JPH0448722B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a boron nitride composite containing titanium nitride manufactured by a vapor phase deposition method and a method for manufacturing the same. BACKGROUND OF THE INVENTION Conventionally, methods for producing boron nitride by chemical vapor deposition have been known. This is a boron deposition source gas containing boron as a raw material gas, e.g.
BCl ₃ , BF ₃ , B ₂ H ₆ , etc. and a nitrogen-containing nitrogen deposition source gas such as NH ₃ , N ₂ are used, and the above two gases are reacted at high temperature to form boron nitride. It is generated. At that time, if a solid substrate such as a carbon plate or a metal rod is present, boron nitride is deposited in a layer on the surface of the solid body, and a thin film or a lump of boron nitride can be obtained. The chemical vapor-deposited boron nitride thus obtained has the C-plane of boron nitride oriented parallel to the substrate surface.
There are differences in the properties of the precipitation growth direction and its perpendicular direction. Chemical vapor deposited boron nitride is gaining importance as a unique material because of its excellent properties such as high purity, high-temperature corrosion resistance, and electrical insulation, as well as the above-mentioned anisotropy. Boron nitride lumps can also be produced by adding sintering aids such as boric acid or silica glass to boron nitride powder and using the pressureless sintering method or the hot press sintering method. The bodies differ significantly in purity and microstructure from chemical vapor deposited boron nitride. By the way, it has been disclosed that a composite sintered body of titanium diboride and boron nitride can be obtained with respect to boron nitride lumps containing titanium (Japanese Patent Publication No. 1973-
No. 15078). However, the vapor-phase deposited boron nitride of the present invention containing titanium nitride has not been previously known. Purpose An object of the present invention is to provide a vapor phase deposited boron nitride containing titanium nitride and a method for producing the same. Composition The composition of the present invention is boron nitride synthesized by a vapor phase precipitation method, and titanium nitride in an amount of 0.05% by weight.
Boron nitride containing titanium nitride is characterized by containing less than 2% by weight of boron nitride, and as a method for producing the boron nitride, the boron nitride is deposited from a boron deposition source gas and a nitrogen deposition source gas. This is a method for producing boron nitride containing titanium nitride by adding and mixing a titanium deposition source gas in an amount such that the Ti/B atomic ratio is 0.005 or more and less than 0.2. The vapor-phase precipitated boron nitride containing titanium nitride of the present invention contains titanium as titanium nitride, and the boron nitride forming the matrix is vapor-phase precipitated boron nitride, and such a material is completely new. It is something. Vapor-phase precipitated boron nitride containing titanium nitride, which is an example of this invention, uses a matrix of polycrystalline boron nitride in which the C-plane of boron nitride is oriented parallel to the precipitation surface, and has fine particles of about 100 Å in size in the matrix. Titanium nitride particles are present in a uniformly dispersed manner. The boron nitride crystallites that form the matrix differ from hexagonal boron nitride in which the hexagonal network layers formed of B ₃ N ₃ are stacked in a perfect three-dimensional arrangement. Normally, it has a turbostratic structure with a slightly larger interlayer distance of 3.35 to 3.45 Å, but it is also possible to use hexagonal boron nitride depending on the manufacturing conditions, and it is also possible to use amorphous boron nitride. It is also possible to do this. Titanium is contained as titanium nitride, and its content is in the range of 0.05 or more and less than 2 weight as titanium nitride, and the amount can be controlled by manufacturing conditions. When the content of titanium nitride is less than 0.05% by weight, the presence of titanium nitride has no effect, and when the content exceeds 10% by weight, the composition becomes non-uniform. However, in the present invention, the content of titanium nitride is set at 0.05% by weight or more.
