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$MoSi_2$/W 복합재료의 합성과 성질에 관한 연구
장대규,Jang, Dae-Kyu,Abbaschian, R. 한국재료학회 1998 한국재료학회지 Vol.8 No.10
$MoSi_2$에 W분말을 첨가하여 $MoSi_2$/W 복합재료를 $1600^{\circ}C$에서 3시간 동안 유지하면서 30MPa의 조건하에서 고온진공 가압기를 이용하여 제조하였으며, 텅스텐 분말의 첨가량이 $(Mo)Si_2$의 미세조직과 기계적 성질에 미치는 영향을 조사하였다. 텅스텐은 몰리브덴과 치환하면서 고용체 합금을 이루었으며, 입자의 크기는 텅스텐 분말의 첨가량이 증가할수록 감소하였다. 비커스경도는 텅스텐 분말의 첨가량이 증가할수록 향상되었으나, 반면에 압흔파단 강도는 오히려 감소되었다. 10%정도의 텅스텐 분말을 첨가하였을 때, 압흔파단 강도가 $4.5MPa$\sqrt{m}$로서 순수 $MoSi_2$의 $2.7MPa\sqrt{m}$에 비하여 향상되었음을 알 수 있었다. $MoSi_2$/W composites were fabricated by vacuum hot press at $1600^{\circ}C$ under 30MPa for 3 hrs. The effects of the amount of tungsten in the composites was explained in terms of the microstructure and mechanical properties. Although tungsten was mainly substituted to Mo atoms forming a complete solid solution of (Mo.W).Si, (x= 1, 5, y=2, 3). the grain size of composites became smaller with the increase of tungsten added. Vickers hardness was increased with the increase of tungsten content due to the solid-solution hardening. On the other hand, toughness of composites decreased sharply by increasing the amount of tungsten. Optimum tungsten amount was determined to be a 10 vol% of composite. Indentation fracture toughness was calculated to be 4.5MPa\sqrt{m}$ in this composites, compared with $2.7MPa\sqrt{m}$ in pure $MoSi_2$.
다양한 유기계 지지체와 광촉매 Nano-ZnO 복합체를 활용한1,1,2-trichloroethylene 제거 효율 평가
장대규(Dae Gyu Jang),안호상(Hosang Ahn),김정연(Jeong Yeon Kim),안창혁(Chang Hyuk Ahn),이새로미(Saeromi Lee),김종규(Jong Kyu Kim),주진철(Jin Chul Joo) 大韓環境工學會 2014 대한환경공학회지 Vol.36 No.11
본 연구에서는 광촉매 nano-ZnO 분말을 수질정화에 사용 후 회수 공정을 생략하기 위해 지지체에 고정화/안정화 시발생하는 효율 저하를 유기오염물의 수착(sorption)으로 극복하고 복합체로부터 nano-ZnO의 탈리(detachment) 현상을 방지 하고자 실리콘(silicone), ABS (acrylonitrile-butadiene-styrene), 에폭시(epoxy), 부타디엔 고무(butadiene rubber)를 선정하여 nano-ZnO/Organic composites (NZOCs)를 제조하였다. 또한, 개발된 다양한 NZOCs의 수중 안정성을 규명 하고, 지하수 내 대표적인 난분해성 유기오염물인 1,1,2-trichloroethylene (TCE)를 대상으로 액상에서 제거 실험을 통해 NZOCs의 활용 타당성을 검증하였다. 연구 결과, 내수성실험을 통해 개발된 NZOCs는 수질정화 용도로 장기간 사용이 타당함을 확인하였다. 또한, FESEM,EDX, imaging 분석을 통해 Nano-ZnO/Butadiene rubber Composite (NZBC)는 다양한 공극과 균열에 nano-ZnO 분말이비교적 균질하게 부착된 반면, Nano-ZnO/Silicone Composite (NZSC), Nano-ZnO/ABS Composite (NZAC), Nano-ZnO/EpoxyComposite (NZEC)는 표면에 공극과 균열이 발달되지 않아 불균질한 부착이 이뤄졌음을 확인할 수 있었다. 또한, NZBC는초기농도 대비 60%의 TCE 수착 능을 보였는데 이는 다른 유기계 지지체와 달리 비결정성 고분자이며, TCE 분자의 소수성분배가 활발히 발생하였기 때문으로 판단된다. 액상에서 TCE의 제거효율(수착+광분해)은 NZBC가 99% 제거 효율로 가장 우수했으며, 복합체 주입량이 증가할수록 TCE 제거효율이 크게 증가하였다. 이러한 결과는 butadiene rubber의 우수한 수착능과nano-ZnO의 광촉매 기작이 동시에 발생하였기 때문인 것으로 판단된다. 마지막으로 액상에서 TCE 제거는 선형모델을 활용해서 비교적 잘 모사할 수 있었으며(R2≥0.936), NZBC의 총 반응상수(Kapp)는 UV에 의한 TCE 분해상수(Kphotolysis) 대비 2.64~3.85배로 높은 값으로 확인되어 butadiene rubber가 TCE 수착 효율이 우수하며, 광분해 기작을 억제하지 않는 지지체로 활용가능한 것으로 판단하였다. In this study, the various organic supports (i.e., silicone, acrylonitrile- butadiene-styrene, epoxy, and, butadiene rubber)with great sorption capacity of organic contaminants were chosen to develop nano-ZnO/organic composites (NZOCs) and to preventthe detachment of nano-ZnO particles. The water resistance of the developed NZOCs were evaluated, and the feasibility of thedeveloped NZOCs were investigated by evaluating the removal efficiency of 1,1,2-trichloroethylene (TCE) in the aqueous phase. Based on the results from water-resistance experiments, long-term water treatment usage of all NZOCs was found to be feasible. According to the FE-SEM, EDX, and imaging analysis, nano-ZnO/butadiene rubber composite (NZBC) with various sizes and typesof porosity and crack was measured to be coated with relatively homogeneously-distributed nano-ZnO particles whereas nano-ZnO/silicone composite (NZSC), nano-ZnO/ABS