Kyoung-Tae Park

Effect of intermetallic compound thickness on anisotropy of Al/Cu honeycomb rods fabricated by hydrostatic extrusion process

Abstract The effect of intermetallic compound (IMC) thickness on the thermal and mechanical properties of Al/Cu honeycomb rods was investigated. The Al/Cu honeycomb rods were fabricated using repeated hydrostatic extrusions at 200 °C. During the process, an IMC layer with 1 μm in thickness was generated at the Al/Cu interface. Different IMC thicknesses were obtained by post-heat treatment at 420 °C for 0.5 to 2 h. The IMC thickness increased to 10.1 μm. The IMC layers were identified as Al2Cu (θ), AlCu (η2), and Al4Cu9 (γ1) phases. The thermal conductivities in the longitudinal direction and cross direction decreased by 11.9% ((268±4.8) to (236±4.4) W/(m·K)) and 10.4% ((210±3.2) to (188±2.8) W/(m·K)), respectively, with increasing IMC thickness. The ultimate tensile strength and elongation of the Al/Cu honeycomb rod are (103±8.4) MPa and (73±6.2)%, respectively. The ultimate tensile strength increased to (131±6.5) MPa until the IMC thickness reached 7.7 μm. It subsequently decreased to (124±3.9) MPa until the IMC thickness reached 10.1 μm. The elongation of the Al/Cu honeycomb rod then sharply decreased to (29±2.5)% with increasing IMC thickness.

Influence of reducing gases on the reduction behavior of water-atomized Fe-Cr-Mo powder

In this study, Fe-based powder of composition Fe-3 wt% Cr-0.5 wt% Mo was prepared using a water atomization process. After atomization, the total oxide content of the powder was calculated as ca. 2.09 wt%. Gas reduction of the as-atomized powder using CO, CH4, and H2 gases was carried out in a horizontal vacuum tubetype furnace at 900 °C. Thermodynamic and kinetic calculations for the reduction reactions were carried out using FactSage and HSC Chemistry programs. The results showed that the reduction proceeded in two stages: from Fe3O4 to FeO, and finally to Fe. Each reducing gas was evaluated and compared based on the oxide reduction capability. The lowest oxygen content was achieved for CH4 (0.49 wt%). However, with CH4, cementite (Fe3C) was also detected due to cracking of CH4.

Thermal Properties of Diamond Aligned Electroless Ni Plating Layer/Oxygen Free Cu Substrates

Abstract The monolayer engineering diamond particles are aligned on the oxygen free Cu plates with electroless Niplating layer. The mean diamond particle sizes of 15, 23 and 50 µm are used as thermal conductivity pathway for fab-ricating metal/carbon multi-layer composite material systems. Interconnected void structure of irregular shaped diamondparticles allow dense electroless Ni plating layer on Cu plate and fixing them with 37-43% Ni thickness of their meandiameter. The thermal conductivity decrease with increasing measurement temperature up to 150 o C in all diamond sizeconditions. When the diamond particle size is increased from 15 µm to 50 µm (Max. 304 W/mK at room temperature)tended to increase thermal conductivity, because the volume fraction of diamond is increased inside plating layer. Keywords: Thermal conductivity, Diamond, Multi-layer materials, Electroless plating ······························································································································· ·································································································