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Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method at temperatures ranging from 700°C to 850°C in a SHS furnace using Mg, B2O3 and KBH4 as raw materials. Samples were characterized by X-ray powder diffraction (XRD), Laser particle size analyzer, Fourier transform infrared spectra (FTIR), X-ray energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission TEM (HRTEM). The boron powders demonstrated an average particle size of 50nm with a purity of 95.64wt.%. The diluter KBH4 played an important role in the active dilution synthesis of amorphous nano-sized boron powders. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed. [ABSTRACT FROM AUTHOR]

A low temperature and high pressure synthetic route assistedwithball milling has been established to prepare high quality orientatedexplosion phase boron nitride (E-BN) octahedron crystals using H3BO3, iron powders, NH4Cl, and Mg asstarting materials. FSEM, TEM, HRTEM, SAED, XRD, Raman, FTIR, andXPS were employed for characterization of the morphology and structureof as-synthesized E-BN samples. The E-BN was identified as the face-centeredcubic structure with a lattice parameter of 8.245 Å. The typicalparticle sizes were mainly in the range of 30–120 nm. A UVspectrum indicated that the product has an obvious absorption band(5.61 eV). Photoluminescence spectra revealed that it has a dominantultraviolet emission peak at 383 nm. The possible chemical reactionsas well as the proposed mechanism of the growth of E-BN octahedroncrystals were also discussed. [ABSTRACT FROM AUTHOR]

Abstract: High purity quasi-octahedral polycrystalline explosion phase boron nitride (e-BN) submicron-powders were synthesized in an autoclave at 600°C for 6h using Mg, FeB1.3 and NH4Cl as the raw materials. Samples were characterized by SEM, FSEM, EDX, TEM, HRTEM, SAED, X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The as-synthesized e-BN powders demonstrated a face-centered cubic structure with lattice parameter of 8.300Å. Besides the e-BN samples presented a quasi-octahedral morphology with an average diameter of 0.8μm. The effects of time, temperature, raw materials and possible catalytic reaction mechanism of the growth of quasi-octahedral polycrystalline e-BN were also discussed. [Copyright &y& Elsevier]

Abstract: A new method for synthesis of nanocrystalline titanium nitride was developed through the reaction of titanium oxide and sodium amide at 500–600 °C for 12 h in an autoclave. X-ray diffraction (XRD) and electron diffraction (SAED) results indicated the product had a cubic phase with lattice parameter a =4.242 Å. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed that the particle sizes were 10 to 40 nm. Quantitative analysis using X-ray photoelectron spectrum (XPS) showed the atomic ratio Ti:N was 1.03:1. [Copyright &y& Elsevier]

Abstract: Nanocrystalline boron nitride (BN) was prepared by the reaction of BBr3 and NaN3 at 350°C. The morphologies of particles, needles, flakes and solid balls were controlled by solvothermal growth using benzene as solvent. X-ray powder diffraction patterns can be indexed as hexagonal BN with the lattice constants of a=2.502 and c=6.734Å. The products were also characterized by X-ray photoelectron spectrum, fourier transformation infrared spectroscopy, transmission electron microscopy and electron diffraction. [Copyright &y& Elsevier]

Titanium silicides were synthesized by co-reducing silicon tetrachloride and titanium tetrachloride with different metal reductants (Na, Mg, Zn and Al) in an autoclave at 650 °C. The X-ray diffraction patterns indicated that the obtained titanium silicides could adopt different structures. The orthorhombic titanium disilicide was obtained when the reductant was metallic sodium. However, the hexagonal titanium silicide (Ti5Si3) was obtained when using Mg, Zn and Al. Transmission electron microscope images showed that the average particle sizes of the samples were about 60, 40, 30 and 25 nm in diameters, respectively. It is suggested that the different reaction activities of the reductants resulted in the different titanium silicides. [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]

