• 한국추진공학회지
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• 제4권1호
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• pp.65-73
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• 2000

금속기지 복합재료의 주조는 폭넓은 재료의 선택과 공정조건들을 제공하는 좋은 공정이다. 용탕교반기술은 압착주조 또는 분말야금과 비교하면 매우 간단하고 값이 싸기 때문에 주조방법중에서 산업응용에 가장 널리 쓰이는 좋은 방법이다. 최근에는 $\alpha$ -$Al_2O_{3(p)}$/Lo-Ex alloy 복합재료의 입자크기, 입자의 부피 분율, 기계적 성질에 있어서 Mg첨가 그리고 열팽창계수 등이 연구되어 왔다. $\alpha$ -$Al_2O_3$는 입자계면과 기지에 형성되어 기계적 성질에 중요한 역할을 하였다 대부분 복합재료의 인장강도는 증가하지 않지만 16$\mu\textrm{m}$ $\alpha$ -$Al_2O_3$ 입자를 5vol%로 첨가한 경우, 3wt.% Mg를 첨가한 복합재료의 인장강도는 증가한다. 강화재의 부피분율과 mg은 복합재료의 열팽창계수를 감소시켰다.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.391-395
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• 2007

MgO enhanced $(Ba_{0.6}Sr_{0.4})$ $TiO_3$ thick films have been fabricated by a tape casting and firing method for tunable devices on the microwave frequency band. In order to improve ferroelectric properties, the composite thick films enhanced with MgO on BST have been asymmetrically annealed by a focused halogen beam method. Dielectric constants of composite thick films are changed from 1050 to 1300 at 100 kHz after 60 s and 150 s annealing by the focused halogen beam. Even though no prominent changes were previously observed from the thick films before and after annealing in terms of chemical composition and surface morphology, it is clear that the average particle size of the thick films calculated by Scherrer's formula were increased by annealing. Furthermore, a strong correlation between particle size and dielectric constant of the composite thick films has been observed; dielectric constant increases with increased particle size. This has been attributed to the increased volume of ferroelectric domain due to increased particle sizes. As a result, the tuning range was improved by halogen beam annealing.

• 대한금속재료학회지
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• 제46권8호
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• pp.538-544
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• 2008

MMCs were manufactured in two different forms. One was two-layered non FGM composite and the other was four-layered FGM composite. The matrix used in this study was AZ31 magnesium alloy and the reinforcement was $Al_{18}B_4O_{33}$. The composite materials contained reinforcement fibers with a volume fraction of 0, 15, 25 and 40%. Squeeze infiltration method was used for the fabrication of each block. The thermal properties of the FGM alloy and composite joints were studied by conducting thermal cycling tests. The numerical calculation (the finite elements method-FEM) results exhibited a good agreement with the experimental results. Thermal stresses induced by thermal cycling test were clearly reduced in the functionally graded materials.

• Applied Microscopy
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• 제29권3호
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• pp.281-289
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• 1999

교반관법으로 제조한 $AZ91HP/SiC_p$ Mg 복합재료를 틱소포팅하여 미세조직과 존재상들을 조사하였다. $AZ91HP/SiC_p$ Mg 복합재료를 반응고 가공시 액상율 50% 이상에서 완전 충전이 이루어겼으며 전형적인 반응고 조직을 보였다. 복합재료내의 강화상이 초정 $\alpha$상의 합체, 조대화를 억제하여 보다 용이하게 thixotropic 조직을 가질 수 있었다. TEM 관찰결과, 복합재료내의 계면반응 생성물은 MgO, $Mg_2Si$ 및 $Al_{12}Mg_{17}$등이며, 직접 가압시 정출상으로 나타나는 비평형상인 decagonal T상이 관찰되었으며, 이 상은 간접가압시 안정상인 $Al_6Mn$의 형태로 관찰되었다. 이는 간접가압시 승온시간이 직접가압보다 상대적으로 길어, 비평형의 decagonal T상이 안정한 $Al_6Mn$상으로 생성된 것으로 판단된다. 아직까지 생성과정이 명확하진 않으나 교반관법으로 제조 후, 2차가압 성형시 비평형상의 존재는 재료의 강화에 기여할 것으로 판단된다.

• 대한환경공학회지
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• 제33권7호
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• pp.530-535
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• 2011

본 연구는 호소의 부영양화의 원인물질인 인을 효과적으로 제거하고자 개발된 알루미늄-황토 및 란타늄-황토 복합체의 흡착 특성을 평가 하였다. 연구 결과 황토 1 g에 주입된 알루미늄과 란타늄 양이 증가할수록 결합된 양이 비례하여 증가하였다. 알루미늄과 란타늄이 첨가되지 않은 황토와 0.5, 1, 2 mg의 알루미늄과 0.5, 1, 3 mg의 란타늄이 첨가된 복합체를 사용한 경우에 인 제거효율이 다르게 나타났다. 수중의 인 1 mg $PO_4^{3-}$-P/L를 모두 제거하는데 요구되는 양은 알루미늄-황토 복합체가 순수 황토에 비하여 약 2~10배 적은 것으로 나타났다. 또한 란타늄-황토의 경우에는 약 1.5~10배 적게 요구되었다. 제조된 알루미늄-황토, 란타늄-황토 복합체를 수세한 후에 인 흡착 정도를 관찰하기 위하여 복합체를 1~3회까지 수세한 후 결과를 관찰하였는데 수세전과 비교하여 인 제거효율 차이는 크지 않은 것으로 나타났다. pH에 따른 영향은 pH 5~8에서 높은 인 제거율을 보임으로써 개발된 복합체는 일반 자연수계에 살포시 탁월한 인 제거 효능을 보일 것으로 판단된다. 또한 제조된 알루미늄-황토 및 란타늄-황토 복합체는 30분 이내에 빠르게 침전되기 때문에 호소 바닥에서 빠른 시간 내에 안정화 되어 수중의 인과 퇴적층에서 용출되는 인 제어를 담당할 것으로 사료된다.

