Phase transfer process and system for preparing silicon nitride powder in batches by gas-phase chemical plasma method

A silicon nitride powder and powder technology, applied in chemical instruments and methods, nitrogen compounds, inorganic chemistry, etc., can solve the problems of high carbon content, affecting the performance of silicon nitride ceramics, and low purity of powder materials, and achieve The effect of improving powder properties

Inactive Publication Date: 2005-02-16
TSINGHUA UNIV
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Problems solved by technology

[0003] The silicon nitride powder preparation method commonly used in the prior art has following several: one, silicon powder direct nitriding method, this method is simple and easy, and cost is low, because the reaction of silicon and nitrogen is exothermic reaction, in order to make silicon powder can Full reaction, the process control is more complicated; at the same time, due to the purity of the raw material itself and the doping of the grinding process after nitriding, the purity of the powder is not high
2. Carbothermal reduction of silica. This method uses silica, which is very abundant in nature, as a raw material, coupled with a faster reaction rate, which is especially suitable for large-scale production, but the disadvantage is that the carbon content in the product is relatively high.
3. Plasma chemical vapor reaction method, which uses silicon halides (SiCl 4 SiBr 4 ... etc.) or silicon hydrohalides (SiHCl 3 SiH 2 Cl 2 ...etc) react with ammonia or nitrogen plus hydrogen in chemical vapor phase, or silane (SiH 4 ) with ammonia or hydrazine (N 2 h 4 ) undergoes a chemical vapor phase reaction, generally producing amorphous silicon nitride powder; the amorphous silicon nitride powder can be heat-treated in a nitrogen atmosphere to obtain a silicon nitride powder with an α-phase content greater than 95%, but currently the The technology is mainly limited to laboratory research, and has not been mass-produced and practically applied; and the oxygen content of the prepared powder is greater than 2-3%, and the residual chlorine content is high, reaching 60ppm, which will eventually affect the performance of silicon nitride ceramics. performance

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  • Phase transfer process and system for preparing silicon nitride powder in batches by gas-phase chemical plasma method
  • Phase transfer process and system for preparing silicon nitride powder in batches by gas-phase chemical plasma method
  • Phase transfer process and system for preparing silicon nitride powder in batches by gas-phase chemical plasma method

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Experimental program
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specific Embodiment approach

[0020] figure 1 It is a process flow chart of preparing amorphous silicon nitride powder by plasma chemical vapor phase method. First, the plasma working gases Ar and H are introduced 2 , and then start the plasma power supply, the plasma generator generates a plasma arc, and the gas flowing through the arc is heated to a high temperature of about 5000°C and enters the reactor; at the same time, the NH 3 and SiCl 4 Raw gas also enters the plasma reactor, rapid decomposition and Si 3 N 4 synthesis reaction.

[0021]

[0022] Generated Si 3 N 4 After crystallization and growth in a very short time (milliseconds), it is then transported through pipelines to a cold environment for rapid cooling, and then through a powder collection system to achieve gas-solid separation to obtain amorphous Si 3 N 4 Powder; the separated gas is discharged into the atmosphere after being treated by the tail gas treatment system.

[0023] The surface obtained by the above process is c...

Embodiment 1

[0026] Use plasma chemical vapor reaction equipment to first obtain amorphous silicon nitride powder; then through the above-mentioned continuous phase inversion heat treatment system, the atmosphere in the furnace is NH 3 :N 2 =1:1 under the condition of mixed gas, after about 1.5 hours of treatment at 600 ° C, the ammonium chloride crystals on the surface of the amorphous silicon nitride powder were removed; High-purity, ultra-fine, high-performance silicon nitride powder with high α-phase content. The performance index of the powder is as follows:

[0027] Test items

Si(%)

N(％)

O(％)

Test results

59

38.5

1.28

[0028] Fluorescent X-ray analysis has been used to detect residual chlorine.

[0029] 2. Phase composition:

[0030] Using the X-ray diffraction analysis method, the α-phase and β-phase contents of the produced silicon nitride powder are calculated as follows:

[0031] α phase: 97.5% β phase: 2.5%

[0032] 3. Pa...

Embodiment 2

[0035] Use plasma chemical vapor reaction equipment to first obtain amorphous silicon nitride powder; then through the above-mentioned continuous phase inversion heat treatment system, the atmosphere in the furnace is NH 3Under the condition of 500°C for about 2 hours, the ammonium chloride crystals on the surface of the amorphous silicon nitride powder were removed; and then heat treated at 1500-1550°C for about 1.5 hours to obtain high-purity, high α-phase content high performance silicon nitride powder. The performance index of the powder is as follows:

[0036] Test items

Si(%)

N(％)

O(％)

Test results

61.7

37.3

0.1

[0037] Fluorescent X-ray analysis has been used to detect residual chlorine.

[0038] 2. Phase composition:

[0039] Using the X-ray diffraction analysis method, the α-phase and β-phase contents of the produced silicon nitride powder are calculated as follows:

[0040] α phase: 95.5% β phase: 4.5% ...

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Abstract

A phase transfer process and equipment for preparing silicon nitride powder in batches by chemical gas-phase plasma method features that on the basis of chemical gas-phase plasma process to prepare amorphous silicon nitride powder, an additional continuous phas-transfer heat treating device is usd, which is composed of material pulsher, front and back sealed boxes, medium-temp and high-temp furnaces and cooling region. Its advantages are high output, high granularity uniformity, and low oxygen content in product (less than 0.2%).

Description

technical field [0001] The invention relates to an equipment and process for producing amorphous silicon nitride powder by plasma chemical vapor phase method and its phase inversion, in particular to a batch production of phase inversion to obtain high-purity, ultrafine, high-alpha-phase silicon nitride powder method. Background technique [0002] Silicon nitride ceramics have a series of advantages such as high hardness, high strength, wear resistance, high temperature resistance, small thermal expansion coefficient, large thermal conductivity, good thermal shock resistance, and low density. They are used in ceramic engines, machining, microelectronics, Space science and nuclear power engineering and other fields have extremely broad application prospects. Related products such as silicon nitride ceramic cutting tools, silicon nitride ceramic bearings, automotive engine valves, automotive turbochargers, heaters, various wear-resistant, high-temperature resistant, corrosion...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B21/068
Inventor 齐龙浩白万杰潘伟曹阳
Owner TSINGHUA UNIV
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