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임혜인,조혜인 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1
The metallic glass {(Fe_(1−x)Co_x)_(0.75) B_(0.2)Si_(0.05)}_(96)Nb_4 (x = 0 ∼ 0.9) system was studied. One of these systems, {(Fe_(1−x)Co_x)_(0.75) B_(0.2)Si_(0.05)}_(96)Nb_4 (x = 0.5), has the highest glass-forming ability (GFA). We made Co_(36)Fe_(36)B_(19.2)Si_(4.8)Nb_4 into ribbon with a thickness of 0.03 mm, strips with thicknesses of 1 mm, 2 mm, and 3 mm and rods with diameters of 2 mm and 3 mm by melt spinning and injection casting. X-ray diffraction (XRD) and differential scanning calorimeter (DSC) studies showed the cast strips to be fully amorphous up to a thickness of 2 mm. The thermal stability parameters, such as supercooled liquid region (ΔT_x = T_g - T_x) and glass transition enthalpy (ΔH), were measured by using a differential scanning calorimeter to be 41.6 - 45.3 K and 1.2169 - 3.7031 J/g, respectively. The bulk glassy alloys also exhibit soft-magnetic properties in ribbons and semihard magnetic properties in thicker samples, i.e., a high saturation magnetization of 0.94 - 1.11 T and a coercive force of 27.9 - 7162 A/m.
Thermal and Elastic Properties of Cu-Hf-Al Bulk Metallic Glasses
임혜인 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.3
Stable bulk glass forming alloys can be developed over a wide range of compositions in the Cu-Hf-Al ternary system. The compositional and the cooling rate dependences of the thermal and the elastic properties of Cu-Hf-Al alloys were systematically investigated. Evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The glass transition temperature (Tg)and crystallization temperature (Tx) were obtained for the alloys by using differential scanning calorimetry (DSC) at a heating rate of 20 K/min. In the results, the differences between the glass temperature and the crystallization temperature (Tx = Tx . Tg) were measured to have values ranging up to 72 . 74 K. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson’s ratio are also given.
Baicalein Protects 6-OHDA-induced Neuronal Damage by Suppressing Oxidative Stress
임혜인,남은주,이은선,황유진,김용식 대한약리학회 2006 The Korean Journal of Physiology & Pharmacology Vol.10 No.6
The protective effects of baicalein, one of the flavonoids in Scutellaria baicalensis Georgi, were evaluated against 6-hydroxydopamine (6-OHDA)-induced neuronal damage in mice and cultured human neuroblastoma cells. Nigrostriatal damage was induced by stereotaxically injecting 6-OHDA into the right striatum. Baicalein was administered intraperitoneally 30 min before and 90 min after lesion induction. Animals received a further daily injection of baicalein for 3 consecutive days. Two weeks after 6-OHDA injection, contralateral rotational asymmetry was observed by apomorphine challenge in lesioned mice. Tyrosine hydroxylase (TH) immunohistochemistry revealed a significant loss of terminals in lesioned striatum and the reduction of the numbers of TH-positive cell in the ipsilateral substantia nigra (SN). In addition, the levels of dopamine (DA) and DA metabolites were reduced and lipid peroxidation was increased in lesioned striatum. However, baicalein treatment reduced apomorphine-induced rotational behavior in 6-OHDA-lesioned mice, and increased TH immunoreactivity in the striatum and SN, and DA levels in lesioned striatum. Lipid peroxidation induced by 6-OHDA was also inhibited by baicalein treatment. Furthermore, when SH-SY5Y human neuroblastoma cells were treated with baicalein, 6-OHDA-induced cytotoxicity and reactive oxygen species (ROS) production were significantly reduced. These results indicate that baicalein effectively protects 6-OHDA-induced neuronal damage through antioxidant action.
임혜인,안지헤,박조영 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.2
Stable bulk glass forming alloys can be developed over a wide range of compositions in Cu-Hf-Al ternary systems starting from the Cu49Hf42Al9 bulk metallic glass. Ternary Cu-Hf-Al alloys can be cast directly from the melt into copper molds to form fully amorphous strips with thicknesses of 1 to 6 mm. The maximum critical diameter of the new Cu-Hf-Al ternary alloy was 6 mm. X-ray diffraction patterns were used to confirm the amorphous nature of the ternary Cu-Hf-Al alloys. To increase the toughness of these metallic glasses, we reinforced the Cu48Hf43Al9 bulk metallic glass-forming liquid with a 50% volume fraction of tungsten particles and an 80% volume fraction of tungsten wires with diameters of 242.4 µm. Composites with a critical diameter of 7mm and length 70 mm were synthesized. The structure of the composites was confirmed by using X-ray diffraction (XRD), and the scanning electron microscopy (SEM). The mechanical properties of the composites were studied in compression tests. The thermal stability and the crystallization processes of the Cu-Hf-Al alloys and composites were investigated by using differential scanning calorimetry (DSC). Values of the glass transition temperature (Tg), the crystallization temperature (Tx), and the supercooled liquid region (ΔT = Tx - Tg) are given in this paper.
Study on Glass Formation and Properties of the Cu-Hf-Al (Ti) Alloy System
임혜인 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.1
Stable bulk metallic glasses can be found over in the neighborhood of Cu50Hf45Al5 and Cu60Hf25Ti15. The thermal and the mechanical properties of the Cu-Hf-Al and the Cu-Hf-Ti systems are examined. Cu-Hf-Al alloys have a strength of ~2 GPa, a Tg of ~500℃ and a ΔT of ~80℃ . On the other hand, Cu-Hf-Ti alloys have a Tg of ~450℃ and a ΔT of ~50℃, with a strength similar to that of Cu-Hf-Al alloys. The compositional dependences of the thermal and elastic properties of the Cu- Hf-Al (Ti) alloys were studied. In the Cu-Hf-Ti ternary system, the shear modulus G and the bulk modulus B decreased with decreasing Cu concentration.