III–V based magnetic (GaMnAs)/nonmagnetic(AlAs) semiconductor superlattices (SLs) have been grown by low-temperature molecular beam epitaxy. X-ray diffraction measurements show that the SLs have good crystalline quality and abrupt interfaces. The SLs having relatively wide (Ga,Mn)As layers (⩾70 Å) are found to be ferromagnetic at low temperatures, while the SLs with narrow (Ga,Mn)As layers (⩽50 Å) are paramagnetic even at 2.0 K. Magneto-optic spectra have revealed that, due to the quantum confinement effect, the interband transition energy at Γ is blue shifted with decreasing the thickness of the (Ga,Mn)As and some subbands are formed.
Ultrasonic welding is a solid-state welding technique that can bond materials at a relatively low temperature and pressure. In this study, steel/steel and steel/Ni combinations were successfully bonded by ultrasonic welding, and the development of the bonding interface was examined. The bonding strength was obtained by a lap shear test and increased with welding time, as did the fraction of bonded area observed by SEM. The bonding process sequence was investigated by SEM and electron backscatter diffraction (EBSD) analysis of a cross-section at the bonding interface. It was revealed that abrasion is caused by oscillation to form small particles consisting of steel and Ni and that the particles are grown and subsequently flattened with welding time. Bonding is achieved by the flattened particles spreading along the bonding interface without any voids.
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