- Effect of Milling Time on the Microstructure and Phase Transformation Behaviors of Ni-B Powder During Mechanical Alloying Process
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Jung-Geun Kim, Wook-Jin Lee, Sung-Kyun Park, Ik-Min Park, Yong-Ho Park
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J Korean Powder Metall Inst. 2011;18(6):496-501.
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DOI: https://doi.org/10.4150/KPMI.2011.18.6.496
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- In this study, the effect of milling time on the microstructure and phase transformation behaviors of Ni-12 wt.%B powders was investigated using vibratory ball milling process. X-ray diffraction patterns showed that the phase transformation of mixed Ni-B elemental powder occurred after 50 hours of milling, with a formation of nickel boride phases. Through the study of microstructures in mechanical alloying process, it was considered that ball milling strongly accelerates solid-state diffusions of the Ni and B atoms during mechanical alloying process. The results of X-ray photoelectron spectroscopy showed that most of B atoms in the powder were linked to Ni with a formation of nickel boride phases after 200 hours of milling. It was finally concluded that mechanical alloying using ball milling process is feasible to synthesize fine and uniform nickel boride powders.
- Synthesis of TiB2 Dispersed Cu Matrix Composite Material by the Combination of the Mechanical Milling and Plasma Activated Sintering Process
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Kyong-Ju Kim, Gil-Geun Lee, Ik-Min Park
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J Korean Powder Metall Inst. 2007;14(5):292-297.
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DOI: https://doi.org/10.4150/KPMI.2007.14.5.292
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- The present study was focused on the synthesis of a TiB_2 dispersed copper matrix composite material by the combination of the mechanical milling and plasma activated sintering processes. The Cu/TiB_2 mixed powder was prepared by the combination of the mechanical milling and reduction processes using the copper oxide and titanium diboride powder as the raw material. The synthesized Cu/TiB_2 mixed powder was sintered by the plasma activated sintering process. The hardness and electric conductivity of the sintered bodies were measured using micro vickers hardness and four probe method, respectively. The relative density of Cu/TiB_2 composite material sintered at 800°C showed about 98% of theoretical density. The Cu-1vol%TiB_2 composite material has a hardness of about 130Hv and an electric conductivity of about 85% IACS. The hardness and electric conductivity of Cu-3vol%TiB_2 composite material were about 140 Hv and about 45% IACS, respectively.
- Influence of Boron Content on the Thermoelectric Properties of p-type Si0.8Ge0.2 Alloy
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Sung-Doo Hwang, Woo-Suk Choi, Ik-Min Park, Yong-Ho Park
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J Korean Powder Metall Inst. 2007;14(4):272-276.
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DOI: https://doi.org/10.4150/KPMI.2007.14.4.272
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- P-type thermoelectric material Si_0.8Ge_0.2 was sintered by Hot Press process (HP) and the effect of boron (0.25sim2 at%) addition on the thermoelectric properties were reported. To enhance the thermoelectric performances, the Si_0.8Ge_0.2, alloys were fabricated by mechanical alloying (MA) and HP. The carrier of p-type SiGe alloy was controlled by B-doping. The effect of sintering condition and thermoelectric properties were investigated. B-doped SiGe alloys exhibited positive seebeck coefficient. The electrical conductivity and thermal conductivity were increased at the small amount of boron content (0.25sim0.5 at%). However, they were decreased over 0.5 at% boron content. As a result, the small addition of boron improved the Z value. The Z value of 0.5 at% B doped Si_0.8Ge_0.2 B alloy was 0.9times10-4/K, the highest value among the prepared alloys.
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