• Title/Summary/Keyword: Hot-pressing process

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Investigation on the mechanism of heat transfer in hot-pressing process of fiberboard manufacturing for laminate flooring (강화마루용 섬유판 열압공정에서의 열전달 원리에 대한 고찰)

  • Kim, Su-Min
    • Journal of the Korea Furniture Society
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    • v.20 no.5
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    • pp.490-503
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    • 2009
  • The objective of this work was to investigate the mechanism of heat transfer in hot-pressing process for MDF manufacturing by reference study. Firstly, general heat transfer theory was studied. The numerical analysis of heat transfer in hot-pressing process was studied on temperature profile, moisture profile, physical properties between moisture and board. The mechanism of heat and moisture transfer inside of board was analyzed by conduction, convection, radiation and diffusion of bound water in wood cell walls. Especially, the change of core temperature as hot press time was important factor to setup hot-pressing schedule in MDF manufacturing.

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Near-net-shape forming of ceramic powder under hot pressing and hot isostatic pressing (가압소결과 열간 등가압소결에 의한 세라믹 분말의 정형 성형)

  • Kwon, Yeong-Sam;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.1
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    • pp.73-82
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    • 1997
  • High temperature densification behaviors of alumina powder compacts were investigated under hot pressing and hot isostatic pressing. An alumina part of valve-head shape was fabricated under hot pressing and its forming process was simulated by finite element calculation. an alumina powder compact encapsulated by a stainless steel container was also densified under hot isostatic pressing. Inhomogeneous deformations during hot isostatic pressing due to the canning effect were observed experimentally and predicted by finite element analysis.

A Performance characteristics of Pt/C Electrode prepared by Hot Pressing Method (Hot Pressing법에 의해 제조된 Pt/C 전극의 성능특성)

  • 김진수;서동우;설용건;이태희
    • Journal of Energy Engineering
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    • v.1 no.1
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    • pp.58-65
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    • 1992
  • Pt loaded porous carbon Pt/C electrode was prepared by hot pressing process to enhance the electrode performance in PAFC (phosphoric acid fuel cell). By changing the hot pressing conditions and PTFE contents, Pt/C electrodes were prepared and the electrochemical characteristics of oxygen reduction and unit-cell performance were evaluated. The optimum condition of hot press to make electrode is 360$^{\circ}C$ and 10 kg/$\textrm{cm}^2$. Maximum performance was obtained at 30 wt% PTFE content in the catalyst layer with 80% utilization of platinum clusters. Unit-cell performance of hot pressed Pt/C electrode was 200 mA/$\textrm{cm}^2$ at 700 ㎷ and stable performance was maintained more than 200 hr.

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Sintering Characterization of Alumina Powders by Hot Pressing after Cold Cyclic Compaction -Densification, Grain-Growth and Fracture Toughness- (상온 반복압축 후 가압소결에 의한 알루미나 분말의 소결특성 -치밀화와 결정립 성장 및 파괴인성-)

  • Son, G.S.;Suh, J.;Baik, S.K.;Kim, K.T.
    • Journal of the Korean Ceramic Society
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    • v.30 no.1
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    • pp.62-68
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    • 1993
  • Densification of alumina powder, grain size and fracture toughness of sintered body by hot pressing after cold compaction were investigated and compared to traditional hot pressing process (without cold cyclic compaction). To achieve a higher densification and to reduce the hot pressing time, hot pressing after cold cyclic compaction was more efficient compared to traditional hot pressing. This phenomenon resulted from the increment of packing densityby the acceleration fo rearrangement of powders under cold cyclic compaction. The grain size of sintered body was only dependent on relative density, and densification during hot pressing was governed by thelattice diffusion. Comprisons of grain size, densification mechanism and fracture toughness resulted from hot pressing after/without cold cyclic compaction showed that a low cyclic pressure may not effect on the fragmentation of alumina powders.

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Numerical Simulation for Pressing Process of Hot glass (고온 유리의 프레스 성형 공정 시뮬레이션)

  • Ji Suk Man;Choi Joo Ho;Kim Jun Bum;Ha Duk Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.5 s.170
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    • pp.205-213
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    • 2005
  • This paper addresses a method for numerical simulation in the pressing process of hot glass. Updated Lagrangian finite element formulations are employed for the flow and energy equations to accommodate moving meshes. The model is assumed axi-symmetric and creep flow is assumed due to the high viscosity. Commercial software ANSYS is used to solve the coupled flow and energy equations. Moving contact points as well as free surface during the pressing are effectively calculated and updated by utilizing API functions of CAD software Unigraphics. The mesh distortion problem near the wall is overcome by automatic remeshing, and the temperatures of the new mesh are conveniently interpolated by using a unique function of ANSYS. The developed model is applied to the pressing process of TV glasses. In conclusion, the presented method shows that the pressing process accompanying moving boundary can be simulated by effectively combining general purpose software without resorting to special dedicated codes.

