• 제목/요약/키워드: phase change materials

검색결과 827건 처리시간 0.031초

Pd 박막의 전기저항-수소농도 이력현상 (Hysteresis Behavior in Electric Resistance-hydrogen Concentration of Pd Thin Films)

  • 이은송이;이준민;전계진;이우영
    • 대한금속재료학회지
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    • 제47권6호
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    • pp.372-377
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    • 2009
  • We report on hysteresis behavior in the electrical resistance-hydrogen concentration of Pd thin films. The variation of the electrical resistance has been investigated during the process of absorption and desorption of hydrogen gas ($H_{2}$) as a function of thickness of Pd thin films. The hysteresis behavior in the electrical resistance with $H_{2}$ concentration was found for Pd thin films and consists of $\alpha$ phase, ${\alpha}+{\beta}$ phase, and $\beta$ phase regions. The sensitivity of Pd thin films with $H_{2}$ concentration was found to follow Sieverts' law in the $\alpha$ phase region. However, the sensitivity was observed to increase abruptly with $H_{2}$ concentration in the ${\alpha}+{\beta}$ phase co-exist region. This is because Pd-H interaction is stronger in the $\beta$ phase than in the $\alpha$ phase and needs a higher concentration gradient as a driving force to desorb. The formation of the $\beta$ phase also was observed to cause the structural change because of the lattice expansion during absorption. The hysteresis height and the trace of structural change were affected by the thickness of the Pd film. As the film becomes thinner, the hysteresis height becomes lower and the amount of delamination on the surface becomes smaller. For films thinner than 20 nm in thickness, the delamination was not found but electrical resistance hysteresis was still observed.

파라핀 기반 상변화 물질을 이용한 태양광 반사 페인트 개발에 관한 연구 (Paraffin-Based Phase Change Materials for Solar Reflective Paints Applications)

  • 잔낫;소우멘 만달;이한승
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2023년도 가을학술발표대회논문집
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    • pp.67-68
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    • 2023
  • This paper reports on the synthesis of paraffin-based phase change materials (PCMs) designed for use in solar reflective paint (SRP) as a thermal energy storage (TES) medium. These PCMs are prepared using the sol-gel process and are encapsulated in silica. The focus of this research is to evaluate the suitability of these synthesized PCMs for efficient thermal energy storage within SRP applications. The obtained PCMs have nanometric dimensions, which make them well-suited for integration into paint formulations. The study also includes a thorough analysis of the chemical, thermal, and structural stabilities of these materials, confirming their applicability in solar reflective paint.

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PCM을 활용한 가변형 몰드 제작 프로세스 (Flexible Mold Production Process for Using the PCM)

  • 김태구;이동훈;김선국
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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    • pp.272-273
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    • 2014
  • Existing the free-form concrete segments (FCS) mold is produced by state of solid such as steel, wood, Styrofoam that can not be recycled. Using FCS mold result in delay on schedule and decrease of productivity because it consists of irregular curved variety and it requires more time than fixed mold. Thus, FCS mold should be developed which can reduce the costs and also it can be used as semipermanent. The aim of this study is to suggest of flexible mold production process for using the phase change materials(PCM). PCM is maintain that its solid state at low temperature but it changes phase to liquid state by heating. PCM is suitable material for flexible mold due to change of phase in relatively high temperature compare to other phase change materials such as water. Flexible mold is possible that reuse semi-permanently made by PCM. Thus, this study is proposed the process of flexible mold production for using the PCM. The study results will be used as the basic theory for studies on production and installation of FCS.

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Hydroxyapatite 분위기 소결을 통한 지르코니아 표면 경도 강화 (Enhancement of Surface Hardness of Zirconia Ceramics by Hydroxyapatite Powder Bed Sintering)

  • 최민근;임지호;공규환;정대용;이원주;이용호;공영민
    • 한국재료학회지
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    • 제24권12호
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    • pp.677-681
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    • 2014
  • To increase the mechanical property of zirconia, we have investigated the phase change and the resulting hardness of zirconia ceramics by hydroxyapatite (HA) powder bed sintering. It was observed using X-ray diffraction that the cubic zirconia phase, which has a higher hardness value than that of the tetragonal phase, was obtained at the surface of 3 mol% $Y_2O_3$ doped tetragonal zirconia polycrystal (3Y-TZP) ceramics during the sintering process; in our experimental conditions, the phase change at the surface increased as the sintering time increased. We believe that the observed crystalline phase change originated from the decomposition of HA and the diffusion of CaO, as follows. CaO, which was derived from the decomposition of HA at high temperature ($1400^{\circ}C$), diffused into the surface of 3Y-TZP and acted as a stabilizer. As a result, the Vickers hardness value of the treated specimens was higher than that of the non-treated specimen due to the formation of the cubic phase on the surface of 3Y-TZP.

