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Formation and Thermal Stability of the Quasicrystalline Phase in Ti-Zr-Ni Alloys
김재용,Jae-Kyun Jeon,이상화,김정기 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Most Ti-based quasicrystals are obtained by rapid quenching, suggesting that they are metastable. Ti-Zr-Ni alloys, however, are known to thermodynamically stable. To investigate the structural stability of quasicrystals formed by 3d-transition-metal alloys, we prepared samples of Ti33+xZr50-xNi17 made with 1) dierent atomic concentrations of Ti and Zr (x = 0, 5, 12, 17 and 22) and 2) various quenching rates from liquids. The existence of quasicrystal phases was examined by using X-ray diffraction (XRD) and was confirmed by obtaining a five-diffraction pattern, which is a forbidden symmetry in solid state physics. Our observations are as follows: 1) with increasing Ti concentration from 33 to 55 at.%, the quasilattice constants decreased from 5.29 Å to 5.15 Å, 2) the coherence length of the quasicrystals was estimated to 195 Å and 3) the quasicrystal phase readily formed over a wide range of concentrations (0 ≤ x ≤ 22 at.%). All our results suggest that the Ti-Zr-Ni quasicrystal phase is found in a wide range of compositions and can be obtained in a thermally stable state.
김재용,문광덕,서권일,Kyung-Wuk Park,최명숙,도경민,Yong-Kee Jeong,Young-Su Cho,이미경 한국식품영양과학회 2009 Journal of medicinal food Vol.12 No.3
This study investigated the beneficial effects of SK1 on obesity and insulin resistance in C57BL/6 mice, which were fed a high-fat diet (37% calories from fat). SK1 is an edible saponin-rich compound from Platycodi radix. The mice were supplemented with two doses of SK1 (0.5% and 1.0%, wt/wt) for 9 weeks. The body weight, visceral fat mass, and adipocyte area were significantly decreased in the SK1 supplemented-groups in a dose-dependent manner compared to the high-fat group. The SK1 supplement significantly lowered plasma triglycerides, total cholesterol, and free fatty acid levels, whereas it significantly elevated the fecal excretion of lipids in the diet-induced obese mice. Supplementation of SK1 decreased the triglyceride and cholesterol levels and the accumulation of lipid droplets in the liver compared to the high-fat control group. High-fat diet induced glucose intolerance and insulin resistance with the elevation of blood glucose levels compared to the normal group; however, the SK1 supplement significantly improved postprandial glucose levels and insulin resistance index. After 9 weeks of being fed a high-fat diet, the mice presented with significantly increased activities of hepatic fatty acid synthase, fatty acid β-oxidation, and glucokinase; however, both 0.5% and 1.0% SK1 supplementation normalized these activities. Notably, SK1 supplementation effectively diminished the ratio of fatty acid biosynthesis to fatty acid oxidation compared to the high-fat group. These results indicate that SK1 exhibits a potential anti-obesity effect and may prevent glucose intolerance by reducing body weight and fat accumulation, increasing fecal lipid excretions, and regulating hepatic lipid and glucose metabolism in high-fat fed mice.
김재용,홍성완,이철태,유영홍 한국화학공학회 1989 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.27 No.2
황산암모늄을 황산화제로 한 TiO₂의 황산화반응에 대해 연구하였다. 본 실험에서 이들 반응은 batch-boat system에서 수행되었으며 반응변수로서 반응온도, 반응시간, 환산암모늄의 양, carrier gas질소의 유량 및 TiO₂의 입도 등을 선정하여 이들이 TiO₂의 황산화반응에 미치는 영향을 조사하였다. 실험결과 본 황산화반응의 적한 반응조건은 반응온도 375℃, 반응시간 2h, TiO₂에 대한 황산암모늄의 mole ratio 9.0, 질소가스의 유량 30㎤/min(반응관 : ID=2.8㎝, L=100㎝), 시료 TiO₂의 입도 -140mesh였으며 이 조건하에서 TiO₂의 98.61%가 Ammonium Titanyl Sulfate[(NH₄)₂TiO (SO₄)₂]로 전환되었다. The reactions of TiO₂ with (NH₄)₂SO₄ were studied. These reactions were carried out in the batch-boat system under nitrogen atmosphere with such variables as reaction temperature, reaction time, mole ratio of (NH₄)₂SO₄ to TiO₂, flow rate of carrier gas (N₂) and particle size of TiO₂. The proper conditions for the reaction were as follows; reaction temperature 375℃, reaction time 2h, mole ratio of (NH₄)₂SO₄ to TiO₂ 9.0, N₂ gas flowrate 30 ㎤/ min (reactor size: ID=2.8 ㎝, L=100 ㎝)and particle size of TiO₂-140 mesh. Under these conditions, conversion TiO₂ to Ammonium Titanyl Sulfate [(NH₄)₂TiO(SO₄)₂] was 98.61%.