JPH03183699A - Production of sic whisker - Google Patents

Abstract

PURPOSE:To improve quality of the subject material by adding a specified amt. of a metallic catalyst to a starting material for an Si source and allowing the starting material to react with a carbon material under specified heating conditions. CONSTITUTION:A metallic catalyst such as Fe, Co, Ni, Mn, Ca and the oxide, carbonate, sulfate or nitrate thereof is uniformly supported on a starting material for an Si source such as silica gel by >=0.06mol per 1mol of the starting material. This catalyst supported starting material is mixed with 60-120wt.% carbon material such as carbon black having >=100ml/100g DBP oil absorption. This mixture is filled into a reactor, heated to 1,550-1,800 deg.C at >=10 deg.C/min heating rate in a nonoxidizing atmosphere of gaseous Ar, etc., and brought into a reaction under heating at the temp. for a prescribed time. The resulting reaction product is taken out of the reactor and SiC whiskers are obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to a large-diameter type SiC with a diameter exceeding 2.0 μm.
This invention relates to a method of manufacturing whiskers.

[Conventional technology]

Whiskers composed of acicular single crystals of 5iCO have excellent performance characteristics in terms of specific strength, specific modulus of elasticity, heat resistance, and chemical stability, so they can be used as composites of various plastic materials, metal materials, or ceramic materials. It is useful as a reinforcing material.

Among these, composite strengthening of ceramic materials, which have particularly poor fracture toughness, has been considered an important development issue in recent years. The mechanism by which the fracture toughness of ceramic materials is improved by combining whiskers is that the whiskers dispersed within the structure stop or suppress the growth of cracks that occur in the ceramic body.
This is said to be based on phenomena such as bending the direction of crank movement to alleviate stress concentration, and absorbing energy at the tip of the crank through the pulling action of the whiskers. It has been confirmed that it is effective to combine whiskers with large diameter whiskers to increase their toughness.

Furthermore, since whiskers have the form of fine needle-like fibers, when they are inhaled into the human respiratory system, they tend to remain in the lungs, and it has been pointed out that there is a risk of respiratory disorders. This damage is closely related to the whisker diameter, and is especially dangerous when the whisker diameter is less than 2 μm.

Due to the need to improve the composite toughness of such ceramic materials and ensure safety for the human body, a diameter of at least 2.0 mm is required.
There is a strong demand for the development of a manufacturing method for obtaining large-diameter type SiC whiskers that exceed μ-closure.

[Problem to be solved by the invention]

There are two methods for producing SiC whiskers, one using a gas-phase raw material system and the other using a solid-phase raw material system.
For example, Japanese Patent Publication No. 60-44280, Japanese Patent Publication No. 61-
If large-diameter whiskers can be produced by the method (Japanese Patent Publication No. 102416), it will be advantageous for disentangling the generated whiskers and facilitating their separation from by-product particles (shot).

However, it is difficult to generate large-diameter SiC whiskers using solid-phase raw material-based manufacturing methods;
Until now, there is no known example of industrially producing a material with a diameter exceeding 2 μm.

The present invention was developed as a result of intensive research, especially regarding the selection of catalyst addition conditions, in order to obtain large-diameter SiC whiskers in response to the above-mentioned demands. An object of the present invention is to provide a method for producing SiC whiskers having properties exceeding .0μ.

(Means for Solving the Problems) A method for producing SiC whiskers according to the present invention to achieve the above-mentioned object includes heating a mixed raw material of a silicon source material and a carbon material to a reaction temperature range in a non-oxidizing atmosphere. In the method for producing SiC whiskers, a metal catalyst is added to the table raw material in an amount equivalent to 0.06 mol or more of metal per 1 mol of Si in the silicon source raw material, and the heat treatment conditions are set such that the heating rate is 10. °C/min, reaction temperature 1550~
A structural feature is that the temperature is set at 1800°C.

The silicon source materials used in the present invention include silica gel,
Any substance containing a silicon component such as silica sand, quartz powder, inorganic silicate, or organic silicon compound may be used, and among them, silica gel containing 5102 as a main component, quartz powder, silica sand, etc. are effective.

As the carbon material, carbon black, coke powder, graphite powder, powdered activated carbon, etc. can be used, but the most suitable carbon material is carbon black. When applying carbon black, use furnace plastic, channel black,
Any type of acetylene black etc., but especially DB
Those having a P oil absorption of 100 d1100 g or more are effectively used.

The blending ratio of the carbonaceous material to the silicon source material is set in the range of 60 to 120% by weight, and both raw material components are mixed sufficiently uniformly.

A metal catalyst selected from Fe, Co, Ni, Ca, and their oxides, chlorides, carbonates, sulfates, and nitrates is added to the above mixed raw material.

The first major requirement of the present invention is the blending conditions of the metal catalyst added to the mixed raw material, such that the metal catalyst is added in an amount equivalent to 0.06 mol or more as metal per 1 mol of Si in the silicon source raw material. Add to mixed raw materials.

If the amount of the metal catalyst is equivalent to less than 0.06 mole of metal, it will be difficult to produce SiC whiskers with a diameter of 2.0 μm or more. Moreover, if this amount exceeds 0.3 mol, the shape of the resulting SiC whiskers tends to deteriorate. Therefore, it is desirable to set the upper limit of the amount to be 0.3 mol.

It is practical to add the metal catalyst in advance to the silicon source material before mixing the carbonaceous material. The addition method may be a method of stirring and mixing in powder form, but it is advantageous for uniform dispersion to adopt a method of immersing the silicon source raw material in an aqueous solution of compounds such as chlorides and nitrates and drying.

