Advanced Materials Research Vols. 194-196

Abstract: Coral-like α-Fe₂O₃ nanostructures modified by surfactant CTAB have been successfully obtained via a solvothermal process by using FeCl₃ 6H₂O and oxalic acid as the starting materials. The coral-like α-Fe₂O₃ nanostructures with good-crystalline consist of well-aligned α-Fe₂O₃ nanoflakes with an average thickness of about 40 nm growing radially from the center of the nanostructures. The obtained products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), superconducting quantum interference device magnetometer (SQUID). Magnetic hysteresis measurements indicate that coral-like α-Fe₂O₃ superstructures show a normal ferromagnetic behavior with the remanence and coercivity of 0.2346emu/g and 1862Oe at room temperature. CTAB, the reaction temperature and solvent played an important role in controlling the final morphology of the products.

Abstract: This study focused on the preparation of electrospun polystyrene (PS) nanofibers. Polystyrene solutions were prepared in single (dimethylformamide; DMF, dimethylacetamide; DMAc or tetrahydrofuran; THF) and mixed solvent (DMF/THF and DMAc/THF) systems prior to electrospinning. The effects of solution parameters, including PS concentration and solvent system on solution properties (e.g. conductivity and viscosity), appearance and diameter of polystyrene fibers were examined. The morphology of the as-spun fibers were carefully investigated using scanning electron microscopy (SEM). It was found that the average diameter of the as-spun fibers increased upon increasing PS concentration. Moreover, the morphology of the fibers significantly depended on the properties of the solvents. The obtained fibers were smooth without any beads and their diameters depended on the amount of THF in the mixed solvent and PS concentration. In summary, the smallest diameter (927±81 nm) and the narrowest fiber diameter distribution of PS nanofibers were obtained from 15% PS solution in DMF/THF (75/25).

Abstract: Hydrophobic magnesium hydroxide (Mg(OH)₂) nanoparticles are prepared by surface modification method with oleic acid (OA) as surface modifier. The influence of synthesis parameters on the hydrophobicity of magnesium hydroxide nanoparticles were studied, such as the amount of OA, modification time and reaction temperature. The results show that the product obtained with this method possesses excellent hydrophobic property such as a high water contact angle of 106° and a well dispersion. The Mg(OH)₂ nanoparticles exhibit a lamella morphology and staggered pattern. The scanning electron microscopy (SEM) results prove that the hydrophobic property is enhanced dramaticlly due to this morphology. The Fourier transform infrared spectroscopy (FTIR) analysis and Thermogravimetric (TGA) analysis prove the OA molecules are bonded onto the surface of Mg(OH)₂ nanoparticles with a stable chemical bond. The crystal habit of the magnesium hydroxide nanoparticles was characterized by X-ray diffraction (XRD).

Abstract: Single crystalline Fe₃O₄ nanorods were fabricated in high yield via a facile hydrothermal route in the presence of sodium citrate as addition agent. The phase structures, morphologies, and sizes of as-prepared products were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The diameter of magnetite nanorods is about 50~80 nm and its length is more than 2 μm. Room-temperature magnetic measurements showed that Fe₃O₄ nanorods exhibited high saturation magnetization and coercitivity of 77.8 emu/g and 98 Oe, respectively, while the as-obtained nanoparticles had low coercitivity value.

Abstract: Polymer-based conductive adhesive materials have become widely used in many electronic packaging interconnect applications. In this paper, a new kind of polymer-based conductive particle used in anisotropic conductive adhesive films (ACFs) is prepared. The preparation of the single scattered polystyrene spheres with the particle size of 3 microns around and the less than 5% dispersion coefficient is done successfully, and a layer of nickel is coated on the surface of polystyrene spheres using chemical plating method well.

Abstract: Electrospinning is a technique use to fabricate ultrafine fibers with diameters in the nanometer range. The electrospun fiber mats have high potentials for many applications, due to their high surface area to volume, high porosity and small pore size. In this study, chitosan-ethylenediaminetetraacetic acid (CS-EDTA)/polyvinyl alcohol (PVA) blend nanofibers were successfully prepared using electrospinning techniques without organic solvent. CS was dissolved in EDTA aqueous solution and then blended with PVA solution at various weight ratios. Physicochemical properties of CS-EDTA/PVA solution such as viscosity, conductivity and surface tension were investigated. The morphology and diameter of the electrospun fiber mats were analyzed by using scanning electron microscopy (SEM). The composite structure was characterized by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FT-IR). SEM images showed that the morphology and diameter of the nanofibers were mainly affected by the weight ratio of the blend. Nanofibers were obtained when the CS-EDTA content was less than 50%wt. The average diameter of the nanofibers was 119-223 nm, and this average diameter decreased with increasing CS-EDTA content. In summary, these CS electrospun nanofiber mats may be proper for the drug delivery or wound dressing application.

Abstract: The nanoalloy NiCoB and NiCoB/SiO2 catalysts were prepared by an incipient impregnation-chemical reduction method with NaBH4. They were characterized and examined for their catalysis in the hydrogenation of furfural to furfural alcohol. NiCoB and NiCoB/SiO₂ catalysts were characterized by XRD as amorphous structure. The amorphous NiCoB/SiO₂ catalyst was active in the hydrogenation of furfural, and it was significantly more active than NiB, CoB and NiCoB.

Abstract: Zinc niobate, Zn₃Nb₂O₈, dielectric ceramics were fabricated by sintering Zn₃Nb₂O₈ nanopowders derived from a rapid vibro-milling technique at various temperatures. Phase formation, densification, microstructure and dielectric properties of the ceramics were investigated as a function of sintering temperatures (1000-1200°C), using a combination of X-ray diffraction, Archimedes density measurement, scanning electron microscopy and dielectric measurement, respectively. It has been found that single-phase Zn₃Nb₂O₈ ceramics with maximum density of ~98% theoretical density can be successfully produced with appropriate firing temperature, without any firing additives. Moreover, it is seen that the dielectric properties are found to enhance with increasing sintering temperature and grain size.

Abstract: V₂O₃ and VN nanocrystals have been conveniently synthesized from thermal ammonolysis of the precursor VOC₂O₄•H₂O in a resistance tubular furnace at 500°С and 780°С for 30 min, respectively. The products were characterized by X-ray diffractometer (XRD)、X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. The average particle sizes of V₂O₃ and VN are both in the ranges of 20~35 nm. The evolution from precursor to hexagonal V₂O₃ and then to cubic VN was explored. The crucial factors，such as the reaction temperature and time，have also been discussed.

Abstract: In order to synthesize WC-Co nanopowders through an integrated mechanical and thermal activation process, WO₃-Co₂O₃-C nanopowders need to be obtained first. It is critical how to obtain the WO₃-Co₂O₃-C nanopowders efficiently. The effect of processing parameters on the grain size during high-energy-milling of WO₃-Co₂O₃-C mixed powders was studied via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the grain size of reactants can be effectively decreased with increasing the milling time, rotation speed, and charge ratio. After a certain time milling, both WO₃ and C powders achieve nano-level in grain size and mixed homogeneously. The appropriate milling parameters for fabricating nanosized WO₃+C+Co₂O₃ powders are suggested to be 4 to 8 hours of milling time, 400 RPM of rotation speed, and 40:1 to 60:1 of charge ratio.