Abstract
To investigate the HfB2 on microstructure and oxidation resistance of ZrB2-30 vol% SiC, ZrB2-30 vol% SiC composites with different amounts of HfB2 (4, 8, and 12 vol%) were consolidated by Spark Plasma Sintering method (SPS). Microstructural evaluations were done by scanning electron microscopic (SEM). To investigate the oxidation resistance, the samples were placed in a box furnace at the temperature of 1400 C for different times. The samples were weighed before and after the oxidation and the Δw was applied as a criterion of oxidation. The thickness of SiO2 layer and Si depleted layer were also used as oxidation criterion. The results showed that HfB2 addition caused to decrease Δw and better oxidation resistance.
Highlights
Due to the growing tendency for high-temperature oxidation resistance materials for several structural and aerospace applications, ultra-high temperature ceramics (UHTCs) have been in the center of attention during last recent years
It has been confirmed that when n>2.00, the oxidation process is parabolically controlled by diffusion or in other word, the diffusion rate of O atoms plays the key role in oxidation behavior of the composite[18]
Results indicated that the presence of HfB2 can promote the formation of HfO2, which reduces the diffusion rate of oxygen atoms and results in improved oxidation resistance of the composite
Summary
Due to the growing tendency for high-temperature oxidation resistance materials for several structural and aerospace applications, ultra-high temperature ceramics (UHTCs) have been in the center of attention during last recent years. To reduce the aerodynamic friction-derived heat in primary aerospace vehicles, high radios and thickness components were designed. Sharp leading edges have been used in new generation of aerospace components which can improve the lift/drag ratio and overall efficiency of the vehicle Anyway, such designs can result in higher friction-derived heat input and promote hightemperature reactions at the sharp leading edges. It has been revealed that HfB2 (melting point: 3380°C) as another member of HUTCs family, improves the mechanical properties and thermal shock resistance of ZrB2-SiC composites, and can influence the oxidation behavior of the composite, as it forms a protective oxide layer, HfO2[5, 7,8,9]. The present study is dedicated to the role of HfB2 in oxidation behavior of ZrB2-SiC-HfB2 ternary composites
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