Nanocrystalline chromium disilicide was synthesized by co-reducing anhydrous chromium trichloride and sodium fluorosilicate with metallic potassium at 650 °C in an autoclave. X-ray powder diffraction pattern indicated that the product was hexagonal CrSi2. Transmission electron microscope images showed that the sample consisted of particles with the diameters of 20–50 nm and an average diameter of about 35 nm. TGA and DTA indicated that the oxidation of CrSi2 began to proceed at 700 °C in air, and only about 8.6 wt.% of the sample was oxidized in the surfaces of the particles below 1000 °C. It had high thermal oxidation stability due to the formed protective layer. [Copyright &y& Elsevier]

Chromium silicide (Cr3Si) nanorods were successfully synthesized using anhydrous chromium trichloride and silicon tetrachloride as starting materials via a co-reduction route at 600 °C in an autoclave. X-ray powder diffraction pattern indicated that the product was cubic Cr3Si (a=4.555 Å). Transmission electron microscope images indicated that the sample consisted of single-crystalline nanorods with a diameter of 40–80 nm, an average length of about 600 nm and a maximum length of about 1.0 μm. The oxidation of Cr3Si began to proceed at the temperature of 650 °C in air, but the product had a high thermal oxidation stability below 1000 °C due to the formed protective layer. [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]

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]

Nano-crystalline vanadium disilicide was successfully synthesized using vanadium tetrachloride and silicon as starting materials via reduction–silication route at 650 °C in the molten salt solution of magnesium chloride and sodium chloride in an autoclave. X-ray powder diffraction patterns indicated that the product was hexagonal VSi2 (a=4.572 A˚, c=6.372 A˚). Transmission electron microscopy images showed that the particle size of the product was in the range of 40–60 nm in diameter. There was a strong absorption peak at 271 nm in the UV-Vis absorption spectra. The oxidation of nano-crystalline VSi2 began to proceed at the temperature of 400 °C in air. But the product had high thermal oxidation stability below 1000 °C. It can be used as an antioxidation coating material. [Copyright &y& Elsevier]

Mn5Si3 nanocages and nanotubes were successfully synthesized by molten salt flux reaction at 650 °C. The samples were characterized with X-ray powder diffraction and transmission electron microscopy. The influence of the reactants molar ratio of MnCl2 to Mg2Si and reaction temperature on the phases and morphologies of the products were discussed. The possible mechanism of forming Mn5Si3 nanocages and nanotubes is discussed. [Copyright &y& Elsevier]

Nanocrystalline hafnium diboride (HfB2) has been prepared by the reaction of HfCl4 with NaBH4 at 600 °C in an autoclave. The X-ray powder diffraction (XRD) pattern can be indexed as hexagonal HfB2 with the lattice constants of a=3.146 and c=3.456 A˚. The transmission electron microscopy (TEM) image shows a particle morphology with an average size of 25 nm. The selected area electron diffraction (SAED) pattern confirms the presence of hexagonal HfB2. The oxidation behavior of HfB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). [Copyright &y& Elsevier]

Nanocrystalline titanium diboride (TiB2) has been prepared by the reaction of TiCl4 with NaBH4 in the temperature range of 500–700 °C in an autoclave. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal TiB2 with the lattice constants of a=3.032 and c=3.229 A˚. Transmission electron microscopy (TEM) image shows particle morphology, with average size of 15 nm for the powder obtained at 600 °C. Selected area electron diffraction (SAED) pattern confirms the prepared hexagonal TiB2. The oxidation behavior of TiB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). [Copyright &y& Elsevier]

Nanocrystalline boron nitride (BN) with needle-like and hollow spherical morphology has been synthesized by nitriding of MgB2 with NH4Cl and NH4Cl–NaN3, respectively. The amount of NaN3 has an obvious effect on the size of the hollow spheres. The samples were characterized by X-ray powder diffraction, Fourier transformation infrared spectroscopy, X-ray photoelectron spectra, and transmission electron microscopy. The possible mechanism of morphology control is also discussed. [Copyright &y& Elsevier]

