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Mullite와 Lithium Alumino Silicate(LAS)나노복합체 세라믹스의 구조와 열적특성
허석 ( S Heo ),전병세 ( B S Jun ) 경남대학교 신소재연구소 2013 신소재연구 Vol.25 No.-
LAS계 소지에서는 열팽창의 이방성 때문에 치밀한 구조를 얻기가 힘들다. 따라서 열팽창계수와 기계적 강도가 감소되어진다. 본 연구에는 LAS계 소지를 고온에서 기계적 강도가 우수하고 상대적으로 열팽창계수가 낮은 Mullite에 첨가 하여 LAS-Mullite 복합체 제조 방법과 LAS-Mullite 복합체의 물성을 문헌에서 조사하였다. 유리세라믹 제조 방법은 LAS/Mullite 나노 복합체를 제조 하는데 좋은 아이디어를 제공하였다. 개수 농도와 소결 방법의 개념은 나노 복합체를 위해 중요하게 기여 할 수 있다. Due to the anisotropy of thermal expansion of LAS system, it is hard to obtain a dense sintered body. Therefore, the thermal expansion coefficient and the mechanical strength were decreased. In this study, LAS system is taken as an additive in Mullite which has good mechanical properties in high temperature and comparatively low thermal expansion coefficient. The LAS-Mullite Composite fabrication methods and properties of LAS-Mullite composite are investigated by literature survey. Glass ceramic fabrication method may give the idea of preparing of LAS/Mullite Nano composite. It is expected that the concept of particle number concentration and sintering method must be employed for the nano composite.
A Fish Robot Driven by Piezoceramic Actuators and Miniaturized Power Supply
Sang Q. Nguyen(구옌쾅상),S. Heo(허석),Hoon C. Park(박훈철),Nam S. Goo(구남서),Taesam Kang(강태삼),Doyoung Byun(변도영) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In this paper, we have introduced a new prototype of fish robot driven by unimorph piezoceramic actuators. To improve the swimming performance of the fish robot in terms of tail beat angle, swimming speed, and thrust force, we used four Light-weight Piezo-Composite Actuators (LIPCAs). We also developed a new actuation mechanism consisting of links and gears. Performance tests of the present fish robot were conducted in the water at various tail-beat frequencies to measure tail-beat angle, swimming speed, and thrust force. The tail-beat angle was significantly improved compared to the previous one. The best tail-beat frequency was 1.4 ㎐ for the present fish robot. A miniaturized power supply was developed to excite the LIPCAs and installed inside fish robot body for free-swimming. The maximum free-swimming speed was 3.2 cm/s and maximum thrust force was 0.0048 N.