Microstructural analyses of B sub(4)C-CeO sub(2) and B sub(4)C-La sub(2)O sub(3) ceramics

• Published in: Journal of nuclear materials 2011-10, Vol.417 (1-3), p.659-662
• Main Authors: Sakamoto, Tatsuaki, Sun, Shu-Chen, Furuno, Tomoya, Kajioka, Michio, Nakai, Kiyomichi, Kurishita, Hiroaki, Kobayashi, Sengo, Wu, Wen-Yuan, Tu, Gan-Feng, Matsuda, Seiji
• Format: Article
• Language: English
• Subjects: Borides; Coherence; Grain boundaries; Hardness; Porosity; Presses; Reduction; Sintering (powder metallurgy)
• ISSN: 0022-3115
• DOI: 10.1016/j.jnucmat.2011.01.072

Effects of additions of CeO sub(2) and La sub(2)O sub(3) on microstructure and mechanical properties of B sub(4)C fabricated under and without hot press have been investigated. Vickers hardness and fracture strength are increased by hot press due to the reduction of porosity because the sintering rate is enhanced. Hardness is increased by the reduction of porosity because crack probably occurs when the hardness is measured due to pore as an initiation point of crack. Hardness increases with increasing additions of CeO sub(2) and La sub(2)O sub(3) because porosity decreases due to the formation of CeB sub(6) and LaB sub(6) on the grain boundary of B sub(4)C, respectively. The borides are formed through reaction between solid phases, which might induce coherent boundary between boride and B sub(4)C. Such coherency also contributes to strengthening the grain boundary of B sub(4)C. The addition of CeO sub(2) enhances the sintering rate more than that of La sub(2)O sub(3), resulting in higher hardness of B sub(4)C-CeO sub(2) than that of B sub(4)C-La sub(2)O sub(3).