Search

Sm 2 Co 17 -type permanent magnets have important application value due to their advanced magnetic properties, which can be ascribed to their unique cellular structure and element segregation in various phases developed after isothermal aging treatment. In this study, the evolution of the microstructure combined with the microchemistry of Sm 2 Co 17 -type magnets from solid solution precursor to the cellular structure is investigated, and a new insight into the formation of the cellular structure is provided. We report for the first time that a large number of strip-like nanoscale short-range ordered micro-domains are distributed in the disordered matrix of the solution precursor, which serve as the nucleation centers in the formation of the embryos of the cellular structure. Based on atomic scale structural analyses, a new mechanism concerning the ordering transformation from short-range 2:17R microtwins to long-range 2:17R phase is proposed, involving collective glide of three partial dislocations on successive basal planes with the net Burgers vector to be zero. Furthermore, microchemistry analysis reveals that the segregation of Cu and Fe in the early stage of isothermal aging is accelerated substantially during the ordering transformation, indicating that the ordering transformation can act as a new driving force for element segregation in Sm 2 Co 17 -type magnets. These findings provide new considerations for the development of high performance Sm 2 Co 17 -type magnets. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract: The field-emission properties of the ZnO nanotip arrays, nanowire arrays as well as Al-doped ZnO nanowires were investigated in detail. After comparison of the different morphologies, it was found that the morphology of the nanostructure ZnO materials has played a crucial role in their field emission performances, especially the turn-on field and the emission current density. Among them, the ZnO nanotip arrays have the lower turn-on field, higher current density, which is attributed to the small emitter radius on the nanoscale and the well vertical align on the substrates. It can effectively improve the field-emission property to dope aluminium in ZnO nanowires because of the carrier concentration increasing, which results in the increase of the field enhancement factor and the reduction of the work function. The emission stability is very good from the emission persistence measurement. [Copyright &y& Elsevier]

Highly c-axis oriented LiNbO3 thin film has been deposited on the SiO2/Si substrate by KrF excimer pulsed laser deposition (PLD) technique under optimized conditions of 30-Pa oxygen pressure and 600 °C substrate temperature. The amorphous SiO2 buffer layer was coated on the Si (001) wafer by thermal oxidation in situ. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirm that the film shows superior crystalline quality and highly c-axis oriented texture. Neither the Li-enriched LiNbO3 target nor a biased electric field was applied during the deposition. [Copyright &y& Elsevier]

The crystalline GaN films were grown on Si(1 1 1) or using Si3N4 as a buffer layer by hot wall chemical vapor deposition. X-ray diffraction (XRD), photoluminescence (PL) and spreading resistance were sued to characterize the crystalline GaN films with or without a Si3N4 buffer. The XRD indicated that the GaN epilayer was in a wurtzite structure. The PL spectrum at room temperature exhibited a strong emission of the GaN epilayer with a silicon nitride buffer at the wavelength of 365 nm and no yellow luminescence (YL) was present, but the PL spectrum of the GaN directly on silicon was not so strong and yellow luminescence was present. The Si3N4 buffer layer was a high resistivity layer by spreading resistance. This simple but effective technique not only suppressed the YL but also made it possible to grow high-quality GaN on Si substrate. [Copyright &y& Elsevier]