• Title/Summary/Keyword: Thermal phase transition

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Silicidation and Thermal Stability of the So/refreactory Metal Bilayer on the Doped Polycrystalline Si Substrate (Co/내열금속/다결정 Si 구조의 실리사이드화와 열적안정성)

  • 권영재;이종무
    • Journal of the Korean Ceramic Society
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    • v.36 no.6
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    • pp.604-610
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    • 1999
  • Silicide layer structures and morphology degradation of the surface and interface of the silicide layers for he Co/refractory metal bilayer sputter-deposited on the P-doped polycrystalline Si substrate and subjected to rapid thermal annealing were investigated and compared with those on the single Si substrate. The CoSi-CoSi2 phase transition temperature is lower an morphology degradation of the silcide layer occurs more severely for the Co/refractorymetal bilayer on the P-doped polycrystalline Si substrate than on the single Si substrate. Also the final layer structure and the morphology of the films after silicidation annealing was found to depend strongly upon the interlayer metal. The layer structure after silicidation annealing of Co/Hf/doped-poly Si is Co-Hf alloy/polycrystalline CoSi2/poly Si substrate while that of Co/Nb is polycrystalline CoSi2/NbSi2/polycrystalline CoSi2/poly Si.

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(An) experimental study on the development of lightweight concrete using the PCM (PCM 혼입 경량기포콘크리트 패널 개발을 위한 기초적 연구)

  • Lim, Myung Kwan;Enkhbold, Odontuya;Kim, Young Ho;Choi, Dong Uk
    • KIEAE Journal
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    • v.14 no.4
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    • pp.133-138
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    • 2014
  • The present study was carried out to assess the basic material properties and thermal behavior of light-weight foamed concrete panel mixed with PCM (Phase Changing Material). To do so, this study fabricated light-weight foamed concrete (1.0kg/m3) in pre-foaming method and mixed it with PCM micro capsule of 1-dodecanol and melamine to examine its physical and thermal properties. The results confirmed strength reinforcement effect by proper replacement ratio of fly-ash, which is an industrial by-product, and PCM. In addition, it found out that PCM-mixed light-weight foamed concrete had time delay and temperature reduction effect within the range of PCM phase transition according to the rise of outdoor temperature. It was also observed that the insulation performance of PCM-mixed light-weight foamed concrete was more dependent upon thickness than PCM replacement ratio.

Synthesis and Properties of Cholesteric Liquid Crystalline Polymers with Isosorbide Group (아이소소바이드기를 갖는 콜레스테릭 액정고분자의 합성 및 성질)

  • Gu, Su-Jin;Yoon, Doo-Soo;Bang, Moon-Soo
    • Applied Chemistry for Engineering
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    • v.28 no.2
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    • pp.230-236
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    • 2017
  • We synthesized liquid crystalline polymers containing isosorbide group as a cholesteric derivative and methylene group for controlling the transition temperature to the liquid crystal phase. Effects of the concentration of the isosorbide group and the position of the methylene group on the properties of the liquid crystalline polymer were investigated. Among all the synthesized polymers, polymers (MnHI-x) with a methylene group in the main chain showed higher melting transition temperature and thermal stability than those (SnBI-x) with a methylene group in the side chain. All the synthesized polymers showed an enantiotropic liquid crystal phase. The polymers having 10 mol% isosorbide as a cholesteric liquid crystal phase derivative showed nematic phase, and those having 20 mol% or more isosorbide showed a cholesteric or chiral smectic phase. Thus, we can conclude that the isosorbide group plays a role as a cholesteric liquid crystal phase derivative.

The Synthesis of Sodium Titanate by the Ion Exchange of H+/Na+ from Hydrous Titanium Dioxide and its Phase Transition (Hydrous Titanium Dioxide로부터 H+/Na+의 이온교환에 의한 티탄산나트륨의 합성 및 성전이)

  • Lee, Jin-Sik;Song, Yon-Ho;Lee, Chul-Tae
    • Applied Chemistry for Engineering
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    • v.9 no.4
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    • pp.585-590
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    • 1998
  • Fibrous $Na_xTi_nO_{2n+1}$ whisker was prepared by $H^+/Na^+$ ion-exchange on layered hydrous titanium dioxide ($H_2Ti_4O_9{\cdot}nH_2O$). The ion-exchange reaction was proceeded at 0.5~2.0 M NaOH solution. In the ion-exchange at 2.0 M NaOH solution, 73% of sodium was exchanged and the prepared $Na_xTi_nO_{2n+1}$ whisker was a fibrous crystal of about $10{\sim}20{\mu}m$ of length and about $0.7{\mu}m$ of diameter. The phase transition of the ion-exchange phases identified by the thermal analysis. The result showed that the $Na_xTi_nO_{2n+1}$ whisker was decomposed into $Na_2Ti_6O_{13}$ and $TiO_2$ in the temperature of $200{\sim}600^{\circ}C$.

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Study on Property Variations of $CoSi_2$ Electrode with Its Preparation Methods ($CoSi_2$ 전극 구조의 증착법에 따른 특성 변화 연구)

  • Nam, Hyoung-Gin
    • Journal of the Semiconductor & Display Technology
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    • v.6 no.4
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    • pp.5-9
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    • 2007
  • Phase transition and dopant redistribution during silicidation of $CoSi_2$ thin films were characterized depending on their preparation methods. Our results indicated that cleanness of the substrate surface played an important role in the formation of the final phase. This effect was found to be reduced by addition of W resulting in the formation of $CoSi_2$. However, even in this case, the formation of the final phase was achieved at the cost of extra thermal energy, which induced rough interface between the substrate and the silicide film. As for the dopant redistribution, the deposition sequence of Co and Si on SiGe was observed to induce significant differences in the dopant profiles. It was found that co-deposition of Co and Si resulted in the least redistribution of dopants thus maintaining the original dopant profile.