Chromium boride (CrB) nanorods were synthesized via a reduction–boronation route at 650 °C in molten salt in an autoclave. The X-ray diffraction pattern of the product was indexed as the orthorhombic CrB. Transmission electron microscope images indicated that the sample consisted of single-crystalline nanorods with the diameter of 10–30 nm and a maximum length of 1.5 μm. The PL spectra showed the ultraviolet light emission at 340 nm. The thermogravimetric analysis showed that the product also had very good anti-oxidation properties below 630 °C. A possible growth mechanism was proposed. [Copyright &y& Elsevier]

Molybdenum carbide (Mo2C) has been synthesized via a sodium co-reduction of molybdenum pentachloride (MoCl5) and carbon tetrabromide (CBr4) in benzene at 350 °C for 12 h. X-ray diffraction (XRD) pattern indicated that the product was mainly hexagonal Mo2C with a small amount of cubic Mo2C. The lattice constants of the hexagonal Mo2C were a=3.009 and c=4.736 A˚. Transmission electron microscopy (TEM) study showed that the product consisted of slightly conglomerated particles of about 30 nm in size. [Copyright &y& Elsevier]

Powdered zirconium nitride (ZrN) has been prepared via a benzene-thermal synthesis via the reaction of anhydrous zirconium tetrachloride (ZrCl4) and lithium nitride (Li3N) at a temperature of 380–400 °C. The product was analyzed by X-ray photoelectron spectroscopy (XPS), and the results show the mole ratio of Zr/N is 1:0.87. X-ray diffraction (XRD) pattern can be indexed to the cubic cell of ZrN with the lattice constant a=4.5675 A˚. Transmission electron microscope (TEM) images indicate that average particle size is about 180 nm in diameter. [Copyright &y& Elsevier]

The synthesis and growth of hexagonal boron-nitride crystallites at low temperature were investigated by carrying out in a lithium bromide (LiBr) melt in 600°–700°C. Transmission electron microscopy study showed that the product obtained at 650°C was composed of two-dimensional plates having an average thickness of about 80 nm and widths from about 400 nm to several micrometers. The molten salt was found to have a strong effect on the crystal growth. The morphology of the crystallites changed from spherical particles to two-dimensional plates when LiBr was used as a crystallization medium. Products were also characterized by X-ray powder diffractions, Fourier Transformed infrared, FESEM/energy dispersive X-ray spectroscopy, and selected area electron diffraction. Possible formation mechanism was also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline hexagonal boron nitride (h-BN) nanoropes with diameters of 60–150 nm and with lengths up to several micrometers have been successfully synthesized by reacting KBH4 and NH4Cl using CoCl2 as the catalyst. The products were characterized by X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), energy dispersive spectrum (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cobalt chloride (CoCl2) played a key role in the formation of the rope-like nanostructure. [Copyright &y& Elsevier]

Abstract: Nanocrystalline niobium carbide (NbC) was successfully synthesized at 550 °C by using a co-reduction route. X-ray powder diffraction and X-ray photoelectron spectra confirmed the formation of cubic NbC. Transmission electron microscopy image revealed that typical NbC crystallites are composed of uniform particles having an average size of about 30 nm. Thermogravimetric analysis showed that the oxidation of nanocrystalline NbC occurred between 350 and 550 °C. [Copyright &y& Elsevier]

Abstract: Nanocrystalline neodymium disilicide was synthesized by co-reducing anhydrous neodymium trichloride and sodium fluorosilicate with metallic sodium in an autoclave at 650°C. The as-prepared product was characterized and studied by X-ray powder diffraction, transmission electron microscopy and thermogravimetric analysis. [Copyright &y& Elsevier]

Nanocrystalline boron nitride (BN) with needle-like morphology has been synthesized by reacting amorphous B powder with NaN3. The samples were characterized by X-ray powder diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), X-ray photoelectron spectra (XPS) and transmission electron microscopy (TEM). [Copyright &y& Elsevier]

Nanocrystalline vanadium diboride (VB2) were successfully synthesized at 650 °C through a solid state reaction. The synthesis was carried out by reacting VCl4 with NaBH4 and Mg in an autoclave. The X-ray powder diffraction pattern indicates the formation of hexagonal VB2. An atomic ratio of B to V of 2.11:1.0 is determined from X-ray photoelectron spectra. Transmission electron microscopy image shows that typical VB2 crystallites are composed of uniform particles with the grain size in the range of 50–100 nm. [Copyright &y& Elsevier]

