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Fabrication of UHTCs by Conversion of Dynamically Consolidated Zr+B and Hf+B Powder Mixtures
Author(s) -
Brochu Mathieu,
Gauntt Bryan,
Zimmerly Tony,
Ayala Alicia,
Loehman Ronald
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02550.x
Subject(s) - materials science , ceramic , grain size , grain growth , relative density , indentation hardness , atmospheric temperature range , thermal shock , fabrication , composite material , metallurgy , analytical chemistry (journal) , microstructure , chemistry , thermodynamics , organic chemistry , medicine , physics , alternative medicine , pathology
Mixtures of Zr+B and Hf+B were shock compacted into bulk samples possessing relative densities above 95.5% and were subsequently converted to ZrB 2 and HfB 2 ceramic components by a heat treatment. The conversion temperature was varied between 1600° and 2000°C. The conversion temperature was found to have no effect on the final density of the ceramics. Theoretical densities of 72% and 62% were obtained for the converted ZrB 2 and HfB 2 ceramics, respectively. Increasing the heat‐treatment temperature promoted grain growth rather than densification for the ZrB 2 samples. The grain size increased from 1.8±0.6 to 5.6±1.3 to 8.5±3.3 μm, for heat treatments at 1600°, 1800°, and 2000°C, respectively. No grain growth was observed for the HfB 2 system, which exhibited a grain structure of 5.0±1.6, 3.3±1.5, and 4.4±2.2 μm for the same temperature range studied. Microhardness values for the ZrB 2 decreased from 19.4±0.4 to 17.2±0.6 down to 13.7±0.6 GPa, while similar hardness results of 19.1±0.8, 17.1±1.0, and 17.8±0.5 GPa were observed for the HfB 2 samples.