The electromagnetic wave (EM) absorption properties of various particle size have been investigated in a sheet-type absorber using the alloy powder. With decreasing the average particle size, the complex permeability () and permittivity () increased and the matching frequency is shifted toward lower frequency. The fabricated EM wave absorbers showed permeability , permittivity for a mesh sample, and the calculated power absorption was as high as 80% in the frequency range over 2 GHz.

수화현상의 대표적 원인 생물인 남조류의 M. aeruginosa와 대조구로서 녹조류인 C. zofingiensis를 인공 배양하여 분말세라믹 투여에 따른 선택적 조류 제거 가능성에 대해 실험하였다. 0.05 mm의 분말세라믹을 투여에 따른 M. aeruginosa 및 C. zofingiensis의 침전효율은 각각 82와 63%였으며, 입자크기 0.1과 1 mm의 경우에서 는 M. aeruginosa는 각각 69와 34%, C. zofingiensis는

Novel polymer mold process for fabrication of microcomponents using metal nanopowders was developed and experimentally optimized. Polymer mold for forming green components was produced by using a hard master mold and polydimethylsiloxane (PDMS). In the preparation of metallic powder premix for the green components without any defect, 90 wt.% 17-4PH statinless steel nanopowders and 10 wt.% organic binder were mixed by a ball milling process. The green components with very clear gear shape were formed by filling the powder premix into the PDMS soft mold in surrounding at about . Cold isostatic pressing (CIP) was very potent process to decrease a porosity in the sintered microcomponent. The microgear fabricated by the improved process showed a good dimension tolerance of about 1.2%.

A process known as the MR and EMR combination process is able to overcome the shortcomings of the MR (metallothermic reduction) and EMR (electronically mediated reaction) process. The effects of as the raw material, sodium as the reducing agent and KCl/KF as the diluent on the characteristics of tantalum powder are investigated. In this study, a MR-EMR combination process has been employed to tantalum powder on the location of reductant. The excess of reductant were varied from 25, 50 to 75 wt%. The total charge and external circuit decreases as the amount of reductant increases. The average particle size increases with increasing the amount of reductant.

Various approaches have been proposed to increase the green density. Warm compaction method has been used for the reduction of residual stress, the improvement of magnetic properties and the higher densities. In this work, the effect of warm compaction on green density of Fe powder was investigated. After ball-milling of Fe oxide powder for 30 hours, Fe oxide powder was reduced through the hydrogen reduction process. The pure Fe powder and polymer binder were mixed by 3-D tubular mixer. And then the mixed powder was warm-compacted with various compaction pressure and binder contents. The green density of specimen was added polyvinyl binder was higher than any other specimens.

In the metallothermic reduction (MR) process used to obtain tantalum powder in one batch, it is difficult to control the morphology and location of the tantalum deposits. On the other hand, an electronically mediated reaction (EMR) process is capable of overcoming this difficulty. The effect of using as the raw material and sodium as the reducting agent on the characteristics of tantalum powder are investigated. As the temperature of the reduction varied from 1023K to 1223K, the powder particles obtained with MR were relatively large , while those prepared via EMR were of uniform . In the MR process, the Ta powder recovery rate increased from 37% to 83% at 1123K in constrat with EMR process.

It is well known that thermal plasma process has lots of advantages such as high temperature and good quality for synthesis of nano particles. In this research, we attempt the synthesis of nano unitary and composite powder (Ag, Mg-Al, Zr-V-Fe) using transferred thermal plasma. Nano particles of metal alloy, ranging from 20 nm to 150 nm, have been synthesized by this process.

Ultrasonic-milling of metal oxide nanopowders for the preparation of tungsten heavy alloys was investigated. Milling time was selected as a major process variable. XRD results of metal oxide nanopowders ultrasonic-milled for 50 h and 100 h showed that agglomerate size reduced with increasing milling time and there was no evidence of contamination or change of composition by impurities. It was found that nanocomposite powders reduced at in a hydrogen atmosphere showed a chemical composition of 93.1W-4.9Ni-2.0Fe from EDS analysis. Hardness of sintered part using 50 h and 100 h powder samples was 399 Hv and 463 Hv, respectively, which is higher than the that of commercial products (330-340 Hv).

It prepared the TiO2 powder which has photo-catalytic activity in the visible-light by the wet process with titanium oxysulfate. The titanium dioxide(TiO2) by the wet process creates a new absorption band in the visible light region, and is expected to create photocatalytic activity in this region. Anatase TiO2 powder which has photocatalytic activity in the visible light region, is treated using microwave and radio-frequency(RF) plasma. But, the TiO2 powder for the visible light region, which also can be easily produced by wet process. The wet process TiO2 absorbed visible light between 400nm and 600nm, and showed a high activity in this region, as measured by the oxidation removal of aceton from the gas phase. The AH-380 sample appears the yellow color to be strong, the catalytic activity in the visible ray was excellent in comparison with the plasma-treated TiO2. The AH-380 TiO2 powder, which can be easily produced on a large scale, is expected to have higher efficiency in utilizing solar energy than the plasma-treated TiO2 powder.

