NiO nanoplatelet-based materials with different dimensionality are synthesized by a one-step hydrothermal route at 120 °C for 4 h. The morphologies and structure of the obtained NiO nanoplatelets grown on Ni foam and NiO microspheres composed of nanoplatelets are characterized. The results show that the former has a length of 5–10 μm and a uniform thickness of ∼100 nm, while the latter has a diameter of 5–10 μm. Their electrochemical properties as anode materials for lithium-ion batteries are evaluated and compared. The discharge capacities of NiO nanoplatelet electrode are 663, 516, 370, 258, and 169 mAh g−1 at current densities of 250, 500, 1000, 2500, and 5000 mA g−1, respectively. Such a lithium storage capability is much higher than that of the NiO microsphere electrode. The reasons for the enhanced electrochemical performance of the nanoplatelet electrode were investigated, which suggested that more active sites for electrochemical reactions and faster ion/electron transfer realized on nanoplatelets are facilitating lithium storage.

To selectively detect Cu2+ ions is very important for controlling daily intake of Cu2+ ions and monitoring numerous biological processes. Fluorescence spectroscopic technique is a useful one for detection of copper ions. Previous methods always involve the use of metal Cd-based quantum dots (QDs), which suffer to the photobleaching and subsequent release of toxic metal ions. Herein, a simple method has been developed to detect Cu2+ ions by using pristine graphene QDs. Graphene QDs are synthesized by chemical oxidation of pitch graphite fibers. Our results indicate the photoluminescence (PL) of as-synthesized graphene QDs could be quenched by a group of metal ions while adding biothiol cysteine can only cause the significant recovery of the PL of graphene QDs quenched by Cu2+ ions. Our approach provides an easy and environmental friendly method for detection of Cu2+ ions and has the potential for future practical applications.

Titanium dioxide (TiO2), a widely used inorganic semiconductor owing to its superb photoelectric properties, has frequently been fabricated into composites to reduce its relatively large band gap and overcome its limited visible light absorption. In this article, a “layer-by-layer” method has been developed to prepare the composite structure of nitrogen (N)-doped graphene quantum dots (GQDs)-sensitized TiO2 nanofibers. The as-prepared structure shows considerable luminescence and exhibits excellent photoelectric properties. Various factors including the crystalline phase of TiO2, amount of N in GQDs, and irradiation wavelength were investigated to find the optimal conditions for enhanced photoelectric activity. It is demonstrated that the combination of highest N amount GQDs with TiO2 nanofibers of mixed phases (750 °C-sintered TiO2 nanofibers) possess the best photoelectric properties. The enhancement of properties using TiO2 nanofibers with mixed phases mainly contributes to the transfer of electrons between conduction bands of different phases in TiO2 and the distinctive photoluminescence (PL) property of N-GQDs. Furthermore, this enhancement can be achieved in most areas of the visible light range. The general mechanism of the electron generation and transfer of the structure is based on the normal PL and upconversion PL property of N-GQDs which serve as the sensitizer. We consider it a feasible method to improve the photoelectric conversion efficiency in photovoltaic devices.

Au nanoparticles (Au NPs) have attracted much interest owing to their unique optical properties. In this paper, a facile process has been successfully developed to synthesize the SiO2/Au hybrid microspheres with a diameter of 200 nm via the galvanic replacement of SiO2/Ag hybrid microspheres and chlorauric acid (HAuCl4) solution. The as-prepared products were investigated by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM, JEOL-6700F), and transmission electron microscopy (TEM, JEOL 3010), respectively. As expected, the as-prepared SiO2/Au hybrid microspheres show strong chemical stability and superior catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The SiO2/Au hybrid microspheres would be found widely used in wastewater treatment, catalytic reaction, bacteriostatic and bactericidal applications.

Tungsten oxide (WO3) nanostructures receive sustained interest for a wide variety of applications, and especially for its usage as a photocatalyst. It is therefore important to find suitable methods allowing for its easy and inexpensive large scale production. Tungstite (WO3·H2O) nanoparticles were synthesized using a simple and inexpensive low temperature and low pressure hydrothermal (HT) method. The precursor solution used for the HT process was prepared by adding hydrochloric acid to diluted sodium tungstate solutions (Na2WO4·2H2O) at temperatures below 5 °C and then dissolved using oxalic acid. This HT process yielded tungstite (WO3·H2O) nanoparticles with the orthorhombic structure. A heat treatment at temperatures at or above 300 °C resulted in a phase transformation to monoclinic WO3, while preserving the nanoparticles morphology. The production of WO3 nanoparticles using this method is therefore a three step process: protonation of tungstate ions, crystallization of tungstite, and phase transformation to WO3. Furthermore, this process can be tailored. For example, we show that WO3 can be doped with cesium and that nanorods can also be obtained. The products were characterized using powder x-ray diffraction, transmission electron microscopy (including electron energy-loss spectroscopy and electron diffraction), and x-ray photoelectron spectroscopy.

The submicrometer Ni cones have been successfully prepared through a simple solvothermal method in glycerol. The as-prepared products were extensively characterized by x-ray diffraction, field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The effects of the volume ratios of glycerol to water, and the concentration of alkali on morphologies of Ni samples were investigated. The electromagnetic wave absorption properties of Ni cones were evaluated based on the relative complex permeability (μr) and permittivity (εr). A minimum reflection loss (RL) of −41.6 dB was observed at 4.7 GHz with the thickness of 3.8 mm and the RL values below −10 dB were obtained in the range of 3.9–15.0 GHz with the corresponding thickness of 1.8–3.8 mm. The excellent wave absorption properties of the obtained products are due to the synergic effect of dielectric loss and magnetic loss, geometry effect and unique morphology.

