Papers by Author: Shuzo Kanzaki

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Authors: Koji Watari, Manuel E. Brito, Takaaki Nagaoka, Motohiro Toriyama, Shuzo Kanzaki
205
Authors: Yu Ping Zeng, Naoki Kondo, Kiyoshi Hirao, Hideki Kita, Tatsuki Ohji, Shuzo Kanzaki
Abstract: Silicon nitride ceramics was prepared by tape casting nonaqueous ceramic slurries, laminating the green ceramic tapes, and gas pressure sintering in nitrogen atmosphere. Lu2O3 and SiO2 were used as the sintering additives, and 3 wt.% β-Si3N4 seed was added to enhance β-Si3N4 grain growth unidirectionally. The seeded and tape-cast Si3N4 showed very good high temperature bending strength at 1500oC, when the stress applied along with the grain alignment direction. This was attributable to the formation of a high melting point grain boundary phase and the fibrous Si3N4 grains alignment. After exposure in air at 1500oC for up to 100 h, the oxidation products formed on the Si3N4 surface consist of Lu2Si2O7 and SiO2. The bending strength of the oxidized and tape-cast Si3N4 was degradation, the strength decrease was associated with the formation of new defects on the surface and the interface between the oxide layer and the Si3N4 bulk.
483
Authors: Shunkichi Ueno, Daniel Doni Jayaseelan, Naoki Kondo, Tatsuki Ohji, Shuzo Kanzaki, Hua Tay Lin
Abstract: Various coating methods of EBC layer for silicon nitride were discussed. High density EBC layer was successfully coated by different techniques such as sputtering, sol-gel and reaction sintering methods. Water vapor corrosion and recession mechanisms of Lu2Si2O7 which is a potential material for EBC were discussed. The problems in the development of EBC revealed by corrosion tests were summarized. The most important problem addressed here was the corrosion of silica at grain boundary. Due to corrosion of silica at the boundary, formation of porous surface is inevitable, then the silicon nitride substrate gets easily oxidized and/or corroded by water vapor. To resolve this issue, we propose a new EBC material without boundary silica and the corrosion mechanism of this improved EBC material is discussed.
449
Authors: Tatsuya Okada, M. Obata, Motohiro Toriyama, Shuzo Kanzaki
129
Authors: Yu Ping Zeng, Naoki Kondo, Kiyoshi Hirao, Tatsuki Ohji, Shuzo Kanzaki
Abstract: Silicon nitride ceramics with and without β-Si3N4 seed addition were prepared via tape casting nonaqueous ceramic slurries, laminating the green ceramic tapes, and gas pressure sintering the green bodies in nitrogen atmosphere. Lu2O3 and SiO2 were used as sintering additives. The results showed that the rod-like β-Si3N4 seed was helpful to enhance β-Si3N4 grain growth unidirectionally. The elongated grains grown from seeds were preferentially oriented parallel to the casting direction, resulting in anisotropic microstructure. When a stress was applied with along the grain alignment, the bending strength of the tape-cast Si3N4 with 3 wt% β-Si3N4 seed addition measured at 1500oC was 738 MPa, which was almost the same as the room temperature bending strength 739 MPa, and the fracture energy can be improved from 301 J/m2 at room temperature to 781 J/m2 at 1500oC. The large fracture energy and bending strength at 1500oC were attributable primarily to the unidirectional alignment fibrous grains and a high melting point grain boundary phase.
1219
Authors: Zoltán Lenčéš, Kiyoshi Hirao, Michael J. Hoffmann, Shuzo Kanzaki
865
Authors: Manuel E. Brito, Kiyoshi Hirao, Masaki Yasuoka, Shuzo Kanzaki
413
Authors: Suzuya Yamada, Kiyoshi Hirao, Shuji Sakaguchi, Yukihiko Yamauchi, Shuzo Kanzaki
811
Authors: Kiyoshi Hirao, Akihiko Tsuge, Manuel E. Brito, Shuzo Kanzaki
63
Authors: Guo Jun Zhang, Tatsuki Ohji, Shuzo Kanzaki
Abstract: Based on the proposed inorganic reactions a series of high performance hexagonal boron nitride-containing composites (BNCC), include SiC-BN, Si3N4-SiC-BN, SiAlON-BN, AlN-BN, Al2O3-BN, AlON-BN and mullite-BN, have been prepared via reactive hot pressing or pressureless reactive sintering. Various boron-bearing components such as B, B4C, AlB2, SiB4, SiB6, B2O3 or H3BO3, 9Al2O3×2B2O3 (9A2B) and 2Al2O3×B2O3 (2AB) are used as the boron source. On the other hand, nitrogen gas or solid state nitirgen-bearing metal nitrides such as Si3N4 and AlN can be used as the nitrogen source. The in situ synthesized composites demonstrated homogeneous and isotropical microstructures with very fine (nano-sized) BN platelets or their agglomerates distributed in the matrixes. These composites showed high strength, low elasticity and improved strain tolerance. In this article the reaction design, thermodynamics, reaction mechanisms, reactive hot pressing or pressureless reactive sintering, microstructures and mechanical properties will be discussed.
1385
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