SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

The effect of the mixing method on the characteristics of hybrid-structure W powder with nano and micro sizes is investigated. Fine WO3 powders with sizes of ~0.6 μm, prepared by ball milling for 10 h, are mixed with pure W powder with sizes of 12 μm by various mixing process. In the case of simple mixing with ball-milled WO3 and micro sized W powders, WO3 particles are locally present in the form of agglomerates in the surface of large W powders, but in the case of ball milling, a relatively uniform distribution of WO3 particles is exhibited. The microstructural observation reveals that the ball milled WO3 powder, heat-treated at 750oC for 1 h in a hydrogen atmosphere, is fine W particles of ~200 nm or less. The powder mixture prepared by simple mixing and hydrogen reduction exhibits the formation of coarse W particles with agglomeration of the micro sized W powder on the surface. Conversely, in the powder mixture fabricated by ball milling and hydrogen reduction, a uniform distribution of fine W particles forming nano-micro sized hybrid structure is observed.

The red ginseng is known to have effects on antioxidativity and cytotoxicity. Nanoscale active substances have various advantages such as improved bioavailability and permeation ability into the cell. However, few studies conducted with the nanoparticles of red ginseng due to its low yield rate and difficulty of manufacturing the product in pilot scale. This study, therefore, investigated the size effects of ultra-fine powder of red ginseng on antioxidativity and cytotoxicity. Red ginseng powder (6, 8, or 158 μm) prepared using a pilot scale was provided by a local company. Antioxidativity was measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays, and cytotoxicity was tested by methylthiazolyl tetrazolium (MTT) assay. The results of DPPH and ABTS radical electron donating ability IC50 of red ginseng were ranged from 2.27 to 3.34 mg/ml and 2.94 to 3.09 mg/ml, respectively, which were not significantly different between all samples. However, the results of cytotoxicity clearly showed a pattern of decreased toxicity in 6 and 8 μm power compared to 158 μm powder. Unexpectedly, particle sizes of red ginseng did not significantly affect antioxidativity. It is believed that these were related to the process of pilot scale production. These phenomena are also believed to be caused by aggregation of low size power particle that increases water holding capacity. From our result, it is concluded that this range of particle size of red ginseng affected the reduction of cytotoxicity.

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-finefecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid(0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing andsintering processes were conduced. In order to examine the effect of cell size (200 µm, 450 µm, 500 µm) in process,pre-samples were sintered for two hours at temperature of 1450˚C, in H₂ atmospheres. A 24-hour thermo gravimetricanalysis test was conducted at 1000˚C in a 79% N₂ + 21% O₂ to investigate the high temperature oxidation behavior ofpowder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased withincreasing cell size. In the 200 µm porous metal with a thinner strut and larger specific surface area, the depletion ofthe stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared withthe 450, 500 µm porous metals.

In this study, by using nickel chloride solution as a raw material, a nano-sized nickel oxide powder with an average particle size below 50 nm was produced by spray pyrolysis reaction. A spray pyrolysis system was specially designed and built for this study. The influence of nozzle tip size on the properties of the produced powder was examined. When the nozzle tip size was 1 mm, the particle size distribution was more uniform than when other nozzle tip sizes were used and the average particle size of the powder was about 15 nm. When the nozzle tip size increases to 2 mm, the average particle size increases to roughly 20 nm, and the particle size distribution becomes more uneven. When the tip size increases to 3 mm, particles with an average size of 25 nm and equal to or less than 10 nm coexist and the particle size distribution becomes much more uneven. When the tip size increases to 5 mm, large particles with average size of 50 nm partially exist, mostly consisting of minute particles with average sizes in the range of 15~25 nm. When the tip size increases from 1 mm to 2 mm, the XRD peak intensities greatly increase while the specific surface area decreases. When the tip size increases to 3 mm, the XRD peak intensities decrease while the specific surface area increases. When the tip size increases to 5 mm, the XRD peak intensities increase again while the specific surface area decreases.

In the current study, the effects of particle size on compaction behavior of water-atomized pure iron powders are investigated. The iron powders are assorted into three groups depending on the particle size; 20-45 , 75-106 , and 150-180 for the compaction experiments. The powder compaction procedures are processed with pressure of 200, 400, 600, and 800 MPa in a cylindrical die. After the compaction stage, the group having 150-180 of particle size distribution shows the best densification behavior and reaches the highest green density. The reason for these results can be explained by the largest average grain size in the largest particle group, due to the low plastic deformation resistance in large grain sized materials.

