Search

X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) have found coexistence of three structures of GaN: wurtzite, zinc blende, and rocksalt in the samples prepared through benzene thermal process at 280–300 °C under pressure about 5 MPa. Previously, GaN with rocksalt structure only appeared at high pressure more than 37 GPa. HRTEM showed that there was a transitional region between the two cubic phases of GaN with zinc blende and rocksalt. X-ray photoelectron spectra analysis of the sample gave the average composition of Ga0.95N. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this work, we have developed a simple and facile method to synchronously synthesize hollow FeSe2/C nanospheres using the Kirkendall effect. When evaluated as an anode for SIBs, the hollow FeSe2/C nanospheres exhibit a high discharge capacity retention of 474.1 mA h g−1 at 0.05 A g−1 (based on the calculation of FeSe2), which is very close to the theoretical capacity of FeSe2 (∼500 mA h g−1). Meanwhile, hollow FeSe2/C also has a superior rate capability of 364.5 and 316.5 mA h g−1 even at 2.0 and 5.0 A g−1, respectively. The high performance of the hollow FeSe2/C nanospheres can be ascribed to the unique carbon coated hollow nanostructure. [ABSTRACT FROM AUTHOR]

Abstract: Honeycomb-like graphitic macroporous carbon (HGMC) was synthesized by means of pyrolysis of NH4HCO3 using Mg powder as reductant in an autoclave at 550°C. The characterization of structure and morphology was carried out by X-ray diffraction (XRD), Raman spectrum, field-emission scanning electron microscopy (FESEM), and (High-resolution) transmission electron microscope [(HR)TEM]. The results of nitrogen adsorption–desorption indicate that the products are macropore materials with the pore size of 1–3μm, and the Brunauer–Emett–Teller (BET) surface area was 14m2/g. As a typical morphology, the possible growth process of HGMC was also investigated and discussed. The experimental results show that the in situ formed MgO microparticles play a template role during the HGMC formation. [Copyright &y& Elsevier]

Abstract: Cubic phase silicon carbide (3C-SiC) nanowires (labeled as “Sample 1”) with diameters ranging from 10nm to 80nm and lengths up to several micrometers were obtained by using CHI3, Si powder, and metallic Na as reactants at 230°C. In addition, SiC polyhedra (labeled as “Sample 2”) with smooth surfaces and diameters of 2–5μm were obtained by using the different amounts of the same reactants at 500°C. The room-temperature photoluminescence (PL) spectra of Sample 1 and Sample 2 show strong ultraviolet emission peaks centered at 360nm and 354nm, respectively. Thermal gravimetric analysis (TGA) curves reveal that the thermal stability (against air oxidation) of Sample 2 is better than Sample 1. The possible formation mechanisms of the products with distinct dimensions were briefly discussed. [Copyright &y& Elsevier]

Abstract: Silicon carbide (3C-SiC) nanocrystals were prepared starting from SiO2, C2H5OH, and metallic Mg in an autoclave at 200°C. X-ray diffraction patterns of the sample can be indexed as the cubic phase of SiC with the lattice constant a =4.357Å, in good agreement with the reported value (JCPDS card no. 29-1129; a =4.359Å). Transmission electron microscopy images show that the product mainly composed of nanowires with diameters in the range of 10–30nm and lengths up to tens of micrometers; High-resolution transmission electron microscopy images reveal that these 3C-SiC nanowires grow along [111] direction; As polyvinylpyrrolidine was added into the above reactant system, the final products obtained at 180°C were mixed 3C and 2H-SiC flakes. Thermal gravimetric analysis curves reveal that these two samples have thermal stability below 800°C, and room-temperature photoluminescence spectrum of the 3C-SiC sample show a strong emission peak centered at 403nm. [Copyright &y& Elsevier]

