The densification of the compacts of Co+32%Cr+20%W+l.5%C, Co+32%Cr+20%W+3.0%C and Co+32%Cr+20%W+4.5%C sintered under gas or vacuum was investigated. The effect of V and B addition on the densification was also investigated. The densification of these compacts were always incomplete regardless of sintering atmosphere, temperature and time. The amounts of oxygen and carbon in compacts sintered in for 3.6ks at 1523K were 0.105~0.160 mass% and 0.33~0.89 mass%, respectively. And those in vacuum were 0.028~0.032% and 0.957~4.08%, respectively. Relative density(Ds) of Co+29%Cr+17%W+3.0%C compact containing 6%V and Co+32%Cr+20%W+2.97%C compact containing 0.03%B were 99 and 100%, respectively, indicating complete densification by solid phase sintering. Victors hardness of sintered compacts containing 6%V or 0.03%B were 632 and 568, showing 50~60% increase in comparison to those without V or B. These results can be explained in terms of oxidation/reduction of oxides and equilibrium pressure of CO in isolated pore, instead of presence of liquid formation and grain boundary separation from pores due to large grain growth.

본 연구에서는 분극성을 갖는 미세분말/유전유체 분산계내의 전기유변효과를 mechanism을 중심으로 고찰하였다. 전기유변효과를 일으키는 mechanism을 (1)입자표면전도(surface conductance) (2)입자내부전도(bulk conductance(3) 유도분극(induced polarization)으로 구분하여 설명하였다. 소수성(anhydrous-base)전기유변유체 내의 미세분말 입자간 상호인력을 예측할 수 있도록 유도분극 mechanism을 적용하여 수학적으로 모델화 함으로써 전기유변효과를 향상 시키기 위한 재료선정의 기초로 하였다. 전기유변유체의 미세입자로 이용될 수 있다고 여겨지는 ceramic, ferrite 및 polymer등 7가지 재료를 선정하여 계산한 결과 ceramic및 ferrite입자가 입자간 상호인력이 큰것으로 나타났다.

This paper evaluates the chemical resistance of mortar according to mixing ratios by using ferronickel slag fine powder which is an industrial by - product and various admixtures. The test results showed that the chlorine ion penetration resistance was the best when the ferronickel slag fine powder and gypsum were used as the admixture. The chemical erosion resistance was highest when ferronickel slag, quicklime, gypsum and calcium chloride were combined.

This study investigated the compressive strength characteristics of concrete and mortar containing waste pottery fine powder. To identify the effects of waste pottery fine powder on the compressive strength of concrete and mortar, cement was replaced with waste pottery fine powder at 5, 10 and 15% rates and the variations in compressive strength were evaluated. For high strength concrete, compared with a control mix, 5% replacement resulted in the reduction of 3.4% in compressive strength at 7 days; however, at 28 days, the strength actually increased by 2.5%. For normal strength concrete, compared with a control mix, 5% replacement resulted in the reduction of 20.4% in compressive strength at 7 days, and 14% reduction at 28 days. As for the mortar, at 5% replacement, compared with a control mortar mix, compressive strength of mortar decreased by 3% at 7 days, while an increase of 5.9% was observed at 28 days. Therefore, the optimum replacement rate of cement with waste pottery fine powder appears to be 5%.

This paper describes the findings of the study conducted to evaluate compressive strength characteristics of high-strength concrete containing waste pottery fine powder. The experimental variables selected were 5, 10, and 15 percent replacements of cement with waste pottery fine powder. The findings are summarized as follows: (1) compared with the strength of the control specimens with no replacement rate, compressive strength of the concrete at 7days decreased by 4% at 5% replacement rate of cement with waste pottery fine powder, but (2) compressive strength of the concrete at 28days increased slightly by 1.3%..

Compressive strength characteristics of mortar containing waste pottery fine powder were investigated in this study. The experimental variables selected were 5, 10, and 15 percent replacements of cement with waste pottery fine powder. The findings are summarized as follows: (1) compared with the strength of the control specimens with no replacement rate, compressive strength of the mortar at 7days decreased by 3% and 9.3%, respectively at 5% and 10% replacement rate of cement with waste pottery fine powder, but (2) compressive strength of the mortar at 28days increased by 5.9% and 6.9%.

This study evaluates the material performance of slump value and compressive strength of the concrete which was made by recycled sand and blast furnace slag powder(BFSP). The main variables are replacement ratio of BFSP. As a result, it was evaluated that more detailed evaluation is needed in long-term strength development and the compensation of slump value to the replacement ratio of BFSP.

고순도 니켈 금속염으로부터 미세하고 입도가 균일한 니켈 분말 직접 제조 연구를 수행하였다. 구형의 형상을 갖는 미세한 니켈 분말을 제조하기 위하여 입도제어가 가능한 슬러리환원법을 사용하였다. 제조된 니켈 분말에 화학성분, 입도, X선회절, 주사전자현미경 분석을 실시하여 니켈 분말의 특성을 조사하였다. 환원제로 하이드라진(hydrazine)을 사용하고, 4.5 M NaOH에서 90분 반응시켜 약 100~200 nm의 입도를 가진 분산도가 양호한 구형의 니켈 분말을 제조할 수 있었다.

초미세 분쇄법은 식품의 가공방법 중 하나로 특히 이를 이용하여 음용으로 활용범위를 넓힐 수 있다. 본 연구는 이에 착안하여 감을 이용한 초미세 분말을 이용하여 항산화 활성과 자가면역질환인 아토피에 효과가 있는지를 확인하여 보았다. 감 초미세 분말을 이용하여 DPPH와 FRAP 항산화 활성 실험을 수행 하였으며, 마우스 동물모델을 이용한 항알러지 피부염 동물모델을 이용하여 확인하였다. 항산화 활성 실험 결과 감 초미세 추출물은 농도에 따른 활성 등