Advanced Materials Research Vol. 924

Abstract: Conductive polyacrylonitrile film reinforced by multiwall carbon nanotubes was prepared via ultrasonic dispersion and vacuum casting. The structure of MWNT/PAN composite film was characterized by WAXD and FT-IR. The LOI of the blend was enhanced from 18.1 % to 24.5 % and TGA show better thermal stability. MWNT composite at 10 wt% MWNT loading showed an electrical conductivity of 10^-2S/cm.

Abstract: The crystal structures, band structures, density of states, charge density, overlap population and optical properties of pure anatase TiO2 and Pr-doped anatase TiO2 were studied by using the plane-wave pseudopotential method based on the first-principles. After Pr doping, the valence band and the conduction band moved down and became dense, energy gap became narrow and a impurity band which consists of Pr 4f states appeared. And the dipole moment got improved, which is good for the separate of the electron-hole pairs. These effectively overcome two huge shortcomings of TiO2. Besides, Pr-doped anatase TiO2 produced more carriers which have good transport properties and the absorption spectra of Pr-O bond appear in the region that the wavelength is longer. The calculation results of optical properties show that the absorption edge occured red shift, which means the photocatalytic activity of anatase TiO2 got remarkable improved during visible-light region. This conforms to the previous analysis. So the photocatalytic activity of anatase TiO2 got remarkable improved after Pr doping.

Abstract: A new solid base, mesoporous K₂O-MgO/ZrO₂-La₂O₃, was prepared by hydrothermal and immersion process using a cationic surfactant C₁₆H₃₃(CH₃)₃NBr (CTAB) as template．The samples were characterized by N₂ adsorption-desorption, X-ray diffraction(XRD), Raman spectroscope and CO₂ temperature programmed desorption(CO₂-TPD). XRD and Raman spectra indicated that the catalyst calcined at 600°C and 700 °C remained surface and bulk tetragonal phase and good mesoporous characteristics when the content of K₂O is less than 0.5. While the monoclinic phase is appeared on catalyst surface when the content of K₂O is more than 0.5 calcined at 700 °C. CO₂-TPD proves that there are two adsorption states at high temperature corresponding to super alkaline sites of K₂O and undecomposed KNO₃. The catalyst with 0.4 mol ratio of K₂O to ZrO₂ calcined at 700 °C showed higher activity in the synthesis of di-2-ethylhexyl carbonate (DEHC) from dimethyl carbonate (DMC) and 2-ethylhexanol (EHOH).

Abstract: Sapphire single crystal is widely used in many fields because of its excellent properties, as a focus of mechanical test, nanoindentation on sapphire is paid a great deal of attention by researchers. In this manuscript, the maximum load, depth and loading rate effects on the first pop-in event during nanoindentation of sapphire single crystal were discussed, the results indicated that these factors had no effect on the load at which the first pop-in occurred and the extension width of pop-in; the deformation below the first pop-in event was discussed and it could be roughly considered as purely elastic deformation through analyzing.

Abstract: Chitosan (CTS) is the partly deacetylated product of Chitin. It contains hydrogen bond and ionic bond, which can form a cage-like molecular network structure and thus it has a strong adsorption. According to the presence of hydroxyl and amino groups of the chitosan, through chemical modification, introduces different groups in repeating units become possible. In this article, different component of the rectorite (REC) were used to intercalate the chitosan in order to have the quaternary ammonium modification. Through this process we could obtain three kinds of chitosan/rectorite modified products. Besides, their structures were observed by using the X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). This paper also explained the examination of the adsorption effect of three kinds of chitosan/ rectorite modified products to the methylene blue under different conditions. Whats more, it also discussed the main factors of this effect. The results showed that the three adsorption behavior of adsorbents can be described by using the Freundlich isotherm model. In three kinds of chitosan/ rectorite modified products, 4:1 CTS/REC-ETA demonstrated the best adsorption. Followed was the 2:1 CTS/REC-ETA. And the 8:1 CTS/REC-ETA was the weakest.

Abstract: The effect of Al-doping concentration and sintered temperature (ST) on the structure and room-temperature ferromagnetism (RTFM) of Al-doped Zn_0.990Co_0.010O nanocrystals was investigated. The experimental results have indicated that all samples have RTFM and are composed of wurtzite ZnO with hexagonal structure without any secondary phases. The crystallization quality is positive related to ST and negative related to Al-doping concentration. When ST is higher than 800°C, the RTFM is dominated by the long rang coupling induced from the conductive carriers of Al³⁺, since it is increasing with the increase of Al-doping concentration and grain sizes. When ST is lower than 800°C, the RTFM is dominated by localized carriers from oxygen vacancies, since the maximum RTFM belongs to the sample which has the lowest parameters of unit cell.

Abstract: Saturation behavior in photocatalysis is investigated for volatile organic carbons (VOCs) and ammonia by using a tubular photoreactor and TiO₂ nanoparticles, synthesized by a flame chemical vapor deposition (CVD) process. Degradation degree versus initial concentration shows that saturation behavior occurs at different initial concentrations for different gas pollutants. The saturation concentration is obtained by taking as the intersection of the level off part and the tangential line to the rapid change part from the curve of degradation degree versus initial concentration. The saturation concentration for benzene is as low as 0.063 mg/m³, and is up to 720mg/m³ for formaldehyde for TiO₂ nanoparticles synthesized by a flame CVD process.

Abstract: Through scanning electron microscope (SEM) observation on kinetic friction and static friction deformation, our data show that granular nanoparticles (commonly 60-80nm with diameter, d) are widespreadly distributions in narrow friction zones. Furthermore, the identification markings, such as nature, experiment and fabric orientation etc., usefully deal with the mechanical analysis,and the granular nanoparticle distributions in narrow friction zones could be subdivided into three kinds, i.e. simple shear, pure shear and rotational shear pattern. Additionally, note that under stress action physico-chemical phase changes might be respectively caused by internal cohesion and dynamic differentiation in the narrow friction zones. These analyses deduce that some few complex idea fields, including structural stress, physics and chemistry field, with spatial and temporal evolution exist in the narrow friction zones, moreover, they viably regulate the nanoparticle distribution.

Abstract: Core-shell Ag@ZnO heterostructures are designed and fabricated by a facile two-step chemical method. The heterostructures are composed of Ag microspheres as the core, on which plenty of small ZnO nanorods grow as the shell. The morphological, structural and Raman properties of the composites were investigated by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering spectra. A strong surface-enhanced Raman scattering (SERS) and Raman red shift of ZnO nanorods were observed in Ag@ZnO core-shell nanocomposites due to the effect of Ag microspheres.

Abstract: High quality PbS nanorcrystallines (NCs) have been fabricated in high yield by a simple hydrothermal method using unique ligands. We find that the experiment conditions such as different ligands,the reaction temperature greatly influence the morphology and the size of PbS NCs. Specifically, the complex ligands OPA and butylamine have great effects on the final products compared with no ligand. We can obtain PbS nanocrystalline with more homogeneous size and higher optical properties. On the other hand, higher external quantum efficiency (EQE) of the solar cell will be achieved with Schottky device structure of ITO/PbS/Al.