• 한국분말재료학회지
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• 제11권6호
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• pp.462-466
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• 2004

The bi-materials composed of $Al-5wt{\%}Mg$ and its composite reinforced with SiC particles were prepared by ball-milling and subsequent sintering process. The size of powder in Al-Mg/SiCp mixture decreased with increasing ball-milling time, it was saturated above 30 h when the ball and powder was in the ratio of 30 to 1. Both $Al-5wt{\%}Mg$ powders mixture and $Al-5wt{\%}Mg/SiCp$ mixture were compacted under a pressure of 350MPa and were bonded by sintering at temperatures ranging from 873K to 1173K for 1-5h. At 873k, the sound bi-mate-rials could not be obtained. In contrast, the bi-materials with the macroscopically well-bonded interface were obtained at higher temperatures than 873K. The length of well-bonded interface became longer with increasing temperature and time, indicating the improved contact in the interface between unreinforced Al-Mg part and Al-Mg/SiCp composite part. The relative density in the bi-materials increased as the sintering temperature and time increased, and the bi-materials sintered at 1173K for 5h showed the highest density.

• Biomolecules & Therapeutics
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• 제4권1호
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• pp.59-67
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• 1996

A new composite antibiotic, SM-101(sulbactam·metampicillin), was at dose levels of 0, 375, 750 and 1500 mg/kg/day administered intravenously to pregnant Sprague-Dawley rats during the organogenetic period. Two-third of dams per group were subjected to caesarean section on day 20 of pregnancy and the remaining 10 dams per group were allowed to deliver. Effects of test substance on dams, embryonal development of F1 fetuses, as well as growth, behaviour and mating performance of F1 offspring were examined. In dams, two deaths occurred at 375 and 1500 mg/kg, respectively. The decrease in the weight of adrenal glands of the 1500 mg/kg group was observed. The prolongation of pregnancy period was found at 1500 mg/kg. F1 fetuses showed no changes related to the treatment of SM-101. In F1 offspring, the increase in spleen weight was seen at all doses treated. No treatment-related abnormalities were observed in each treated group in terms of development, behaviour and reproductive performance. In F2 fetuses, no drug-induced abnormalities occurred at all doses. The results show that the no-effect dose levels (NOELS) for dams and Fl offspring are under 375 mg/kg/day and NOELs for F1/F2 fetuses are over 1500 mg/kg/day.

• 한국세라믹학회지
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• 제40권6호
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• pp.530-538
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• 2003

110 K 상의 산화물 고온초전도체를 B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$의 출발조성비로 고상반응법에 의해 합성하였다. 합성된 Bi계 110 K 상의 산화물 고온초전도 물질을 다시 분말 상태로 만든 후, MgO 금속산화물 분말을 5~50 wt%의 각 비율로 혼합하였다. MgO 금속산화물 분말이 혼합된 시편들을 820~86$0^{\circ}C$로 24시간동안 최종 소결시켰다. 그 후, 각 시편들에 대하여 x-선, $T_{c}$, SEM 등을 측정하여 MgO 금속산화물 혼합량에 대한 초전도특성 및 표면의 입자 크기 변화 등에 대한 조사를 진행하였다. MgO 금속산화물의 혼합량이 증가됨에 따라 MgO 관련 피크들의 강도 및 2212 상들의 피크들의 비율은 증가되었고, 시편 내 2223 상의 비율은 감소하고 2212상의 비율은 증가되었다.다.은 증가되었다.다.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.780-786
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• 2011

Mg hydride had high hydrogen capacity (7.6%), lightweight and low cost materials and it was promising hydrogen storage material at high temperature. However, commercial applications of the Mg hydride are currently hindered by its high absorption/desorption temperature, and very slow reaction kinetics. one of the approaches to improve the kinetic is $MgH_x$ intermixed with carbon. And it shows that carbon and carbon allotropes have a beneficial effect on hydrogen sorption in Mg. The graphene is a kind of carbon allotropes which is easily desorbed reaction at low temperatures because its reaction is exothermic. In this work, the effect of graphene concentration on the kinetics of Mg hydrogen absorption reaction was investigated. The $MgH_x$-Graphene composites has been prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD and simultaneous TG, DSC analysis. The hydrogenation behaviors were evaluated by using a sievert's type automatic PCT apparatus. In this research, results of kinetic profiles exhibit hydrogen absorption rate of $MgH_x$-5wt.% and 10wt.% graphene composite, as 1.25wt.%/ms, 10.33wt.%/ms against 0.88wt.%/ms for $MgH_x$ alone at 473K.

• Corrosion Science and Technology
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• 제16권3호
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• pp.151-159
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• 2017

The MA8 alloy (formula Mg-Mn-Се) has been shown to have greater corrosion stability than the VMD10 magnesium alloy (formula Mg-Zn-Zr-Y) in chloride-containing solutions by Scanning Vibrating Electrode Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.