Low temperature synthesis of vanadium carbide (VC)

Nanocrystalline VC has been prepared via a convenient route by the reaction of metallic magnesium powder with vanadium pentoxide and basic magnesium carbonate in an autoclave at 650 °C. X-ray powder diffraction pattern indicated that the product was cubic vanadium carbide, and the cell constant was a = 4.155 Å. Scanning electron microscopy (SEM) image showed particles with an average size of about 60 nm. The product was also studied by BET and TGA. It had good thermal stability and oxidation resistance below 350 °C in air.     

Preparation and transformation to hollow nanospheres of wrapped CuS nanowires by a simple hydrothermal route

In this paper we reported the preparation of wrapped CuS nanowires via a simple hydrothermal reaction at 180 °C for 2 h, employing CuSO₄·5H₂O and thiourea as reactants in the absence of any structure-directing agent. SAED pattern showed that the wrapped CuS nanowires were polycrystalline, which was comprised of small nanoparticles. TEM observations showed that wrapped nanowires could grow and further transfer to hollow spheres with the prolonging of the reaction time from 2 h to 13. The UV-Vis spectra of CuS prepared at 180 °C for different times were studied. The possible transfer mechanism from wrapped nanowires to hollow spheres was suggested.     

Synthesis, thermal stability, and photocatalytic activity of nanocrystalline titanium carbide

Titanium carbide (TiC) was prepared via one simple route by the reaction of metallic magnesium powders with titanium dioxide (TiO₂) and potassium acetate (CH₃COOK) in an autoclave at 600 °C and 8 h. Phase structure and morphology were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). The results indicated that the product was cubic TiC, which consisted of particles with an average size of about 100 nm in diameter. The product was also studied by the thermogravimetric analysis (TGA) and its photocatalysis. It had good thermal stability and oxidation resistance below 350 °C in air. In addition, we discovered that the cubic TiC powders exhibited photocatalytic activity in degradation of Rhodamine-B (RhB) under 500 W mercury lamp light irradiation.     

One simple synthesis route to whisker-like nanocrystalline boron nitride by the reaction of NaBH4 and NaN3

Nanocrystalline boron nitride (BN) was synthesized via a simple route by the reaction of sodium borohydride with sodium azide in an autoclave at 600 °C. X-ray powder diffraction pattern indicated that the product was hexagonal BN, and the cell constant was a = 2.495 Å, c = 6.687 Å. Transmission electron microscopy image showed that it consisted of whisker-like particles with an average size of 200 nm × 20 nm. The product was also studied by FT-IR, XPS and TGA. It has good thermal stability and oxidation resistance in high temperature.     

A novel route for the synthesis of nanosize particles of metallic palladium

A novel route for the synthesis of metallic palladium consisting of nanosize particles has been reported. The synthesis is based on (a) the addition of tetramethylammonium hydroxide (TMAH) to the aqueous solution of PdCl₂, and (b) autoclaving of this precipitation system at 160 °C. The distribution of the nanosize particles of metallic palladium has its mean value at about 18 nm. The mechanism of the metallic palladium formation is briefly discussed.     

A simple and low-temperature hydrothermal route for the synthesis of tubular α-FeOOH

Tubular α-FeOOH was synthesized via hydrothermal reaction at 120 °C. X-ray diffraction (XRD) pattern indicates that the as-prepared sample is the pure orthorhombic phase α-FeOOH. Fourier transform infrared (FT-IR) analysis further confirms the formation of orthorhombic phase α-FeOOH. The morphology and structure of the as-obtained product were characterized by transmission electron microscopy (TEM) techniques. TEM images show a high degree of contrast between the bright central part and the darker edges, demonstrating the hollow core of the product. The obtained tubular α-FeOOH was ∼ 10 nm in outer diameter and ∼ 6 nm in inner diameter, respectively. High-resolution TEM image of one single nanotube shows the clearly resolved interplanar spacing of about 4.18 Å, which corresponds to the spacing between (110) planes of the orthorhombic-type α-FeOOH crystal. The room-temperature UV-Vis absorption spectrum of the tubular α-FeOOH nanostructures is presented.     