Less than % by weight. The density of chemical vapor deposited boron nitride containing titanium nitride, which is an example of this invention, varies depending on the manufacturing conditions and falls within the range of 1.4 to 2.3 gr/ ^cm3 , but the density containing titanium nitride is 2.0 to 2.2 gr/cm3. cm ³ chemical vapor deposited boron nitride is more suitable as a material. The chemical vapor-deposited boron nitride containing the titanium nitride of the present invention has an extremely low thermal diffusivity in the direction perpendicular to the deposition surface, and can be expected to be used as an excellent heat insulating material. Conventional chemical vapor-deposited boron nitride has a structure in which the C-plane of boron nitride is oriented parallel to the precipitation surface as described above, so it exhibits remarkable anisotropy that is not seen in ordinary sintered bodies. For example, the thermal diffusivity has a value of 10 to 12×10 ^-3 cm ² /sec in the direction perpendicular to the precipitation surface, and 5×10 ^-1 cm ² /sec in the direction parallel to the precipitation surface.
From these values, in the direction perpendicular to the precipitation surface, the insulation material,
Similarly, in the direction parallel to the precipitation surface, it is a good conductor of heat. The thermal diffusivity of the chemical vapor deposited boron nitride containing titanium nitride in the direction perpendicular to the precipitation surface of this invention is:
It exhibits a value close to about 1/2 to 1/5 of the thermal diffusivity of the conventional chemical vapor-deposited boron nitride mentioned above. Figure 1 shows an example of the temperature change in thermal diffusivity 1 in the direction perpendicular to the precipitation surface of chemical vapor deposited boron nitride of the present invention containing titanium nitride, compared with that of conventional chemical vapor deposited boron nitride 2. This is the graph shown. Thermal diffusivity has the following relationship with thermal conductivity. Thermal conductivity = Sample density x Specific heat x Thermal diffusivity...(1) The density of the chemical vapor deposited boron nitride of this invention containing titanium nitride is 2.3 gr/cm ³ or less as described above, which is higher than that of conventional chemical vapor deposition. The density of phase precipitated boron nitride is 2.0
2.2 gr/cm ³ , the density term in the above equation (1) is almost the same for both the present invention and the conventional method. Further, the specific heat is a value determined by the constituent elements, and is the same for boron nitride forming the matrix of this invention and the conventional boron nitride, and is about 0.2 cal/gr°C at room temperature. On the other hand, the specific heat of titanium nitride is approximately 0.15 cal/gr°C at room temperature. Therefore,
Since the specific heat term in equation (1) is almost the same for the product of this invention and the conventional product, the difference in thermal diffusivity between the product of this invention and the conventional product shown in Figure 1 directly represents the difference in thermal conductivity. It can be said that Figure 2 shows the thermal conductivity value 3 calculated from the above formula (1) from the thermal diffusivity value of the chemical vapor deposited boron nitride of this invention containing titanium nitride, and the thermal conductivity of various conventionally known materials. This is a comparison with the rate. For example, among the lines showing the thermal conductivity of various materials, powdered magnesia 4, insulation brick 5, stabilized zirconia 6, transparent quartz glass 7, clay refractory 8, dense alumina sintered body 9, dense magnesia sintered body body 1
0, indicates the thermal conductivity of beryllia 11. Like the chemical vapor deposited boron nitride of this invention containing titanium nitride, it exhibits low thermal conductivity, and is resistant to thermal shock with the same gas impermeability (dense quality) as conventional chemical vapor deposited boron nitride. , materials with corrosion resistance at high temperatures are extremely useful as insulation materials. Next, an example of the method for manufacturing chemical vapor deposition boron nitride of the present invention containing titanium nitride will be described. The chemical vapor deposition boron nitride containing titanium nitride of the present invention is produced by adding a titanium deposition source gas to the boron deposition source gas in a method of depositing chemical vapor deposition boron nitride using a boron deposition source gas and a nitrogen deposition source gas. , can be produced by mixing.
Boron deposition source gases include halides such as BCl ₃ and BF ₃ , hydrides such as B ₂ H ₆ and B ₁₀ H ₁₄ , B ₃ N ₃ H ₆ (borazine) and B ₃ N ₃ H ₃ Cl ₃ (borazine). One or more selected from nitrogen-containing boron compounds such as (borazole chloride) and alkyl boron compounds such as B(C ₂ H ₅ ) ₃ and B(CH ₃ ) ₃ can be used. It is preferable to use B ₂ H ₆ and BCl ₃ which are gases at room temperature.