본 연구에서는 고춧가루의 매운맛을 내는 주성분인 캡사이신 함량을 신속하게 측정할 수 있도록 근적외선 흡광도를 측정할 수 있는 시스템을 구성하였다. 이를 이용하여 동일지역(영광군)에서 생산된 맵지 않은 일반 품종의 고춧가루와 우리나라에서 아주 매운 고추로 알려진 청양 품종의 고춧가루를 혼합하여 만들어진 시료에 대하여 입자의 크기별로 캡사이신 함량을 예측할 수 있는 PLSR 모델을 개발하였다. 고춧가루 입도별로 캡사이신 함량의 예측성능을 향상시키기 위한 스펙트럼 전처리 조건을 구명하였으며, 입도가 캡사이신의 함량 예측에 미치는 영향을 구명하였다. 그 결과를 요약하면 다음과 같다. (1) 고춧가루의 근적외선 흡광도 측정 시스템은 1100-2300 nm 대역에서의 근적외선 흡광도 측정용 AOTF-NIR Spectrometer, 여러 부위의 흡광도를 측정하기 위하여 제작된 시료 회전판, 시료 회전판을 회전시키는 모터, 회전판의 속도를 조절하는 속도조절장치와, 시료 용기 등으로 구성되었다. (2) 1100-2300 nm의 대역에서 고춧가루와 순수 캡사이신 분말의 스펙트럼을 측정한 결과 고춧가루의 스펙트럼 피크들과 캡사이신의 스펙트럼 피크가 유사한 대역에서 나타나, 근적외선 분광법을 이용하여 고춧가루의 캡사이신 함량 예측이 가능한것으로 판단되었다. (3) 고춧가루 입도별(0.425 mm이하, 0.425-0.71 mm, 0.71-1.4 mm)로 획득한 근적외선 흡광도에 대하여 전처리를 달리하여 개발한 캡사이신 함량 예측용 PLSR 모델을 교차검증한 결과 결정계수(RV2)는 0.948-0.979, 예측오차(SEP)는 6.56-7.94 mg% 범위에서 나타났으며, 입도가 작을수록 예측성능이 우수하였다. (4) 3가지 입도를 통합한 고춧가루(입도 1.4 mm이하)에 대하여 캡사이신 함량 예측모델 개발을 위한 최적의 스펙트럼 전처리 조건은 영역 정규화, SNV와 1차 미분 3가지를 순차적으로 적용하는 것이었으며, 이를 이용하여 PLSR 예측모델을 개발하여 교차검증으로 검증할 때 결정계수(Rv2)는 0.959, 예측오차(SEP)는 8.82 mg%로 나타났다. (5) 입도가 구분된 고춧가루에는 입도별 예측모델을 적용하고, 입도가 구분되지 않은 고춧가루는 통합 입도 예측모델에 적용함으로써 캡사이신 함량의 예측정확도를 향상시킬 수 있을 것으로 판단되었다.

In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were investigated as a function of different initial powder size using the high-energy ball milling equipment, which produces the fine powder by means of an ultra high-energy within a short duration. The morphological change of the powders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasing milling time, the size of Si powder was decreased. In addition, more energy and stress for milling were required with the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball milling time. However, the refined powder started to agglomerate at 30 min milling time, while the powder size became uniform at 60 min milling time.

The vacuum infiltration method is one of the composite producing methods. There are several parameters in composite production by vacuum infiltration. One of them is particle size of reinforcement in particulate reinforced composites. In this study, MgO powder and Al were used as reinforcement and matrix respectively. MgO powders with different size and amount to give same height were filled in quartz tubes and liquid metal was vacuum infiltrated into the MgO powder under same vacuum condition and for same time. Infiltration height was measured and microstructure and fracture behavior of composite were investigated. It has been found that infiltration height and fracture strength were increased with particulate reinforcement sizes. It has also been determined that molten metal temperature facilitates infiltration.

alloy powders were prepared using an industrial scale gas atomizer, followed by warm extrusion. The powders were almost spherical in shape. The microstructure of powders as atomized and bars as extruded was examined as a function of initial powder size distribution using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscope (EDS) and X-ray Diffractometer (XRD). The grain sizes were decreased with extruding as well as decreasing the initial powder sizes. Both the ultimate strength and elongation were enhanced as the initial powder sizes were decreased.

The amorphous alloy strip was pulverized to get a flake-shaped powder after annealing at for 90 min and subsequently ground to obtain finer flake-shaped powder by using a ball mill. The powder was mixed with polyimide-based binder of , and then the mixture was cold compacted to make a toroidal powder core. After crystallization treatment for 1 hour at , the powder was transformed from amorphous to nanocrystalline with the grain size of . Soft magnetic characteristics of the powder core was optimized at with the insulating binder of 3wt%. As a result, the powder core showed the outstanding magnetic properties in terms of core loss and permeability, which were originated from the optimization of the grain size and distribution of the insulating binder.

Small powder size is very useful in achieving detailed structures. STS 316 nanopowders with an average diameter of 100 nm and were utilized to produce feedstock. The mixing behavior of the feedstock indicated that the nanoparticle feedstock produced the highest mixing torque at various powder loading compared to the micropowder feedstock. The nanoparticles feedstocks showed that elastic properties are dominant in flow behavior and high viscosity. Conversely the micropowders feedstocks, viscous properties are dominant in flow behavior and less viscosity, nanopowders feedstock perform lower flow activation energy than feedstock with bigger particles.