Graphite sheets have been synthesized by using hexachlorobutadiene (C4Cl6) and Na as reactants at 500 °C in an autoclave. Transmission electron microscopy images show that the average dimension of graphite sheets is about 8 × 15 μm and the thickness ranges 20–50 nm. The possible reaction mechanism is discussed. [Copyright &y& Elsevier]

Amorphous phosphorus nitride (P3N5) hollow spheres were synthesized via reacting PCl3 with NaNH2 at room temperature. Transmission electron microscopy (TEM) images showed the hollow spheres with a diameter of 80–150 nm. X-ray photoelectron spectra (XPS) were used to determine the molar ratio of 1:1.60 for P:N. The optical properties of the as-prepared P3N5 were investigated. [Copyright &y& Elsevier]

Nanocrystalline titanium diboride (TiB2) has been prepared through a reduction–boronation route by using Ti powders and BBr3 as titanium and boron sources, and metallic sodium as reductant at 400 °C. X-ray powder diffraction (XRD) pattern can be indexed as hexagonal TiB2 with the lattice constants of a=3.028 and c=3.223 A˚. Transmission electron microscopy images show particle morphology with average size of 15 nm. Selected area electron diffraction patterns confirm the preparation of the hexagonal TiB2. [Copyright &y& Elsevier]

Nanocrystalline ZrB2 has been prepared by the reaction of ZrCl4 with NaBH4 in the temperature range of 500–700 °C. The microstructure of the powders consists of uniform particles about 20 nm in size. The UV–vis absorption spectra and thermal oxidation behavior of the products are studied. [Copyright &y& Elsevier]

Nanocrystalline titanium diboride (TiB2) powders were successfully synthesized at 650 °C by using TiCl4, Mg and MgB2 as the reactants. Transmission electron microscopy images show that typical TiB2 crystallites are composed of uniform particles with the average grain size of about 40 nm. [Copyright &y& Elsevier]

B4C ultrafine powders were successfully synthesized at 450 °C through a new co-reduction route. The synthesis was carried out in an autoclave by using BBr3 and CCl4 as the reactants and metallic Na as the co-reductant. The X-ray powder diffraction pattern and Raman spectra indicate the formation of B4C. An atomic ratio of B to C of 4.09:1.0 was determined from X-ray photoelectron spectra. Transmission electron microscopy images shows that typical B4C crystallites are composed of uniform ultrafine spherical and rod-like particles. [Copyright &y& Elsevier]

Titanium diboride (TiB2) has been synthesized via a benzene-thermal reaction of metallic sodium with amorphous boron powder and titanium tetrachloride at 400 °C in an autoclave; the temperature was much lower than that of traditional methods. The X-ray diffraction (XRD) pattern can be indexed with the hexagonal cell of TiB2 and the lattice constants a=3.027 and c=3.228 A˚. X-ray photoelectron spectroscopy (XPS) results show the mole ratio of Ti:B as 1:1.766. Transmission electron microscope (TEM) images indicate that the average particle size is in the range of 15–40 nm in diameter. [Copyright &y& Elsevier]

