JPH0477399A - Manufacturing method of SiC whiskers - Google Patents

Abstract

PURPOSE:To industrially obtain SiC whisker having good straightness and high aspect ratio by using a sealed cylindrical reactor consisting of a specified porous graphite in the production process of SiC whisker from the mixture powder source material of silicon source material and carbon material by reduction method. CONSTITUTION:The reactor is filled with the powder mixture of silicon raw material and carbon material with addition of metal catalyst, and then heated in a reaction furnace at 1500-1900 deg.C in a nonoxidative atmosphere to obtain the SiC whisker. In this process, the reactor is a sealed cylinder consisting of porous graphite having 500-200ml/h.cm<2>.mm Aq air diffesibility. It is preferable that the sealed cylindrical reactor consists of porous graphite material having 0.3-1.4 g/cc bulk density.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing SiC whiskers useful as composite reinforcing materials, and in particular to industrially producing SiC whiskers having good straightness and high aspect ratio. Concerning an advantageous method for producing.

(Prior art) Whiskers composed of acicular single crystals of SiC have excellent performance characteristics in terms of specific strength, specific modulus of elasticity, heat resistance, chemical stability, etc., and are therefore used in various plastic materials and metals. It is used as a composite reinforcing material for ceramic materials.

Means for producing SiC whiskers are classified into gas-phase raw material systems and solid-phase raw material systems, depending on the state of the raw materials used.
Among these, the mass production technology currently available is a manufacturing method using a solid phase raw material system (for example, Japanese Patent Publication No. 60-44280
No. 61-102416, JP-A No. 62-3
No. 099, etc.). The basic steps of manufacturing techniques using these solid-phase raw material systems include a process in which a silicon source and a carbonaceous material are mixed together with a catalyst component in a powder state, and the raw material system is heated and reacted in a non-oxidizing atmosphere. At this time, the raw material system is packed into a closed reaction container and subjected to a heating reaction.The heating reaction can be carried out by packing the reaction container into a fixed Acheson furnace or by shuffling the reaction container into a tube furnace. A method is adopted in which the material is pushed through the material and moved intermittently by sliding.

Conventionally, the reaction vessel has been made of graphite or a ceramic material such as alumina or mullite.

[Problem to be solved by the invention]

Since the reaction vessel must be directly heated to maintain the raw material system filled therein within the reaction temperature range, the material is required to have high heat resistance and thermal conductivity. Conventionally used materials such as graphite, alumina, and mullite all have a high degree of heat resistance, but graphite materials have the best thermal conductivity.

Although it has been recognized that graphite is suitable as a constituent material for reaction vessels, there has been no study of the material structure of reaction vessels in relation to reactions and products.

The SiC whisker production reaction using a solid phase raw material system is usually a V L reaction using S10 gas due to the reaction between Sing and C.
Although it is thought that the process proceeds via the S (Vapor-Liquid-Solid) mechanism, the present inventors focused on the fact that the concentration of CO gas, which is produced as a by-product in this process, in the reaction system affects the production reaction. After repeated research, we found that when a graphite reaction vessel is filled with CO gas, the reaction to SiC is inhibited and many needle-shaped crystals with low aspect ratios with bends and knots are produced. It was confirmed that high-quality SiC whiskers with good stretchability and a high aspect ratio can be produced by releasing CO gas out of the reaction system.

The present invention has been developed based on the above findings, and its purpose is to produce high-quality S
An object of the present invention is to provide a method for industrially manufacturing iC whiskers.

[Means to solve the problem]

The method for producing SiC whiskers according to the present invention to achieve the above object includes adding a metal catalyst to a powder mixture of a silicon source material and a carbon material, and filling the mixture into a reaction vessel.
In a method of generating 7SjC whiskers by a heating reaction in a reactor maintained at a temperature of 500 to 1900"C and a non-oxidizing atmosphere, the air permeability is 500 to 2000".
The structure is characterized by the use of a closed cylindrical reaction vessel made of porous graphite material in the range of af/h HC1,''H+nmAq.

