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전기선폭발법으로 제조된 텅스텐 분말의 산소 조성이 방전플라즈마소결 거동에 미치는 영향
김철희,이성,김병기,김지순,Kim, Cheol-Hee,Lee, Seong,Kim, Byung-Kee,Kim, Ji Soon 한국분말야금학회 2014 한국분말재료학회지 (KPMI) Vol.21 No.6
Effect of oxygen content in the ultrafine tungsten powder fabricated by electrical explosion of wire method on the behvior of spark plasma sintering was investigated. The initial oxygen content of 6.5 wt% of as-fabricated tungsten powder was reduced to 2.3 and 0.7 wt% for the powders which were reduction-treated at $400^{\circ}C$ for 2 hour and at $500^{\circ}C$ for 1h in hydrogen atmosphere, respectively. The reduction-treated tungsten powders were spark-plasma sintered at $1200-1600^{\circ}C$ for 100-3600 sec. with applied pressure of 50 MPa under vacuum of 0.133 Pa. Maximun sindered density of 97% relative density was obtained under the condition of $1600^{\circ}C$ for 1h from the tungsten powder with 0.7 wt% oxygen. Sintering activation energy of $95.85kJ/mol^{-1}$ was obtained, which is remarkably smaller than the reported ones of $380{\sim}460kJ/mol^{-1}$ for pressureless sintering of micron-scale tungsten powders.
김철희,채현병,이창우,김정한,이세헌,Kim, Cheol-Hee,Chae, Hyun-Byung,Lee, Chang-Woo,Kim, Jeong-Han,Rhee, Se-Hun 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.1
Laser-rotating arc hybrid welding was introduced by combining $CO_2$ laser and rotating gas metal arc welding. While the arc rotation enhances the weld pool motion, it reduces the undercut formation which is one of most critical weld defects in the conventional laser-arc hybrid welding. This research investigated the bead characteristics according to the welding parameters such as frequency of rotation, welding voltage, shielding gas composition and interspacing distance between laser and we. The welding parameters were selected to reduce spatter generation and ensure sound weld beads fur bead welding and butt welding with various joint gaps. Gap bridging ability was improved, such that the sound weld beads were achieved for butt joint with up to 2mm joint sap, with no adjustment of CTWD(Contact tip-to-workpiece distance) and electrode diameter.
Al 5052, 6061합금에 대한 플라즈마-GMA 용접공정특성 평가
김철희,안영남,최진강,이세헌,Kim, Cheol-Hee,Ahn, Young-Nam,Choi, Jin-Kang,Rhee, Se-Hun 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.6
In this study, the bead-on-plate welding were conducted by using GMA welding and plasma-GMA welding on Al 5052 and, Al 6061 plates. For these processes, the maximum welding speeds for full penetration were compared, and various weld qualities such as bead appearance, cross-section, cracks and porosities were examined. Faster welding speed, cleaner bead surface and more stable drop transfer could be achieved by plasma-GMA welding, compared with GMA welding.
유기 킬레이터들을 이용한 구리 식각에 대한 반응성 평가
김철희,임은택,박찬호,박성용,이지수,정지원,김동욱,Kim, Chul Hee,Lim, Eun Taek,Park, Chan Ho,Park, Sung Yong,Lee, Ji Soo,Chung, Chee Won,Kim, Dong Wook 한국재료학회 2021 한국재료학회지 Vol.31 No.10
The reactivity evaluation of copper is performed using ethylenediamine, aminoethanol, and piperidine to apply organic chelators to copper etching. It is revealed that piperidine, which is a ring-type chelator, has the lowest reactivity on copper and copper oxide and ethylenediamine, which is a chain-type chelator, has the highest reactivity via inductively coupled plasma-mass spectroscopy (ICP-MS). Furthermore, it is confirmed that the stable complex of copper-ethylenediamine can be formed during the reaction between copper and ethylenediamine using nuclear magnetic resonance (NMR) and radio-thin layer chromatography. As a final evaluation, the copper reactivity is evaluated by wet etching using each solution. Scanning electron micrographs reveal that the degree of copper reaction in ethylenediamine is stronger than that in any other chelator. This result is in good agreement with the evaluation results obtained by ICP-MS and NMR. It is concluded that ethylenediamine is a prospective etch gas for the dry etching of the copper.