PCM의 잠열측정을 위한 T-history법에 대한 고찰 (Consideration on the T-history Method for Measuring Heat of Fusion of Phase Change Materials)

  • 박창현;최주환;홍희기
    • 설비공학논문집
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    • 제13권12호
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    • pp.1223-1229
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    • 2001
  • Though conventional calorimetry methods such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) are used generally in measuring heat of fusion, T-history method has the advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermal properties of inhomogeneous phase change materials (PCMs) in sealed tubes. However, random criteria (a degree of supercooling) used in selecting the range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

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Improvement of the T-history Method to Measure Heat of Fusion for Phase Change Materials

  • Hong, Hi-Ki;Park, Chang-Hyun;Choi, Ju-Hwan;Peek, Jong-Hyeon
    • International Journal of Air-Conditioning and Refrigeration
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    • 제11권1호
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    • pp.32-39
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    • 2003
  • Though conventional calorimetry methods such as differential scanning calorimetry and differential thermal analysis are used generally in measuring heat of fusion, T-history method has advantages of a simple experimental apparatus and no requirements of sampling process, which is particularly useful for measuring thermophyical properties of in-homogeneous phase change materials in sealed tubes. However, the degree of supercooling used in selecting a range of latent heat release and neglecting sensible heat during the phase change process can cause significant errors in determining the heat of fusion. In the present study, it was shown that a 40% discrepancy exists between the original T-history and the present methods when analyzing the same experimental data. As a result, a reasonable modification to the original T-history method is proposed.

위상변화를 이용한 표면탄성파 가스센서 (Surface acoustic wave gas sensors by utilizing the phase change)

  • 김진상;정용철;강종윤;김달영;남창우;윤석진
    • 센서학회지
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    • 제14권3호
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    • pp.186-190
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    • 2005
  • This paper describes the development of a surface acoustic wave gas sensor that is designed to detect volatile gas by monitering phase change of output signal as a function of time. The sensor consists of SAW oscillators with a center frequency of 100 MHz fabricated on $128^{\circ}$ Y-Z $LiNbO_{3}$ substrates. Experimental results, which show the phase change of output signal under the absorption of volatile gas onto sensors, are presented. The proposed sensor has the properties of high sensitivity compare to the conventional SAW gas sensor and chemical selectivity. Thus, it is thought these results are applicable for use in sensor array of an high performance electronic nose system.

Rapid Manufacturing of 3D Micro-products using UV Laser Ablation and Phase-change Filling

  • Shin Bo-Sung;Kim Jae-Gu;Chang Won-Suk;Whang Kyung-Hyun
    • International Journal of Precision Engineering and Manufacturing
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    • 제7권3호
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    • pp.56-59
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    • 2006
  • UV laser micromachining is generally used to create microstructures for micro-products through a sequence of lithography-based photo-patterning steps. However, the micromachining process is not suitable for rapid realization of complex 3D micro-products because it depends on worker experience. In addition, the cost and time required to make many masks are excessive. In this paper, a more effective and rapid micro-manufacturing process, which was developed based on laser micromachining, is proposed for fabricating micro-products directly using UV laser ablation and phase-change filling. The filling process is useful for holding the micro-products during the ablation step. The proposed rapid micro-manufacturing process was demonstrated experimentally by fabricating 3D micro-products from functional UV-sensitive polymers using 3D CAD data.

수중 무인 이동체 적용을 위한 상변화물질 기반의 전기 에너지 생성에 대한 실험적 연구 (An Experimental Study on Electrical Energy Generation Based on Phase Change Materials for Application of Underwater Unmanned Vehicles)

  • 하연철
    • 융합신호처리학회논문지
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    • 제23권4호
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    • pp.228-233
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    • 2022
  • 본 연구는 수중 무인 이동체의 장기 운용을 위한 전기 에너지의 생성을 위하여 상변화물질(PCM)을 활용하는 방안에 대한 실험적 연구이다. 상변화물질이 온도에 따라 고체와 액체의 상태로 변하면서 발생하는 부피의 변화가 한정된 공간에서 고압으로 변환되어 이를 통해 유체의 흐름을 만들어 발전하는 방식이다. 상변화물질로 해양의 온도를 고려하여 폴리에틸렌글리콜(Polyethylene glycol)을 사용하였으며, 고체상태인 저온(1℃~2℃)과 액체 상태인 고온(21℃~25℃)에서 부피 변화를 압력으로 변환 시켜주는 전기 에너지 생성 장치를 제작하여 전기 에너지 생성 실험을 수행하였다. 실험 결과, 상(Phase)변화에 따른 압력 변화는 1시간에서 2시간 사이에 급격히 발생하였으며, 4시간 이후에는 약 24MPa 정도의 압력을 유지하였다. 이를 통해 상변화물질과 온도 차를 이용하여 수중 무인 이동체의 전원으로 활용할 수 있음을 확인하였고, 이를 적용하기 위해서는 좀 더 개선된 설계가 이루어져야 함을 알 수 있었다.

형태안정성 PCM: 잠열저장을 위한 Polypropylene과 n-Eicosane으로 구성된 고화젤의 제조 및 특성 (Shape-Stabilized Phase Change Materials: Preparation and Properties of Frozen Gels from Polypropylene and n-Eicosane for Latent Heat Storage)

  • 손태원;임학상;김태훈;고재왕
    • 폴리머
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    • 제34권3호
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    • pp.261-268
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    • 2010
  • 본 연구에서는 상전이 온도가 36 $^{\circ}C$인 n-eicosnae을 열가소성 폴리올레핀 고분자인 폴리프로필렌과 블렌드하였으며, 또한 최근의 형태안정성 PCM(SSPCM)의 연구검토를 통하여 폴리프로필렌과 n-eicosnae의 특성과 잠열저장체로서의 적용 가능성을 확인하였다. 상전이 온도가 36 $^{\circ}C$인 n-eicosane과 폴리프로필렌을 멜팅방법과 흡수방법을 이용하여 시료를 제조하였다. 제조된 형태안정성 PCM(SSPCM)을 DSC, WAXD, FTIR spectroscopy, ARES로 분석결과 형태안정성, 열용량의 향상을 확인하였다.