Abstract: Hexagonal boron nitride (h-BN) particles including hollow spheres (with a proportion of ~30–40%) and nanotubes (10%) have been synthesized by using sodium fluoroborate and sodium azide at 450°C for 20h. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) studies show that the as-obtained BN hollow particles are crystalline. The total specific surface area of the product calculated from Brunauer–Emmentt–Teller (BET) absorption measurement is 89.79m2/g, indicating that it may be utilized as a promising candidate for hydrogen storage container or catalyst. Thermal gravimetric analysis (TGA) result reveals its excellent thermal stability below 800°C. Its possible growth mechanism and the effects of reaction parameters were also briefly discussed. [Copyright &y& Elsevier]

Abstract: V2O3 and VN nanocrystals have been synthesized by the decomposition of the precursor NH4VO3 and following nitridation in an autoclave with metallic Na flux at 450–600°C. X-ray powder diffraction (XRD) recorded the evolution process of the reaction from precursor NH4VO3 to hexagonal V2O3 and then to NaCl-type VN. In addition, the products were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). [Copyright &y& Elsevier]

Abstract: Stable (α) MnS was synthesized by solvothermal method in different solutions at relatively low temperature (120°C for 12h). The effect of the solvents, surfactant, the ratio of reactant to the surfactant and reaction temperature, time on the morphology and phase of products has been investigated. The morphology of the products was mainly affected by the solvent and the concentration of the surfactant. The as-prepared α-MnS crystals have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–vis absorption and the PL spectrum and X-ray photoelectron spectroscopy (XPS). The proposed formation mechanism of α-MnS is also discussed. [Copyright &y& Elsevier]

Abstract: Single-crystalline nanorods of β-MnO2, α-Mn2O3 and Mn3O4 were successfully synthesized via the heat-treatment of γ-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of γ-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050°C, the precursor γ-MnOOH was first changed to β-MnO2, then to α-Mn2O3 and finally to Mn3O4. When calcined in N2 atmosphere, γ-MnOOH was directly converted into Mn3O4 at as low as 500°C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor γ-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H2O2. [Copyright &y& Elsevier]

Abstract: Nanocrystalline vanadium nitride (VN) was prepared by a direct thermal liquid–solid reaction between vanadium chloride (VCl4) and sodium azide (NaN3) at 600 °C. Characterized by XRD, TEM, XPS and PL, the composition and morphology of the product were confirmed. The possible reaction mechanism was also discussed. [Copyright &y& Elsevier]

Vanadium nitride was synthesized by the reaction of VCl4 and NaNH2 at room temperature. X-ray powder diffraction could be indexed as cubic VN with the lattice constant of a=4.134Å. Transmission electron microscopy image showed particle and hollow sphere morphology. The optical properties of the as-prepared VN were investigated. [Copyright &y& Elsevier]

Nanocrystalline silicon carbide has been prepared via reacting magnesium silicide (Mg2Si) with carbon tetrachloride (CCl4) in an autoclave at 450–600°C. X-ray diffraction patterns of the products can be indexed as the cubic cell of SiC with the lattice constant, a=4.352 Å, in good agreement with a=4.349 Å (JCPDS card No. 75-0254). The transmission electron microscopy images show that the sample mainly consists of nanoparticles with an average size from 30 to 80 nm co-existing with a small fraction of nanorods and nanowires. Typically the nanorods range from 20 to 40 nm in diameter and the nanowires have diameters of 20 nm and lengths up to 10 μm. The Raman spectrum shows a characteristic sharp peak at 790 cm-1. X-ray photoelectron spectra (XPS) gives an atomic ratio of Si to C as 1.08:1.00 from the quantification of the peak intensities. Photoluminescence spectrum reveals that the SiC sample emits ultraviolet light of 328 nm. A possible mechanism and the influence of temperature on the formation of crystalline SiC are proposed. [Copyright &y& Elsevier]

