| Thermal Conductivity and Flexural Strength of Two-Step
Hot-Pressed SiC Ceramics |
Jingren Li,a, b Wenzhong Lua, b, * and Hai Jiangc
Pages : 15-21
DOI : 10.1080/0371750X.2022.2038672 |
| Abstract |
| Effects of two-step hot-pressing on microstructure, thermal conductivity and flexural
strength of silicon carbide (SiC) ceramics were investigated. A novel combination
of aluminium nitride (AlN), La2O3 and LaF3 was employed as sinter additives in this
study. SiC ceramics prepared through both one-step (OS samples) and two-step
(TS samples) hot-pressing method exhibited high relative densities. Compared
with OS samples, the TS samples yielded finer microstructures with both higher
thermal conductivities and flexural strengths. Impedance spectroscopy analysis
was employed to reinforce the investigation on thermal conductivity variations in
different samples. According to the analysis results, TS samples exhibited higher
fitting grain and grain boundary resistances, which stood for a lower concentration
of VSi vacancies, indicating that two-step hot-pressing is more beneficial to the
elimination of defects and improvement of thermal conductivity in SiC ceramics. On
the other hand, TS samples were strengthened by a combined effect of finer
microstructure and formation of SiC-AlN solid solution, thereby obtained higher
flexural strengths. Hence, the present study suggests that two-step hot-pressing is
more favorable to the improvement of both thermal conductivity and flexural strength
of SiC ceramics with AlN-La2O3-LaF3 additive combinations.
[Keywords: Silicon carbide, Hot-pressing, Thermal conductivity, Flexural strength,
Impedance spectroscopy analysis] |
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