Advanced Materials Research Vols. 602-604

Abstract: In this study, SiO₂/TiO₂ core-shell powders were prepared by 2 steps of modified sol-gel method. Silica cores were firstly prepared. In this step, polyethylene glycol was introduced in order to control shape and size. At the second step, Zn, N co-doped TiO₂ sols were prepared to coat on SiO₂ cores by dipping method. The synthesized core-shell structured powders were characterized using scanning electron microscopy, electron dispersive X-ray spectrometer, X-ray diffractometer and Fourier-transformed infrared spectrophotometer. Photocatalytic activity was evaluated by means of degradation of methylene blue solution. The effect of polyethylene glycol utilized for controlling size and shape of silica cores was studied together with the effect of calcinations temperature and amount of Zn doping on anatase phase, morphology, and crystallite size and photocatalytic property. Silica cored particles are spherical shape having particle size of 300 nm. TiO₂ coating resulted in a rough and textured surface of the core-shell particles and particle size about 400 nm. It was found that calcination temperature has a significant effect on degree of crystallinity of anatase phase, leading to enhancement of photocatalytic activity.

Abstract: The ZnO nanorods with sharp tip have been fabricated via water cooling treatment during the hydrothermal growth. The morphology and crystal structure of the zinc oxide nanostructure were examined by field-emission scanning electron microscopy and x-ray diffraction, respectively. The structural characterizations revealed that the as-synthesized nanorods were single crystalline, with a hexagonal phase. It has been demonstrated that the cooling rate is the critical factor of the synthesis of the sharp tip ZnO nanorods by comparing the different cooling conditions. The growth mechanism for the sharp tip ZnO nanorods has been proposed on the basis of the different crystallographic habits of wurtzite hexagonal ZnO crystals.

Abstract: Silver nano-particles (AgNPs) films were prepared and coated on glass fibers by reduction of [Ag(NH₃)₂]⁺ complex with sucrose at temperature of 400-600°C. The effect of AgNO₃ solution used as a source of silver was also investigated. The synthesized films were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and electron dispersive X-ray spectrometer (EDX). It was found that both concentration and temperature have an effect on crystal growth, morphology and hydrophobic property of silver nanoparticles on surfaces of glass fibers. High temperature synthesis can partially cause grain coarsening of AgNPs on the films. The hydrophobic property of these silver coarsened grains was found to increase at the calcined temperature of 600°C, leading to easily removed from the surface coating.

Abstract: Under the conditions of the presence of surfactants and ultrasonication, the use of different cerium salt, respectively, with phosphate under solid state chemistry reactions, the synthesis of nano-rare earth metal complexes of CePO4 crystals was formed. The solid phase was characterized by powder X-ray diffraction and electron diffraction. The particle size, its distribution, and morphology of the prepared nanocrystallite were observed by transmission electron microscopy. The results show that particle sizes are relatively uniform, the morphology of the crystal is spherical, the average particle diameter is about 50 nm, and the yield rate is approximately 92.8%. Furthermore, during the synthesis, the solid-state reaction conditions including raw materials, matching proportion of reactants, additions of inert substance, addition of trace solvents, surfactants and porphyrization time, etc, all have some influence on the morphology, particle size and size distribution of the final products. During the synthesis of the nanocrystalline CePO4, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different times may influence morphology, particle size and the size distribution of final products.

Abstract: Polyurethane-poly (vinyl alcohol)/chitosan (PU-PVA/CS) blend nanofiber nonwovens were successfully prepared by coelectrospinning in this paper. The morphology, diameter and structure of the electrospun nanomaterials were examined by SEM and FITR, and their mechanical properties were tested. The diameter distribution of the nanofibers was measured by Image-Pro Plus. The results show that the ideal nanofibers with the diameter in 50-350 nm can be obtained with the proper technical parameters of PU and PVA/CS nanofibers as follows: the spinning voltage at 30 kV and 40 kV, the extruding speed at 6 mL/h and 0.5 ml/h, the collecting distance at 150 mm and 200 mm, respectively.

Abstract: High anisotropic Nd13Fe75Co4B8 magnetic powders are obtained with low desorption H2-pressure of the hydrogenation disproportionation desorption recombination (HDDR) process. Scanning electron microscopy (SEM) indicates a lamella structure in the 20 kPa desorption H2-pressure HDDR products and may be related to the high anisotropy. The magnetic powders with a desorption H2-pressure of 20 kPa have the magnetic properties of Br =0.86 T and Mr/Ms =0.81.This shows that the H2-pressure has great effect on the formation of crystal texture in the HDDR Nd-Fe-B powders.

