JPS6096517A - Ultrafine silicon carbidie - Google Patents

Abstract

PURPOSE:Ultrafine polycrystalline SiC of beta type having high purity and improved sintering properties, comprising crystallite of aggregate of SiC of beta type, having a shperical shape with submicron particle diameter. CONSTITUTION:Ultrafine polycrystalline of beta type comprising crystallite of aggregate of SiC of beta type with <=50Angstrom , having a shperical shape with 0.01-1mu average particle diameter, high purity, and improved sintering properties, useful as a raw material for a molded article of heat-resistant ceramic. The SiC can be obtained in high yield and in high purity in the form of ultrafine powder by decomposing thermally an organic silicon compound containing at least one SiH bond in the molecule and no SiX (X is halogen atom or oxygen atom) bond at >=about 750 deg.C in a gaseous phase without reguiring post-treatment such as grinding process, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ultrafine silicon carbide having a spherical shape.

Silicon carbide powder bundles have recently been attracting attention as a material for heat-resistant ceramic compacts, but from the viewpoint of their uses (2) they have high purity, good sinterability, and submicron-order production. There is a demand for supply of fine powder.

Regarding the manufacturing method of this silicon carbide powder bundle, 1)
Method of reacting metal silicon and carbon at high temperature in an electric furnace and pulverizing them at the same time, 2) General formula Rn5iX4-n
(,.

(2R is a hydrogen atom or an alkyl group, X is a halogen atom, n = 1 to 4) A method of thermally decomposing a silane or a mixture of this silane and a hydrocarbon compound such as methane at high temperature, 3) Polymer Methods such as thermal decomposition of polycarbosilane and 4) mixing silicon dioxide (5 in 2) and carbon and heating to high temperature are known, but method l) Although it is suitable for the manufacturing method, it is difficult to obtain high-purity C2 products with submicron order yields because it requires a pulverization process, and method 2) requires high temperatures and is difficult to obtain. However, the yield is low and a fine powder of β-810 is obtained.

Since a small amount of 5i-at remains, there is a problem in the production of C-ceramic sintered bodies, and there is a disadvantage that it is necessary to treat HOl, which is produced as a by-product during one reaction, and is used as a raw material in method 3). Polycarbosilane is expensive and requires a post-processing step to finely grind the resulting silicon carbide;
Furthermore, method (24) requires a grinding process that requires considerably high temperatures, and furthermore, because the C2 reactant contains unreacted raw materials and by-product silicon silica, the high temperature is high after the fact. In addition to the disadvantage that purification treatment is required, the silicon carbide obtained by these pulverization methods does not have a spherical shape, making it difficult to achieve high purity, and the sinterability (even two methods are not satisfactory). It wasn't something that should have been done.

The present invention solves these disadvantages by using ultrafine silicon carbide particles with high purity and good sinterability, which is an aggregate of β-type silicon carbide with crystallites of 50A or less It is characterized by having a spherical shape with an average particle size of 0.01 to 1 μ.

To explain this, 1. The present inventors have studied various methods of obtaining high-purity silicon carbide in the form of fine powder without going through a pulverization process, and first found that at least one 8-8
An organosilicon compound that contains a 1H bond but does not contain \ to xi'; z halogen atom - oxygen atom in 81x
It has been discovered that high-purity fine silicon carbide powder can be obtained without post-treatment such as a grinding process with a higher yield by performing gas-phase pyrolysis at 50°C or higher. (See Application No. 58-155911). Further research was carried out using C2, examining the properties and sinterability of the fine powder obtained by this method, and its manufacturing conditions. As a result, it was found that the beam had a completely spherical shape, which was different from the commercially available product produced by the conventional manufacturing method C2, and that β-8iO (1
, 1, 1), individual particles are found in the dark-field image by diffraction of 50
It was confirmed that it is an aggregate of β-type silicon carbide crystallites of A or less, and its average particle size is 0.01-1μ, and that this ultrafine powder silicon carbide is different from conventional silicon carbide. The present invention was completed by discovering that it is possible to easily form a highly densified sintered body of C2 without adding any sintering aids, etc., which were thought to be indispensable to the sintering process. .

The ultrafine particulate β-type silicon carbide of the present invention is an organosilicon compound that has at least one 381H bond in one molecule and does not contain an 81X bond (X is a halogen atom or an oxygen atom).
It can be obtained by vapor phase pyrolysis at 50°C or higher. This is especially (secondly, the general formula (OH3) aSibHo
b=integer from i to 3, 2b+1≧a, a≧b, 2b
+1≧C≧l−a+o=2b+2) at least one of methylhydrodiene and 7-9 compounds represented by hydrogen or nitrogen.

