• Title/Summary/Keyword: hot-pressing

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Thermoelectric Properties of the (Pb$_{1-x}$Sn/$_{x}$)Te Sintered by AC Applied Hot Pressing (AC 통전식 Hot Press 법에 의해 제조된 (Pb$_{1-x}$Sn/$_{x}$)Te 열전반도체의 물성)

  • 신병철;황창원;오수기;최승철;백동규
    • Journal of the Microelectronics and Packaging Society
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    • v.7 no.4
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    • pp.1-5
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    • 2000
  • Properties of AC applied hot pressed ($Pb_{1-x}Sn_{x}$) Te thermoelectrics were investigated. Mechanical alloying process used to produce alloyed powder to reduce the inhomogeneity and to avoid vaporization of constituents. It showed an increase in the mechanical alloying time with increasing of Sn contents in ($Pb_{1-x}Sn_{x}$)Te. ($Pb_{1-x}Sn_{x}$)Te were sintered at 873 to 923K for 1-4 minutes, under 150 kgf/$\textrm{cm}^2$ by AC applied hot pressng method. The short sintering time of AC applied hot pressing process could reduce the vaporization of Te. The density of ($Pb_{1-x}Sn_{x}$) Te was more dependent on the sintering temperature than the sintering time. The p-n transition was observed at x=0.1 but only p type conduction behavior was observed at more than 20 mol% of Sn compositions. The maximum value of Seebeck coefficient is 250 $\mu$V/K for x=0.2 at 500K. As the amount of Sn increases, the peak value of Seebeck coefficient drops and shifts to higher temperature and the peak value of electrical conductivity decreased with increasing temperature.

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Fabrication and Tensile Properties of Alloy 617 base ODS Alloy (Alloy 617계 산화물 분산강화(ODS) 합금의 제조와 인장특성)

  • Min, Hyoung-Kee;Kang, Suk-Hoon;Kim, Tae-Kyu;Han, Chang-Hee;Kim, Do-Hyang;Jang, Jin-Sung
    • Journal of Powder Materials
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    • v.18 no.6
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    • pp.482-487
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    • 2011
  • Alloy 617, Ni-22Cr-12Co-9Mo base oxide dispersion strengthened alloy was fabricated by using mechanical alloying, hot isostatic pressing and hot rolling. Uniaxial tensile tests were performed at room temperature and at $700^{\circ}C$. Compared with the conventional Alloy 617, ODS alloy showed much higher yield strength and tensile strength, but lower elongation. Fracture surfaces of the tensile tested specimens were investigated in order to find out the mechanism of fracture mode at each test temperature. Grain adjustment during tensile deformation was analyzed by electron backscattered diffraction mapping, inverse pole figures and TEM observation.

Fabrication and Properties of Reactively Hot Pressed HfB2-HfC Ultra-High Temperature Ceramics

  • Lee, Seung-Jun;Seong, Young-Hoon;Baek, Seung-Su;Kang, Eul-Son;Kim, Do-Kyung
    • Journal of the Korean Ceramic Society
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    • v.47 no.6
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    • pp.534-539
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    • 2010
  • $HfB_2$-HfC composites were prepared by reactive hot pressing using Hf and $B_4C$ at temperatures of 1800 and $1900^{\circ}C$ for 60 min under 32 MPa in an Ar atmosphere. The reaction sequences of the $HfB_2$-HfC composite were studied through series of pressureless heat treatments ranging from 800 to $1600^{\circ}C$. The effect of size reduction of the starting powders on densification was investigated by vibration milling. Fully dense $HfB_2$-HfC composites were obtained by size reduction of the starting powders via vibration milling. The oxidation behaviour of the $HfB_2$-HfC composites at $1500^{\circ}C$ in air showed formation of a non-protective $HfO_2$ scale with linear mass gain. Examination of the mechanical properties showed that particle size reduction via vibration milling also led to improved flexural strength, hardness and fracture toughness.

