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Research on Synthesis and Oxidation Resistance of Zr2（Al（Si））4C5 Quaternary Ceramic

Author: ZhaoLei
Tutor: ChenGuiQing
School: Harbin Institute of Technology
Course: Materials Science
Keywords: Zr2（Al（Si））4C5 hot-pressing microstructure mechanical properties oxidation resistance
CLC: TQ174.1
Type: Master's thesis
Year: 2009
Downloads: 24
Quote: 2
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Abstract


Layered carbides combine properties of both metals and ceramics. They are thermal and electrical conductors, relatively soft, high elastic properties. Besides, they are elastically stiff, high melting point, high thermal stability and excellent oxidation resistance. These excellent properties above make them high temperature materials. Zr2(Al(Si))4C5 quaternary ceramic was successfully synthesized by hot-pressing method. The synthetical route, microstructure and mechanical properties of the composite were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), three-point bending test, single edge notched beam method, etc. The research of oxidation resistance of Zr2(Al(Si))4C5 quaternary ceramic was focused on.The compounds synthesized at different temperatures were analyzed by Differential thermal analysis (DTA), X-Ray diffraction (XRD) and Raman shift using ZrC, Al and carbon black powders as starting materials. The synthesis path of Zr2Al4C5 was investigated, and finally determinated the technical route.The microstructure of Zr2(Al(Si))4C5 was anisotropic and mostly consisted of elongated and rod-like and/or plate-like grains. There were some holes in it. The stiffness, Vickers hardness and flexural strength were high at room temperature. The fracture mode was transgranular. In the temperature rang of 25-1200℃, the flexural strength at high temperatures increased with temperature because of the releasing of thermal stress. The heat capacity also increased with temperature while the heat conductivity decreased. The heat expansion coefficient increased parabolizely with temperature. Thermal shock resistance results showed high resistance of crack propagation. It could be improved by decrease the grain size and improve the relavity density, which need to be further investigated.The isothermal oxidation behavior of Zr2(Al(Si))4C5 was studied. The oxidation kinetics at different temperatures were analysized. We found that at 1000℃, it obeyed the parabolic law, it was linear law at 1100℃, while at 1200℃it was as-like parabolic law. The analysis of the oxidation layer revealed that armophous Al2O3 existed below 1000℃, at 1000-1200℃the oxidation layer was composed ofα-Al2O3 and t-ZrO2. The material was serious oxidatized since no protectional oxidation layer was formed. The thickness of oxidation layer and the time went well with the parabolic law. The formation of a continous protectional oxidation layer and the amount of Si element to form aluminosilicate glass to improve the oxidation resistance of Zr2(Al(Si))4C5 at higher temperatures, which need more research.

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CLC: > Industrial Technology > Chemical Industry > Silicate > Ceramic Industry > Basic theory
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