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Method for synthesizing isotropic silicon nitride powder adopting hollow type annular material-distribution

A technology for combustion synthesis and silicon nitride powder, which is applied in chemical instruments and methods, nitrogen compounds, inorganic chemistry, etc. Powder production efficiency and product purity, synthetic product composition and uneven microscopic morphology, etc., to avoid heat accumulation, high α-phase content, and uniform and fine particles

Inactive Publication Date: 2008-06-18
UNIV OF SCI & TECH BEIJING
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The inhomogeneity of the synthetic product often occurs in the process of combustion synthesis of silicon nitride powder, which greatly affects the production efficiency and product purity of combustion synthesis silicon nitride powder, and also increases the difficulty of subsequent separation and treatment, seriously Large-scale industrial production and application of combustion-limited synthesis of silicon nitride powder
[0008] The object of the present invention is to provide a method for synthesizing homogeneous silicon nitride powder by combustion of a hollow annular cloth, which solves the problem of various parts of the reaction mixture system caused by the different conditions of heat loss and heat accumulation in the conventional combustion synthesis method. The problem of uneven distribution of the temperature field, overcomes the problem of inhomogeneity in the composition and microscopic morphology of the synthetic product existing in the conventional combustion synthesis method, especially the difference in the phase composition, grain shape and impurity content of the internal and external layers of the synthetic product bigger problem

Method used

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  • Method for synthesizing isotropic silicon nitride powder adopting hollow type annular material-distribution
  • Method for synthesizing isotropic silicon nitride powder adopting hollow type annular material-distribution
  • Method for synthesizing isotropic silicon nitride powder adopting hollow type annular material-distribution

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0046] The raw materials used in this example are silicon powder with an average particle size of 25 μm (purity greater than 98.5%) and silicon nitride powder with an average particle size of 1 μm (purity greater than 96%, and α-phase content of about 93%). Dosing and grinding and mixing according to the weight ratio, the proportioning ratio is Si:Si 3 N 4 =50:50, the total weight of the reaction mixture was 4.2 kg. The above-mentioned grinding and mixing of the reaction mixture is carried out in the following manner: first, the silicon powder is ground and mixed in the ball mill barrel of the agitating ball mill with absolute ethanol as the ball milling medium for 6 hours, and then dried in a vacuum oven at 60°C. Then add inert diluent silicon nitride powder and grind and mix on a vibrating mill for 1 hour. The reaction mixture was then placed in a cylindrical porous graphite crucible according to the attached figure 1 The hollow annular cloth is shown, wherein the cylindr...

Embodiment 2

[0049] The raw materials used in this example are silicon powder with an average particle size of 17 μm (purity greater than 98%) and silicon nitride powder with an average particle size of 2.2 μm (purity greater than 98%, and α-phase content of about 95%). Dosing and grinding and mixing according to the weight ratio, the proportioning ratio is Si:Si 3 N 4=52.5:47.5, the total weight of the reaction mixture was 4 kg. The above-mentioned grinding and mixing of the reaction mixture is carried out in the following manner: first mix the silicon powder and the inert diluent silicon nitride powder in the ball mill barrel of the agitating ball mill with absolute ethanol as the ball milling medium for ball milling for 8 hours for grinding and mixing, and then grind and mix in the electric heating Drying was performed in an oven at 65°C. Then the dried silicon powder and the inert diluent silicon nitride powder mixture were ground and mixed on a roller mill for 2 hours. Then the rea...

Embodiment 3

[0051] The raw materials used in this example are silicon powder with an average particle size of 47 μm (purity greater than 98.5%) and silicon nitride powder with an average particle size of 1.5 μm (purity greater than 96%, and α-phase content of about 90%). Dosing and grinding and mixing according to the weight ratio, the proportioning ratio is Si:Si 3 N 4 =55:45, the total weight of the reaction mixture was 3.5 kg. The above-mentioned grinding and mixing of the reaction mixture is carried out in the following manner: first, the silicon powder and the inert diluent silicon nitride powder are respectively ball milled in the ball mill barrel of the agitating ball mill with absolute ethanol as the ball mill medium for 6 hours, and then in a vacuum oven at 60 °C for drying. The mixture of silicon powder and silicon nitride powder, an inert diluent, was then ground and mixed on a vibrating mill for 3 hours. Then these three reaction mixtures with different component ratios wer...

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Abstract

The invention discloses a homogeneous silicon nitride powder synthetic method of hollow ring-shaped cloth combustion in the inorganic non-metal material domain, which is characterized by the following: grinding to mix the silicon powder and silicon nitride powder at different proportions; placing the material in the combustion synthetic reaction device with poromeric hollow pipe according to the hollow ring-shaped cloth method after drying; charging 1-20 Mpa nitrogen gas in the vacuum device; inducing the combustion synthetic reaction through igniting. The invention realizes the complete nitridation of whole reactant at isothermal pattern, which improves the uniformity of silicon nitride powder.

Description

technical field [0001] The invention belongs to the field of inorganic non-metallic materials, and in particular provides a method for synthesizing homogeneous silicon nitride powder by burning hollow annular cloth. Background technique [0002] Silicon nitride is a synthetic non-oxide ceramic. It has the characteristics of low density, low specific gravity, high hardness, high strength, corrosion resistance, oxidation resistance, wear resistance, high elastic modulus, high temperature resistance, small thermal expansion coefficient, large thermal conductivity, thermal shock resistance and good electrical insulation performance. , its mechanical properties and thermal properties are significantly better than general oxide ceramics. Silicon nitride ceramic products and silicon nitride-based composite ceramic products manufactured by different sintering processes can be widely used in cutting tools, bearings, engine parts, as well as chemical industry, metallurgy, machinery, ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B21/068C04B35/584C04B35/626
Inventor 葛昌纯王飞
Owner UNIV OF SCI & TECH BEIJING
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