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심건주(Gun Choo Shim),최국선(Good Sun Choi) 대한금속재료학회 ( 구 대한금속학회 ) 2002 대한금속·재료학회지 Vol.40 No.9
Titanium diboride and zirconium diboride powders were synthesized with TiO2(ZrO2)-B2O3-Mg by employing a magnesium thermite technique. In place of B2O3, H3BO3 was also tried as a source of boron with limited success. Removing the by-product MgO by acid leaching, metal borides of submicron size with basically spherical shape could be obtained. In the case of TiB2, a small amount of TiN was formed besides MgO during the synthesis reaction due to high temperature exposure of the reactants to air. Though ZrB2 could be similarly synthesized as TiB2 using the same technique, it was difficult to remove residual ZrO2 even after acid leaching. The presence of ZrN was not as apparent as that of TiN. The spark plasma sintering method was used to sinter the synthesized TiB2 without using any additives. At temperatures of 1600℃ and higher, relative density greater than 98% was obtained. The maximum Vickers hardness of the sintered body was 3360(32.9 GPa). Two sets of commercial powders with particle size of 3 and 16 μm respectively were tested at 2000℃ for comparison but they showed relative density less than 80%. The surface conditions of the sintered commercial powders were unfit for the hardness test.
Ti-Cr-V 합금의 수소화-탈수소화에 따른 상천이 및 열처리에 의한 수소저장특성의 향상
유정현,조성욱,심건주,최국선,박충년,최전,You, Jeong-Hyun,Cho, Sung-Wook,Shim, Gun-Choo,Choi, Good-Sun,Park, Choong-Nyeon,Choi, Jeon 한국수소및신에너지학회 2006 한국수소 및 신에너지학회논문집 Vol.17 No.2
The alloys which compositions were represented by the formula, $Ti_{(0.22+X)}Cr_{(0.28+1.5X)}V_{(0.5-2.5X)}$ ($0{\leq}X{\leq}0.12$), had the total hydrogen storage capacity higher than 3 wt% and the effective hydrogen storage capacity higher than 1.4 wt%. Particularly, among all the tested alloys, the $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy exhibited the best effective hydrogen storage capacity of 1.65 wt%. Furthermore, the reversible bcc${\leftrightarrow}$fcc structural transition was observed with hydrogenation and dehydrogenation, which predicted the possibility of pressure cycling. EDS analysis revealed micro-segregation, which suggested the necessity of microstructure homogenization by heat treatment. The $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy was selected for heat treatment and for other related studies. The results showed that the total and the effective hydrogen storage capacity increased to 3.7 wt% and 2.3 wt%, respectively. The flatness of the plateau region was also greatly improved and heat of hydride formation was determined to be approximately -36 kJ/mol $H_2$.
Zr<sub>57</sub>V<sub>36</sub>Fe<sub>7</sub>게터합금의 수소흡수특성에 미치는 분쇄의 영향
박제신,서창열,심건주,김원백,Park, Je-Shin,Suh, Chang-Youl,Shim, Gun-Choo,Kim, Won-Baek 한국재료학회 2006 한국재료학회지 Vol.16 No.2
The effects of milling time in argon and hydrogen atmospheres on the hydrogen sorption speed of a getter alloy, $Zr_{57}V_{36}Fe_{7}$, was studied. The hydrogen sorption speed of milled alloys was evaluated at room temperature. In argon, as the oxygen content increased with milling time, the hydrogen sorption speed decreased accordingly. In hydrogen, on the other hand, the oxygen content decreased at first with milling time but started increasing after 5 hrs of milling time. Similar to the case of argon, however, the hydrogen sorption speed changed exactly in the opposite direction with the oxygen content, exhibiting the maximum rate at 5 hrs. These results suggest that in both atmospheres the hydrogen sorption speeds are inversely related with the oxygen contents.
게터용 Zr57V36Fe7합금의 수소 흡수특성에 미치는 산소농도의 영향
박제신 ( Je Shin Park ),우샛별 ( Saet Byul Woo ),서창열 ( Chang Youl Suh ),박미영 ( Mi Young Park ),심건주 ( Gun Choo Shim ),김원백 ( Won Baek Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.5
The effects of the oxygen concentration on the hydrogen sorption properties of an NEG(non-evaporable getter) alloy, Zr(57)V(36)Fe7, were investigated. The desired level of the oxygen concentration was obtained by letting an argon gas with 2.98 vol% O2 flow through a tube furnace containing the alloy powder at 423 K for a predetermined time period. The sorption speed of the alloy decreased almost linearly with the increase of the oxygen concentration. The reason for this can be explained as follows: the activated metal surface area decreases with the increase of the oxygen concentration and the activation of the metal surface covered with oxygen requires more energy to remove it.
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.
천병선,원창환,장대규,심건주 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6
The combustion synthesis of titanium carbide from elemental powders has been experimentally studied as following. 1) All the products synthesized by SHS method were nearly pure TiC powders. The lattice constant was increased with increasing C/Ti atomic ratio, however, at about 0.8 C/Ti atomic ratio the lattice constant reached a plateau of 4.325Å. 2) The combustion of titanium and carbon powders was accompanied by the evolution of gases having steady state combustion mode with propagation rate of 10㎜/sec. at 2600℃. 3) The size distribution of the product was relatively wide in the range of 2㎛ and 40㎛.
김흥원,천병선,원창환,심건주,고석권 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.12
The SiC powder was prepared by a SHS process using SiO₂, Mg and C as raw materials to determine the optimum process variables. The results obtained from this study may be summarized as follows; 1) The mole ratio between C and Mg affected the magnesiothermic reduction reaction most and the highest yield of SiC was obtained at the mole ratio of SiO₂ : Mg : C = 1.0 : 2.5 : 2.2. 2) The propagation speed of combustion reaction was about l0㎜/sec increasing with the decrease of SiO₂ particle size. 3) The amount of unreacted silicon decreased with increasing compaction pressure. 4) Impurities were found to decrease by evaporation during the high temperature reaction or by solution during leaching process. 5) The particle size of prepared SiC powders was in the range of 0.2∼1.0 microns with the purity of about 98.885 weight percent.