Low temperature sintering of Hf0.95Nb0.05B2-based ceramics with submicron-scaled grains and enhanced mechanical properties |
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| Affiliation: | 1. Hubei Longzhong Laboratory, Wuhan University of Technology Xiangyang Demonstration Zone, Xiangyang 441000, China;2. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China;3. School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China;1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, PR China;2. Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, PR China;3. Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China;1. Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, PR China;2. Beijing Mechanical Equipment Institute, Beijing 100039, PR China;3. College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, No.29 Jiangjun Ave., Nanjing 211106, PR China;4. School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China;1. Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA;2. Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA |
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| Abstract: | Hf0.95Nb0.05B2 ceramics and their composites containing 20 vol% SiC were prepared via high-pressure spark plasma sintering in the study. The densification, microstructures, and mechanical properties of the prepared materials were then investigated. It is challenging to achieve full densification of HfB2 ceramics, even with markedly refined Hf0.95Nb0.05B2 solid solution powder under the sintering conditions of 2000 °C/30 MPa. However, under the sintering conditions of 1700 °C/200 MPa, a dense microstructure of Hf0.95Nb0.05B2 ceramics was achieved. Moreover, the Hf0.95Nb0.05B2-20 vol% SiC composite was densified at a lower temperature (1500 °C) and exhibited ultrafine grains (300 nm) and high-density defects, including stacking faults, Lomer-Cottrell locks, and twins, thus resulting in exceptional comprehensive mechanical properties, such as ultra-high hardness (32 GPa) and significantly improved fracture toughness (5.2 MPa.m1/2). |
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| Keywords: | High pressure sintering Microstructure Mechanical property |
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