JPS5860609A - Preparation of high purity sic - Google Patents

Abstract

PURPOSE:To prepare high purity SiC, by compounding a granular carbonaceous material to the granulated mixtue of SiO2 powder and C powder, heating the composition at high temperature in a chlorine-containing atmosphere to dissipate the impurities as chlorides and at the same time to react the produced gaseous Si oxide with said granular carbonaceous material, and then separating and removing the reaction residue. CONSTITUTION:SiO2 powder obtained usually by crushing quartzite is mixed with C powder such as petroleum coke powder (the molar ratio of SiO2 to C is about 1), and granulated to granule diameter of 2-10mm.. The granulated mixture is compounded with granular carbonaceous material such as charcoal, or the granulated mixture is coated with the carbonaceous material, and the composition is heated at >=1,600 deg.C, especially at 1,700-2,000 deg.C in an atmosphere of Cl2 or a chloride to dissipate the impurites of the raw material, e.g. Al2O3, Fe2O3, etc. as chlorides. SiO2 in the granulated mixture is made to react with C simultaneously to the above dissipation to obtain gaseous Si oxide, which is released from the granulated mixture and reacted with the granular carbonaceous material to obtain SiC. The SiC-containing material is separated from the reaction residue of the above granulated mixture to obtain highly pure SiC having a purity of >=99.95%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on 8i0. Powder and carbon powder'f: Relating to a method for producing high-purity SICR as a raw material.

High-purity S50 fine powder is expected to be used as a raw material for sintering, as a filler for synthetic resins, and as a plating material for parts of metal tools that are prone to wear.It is currently considered the most promising along with 8i and N4. This is the material that is used.

A conventional method for producing SiC is to mix nite (8i0) and coke (C) and heat the mixture in an Acheson furnace (1/2F), which reacts according to the following equation to produce SiC.

8i0. +JC=8iC+CoCO By the way, the above silica stone usually contains AJ! 011,F
e, 0. Contains a total of nearly 1/1 impurity such as
These non-volatile impurities are concentrated and accumulated in the product SiC,
This hindered the high purity of StC.

To solve this problem, methods have been used to remove impurities as chlorides by passing the raw material through an ESiC production furnace on C6 or HCI rt or by mixing NaCJ, which becomes chloride vapor at high temperatures, with the raw material. It has not yet been possible to increase the purity to that level.

The present inventor previously developed a method for producing high-purity 8iC by mixing and granulating silica powder and carbon powder, and adding granular carbonaceous material e to this granulated product.
The above-mentioned granules are heated to 1000°C or higher in a non-oxidizing atmosphere, and the sio and C in the above-mentioned granules are reacted to form gaseous silicon. Generates oxides and releases them outside the granules,
This was reacted with the above-mentioned granular soft wood or coated carbon material to produce 8jC and T.A method for producing SIC using the following (])\(2+ formula was proposed.

8fO, +C→SiO+CO (1) 8i0 +CoC-+8 i c+co (21
By the way, the above method uses high purity SiC of about 998%.
can be easily manufactured, but? 9! ? In order to obtain 8iC of 3% or more, 5iO1, C and generated 17, which are granule raw materials,
Collecting 11SiO and producing SiC? , the purity of the carbon material must be increased.

The present invention typically has an easily obtainable purity of 8i0! The purpose is to provide a method for producing extremely pure SiC using SiC and C. Silica powder and carbon powder are mixed and granulated, and granular carbonaceous material is blended into this granulated material. The product or the above granules are coated with carbonaceous material and heated to a temperature of ii, co"c or higher in a chlorine or chloride atmosphere,
In addition to volatilizing impurities in raw materials as chlorides,
StO and C in the granules are reacted and released as gaseous silicon oxide to the outside of the granules, which is then reacted with the granular carbon material or coated carbon material to form SiC, and this SiC-containing material is This method is characterized by separating the granules from the reaction residue.

The present invention will be explained in detail below.

The raw material 5tOt powder is usually prepared by crushing silica stone.
Ru. The particle size should be as thin as possible in order to increase the strength and reactivity of the granulated product, and should be at least less than qμ. Preferably it is Dada μ or less.

Most carbon materials such as petroleum coke, coal coke, and charcoal can be used as the carbon powder, and the particle size is similar to that of silica powder.

Of course-1, the above-mentioned silica stone and carbonaceous material may be mixed and pulverized. In any case, the crusher is a ball mill, vibratory mill,
A centrifugal marl mill or the like is used.

A pan pelletizer, marmerizer, pre-nut machine, etc. is used to granulate the mixed powder.
Aqueous solutions of MC, PVA, gum arabic, etc. may be used as the primary binder. It is appropriate to select the size of the granules within the range of 4 to 1 Ow. If the diameter is less than 10mm, the reaction will be hindered due to poor gas ventilation, and if the diameter is more than 10mm, the reaction rate inside the granules will be slow, and SiO2 will be generated in the gas phase. etc. become difficult to release ◇8i0.
The mixing ratio of C and StO is important because they react according to the first stage reaction formula (1) shown below.

and C are mixed in approximately equimolar amounts and granulated.

S i O, -1-C→S iO+cO (1) Also, 8i0 generated from the above granulated material reacts with the carbonaceous material according to equation (2) to generate 8iC.

8 i 0+2C-+S i C+Co (2
1 Therefore, C as a raw material for coating or carbon granules
It is desirable to have high reactivity, high porosity, and high surface area. In terms of material, it is charcoal, activated carbon, carbon black, etc., and expressed in terms of specific surface area, it is 1 ootyt.
7y or more is desirable.

