• Journal of Ceramic Processing Research
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• v.20 no.6
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• pp.582-588
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• 2019

FeVSb1-xTex (0.02 ≤ x ≤ 0.10) half-Heusler alloys were fabricated by mechanical alloying process and subsequent vacuum hot pressing. Near single half-Heusler phases are formed in vacuum hot pressed samples but a second phase of FeSb2 couldn't be avoided. After doping, the lattice thermal conductivity in the system was shown to decrease with increasing Te concentration and with increasing temperature. The lowest thermal conductivity was achieved for FeVSb0.94Te0.06 sample at about 657 K. This considerable reduction of thermal conductivities is attributed to the increased phonon scattering enhanced by defect structure, which is formed by doping of Te at Sb site. The phonon scattering might also increase at grain boundaries due to the formation of fine grain structure. The Seebeck coefficient increased considerably as well, consequently optimizing the thermoelectric figure of merit to a peak value of ~0.24 for FeVSb0.94Te0.06. Thermoelectric properties of various Te concentrations were investigated in the temperature range of around 300~973 K.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1535-1540
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• 2022

A solid tungsten target was used at the China Spallation Neutron Source (CSNS) with 100 kW proton beam power. To improve the lifetime, hot isostatic pressing (HIP) process was selected to bond tantalum cladding with tungsten plates. Radioactive isotope ¹⁸²Ta, an activation product of tantalum, was found in the cooling water after a period of operation, however, no radioactive isotopes of ¹⁸⁷W was found, which shows the tantalum layer remained mostly intact. The CSNS Target-1 had been operating safely for three years and was replaced by Target-2 in August 2020.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.255-259
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• 2022

In this study, we fabricated ZnS substrates with excellent transmittance in the mid-infrared region (3-5 ㎛) using hot pressing instead of conventional chemical vapor deposition (CVD). Diamond-like carbon (DLC) was coated on either one or both sides of the ZnS substrates to improve their mechanical properties and transmittance efficiency. To reduce the reflectance and further improve transmittance in the mid-infrared region, anti-reflection (AR) coating was designed for DLC/ZnS /AR and AR/ ZnS /AR structures. The coating structure, microstructure, and optical properties of the AR-coated ZnS substrates were subsequently investigated by employing energy dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared (FTIR) spectroscopy. The FTIR spectroscopy results demonstrated that, in the mid-infrared region, the average transmittance of the samples with AR coating on one and both sides increased by approximately 18% and 27%, respectively. Thus, AR coating improved the transmittance of the ZnS substrates.

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.26-31
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• 2006

In order to effectively improve interfacial adhesion strength between polypropylene (PP) and jute fiber, we particularly incorporated maleic anhydride grafted PP (MAPP) into the matrix through the environment-friendly process without an additional method of process and had better mechanical performances by providing the alignment into the natural fiber than those of the conventional fabrication technology such as an extrusion or injection molding. We also proposed hot pressing method which applied relatively low shear to the composites and confirmed the chemical bonds among the functional groups of MAPP and jute using FT-IR approach. The concentration of MAPP for maximum tensile strength and modulus was optimized at 3 wt%. Flexural properties had no noticeable tendency to increase with MAPP contents compared to tensile strength, which could probably be explained by the degree in wetting of PP/MAPP matrix.

• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.625-625
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• 1991

The specimens for the corrosion test were made by hot-pressing of SiC power with 2 wt% Nl2O3 and 10wt% Al2O3 additions at 2000℃ and 2050℃. The specimens were corroded in 37 mole% NaCl and 63 mole% Na2SO4 salt mixture at 1000℃ up to 60 min. SiO2 layer was formed on SiC and then this oxide layer was dissolved by Na2O ion in the salt mixture. The rate of corrosion of the specimen containing 10 wt% Al2O3 was slower than that of the specimen containing 2 wt% Al2O3. This is due to the presence of continuous grain boundary phase in the specimen containing 10 wt% Al2O3. The oxidation of SiC produced gas bubbles at the SiC-SiO2 interface. The rate of corrosion follows a linear rate law up to 50 min. and then was accelerated. This acceleration is due to the disruption oxide layer by the gas evolution at SiC-SiO2 interface. Pitting corrosion has found at open pores and grain boundaries.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.356-364
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• 1997

