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.

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.

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.

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.

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.

핫프레싱법에 의한 Zn₄Sb₃ 합금의 고상반응합성

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.

機械的 合金化 NiAl의 二次再結晶化에 따른 크리프 下限 應力의 擧動

魚淳喆 忠州大學校 1996 한국교통대학교 논문집 Vol.31 No.1

NiAl based ODS(Oxide Dispersion Strengthened) intermetallic alloys have been produced by mechanical alloying(MA) process and consolidated by hot extrusion. Subsequent thermomechanical treatments have been applied to induce secondary recrystallization in an attempt to improve creep resistance in this material. The creep behavior of secondary recrystallized MA NiAl has been investigated and compared with those of as-extruded condition. Minimum creep rates were shown approximately two orders of magnitude lower than that in as-extruded condition. The improvement in creep resistance is believed due to the grain coarsening as well as increase in grain aspect ratio. However, the threshold stress, below which no measurable creep rate can be detected, becomes negligible presumably due to dispersoid coarsening and a decrease in grain boundary area during secondary recrystallization.

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.

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.