The general composition like moisture content, and the physical and sensory characteristics of the steamed rice cake added with powder of roots of balloonflowers were as follows. The moisture content in the roots was 4.13±0.01%, crude protein 9.24±0.11%, crude fat 3.07±0.04%, crude fiber 33.82±0.01%, and crude ash 8.16±0.02%. The moisture content of the cake was decreased with increase of the root’s powder added. In physical characteristic, the hardness of the cake was increased with increase of the powder. The control cake was the highest in the cohesiveness. The springiness tended to be increased with increase of the powder. The gumminess was higher with increase of the powder, being 530.33% in the control and 284.44% in the sample with 12.0% powder added. The adhesiveness was decreased with increase of the powder. The color change was significantly decreased with increase of the powder. With increase of the powder, the value a was decreased, while the value b showed to be increased. In a sensory test, the favorite degree to color, flavor, bitter taste, moistness, soft-ness and overall acceptability was measured to get the follow result. To color, the lot with 6% of the balloonflower powder added showed the highest accept-ability with the same highest result also to flavor and bitter taste. The moistness and the softness were revealed as the highest at the control, and the chewiness was also highest at the lot with 3% of the powder added. The overall acceptability was highest as 5.75 at the lot with 6% of the powder added, coming out to be higher in order of the 3% added-lot, the control, the 9%-lot and the 12%-lot.

Using spark plasma sintering process (SPS), Ti-6Al-4V alloy powders were successfully consolidated without any contamination happened due to reaction between the alloy powders and graphite mold. Variation of microstructure and mechanical properties were investigated as a function of SPS temperature and time. Compared with hot isostatic pressing (HIP), the sintering time and temperature could be lowered to be 10 min. and , respectively. At the SPS condition, UTS and elongation were about 890 MPa and 24%, respectively. Considering the density of 98.5% and elongation of 24%, further improving the tensile strength would obtain by increasing the SPS pressure.

The mother Ni-W (1-5 wt.%) alloy billets for coated conductor substrate were fabricated by powder metallurgy process. The tensile test results for the sintered Ni-W rods showed the increase of mechanical strength and decrease of ductility with increasing W content due to the solid solution hardening. All the fracture surfaces of the tested specimens showed the typical ductile fracture mode of dimple rupture due to the local necking. The Ni-W alloy billets were made into tape by cold rolling. After the appropriate heat treatment for recrystallization, the brass texture formed by the cold rolling was converted to the complete cube texture. The in-plane and out of plane texture of the tapes estimated by x-ray pole figure were smaller than 9 degree and 7 degree, respectively. The effect of the W addition on the texture development seems not to be significant.

The effect of a CAM (Continuous Attrition Mill) treatment on the sinterability of ex-ADU powder was investigated. As the cycles of a CAM increased, the apparent density, specific surface area and O/U of the milled powder increased, but there particle sizes decreased. However the sintered density of the pellet decreased as the cycles of the CAM increased. It is considered that the decrease of the sintered density is due to the formation of , which was produced by a CAM mechanism

The microstructural and mechanical properties of Al-Si alloyed powder, prepared by gas atomization fallowed by hot extrusion, were studied by optical and scanning electron microscopies, hardness and wear testing. The gas atomized Al-Si alloy powder exhibited uniformly dispersed Si particles with particle size ranging from 5 to . The hot extruded Al-Si alloy shows the average Si particle size of less than . After heat-treatment, the average particle size was increased from 2 to . Also, mechanical properties of extruded Al-Si alloy powder were analyzed before and after heat-treatment. As expected from the microstructural analysis, the heat-treated samples resulted in a decrease in the hardness and wear resistance due to Si particle growth. The friction coefficient of heat-treated Al-Si alloyed powder showed higher value tough all sliding speed. This behavior would be due to abrasive wear mechanism. As sliding speed increases, friction coefficient and depth and width of wear track increase. No significant changes occurred in the wear track shape with increased sliding speed.

본고에서는 고유한 원자구조에 기인한 우수한 특성으로 인해 구조재료 및 기능재료로서 그 활용이 기대되고 있는 벌크 아몰퍼스 소재에 있어 온간압출, 온간압연, 방전 플라즈마 소결(Spark Plasma Sintering)등 과냉각액체온도구간에서의 점성유동을 이용한 고화성형 공정의 최근 기술동향에 대해 간략히 소개했다.