본 연구에서는 고압 환경에서 합성된 결정 입자의 크기에 원시료(starting materials)의 상(phase)이 미치 는 영향을 확인했다. 상이 다른 두 가지 원시료인 비정질 시료와 나노파우더 시료를 이용해 알루미늄이 부화된 고 압의 환원환경에서 삼원계 시스템인 브리지마나이트-페리클레이스-칼슘 페라이트(calcium ferrite)상의 MgAl2O4을 합성했다. 시료는 40 GPa 2000 K의 압력온도 조건에서 20 시간 동안 가열하여 합성했다. 합성된 시료는 비정질 시료를 이용한 경우 입자 크기가 50-200 nm였으며, 나노파우더를 이용한 경우 ~500 nm로 나타났다. 이러한 차이 는 1) 시료가 합성된 2000 K의 온도가 낮아 비정질 시료의 경우 결정 성장보다 결정핵 성장이 더 우세하게 나타 났거나 2) 시료에 존재할 수 있는 산화 환원반응 상태의 차이로 생각된다. 추후 다원계 시스템에 대한 고압 실험을 수행할 때 비정질 시료보다 나노파우더를 원시료로 이용하는 것이 결정 성장에서 더 유리할 것으로 생각된다.

본 연구에서는 검정찰옥수수 종실을 일반분쇄와 저온미세분쇄를 하여 입자크기에 따른 항산화 활성과 cytotoxicity를 평가하여 이용성 증진을 하고자 연구를 수행하였다. 본 연구의 결과를 요약하면 다음과 같다. 1. 분쇄 정도에 따른 평균값은 일반분쇄가 473.7um , 저온미세분쇄 17.2um 이었으며 중간값은 336.9um 와 13.4um 를 나타내었다. 2. TEAC 활성 측정 결과 일반분쇄는 3.87umol TE/g로서 저온미세분쇄 5.15umol TE/g보다 낮은 활성을 보였다. FRAP 활성 측정에서는 저온미세분쇄가 10.08umol Fe(II)/g로 일반분쇄 8.86umol Fe(II)/g보다 높은 활성을 보였다 3. 간암 세포주(Hep-G2) 성장억제에 미치는 영향은 1 mg/ml 농도에서 검정찰옥수수 종실을 일반분쇄(31.48%)한 것보다 저온미세분쇄(27.41%)를 한 경우가 암세포 생장 억제 효과를 큰 것으로 나타났다. 4. 대장암 세포주인 HCT-116에서는 1 mg/ml에서 분쇄정도에 따라 큰 차이를 보이지 않았으며, 유방암 세포주(MCF-7)에서는 일반분쇄가 미세분쇄보다 높은 생장억제를 보였다.

본 연구에서는 옥수수수염을 일반분쇄기와 저온초미분쇄기를 이용하여 얻은 5단계의 다른 입자 크기의 옥수수수염 분말을 각각의 입자 크기별 이화학적 특성을 검토하고 항산화활성을 평가하여 최적의 입자크기를 찾고 우수한 가공법을 확립하고자 연구를 수행하였다. 본 연구의 결과를 요약하면 다음과 같다. 1. 건조된 옥수수수염을 일반적 분쇄 방법과 저온초미분쇄기를 이용하여 분쇄한 5단계의 입자크기는 각각 199.17um , 178.27um , 85.48um , 27.04um 및 20.97um 로 가장 큰 입자 크기와 가장 작은 입자 크기와는 약 10배 가량 입자크기의 차이가 있었다. 2. 입자크기별 옥수수수염 분말의 색차는 입자의 크기가 작아질수록 명도와 황색도의 수치가 커졌다. 3. 또한 입자크기별 옥수수 수염 분말을 주사전자현미경(SEM)을 이용하여 300배 확대하여 관찰한 결과 입자의 크기가 작아질수록 확대한 입자의 크기가 작은 것을 확인할 수 있었으며 입자의 모양은 다각형의 모양을 보였다. 4. 입자크기별 옥수수수염 분말의 조지방, 조섬유, 조회분, 조단백질 함량과 유리당 함량을 분석한 결과 조섬유 함량과 조단백질 함량은 입자크기가 작아질수록 그 수치가 줄어들었고, 조지방 함량과 조단백질 함량, 유리당 함량은 입자크기 간에 유의적인 차이를 보이지 않았다. 5. 입자크기별 옥수수수염 분말의 총 페놀 함량과 DPPH 라디컬 소거능 모두 입자크기가 작아질수록 그 수치가 증가하였고 통계적으로도 유의적인 차이를 보였다. 6. 옥수수수염 분말의 입자크기에 따른 ascorbic acid equivalents는 입자크기간의 수치적으로는 차이가 있는 것으로 보였으나 통계적으로는 서로간의 유의적 차이가 없는 것으로 나타났으나 TEAC 실험과 FRAP 실험에서는 입자크기가 작아질수록 그 수치가 증가하였고 통계적으로도 유의적인 차이를 보였다. 7. 옥수수수염 분말의 입자크기, 색도, 이화학적 특성 및 항산화 활성간의 상관관계를 분석한 결과 서로 유의적 관계를 보였으며 특히 입자크기가 작아질수록 명도, 적색도, 황색도, 총 페놀 함량, ascorbic acid equivalents, TEAC에서 고도로 유의한 상관관계를 보였다.