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Method for preparing silicon nitride ceramic from low-grade diatomite

A technology of silicon nitride ceramics and diatomite, which is applied in the field of silicon nitride ceramics preparation, can solve problems such as long nitriding time, and achieve the effects of low cost, simple process and excellent performance.

Pending Publication Date: 2021-07-20
BAISHAN SCI & TECH INST +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The reaction sintering method (RS) is suitable for manufacturing parts with complex shapes and precise dimensions, and the cost is also low, but the nitriding time is very long

Method used

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  • Method for preparing silicon nitride ceramic from low-grade diatomite
  • Method for preparing silicon nitride ceramic from low-grade diatomite

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Experimental program
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preparation example Construction

[0027] Step 2, preparation of silicon nitride green body

[0028] Mix the purified diatomite obtained in step 1 with 5wt% polyvinyl alcohol and 7wt% yttrium oxide evenly, place it in a mold, and press it into a silicon nitride green body with a pressing pressure of 15-30 MPa and a pressing time of 120-360s; preferably The pressing pressure is 25Mpa, and the pressing time is 240s;

[0029] Step 3, the preparation of silicon nitride ceramics

[0030] Put the silicon nitride body into the electric furnace, feed high-purity nitrogen (99.9%), first raise the temperature to 1100°C at a heating rate of 3-5°C / min, keep it warm for 2-3h, and then heat it at 8-10°C / min The heating rate is raised to 1420°C, the temperature is kept for 4-5 hours, and then the temperature is lowered to room temperature at a cooling rate of 5-10°C / min, and silicon nitride ceramics are obtained.

Embodiment 1

[0035] Step 1. Diatomaceous earth purification

[0036] Preheat low-grade diatomite to 500°C, keep it warm for 2 hours, add 2wt% dispersant to scrub, then pickle with 50wt% sulfuric acid, keep warm at 100°C for 2h, wash with water until neutral, suction filter, dry, and crush to Particle size ≤ 40 microns, to obtain purified diatomite; low-grade diatomite is SiO 2 Diatomite with a content greater than 75% and less than 85%; SiO in purified diatomite 2 Content ≥ 90%; dispersant is sodium hexametaphosphate;

[0037] Step 2, preparation of silicon nitride green body

[0038] The diatomite after the purification is mixed with 5wt% polyvinyl alcohol and 7wt% yttrium oxide, is placed in mold (disc ), the pressing pressure is 20MPa, and the pressing time is 120s;

[0039] Step 3, the preparation of silicon nitride ceramics

[0040] Put the silicon nitride body into the electric furnace, feed high-purity nitrogen (99.9%), first raise the temperature to 1100°C at a heating rate o...

Embodiment 2

[0042] Step 1. Diatomaceous earth purification

[0043] Preheat low-grade diatomite to 500°C, keep it warm for 2 hours, add 2wt% dispersant to scrub, then pickle with 50wt% sulfuric acid, keep warm at 100°C for 2h, wash with water until neutral, suction filter, dry, and crush to Particle size ≤ 40 microns, to obtain purified diatomite; low-grade diatomite is SiO 2 Diatomite with a content greater than 75% and less than 85%; SiO in purified diatomite 2 Content ≥ 90%; dispersant is sodium hexametaphosphate;

[0044] Step 2, preparation of silicon nitride green body

[0045] Mix the purified diatomite with 5wt% polyvinyl alcohol and 7wt% yttrium oxide evenly, place it in a mold (sheet 15×15×18mm), and press it into a silicon nitride green body, the pressing pressure is 25Mpa, and the pressing time is 240s ;

[0046] Step 3, the preparation of silicon nitride ceramics

[0047] Put the silicon nitride body into the electric furnace, feed high-purity nitrogen (99.9%), first rai...

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Abstract

The invention relates to a method for preparing silicon nitride ceramic from low-grade diatomite, and belongs to the technical field of silicon nitride ceramic preparation. According to the method for preparing the silicon nitride ceramic from the low-grade diatomite, the diatomite is purified firstly, then silicon nitride powder is prepared, then a silicon nitride green body is prepared, and finally the silicon nitride ceramic is prepared. According to the method for preparing the silicon nitride ceramic from the low-grade diatomite, the low-grade diatomite is used for replacing silicon powder to serve as a raw material for preparing the silicon nitride ceramic, the cost is low, the process is simple, the prepared silicon nitride ceramic is excellent in performance, the density average value is 3.26 g / cm<3>, the bending strength average value is 537 MPa, and the compression strength average value is 2139 MPa.

Description

technical field [0001] The invention belongs to the technical field of preparing silicon nitride ceramics, and in particular relates to a method for preparing silicon nitride ceramics from low-grade diatomite. Background technique [0002] Silicon nitride is an important structural ceramic material with excellent properties, such as (1) high mechanical strength and hardness close to that of corundum. (2) Small surface friction coefficient, wear resistance, large elastic modulus, and high temperature resistance. (3) The thermal expansion coefficient is small, the thermal conductivity is large, and the thermal shock resistance is good. (4) Low density and small specific gravity. (5) Corrosion resistance and oxidation resistance. (6) Good electrical insulation. [0003] The excellent performance of silicon nitride ceramics has special use value for the working environment of high temperature, high speed and strong corrosive medium. For example, silicon nitride turbine rotor...

Claims

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Application Information

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IPC IPC(8): C04B35/584C04B35/622
CPCC04B35/584C04B35/622C04B2235/3418C04B2235/3225C04B2235/447C04B2235/6562C04B2235/6567C04B2235/6565C04B2235/46C04B2235/77C04B2235/96
Inventor 姜永久赵颖于工黄旭王宇王义鹏王继涛王继波
Owner BAISHAN SCI & TECH INST
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