Nitrogen deposition source gases include nitrogen hydride,
(HN ₃ , NH ₃ , N ₂ H ₄ ), ammonium halides (NH ₄ Cl, NH ₄ Br, NH ₄ F, NH ₄ HF ₂ ,
One or more kinds selected from NH ₄ I) and nitrogen can be used, and it is appropriate to use NH ₃ because it is inexpensive. Further, as the titanium deposition source gas, one or more selected from titanium halides (Ticl ₄ , TiBr ₄ , TiF ₄ , TiI ₄ ) can be used. TiCl ₄ is relatively inexpensive and has a high vapor pressure, making it easy to use. In addition to the source gas, any one or more of N ₂ , Ar, He, and H ₂ may be used as necessary to convey and/or dilute the source gas. Boron deposition source gas, titanium deposition source gas, nitrogen deposition source gas, and optionally used conveying and/or dilution gases are introduced into a reactor containing heated gases, such as concentric double tube or triple tube. The method of mixing the mixed deposition gas of boron and titanium with the nitrogen deposition source gas near the substrate using a combination tube such as a tube is advantageous for increasing the reaction efficiency and deposition rate of the raw material gas, but it is There is no problem in introducing the deposition source gas into the reactor after mixing. Boron nitride containing titanium nitride can be obtained when the temperature of the substrate in the reactor is in the range of 500 to 2000°C, but preferably 1000 to 1500°C, more preferably 1200 to 2000°C.
A temperature range of 1400°C is preferred. In addition, high frequency plasma, microwave plasma,
By using a laser or the like in combination, the temperature at which boron nitride of the present invention containing titanium nitride can be manufactured can be lowered. The total pressure inside the reactor is
A range of 0.1 to 770 Torr is used, preferably 0.5 to 50 Torr, and most preferably 1 to 15 Torr. Next, the manufacturing conditions of the manufacturing method according to the present invention,
The relationship with the properties of boron nitride containing titanium nitride to be manufactured will be explained. FIG. 3 shows the manufacturing temperatures at which chemical vapor deposited boron nitride of the present invention containing titanium nitride (line 12) and chemical vapor deposited boron nitride without titanium nitride (line 13) are manufactured. It is a graph showing an example of the influence on the density of precipitates. There was no difference in the manufacturing conditions other than the manufacturing temperature between when the titanium deposition source gas was added and when it was not. As is clear from Figure 3, when titanium is added, compared to when titanium is not included,
It can be seen that high density production can be obtained even at low temperatures.
This high density is achieved not only by the increase in density due to the inclusion of titanium as titanium nitride, but also by the progress of crystallization of boron nitride forming the matrix. In the case of Figure 3, the amount of titanium nitride contained is approximately 0.5% by weight, and the contribution of titanium nitride to the density increase is extremely small.
The densification is substantially due to the progress of crystallization of boron nitride. The degree of crystallization of boron nitride is
This can be determined by measuring the interlayer distance of boron nitride, and the shorter the interlayer distance, the higher the degree of crystallization. Figure 4 shows the effect of manufacturing temperature on the interlayer distance of boron nitride, showing chemical vapor deposited boron nitride forming the matrix of precipitates when titanium is added (line 14) and when manufactured without titanium. Chemical vapor deposited boron nitride (line 15)
A graph of an example of comparison is shown. The manufacturing conditions in this case are exactly the same as those shown in FIG. As is clear from the graph in FIG. 4, it can be seen that by adding titanium, boron nitride is precipitated with more advanced crystallization. Chemical vapor phase precipitated boron nitride, in which boron nitride with poor crystallinity is precipitated, generally has a low density and is chemically unstable. High production temperature conditions of 1850°C or higher were required to obtain chemically stable precipitates. According to the method of adding and mixing a titanium deposition source gas to a boron deposition source gas of the present invention, chemical vapor deposited boron nitride containing titanium nitride having performance superior to conventional chemical vapor deposited boron nitride can be produced at a manufacturing temperature.
