Heesung Metal Ltd.

Incheon, South Korea

Heesung Metal Ltd.

Incheon, South Korea
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Lee G.-E.,Korea National University of Transportation | Kim I.-H.,Korea National University of Transportation | Choi S.-M.,Korea University of Technology and Education | Lim Y.S.,Korea Institute of Ceramic Engineering And Technology | And 3 more authors.
Journal of the Korean Physical Society | Year: 2014

p-Type Bi2Te3-Sb2Te3 solid solutions were prepared by mechanical alloying (MA) and hot pressing (HP) under different process conditions, after which the transport and the thermoelectric properties were evaluated. The relative densities of all hot-pressed specimens were over 98%, and the microstructure and crystal orientation were independent of the HP direction. All specimens exhibited p-type conduction, and the electrical resistivity was observed to increase slightly with increasing temperature, indicating a degenerate semiconductor behavior. The carrier concentration decreased with increasing HP temperature while the mobility increased. The maximum figure of merit obtained was 0.86 at 323 K for Bi0.5Sb1.5Te3 hot-pressed at 648 K. © 2014, The Korean Physical Society.


Lee G.-E.,Korea National University of Transportation | Kim I.-H.,Korea National University of Transportation | Choi S.-M.,Korea University of Technology and Education | Lim Y.S.,Korea Institute of Ceramic Engineering And Technology | And 3 more authors.
Journal of the Korean Physical Society | Year: 2014

Bi2Te3−ySey (y = 0.15–0.6) solid solutions were prepared by attrition milling and hot pressing. The lattice constants decreased with increasing Se content, indicating that the Se atoms were successfully substituted into the Te sites. All specimens exhibited n-type conduction, and their electrical resistivities increased slightly with increasing temperature. With increasing Se content, the Seebeck coefficients increased while the thermal conductivity decreased due to the increase in phonon scattering. The maximum figure of merit obtained was 0.63 at 440 K for the undoped Bi2Te2.4Se0.6 solid solution. © 2014, The Korean Physical Society.


Eum A.-Y.,Korea National University of Transportation | Choi S.-M.,Korea University of Technology and Education | Lee S.,Korea Institute of Ceramic Engineering And Technology | Seo W.-S.,Korea Institute of Ceramic Engineering And Technology | And 3 more authors.
Journal of Electronic Materials | Year: 2016

Bi2Te3−ySey:Im (y = 0.15–0.6 and m = 0.0025–0.01) solid solutions were prepared by mechanical alloying and hot pressing. The lattice constants that were measured from x-ray diffraction patterns decreased linearly with increasing Se content, but they were not changed remarkably by I doping. The average relative densities of the hot-pressed specimens are higher than 97%. All of the specimens exhibited n-type conductions in the measured temperature range from 323 K to 523 K, and their electrical conductivity decreased slightly with increasing temperature, indicating degenerate semiconductor behaviors. The electrical conductivity decreased with increasing Se content, whereas it was increased by I doping, and this is in contrast with the Seebeck coefficient; this resulted from the changes of the electron concentrations due to the Se substitution and the I doping. The thermal conductivity decreased with increasing Se content, and this is the result of both the decreased electronic thermal conductivity due to the decreased carrier concentration and the decreased lattice thermal conductivity due to the increased alloy scattering. The maximum dimensionless figure of merit for Bi2Te2.4Se0.6, ZTmax = 0.84 at 473 K, is due to its low thermal conductivity and high Seebeck coefficient. © 2016 The Minerals, Metals & Materials Society


Lee Y.-S.,Inha University | Lee Y.-S.,Korea Institute of Materials Science | Yeon B.-H.,Inha University | Yeon B.-H.,Heesung Metal Ltd. | And 2 more authors.
Materials Letters | Year: 2012

A new type of periodic cellular metal called wire-woven bulk Kagome (WBK) was used as a precursor for creating the composite materials with improved dispersibility. Preheated and non-preheated preforms were placed into molds, and then molten aluminum was poured into them to fabricate composites. The effects of preheating on the wettability and interfacial reaction between the aluminum matrix and the WBK preform were then investigated. The preheated preform composite had good wettability compared to the non-preheated preform composite. Interfacial phenomena between the aluminum matrix and the WBK preform were observed. Our research offers a new avenue for solving the problem of composite material dispersibility. © 2012 Elsevier B.V. All rights reserved.


Cho S.H.,Electronics and Telecommunications Research Institute | Ko J.B.,Korea Advanced Institute of Science and Technology | Ryu M.K.,Electronics and Telecommunications Research Institute | Yang J.-H.,Electronics and Telecommunications Research Institute | And 4 more authors.
IEEE Transactions on Electron Devices | Year: 2015

We report the electrical characteristics of backchannel etch (BCE) metal-oxide-semiconductor thin-film transistor (TFT) comprised of aluminum-doped tin-zinc-indium oxide (ATZIO). It has high etch selectivity in wet chemical etchants, which consist of H3PO4, CH3COOH, and HNO3. This is contrary to the conventional metal-oxide-semiconductors of indium-gallium-zinc oxides, which are highly soluble in the acidic chemicals. As a result, no etch stop layer is needed to protect the backchannel from the wet etchant damage during the source and drain patterning in the bottom-gate-staggered TFT structure. This provides the possibility of oxide TFT fabrication process made as simple as that of the current amorphous silicon TFT using three or four photomasks with short channel length and less parasitic capacitance. The electrical characteristics of our ATZIO BCE-TFTs have the mobility of 21.4 cm2/Vs , subthreshold swing (S.S) of 0.11 V/decade, and threshold voltage of 0.8 V. In spite of the BCE structure, they have excellent stability against bias temperature stress, which shows the threshold voltage shifts of +0.75 V and-0.51 V under the prolonged positive (+20 V) and negative (-20 V) gate bias stresses for 10 000 s at 60 °C, respectively. © 2015 IEEE.


