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이강래 ( Kang Rae Lee ),최경환 ( Kyeong Hwan Choe ),조규섭 ( Gue Serb Cho ),이경환 ( Kyong Whoan Lee ),김명호 ( Myung Ho Kim ),임경화 ( Kyung Hwa Rim ),김기영 ( Ki Young Kim ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.5
N/A Vibrational motions of the compaction table were investigated to select the optimal operation conditions of sand filling and compaction for the EPC process. Their modes were measured at the nine points of the table with changing the relative rotation angles between the two eccentric mass vibrators which were attached parallel beneath the table. Well-defined vibration modes were measured at the center of the table but those of left and right sides of the table were distorted regardless of rotational angle differences. The distortion of vibration modes at both sides of the table were caused by the moment generated by offset positions of two eccentric masses. It was found that the uniform vibration modes would be gathered by controlling the relative distances between the rotating axis and the center of gravity in the compaction system at the various conditions of vibration modes and rotational angle differences.
Al-xMg-CNT 복합분말체의 용융특성에 미치는 마그네슘 첨가와 온도의 영향
임정규 ( Jung Kyu Lim ),최경환 ( Kyong Hwan Choe ),김상섭 ( Sang Sub Kim ),조규섭 ( Gue Serb Cho ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.4
We conducted melt-down experiments on Al-xMg-carbon nanotube (CNT) complex powder compacts at 700℃ and 800℃ for carrying the CNTs into the molten Al7021 matrix alloy. The parameters in the melting experiments were the holding temperatures and the amount of Mg content. The microstructures of the melt-down compacts were observed by optical microscopy (OM) and field emission scanning electro-microscopy (FESEM). The several phases obtained from the reaction products within the Al-xMg-CNT compacts were identified by energy dispersive X-ray spectroscopy (EDXS) and X-Ray diffractometry (XRD). The complete melt-down area was increased due to a large addition of Mg in the compacts and outer areas remained as undissolved powder compacts due to the large number of oxidation products such as MgO, MgAl2O4 and Al2O3. CNTs were observed on the surface of Al powders with oxidation products at 700℃ in a melting experiment. However, at 800℃, the CNT agglomerates moved away from the center because of the poor wettability and low density of the CNTs.
Al-CNT 복합펠렛의 계면반응에 미치는 마그네슘 첨가 및 제조 조건의 영향
임정규 ( Jung Kyu Lim ),최순열 ( Soon Yool Choi ),최경환 ( Kyong Hwan Choe ),김상섭 ( Sang Sub Kim ),조규섭 ( Gue Serb Cho ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.5
In the present study, Al-CNT pellets were investigated to understand the effect of Mg addition and manufacturing conditions on the interfacial reactions between Al and CNTs in Al-CNT pellets. The pellets were heated and held at 700 ℃ and 800 ℃ for 2 hours under nitrogen (N2) atmosphere. To confirm the reactions between Al and CNT in the pellets under different manufacturing conditions, the microstructures were observed by optical microscopy (OM) and field emission scanning electro microscopy (FESEM). And, the composition and reaction phases were analyzed by energy dispersive X-ray spectroscory (EDXS) and X-ray diffractometry (XRD). The presence of oxidation products and Mg on the surface of Al powder in the pellets appeared to prevent the formation of Al4C3. But, Al4C3 reaction products were increased due to the high temperature of 800 ℃, which produced a high amount of reduced aluminium and increased the reaction areas between Al and CNT. The Al-CNT pellets compacted under air atmosphere prohibited the reaction between Al and CNT because of the high amount of oxidation products, such as MgO and MgAl2O4.