For testing the determination of the reactivity of aluminum powders it is proposed to use the following parameters: temperature of the beginning of oxidation, maximal oxidation rate, degree of transformation (degree of oxidation) of aluminum, relative thermal effect. Parameters for an evaluation of the reactivity of powders were chosen following the analysis of results of a non‐isothermal oxidation of powders of different grain size under conditions of programmed heating (the oxidizer being air). According to the proposed method of testing, the sample of ultrafine powder UFAP‐4 produced by the electrical explosion of wires has the highest reactivity among the studied powders.

This work was aimed at studying the tribological properties of nanolamellar tungsten and molybdenum disulfides produced from nanosized W and Mo nanopowders by self-propagating high-temperature synthesis. The prepared WS2and MoS2powders were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential thermal analysis (DTA). For tribological tests, oil-based lubricants added with nanolamellar tungsten and molybdenum disulfides were prepared. The tribological tests show that the friction coefficient of the nanolamellar powders is lower than that of commercial powder(μmin=0.024and 0.064, resp.). It is also found that the oil-based lubricants with nanolamellar disulfide additives display higher antifriction and antiwear properties compared to commercial powder.

Photoelectrochemical water splitting has emerged as an effective artificial photosynthesis technology to generate clean energy of H from sunlight. The core issue in this reaction system is to develop a highly efficient photoanode with a large fraction of solar light absorption and greater active surface area. In this work, we take advantage of energy band engineering to synthesize (GaN)(ZnO) solid solution nanowires with ZnO contents ranging from 10.3% to 47.6% and corresponding band gap tailoring from 3.08 to 2.77 eV on the basis of the Au-assisted VLS mechanism. The morphology of nanowires directly grown on the conductive substrate facilitates the charge transfer and simultaneously improves the surface reaction sites. As a result, a photocurrent approximately 10 times larger than that for a conventional powder-based photoanode is obtained, which indicates the potential of (GaN)(ZnO) nanowires in the preparation of superior photoanodes for enhanced water splitting. It is anticipated that the water-splitting capability of (GaN)(ZnO) nanowire can be further increased through alignment control for enhanced visible light absorption and reduction of charge transfer resistance.

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Well-aligned GaN nanowires are promising candidates for building high-performance optoelectronic nanodevices. In this work, we demonstrate the epitaxial growth of well-aligned GaN nanowires on a [0001]-oriented sapphire substrate in a simple catalyst-assisted chemical vapor deposition process and their alignment control. It is found that the ammonia flux plays a key role in dominating the initial nucleation of GaN nanocrystals and their orientation. Typically, significant improvement of the GaN nanowire alignment can be realized at a low NH flow rate. X-ray diffraction and cross-sectional scanning electron microscopy studies further verified the preferential orientation of GaN nanowires along the [0001] direction. The growth mechanism of GaN nanowire arrays is also well studied based on cross-sectional high-resolution transmission electron microscopy (HRTEM) characterization and it is observed that GaN nanowires have good epitaxial growth on the sapphire substrate following the crystallographic relationship between (0001)∥(0001) and (101[combining macron]0)∥(112[combining macron]0). Most importantly, periodic misfit dislocations are also experimentally observed in the interface region due to the large lattice mismatch between the GaN nanowire and the sapphire substrate, and the formation of such dislocations will favor the release of structural strain in GaN nanowires. HRTEM analysis also finds the existence of "type I" stacking faults and voids inside the GaN nanowires. Optical investigation suggests that the GaN nanowire arrays have strong emission in the UV range, suggesting their crystalline nature and chemical purity. The achievement of aligned GaN nanowires will further promote the wide applications of GaN nanostructures toward diverse high-performance optoelectronic nanodevices including nano-LEDs, photovoltaic cells, photodetectors etc.