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Mechanical Behavior and Microstructure of Al-10wt.% Nb Alloy Fabricated by Mechanical Alloying
Ahn In Shup,Jung, Kwang Chul,Kim, Sang Shik,Kim, Yoo Young 대한금속재료학회(대한금속학회) 1999 METALS AND MATERIALS International Vol.5 No.6
Al-10%Nb alloy powders were fabricated by mechanical alloying and their mechanical behavior and microstructure were investigated by means of tensile testing, differential scanning calorimetry, X-ray diffraction and electron microscopy. An intermetallic compound of Al₃Nb was partially formed in the mechanically alloyed powders. The grain size was 50 nm after mechanical alloying for 20 hours, and increased to 500 nm after hot extrusion at 400℃. However the 20 size of the intermetallic compounds of precipitated Al₃Nb in an A1 matrix, did not vary with hot extrusion. The density of the consolidated Al-Nb alloy was over 97% relatively with hot extrusion. Both the tensile strength and elongation decreased at the elevated temperature. As the temperature increased, the dimples in the fracture surface were large and of coalescent shape, and the fracture was caused by the precipitated phases of Al₃Nb.
Synthesis of Titanium Carbide Nano Particles by the Mechano Chemical Process
Ahn, In-Shup,Park, Dong-Kyu,Lee, Yong-Hee The Korean Powder Metallurgy Institute 2009 한국분말재료학회지 (KPMI) Vol.16 No.1
Titanium carbides are widely used for cutting tools and grinding wheels, because of their superior physical properties such as high melting temperature, high hardness, high wear resistance, good thermal conductivity and excellent thermal shock resistance. The common synthesizing method for the titanium carbide powders is carbo-thermal reduction from the mixtures of titanium oxide($TiO_2$) and carbon black. The purpose of the present research is to fabricate nano TiC powders using titanium salt and titanium hydride by the mechanochemical process(MCP). The initial elements used in this experiment are liquid $TiCl_4$(99.9%), $TiH_2$(99.9%) and active carbon(<$32{\mu}m$, 99.9%). Mg powders were added to the $TiCl_4$ solution in order to induce the reaction with Cl-. The weight ratios of the carbon and Mg powders were theoretically calculated. The TiC and $MgCl_2$ powders were milled in the planetary milling jar for 10 hours. The 40 nm TiC powders were fabricated by wet milling for 4 hours from the $TiCl_4$+C+Mg solution, and 300 nm TiC particles were obtained by using titanium hydride.
Ahn, In-Shup,Bae, Sung-Yeal,Kim, You-Young 대한금속재료학회 2004 METALS AND MATERIALS International Vol.10 No.1
In the present study, equi-atomic porous TiNi shape-memory alloys have been successfully prepared by self- propagating high-temperature synthesis (SHS) using elemental titanium and nickel powders. The porous TiNi alloys thus obtained have an open porous structure with about 64 vol.% porosity, and the pore size is about 1.8 mm. The effect of preheating temperature on the microstructure has been investigated. It was found that the pore size increased with increasing preheating temperature. Moreover, the preheating temperature was shown to have a significant effect on the microstructure of the SHS-synthesized porous TiNi shape memory alloys. Aluminum was infiltrated into porous TiNi shape-memory alloys and the damping property of Al/TiNi was measured by a vibration analyzer (FFT analyzer). The specific damping capacity of Al/TiNi composites is 70 % that of a pure TiNi ingot.
Synthesis of Titanium Carbide by Thermo-Chemical Methods with TiH2 and Carbon Black Powders
( In Shup Ahn ),( Tek Kyoung Sung ),( Sung Yeal Bae ),( Ho Jung Cho ),( Dong Kyu Park ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 METALS AND MATERIALS International Vol.12 No.3
A new synthesizing method for producing submicron TiC powders was studied by using TiH2 and carbon black powders. It is well known that hydrogen absorption transforms titanium from metal (h.c.p.) to brittle hydride (f.c.c.) powders by ball-milling. This research focused on obtaining submicron-sized TiC powders from the ball-milled mixture of TiH2 and carbon black by thermal treatment. The hydrogen, carbon, iron, and oxygen composition changes in the mixed powders were analyzed. Thereafter, a differential thermal analysis (DTA) test was performed to observe change of phase with ball-milling time. The TiC powders were obtained by heat treating the powders milled for 5 h at various temperatures (600-1200℃). The phase microstructure was investigated via DTA, X-ray diffraction (XRD), and scanning electron microscope (SEM). The mixture milled for 2 h had an f.c.t. structure containing 66.73 at.%H transformed to f.c.c. by milling for 4 h. After 5h of ball-milling, submicron-sized particles of 273 nm were obtained. At the isothermal heat-treating temperature of 500℃, the Ti single phase was formed completely, and the TiC phase of lattice parameter 0.310 nm was completely formed over the temperature of 1000℃.
기계적합금법에 의해 제조된 TiNi합금의 수소화반응특성에 관한 연구
안효준(Hyo Jun Ahn),김보수(Bo Su Kim),황진환(Jin Hwan Hwang),안인섭(In Shup Ahn),김기원(Ki Won Kim),허보영(Bo Young Hur) 한국수소및신에너지학회 1994 한국수소 및 신에너지학회논문집 Vol.5 No.2
The hydrogenation behavior of Ti-Ni powders prepared by mechanical alloying in a high energy ball mill have been investigated by P-C isotherm curves, DSC(differential scanning calorimetry), X-ray diffractometer, SEM(scanning electron microscope). Amorphous TiNi phase was formed after 10 milling hours. The hydrogen storage capacity gradually decreased as a function of mechanical alloying time. There appears the DSC endothermic peak due to hydrogen evolution of amorphous hydride phase.
Discharge properties of a lithium/sulfur cell at body temperature
Kim, Ic-Pyo,Park, Jin-Woo,Ahn, Hyo-Jun,Ahn, In-Shup,Kim, Ki-Won,Ahn, Jou-Hyeon,Ryu, Ho-Suk Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>To investigate the feasibility of a Li/S cell for application to medical devices, the discharge properties of Li/S cells were investigated at 36.5 °C. A Li/S cell has the first discharge capacity 1158 mA h (g-S)<SUP>−1</SUP> at body temperature, whose cathode is composed of sulfur, carbon black and PVdF. The Li/S cells were discharged at various current densities to evaluate the rate capability, and the cycle performance at 100 mA g<SUP>−1</SUP> current density was also studied compared with previous reports.</P>