Materials Science Forum Vols. 809-810

Abstract: Silicon nanoparticles have extraordinary electrochemical performance for lithium-ion batteries. This paper gives an improved low temperature solution synthesis route of Si NPs. Reduced by magnesium and then passivated by four kinds of amines/amides respectively, stable yellow Si NPs ranging from 5-50 nm were prepared. When passivated by N-methyl-2-pyrrolidone, grape-like aggregation of 5-20 nm particles were generated. FTIR, XRD, SEM and Electrochemical Characterization were performed to confirm the product. The Si NPs passivated by NMP achieve good electrochemical performance with a first discharge capacity of 1154 mAhg^-1 at a current density of 200 mAg^-1 and good capacity retention of 95.3% after 5 cycles.

Abstract: Highly-ordered V₂O₅ nanowires were prepared by sol-gel strategy using anodic aluminum oxide (AAO) as a template. The morphologies, structures and components of the nanowires were characterized by XRD, SEM and XPS. The results indicated high-ordered and uniformly distributed V₂O₅ nanowires were obtained, and the length and diameter were dependent on the diameter and the thickness of the applied AAO template. The V₂O₅ nanowires modified glassy carbon electrode (GCE) was used to investigate the electrochemical properties of dopamine (DA), V₂O₅ nanowires exhibited an excellent electrocatalytic behavior on DA.

Abstract: Mg-doped GaN nanowires have been successfully synthesized on Si (111) substrates by magnetron sputtering deposition through ammoniating Ga₂O₃/Au thin films at 900 °C for 15 min. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and photoluminescence (PL) spectrum were carried out to characterize microstructure, morphology, and optical property of GaN sample. The results demonstrate that the nanowires are single-crystal Mg-doped GaN with hexagonal wurtzite structure and high crystalline quality, which have the size of 40 nm in diameter and several tens of microns in length and good emission property. The growth procedure mainly follows the VLS mechanism, and Au plays an important role as catalyst, and more defect energy is formed due to metallic Au and thus promote the growth of GaN nanowires.

Abstract: Dry waters with ammonium biphosphate solution as core were prepared and used as fire extinguishing agent for the first time. The dry waters were near-spherical and had a size smaller than 200 μm. The fire suppression performance of the dry waters was higher than that of ABC powder. The dry waters with different core composition could be mixed and used as fire extinguishing agent.

Abstract: Monodisperse mesoporous silica microspheres (MSM-SF) were successfully prepared through PICA and pseudomorphic transformation using silica fume as original silica source. The structure and morphology of spheres were quantitatively investigated by Zata potential and particle size analyzer, N2 sorption isotherms, XRD, SEM and TEM. The results showed that the monodisperse spherical mesoporous silica microspheres (MSM-SF) exhibited uniform spherical morphology, worm-like mesoporous, large BET surface area of 559.9m2/g; its BJH average pore size diameter and total pore volume are 3.3nm and 0.12cm3/g, respectively. This preparation method provides a new synthetic strategy to control the particle morphology and structure simultaneously, meanwhile this method can also significantly reduce the cost of synthesis of mesoporous silica microspheres.

Abstract: The distributed processing of β-SiC submicron powders were carried out by tetramethyl ammonium hydroxide (TMAH). The effects of dispersant on the dispersion stability of the β-SiC powders were investigated by the particle size, flow characteristics, morphology and other physical properties of the powder before and after dispersed treatment. The results show that the best dispersing state of SiC is obtained by using the ultrasonic 7mins. In these conditions, the suspension solid content of β-SiC is 8%, and the dosage of TMAH is 8wt.%. An optimum amount of TMAH is proved as 8wt.% when the solid content is kept as 8wt.%. The powder particle size has been reduced from 0.73μm to 0.45μm, and its flowability has improved significantly after low temperature drying. The dispersed powder has small particle size, uniform distribution and excellent dispersion stability.

Abstract: One lanthanide nitrate (Ln = Tb) with a novel three dimensional structure have been prepared through hydrothermal method. Single crystal X-ray diffraction structures were obtained. The compound crystallizes in the orthorhombic, Pnma space group. The lanthanide ions are eight-coordinate with six oxygen atoms coming from nitrate ions and two from bridge oxygen atoms. If the bridge oxygen atoms could be ignored, the compound can be described as a rare microporous 3D Lanthanide nitride with the open framework.

Abstract: In this paper, the hollow polymer nanolatex microspheres with uniform size and good monodisperse made by in-situ polymerization with the method of encapsulation non-solvent,and the effect of crosslinking monomer (DVB) dosage in the shell on the morphology and opacity of the hollow polymer nanolatex microspheres were investigated by the characterization methods of particle size analysismeter, viscosity meter, acid value analysis, SEM, TEM and UV-Vis spectrophotometry. The results show that under the other conditions and MAA dosage of the shell unchanged, when the crosslinking monomer dosage of the shell was less than 15wt%, with the reduce of the crpsslinking monomer dosage in the shell, the strength of the shell of the hollow polymer nanolatex microspheres trends decrease, when pore-swelled, the hollow polymer nanolatex microspheres were easily cracked and collapsed; when the dosage was greater than 20wt%, with the increase of the crosslinking monomer dosage in the shell, the strength of the shell and particle size of the hollow polymer nanolatex microspheres trends increase and decrease respectively, it becomes difficult to swell; when the dosage is between 15-20wt%, the dry film of the emulsion containing the hollow polymer nanolatex microspheres obtained the the optimal opacity performance.

Abstract: We report a facial and straightforward method to fabricate highly ordered two-dimensional graphene arrays. A monolayer molecule pattern with alternative hydrophilic/hydrophobic wetting property was first formed by using micro-contact printing (μCP) and self-assembly techniques. Water droplets were condensed on the hydrophilic areas under saturated water atmosphere, which could be used to construct the ordered graphene arrays. The optical microscopy and atom force microscopy results indicate that ring and porous arrays of graphene can be obtained with low and high concentration of graphene solutions, respectively. Without the water droplet template, graphene patterns with square structure were produced.

Abstract: In this study, hollow glass microspheres (HGM) and hollow polystyrene microspheres (HPSM) have been employed as fillers in epoxy resin to prepare the syntactic foam. A kind of good performance composite was prepared. The effects of presence of various hollow microspheres on the impact and compressive properties of syntactic foams are studied. Weight fraction of HPSM and HGM for the syntactic foams varies up to 2.0 wt% and 25 wt%, respectively. The results show that the coupling agent can induce the interfacial adhesion between the HGM and the resin and help HGM uniformly disperse in the resin and hence result in better mechanical properties of composite. On the other hand, the effect of HPSM for the composite density is greater than that of HGM. The addition of a small percentage of HPSM helps produce an important improvement in the low density of syntactic foam. The syntactic foam has uniform stability component and the excellent integrative performances. Fabricated syntactic foams had compression strength of 51.96 MPa and density of 0.671 g/cm³.