• Title/Summary/Keyword: 등방성 수축

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Observation of the Shrinkage Characteristics of the Machined Zirconia Abutment by the full sintering process (완전 소결에 의한 지르코니아 어뷰트먼트의 수축 등방성 평가)

  • Lee, Ho-Cheol;Park, Seong-Jun;Kim, Jae-Duk
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.6
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    • pp.729-734
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    • 2011
  • The full sintering process of zirconia has some extent of shrinkage and the custom abutment design should consider the pre-compensation volume of the shape. In this paper, we concentrated to reveal the asymmetric sintering characteristics. The circular profile of all six samples were measured using the three dimensional coordinate machine. After the full sintering process, the profiles were measured again. The roundness were compared to those of the original shapes and the percent of shrinkage were calculated. On the other hand, surface roughness was also investigated after the full sintering process. The final average surface roughness was improved by the sintering of the machined zirconia surface.

Evaluation of Characteristics of Anisotropic Deformation in Manufacturing of Large-scale Glass-ceramic Composite Sintered Body (대형 유리-세라믹 복합 매질 소결체 제조 시 비등방성 변형 특성 평가)

  • Kim, Kwang-Wook;Sohn, Sungjune;Kim, Jimin;Foster, Richard I.;Lee, Keunyoung
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.1
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    • pp.31-41
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    • 2020
  • We studied the anisotropic shrinkage and deformation characteristics of large size sintered bodies in the manufacturing of glass-ceramic composite wasteform. We used uranium-bearing waste, generated from the treatment of spent uranium catalyst. Sintered specimens were prepared in several forms, comprising a circular disk, and a quarter disk in several diameters of up to 40 cm. Regardless of form or size, the sintered bodies had high isotropic shrinkage when they were fabricated using green bodies prepared at 60 MPa. The average anisotropy rate and average shrinkage rate were 1.6%, and 37.4%, respectively. We confirmed that the glass-ceramic composite wasteform in a large scale disk-type for packing in a 200 L drum could be fabricated with a tolerable anisotropy shrinkage. This has resulted in a significant reduction in the volume of radioactive waste to be disposed of with highly stable wasteform.

Extended Unmixing-Mixing Scheme for Prediction of 3D Behavior of Porous Composites (다공성 복합재료의 삼차원 거동 예측을 위한 분리-혼합 기법의 확장)

  • Choi, Hoi Kil;Shin, Eui Sup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.2
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    • pp.91-97
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    • 2013
  • Pyrolysis and surface recession of charring composites are progressed primarily in the thickness direction. The unmixing-mixing scheme is applied to describe the in-plane and through-thickness behaviors of porous composites. The extended unmixing-mixing equations are based on transverse isotropy of unidirectionally fiber-reinforced composites. The strain components of gas pressure in pores, thermal expansion, and chemical shrinkage are included in the constitutive model. By analyzing micromechanical representative volume elements of porous composites, the validity of the derived equations are examined.

Micropatterning of Polyimide and Liquid Crystal Elastomer Bilayer for Smart Actuator (스마트 액추에이터를 위한 폴리이미드 및 액정 엘라스토머 이중층의 미세패터닝)

  • Yerin Sung;Hyun Seung Choi;Wonseong Song;Vanessa;Yuri Kim;Yeonhae Ryu;Youngjin Kim;Jaemin Im;Dae Seok Kim;Hyun Ho Choi
    • Journal of Adhesion and Interface
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    • v.25 no.1
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    • pp.169-274
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    • 2024
  • Recent attention has been drawn to materials that undergo reversible expansion and contraction in response to external stimuli, leading to morphological changes. These materials hold potential applications in various fields including soft robotics, sensors, and artificial muscles. In this study, a novel material capable of responding to high temperatures for protection or encapsulation is proposed. To achieve this, liquid crystal elastomer (LCE) with nematic-isotropic transition properties and polyimide (PI) with high mechanical strength and thermal stability were utilized. To utilize a solution process, a dope solution was synthesized and introduced into micro-printing techniques to develop a two-dimensional pattern of LCE/PI bilayer structures with sub-millimeter widths. The honeycomb-patterned LCE/PI bilayer mesh combined the mechanical strength of PI with the high-temperature contraction behavior of LCE, and selective printing of LCE facilitated deformation in desired directions at high temperatures. Consequently, the functionality of selectively and reversibly encapsulating specific high-temperature materials was achieved. This study suggests potential applications in various actuator fields where functionalities can be implemented across different temperature ranges without the need for electrical energy input, contingent upon molecular changes in LCE.