Abstract: The infrared extinction properties of columnar nano-graphite particles were studied based on the discrete dipole approximation (DDA) method. The research results show that infrared extinction properties of columnar nano-graphite particles are associated with the shape and size of particles and wavelength. For cylindrical nano-graphite particles, when the effective radius aeff =100nm，the more the length-diameter ratio deviates from value 1, the better the performance of extinction is. Under the circumstance of the same volume and length-diameter ratio, the infrared extinction will be different if the cross-section shapes of columnar nano-graphite particles are different. The infrared extinction properties of triangular prism nano-graphite particles are the best among the four kinds columnar particles.

Abstract: Cubic pyrochlore type Nd_xCo_2-xZr₂O₇ nano-crystals were prepared by salt-assistant glycine solution combustion method (SGCM), with neodymium nitrate, cobalt nitrate and zirconium nitrate as raw materials, glycine as the incendiary agent, and KCl as a reaction inert salt. The Nd_xCo_2-xZr₂O₇ nano-crystals were characterized by means of XRD (X-ray powder diffraction), FT-IR (Fourier trans-form-infrared spectroscopy), Raman spectroscopy, TEM (Transmission electron microscope) and HRTEM (High resolution transmission electron microscopy). The results showed that neodymium ions were partially substituted by cobalt ions, while maintaining the original pyrochlore structure. The nano particles obtained had a perfect crystal structure, good dispersion, and the size was about 31nm. For Nd_1.9Co_0.1Zr₂O₇ nanocrystals, the four strong diffraction peaks were at 2θ=29.18°, 33.80°, 48.49° and 57.53°. The corresponding crystal plane distances calculated by Bragg equation λ = 2dSinθ were 0.306, 0.265, 0.188 and 0.160 nm. With the study of the photocatalytic activity of the product, it is found that compared with the undoped crystals, photocatalytic activity of dopped products had been significantly improved and different doping amount led to different levels of catalytic activity. When n_Nd:n_Co = 9:1, the 2 hours net degradation amount was as high as 83%.

Abstract: This paper investigates the influence of nanoclay content on sandwich composites under flexural and impact loading. Four different combinations of sandwich samples were made of fiberglass/nano-modified polyester as face sheets and polystyrene foam as core materials. The tested samples showed that the flexural and impact properties are greatly increased, over the range of nanoclay loading.

Abstract: Cubic pyrochlore type Nd_xCo_2-xZr₂O₇ nano-crystals were prepared by salt-assistant glycine solution combustion method (SGCM), with neodymium nitrate, cobalt nitrate and zirconium nitrate as raw materials, glycine as the incendiary agent, and KCl as a reaction inert salt. The Nd_xCo_2-xZr₂O₇ nano-crystals were characterized by means of XRD (X-ray powder diffraction), FT-IR (Fourier trans- form-infrared spectroscopy), Raman spectroscopy, TEM (Transmission electron microscope) and HRTEM (High resolution transmission electron microscopy). The results showed that neodymium ions were partially substituted by cobalt ions, while maintaining the original pyrochlore structure. The nano particles obtained had a perfect crystal structure, good dispersion, and the size was about 31nm. For Nd_1.9Co_0.1Zr₂O₇ nanocrystals, the four strong diffraction peaks were at 2θ=29.18°, 33.80°, 48.49° and 57.53°. The corresponding crystal plane distances calculated by Bragg equation λ=2dSinθ were 0.306, 0.265, 0.188 and 0.160 nm. Study the catalyst effect of Nd_xCo_2-xZr₂O₇ on the thermal decomposition of ammonium perchlorate (AP) using DSC (Differential scanning calorimetry). The results showed that nano Nd_xCo_2-xZr₂O₇ had high catalytic activity during on the thermal decomposition of ammonium perchlorate. With 2% more nano Nd_xCo_2-xZr₂O₇, the peak temperature of AP thermal decomposition reaction dropped by nearly 88°C. The apparent decomposition reaction heat increased from 655J•g^-1 to 1073J•g^-1. The results showed that the catalytic effect of thermal decomposition of AP with nano cobalt-doped zirconium acid neodymium is better than the single component of nano-metal oxides and undoped zirconate neodymium nanocrystals.