• Title/Summary/Keyword: Growth mechanism

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Fatigue Crack Growth Behavior of Non-Magnetic Steel with Large Grain Size (조대결정 비자성강의 피로균열진전특성)

  • 남정학;최성대;이종형;정선환
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.807-810
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    • 2001

  • Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Crystal grain size of the material is about 1000$\mu\textrm{m}$. For this material, the fatigue crack growth mechanism of high manganese steel was clarified from results such as observation of crack growth path and fracture surface. $\Delta$$K_{th}$ is about 8MPa$\surd$m which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low $\Delta$K regsion. The reason of this behavior is crack closure due to fracture surface roughness.

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Growth of Nanosized Pyrolytic Carbon Whisker by Catalytic Pyrolysis of Methane (저온에서 methane의 촉매적 열분해시 nanosized pyrolytic carbon whisker성장의 발견)

  • H. S. Rhee;Park, Y. T.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.04a
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    • pp.173-175
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    • 2003

  • At the low temperature of $950^{\circ}C$ the $\mu\textrm{m}$-sized whisker growth during the catalytic CVD of pyrolytic carbon from methane with $H_2$- and Ar-gas on quartz substrate with NiO powder was found in this work. In the preliminary study it was observed from pure methane pyrolysis without catalyst at the high temperature $1500~1700^{\circ}C$. If the growth whisker should be stopped at initial stage, about 20 min. of the methane pyrolysis, it would be nanosized whisker growth. The screw growth mechanism and unique mechanical properties of whisker for composites were also recognized. If the pyrolysis would be continued, we could found also spiral growth of whistlers with diameter of about 1, 5 mm. The large length of whisker was about 10 cm in 20 minute.

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Mechanism of Piezoelectricity for Langasite Based on the Framework Crystal Structure

  • Ohsato, Hitoshi;Iwataki, Tsuyoshi;Morikoshi, Hiroki
    • Transactions on Electrical and Electronic Materials
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    • v.13 no.2
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    • pp.51-59
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    • 2012

  • Piezoelectric langasite crystals have superior properties such as high temperature performance and high quality Q and can be applied in combustion pressure sensors and surface acoustic wave (SAW) filters. Crystal growth, crystal structure and properties of langasite group are reviewed, and the mechanism of piezoelectricity of langasite is presented based on the crystal structure and deformation under high pressure. Finally, for the discovery of new piezoelectric materials, this paper presents the role of the framework, and recommends the search of framework crystal structure, because the characteristic of the mechanism exists on the framework of the crystal structure.

  • https://doi.org/10.4313/TEEM.2012.13.2.51 인용 PDF KSCI