It can also be produced at 1200°C. Furthermore, when producing agglomerates by chemical vapor deposition, the deposition rate is an important factor, and according to the method of adding titanium of this invention, the deposition rate is lower than when titanium is not added. Faster by about 1.5
Double. For example, chemical vapor deposited boron nitride containing titanium nitride at a production temperature of 1400° C. can be produced at a deposition rate of 0.2 mm/hr or more, and this increased rate is particularly advantageous in the production of bulk bodies. The content of titanium nitride in the chemical vapor-deposited boron nitride of this invention containing titanium nitride can be controlled mainly by the flow rate ratio of the boron deposition source gas and the titanium deposition source gas, but it also depends on the production temperature, the inside of the reactor, and the total pressure. It can also be controlled by In order to lower the production temperature and increase the deposition rate, it is necessary to set the amount of titanium deposition source gas added within a preferable range. In the present invention
The flow rate of the titanium deposition source gas relative to the boron deposition source gas is set so that the Ti/B atomic ratio is in the range of 0.005 or more and less than 0.2. The vapor-deposited boron nitride of the present invention containing titanium nitride can take various forms depending on its use. That is, it is possible to produce any of the following: thin film, plate, rod, pipe, crucible, and other molded products. The vapor-deposited boron nitride of the present invention, which contains titanium nitride, has the superior heat resistance, chemical stability, wet slip properties, machinability, neutron absorption ability, and large anisotropy of previously known boron nitrides. In addition, it has the above-mentioned excellent heat resistance, so it can be used as a high-temperature shield, for example.
Used in high-temperature reactor insulation materials, high-temperature reactor jigs, high-purity metal crystal growth crucibles, electron beam hearth liners, electrical materials, nuclear reactor shielding materials, etc. Next, the present invention will be specifically explained using examples. Example 1 BCl ₃ , NH ₃ and TiCl ₄ were used as raw material gases, and H ₂ gas was used as a carrier gas for TiCl ₄ . The respective gas flow rates were as follows. BCl ₃ ...150ml/min _NH3 ...90ml/min TiCl4 _... 8ml/min _H2 ...670ml/min These gases were introduced into a reactor containing a graphite substrate heated to 1400°C, and It was allowed to precipitate for hours. During this time, the total pressure inside the reactor was maintained at 5 Torr. After the reaction was completed, gas introduction was stopped, the inside of the reactor was evacuated, and the substrate was cooled. After cooling, when the substrate was taken out from the reactor,
A 1 mm thick black-blue boron nitride containing titanium nitride was deposited on the surface. The results of measuring the characteristics of boron nitride containing titanium nitride were as follows. TiN content...0.5% by weight Density...2.16gr/cm Interlayer distance of ³ matrix BN...3.38Å Thermal diffusivity in the direction perpendicular to the precipitation surface
...1.8×10 ^-3 cm ² /sec The above characteristics were measured for commercially available chemically vapor deposited boron nitride for comparison, and the following results were obtained. Density...2.14gr/cm ^Interlayer distance...3.42Å Thermal diffusivity in the precipitation direction...7.8×10 ^-3 cm ² /sec According to the above results, the chemical vapor deposited boron nitride of this invention containing titanium nitride is Compared to conventional chemical vapor-deposited boron nitride, the thermal conductivity in the direction perpendicular to the deposition surface is approximately 1/4, meaning that it has extremely high heat insulation properties. Example 2 The flow rate of each gas, the deposition time, and the pressure inside the reactor were the same as in Example 1, and the temperature of the substrate was set at 1300° C. to produce boron nitride containing titanium nitride. After cooling, the substrate was taken out, and a 0.6 mm thick layer of black chemical vapor-deposited boron nitride containing titanium nitride was found on the surface of the substrate. The physical properties were measured and the results for steam were obtained. TiN content: 0.9% by weight Density: 2.19gr/cm Interlayer distance of ³ matrix BN: 3.37Å Thermal diffusivity in the direction perpendicular to the precipitation surface
...1.5×10 ^-3 cm ² /sec Example 3 The flow rate of each gas and the deposition time were the same as in Example 1, the pressure inside the reactor was 10 Torr, and the temperature of the substrate was
Boron nitride containing titanium nitride was produced at 1200℃. After cooling, the substrate was taken out, and a 0.7 mm thick black-blue boron nitride containing titanium nitride was obtained on the surface of the substrate. As a comparative example, boron nitride was produced under the same conditions as in Example 3 except that no TiCl ₄ was added, and white boron nitride with a thickness of 0.5 mm was obtained on the surface of the substrate. Table 1 shows the results of density, elemental analysis, and structural analysis of the samples obtained in Example 3 and Comparative Example.