Oxide-dispersion-strengthened (ODS) ferritic alloys are fascinating materials for future high temperature energy production technologies. MgAl2O4 ODS alloy incorporating nanoscale oxide particles were produced by mechanical milling (MM) followed by hot isostatic pressing (HIP). The MgAl2O4 nanoscale oxide particles were formed during the HIP process by the addition of MgO and Al2O3 to the Fe–Cr matrix. Microstructural evolution of ODS alloys was structurally characterized at each step of the elaboration processes by means of scanning electron microscope (SEM), transmission electron microscope (TEM), and x-ray diffraction (XRD). The observations of structure of the mixed powders in ODS alloys after MM indicated that the initial powders, coupled with the original MgO and Al2O3 powders, got fractured by severe plastic deformation and ultrafine bcc grains (∼17 nm) of the matrix and amorphous phase composed of Mg, Al, and O were formed during MM. The main driving force for the formation of amorphous phase comes from the increase of volume fraction of bcc Fe grain boundary and the increase of interfacial energy due to the decrease in the size of MgO and Al2O3 powders. The MgAl2O4 nanoscale oxide particles formed at 1173 K which was far below the traditional sintering temperature of the raw material. And the structures of MgAl2O4 nanoscale oxide particles were observed by TEM.

The effects of magnetic field on the austenite formation and grain size were studied by applying high magnetic field during the different stages. Optical microscopy and scanning electron microscopy were used to characterize the microstructure evolution for the samples treated without and with magnetic field. Magnetic field dramatically retards the austenite formation kinetics including pearlite to austenite transformation and cementite dissolution. The austenite grain size is enlarged by the magnetic field applied during austenite formation and not affected by the magnetic field applied only during austenite grain coarsening. The austenite treated with magnetic field during the whole austenitization process also has a larger grain size. The changes in austenite formation kinetics and grain size are related to lower nucleation rate of austenite caused by magnetic field.

In situ transmission electron microscopy (TEM) analysis shows that submicrometer grains formed by ultrasonic impact treatment (UIT) of sensitized 5456-H116 Al–Mg alloy products are thermally stable up to ∼300 °C which is consistent with previous research on annealing of heavily deformed Al–Mg. Grain growth occurs above 300 °C with significant growth at ∼400 °C. Grain growth continued upon heating to 450 °C; the grain size did not significantly increase when the temperature was held at 450 °C long term. In situ TEM revealed a duplex microstructure that was not fully recrystallized. The activation energy for grain growth was determined to be ∼32 kJ/mol. The submicrometer grains produced by UIT offer improved resistance to fatigue and corrosion. The majority of sensitized 5456-H116 failures are sensitive to the material's surface properties and operational service temperature; the stability of the submicrometer grains in the UIT Al–Mg makes them more stable in practical operations where increase in the material temperature is an issue.

Binary interdiffusion data as function of composition in the Mg–{Ce, Nd, Zn} and Zn–{Ce, Nd} systems were obtained experimentally using solid–solid diffusion couples. For the studied systems, all intermetallic compounds were produced, based on the equilibrium phase diagrams, eliminating the problem of missing compounds in the diffusion couples found in the literature. The composition profiles were obtained using wavelength dispersive spectroscopy line-scans across diffusion couples. The composition-dependent diffusion coefficient at each interface was determined using Boltzmann–Matano analysis. For the available literature data for some of the compounds in the Mg–{Ce, Nd, Zn} systems, the calculated interdiffusion coefficients were in good agreement. No diffusion data regarding Zn–{Ce, Nd} systems could be found in the literature. The activation energy and the preexponential factor of the growth of the Mg–{Ce, Nd, Zn} compounds were determined using Arrhenius equation. The activation energies of the growth of the Mg–Ce compounds showed relatively higher values than those of Mg–Nd and Mg–Zn compounds.

Aluminum metal matrix hybrid composites were synthesized through powder metallurgy route from ball milled powders to yield the compositions: Al + 0% TiO2, Al + 2.5% TiO2, Al + 2.5% TiO2 + 2% Gr, and Al + 2.5% TiO2 + 4% Gr. The densification and deformation properties of sintered Al–TiO2–Gr composites during cold upsetting were investigated experimentally. The powder preforms are compacted using suitable punch and die in 40 kN hydraulic press and the initial percentage theoretical density was maintained as 85%. Sintering was done in an electric muffle furnace at the temperature of 590 °C for a period of 3 h. The sintered preforms were subjected to incremental compressive loading of 10 kN until cracks were found at the free surface. The true axial stress (σz), true hoop stress (σθ), true hydrostatic stress (σm), and true effective stress (σeff) were calculated for all the preforms and all these stresses are correlated with the true axial strain (εz). The densification behaviors of the composites were studied against true axial strain (εz) and lateral strain. Better densification and deformation property were obtained for pure aluminum preforms compared with other composite preforms. Addition of TiO2 to the pure Al and Gr reinforcements increases the strength coefficient of the Al–TiO2 composite.