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Effect of Pb Content on the Phase Transformation of Sputter-Deposited PZT Thin Film During RTA (PZT 박막의 급속열처리시 Pb 함량이 상변태에 미치는 영향)

  • 주재현;길덕신;주승기
    • Journal of the Korean Ceramic Society
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    • v.30 no.10
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    • pp.803-810
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    • 1993
  • PbxZr0.4Ti0.6O3 thin films were prepared by reactive co-sputtering and annealed by RTA(Rapid Thermal Annealing) process. Effect of Pb content in PbxZr0.4Ti0.6O3 films on the phase transformation was intensively studied. It has been found out that depending on the Pb content as well as RTA temperature, crystal structure of PbxZr0.4Ti0.6O3 films change greatly. It turned out that transformation temperature for perovskite can be lowered and the width of transition temperature region was reduced by increasing Pb content in the film. And the lattice was expanded with increasing Pb content. With increasing RTA temperature, as-deposited phase was transformed into perovskite through three different transformation paths depending on Pb content. It was confirmed that activation energies for nucleation of perovskite structure are much larger than those of its growth.

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Properties and Synthesis of Porous Cordierite from Fly Ash (플라이 애쉬를 이용한 다공성 코디어라이트의 합성 및 특성)

  • Kim, Sung-Jin;Bang, Hee-Gon;Park, Sang-Yeup
    • Journal of the Korean Ceramic Society
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    • v.43 no.6 s.289
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    • pp.344-350
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    • 2006
  • Porous cordierite was synthesized by the mechano-chemical processing using fly ash. The phase evolution of cordierite was investigated as a function of processing variables such as milling time and sintering temperature. In this study, the phase transition path of cordierite from fly ash was followed by sapprine/spinel ${\to}$ mullite/spinel ${\to}{\alpha}$-cordierite. Porous cordierite fabricated after 32 h of milling time and sintering at $1150^{\circ}C$ showed relatively low thermal expansion coefficient ($2.5{\times}10^{-6}/^{\circ}C\;(25{\sim}1000^{\circ}C$)) and high porosity (75%).

Two-Phase Flow Characteristics in an Adiabatic Horizontal Tube (단열 수평관내 이상류의 유동특성)

  • Choi, B.H.
    • Journal of Power System Engineering
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    • v.8 no.1
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    • pp.36-40
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    • 2004
  • Two-phase loop systems using the latent heat capacity of their working fluids can meet the increasing power requirements and are well suited to thermal management systems of future large applications, due to its abilities to handle large heat loads and to provide them at uniform temperatures regardless of the changes in the heat loads. Therefore some experiments on the effect of the gas and liquid superficial velocities, $j_G,\;j_L$ on flow pattern transition, void fraction and frictional pressure loss were performed on a co-current air-water flow in an adiabatic horizontal tube. The flow patterns were depended on the superficial velocity of each phase. It snowed that the increasing $j_L$, resulted in a significant increase in the frictional pressure loss for all flow patterns, at a constant $j_G$. The experimental results were also evaluated with some of existing models and correlations.

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Metal-Organic Vapor Phase Epitaxy : A Review II. Process and charactristics (MOVPE 단결정층 성장법 II. MOVPE공정 및 특징)

  • 정원국
    • Journal of the Korean institute of surface engineering
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    • v.23 no.2
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    • pp.1-10
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    • 1990
  • Metal-Organic Vapor Phase Epitaxy (MOVPE) is an epitaxial process utilizaing ane or more of organometallice as reactnte to grow compound semicond semiconductror layers. MOVPE is basically a cold wall process in which reactants are delivered without reacting with each other to the heated substrate where reactants are thermally decomposed to from compound semiconductors through chemical reaction. Since reactants are delivered as gas phase and the formation of the single crystal compunds depends on the thermal decomposition of the reactants, details of MOVPE relies on the hydrodynamics and pyroltsis and chemical reation of reactants inside on reaction chamber. It has been demonstrated that MOVPE is capable of growing virtually all of the III-V, II-VI and IV-VI compound semiconductrs, fabricating ultrathin epilayers, for ming abrupt hetrointerfaces with monolayer transition width, and is suitable for multi-wafer operation yilding a high throghtput. Overiew of reactror componts and layer, characteristics, and status of MOVPE are discussed.

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Thermal Transient Analysis of Electric Initiator Used SUS 304 Bridgewire (SUS 304 발열선을 사용한 전기식 착화기의 열특성 분석)

  • Yoon Ki-Eun;Ryu Byung-Tae;Choi Hong-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.184-187
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    • 2005
  • Performing thermal transient test on electric initiator with SUS 304 bridgewire(diameter 2.3mil) and $Zr-KClO_4$ primary charge and analysing the test data using Fitted Wire Model shows that the thermal characteristic parameter related to primary charge is changed sharply around $300^{\circ}C$. It is determined that this phenomenon is due to endothermic reaction from phase transition of $KClO_4$, which is used as primary charge, and to physical change of thermal transient interface between bridgewire and primary charge. With this results, useful temperature range for the parameter obtained from thermal transient test can be suggested.

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