The silicon source materials used in the present invention include silica gel,
Various substances containing silicon components can be mentioned, such as silica sand, quartz powder, inorganic silicates, and organic silicon compounds, among which S
It is effective to use silica gel, quartz powder, silica sand, etc. whose main component is in.

As the carbon material, carbon blank, coke powder, graphite powder, powdered activated carbon, etc. can be used, but the most suitable carbon material is carbon black. When carbon black is used, fur fusubura tsuku, channel black,
Any type of acetylene black etc., but especially DB
Those having a P oil absorption of 100d/100g or more are effectively used.

The metal catalyst is selected from powders of Fe, Co Ni Ca, and alloys or oxides thereof.

The blending ratio of raw material components is 60% to 60% carbon material to silicon source material.
The range is 200% by weight, and the amount of metal catalyst is 0.01 to 0.1 as metal per mole of Si in the silicon source material.
It is set to 5 moles.

The above raw material system is filled into a closed cylindrical reactor made of graphite material and subjected to a heating reaction. This is to prevent leakage and scattering, and a cylindrical graphite tube is usually formed with a structure in which a drop cap made of graphite disks is fitted to both ends to seal it.

An important requirement in the present invention is that the closed disc-shaped reaction vessel has ventilation characteristics of 500 to 2000 a+F! /h H
The method is to apply a material formed using a porous graphite material in the range of cm2/mmAq. The ventilation characteristics are 50
If it exceeds 0 d/h-cm2 ・-mAq, the ventilation is insufficient and the excess CO gas filling the container cannot be smoothly discharged, making it difficult to generate high quality SiC whiskers. h-cm”・mmA
If q is exceeded, the structure of the container itself becomes fragile, which poses a problem in terms of handling, and in the case where the hole is formed by drilling, the hole becomes large, causing the inconvenience that the raw material powder passes through.

Such ventilation characteristics 500-2000d/h-cm”
A reaction vessel of porous graphite material in the range -mtaAq can be formed by processing a graphite material with a porous structure having a bulk density of 0.3 to 1.4 g/cc.

In addition, a large number of holes with a diameter of 1 to 5 mm are bored around the end (lid) and/or cylindrical part of a reaction vessel made of ordinary graphite material with a bulk density of 1.5 g/cc or more. By doing so, the ventilation characteristics are 500~2000m1! /h-
It is also possible to form the reaction vessel of porous graphite material in the range c+mz-mmAq. In this case, the number of holes to be drilled is preferably 10 to 30, for example, in a reaction vessel having an inner diameter of 40 to 200 m and a length of 100 to 500 mm. If the length of the reaction container is 200 mm or less, the holes should be installed only at both ends (lid).
For shapes exceeding 0 m5, it is preferable to install it near the center of the cylindrical part. A reaction vessel filled with a raw material system is heated to a reaction temperature range in a heating furnace maintained in a non-oxidizing atmosphere such as nitrogen or argon. As the heating furnace, a normal electric resistance heating furnace, Acheson furnace, pusher type tube furnace, etc. are used. The heating reaction conditions are a heating rate of 5 to 40°.
C/sin, the reaction temperature is set at 1500-1900°C. More suitable conditions are a heating rate of 10 to 30°
C/sin, reactivity should be in the range of 1550 to 1700°C.

If the temperature increase rate is less than 5°C/win, it will be difficult to generate large-diameter SiC whiskers;
When the material goes around l1n once, 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. In addition, the reaction temperature is 1500°C
If the temperature is below 1,900°C, the generation of SiC whiskers will not proceed smoothly, and a large amount of silicon source material will remain.In the high temperature range exceeding 1900'C, the shape of the whiskers will increase, and at the same time, the whiskers will begin to become granular, resulting in a problem with the shot. Mixing will increase.

