture is brought into contact with nitrogen or a nitrogen compound to nitride boron or a boron compound and convert it into boron nitride. Production method.