The raw material components, including the silicon source material, carbonaceous material, and a specific amount of metal catalyst, are filled into a reaction vessel made of a highly heat-resistant material such as graphite and sealed, and the surrounding area is covered with a carbon backing material made of coke granules. In this state, it is heated by electricity.

At this time, the heat treatment conditions were as follows: a temperature increase rate of 10°C/inch or higher in a non-oxidizing atmosphere, and a reaction temperature of 1550 to 18°C.
The second major requirement is to set it to 00''C.

More suitable conditions include a temperature increase rate of 10 to 40°C/win;
, the reaction temperature should be in the range of 1600 to 1750°C.

The reason why the temperature increase rate is set to 10℃/...in or more is that
This is because if Oo(:/win is lowered, it will no longer contribute to generating large diameter SiC whiskers. Also, 40
In the case of increasing the C/min, the temperature gradient in the raw material structure increases, which tends to increase the irregular shape and variation in the shape of the generated whiskers.

The reason for setting the reaction temperature in the range of 1550 to 1800°C is because
If the temperature is lower than 1550'C, the diameter of the generated whiskers will not increase smoothly, and more Sing will remain.
This is because, in a high temperature range exceeding 0° C., the shape of the whiskers increases and the whiskers begin to become granular, increasing the amount of shots mixed together.

After the reaction, unreacted carbonaceous components remaining in the reaction vessel are removed by incineration.

The SiC whiskers obtained in this way are pale green-white, acicular single crystals of SiC without lattice defects, and have a diameter of 2.0 μm or more and a length of more than 50 μm, with a good aspect ratio. It is something.

[For production]

According to the present invention, the diameter of the produced SiC whiskers can be increased by selecting the blending conditions of the metal catalyst and the heat treatment conditions of the raw material components and satisfying these conditions simultaneously. Although the reason for this has not yet been elucidated,
In the prior art, there is no example in which the amount of metal catalyst and the heating temperature conditions are selected with the intention of increasing the diameter of the SiC whiskers produced, so there is a selective element in the action of the present invention.

〔Example〕

Examples of the present invention will be described below while comparing them with comparative examples.

Example 1 Silica gel with a particle size of 200 mesh or less was used as a silicon source raw material, and the silicon source raw material had a CO content of 0.00% per mole of Si.
CoC/! was prepared at five levels of blending ratio corresponding to 0.01 to 0.3 moles. , immersed in an aqueous solution and dried.

110% by weight of carbon black material was blended into the silicon source material on which the metal catalyst was uniformly supported in this manner, and the mixture was stirred and mixed uniformly. As carbon black for carbonaceous materials, D
Furnace black with BP oil absorption of 130 mff1/100g and iodine adsorption of 1104mg/g.
Tokai Carbon side type, "SEMST 51") was used.

Next, the mixed raw materials were lightly filled into a reaction vessel made of high-purity graphite, a graphite lid was attached to the top, and the mixture was placed in an electric resistance heating furnace maintained in a gas atmosphere.
The reaction temperature was changed at a temperature increase rate of 1.5 in, and the reaction was carried out by heating for 2 hours.

After the heating reaction, the contents were collected from the reaction vessel and heated in the atmosphere for 6 hours.
The remaining carbonaceous components were removed by heat treatment at a temperature of 00° C. by incineration.

When the obtained product was subjected to X-ray diffraction, β
Clear peaks appeared at the wavelength positions of -3iC atomic interrogator jit [2, 15, and 154, but no diffraction lines corresponding to SiO□ or C were confirmed.

Table 1 shows the diameter and shape evaluation results of each SiC whisker produced in comparison with the molar amount of metal catalyst and reaction temperature.

From the results in Table 1, SiC whiskers with a diameter of 2.0 μm or more cannot be produced when the amount of metal catalyst is less than 0.05, and at a reaction temperature of 1900°C, although the diameter becomes thicker, the whisker shape remains. There will be more bends, joints, etc.

Table 1 Example 2 Silica sand with a particle size of 200 mesh or less was used as the silicon source raw material, and FezO = was added as a metal catalyst to it at a concentration of F per mole of Si.
0 as e. Five levels of compounding amounts corresponding to 1 to 0.3 moles of O were added and mixed. Other conditions were the same as in Example 1 to generate SiC whiskers.

The diameter and shape of each SiC whisker obtained were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

The results in Table 2 also showed the same tendency as in Table 1, and the best SiC whiskers were obtained under conditions where the amount of metal catalyst was 0.10 to 0.30 mol and the reaction temperature was 1600°C.

Table [Effects of the Invention] [Effects of the Invention] As described above, according to the present invention, by applying the specified blending conditions of the metal catalyst and heat treatment conditions during reaction, a diameter of 2.0 μm or more is always achieved. It is possible to produce high-quality SiC whiskers having a shape with a good yield.

Therefore, it is possible to supply SiC whiskers that are effective in increasing the composite toughness of ceramic materials and are highly safe for the human body.

Claims (1)

[Claims] 1. In a method of generating SiC whiskers by heat-treating a mixed raw material of a silicon source raw material and a carbonaceous material to a reaction temperature range in a non-oxidizing atmosphere, a metal catalyst is applied to Si1 in the silicon source raw material. It is added to the mixed raw material in an amount equivalent to 0.06 mole or more of metal per mole, and the heat treatment conditions are set to a heating rate of 10.
°C/min. As described above, the method for producing SiC whiskers is characterized in that the reaction temperature is set at 1550 to 1800°C. 2. The method for producing SiC whiskers according to claim 1, wherein the metal catalyst is selected from Fe, Co, Ni, Mn, Ca, and their oxides, carbonates, sulfates, and nitrates.