In order to study effects of Cu and Be on the microstructure and tensile properties of rapidly solidified Al-Mg alloys, Al-Mg-Cu-Be alloys have been rapidly solidified by inert gas atomization process. Microstructure of rapidly solidified Al-Mg-Cu-Be powders exhibited refinement and good dispersion of Be particles as increasing of solidification rate. Solidification rate of atomized powders was estimated to be about $5{\times}10^{3{\circ}}C/s$. Inert gas atomized Al-Mg-Cu-Be powders were hot-processed by vacuum hot pressing at $450^{\circ}C$ under 100 MPa and hot extruded with reduction ratio in area of 25: 1 at $450^{\circ}C$. The extruded Al-Mg-Cu-Be powders consisted of recrystallized fine Al grains and homogeneously dispersed fine Be particles, and exhibited improved tensile properties with increase in Cu content. $Al_2CuMg$ compounds precipitated in grain and grain boundaries of Al-Mg-Cu-Be alloys with aging heat treatment after solution treatment. Hardness and tensile properties were improved by increasing Cu content and Be addition. Compared with extruded Al-Mg-Cu powders, the extruded Al-Mg-Cu-Be powders exhibited finer recrystallized grains and improved tensile properties by dispersion hardening of Be and subgrain boundaries pinned by fine Be particles. After aging treatment, hardness and tensile properties were improved due to restricted precipitation by increasing of dislocation density around Be particles in matrix.

• Korean Journal of Materials Research
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• v.6 no.3
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• pp.318-323
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• 1996

원소 분말을 합성하여 Ti5SI3 화합물을 합성하는 방법을 연구하였다. 합성법으로서는 기본적으로 반응소결법을 사용하였으며, 치밀화를 위하여는 유사-열간 정수압 성형법(PHIP, pseude-hot isostatic pressing)을 사용하였다. 반응소결법에서는 분말의 입도, 반응온도 및 유지시간이 소결밀도에 영향을 주었으며, PHIP법에 의한 치밀화에서는 압력 및 유지 간이 주요 변수로 사용되었다. 이들 변수중 미세한 입도와 유지시간이 기공을 감소시켰다. 또한 Cu의 첨가 영향을 연구하였는데, 약 6wt%이내의 Cu 첨가는 밀도 향상에 좋은 영향을 미쳤다. 반응소결 및 PHIP를 통해 Ti5SI3 -Cu의 상대밀도를 약 99%까지 높일 수 있었으며, 이때 Cu의 효과는 감도지수 부합됨을 확인하였다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.220-224
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• 1999

Sliding wear test was employed to determine the effect of whisker content and orientation on the firiction and wear behavior of SiC whisker reinforced alumina. Composites containing unidirectionally oriented whiskers were prepared by a modified tape casting followed by lamination, binder removal and hot pressing in order to align the whiskers in the tape casting direction. Wear coefficients on three directions were measured; parallel and normal to the tape casting direction on the tape casting surface and normal to lamination direction on surfnce normal to the tape casting direction. In the effect of whisker orientation, the highest wear rate was obtained in the direction parallel tape casting direction and the lowest in the direction normal to lamination direction at all temperatures. Silicon oxide layer amoothing the surface was detected by energy dispersive X-ray analysis on the worn surface.

• Journal of Powder Materials
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• v.20 no.2
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• pp.85-99
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• 2013

Powder metallurgy applied rapid heating to sintering starting year 1900. Since 1970 the study has intensified. Now rapid sintering concepts embrace a spectrum of options ranging from dunk cycles to microwave, induction, exothermic, electric field, and spark approaches. Most of the efforts are targeting reduced microstructure coarsening during sintering, although reduced material decomposition is another common goal. The efforts are impressive for simple shapes and success metrics such a small grain size after densification. Several barriers need to be removed prior to application in powder metallurgy commercial sintering. Rapid heating research needs to focus on significant property gains, accurate product dimensions, and lower costs. So far each property gain obtained with rapid heating is matched by traditional sintering and composition changes. Several examples are cited to show the goals for the next round of innovations.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.195-198
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• 2008

Graphite and $MoS_2$ were added respectively to the Cu/Sn bond materials of the same composition as a lubricant in order to find out the effect of lubricants on the mechanical properties and the increase in density of the sintered products for microblades. The addition of $MoS_2$ as a lubricant was more beneficial to strength, fracture toughness, and hardness as well as densification than graphite. $MoS_2$ seemed to be more effective in reducing the friction between the metallic powders and die wall during hot pressing process. Due to the better wettability of MoS2 with bond metal alloy, less amount of interfacial defects which is detrimental to mechanical properties use observed.