• 한국분말재료학회지
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• 제1권2호
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• pp.159-166
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• 1994

The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.

• 대한기계학회논문집A
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• 제21권1호
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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.

• 대한기계학회논문집A
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• 제24권3호
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• pp.735-742
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• 2000

Densification behaviors of mixed metal powder under high temperature were investigated. Experimental data of mixed copper and tool steel powder with various volume fractions of Cu powder were obtained under hot isostatic pressing and hot pressing. By mixing the creep potentials of McMeeking and co-workers and of Abouaf and co-workers originally for pure powder, the mixed creep potentials with various volume fractions of Cu powder were employed in the constitutive models. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data for densification of mixed powder under hot isostatic pressing and hot pressing. Finite element calculations by using the creep potentials of Abouaf and co-workers agreed reasonably well with experimental data, however, those by McMeeking and co-workers underestimate experimental data as observed in the case of pure metal powders.

• 한국분말재료학회지
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• 제12권4호
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• pp.255-260
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• 2005

Direct solid state synthesis by hot pressing has been applied in order to produce high efficiency $Zn_4Sb_3$ bulk specimens. Single phase $Zn_4Sb_3$ with 98.5% of theoretical density was successfully produced by direct hot pressing of elemental powders containing 1.2 at.% excess Zn. Thermoelectric properties as a function of temperature were investigated from room temperature to 600 K and compared with results of other studies. Transport properties at room temperature were also evaluated. Thermoelectric properties of single phase $Zn_4Sb_3$ materials produced by direct synthesis were measured and are comparable to the published data. Direct solid state synthesis by hot pressing provides a promising processing route in this material.

• 한국가구학회지
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• 제20권5호
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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.

• 한국세라믹학회지
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• 제19권2호
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• pp.152-156
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• 1982

The behavior of magnesite during hot pressing is studied from 80$0^{\circ}C$ to 110$0^{\circ}C$ by Knoop hardness test, X-ray diffraction and electron microscopy. The growth of magnesia crystallite in magnesite is observed at 110$0^{\circ}C$ and crystallite size is about 2 microns. It is also observed that hot pressing showes enhanced sinterability comparing to ordinary pressure-less sintering. The magnesia body with 95 per cent of theoretical density is obtained by hot pressing at relatively low temperature such as 110$0^{\circ}C$.

• 한국주조공학회지
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• 제13권6호
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• pp.547-554
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• 1993

Aluminum alloy matrix composites reinforced with various amounts of $Al_2O_3$ short fibers have been produced by rheo-compocasting accompanied by hot pressing. When composites reinforced with fibers are produced by rheo-compocasting, S-L process is the most effective method for homogeneous dispersion of fibers. A sound composites with the improved orientation(3 dimension${\rightarrow}$2 dimension) of the fibers and increased volume fraction of them have been fabricated through the hot pressing of the casted composites. Fibers are broken down when rheo-compocasting, hot pressing, and $T_6$ treating. Among them fibers are broken down most heavily in the hot pressing. And even in the case of the composite reinforced with 30 vol% fibers, which showed the hardest fiber break down, aspect ratio(11.6) is higher than critical aspect ratio(10.7). The fiber strengthening effect in the composites has showed upto 573K. As the test temperature increases to the range of 573K, the effect has been higher. The fracture of composites is controlled by fiber from room temperature to 473K, but the fracture of composites is controlled by interface between fiber and matrix alloy above 473K.

• 한국재료학회지
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• 제15권7호
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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 $Zn_4Sb_3$.ٓ

• Journal of the Korean Wood Science and Technology
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• 제31권2호
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• pp.77-83
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• 2003

본 연구에서는 대나무 Zephyr 보드에 있어서 열압조건이 보드의 성능에 미치는 영향을 조사하기 위하여 다양한 열압시간과 열압온도를 적용하여 보드(목표밀도 0.7 g/cm³, 400×400×12 mm)를 제조하고 그 기본적인 물성을 비교, 검토해 보았다. 제조된 보드는 KS F 3104와 KS F 3113에 준하여 성능평가를 하였으며 그 결과는 다음과 같다. 보드의 상태 휨강도는 열압조건에 관계없이 전반적으로 상당히 높은 값을 나타내었으며 그 중 span에 대한 평행 방향에 있어서는 열판온도 160℃에서 12분 동안 열압하여 제조한 보드가 가장 높은 강도를 보였다. 보드의 박리강도 시험에서는 모든 열압시간에서 열압온도가 높을수록 상대적으로 더 높은 값을 나타내었으며, 그 결과 200℃에서 압체된 보드가 가장 높은 강도를 보였다. 보드의 습윤 휨강도 시험에서는 총 열압시간 12분과 10분일 때 각각 160℃와 180℃의 온도에서 제조된 보드가 상대적으로 높은 강도를 나타내었다. 더욱이, 200℃에서 8분 동안 열압하여 제조한 보드의 경우 상태 휨강도에 거의 육박하는 가장 높은 습윤 휨강도를 보였다. 두께 팽창율 시험에서는 모든 보드에서 전반적으로 6% 미만의 낮은 값을 나타내어 높은 치수안정성을 가지는 것을 알 수 있었다.

• 한국세라믹학회지
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• 제29권11호
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• pp.855-862
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• 1992

Thermoelectric power, electrical conductivity and Hall effect were measured, as functions of temperature in the range of 100 to 600 K, on polycrystalline Bi4/3Sb2/3Te3 which had been prepared via uniaxial hot-pressing at different temperatures in the range of 373 K to 773 K, aiming at searching a profitable processing route to a polycrystalline thermoelectric material, a promising, viable alternative to a single crystalline one. It was found that, with increasing temperature of pressing under a fixed pressure, the material, normally a p-type prior to being hot-pressed, underwent a transition to n-type. This transition was confirmed to be due to plastic deformation during hot-pressing and interpreted as being attributed to the change of the major ionic defect BiTe' into TeBi˙at temperature high enough for structure elements mobility. Thermoelectric figure-of-merit of the hot-pressed material was discussed in connection with the p-n transition in addition to microstructure.