A novel boron nitride nanotube‐supported nano‐sheets one‐dimensional hierarchical structures (BNNT‐BNNS) were efficiently prepared via a ball milling assisting chemical vapor deposition method. X‐ray powder diffraction (XRD), fourier transform infrared spectrometer (FTIR), Raman, field scanning electron microscopy (FSEM), energy dispersive spectroscopy (EDX), transmission electron microscopy (TEM) and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the as‐synthesized samples. The samples presented a length of more than 20 μm and wide diameter ranges from 20 nm to 600 nm. Abundant nano‐sheets grew in random directions and intertwined closely on the surface of the one‐dimensional structures. Every nano‐sheet was transparent and demonstrated a thickness of less than 10 nm with irregular size and shape. Ultraviolet‐visible (UV‐vis) and photoluminescence (PL) results indicated that the band gap was 5.71 eV and the maximum fluorescence emission peak was located at 368 nm. In addition, it was worth noting that the BNNT‐BNNS hierarchical structures also presented excellent adsorption property for methylene blue (MB). When the adsorption time was 5 min, MB could be removed by 75.2% from water solution. The adsorption rate could increase to 97.3% when the adsorption time was 115 min. Finally, the possible chemical reactions and the corresponding catalytic cracking growth mechanism of the special hierarchical structures also were investigated carefully. One‐dimensional boron nitride nanotube‐supported nano‐sheets hierarchical structures (BNNT‐BNNS) were prepared by a ball milling assisting chemical vapor deposition method. The band gap was 5.71 eV and the maximum fluorescence emission peak was located at 368 nm. MB could be removed by 75.2% when the adsorption time was 5 min. Possible chemical reactions and catalytic cracking growth mechanism of the samples were also proposed. [ABSTRACT FROM AUTHOR]

Presents information on solvothermal synthesis of titanium phosphides. Group IV transition metal phosphides have a number of phases with different stoichiometries. Among these, titanium phosphide has a high thermal stability, inertness to chemical attack, high thermal and electrical conductivity, high hardness and strength. In the solvothermal process, nascent phosphorus and titanium were generated by reducing titanium chloride and combined forming titanium phosphides.

High quality BNNTs have been prepared by a combined chemical vapor deposition (CVD) and self-propagation high-temperature synthesis (SHS) method using industrial glass fabrics as the growth catalyst and the products collecting substrate. The products and the glass fabrics were characterized by SEM, TEM, HRTEM, SAED, XPS, EDX, XRD, FTIR and Raman spectroscopy. The BNNTs reveal an average length of about 10 μm and a fairly broad diameter distribution from tens to hundreds of nanometers. The possible chemical reactions and a novel self-cracking vapor–liquid–solid (VLS) growth mechanism were also proposed to appropriately explain the formation processes of BNNTs. [ABSTRACT FROM AUTHOR]

Abstract: Large quantities of boron nitride (BN) nanotubes were synthesized by annealing a catalytic boron-containing porous precursor in flowing NH3 gas at 1180°C. The porous precursor was prepared by self-propagation high-temperature synthesis (SHS) method at 800°C using Mg, B2O3 and amorphous boron powder (α-B) as the starting materials. The porous precursor played an important role in large quantities synthesis of BN nanotubes. The as-synthesized product was characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Raman, Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HRTEM). Characterization results indicated that the BN nanotubes displayed wave-like inner structures with diameters in the range of 50–300nm and average lengths of more than 10μm. The possible growth mechanism of the BN nanotubes was also discussed. [Copyright &y& Elsevier]

Abstract: The high-pure bamboo-like boron nitride (BN) nanotubes with high yield were synthesized via an effective chemical vapor deposition method by annealing porous precursor under NH3 atmosphere at 1150°C. The porous precursor was readily prepared by self-propagation high temperature synthesis (SHS) method. The as-synthesized BN nanotubes were characterized by SEM, TEM, HRTEM, XRD, Raman and FTIR spectroscopy. The results indicate these nanotubes have bamboo-like structures with an average diameter of about 90nm and length of more than 10μm. Nanotube content is estimated as approximately 90wt.% according to the statistical analyses by SEM and TEM. Moreover, the reaction mechanism for the as-synthesized BN nanotubes is proposed. [Copyright &y& Elsevier]

Abstract: Fe-filled boron nitride (BN) nanotubes with high purity and good yield were conveniently synthesized by a novel ball-milling and self-propagation high-temperature synthesis (SHS) method at a low temperature (700°C). The as-prepared product was characterized by XRD, FTIR, SEM, TEM and HRTEM. The results of XRD, FTIR and HRTEM reflect that the product is a hexagonal BN nanotube filled with Fe. The results of SEM and TEM reveal that the Fe-filled BN nanotubes have a diameter of 20–150nm with the wall-thickness of about 20nm and the length of more than 5μm. The possible growth mechanism was also discussed. [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]