[Table] In Table 1, stability against humidity shows the weight increase (%) after the product was left in the atmosphere for one month. This weight increase is caused by the hydrolysis of boron nitride. From the comparison results in the table above, when the substrate temperature is relatively low, the comparative example has a low density and is unstable to moisture, whereas the product manufactured by the method of this invention has a low density. is high, indicating that it is stable against moisture. Example 4 Boron nitride precipitates with different titanium nitride contents were created by changing the flow rate ratio of TiCl ₄ and BCl ₃ at a substrate temperature of 1400°C and a total pressure in the reactor of 5 Torr, and their properties were compared. did. Table 2 shows the manufacturing conditions, and Table 3 shows the properties of the product.

【table】

[Table] As shown in Table 3, when the Ti content exceeds 10wt%, TiN and _TiB2 precipitate in a non-uniform manner, resulting in BN
The effect of improving crystallinity is lost, and
As the Ti content increased, layered precipitation occurred.
The characteristics of TiN and TiB ₂ appear strongly, and the excellent anisotropy originally possessed by BN is lost. Effects As explained above, according to the present invention, it is possible to obtain a boron nitride molded body having extremely strong anisotropy in the direction parallel to the deposition surface on the substrate and in the direction perpendicular thereto.

[Brief explanation of drawings]

Figure 1 is a graph showing temperature changes in thermal diffusivity in the direction of precipitation of chemical vapor deposited boron nitride as an example of the present invention containing titanium nitride and conventional chemical vapor deposited boron nitride. FIG. 3 is a graph showing the thermal conductivity in the precipitation direction of chemical vapor-deposited boron nitride of this invention containing titanium, and the thermal conductivity of other ceramic materials. Figure 4 is a graph showing the relationship between the density of boron nitride that does not contain titanium and the manufacturing temperature of each, and the interlayer distance of boron nitride of the present invention that contains titanium nitride and boron nitride that does not contain titanium and the manufacturing temperature of each. This is a graph showing the relationship between 1... A line showing the thermal diffusivity in the direction perpendicular to the precipitation surface of boron nitride of this invention containing titanium nitride, 2...
A line showing the thermal diffusivity in the direction perpendicular to the precipitation surface of boron nitride not containing titanium, 3... A line showing the thermal conductivity of boron nitride of the present invention containing titanium nitride, 4...
A line showing the thermal conductivity of magnesia powder, 5... A line showing the thermal conductivity of the insulating brick, 6... A line showing the thermal conductivity of stabilized zirconia, 7... A line showing the thermal conductivity of transparent quartz glass. , 8... A line showing the thermal conductivity of the clay refractory, 9... A line showing the thermal conductivity of the dense alumina sintered body, 10... A line showing the thermal conductivity of the dense magnesia sintered body, 11... A line showing the thermal conductivity of beryllium oxide, 12... A line showing the density of boron nitride of this invention containing titanium nitride, 13...
Line showing the density of boron nitride without titanium, 1
4... A line showing the interlayer distance of boron nitride of the present invention containing titanium nitride, 15... A line showing the interlayer distance of boron nitride not containing titanium.

Claims (1)

[Scope of Claims] 1. Boron nitride containing titanium nitride, which is synthesized by a vapor phase precipitation method and is characterized by containing 0.05% by weight or more and less than 2% by weight of titanium nitride. 2. In the method of depositing boron nitride from a boron deposition source gas and a nitrogen deposition source gas, adding and mixing titanium deposition source gas in an amount such that the Ti/B atomic ratio is 0.005 or more and less than 0.2. A method for producing boron nitride containing titanium nitride, characterized by: