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Nagano-shi, Japan

Xu G.,Shinshu University | Xu G.,ASUZAC Inc. | Yamakami T.,Shinshu University | Yamaguchi T.,Shinshu University | And 3 more authors.
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2015

In this study, in order to improve interfacial strength between CNFs and SiC matrix and to disperse CNFs uniformly in the SiC matrix, using the SiC-coated CNFs which were prepared using SiO2 powder at 14001800 °C in argon atmosphere, CNFs/SiC composites were fabricated in argon atmosphere under pressureless condition. The non-coated CNFs/SiC and SiC-coated CNFs/SiC composites reached near the full density at 2150°C. The SiC grains and the carbon agglomerates in the composites tended to be finer with an increase in amount of SiC coating on CNFs. The SiC-coated CNFs/SiC composites showed almost the same fracture toughness (4.55.0 MPa•m0.5) with the non-coated CNFs/SiC composite. On the other hand, the SiC-coated CNFs/SiC composites showed higher bending strength than the non-coated CNFs/SiC composite, and the bending strength became higher with an increase in amount of SiC coating on CNFs. The maximum bending strength was 551 MPa, which represent a 32% increase compared with that of the non-coated CNFs/SiC composite. © 2015 The Ceramic Society of Japan. All rights reserved. Source


Xu G.,Shinshu University | Xu G.,ASUZAC Inc. | Yamakami T.,Shinshu University | Yamaguchi T.,Shinshu University | And 3 more authors.
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2014

In order to improve interfacial bonding strength between carbon nanofibers (CNFs) and SiC matrix in CNFs/SiC composites and to disperse CNFs uniformly in the matrix, SiC coating on surface of CNFs was performed in argon atmosphere in the temperature range of 1400 to 1800°C using SiO2, SiO, and mixture of Si and SiO2powders (Si/SiO2powder) as silicon sources, and the modification and dispersibility of the treated CNFs were investigated. β-SiC particles were deposited on the surface of the CNFs in all the specimens at 1600-1800°C. So more SiC was formed by heating CNFs with SiO powder at 1600°C. However, the formed SiC was oxidized at higher temperature, practically, at 1800°C. This oxidation was advanced more by using SiO2and Si/SiO2powders as silicon sources and very fine carbon fibers were observed on the surface of CNFs. The dispersibilities of CNFs heated with Si/SiO2and SiO powders were superior to those of as-received CNFs, CNFs treated with NaClO3solution and CNFs heated with SiO2powder, which resulted from the advanced oxidation of CNFs and the silanol group (-SiOH) on surface of formed SiC. © 2014 The Ceramic Society of Japan. All rights reserved. Source


Xu G.,Shinshu University | Xu G.,ASUZAC Inc. | Yamakami T.,Shinshu University | Yamaguchi T.,Shinshu University | And 3 more authors.
International Journal of Applied Ceramic Technology | Year: 2014

To enhance the fracture toughness of silicon carbide (SiC) ceramics and prevent the generation of cracks and chippings in the SiC ceramics during machining process, carbon nanofibres (CNFs) were compounded with SiC. The densification and microstructure development of the CNFs/SiC composites pressureless sintered in Ar atmosphere were investigated. The fracture toughness of SiC ceramics was enhanced by the addition of 1-3 wt% CNFs, which resulted from the pullout and/or bridging effect of CNFs bonded much more closely with SiC. The addition of 3 wt% CNFs prevented the chippings from generating in the composite during precision machining process. © 2013 The American Ceramic Society. Source

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