Glass fabrics were used to fabricate boron nitride nanotubes (BNNTs) with a broad diameter range through a combined chemical vapor deposition and self-propagation high-temperature synthesis (CVD-SHS) method at different holding times (0min, 30min, 90min, 180min and 360min). SEM characterization has been employed to investigate the macro and micro structure/morphology changes of the glass fabrics and BNNTs in detail. SEM image analysis has provided direct experimental evidences for the rationality of the optimized self-cracking catalyst VLS growth mechanism, including the transformation situations of the glass fabrics and the BNNTs growth processes respectively. This paper was the further research and compensation for the theory and experiment deficiencies in the new preparation method of BNNTs reported in our previous work. In addition, it is likely that the distinctive self-cracking catalyst VLS growth mechanism could provide a new idea to preparation of other inorganic functional nano-materials using similar one-dimensional raw materials as growth templates and catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Four types of BN nanotubes are selectively synthesized by annealing porous precursor in flowing NH3 and NH3/H2 atmosphere at temperature ranging from 1000 to 1200°C in a vertical furnace. The as-synthesized BN nanotubes, including cylinder, wave-like, bamboo-like and bubble-chain, are characterized by XRD, FTIR, Raman, SEM, TEM and HRTEM. Three phenomenological growth models are proposed to interpret growth scenario and structure features of the four types of BN nanotubes. Selectivity of nanotubes formation is estimated as approximately 80–95%. The precursor containing B, Mg, Fe and O prepared by self-propagation high-temperature synthesis (SHS) method plays a key role in selective synthesis of the as-synthesized BN nanotubes. Chemical reactions are also 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: Nanocrystalline Mo2C powders were successfully synthesized at 500°C by reacting molybdenum chloride (MoCl5) with C (graphite or carbon nanotube) in metallic sodium medium. X-ray powder diffractometer (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS) and surface area analyzer (BET method) were used to characterize the samples. Experiments reveal that the carbon source used for the carbide synthesis has a great effect on the particle size and the surface area of the samples. When micro-sized graphite was used as C source the obtained nanocrystalline Mo2C powder consists of particles of 30∼100nm, with a surface area of 2.311m2/g. When carbon nanotubes were used as C source, the as-synthesized Mo2C sample is composed of particles of 20∼50nm, with a surface area of 23.458m2/g, which is an order of magnitude larger than that of the carbide prepared from the graphite. [Copyright &y& Elsevier]

Abstract: In this Letter, we report the synthesis of hexagonal crystalline BN powders with novel cage-like structures from a single-source precursor NH4BF4 at 400–600 °C for 12 h. The obtained samples are characterized by XRD, XPS, TEM and HRTEM. Experiments reveal that the as-prepared BN powders exist in multiwall nanocages with dimensions from about 20 to 200 nm and have very good anti-oxidation properties at high temperatures. [Copyright &y& Elsevier]

Nanocrystalline gallium phosphide (GaP) has been prepared through a reduction–phosphidation by using Ga, PCl3 as gallium and phosphorus sources and metallic sodium as reductant at 350°C. The XRD pattern can be indexed as cublic GaP with the lattice constant of a=5.446Å. The TEM image shows particle-like polycrystals and flake-like single crystals. The PL spectrum exhibits one peak at 330nm for the as-prepared nanocrystalline GaP. [Copyright &y& Elsevier]

Thorn-like polycrystalline CaBO·HO microspheres with nano-sized slices were synthesized using boric acid and calcium hydroxide as reactants by a facile catalyst-free hydrothermal method at low temperature. The products were characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern reveals that the CaBO·HO is a monoclinic phase polycrystalline with cell parameters a = 0·6702, b = 0·5419 and c = 0·3558 nm. SEM also reveals that the monoclinic phase polycrystalline are thorn-like microspheres composed of many flakes with an average thickness of <100 nm. Possible reaction and growth mechanism were also discussed. [ABSTRACT FROM AUTHOR]