著者

Fumio SAWA Manwal HUSSAIN Atsushi NAKAHIRA Shigehiro NISHIJIMA Koichi NIIHARA Toichi OKADA

出版者

CRYOGENICS AND SUPERCONDUCTIVITY SOCIETY OF JAPAN

雑誌

TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan) (ISSN:03892441)

巻号頁・発行日

vol.30, no.9, pp.415-419, 1995-09-25 (Released:2010-02-26)

参考文献数

9

被引用文献数

1

---

Hybrid materials involving epoxies with different numbers of reactive groups have been prepared to determine the molecular design of epoxies with high fracture toughness at cryogenic temperatures. To answer the opponent demands, that is, strong and flexible chains, hybrid materials were proposed. Two types of epoxy resin with different numbers of epoxy groups were mixed and cured by changing the mixing ratio. Fracture toughness, flexural strength, dielectric loss tangent, and thermal contraction of the hybrid epoxy resins were measured down to cryogenic temperatures. A hybrid material with high fracture toughness, even at liquid helium temperature, was successfully developed and hence the molecular design orientation was confirmed to be possible.

著者

Son Thanh NGUYEN Tsuyoshi TAKAHASHI Ayahisa OKAWA Hisayuki SUEMATSU Koichi NIIHARA Tadachika NAKAYAMA

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.129, no.4, pp.209-216, 2021-04-01 (Released:2021-04-01)

参考文献数

33

被引用文献数

12

---

In the emerging era of aircraft industry, silicon carbide (SiC) is regarded as an appropriate material for gas turbine engine blades. In order to protect this ceramic component against the oxidation and volatilization in hot steam environments, environmental barrier coating should be utilized. The composite of SiC/Yb2Si2O7–Yb2SiO5 with self-healing ability is a candidate for the top layer of this coating. In this study, the crack-healing behavior of SiC/Yb2Si2O7–Yb2SiO5 nanocomposites is investigated by pre-cracking followed by annealing in oxidizing environments. Comparing to previous studies, the healing time and healing temperature can be reduced to 15 min and 800 °C by increasing the volume fraction of SiC to 20 %. In addition, nanocomposites with both self-healing ability and superior strength were created in this research by combining two types of SiC filler (whiskers and nanoparticulates). The self-healing mechanism in these composites is the SiC oxidation and silicate transformation associated with their volume expansion, which is evidenced by X-ray diffraction and scanning electron microscope. According to the results, the best volume ratio between whisker and nanoparticulate is determined as 1/3.