Also, from the viewpoint of reactivity, it is preferable to use a material with a low degree of black ship formation.

And in the case of coating, powder of about 71/-μ or less is suitable, and in the case of carbon granules! ~/jxx or so.

The carbon granules may be granulated carbon powder.

Coating with carbon powder can be performed by adding carbon powder to a granulated product and using a granulator.

The amount of granular carbonaceous material or coated carbonaceous material to be used is determined by the amount of Sin! in the granules in order to completely collect 8i0. It is used in a ratio of 1 to q mol per mol.

(Hereinafter, silica and carbonaceous granules coated with carbon powder, or granules mixed with carbon granules will be referred to as raw materials.) The raw material heating device is not particularly limited. ,
Any material that can provide a C6 or chloride atmosphere may be used. In this case, the heating temperature is preferably 1400°C or higher, but
Preferably it is 1700-200Q°C.

The amount of C/ or chloride gas to be introduced is approximately 0 l-II 1 minute per 1 kg of granules in the raw material. The chloride gas may be H (J). A substance that becomes chloride vapor at high temperature outside the gas, such as NaCl, may be mixed into or mixed with the granules as a raw material.Na
In the case of C1, it is sufficient to add 03 to S% to the raw material granules. After heating, unreacted NaCl condenses in the low temperature section and must be removed by washing with water afterwards. MCI
It can be used suitably as there is no condensation. Also, C
When using Jffi, N 81 C4 is generated or
There is no problem because it evaporates at low temperatures and is emitted. Also, impurities in raw materials AI! , O,, Fe, O, etc. are often removed from the product as chlorides, etc., but if this is done in a closed equipment, some may condense in the low temperature parts and enter the product. It is necessary to remove it. This removal can be easily done by washing with water or the like.

As described above, the SiC manufacturing method of the present invention uses extremely pure S
iC is what is generated.

Next, a simple embodiment of the present invention will be explained.

FIG. 7 shows an example of a vertical furnace used for continuous production of 8iC. The raw material 8 is continuously supplied from the input port 2 of the vertical furnace 1 . In addition, a table feeder number is provided at the bottom, and a T for continuously taking out the granulated material after the reaction has been completed. Further, 5 is a heater which heats the raw material 8 that is descending inside the furnace 1.

The raw material 8 is introduced from the inlet 6 during this descending process.
When it comes into contact with ffi or H(J) at high temperature, the tOs, Fe, o, contained in the raw material 8 are volatilized as chlorides and discharged from the discharge lower.

Moreover, FIG. 2 shows a graphite crucible IO, and 11 is a lid. A discharge port 12 is provided in the lid 11. Also,
A graphite perforated plate 18 is provided at the bottom of the crucible 10, and a C4 or HC plate provided through the lid is provided below the perforated plate 1B.
The tip of the introduction tube 14 such as L is open. This crucible lO
The raw material art is placed in the tank, sealed, and heated to t'too°C or higher, and Cl5R or HCJ or the like is introduced from the introduction pipe 14. As a result, impurities in the raw material 8 become chlorides and volatilize, producing StC with high purity.

Next, the production of 8iC using the above apparatus will be explained using Examples and Comparative Examples.

Example 1 Silica powder and carbon powder (each with a purity of 97%) were mixed and granulated in approximately equal molar amounts to make rough carbon powder (C purity: 7%).
was coated at a ratio of 23 moles to 7 moles of silica. This double-structure raw material 8 is continuously fed from the input port 2 of a vertical furnace l whose top is completely sealed as shown in Fig. 1, and at the same time the reaction conditions are 1ts-o to ttzo”c
, the residence time was 1 hour. The product was removed using a yellow spherical shell, washed with water, acid washed (regia regia, 7-acid), and analyzed as 8iC9 de? It was 7%. Ma-r, t t81
β-8iC300P9 was obtained through continuous operation.

Comparative Example 1 The purity of β-8iC obtained by carrying out all the same operations as in Example 1 except that C1h was not passed was examined. The result was 99.7%.

Example 2 Same double structure raw material as Example 1. Inner diameter aoo'xxφ height 7
Place it in a graphite crucible 10 of 5300 Rm, seal it, and heat it to 1900 Rm.
℃ for 1 hour, during which time C.
4 gases were injected (see Figure 2). The product had a yellow color and was analyzed after decarburization, water washing, and pickling (hydrochloric acid, Fluorine M), and the result was β-8iC99'l! It was r%.

Example 3 For 0.1 mole of 8i in the granulated product of sio and C powder,
Example 2 Raw material pellets containing 3 moles of granular carbonaceous material were
β-8iC was produced under the same conditions except that H(J was used instead of C/*) and analyzed. As a result, the amount of β-8iC produced was 3% of Tadeta.

One 8iC was manufactured. What is the purity of β-8iC? ? , A%
Met.

Example 4

Claims (1)

[Claims] Silica powder and carbon powder P are mixed and granulated, and the granules are blended with granular carbonaceous materials, or the granules are coated with powdery carbonaceous materials in a chlorine or chloride atmosphere under 11. 00°C or higher to volatilize impurities in the raw materials and remove 8i0. and C are reacted and released as gaseous silicon oxide to the outside of the granules.
8 by reacting with the granular carbon material or coated carbon material.
A method for producing high-purity SiC, which comprises separating iC and 1 containing SiC from the reaction residue of the granules.