Fabrication and Characterization of TiNi Shape Memory Alloy Fiber Reinforced 6061 Aluminum Matrix Composite by Using Hot Press (핫프레스법에 의한 TiNi/Al6061 형상기억복합재료의 제조 및 기계적 특성에 관한 연구)

  • Park, Dong-Sung;Lee, Jun-Hee;Lee, Guy-Chang;Park, Young-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.7
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    • pp.1223-1231
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    • 2002
  • Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate microstructures and mechanical properties. The analysis of SEM and EDS showed that the composites have shown good interface bonding. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of prestrain, and it showed that the yield stress at 363K was higher than that of the room temperature. Especially, the yield stress of this composite increases with increasing the amount of prestrain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. Microstructural observation has revealed that interfacial reactions occur between the matrix and fiber, creating two intermetallic layers.

Mechanical and Electrical Properties of Hot-Pressed Silicon Carbide-Titanium Carbide Composites (고온가압소결한 SiC-TiC 복합체의 기계적, 전기적 특성)

  • 박용갑
    • Journal of the Korean Ceramic Society
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    • v.32 no.10
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    • pp.1194-1202
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    • 1995
  • The influences of TiC additions to the α-SiC on microstructural, mechanical, and electrical properties were investigated. Electrical discharge machinability of SiC-TiC composites was also studied. Samples were prepared by adding 30, 45, 60 wt.% TiC particles as a second phase to a SiC matrix. Sintering of SiC-TiC composites was done by hot pressing under a vacuum atmospehre from 1000 to 2000℃ with a pressure of 32 MPa and held for 90 minutes at 2000℃. Samples obtained by hot pressing were fully dense with the relative densities over 99% except 60wt.% TiC samples. Flexural strength and fracture toughness of the samples were increased with the TiC content. In case of SiC samples containing 45 wt.% TiC, the fracture toughness showed 90% increase compared to that of monolithic SiC sample. The crack propagation and crack deflection were observed with a SEM for etched samples after Vicker's indentation. The electrical resistivities of SiC-TiC composites were measured utilizing the four-point probe. The electrical dischage machining of composites was also conducted to evaluate the machinability.

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Performance of Fuel Cell with PEMFC Fabricated under Different Pressure (고분자 전해질 연료전지 성능에 미치는 MEA 가압제조 공정 조건의 영향)

  • Lee, Ki-Seong;Sim, Sooman;Kim, Dongmin
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.1
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    • pp.70-75
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    • 2013
  • It has fabricated membrane electrode assemblies (MEA) for proton exchange membrane fuel cell by hot-pressing method. The hot-pressing was used for the fabrication of MEA which is composed of commercial platinum electrode on carbon paper. The performance of MEA was studied with different fabrication conditions of temperature, pressure and torque. As the temperature increased, the performance of MEA was increased. and started to decrease l after arrived at the maximum performance of MEA. This is related with good contact between electrode and polymer electrolyte membrane at high temperature and microstructural change at much higher temperature. Similarly, as the pressure increased, the performance of the MEA increased up to highest values and start to decrease. According to the our results, the maximal performance of the MEA was at the temperature of $140^{\circ}C$ and the pressure of $1.5{\times}10^3$ kPa. The optimal torque to assemble the single stack was 3.2 N m.

Tribological Properties of Hot Pressed SiC/$Si_3$$N_4$/SiCw Composites (가압소결 SiC/$Si_3$$N_4$/SiCw 복합체의 마찰마모특성)

  • Baik, Yong-Hyuck;Choi, Woong;Kang, Seon-Myung;Park, Yong-Kap
    • Journal of the Korean Ceramic Society
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    • v.37 no.11
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    • pp.1039-1043
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    • 2000
  • $\alpha$-Si$_3$N$_4$가 20vol% 혼합된 SiC/Si$_3$N$_4$혼합물에서 $\alpha$-SiC의 일부를 SiC whisker로 치환하여 첨가한 후 180$0^{\circ}C$, 25MPa의 압력으로 hot pressing하여 SiC/Si$_3$N$_4$/SiCw 복합체를 제조하였다. SiC whisker의 첨가 함량이 증가할수록 상대밀도, 꺽임강도, 마모 저항성은 감소되었으나, 파괴인성은 크게 향상되었다. $\alpha$-SiC의 일부를 SiC whisker로의 치환은 치밀화를 억제하였으나 파괴인성의 증가는 마모 저항성을 향상시키지 않았다.

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