Synthesis of SnO_2 nanorods from aqueous solution:The effect of preparation conditions on the formed patterns

<正>SnO_2 nanorods were deposited on the Si substrates in an aqueous solution containing both SnCl_4 and CO(NH_2)_2.It is found that different self-assembled patterns of SnO_2 nanorods can be obtained by changing the deposition conditions such as the molar ratio of CO(NH_2)_2 to SnCl_4 and the pretreatment of the substrate.Scattered SnO_2 nanorods,for example,can be changed into flower-like patterns when the molar ratio of CO(NH_2)_2 to SnCl_4 is raised,and well-aligned nanorod arrays can be formed when the pretreatment of the substrate is changed.In addition,some interesting patterns,e.g.tree-like patterns,can also be observed.     

Correlation between thermal conductivity and bond length alternation in carbon nanotubes: A combined reverse nonequilibrium molecular dynamics—Crystal orbital analysis

The thermal conductivity (λ) of carbon nanotubes (CNTs) with chirality indices (5,0), (10,0), (5,5), and (10,10) has been studied by reverse nonequilibrium molecular dynamics (RNEMD) simulations as a function of different bond length alternation patterns (Δr_i). The Δr_i dependence of the bond force constant (k_rx) in the molecular dynamics force field has been modeled with the help of an electronic band structure approach. These calculations show that the Δr_i dependence of k_rx in tubes with not too small a diameter can be mapped by a simple linear bond length–bond order correlation. A bond length alternation with an overall reduction in the length of the nanotube causes an enhancement of λ, whereas an alternation scheme leading to an elongation of the tube is coupled to a decrease of the thermal conductivity. This effect is more pronounced in carbon nanotubes with larger diameters. The formation of a polyene‐like structure in the direction of the longitudinal axis has a negligible influence on λ. A comparative analysis of the RNEMD and crystal orbital results indicates that Δr_i‐dependent modifications of λ and the electrical conductivity are uncorrelated. This behavior is in‐line with a heat transfer that is not carried by electrons. Modifications of λ as a function of the bond alternation in the (10,10) nanotube are explained with the help of power spectra, which provide access to the density of vibrational states. We have suggested longitudinal low‐energy modes in the spectra that might be responsible for the Δr_i dependence of λ. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Mechanical properties and deformation morphologies of covalently bridged multi-walled carbon nanotubes: Multiscale modeling

We formulate a multiscale modeling framework to investigate the deformation morphologies and energetics of covalently bridged multi-walled carbon nanotubes (MWCNTs). The formulation involves extending a previously established quasi-continuum model by incorporating the inter-wall bridging energy density function into the constitutive relations via message passing from fully atomistic simulations. Using the extended numerical model, we studied the mechanical responses of the 10-walled MWCNT with varying inter-wall bridge densities under torsion, bending, and uniaxial compression. Our simulation results show that the presence of inter-wall covalent bridges not only enhances the post-buckling rigidities of the MWCNTs, but also modifies the deformation morphologies and morphology pathways. For bending and uniaxial compression, we constructed in the space of bridge density and applied strain the deformation morphology phase diagram, where three phases, uniformly deformed phase, rippling pattern, and diamond-shaped pattern, are identified and separated by linear phase boundaries. We attribute the deformation phase transitions to the interplay of inter-wall and intra-wall interaction energies. The multiple shape transitions of MWCNTs and the elastic nature of the deformation suggest that MWCNTs can be designed as shape-memory nanodevices with tunable stabilities.     

Thin-Film Zinc/Manganese Dioxide Electrodes

Summary.  Thin-film electrodes allow the manufacturing of flat batteries of variable design. Their electric performance is better than that of customary cells because of a larger contact area between anode and cathode and better utilization of the electrochemically active materials. Bipolar thin-film electrodes for the rechargeable alkaline zinc/manganese dioxide system were assembled using graphite-filled plastics (high-density polyethylene and polyisobutylene). In a different approach, extremely thin electrodes were obtained using 25 μm thick foils made of non-conductive micro-porous polypropylene. The electroactive materials were electrolytically deposited into the pores of the previously metallized foil, providing the required conductive connection through the plastic matrix by themselves. Cycle behavior, cumulated capacities, and energies of batteries with up to two bipolar units were measured. At this early stage of development, batteries based on graphite-filled polymer foils showed better results with regard to storage capacity per unit area and to cycle life. Prototypes based on micro-porous polypropylene suffered from the relatively small fraction of pore volume available for the deposition of active material (about 38%) and from current collector corrosion. Received May 30, 2000. Accepted December 18, 2000     

Alkoxycarbonylation of Allyl Bromide over Palladium Catalyst in Different Reaction Mediums

Supercritical carbon dioxide(scCO2)and its subcritical analogue are now widely used as environ mentally-friendly substitutes of conventional organic solvents in chemical synthesis[1-4]     

Effect of Hydrogen on Catalytic Coupling Reaction of Carbon Monoxide to Diethyl Oxalate

The kinetics of hydrolysis of tetrahydrozoline hydrochloride in aqueous solution at 353, 363 and 368 K in the pH-range from 2.00 to 12.20 has been investigated. The decomposition products have been investigated by HPLC. This revised version was published online in June 2006 with corrections to the Cover Date.     

槲皮素化学修饰碳糊电极吸附溶出伏安法测定痕量铅

建立了用槲皮素修饰碳糊电极测定痕量铅的新方法 ,在 0 .1 0mol L甲酸盐缓冲液 (pH 4.3 )中 ,于 -0 .1 0V(vs.SCE)搅拌富集 ,再在 -0 .70V静止还原 40s后 ,阳极化扫描 ,于 -0 .42V左右获得一灵敏的铅阳极溶出峰。在最佳条件下 ,富集不同时间 ,其二次导数峰电流与Pb2 + 在 1 .0× 1 0 - 8～ 8.0× 1 0 - 7mol L和 2 .0× 1 0 - 9～ 6.0× 1 0 - 8mol L两个范围内呈线性关系 ,检出限为 8.0× 1 0 - 1 0 mol L(S N =3 )。同时初步探讨了电极反应机理。     

Sm2O3对Ni／sepiolite甲烷化催化剂的影响

采用浸渍法制备了Ni/sepiolite及Ni-Sm/sepiolite催化剂并测定了催化剂的CO甲烷化活性，采用抗热实验，XPS及CS2中毒等手段研究了钐对Ni/sepiolite催化剂的影响，结果表明，加入Sm2O3提高了Ni/sepiolite催化剂的甲烷化活性，催化剂热稳定性及抗毒能力，降低了镍原子的电子结合能。