The effect of MEA fabrication procedure on PEMFC performance (고분자전해질 연료전지의 MEA 제조방법에 따른 성능비교)

  • Cho Yong-Hun;Cho Yoon-Hwan;Park In-Su;Choi Baeckbom;Jung Dae-Sik;Sung Yung-Eun
    • 한국신재생에너지학회:학술대회논문집
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    • 2005.06a
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    • pp.291-295
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    • 2005
  • The PEMFC behavior is quite complex and is influenced by several factors, including composition and structure of electrodes and membrane type. Fabrication of MFA is important factor for proton exchange membrane fuel cell. MFA of PEMFC with hot pressing and direct coating method were prepared, and performances were evaluated and compared each other. The effect of MEA preparation methods, hot pressing methods and direct coating methods, on the cell performance was analyzed by impedance spectroscopy and SEM. The performance of PEMFC wi th direct coat ing method was better than wi th hot pressing method because membrane internal resistance and membrane-:-interfacial resistance were reduced by elimination of hot pressing process in MEA fabrication. In addition the micro structure of MEA with direct coating method reveals uniform interface between membrane and catalyst layer.

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Fabrication and Properties Analysis of MEA for PEMFC (고분자전해질 연료전지용 MEA 제조 및 특성평가)

  • Cho Y.H.;Cho Y.H.;Park I.S.;Sung Y.E.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.230-234
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    • 2005
  • Fabrication of MEA is important factor for proton exchange membrane fuel cell (PEMFC). MEA of PEMFC with hot pressing and direct coating method were prepared, and performances were evaluated and compared each other. The effect of MEA preparation methods, hot pressing methods and direct coating methods, on the cell performance was analyzed by impedance spectroscopy and SEM. The performance of PEMFC with direct coating method was better than with hot pressing method because membrane internal resistance and membrane-interfacial resistance were reduced by elimination of hot pressing process in MEA fabrication. In addition the micro structure of MEA with direct coating method reveals uniform interface between membrane and catalyst layer.

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Hot Pressing after Cold Cyclic Compaction of Alumina Powder Matrix Mixtures -Effects of Cold Cyclic Compaction- (알루미나 분말 기지혼합체의 상온 반복압축 후 가압소결 -상온 반복압축 효과-)

  • Son, G.S.;Suh, J.;Park, B.H.;Kim, K.T.
    • Journal of the Korean Ceramic Society
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    • v.30 no.2
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    • pp.157-163
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    • 1993
  • Hot pressing after cold cyclic compaction of Al2O3 powder mixtures containing SiC whiskers or Al2O3 short fibers is studied with emphasis on the effects of cold cyclic compaction. The green density of the mixtures increases as the cycle number increases and the cyclic pressure becomes higher. The higher green density is also obtained by cold cyclic compaction with the lower pressrue than a single stroke cold compaction. To achieve a higher densification during hot pressing, cold cyclic compaction before hot pressing is more efficient compared to the conventional hot pressing process (without cold cyclic compaction). Moreover, a low cyclic pressure did not affect on toughening mechanism by whisker reinforcement.

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Synthesis of Zn4Sb3 by Solid State Reaction and Hot Pressing, and Their Thermoeletric Properties (고상 합성과 진공 압축성형에 의한 Zn4Sb3의 제조 및 열전특성)

  • Ur Soon-Chul
    • Korean Journal of Materials Research
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    • v.15 no.7
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    • pp.473-479
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    • 2005
  • Thermoelectric $Zn_4Sb_3$ alloys were synthesized by a conventional powder metallurgy process consisting of solid state reaction and hot pressing. Single phase $Zn_4Sb_3$ was successfully produced by the annealing of cold compact starting with the mixed elemental powders, and subsequent hot pressing yielded single phase bulk specimens without microcracks. Phase transformations in this alloy system during synthesis were investigated using XRD, SEM and EDS. Thermoelectric properties as a function of temperature were investigated from room temperature to 600 K and compared with results of analogue studies. Transport properties at room temperature were also evaluated. Thermoelectric properties of single phase $Zn_4Sb_3$ materials produced by this process are comparable to the published data. Synthesis by solid state reaction and hot pressing offers a potential processing route to produce a bulk $Zn_4Sb_3$