A simple route to synthesis and characterization of CoAl2O4 nanocrystalline via combustion method using egg white (ovalbumine) as a new fuel

Single phase of CoAl₂O₄ nanocrystalline spinel has been synthesized first time successively by combustion method using extracted egg white (ovalbumine) as new fuel. The prepared samples were characterized using XRD, TGA, DSC, TEM, BET, IR, UV-Vis and CIE L*a*b* colorimetric method. The average particle sizes were in the range 10.45-26.58 nm and fine agglomerates in a way that specific surface area up to 188.55 m² g⁻¹ could be obtained.     

Synthesis of nanocrystalline Mo2C via sodium co-reduction of MoCl5 and CBr4 in benzene

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 Å. Transmission electron microscopy (TEM) study showed that the product consisted of slightly conglomerated particles of about 30 nm in size.     

Crystal structure of ball-milled mixture of sodium chloride and magnesium chloride-ethanol adduct

NaCl doped MgCl₂·nEtOH adducts were prepared by ball-milling MgCl₂·2.5EtOH with NaCl. Both the ball-milled MgCl₂·nEtOH/NaCl mixture and pure MgCl₂·2.5EtOH adducts were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetry (TG) and differencial scanning calorimetry (DSC). A simple MgCl₂·nEtOH/NaCl mixture without ball-milling treatment was also studied for comparison. Two kinds of mixed crystals, Na₂MgCl₄ and NaMgCl₃, were found to be formed in a ball-milled mixture that contained 16 mol.% NaCl. TG and DSC analysis of the samples also provided indirect evidences supporting the presence of the mixed crystals in the ball-milled mixture. Adding certain amounts of NaCl in MgCl₂·2.5EtOH adduct, either by co-milling or by simple mixing, greatly increased the thermal stability of the adduct, but thermal decomposition behaviour of the ball-milled mixture was still different from that of a simple mixture.     

Facile synthesis and characterization of hydrophobic vaterite CaCO3 with novel spike-like morphology via a solution route

Hydrophobic spike-like vaterite CaCO₃ composed of nanoparticles with an average size of 100 nm has been successfully synthesized via a simple synthetic method. The crystallization of vaterite CaCO₃ was fabricated by the reaction of CaCl₂ with Na₂CO₃ in ethanol-water solvents in the presence of oleic acid. The as-prepared products were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and contact angle analysis. The characterization results revealed that oleic acid played an important role in determining the phase and morphology of the sample. In addition, the surface properties of the vaterite CaCO₃ changed from hydrophilic to hydrophobic. The contact angle of the modified CaCO₃ reached 95.8°.     

A novel route to the synthesis of nanosized metallic molybdenum at moderate temperature and its catalytic properties

Nanosized metallic molybdenum could be synthesized from MoO₃ and KBH₄ by solid-state reaction at moderate temperature. The crystallinity, morphology, surface properties of as-synthesized metallic molybdenum were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectral (XPS). The results of its catalytic activity test show that the as-synthesized nanosized metallic molybdenum is superior to the noble metal catalyst 0.3% Pd/Al₂O₃ for the selective hydrogenation of alkadienes at higher temperature and pressure.     

Repeatable synthesis of Cu2O nanorods by a simple and novel reduction route

Cu₂O nanorods were synthesized by reducing bamboo leaf-shaped Cu(OH)₂ with sodium hypophosphite (NaH₂PO₂) in an H₂O/ethylene glycol (EG) mixing solution. The Cu(OH)₂ was prepared by adding an alkaline solution to an aqueous solution containing CuSO₄ and NaH₂PO₂ at room temperature. The optimum temperature range for the reduction of the Cu(OH)₂ to Cu₂O nanorods was 55-70 °C. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The result showed the prepared Cu₂O nanorods were uniform and had diameters of 10-20 nm and lengths of 150-200 nm. The synthesis is simple, inexpensive, and highly repeatable.     