composite (NZAC), and nano-ZnO/epoxy composite (NZEC) with poorly-developedporosity and crack were measured to be coated with relatively heterogeneously-distributed nano-ZnO particles. The sorption capacityof NZBC was close to 60% relative to the initial concentration, and this result was mainly attributed to the amorphous structure ofNZBC, hence the hydrophobic partitioning of TCE to the amorphous structure of NZBC intensively occurred. The removal efficiencyof TCE in aqueous phase using NZBC was close to 99% relative to the initial concentration, and the removal efficiency of TCE wasimproved as the amount of NZBC increased. These results stemmed from the synergistic mechanisms with great sorption capabilityof butadiene rubber and superior photocatalytic activities of nano-ZnO. Finally, the removal efficiency of TCE in aqueous phaseusing NZBC was well represented by linear model (R2≥0.936), and the Kapp values of NZBC were from 2.64 to 3.85 times greaterthan those of Kphotolysis, indicating that butadiene rubber was found to be the suitable organic supporting materials with enhancedsorption capacity and without inhibition of photocatalytic activities of nano-ZnO.
산소/철분의 함량변화가 티타늄의 기계적 성질에 미치는 영향
심건주,이강인,장대규,서창열 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.1
Using a vacuum consumable arc melting furnace, the methods of adding oxygen and iron to pure titanium and the effects of these additives on the mechanical properties of titanium were studied. The chemical composition and mechanical properties of ASTM grads 1, 3 and 4 were used as targets in the experiments. Addition of oxygen in the form of Ti-10wt% O master alloy gave more consistent results than in the form of TiO₂. Iron was added in the form of powder. Under the pressure employed in the main experiment about 20% and 50% of oxygen and iron were found to be a loss in the process of melting, respectively. As a result oxygen and iron contents of the grades 3 and 4 turned out to be a little higher than expected, giving rise to the much higher ultimate tensile strength and yield strength but slightly higher reduction in area than the lower ASTM limits. The grade 1 to which nothing was added was satisfactory both in the chemical composition and mechanical properties.
자전고온합성법에 의한 이규화몰리브덴의 제조에 관한 연구
김원백,심건주,장대규,서창열,조통래 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.7
MoSi₂ powders were prepared by the SHS (Self-Propagating High-Temperature Synthesis) Method. The measured reaction temperatures varied from 1600K to 1900K, while the reaction rate varied from 1 to 4 ㎜/sec. More than 50% of major metallic impurities were removed through evaporation during the high-temperature synthesis. The reaction temperature and rate were the highest when the precursor Mo and Si powders were mixed at the stoichiometric ratio(Si/Mo=2). At this composition, the measured temperature at the reaction front was 1853K, slightly lower than the theoretical adiabatic temperature, 1900K. The small discrepancy indicates that the reaction is close to adiabatic but not perfectly so. When the precursor powders contained either Mo or Si in excess, both the reaction temperature and rate were found to decrease, with the decreasing rate steeper in Si-rich composition than in Mo-rich one. the difference was explained in terms of the amounts of MoSi₂ at each composition. The reaction rate increased with the apparent bulk density and decreased with the particle size. The apparent activation energy for the reaction was found to be 40±3 ㎉/㏖. This value corresponds to the activation energy of 43 ㎉/㏖ calculated from the growth of Mo_5Si₃ in Mo_5Si₂-Mo diffusion couple. The interdiffusion of Mo and Si through MoSi₂ controls the synthesis reaction.