Ultrafine magnesium diboride (MgB2) powders were successfully synthesized at 600 °C through a solid-state reaction. The synthesis was carried out in an autoclave by using MgCl2 and NaBH4 as the reactants. The X-ray powder diffraction pattern indicates the formation of hexagonal MgB2. Transmission electron microscopy image shows that typical MgB2 crystallites are composed of ultrafine particles with an average size of 300 nm. The superconducting transition of the MgB2 sample occurs at 39 K. [Copyright &y& Elsevier]

Nanocrystalline TiN, VN and CrN have been synthesized by a thermal nitridation reaction between the corresponding metal powder and NH4Cl at 600 °C in an autoclave. X-ray powders diffraction (XRD) indicated that these nanocystallites had a NaCl-type structure with lattice parameters: a=4.236 Å for TiN, 4.133 Å for VN, 4.145 Å for CrN. Transmission electron microscopy (TEM) showed these products consisted of cubic nanocrystals. X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) techniques revealed that all the products were almost pure nitrides. [Copyright &y& Elsevier]

Boron nitride hollow spheres were synthesized by the reaction of BBr3 and NaNH2 at room temperature; X-ray powder diffraction pattern could be indexed as hexagonal BN with the lattice constants of a=2.482 and c=6.701 A˚; high-resolution transmission electron microscopy image showed the hollow spheres consisted of BN nanoparticles, with diameter between 80 and 300 nm; a possible formation mechanism of BN hollow spheres was discussed. [Copyright &y& Elsevier]

In this paper, we report the low-temperature synthesis of metal tungstate, MWO4 (M=Ca, Sr, Ba, Cd, Zn, Pb) nanocrystallites. By reaction between metal chloride and sodium tungstate in ethylene glycol at 180 °C for 10 h, well-crystallized tungstate particles were successfully obtained. Characterization by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) shows that the product powders consist of nanosize particles. Photoluminescence measurement reveals that the as-obtained CaWO4, CdWO4, and PbWO4 show excitonic peaks at about 430, 500 and 500 nm, respectively. The solvent and reaction conditions are important in the formation of the products. [Copyright &y& Elsevier]

α-silicon nitride nanorods have been synthesized through solid-state reduction–nitridation of silica using NaNH2 as both a reductant and a nitriding reagent. X-ray powder diffraction patterns show that the products have a hexagonal phase with lattice parameters a=7.767 Å and c=5.630 Å. Transmission electron microscopy reveals that the as-synthesized products are pure nanorods with an average size about 30 nm in diameter and 400 nm in length. X-ray photoelectron spectra indicate that the molar ratio of Si/N is 2.988:4. Fourier-transform infrared spectrum yields a strong Si–N absorption at 926 cm−1 that may be a red shift due to size effect. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline boron nitride (BN) was prepared by the reaction of BBr3 and Mg3N2 at 400 °C. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal BN with the lattice constants of a=2.504 and c=6.671 Å. The transmission electron microscopy (TEM) images showed whisker-like and flake-like morphology. The product was also characterized by X-ray photoelectron spectrum (XPS) and Fourier transformation infrared spectroscopy (FTIR). [Copyright &y& Elsevier]

Zirconium phosphide (ZrP) has been synthesized via a sodium co reduction of ZrCl4 and PCl3 at 350 °C. The X-ray powder diffraction (XRD) pattern can be indexed as cubic ZrP with the lattice constant a=5.25 Å. The transmission electron microscopy (TEM) image indicates the product has dendritic morphology and hexagonal flakes. [Copyright &y& Elsevier]

The direct polyol method is used to prepare silver bismuth sulfide AgBiS2 nanorods. X-ray powder diffraction patterns indicate that AgBiS2 is cubic with a cell constant a=5.651 A˚. Transmission electron microscopy images reveal that the product consists of uniform rod-like crystals with diameters of about 40 nm and lengths up to 10 μm. A possible formation mechanism of silver bismuth sulfide is proposed. [Copyright &y& Elsevier]