Powder synthesis and characterization of nanocrystalline CeO2 via the combustion processes

Nanocrystalline CeO₂ powders were synthesized by the combustion reactions using citric acid and glycol as fuels and nitrate as an oxidant. The adiabatic flame temperatures in the auto ignition processes of the precursors were calculated theoretically. XRD measurements indicated that the powders produced in the combustion processes were cubic fluorite CeO₂ phase. The size and morphology of the particles and extent of agglomeration in the powders were studied using transmission electron microscopy (TEM) and the particle size analyzer respectively. Blue shifts of the absorption peak of the as-prepared powders were observed.     

Synthesis of nanocrystalline magnesium aluminate (MgAl2O4) spinel powder by the urea-formaldehyde polymer gel combustion route

Nanocrystalline MgAl₂O₄ spinel powder was synthesized by the urea-formaldehyde (UF) polymer gel combustion route. A transparent gel formed from magnesium nitrate, aluminium nitrate and UF after drying underwet self-sustained combustion when initiated with a burning splinter. The combustion product on calcinations at 850 °C formed MgAl₂O₄ spinel. Calcination of the combustion product resulted in particle coarsening. The powder obtained by planetary ball milling of the spinel had a median particle size of 1.58 μm. The spinel particles are agglomerates of nanocrystallites of size in the range 10-30 nm. The compacts prepared by uni-axial pressing of the spinel powder sintered to >99% TD at 1600 °C.     

Reversible thermal behavior of the layered double hydroxides (LDHs) of Mg with Ga and In

The layered double hydroxides (LDHs) of Mg with Ga and In decompose completely on heating to 500 °C to yield poorly ordered oxide residues. In the Mg-Ga system, the oxide residue has a rock-salt structure with Ga incorporated in the MgO matrix. In the Mg-In system, the oxide residue is X-ray amorphous. These oxide residues revert back to the original LDH either on standing in a water-saturated atmosphere or on hydrothermal treatment in a Na₂CO₃ solution. In contrast, the LDHs of Co with Ga and In yield the thermodynamically stable spinel oxides and the decomposition is irreversible. These results have implications for the synthesis of ‘oxide’ catalysts by thermal decomposition of the LDHs.     

A simple and novel route for the synthesis of water soluble ZnSe quantum dots using the Nano-Se as the reaction intermediate

A new and simple synthesis method for water soluble and low toxic ZnSe QDs is presented in this paper. N-acetyl-l-cysteine (NAC) is chosen as the stabilizer of ZnSe QDs and reducing agent of Na₂SeO₃ in one reaction system. The reaction intermediate Nano-Se generated by the redox reaction between NAC and Na₂SeO₃ is used as the Se source. The water soluble ZnSe QDs obtained by our synthesis method show blue-green light emission. The effects of the pH, stabilizer concentration and synthesis time on the photoluminescence (PL) intensity of ZnSe QDs are also investigated. This new synthesis method simplifies the reaction steps, enhances the utilization rate of chemicals and reduces the cost.     

Large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles with a simple route and their application to photocatalytic degradation

We report the large-scale synthesis of hexagonal cone-shaped ZnO nanoparticles by the esterification between zinc acetate and alcohol. The morphology of the ZnO nanoparticles was investigated by transmission electron microscopy, selected area electron diffraction and scanning electron microscopy measurements. The synthesized ZnO nanoparticles are single-crystalline with hexagonal phase and show a strong UV emission at −378 nm due to the excellent crystallinity of particles. A possible formation mechanism of the hexagonal cone-shape structure is proposed. Furthermore, the as-prepared ZnO particles exhibit high photocatalytic activity for the photocatalytic degradation of Rhodamine B, indicating that the ZnO nanostructure is promising as a semiconductor photocatalyst.     

Microwave-assisted synthesis: A fast and efficient route to produce LaMO3 (M = Al, Cr, Mn, Fe, Co) perovskite materials

A series of lanthanum perovskites, LaMO₃ (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol-gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.