Hwang B.,Andong National University | Paek Y.-K.,Andong National University | Yang S.-H.,Heesung Metal Ltd. | Lim S.,Heesung Metal Ltd. | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

With the doping of Al in ZnO for the preparation of a bulk transparent conductor target, deteriorations were observed in sinterability and uniformity. The doping of 3 wt% Al resulted in the predominance of open pores after sintering at 1300 °C. Less open pores were observed in the ZnO with 2 wt% Al, but the porosity between the inner and outer regions was not uniform due to the preferential evaporation near the surface. To improve both the sinterability and uniformity, mild (<2 MPa) pressure was applied during the preliminary heat treatment at 900 °C, before pressureless final sintering. The pressed specimens showed increased density and uniformity after the final sintering, which were higher than those of the unpressed specimens. The improvements were particularly noticeable in the 3 wt% Al and at 1250 °C, wherein the conventional densification was not successful. © 2011 Elsevier B.V. All rights reserved.


Lee S.-P.,Andong National University | Hwang B.,Andong National University | Paek Y.-K.,Andong National University | Chung T.-J.,Andong National University | And 4 more authors.
Journal of the European Ceramic Society | Year: 2013

The application of a two-step sintering route successfully decreased the sintering temperature of Al-doped ZnO transparent conducting oxide target. The two-step sintering consisted of initial heat treatment (IHT) at 800-1000 °C under mild (<2. MPa) external pressure, and pressureless final sintering at 1250-1350 °C in a separate furnace. The optimum IHTs for effective densification depended on the Al doping. The 800 °C IHT was effective for 1. wt.% Al doping, and the 1000 °C IHT, for 3. wt.% Al doping. As a result of the effective IHT, the volume of the micron sized pore decreased with the fragmentation into submicron pores. This suggests that cohesion of the secondary particles occurred during the effective IHT. The IHT temperature for achieving cohesion increased in the 3. wt.% Al doping. The criterion for determining the IHT in the two-step sintering was identified as the minimum temperature at which the cohesion of secondary particles can be achieved. © 2012 Elsevier Ltd.


Lee J.-R.,Andong National University | Chung T.-J.,Andong National University | Yang S.-H.,Heesung Metal Ltd. | Hong G.-S.,Heesung Metal Ltd. | Oh K.-S.,Andong National University
Ceramics International | Year: 2015

The tube-type transparent conducting oxide target is preferred to the planar type owing to a prolonged life. The uniaxial pressing of 2 wt% Al-ZnO powder into a tube shape and subsequent sintering resulted in a tapered product owing to the nonuniform green density. To suppress the taper, an initial heat treatment (IHT) under an external pressure was applied prior to the main final sintering. The degree of the taper was estimated from the difference in the percentage between the longer and shorter diameters of the tube. The application of pressure (1 MPa) during the IHT at 800 °C decreased the taper from 4.3% to 0.9% after pressureless final sintering at 1250 °C. The application of pressure during the IHT activated shrinkage at the bottom part of the tube and consequently reduced the tapering. With the IHT under pressure, micron-sized voids fragmented into the submicron pores, and the sintering potential was improved. © 2014 Elsevier Ltd and Techna Group S.r.l.


Moon G.-S.,Andong National University | Chung T.-J.,Andong National University | Yang S.-H.,Heesung Metal Ltd. | Hong G.-S.,Heesung Metal Ltd. | Oh K.-S.,Andong National University
Archives of Metallurgy and Materials | Year: 2015

The green body and dense substrate of indium tin oxide was joined by uniaxially pressing at 0.3 MPa at 1300°C to test the restoring of the eroded part of transparent conducting oxide target. The green body was sintered to 98% of theoretical density under the suppression of shrinkage along the boundary below 5%. The boundary between two parts was free of pore but could be recognized from the difference in grain sizes. The joined part had the virtually same density with the substrate, but the grain size was less than one fifth compared with that of substrate.


The present invention is related to a manufacturing method of high purity and refined Ru (Ruthenium) powder produced by using a waste Ru target. Yield of the target and physical properties of a thin film are improved by producing tremendously refined in which oxygen content of the target is decreased, and a crystal particle size is reduced. In order to obtain these merits, powder having a hollow inside is produced by applying plasma to a waste Ru target. Carbon impurities are selectively removed through a atmospheric heat process and Ru powder is oxidized. Thereby, Ru oxide (RuOx) powder is produced. High purity and refined Ru powder is acquired through a hydrogen atmospheric heat process after pulverizing the produced Ru oxide (RuOx) powder into refined shape.

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