結晶粒 組大化된 機械的 合金化 ODS NiAl의 高溫 機械的 性質

魚淳喆 忠州大學校 1997 한국교통대학교 논문집 Vol.32 No.1

NiAl based oxide dispersion strengthened(ODS) intermetallic alloys have been produced by mechanical alloying(MA) and consolidated by hot extrusion. Subsequent isothermal annealing has been carried out to induce normal grain growth (NGG) and thermomechanical treatment utilizing prestrain and isothermal annealing has also been applied to induce secondary recrystallization(SRx). High temperature mechanical properties of grain coarsened ODS MA NiAl have been investigated, correlating with grain growth mechanisms. The general creep trends of the grain coarsened MA NiAl have also been investigated and compared with those of as-consolidated MA NiAl and other counterparts. It has been shown that SRx leads to a pronounced grain coarsening and high grain aspect ratio without concurrent dispersoid coarsening, which results in improved high temperature mechanical properties as well as creep resistance, whereas limited grain coarsening with dispersoid coarsening by NGG mechanism degrades the high temperature properties.

급지 로울러용 세라믹 용사코팅 조도에 미치는 공정변수의 영향

魚淳喆 충주대 2000 한국교통대학교 논문집 Vol.35 No.1

Thermal spray coating process has proven to be effective at producing hard, dense, wear resistance coatings such as industrial rollers having relatively mild and tough substrates.Since the roughness is a critical factor in high friction applications such as feed roller, ceramic thermal spray coating has been recently considered to be a substitute for rubber lining.Process parameters in ceramic thermal spray coating can affect the properties of end product, and thus the effects of several process parameters on the roughness and related properties in WC ceramic coatings have been investigated and correlated with microstructures in this study.The results indicated that the desired roughness can be controlled by appropriated particle size and distribution along with proper process conditions.

기계적 합금화로 제조한 half-Heusler ZrNiSn1-xSbx 합금에서의 캐리어 이동 특성

어순철 忠州大學校 2011 한국교통대학교 논문집 Vol.46 No.-

Half-heusler ZrNiSn1-xSbx (0.02≤x≤0.08) alloys were prepared by mechanical alloying of elemental powders, and consolidated by vacuum hot pressing. Single phase of the Sb doped ZrNiSn was successfully produced in all doping ranges without subsequent annealing. Phase transformations during mechanical alloying and hot consolidation were investigated using XRD and SEM. Thermoelectric properties as functions of temperature and Sb contents were evaluated for hot pressed specimens. Their doping effect on the thermoelectric and the transport properties were examined. The Hall and Seebeck coefficients confirmed that all the Sb doped compositions exhibited n-type conduction. Relatively high carrier concentration and medium mobility were observed. Sb doping up to x=0.04 in ZrNiSn1-xSbx was shown to be effective on thermoelectric properties, and the figure of merit (ZT) was shown to reach to the maximum at x=0.02 in this study.

기계적 합금화에 의한 Zn4Sb3 열전재료의 합성

어순철 忠州大學校 2003 한국교통대학교 논문집 Vol.38 No.4

Thermoelectric Zn4Sb3 bulk specimens were produced by mechanical alloying using elemental powders and consolidated by hot pressing. 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.

잔류 Ferro-element 검출에 의한 금속간 화합물의 기계적 합금화 공정 분석

魚淳喆 忠州大學校 1999 한국교통대학교 논문집 Vol.34 No.1

Mechanical alloying(MA) process has been applied to produce an intermetallic alloy, NiAl, using Ni and Al enemental powders in an atmosphere controlled high energy attrition mill. A modified thermogravimetric analysis(TGA) technique was used to investigate the degree of alloying as a function of as-milled particle size as well as in as-consolidated specimen. It is shown that the measurement of Curie temperatures in MA intermetallic powders containing ferromagnetic components, when determined as a function of milling parameters, can give some insight into the progress and mechanism of alloying.

機械的 合金化 Zn₄Sb₃ 合金의 相變態 擧動

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.

기계적 합금화 금속간 화합물의 합금화 공정 분석

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.

機械的 合金化 方法으로 製造된 β-FeSi_2의 熱電 特性

魚淳喆 충주대 2003 産業科學論文集 Vol.11 No.-

N-type Fe_0.98Co_0.98Si_2 powders has been produced by mechanical alloying process and consolidated by vacuum hot pressing. As-consolidated iron silicides consisted of untransformed mixture of α-Fe_2Si_5 and ε-FeSi phases. Isothermal annealing has been carried out to induce the transformation to a thermoelectric semiconducting β-FeSi_2 phase. The phase transformation behavior of iron silicide was investigated by utilizing SEM/EDS and XRD analyses. Isothermal annealing at 830 ℃ in vacuum led to the thermoelectric semiconducting β-FeSi_2 phase transformation, but some residual metallic α-Fe_2Si_5 and εFeSi phases were unavoidable even after 96 hours of annealing. Thermoelectric properties of β-FeSi_2 with respect to annealing time were evaluated at room temperature. Thermoelectric properties of annealed specimen were also evaluated as a function of temperature. Thermoelectric properties were remarkably enhanced by isothermal annealing due to the transformation from metallic phases to semiconducting phases. Thermoelectric power factors in β-FeSi_2 to 600 K were lower than published data, leading to a lower estimated figure of merit value of 0.05 t 600 K, possibly due to the existence of metallic phases.

Toner Control Dr. Blade용 세라믹 용사코팅 조도에 미치는 공정변수의 영향

魚淳喆 충주대 2001 한국교통대학교 논문집 Vol.36 No.1

Thermal spray coating process has proven to be effective at producing hard, dense, wear resistance coatings on the relatively mild and tough substrates.Since the roughness is an important factor in wear resistance applications such as toner controller, and thus the effect of process parameters on the subsequent roughness becomes a matter of consideration in ceramic thermal spray coating.The effects of several process parameters on the roughness and related properties in tungsten carbide coatings have been investigated and correlated with microstructures in this study.The results indicated that the desired roughness can be controlled by appropriated particle size and distribution along with proper process conditions.

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.