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A method for preparing hfc-sic composite ceramics

A technology of multiphase ceramics, hfc-si3n4-c, is applied in the field of preparing HfC-SiC multiphase ceramics, which can solve the problems of coarse grains and poor mechanical properties of material HfC ceramics, and achieve stable phase composition and easy realization of scale. , controllable effect

Inactive Publication Date: 2015-10-28
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, HfC ceramics are very sensitive to oxygen impurities during high-temperature sintering, and there is always a layer of SiO on the surface of fine SiC particles. 2 impurities, the SiO 2 Impurities will cause grain coarsening of HfC ceramics during high temperature sintering, making the mechanical properties of HfC ceramics poor

Method used

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  • A method for preparing hfc-sic composite ceramics
  • A method for preparing hfc-sic composite ceramics
  • A method for preparing hfc-sic composite ceramics

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] HfC powder (0.1~1.5μm, 99wt%), Si 3 N 4 Powder (0.1~1.5μm, 99wt%) and carbon black (0.04~0.5μm, 99wt%) are compounded at a molar ratio of 3.74:1:3, with ethanol as the medium, Si 3 N 4 The balls are milled and mixed on a roller ball mill at a speed of 200 rpm for 24 hours, and then rotary evaporated to obtain HfC-Si 3 N 4 -C mixed dry powder; after the mixed dry powder is dry-pressed and then isostatically pressed at 250MPa to obtain HfC-Si 3 N 4 -C green body; then keep the green body under vacuum at 1300°C for 2h to obtain the HfC-SiC green body; then continue sintering at 2200°C for 0.5h under argon atmosphere to obtain HfC-40vol%SiC composite ceramics .

[0026] According to the analysis, the density of the prepared HfC-40vol%SiC composite ceramics is 100%, and the grains are fine. The average grain size of the HfC phase is only 0.8 μm, and the average grain size of the SiC phase is only 1 μm. The fracture micro-morphology of the obtained multiphase ceramics ...

Embodiment 2

[0028] HfC powder (0.1~1.5μm, 99wt%), Si 3 N 4 Powder (0.1~1.5μm, 99wt%) and carbon black (0.04~0.5μm, 99wt%) are compounded at a molar ratio of 7.46:1:3, with acetone as the medium and SiC balls as the grinding balls on a roller ball mill The rotating speed of 200 rev / min carries out ball milling and mixing for 24 hours, and then obtains HfC-Si through rotary evaporation 3 N 4 -C mixed dry powder; after the mixed dry powder is dry-pressed and then isostatically pressed at 150MPa to obtain HfC-Si 3 N 4 -C green body; then keep the green body under vacuum at 800°C for 2h to obtain the HfC-SiC green body; then continue sintering at 1900°C for 1h under an argon atmosphere to obtain HfC-25vol%SiC composite ceramics.

[0029] After analysis: the prepared HfC-25vol%SiC composite ceramics has a density of 99.7% and fine grains, and the average grain size of HfC phase and SiC phase is only 0.9 μm. The fracture micro-morphology of the obtained multiphase ceramics is as follows: ...

Embodiment 3

[0031] HfC powder (0.1~1.5μm, 99wt%), Si 3 N 4 Powder (0.1~1.5μm, 99wt%) and carbon black (0.04~0.5μm, 99wt%) are compounded at a molar ratio of 5.8:1:3, with ethanol as the medium, Si 3 N 4 The balls are milled and mixed on a roller ball mill at a speed of 200 rpm for 24 hours, and then rotary evaporated to obtain HfC-Si 3 N 4 -C mixed dry powder; after the mixed dry powder is dry-pressed and then isostatically pressed at 350MPa to obtain HfC-Si 3 N 4 -C green body; then the green body is first kept at 1400°C for 1 hour under an argon atmosphere to obtain a HfC-SiC green body; and then sintered at 2300°C for 0.5 hours under an argon atmosphere to obtain a HfC-30vol%SiC composite phase ceramics.

[0032]After analysis: the density of the prepared HfC-30vol%SiC composite ceramics reaches 99.5%, and the grains are fine, and the average grain size of the HfC phase and the SiC phase is only 1 μm; and the prepared HfC-30vol% The four-point bending strength of SiC composite c...

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Abstract

The invention discloses a method for preparing HfC-SiC multiphase ceramic. The method comprises the following steps: (a) HFC-Si3N4-C mixed powder is prepared; (b) a HfC-Si3N4-C green body is prepared; and (c) a temperature is maintained at 800-1400 DEG C under an inert atmosphere or vacuum for 1-2h, such that a HFC-SiC blank is prepared; sintering is carried out for 0.5-1h under a temperature of 1900-2300 DEG C in an inert atmosphere, such that HfC-SiC multiphase ceramic is prepared. A density of the HfC-SiC multiphase ceramic provided by the invention can reach 100%. The HfC-SiC multiphase ceramic has an average grain size smaller than 1mum. In an inert atmosphere, the ceramic can resist a high temperature of 2300 DEG C. The phase composition of the ceramic is stable. A four-point bending strength of the ceramic at a temperature of 1500 DEG C can be higher than 350 MPa. Also, with the method provided by the invention, raw materials are cheap and easy to obtain, the preparation process is simple, controllability is high, and large-scale production can be easily realized.

Description

technical field [0001] The invention relates to a method for preparing HfC-SiC composite ceramics, which belongs to the technical field of high temperature resistant ceramics preparation. Background technique [0002] At present, among the known high-temperature-resistant ceramic systems, HfC has the highest melting point of 3950°C, and it is expected to be applied in extreme high-temperature environments above 2500°C. However, the self-diffusion coefficient of HfC is low, and it is very difficult to sinter and densify, and it usually needs to be sintered at a higher temperature. In the process of high temperature sintering, HfC grains tend to grow rapidly, resulting in rough microstructure of HfC ceramics. Sciti et al. used spark plasma sintering technology to prepare single-phase HfC ceramics at a high temperature above 2400 ° C. The grains of the obtained ceramics were relatively coarse, with an average grain size of 19 μm (Journal of the American Ceramic Society, 91 [5]...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B35/56C04B35/622
Inventor 刘吉轩张国军刘海涛
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI