Advanced Materials Research Vol. 664

Abstract: The diamond microcrystalline-aggregate array was fabricated by microwave plasma chemical vapor deposition (MPCVD) method. The ceramic with a Ti mental layer is used as substrate. The diamond array was evaluated by Raman scattering spectroscopy, x-ray diffraction spectrum (XRD), scanning electron microscopy (SEM). The field emission properties were tested by using a diode structure in a vacuum. A phosphor-coated indium tin oxide (ITO) anode was used for observing and characterizing the field emission. It was found that the diamond microcrystalline-aggregate array exhibited better electron emission properties. The turn-on field is only 1.1V/μm and a emission current density as high as 1mA/cm2 was obtained under an applied field of 3.3V/μm. The good field emission properties of the diamond microcrystalline-aggregate array are discussed relating to microstructure and electrical conductivity.

Abstract: The preparation and characterization of Unsaturated Polyester Resin (UPR) filled recycled Expanded Polystyrene (EPS) composite systems were systematically investigated. Additives such as Alumina and silica aerogel powder were added to the composite for Infrared reflection and insulation enhancement. The effect of differing alumina weight percentage on the thermal properties, i.e. thermal conductivity and glass transition temperature, T_g were determined. The fabricated composite undergoes thermal analysis by using a DSC and a hand-held thermal probe, and characterized by a FTIR. There is little variation of the T_g across the samples tested. Specific heat capacity, c_p from the DSC thermogram was significantly affected by incorporation of silica aerogel; 565 J/kgK compared to the unfilled sample result of 1706 kJ/kg. The thermal conductivity showed a minimum at 0.147 W m^-1 K^-1 from integrated silica aerogel only sample, and alumina addition increases the thermal conductivity above the minimum k value in the ranges 0.227-0.313 W m^-1 K^-1. Alternative C_p values from the thermal probe followed similar trend as the DSC C_p. Thermal diffusivity from the probe also showed an increase upon silica aerogel and alumina incorporation.

Abstract: Flower-like ZnO nanostructures have been synthesized via solution process using zinc nitrate and sodium hydroxide at very low temperature of 70 °C in 1h. The structure, morphology and optical properties of the product were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and photoluminescence. The flower-like ZnO nanostructures were composed of uniform nanorods, they were well crystallized with a hexagonal wurtzite structure, and showed a strong ultraviolet emission at 385 nm and a weak and broad yellow emission in the photoluminescence spectrum.

Abstract: A novel microspheres adsorbent was prepared by the emulsion-congealed crosslinking method. The gelatin was as raw material and glutaraldehyde was as the crosslinking agent. The product was characterized by AFM, Zeta Potential Tester and SEM. These results showed that there were some irregular protuberances and grooves on the surface of gelatin microspheres. The relative surface roughness namely Ra was equal to 2.469E+01nm. The isoelectric point of gelatin microspheres was 3.2. Their morphology was almost not affected by treatment of the acid and alkali, and the performance of the acid and alkali resistance was superior. The result of desorption experiment showed that the regeneration ability of gelatin microspheres was stronger in the alkali solution than that in the distilled water. The optimum desorption temperature was 30°C. The desorption process got to balance for 80min. The desorption rate got to 88% in the alkali solution and regeneration effect was obvious. The result of the second-adsorption experiment showed that the desorbed adsorbent which was used in the second-adsorption experienced the same as the first-adsorption process. And the saturated adsorption capacity changed a little. So the gelatin microspheres can be recycled.

Abstract: The local structure evolution of polyacrylonitrile (PAN) fibers during pre-oxidation and carbonization was studied using X-ray diffraction (XRD) and radial distribution function (RDF). The nearest inter-chains distance of PAN is 6.88 Å, which is close to the diameter of the “rigid rod” model proposed by Warner. The third neighbor distances of carbon fibers are greater than that of graphite, indicating the planar six-member rings are absent in the carbon fibers from 500 to 1250°C. The structure of fibers transforms from long-range order to long-range disorder during the pre-oxidation process, then transforms from short-range order to long-range order during the carbonization process.

Abstract: Pottery stone (PTS) microcrystalline powders were synthesized by a hydrothermal method using two concentrations of NaOH solution (2 M and 4 M) at 60, 80 and 120°C for 8 h in a Teflon- lined stainless steel autoclave. The phase composition and morphology of the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The major phase compositions of the as-prepared PTS powders appeared in the XRD patterns are all silicate compounds such as tridymite, crystobalite, quartz, feldspar, albite, sodium silicate, analcime, hydroxyl-cancrinite and sodium aluminium silicates, depending on the NaOH concentration and the reaction temperature. Moreover, SEM micrographs showed the spherical polyhedral particles ranging from 8 to 14 µm in diameters and needle-like particles with a mean aspect ratio of 5.7 that obtained by the hydrothermal treatment operated at 120°C using 2 M and 4 M of NaOH, respectively.

Abstract: Kinetic indentation diagram has been used for the mathematical description of the contact interaction between a sphere and elastoplastic half-space. The unloading curve exponent m has been determined. It has been shown that the value of m is independent of the load distribution on the contact surface, and does depend on the ratio c²h/R (or h_c/R). Based on the deformation characteristics similitude, the sphere penetration value h has been determined for the areas of constrained and developed elastoplasticity. The new parameter k_h(ε_y,n) has been introduced to account for the material hardening.

Abstract: This work aims at the characterization of power transformer oil mixtures by using dc charging currents measurements for long field application times. The principle of this approach is inspired from the technique of measurements carried out on solid dielectrics used in high voltage insulation. It will be applied to characterize mixtures between two compatible oils of different provenances and ages. The obtained results are conclusive and reinforce those obtained by classical physicochemical methods of characterization. For the purpose, we intent to link between the space charge behavior in the insulation and its several characteristics. Moreover, in addition to the fact that the obtained results are in good agreement with the physicochemical characteristics, the charging currents reported at room temperature enabled us to determine the mixture resistivity and charge carriers' mobility.

Abstract: The aim of this study is to assess the volumetric and mechanical behavior of concrete asphalt mixtures, using natural sludge as a partial substitute for the tiny aggregate and calcined sludge as filler. This assessment was performed based on technical and environmental parameters, using laboratory tests obeying current Brazilian norms, according to international standards. The addition of natural sludge to the mixtures has increased stability, increased air voids contents of the mixtures. The addition has compromised mixture adhesiveness. With respect to the addition of calcined sludge to the mixtures, the mixtures with calcined sludge displayed the same behavior as those with cement. It was observed decrease in empty space volume of the mixtures and consequent increase in empty space-bitumen relation and increased stability. The mixture addition of natural sludge that has the best mechanical and volumetric performance is the one with 7.5% of natural sludge in the granulometric composition of the mixture. The mixture with 1% of calcined sludge had the best volumetric and mechanical performance.

Abstract: In this work, biodegradable plastics were produced from different poly(lactic acid) (PLA)/ poly(butylene succinate) (PBS) blend ratios in the presence of a fix loading (1 phr) of a commercial epoxy functionalised polymeric chain extender (Joncryl ADR-4300-S). The effects of blend ratio and chain extender on the tensile properties, thermal stability and morphology were investigated by the tensile testing, thermogravimetric analysis (TGA) and scanning electron microscopy, respectively. The results show that the incorporation of PBS and Joncryl into PLA apparently reduced the tensile strength and tensile modulus, but increased the elongation at break of the blends in a dose-dependent manner. However, their blends provide interesting materials for industrial packaging applications, due to their enhanced ductility by decreasing the tensile modulus and increasing the elongation at break. TGA analysis showed that thermal stability of the blends was lower than that of the pure PLA and PBS. Moreover, the chain-extended products exhibit two stages of thermal decomposition, the first was due to the degradation of PBS, and the second was due to the degradation of PLA.