• 한국세라믹학회지
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• 제35권5호
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• pp.465-471
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• 1998

Lead titanate(PT) and lead magnesium niobate(PMN) ceramic powders were prepared by microwave hy-drothermal method using teflon bomb. Raw materials were Pb(NO3)2 and TiO2 for lead titanate and Pb(NO3)2 Nb2O5 and Mg(NO)3.6H2O for PMN with NaOH as mineralizer in both cases. in lead titanate synthsis rate of microwave hydrothermal method was faster three times than one f conventional hydrothermal methods In lead magnesium niobate synthsis the mixture of perovskite and pyrochlore phases was obtained by single step technique and the PMN was not obtained by double step technique due to low temperature limitation of teflon bomb.

• 한국분말재료학회지
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• 제8권3호
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• pp.174-178
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• 2001

The microstructure and mechanical properties of $Si_3N_4/BN $nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing $\alpha-Si_3N_4$powders covered with turbostratic BN (t-BN). The t-BN coating on $\alpha-Si_3N_4$particles was prepared by heating $\alpha-Si_3N_4$ particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within $Si_3N_4$grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the $Si_3N_4/BN$ microcomposites.

• 한국분말재료학회지
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• 제1권2호
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• pp.174-180
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• 1994

Electrical contact property of the W-20wt%Cu contact materials manufactured by liquid phase sintering of nanocomposite W-Cu powders was investigated and discussed in terms of microstructural development during performance test. Nanocomposite powders were prepared by hydrogen reduction of ball milled W-Cu oxide mixture. They underwent complete densification and microstructural homogenization during liquid phase sintering. As a consequence, the W-Cu contacts produced from nanocomposite powders showed superior contact property of lower arc erosion and stable contact resistance. This might be mostly due to the fact that the arc erosion by evaporation of Cu liquid droplets and surface cracking remarkably became weakened. It is concluded that the improvement of anti-arc erosion of the composite specimen is basically attributed to microstructural homogeneity.

• 한국분말재료학회지
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• 제14권6호
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• pp.405-409
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• 2007

The Cu-based bulk metallic glass (BMG) composites containing Zr-based metallic glass phase have been consolidated by spark plasma sintering using the mixture of Cu-based and Zr-based metallic glass powders in their overlapped supercooled liquid region. The Zr-based metallic glass phases are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation process. The successful consolidation of BMG composites with dual amorphous phases was corresponding to the sound viscous flow of the two kinds of metallic glass powders in their overlapped supercooled liquid region.

• 한국레이저가공학회지
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• 제13권1호
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• pp.1-5
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• 2010

ln this work, the feasibility of using a UV laser for micromachining of powder injection molded parts is examined experimentally. The results, although preliminary, indicate that microfabrication of various parts by laser micromachining of the injection molded parts and then sintering is promising. Particularly, micromachining of a mixture composed of stainless steel particles and polyrner binders was studied using a KrF excimer laser.

• 한국세라믹학회지
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• 제24권2호
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• pp.139-146
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• 1987

${\beta}$-SiC powders were prepared by the simultaneous reduction and carbiding of Jecheon quartzite at 1400$^{\circ}C$ for 7 hours in hydrogen atmosphere, using graphite or carbon black as the reducing and carbiding reagent. The prepared SiC powder was acid-treated with the mixture of fluoric acid and hydrochloric acid at room temperature and also by heating on an alcohol lamp for one hour, respectively. The impurities were mostly eliminated and the purity of SiC became 98.5% after hot acid treatment. The specific surface area of SiC powder was also increased up to 115㎡/g by hot acid treatment. This pure and fine SiC powder was hot-pressed at 1900$^{\circ}C$ for 30min, using 5wt% Al2O3 as a sintering aid. The density, M.O.R., KIC and hardness of the hot-pressed SiC ceramics were 3.195g/㎤, 48.7Kgf/$\textrm{mm}^2$, 5.4MN/㎥/2 and 2,182Kgf/$\textrm{mm}^2$, respectively.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1057-1058
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• 2006

The preparation of $Ti_{50}Cu_{28}Ni_{15}Sn_7$ metallic glass composite powders was accomplished by the mechanical alloying of a pure Ti, Cu, Ni, Sn and carbon nanotube (CNT) powder mixture after 8 h milling. In the ball-milled composites, the initial CNT particles were dissolved in the Ti-based alloy glassy matrix. The bulk metallic glass composite was successfully prepared by vacuum hot pressing the as-milled CNT/$Ti_{50}Cu_{28}Ni_{15}Sn_7$ metallic glass composite powders. A significant hardness increase with the CNT additions was observed for the consolidated composite compacts.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.916-917
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• 2006

Solid Oxide Fuel Cell technology uses powder processes to produce electrodes with residual porosity by partially sintering a mixture of electronically and ionically conducting particles. We model porous fuel cell electrodes with 3D packings of monosized spherical particles. These packings are created by numerical sintering. Each particle-particle contact is characteristic for an ionic, electronic or electrochemical resistance. The numerical packing is then discretized into a resistor network which is solved by using Kirchhoff's current law to evaluate the electrode's electrochemical performance. We investigate in particular percolation effects in functionally graded electrodes as compared to other types of electrodes.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2003년도 international symposium on advanced powder metallurgy
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• pp.90-90
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• 2003

• 한국세라믹학회지
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• 제28권5호
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• pp.390-398
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• 1991

$\beta$-Sialon powder was prepared from Wando pyrophyllite by the carbothermic reduction and nitridation at 135$0^{\circ}C$ for 10 h nitrogen atmosphere. Amorphous silica prepared from Si(OC2H5)4 was added to Wando pyrophyllite powder in order to control the final Z value. Two different methods were applied for synthesis of $\beta$-sialon powders. In Process A, the amorphous silica prepared from Si(OC2H5)4 was admixed to Wando pyrophyllite powder. Process B was started from the mixture of Wando Y2O3 was added to the synthesized $\beta$-Sialon powders as a sintering aid, and the mixed powders were hot pressed at 175$0^{\circ}C$ for 120 min in nitrogen atmosphere under 30 MPa. Their mechanical properties were compared. The maximum values of M.O.R., hardness and KIC were 667 MPa, 16 GPa and 6.3 MN/m3/2, respectively, and they are the values obtained form $\beta$-Sialon ceramics prepared by process A of Z=0.5.