Synthesis of Al4SiC4 powders via carbothermic reduction: Reaction and grain growth mechanisms

Xinming Xing,Bin Li,Xinmei Hou,Guoping Bei,Kuo-Chih Chou,Junhong Chen

doi:10.1007/s40145-017-0247-z

Xinming Xing, Bin Li + Show 4 more

Open Access

https://doi.org/10.1007/s40145-017-0247-z

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Abstract

Highly pure Al4SiC4 powders were prepared by carbothermic reduction at 2173 K using Al2O3, SiO2, and graphite as raw materials. The obtained Al4SiC4 powders owned hexagonal plate-like grains with a diameter of about 200–300 μm and a thickness of about 2–6 μm. Based on the experimental results, the reaction of Al4SiC4 formation and grain evolution mechanisms were determined from thermodynamic and first-principles calculations. The results indicated that the synthesis of Al4SiC4 by the carbothermic reduction consisted of two parts, i.e., solid–solid reactions initially followed by complex gas–solid and gas–gas reactions. The grain growth mechanism of Al4SiC4 featured a two-dimensional nucleation and growth mechanism. The gas phases formed during the sintering process favored the preferential grain growth of (0010) and (1 ī0) planes resulting in formation of hexagonal plate-like Al4SiC4 grains.

Highlights

Silicon-based non-oxide ceramic materials such as SiC and Si3N4 are widely used for high temperature applications due to their excellent high temperature properties
It is worth noting that under high temperature oxidation condition, a dual protective layer consisting of inner mullite and outer alumina is formed on the Al4SiC4 surface which can improve the oxidation resistance even in water vapor atmosphere [5,9,10]
Most of the diffraction peaks is consistent with the standard card of Al4SiC4 (PDF No 35-1072) and the relative X-ray intensity ratio of the (0010) and (1 10) planes ( I(0010) / I(110) ) of Al4SiC4 is much higher than the standard PDF card, indicating a preferential grain growth orientation [28]

Summary

Introduction

Silicon-based non-oxide ceramic materials such as SiC and Si3N4 are widely used for high temperature applications due to their excellent high temperature properties. Carbothermic reduction has become a promising synthesis route for high temperature ceramics because of its low requirements on starting materials. Both industrial raw materials such as commercial alumina and quartz and natural minerals such as sintered bauxite and kaolin can be adopted as starting materials, leading to great industrialization potential [19,20,22,23,24,25]. Based on the microstructure analysis, the growth mechanism of the hexagonal plate-like Al4SiC4 grains was further evaluated using first-principles calculation

Experimental details

Results and discussion

Conclusions