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

The SiC whiskers thus obtained are 5iCO acicular single crystals having a pale greenish-white color and no lattice defects, and are of high quality with excellent straightness and a high aspect ratio.

[For production]

Generation of SiC whiskers using a solid raw material system proceeds through the reaction of the following formula.

S　i　Ox　10C-+S　i　o+c.

When the CO gas generated in this reaction stays in the reaction vessel and gradually fills up, a phenomenon occurs that inhibits the straight growth of SiC needle crystals.

This phenomenon is based on the present invention with air permeability of 500 to 200.
When raw material powder is filled into a closed cylindrical reaction vessel made of porous graphite material in the range of 0d/h-CIIlz-IIIIIIAq and subjected to heating reaction, excess CO gas is released from the porous structure or drilled holes. It is effectively eliminated by preferential removal to the outside. Therefore, an environment is provided in the reaction vessel in which straight, high aspect ratio crystals can grow, and SiC whiskers of high quality are always produced.

(Example) Hereinafter, examples of the present invention will be described while comparing them with comparative examples.

Example 1 Quartz powder with a particle size of 200 mesh or less was used as a silicon source material, and Fe powder was mixed as a catalyst in an amount equivalent to 0.03 mol per 1 mol of Si. Carbon black carbonaceous material was added thereto at a ratio of 180% by weight based on the silicon source material, and the mixture was stirred and mixed uniformly. Carbon black for charcoal materials has DBP oil absorption of 1130ml! Furnace black [manufactured by Tokai Carbon ■, "'5EAST5H"] having the characteristics of iodine adsorption amount of 104 mg/g and iodine adsorption amount of 104 mg/g was used.

A porous graphite material with a bulk density of 1.8 g/CC was formed from this powder mixed raw material with an inner diameter of 5011 Il and a length of 150 Il.
A closed cylindrical reaction vessel consisting of a mm-thick tubular portion and a disk lid fitted at both ends was lightly filled. The ventilation characteristics of this reaction vessel were 750 ml/h-cm".+u+Aq.

The reaction vessel was placed in an electric resistance heating furnace maintained in a nitrogen gas atmosphere, and the temperature was raised to 1640° C. at a rate of 10° C./sin, and maintained for 2 hours to generate a reaction.

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 chi-ray diffraction, it was found that β
Clear peaks appeared at wavelength positions of -3iC atomic open circuits of 82.15 and 1.54, and no diffraction lines corresponding to 5iCh or C were confirmed.

The average diameter, aspect ratio, shape, etc. of each SiC whisker produced are shown in Table 1 in comparison with the ventilation characteristics of the reaction vessel used.

In addition, the properties and shapes were evaluated using SEM of SiC whiskers.
In addition to observing them with enlarged photographs, we also measured the diameter and length of 100 of them.

Example 2 The same raw material powder as in Example 1 was lightly filled into a reaction vessel having the same shape as in Example 1 and formed by processing graphite material with a bulk density of 0.4 g/cc. The ventilation characteristics of this reaction vessel are 1520
d/h-cta! It was 1 mAq.

The reaction vessel was placed in an electric resistance heating furnace maintained in a nitrogen gas atmosphere, and a heating reaction was carried out under the same conditions as in Example 1 to remove residual carbonaceous components by incineration.

The properties, shape, etc. of the obtained SiC whiskers are also listed in Table 1.

Comparative Example 1 The same raw material powder as in Example 1 was lightly filled into a reaction vessel having the same shape as in Example 1 and formed by processing graphite material with a bulk density of 1.51/cc. The ventilation characteristics of this reaction vessel are 450
Id/h −cm” ·−*Aq.

The reaction vessel was placed in an electric resistance heating furnace maintained in a nitrogen gas atmosphere, and a heating reaction was carried out under the same conditions as in Example 1 to remove residual carbonaceous components by incineration.

The properties, shape, etc. of the obtained SiC whiskers are also listed in Table 1.

Example 3 The same raw material powder as in Example 1 was processed into a graphite material with a bulk density of 1.7 g/cc, and a tubular part 1 with an inner diameter of 50 mm and a length of 150mm was drilled with 5 holes 3 with a diameter of 2 mm at both ends. A reaction vessel as shown in FIG. 1 (cross-sectional view) and FIG. 2 (plan view of the disk lid) consisting of a disc lid 2 was lightly filled with the mixture. The ventilation characteristics of this reaction vessel are 1100I11/h・0m2・
It was mIIIAq.

The reaction vessel was placed in an electric resistance heating furnace maintained in a nitrogen gas atmosphere, and a heating reaction was carried out under the same conditions as in Example 1 to remove residual carbonaceous components by incineration.

The properties, shape, etc. of the obtained SiC whiskers are also listed in Table 1.

Comparative Example 2 The same raw material powder as in Example 1 was used at a bulk density of 1 and 7 g/cc.
A reaction vessel having the same shape as in Example 3 and having no holes was lightly filled with the reaction vessel, which was made from graphite material. The ventilation characteristics of this reaction vessel were 20R1/h-cm".IImAq.

The reaction vessel was placed in an electric resistance heating furnace maintained in a nitrogen gas atmosphere, and a heating reaction was carried out under the same conditions as in Example 1 to remove residual carbonaceous components by incineration.

The properties, shape, etc. of the obtained SiC whiskers are also listed in Table 1.

Table 1 From the results in Table 1, SiC whiskers having good straightness and a high aspect ratio are produced in Examples 1 to 3 using reaction vessels having the ventilation characteristics specified in the present invention. was recognized.

〔Effect of the invention〕

As described above, according to the present invention, SiC whiskers with excellent straightness and high aspect ratio can be manufactured with good operability by applying a reaction vessel made of a porous graphite material having specific air permeability properties. be able to.

Therefore, it becomes possible to mass-produce high-quality composite reinforcement materials for various matrix materials.

[Brief explanation of drawings]

The figures show the graphite reaction vessel used in Example 3, with FIG. 1 being a sectional view and FIG. 2 being a plan view of the disk lid portion. 1...Tubular part 2...Disc lid 3...Bore Applicant Tokai Carbon Co., Ltd. Agent Patent Attorney Masaya Takahata Procedural Amendment (Voluntary) (1) ``In the specification, page 1, line 12'' ... Particle size 200 mesh..." is corrected to "...Particle size 200 μm...". September 11, 1990 (2) Page 11, line 13 of the specification, “... interatomic distance 2
．． 15 people,..." to "...plane spacing 2.51 people,...
Patent Application No. 189993 of 1990 amended to 2, title of invention: Process for manufacturing SiC whiskers 3゜4゜Relationship with the case of the person making the amendment Patent Applicant Address: 2-3 Kita-Aoyama-chome, Minato-ku, Tokyo Name: Tokai Carbon Co., Ltd. President Masahisa Sanmonji

Claims (1)

[Claims] 1. A metal catalyst is added to a powdered mixed raw material of a silicon source raw material and a carbonaceous material, and the mixture is filled into a reaction vessel.
In the method of producing SiC whiskers by heating reaction in a reactor maintained at a temperature of ℃ and a non-oxidizing atmosphere, the air permeability is 500 to 2000 ml/h cm^
SiC characterized by using a closed cylindrical reaction vessel made of porous graphite material in the range of 2 mmAq
How to make whiskers. 2. The closed cylindrical reaction container has a bulk density of 0.3 to 1.4 g.
The method for producing a SiC whisker according to claim 1, wherein the SiC whisker is made of a porous graphite material of /cc. 3. A closed cylindrical reaction container with a diameter of 1 to 5 mm is placed around the reaction container made of graphite material with a bulk density of 1.5 g/cc or more.
2. The method of manufacturing a SiC whisker according to claim 1, wherein the method comprises drilling a large number of holes.