Preferably, the gas phase pyrolysis is carried out in a reaction zone at a temperature of 750 DEG to 1,600 DEG C. in the presence of a cavity gas such as helium-argon at a concentration of 30% by volume or less.

In addition, since the methylhy-l-'cy dienelyrane compound as the starting material can be easily purified in advance by rectification, the obtained ultrafine particulate β-type silicon carbide also has a very high purity. Purity can be obtained.Also,
The size of the resulting silicon carbide crystallites, the spherical shape, and the particle size of the aggregate powder are determined by the concentration of the methylhydrodiene silane compound in the reaction zone, the trading time, the linear gas velocity, the reaction temperature, and the type of carrier gas. etc. σ) Since reaction conditions can be freely adjusted by selecting them, these conditions may be arbitrarily set according to the purpose.

Next, C2 Examples of the present invention will be described.

Example 1゜Inner diameter 524111. An alumina reaction tube with a length of 1.000 m was installed in a horizontal reactor, and the temperature at the center was kept at 1.1.
The temperature was maintained at 50°C, and 40011/min of hydrogen gas containing OH, 0H3 WS was introduced for 8 hours to cause gas phase thermal decomposition, and after one reaction was completed, it was cooled.

15.5g of brown ultrafine carbonized cord (yield: 75.5g)
0) was obtained.

The chemical analysis values of this powder are 81=69.9%, 0=29.
AA-Or-Ou-Fe at 4% by optical analysis
, Mg-Mn-Ni-Ti, V, and other gold-collecting impurities 11 are all 10 ppm or less.

The purity was much higher than that of commercially available silicon carbide.

The bright-field image obtained by observing this material with an electron microscope and the dark-field image obtained by β-8iO (1,1,1) diffraction are shown in Figures 1 and 2. This material consists of an aggregate of crystallites of 50λ or less, and has a grain size of 70.
It must be within the range of 0.08μ or less and 0.2μ or less, and the measurement results using a centrifugal automatic particle size distribution analyzer 0A-P A5 (l O type (trade name: Toji, manufactured by Horiba, Ltd.) indicate that it is less than 0.08μ and 0.
There are no particles larger than 5μ, and each particle size is 0.1 to 0.3μ.
It was confirmed that the particles had a uniform spherical shape with a diameter of 88.3 mm. In addition, the results of the infrared absorption spectrum and X-ray diffraction of this powder by the KBr method are shown in Figures 3 and 4-2, confirming that it is β-type S10, and the specific surface area of this powder is When measured by method, it was 26.8d/11.

Next, the ultrafine particulate carbonized silicon obtained above was degassed under reduced pressure in a 40W+yJ carbon mold for hot pressing by two people without adding any sintering aid. 2,0 under a pressure of 200Kt/-.
The sintered body was sintered by heating at 00°C for 50 minutes, and after cooling, the sintered body was taken out and the density was measured. o,
(3!!! theoretical density 3.2: 95.3 ratio to 12), and from the results of 1 or more, it was confirmed that this material had good sinterability like water.

Comparative Example A commercially available high-purity β-type disaster silicon image powder manufactured by Ibiden Co., Ltd. has an average particle size of 0.4 μ and a specific surface area of 18.6 wl/I, and the amount of metal impurities contained in it is At450p
pm, Or 10100pp cu<10ppm, F
e 500ppm, MMg 30pp.

Mn (5ppm, Nil 90ppm-T1300
ppm-V 370 m)1)m. In addition, a bright field image of this product and β-810 (
1,1,l) The dark-field image obtained by diffraction is as shown in FIGS. 5 and 6, and the spherical shape was not uniform and no clear crystallites were observed.

Examples 2 to 8 Using the same reactor as in Example 1, the type of raw material lira,
Dark I1. When the gas phase thermal decomposition of the raw material v run was carried out by changing the carrier gas type 1 composition, introduction vk - reaction temperature If as shown in Table 1g:, the results were as shown in Table 1. Silicon carbide is obtained in yield, these are secondary
It exhibited the physical properties shown in the table.

[Brief explanation of drawings]

Figure 1 shows a bright-field electron microscope image of the ultrafine particulate β-polycrystalline silicon carbide of the present invention, and Figure 2 shows the β-810 (1,
1. Dark field image directly above IJ diffraction, Figure 3 tX that KBr
Infrared absorption spectrum by method, Figure 4 is X#1!11
Diffraction diagrams, Figures 5 and 6 are electron microscopic bright field images of commercially available β-type carbide as a comparative example and β-810 (1
, 1, 1) This is a dark field image obtained by diffraction C2.

Claims (1)

[Claims] 1. Ultrafine particulate β-type polycrystalline silicon carbide which is an aggregate of β-type silicon carbide with crystallites of 50X or less and has a spherical shape with an average particle size of 0.01 to 1μ.