Advanced Materials Research Vols. 233-235

Abstract: PolymethylMethacrylate (PMMA) composites with different weight content of organic rectorite (OREC) are prepared via melt blending. The results of X-ray diffraction (XRD) show that the layer distance of OREC is much larger than that of the pristine rectorite. SEM images reveal that the OREC filler has been well dispersed in matrix. With the addition of OREC, Bending modulus increased obviously. Ortho-positronium (o-Ps) lifetimes show that the free volume sizes of PMMA/OREC composites are larger than those of the PMMA matrix. The relationship between the atomic-scale free volume size and mechanical properties is preliminarily discussed in this work.

Abstract: Molecular dynamics (MD) simulations have been used to investigate the interlayer structure of water saturated organoclays. The basal spacing values of cetyltrimethylammonium (CTMA) intercalated montmorillonite (CTMA-Mont) in dry and water saturated states were detected using XRD. Then the results were compared with simulation results of dry CTMA-Mont. The MD simulations show that the CTMA cations form layer structures on siloxane surface and aggregate in the interlayer space. Water molecules can access part of the siloxane surface and form H-bonds with surface oxygen atoms by donating one or two of the hydrogen atoms. Thus, the water molecules close to the surface have a preferred orientation with the dipole pointing towards the surface, while in the interlayer space, the water molecules aggregate to form large clusters. The H-bonds between surface oxygen and water molecules are shown to be slightly weaker than those between water molecules. Although water molecules within interlayer space can form strong H-bonds as in bulk water the number of H-bond for each water molecule is reduced. Our results indicate that MD simulations represent a useful tool for exploring the microstructure of water saturated organoclays.

Abstract: The density functional theory (DFT) is used to compute the ground-state geometries of naphthoquinone derivatives, and lowest singlet excited-state geometries of them have been investigated by the singles configuration interaction (CIS) method. The absorption and emission spectra are calculated by time-dependent DFT (TDDFT) on the basis of the ground- and excited-state geometries, respectively. Our calculations are in good agreement with the available experimental results. The calculated results show that with the introduction of hydroxyl the red-shift was found in the absorption and emission, and the range of spectra reach the visible region. Furthermore, in the absorptions electron transition type was identified from the point-view of molecular orbitals. Study of the effect of hydroxyl and site on spectra can provide the helpful information on further designing molecular devices.

Abstract: Aminopropyl-functionalized silica (NH₂-SiO₂) was obtained via a sol-gel process using tetraethoxylsilicate (TEOS) and aminopropyltriethoxysilane (APTES). Aminopropyl group contained silica was further modified with formaldehyde to achieve a novel organic group modified silica, denoted as CH₂O-SiO₂. Using CH₂O-SiO₂ as support to prepare surported Pd catalyst (denoted as Pd/M-SiO₂), small Pd nanoparticles (1-2 nm) were fabricated on CH₂O-SiO₂ surport. Hydrogenation of acetylene is used as probe reaction to evaluate the catalytic performance of Pd/M-SiO₂. The results indicate that Pd/M-SiO₂ exhibits unique catalytic property, which the selectivity of ethylene increases with the increase of acetylene conversion. In-situ DRIFTS spectra of CO adsorption show that the organic groups presented on the silica affect the electronic property of the very small Pd nanoparticles, which causes the change of reaction paths of hydrogenation of acetylene over Pd/M-SiO₂ compared with traditional supported Pd catalyst.

Abstract: This paper analyses the advantages of spreading self-insulation wall, which uses the energy-saving fired hollow bricks as the major structure, in cold region rich in natural resources of loess. Through calculating the thermal parameters, concluding that this kind of wall can meet the national requirement of saving-energy by 50%, even can meet the national requirement of saving-energy by 65% to limit the shape coefficient of building in some region.

Abstract: The nanocrystalline WC-10Co hard alloys with high density (97.5% T.D.) have been prepared by use of mixing and explosion compaction technology and the average crystalline size is less than 100 nm. The microstructure analysis shows that, the particle size of the mixing powders is less than 200nm and that of the explosive compaction billet is even fine about 100nm. If explosive speed of any explosive is either big or small, we can not get density billets because the initial density of mixing powders is too low. If using secondary explosive compaction process (low-speed explosive Ammonium Nitrate 280g + high-speed explosive TNT 200g), we can get about 97% (maximum density of 97.58%) of the theory density of bulk nanocrystalline WC-10Co hard alloys.

Abstract: Recently, "Low carbon" is attracting more attention all over the world. Based on the foreign two typical low carbon community British Bed ZED, Germany Vauban community, using research, systematic analysis and other methods, from the success of the two communities in low carbon planning , the paper summarized: the public participation; Urban lands applications; The full utilization of energy; Land reasonable layout; Road traffic arrangement and so on. This article can be a very good reference for our low carbon community planning.

Abstract: Nanostructured ZrO₂ was prepared successfully by mechanically activated solid state reaction. The structural and microstructural of products were monitored using X-ray powder diffraction (XRD), transmission electron microscopy (TEM). The effects of ball milling speed and calcined temperature on products were monitored by XRD. The results of XRD show that the most suitable ball milling speed is 150r/min, and the calcined temperature is 600°C. TEM images show that ZrO₂ particles prepare at heating rate of 5°C/min have several advantages in the morphology, spherical shape, narrow size distribution with no hard aggregation, and the particle size is about 15 nm, and at the heating rate of 2.5°C/min, a network structure ZrO₂ can be prepared for the first time.

Abstract: A convenient method to synthesize starch/lactic acid copolymer was studied in this work. Copolymer of starch graft with lactic acid (LA) was directly prepared by reaction of cornstarch with lactic acid in sodium hydroxide (NaOH) aqueous solution as a catalyst. The product was characterized by IR and WAXD, and the good adhesion between the two components has been observed by SEM. The results showed that the highest grafting degree could reach 33.60% when the graft copolymerization was carried in 0.40 mol·L^-1 NaOH aqueous for 9 h at 90°C with the 1: 5~6 ratio of starch and lactic acid.

Abstract: The flake-like silver nano-particles were prepared by reducing silver nitrate with hydrazine hydrate in the sodium dodecyl benzene sulfonate (SDBS) and Polyvinyl pyrrolidone (PVP) complex solution. The as-received silver powders were characterized by SEM, EDS, TEM and XRD methods. The effects of SDBS and PVP with Ag⁺ ligand on the preparation of flake-like shape were analyzed. The results provide evidence that the SDBS-Ag⁺ ligand play a limiting template role during the silver growth and leading to the formation of flake-like silver consequently.