[en] Hard carbon and microcrystalline graphite (MG) core-shell structured composite materials are prepared, and their electrochemical performances as an anode material for lithium-ion batteries are reported. The composite materials are obtained by coating a mixture of MG and pitch onto hard carbon particles, followed by heating at 1200 °C under an argon atmosphere for 1 h. The surface of the hard carbon is subsequently covered with a layer of the MG/pitch carbon composite. In the coating layer of the MG/pitch carbon composite, the MG particles are divided into nanoscale graphite sheets, and uniformly dispersed within the pitch of carbon matrix. The composite particles have a rounded shape, especially when the content of MG increases, which can improve their packing density compared to hard carbon having sharp edges. Anodes prepared from these composite materials exhibit enhanced electrochemical performances, including a high reversible capacity, high initial coulombic efficiency, high charging/discharging rate capability, and desirable cycling stability

[en] Highlights: ► Thermo-mechanical treatments and C addition improved the mechanical and electrical properties. ► The difference of properties was affected by the Fe precipitates phases and sizes. ► The Fe₃P particles were only marginally affected by the final processes. - Abstract: The microstructures, secondary-phase particles and precipitates of thermo-mechanically treated non C-alloyed and 0.0133 wt.% C-alloyed Cu–2.5Fe–0.1P alloys were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All of the thermo-mechanical treatment processes consequentially improved the mechanical and electrical properties. The Fe₃P particles were only marginally affected by the final processes. The Fe precipitates, by contrast, showed different phases and sizes resulting from C-alloying and the final processes; thus, the mechanical and electrical property changes manifested in the alloys were attributed to the Fe precipitates.

[en] Three types of oxide layers Al₂O₃, Al_1.98Cr_0.02O₃, and AlFeO₃ phases on the surface of Fe–22Cr–6Al (FeCrAl) foam during pre-oxidation were characterized by means of transmission electron microscopy (TEM). The growth rate of each oxide layer was investigated using measurement of total weight gain. The Al₂O₃ layer mainly affected the growth rate of the total oxide layer, and it hindered the diffusion of Fe and Cr atoms from the matrix to the oxide layers.

[en] Highlights: • The hardness and strength of pure titanium fabricated by SLM were increased with increasing the laser power. • During the SLM processing, the concentrations of oxygen and nitrogen in the SLM parts were increased. • The oxidation and nitriding were thermodynamically possible under SLM. - Abstract: This study analyzed the variation of mechanical properties and its causes with increasing the laser power in the fabrication of pure titanium by selective laser melting (SLM). SLM samples were fabricated using commercially pure titanium grade 1 powder when the scan speed was 1000 mm/s and the laser power as 120, 200, 280, 360, and 440 W, respectively. As the laser power increased, the hardness and strength of the samples increased gradually. During the SLM processing, the concentrations of oxygen and nitrogen in the SLM samples were increased, which resulted in the increase of hardness and strength. The SLM equipment used in this study removed oxygen in the chamber by flowing high purity argon gas and fabricates the sample while preserving the oxygen concentration in the atmosphere to 0.2%. Evaluating the possibility of oxidation and nitriding during the SLM process by thermodynamic analysis, it was found that the process occurred under conditions in which temperature and residual oxygen and nitrogen partial pressure led to oxidation and nitriding.

[en] Highlights: • The range of SLM process condition to achieve over 99.5% relative planar density of SUS316L. • Correlation study between microstructural, mechanical and chemical properties of SUS316L according to the high density process conditions for SLM. • Locally property tuning of SUS316L part by controlling the process condition of SLM selectively. The effects of laser energy density on microstructural, mechanical properties, and chemical composition of stainless steel 316 L (SUS316L) parts fabricated by selective laser melting (SLM) technology were studied. Total 36 specimens were fabricated under the range from 1.3 to 46.7 J/mm³. The process conditions to achieve over 99.5% ± 0.1% relative planar density were obtained, and the mechanism of tunable mechanical properties was investigated by understanding the correlation between the microstructure and chemical composition according to the energy density. As the energy density increased, tensile properties were decreased with grain growth and the concentrations of light elements were increased by accelerating dissolution. As the concentrations of light elements increased, the mechanism of destructive behavior changed from ductile fracture to brittle fracture and it caused that the hardness was improved. Consequently, it was necessary to control the energy density from 9.34 to 23.98 J/mm³ in order to fabricate SUS316L parts of high strength and high elongation characteristics by SLM method.

[en] A comparative study on the difference in interfacial behavior of thermally aged Cu wire bonding with Al and Au pads was conducted using transmission electron microscopy. During high-temperature lifetime testing of Cu wire bonding with Al and Au pads at 175 °C for up to 2000 h, different growth rates and growth characteristics were investigated in the Cu–Al intermetallic compounds (IMCs), including CuAl₂, CuAl and Cu₉Al₄, and in the Cu–Au IMCs, including (Au,Cu), Cu₃Au and (Cu,Au). Because of the lower growth rates and greater ductility of Cu–Au IMCs compared to those of Cu–Al IMCs, the Cu wire bonding with the Au pad showed relatively better thermal aging properties of bond pull strength and ball shear strength than those with the Al pad counterpart. In this study, the coherent interfaces were found to retard the growth of IMCs, and a variety of orientation relationships between wire, pad and interfacial IMCs were identified

[en] Highlights: • Oxidation layer thickness of CaO added AM60 increases with increasing amounts of CaO. • Effect of CaO is that the columnar grains on AM60 grow along the [1 0 0]_M_g_O. • A initial oxidation layer thickness and ignition temperature is closely connected. • The columnar oxide layer formed due to Ca, which dissolved from CaO. - Abstract: A transmission electron microscopy analysis was conducted on the oxide layers of Mg–5.5Al–0.25Mn (AM60) alloys with different levels of CaO content formed in a thermogravimetric analyzer (TGA) system at 450 °C for 7 h. It was found that the oxide layer in AM60 + CaO grew as a columnar structure and, resultantly, that the oxide layers had different thicknesses with different levels of CaO content. The columnar oxide grains that were formed on the Mg + CaO alloy grew on the [1 0 0]_M_g_O, resulting in a more compact and thicker initial oxide layer compared to the normal oxide layer. The columnar growth of the oxide layer in AM60 + CaO formed due to the Ca, which dissolved from CaO