Method for preparing high-density hexagonal boron nitride ceramic material

Patent metadata

Field	Value
Publication number	US-2016304346-A1
Application number	US-201415100837-A
Country	US
Kind code	A1
Filing date	Aug 14, 2014
Priority date	Aug 11, 2014
Publication date	Oct 20, 2016
Grant date	—

Abstract

A method for preparation of a high-density hexagonal boron nitride (hBN) ceramic material is disclosed. According to the method, the surface of hBN powder is coated with an evenly-dispersed SiO 2 nanoparticle layer using tetraethyl orthosilicate as a precursor, and then the high-density hBN ceramic material is obtained by pressureless sintering. The relative density of the prepared hBN ceramic material is over 80%.

First claim

1 . A method for preparing a high-density hexagonal boron nitride (hBN) ceramic material, comprising:
(1) adding hBN powder into deionized water, and evenly stirring the hBN powder to obtain mixture of hBN powder and deionized water; (2) adding ethanol dropwise into the mixture obtained through the step (1), causing the mass ratio of the dropwise added ethanol to the mixture to be 0.08-0.1; then, continuing to add ammonia water dropwise into the mixture to cause the pH of the solution to be 9-10; after the mixture is evenly mixed, continuing to add mixed solution of tetraethyl orthosilicate and ethanol dropwise until the mole ratio of tetraethyl orthosilicate in the mixed solution to deionized water in the step (1) is (1:4)-(1:8); after the mixed solution is added dropwise, sealing the bottle, and continuing to react for 5-20 h; (3) after the reaction in the step (2) is over, filtering the obtained powder, drying the powder, and grinding and sieving the powder; (4) pre-sintering the sieved powder obtained through the step (3) in a high vacuum furnace, and evenly grinding and sieving the powder again after the pre-sintering; (5) causing the powder obtained through the step (4) to undergo cold isostatic press molding, undergo high-temperature pressureless sintering in the atmosphere of N 2 and then undergo heat preservation for 1-3 h, so as to obtain a sample; (6) after the sintering experiment is over, performing cooling and taking out the sample.

2 . The preparation method according to claim 1 , wherein the purity of the hBN powder is greater than 98%, and the particle size of the hBN powder is not larger than 10 microns; and the mass ratio of the hBN powder to the deionized water is 0.008-0.015.

3 . The preparation method according to claim 1 , wherein the stirring conditions in the step (1) are that magnetic stirring is performed; the stirring speed is 500-1000 rpm, and the stirring time is 1-10 h.

4 . The preparation method according to claim 1 , wherein in the step (2), the dripping speed of the ethanol is 1-10 ml/min, the dripping speed of ammonia water is 1-10 ml/min, and the dripping speed of the mixed solution of tetraethyl orthosilicate and ethanol is 1-20 ml/min.

5 . The preparation method according to claim 1 , wherein in the step (2), in the mixed solution of tetraethyl orthosilicate and ethanol, the mass ratio of tetraethyl orthosilicate to ethanol is (1:5)-(1:10).

6 . The preparation method according to claim 1 , wherein in the step (3), the conditions of powder drying are that the powder is dried for 10-30 h at 90-110° C.; and the conditions of powder grinding are that the powder is sieved through a 200-mesh sieve 2-4 times.

7 . The preparation method according to claim 1 , wherein in the step (4), the conditions of powder pre-sintering are that the pre-sintering temperature is 700-900° C., and the pre-sintering time is 0.5-5 h; and the grinding conditions are that the powder is sieved through a 200-mesh sieve 2-4 times.

8 . The preparation method according to claim 1 , wherein in the step (5), the molding pressure of cold isostatic press molding is 100-200 MPa.

9 . The preparation method according to claim 1 , wherein in the step (5), the sintering temperature is 1600-1900° C.

Assignees

• Univ Hohai

Inventors

• Zhang Jianfeng
• Wu Yuping
• Li Gaiye
• Hong Sheng
• Guo Wenmin

Classifications

• C04B2235/668

  Pressureless sintering · CPC title

• C04B2235/386

  Boron nitrides · CPC title

• C04B35/64

  Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F}) · CPC title

• C04B2235/77

  Density · CPC title

• C04B2235/661

  Multi-step sintering · CPC title