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Electronic Transport Properties of Ni-doped CoSb3 Prepared by Hot Pressing
어순철,김일호 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
Ni-doped CoSb3 skutterudites (Co1−xNixSb3) were prepared by hot pressing, and their electronic transport properties were examined. Single-phase δ-(Co,Ni)Sb3 was successfully obtained, but it decomposed to δ-(Co,Ni)Sb2 and Sb when x ≥ 0.2, which means that the solubility limit of Ni in Co is x < 0.2. The negative signs of the Seebeck coefficients for all Ni-doped specimens revealed that Ni atoms acted as n-type dopants by substituting for Co atoms. The electrical resistivity and the thermal conductivity decreased with increasing Ni doping level. The ZT (dimensionless figure of merit) value was considerably enhanced by the Ni doping, and the optimum composition was found as Co0.9Ni0.1Sb3 for Ni-doped CoSb3 prepared by hot pressing.
Thermoelectric Properties of Tin-Filled Skutterudites Prepared by Mechanical Alloying Process
어순철,권준철,김일호 대한금속·재료학회 2008 METALS AND MATERIALS International Vol.14 No.5
Sn-filled (Fe,Co)Sb₃ skutterudites of the form of SnyFe3Co5Sb24 (0 ≤ y ≤ 1.5) were synthesized by the mechanical alloying of elemental powders followed by vacuum hot pressing. The phase transformations that occur during both mechanical alloying and vacuum hot pressing were examined by X-ray diffraction. Single-phase Sn-filled skutterudite was successfully produced by vacuum hot pressing using as-milled powders without subsequent annealing. The thermoelectric properties of the hot-pressed specimens were evaluated as a function of temperature and tin content. The void filling of tin (up to y = 1.0) in Fe₃Co5Sb24 appeared to increase the thermoelectric figure of merit.
어순철 忠州大學校 2004 한국교통대학교 논문집 Vol.39 No.1
Solid state synthesis by hot pressing has been used in order to produce high efficiency Zn4Sb3 bulk specimens. Single phase Zn4Sb3 with 98.5% of theoretical density were successfully produced by direct hot pressing of elemental powders containing 1.2 at.% excess Zn. Direct synthesis by hot pressing provides an optional processing route in this material.
플라즈마 용사법에 의해 제조된 알루미나 IC Heat Sink의 특성
어순철,이영근 忠州大學校 2002 한국교통대학교 논문집 Vol.37 No.4
Plasma spray coating has been employed to prepare the alumina heat sink for hermetic 4 sided seal type IC packaging.
魚淳喆 충주대 산업과학기술연구소 1999 産業科學論文集 Vol.7 No.1
Mechanical alloying(MA) process has been applied to produce an intermetallic alloy, NiAl, using Ni and Al elemental powders in an atmosphere controlled high energy attrition mill. In order to characterize alloying process, thermal variations along with oxygen level variations in the system and X-ray diffraction pattern variations as a function of milling time have been investigated throughout the milling process. As-milled intermetallic powder characteristics have also been analyzed and discussed in this study.
기계적 합금화로 제조한 N형 β의 상변화 및 열전 특성
어순철,Eo, Sun-Cheol 한국재료학회 2002 한국재료학회지 Vol.12 No.5
N-type ${\beta}-FeSi_2$ with a nominal composition of $Fe_{0.98}Co_{0.02}Si_2$ powders has been produced by mechanical alloying process and consolidated by vacuum hot pressing. As-milled powders were of metastable state and fully transformed to ${\beta}-FeSi_2$ phase by subsequent isothermal annealing. However, as-consolidated $Fe_{0.98}Co_{0.02}Si_2$ consisted of untransformed mixture of ${\alpha}-Fe_2Si_ 5$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce the transformation to a thermoelectric semiconducting ${\beta}-FeSi_2$ phase. The transformation behavior of ${\beta}-FeSi_2$ was investigated by utilizing DTA, a modified TGA under magnetic field, SEM, and XRD analyses. Isothermal annealing at $830^{\circ}C$ in vacuum led to the thermoelectric semiconducting ${\beta}-FeSi_2$ phase transformation, but some residual metallic $\alpha$ and $\varepsilon$ phases were unavoidable even after prolonged annealing. Thermoelectric properties were remarkably improved by isothermal annealing due to the transformation from metallic $\alpha$ and $\varepsilon$ phases to semiconducting phases.
기계적 합금화에 의한 Zn<sub>4</sub>Sb<sub>3</sub> 열전소재의 합성 및 열전 특성
어순철,Ur Soon-Chul 한국재료학회 2004 한국재료학회지 Vol.14 No.8
Thermoelectric $Zn_{4}Sb_3$ alloy powders were synthesized from elemental powders by mechanical alloying process and consolidated by hot pressing under controlled atmosphere. Single phase $Zn_{4}Sb_3$ was not obtained using a nominal stoichiometric composition, but near single phase $Zn_{4}Sb_3$ with remnant elemental Zn having a relatively high density was produced using a nominally 11.7 $at.\%$ Zn rich powders. Phase transformations during mechanical alloying were systematically investigated using XRD and SEM. Thermoelectric and transport properties were evaluated for the hot pressed specimens and compared with results of analogous studies.
Thermal Spray Coating의 耐磨耗 特性 向上에 관한 硏究
魚淳喆 忠州大學校 1998 한국교통대학교 논문집 Vol.33 No.1
Thermal spray coating process has proven to be effective at producing hard, dense, wear resistance coatings on the relatively mild substrates. The thermal spray coating technique is now widely used to improve various surface characteristics such as corrosion/oxidation resistance, wear resistance and electrical/thermal insulation properties using cermet, intermetallics or ceramics. Among several spraying techniques, HVOF(High Velocity Oxygen Fuel) and plasma coating process are preferentially used particularly for wear resistance application such as capstan. The effects of pre-treatment, in-process and post-treatment parameters on the structures and wear properties of several coating processes of WC + 12% Co, Cr₃C₂and Al₂O₃powder coatings on medium carbon steel substrates have been studied. Several process conditions were investigated and compared in order to optimize the process conditions on microstructure, phase structure, microhardness, adhesive strength and abrasive wear resistance of the coatings, especially in capstan application. The result indicates that carbide coating is more preferable to the oxide coatings and the post-treatments consisting of vacuum annealing and sealing on the carbide coatings lead to significant improvements in wear resistance, adhesive strength and phase stabilization over the other processing techniques in this application.
魚淳喆 충주대 2004 産業科學論文集 Vol.12 No.-
Thermoelectric Zn₄Sb₃ alloy powders were synthesized from elemental powders by mechanical alloying process and consolidated by hot pressing under controlled atmosphere. Single phase Zn₄Sb₃ was not obtained using a nominal stoichiometric composition, but near single phase Zn₄Sb₃ with remnant elemental Zn having a relatively high density was produced using a nominally 11.7 at.% Zn rich powders. Phase transformations during mechanical alloying were systematically investigated using XRD and SEM. Physical properties were evaluated for the hot pressed specimens and compared with results of analogous studies.