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首页> 外文OA文献 >Microstructure and Mechanical Properties of Nanofiller Reinforced Tantalum-Niobium Carbide Formed by Spark Plasma Sintering
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Microstructure and Mechanical Properties of Nanofiller Reinforced Tantalum-Niobium Carbide Formed by Spark Plasma Sintering

机译：放电等离子烧结纳米填料增强钽铌碳化物的组织与力学性能

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摘要

Ultra high temperature ceramics (UHTC) are candidate materials for high temperature applications such as leading edges for hypersonic flight vehicles, thermal protection systems for spacecraft, and rocket nozzle throat inserts due to their extremely high melting points. Tantalum and Niobium Carbide (TaC and NbC), with melting points of 3950°C and 3600°C, respectively, have high resistivity to chemical attack, making them ideal candidates for the harsh environments UHTCs are to be used in. The major setbacks to the implementation of UHTC materials for these applications are the difficulty in consolidating to full density as well as their low fracture toughness. In this study, small amounts of sintering additive were used to enhance the densification and Graphene Nanoplatelets (GNP) were dispersed in the ceramic composites to enhance the fracture toughness. While the mechanisms of toughening of GNP addition to ceramics have been previously documented, this study focused on the anisotropy of the mechanisms. Spark plasma sintering was used to consolidate both bulk GNP pellets and near full relative density TaC-NbC ceramic composites with the addition of both sintering aid and GNP and resulted in an aligned GNP orientation perpendicular to the SPS pressing axis that allowed the anisotropy to be studied. In situ high load indentation was performed that allowed real time viewing of the deformation mechanisms for enhanced analysis. The total energy dissipation when indenting the bulk GNP pellet in the in-plane GNP direction was found to be 270% greater than in the out-of-plane orientation due to the resulting deformation mechanisms that occurred. In GNP reinforced TaC-NbC composites, the projected residual damaged area as a result of indentation was 89% greater when indenting on the surface of the sintered compact (out-of-plane GNP orientation) than when indenting in the orthogonal direction (in-plane GNP orientation) which is further evidence to the anisotropy of the GNP reinforcement.
机译：超高温陶瓷（UHTC）因其极高的熔点而成为高温应用的候选材料，例如超音速飞行器的前缘，航天器的热保护系统以及火箭喷嘴的喉管嵌件。钽和碳化铌（TaC和NbC）的熔点分别为3950°C和3600°C，对化学腐蚀具有很高的抵抗力，使其成为使用UHTC的恶劣环境的理想选择。在这些应用中使用UHTC材料很难将其固结到全密度，并且其断裂韧性低。在这项研究中，少量的烧结添加剂被用来增强致密性，并且石墨烯纳米片（GNP）被分散在陶瓷复合材料中以增强断裂韧性。虽然先前已记录了将GNP添加到陶瓷中的增韧机理，但这项研究集中于机理的各向异性。火花等离子体烧结用于固结块状GNP球粒和接近全相对密度的TaC-NbC陶瓷复合材料，同时添加烧结助剂和GNP，并导致垂直于SPS压制轴的GNP取向对齐，从而可以研究各向异性。在原位进行了高负荷压痕，可以实时查看变形机制以进行增强分析。由于在平面内GNP方向上压入大块GNP颗粒，总的能量耗散比在面外GNP方向上大270％，这是由于产生了变形机制。在GNP增强的TaC-NbC复合材料中，由于压痕导致的预计残余损坏面积，比在正交方向上压痕（在GNP方向上压痕）大89％。平面GNP方向），这进一步证明了GNP增强材料的各向异性。

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