Plasmon-enhanced quasi-solid-state dye-sensitized solar cells with metal@Dendron nanoparticles

We have investigated the effects of localized surface plasmons (LSPs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs). Ag and Au nanoparticles (NPs) were prepared by photoreduction in the presence of generation 5 polyester hydroxyl acetylene bis(hydroxymethyl)propanoic acid dendrons (Dendron) as a stabilizer. The plasmon-enhanced DSSCs were achieved by incorporating metal@Dendron NPs into TiO₂ photoanodes. The presence of dendrons prevents the photoelectrons from recombining on the surface of TiO₂ semiconductor and improves the stability of metal NPs. With the addition of Ag@Dendron NPs, the photocurrent and the power conversion efficiency of quasi-solid-state DSSCs increased due to the LSP effect of metal NPs and the barrier effect of dendron, which were confirmed by the increased incident photon-to-photocurrent efficiency and by electrochemical impedance spectroscopy analysis.     

NUCLEATION REACTIONS AND FILM GROWTH OF COPPER ON TiN USING HEXAFLUOROACETYLACETONATE COPPER(I) TRIMETHYLVINYLSILANE

In this work, the nucleation and film growth of copper on TiN chemically treated with WF₆ and air-exposed TiN by chemical vapor deposition(CVD) from hexafluoroacetylacetonate copper¹ trimethyl-vinylsilane, (HFA)Cu(TMVS), was studied. Copper grows as islands of poorly connected grains on air-exposed TiN. In contrast, copper grows as a continuous film with well-connected grains on the surface of WF₆-treated TiN. The effect of TiN surface condition has been examined using Auger electron spectros-copy(AES), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM). On the basis of our experimental observation, and information in the literature, nucleation reaction mechanisms are proposed for the chemical vapor deposition of copper on the two different TiN samples.     

High-temperature polyimide nanofoams for microelectronic applications

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term ‘nanofoam’. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.     

The effect of zirconium oxide coating on the lithium nickel cobalt oxide for lithium secondary batteries

The electrochemical properties of LiNi_0.8Co_0.2O₂ coated with ZrO₂ by three different coating processes (ball-milling, sol-gel method, simple grinding) were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Results showed that the ZrO₂ coating significantly improved the capacity retention of the cathode by suppressing the impedance growth at the interface between electrodes and electrolyte and the best cyclability was obtained in the case of employing the simple grinding for the ZrO₂ coating. On the other hand, the initial capacities of the ZrO₂-coated LiNi_0.8Co_0.2O₂ cathode were slightly decreased.     

Poisoning effect of CO on ethylene polymerization with Ni(II)-diimine/MAO

CO was not a comonomer but an inhibitor in ethylene polymerization catalyzed over [1,2-bis(2,6-diisopropylphenylimino)]acenaphthene nickel(II) dibromide (1)/MAO. The average number of active sites, , and the average rate constant for chain propagation, of the (1)/MAO system was determined using CO inhibition method based on the assumption that two molecules of CO coordinate to each active center. At 0 °C, the average number of active centers, , was increased with the Al/Ni ratio, and , was not influenced by the Al/Ni ratio. Up to Al/Ni ratio of 3000, the average number of active sites was saturated. Single active site was present at the high ratio of Al/Ni and its reactivity with CO is uniform at 0 °C. The maximum average activity was 5262.07 (kg-PE/mol-Ni/atm/hr) and 65.7% of (1) was converted to form active cation complexes at 0 °C and Al/Ni molar ratio of 5000, while 36.5% of (1) was activated at the Al/Ni molar ratio of 250. Above 30 °C, the complicated CO poisoning behavior was observed because the reactivity and stoichiometry of active centers with CO were not uniform and their thermal stability was very poor.     

Effect of solution properties on nanofibrous structure of electrospun poly(lactic‐co‐glycolic acid)

Electrospinning of poly(lactic‐co‐glycolic acid) (PLGA) in chloroform or 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was investigated, focusing on its solution parameters, to develop nonwoven biodegradable nanofibrous structures for tissue engineering. PLGA nanofibers were obtained by electrospinning of 15 wt % PLGA solution and the resulting average fiber diameters were varied with the range of 270–760 nm, depending on solution property. When small amounts of benzyl triethylammonium chloride (BTEAC) was added to the PLGA/chloroform solution, the average diameter was decreased from 760 to 450 nm and the fibers were densely amounted in a straight shape. In addition, the average fiber diameter (270 nm) of nanofibers electrospun from polar HFIP solvent was much smaller than that (760 nm) of nanofibers electrospun from nonpolar chloroform solvent. Therefore, it could be concluded that conductivity or dielectric constant of the PLGA solution was a major parameter affecting the morphology and diameter of the electrospun PLGA fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1214–1221, 2006     

Temperature and grain size dependence of superplasticity in a Zn−0.3wt.%Al alloy

The superplastic deformation behavior of quasi-single phase Zn-0.3 wt. %Al was investigated. A series of load relaxation and tensile tests was conducted at various temperatures ranging from RT (20 °C) to 200 °C. The recently proposed internal variable theory of structural superplasticity was applied. The flow curves obtained from load relaxation tests were shown to consist of contributions from interface sliding (IS) and accommodating plastic deformation. In the case of quasi-single phase Zn-0.3 wt.% Al alloy with an average agrain size of 1 μm, the IS behavior could be described as a viscous flow process characterized by a power index of M_g=0.5. A large elongation of about 1400% was obtained at room temperature and the strain rate sensitivity parameter was about 0.4. Although relatively large-grained (10 μm) single phase alloy showed a high value of strain rate sensitivity comparable to that of fine-grained alloy at very low strain rate range, IS was not expected from the analysis based on the internal variable theory of structural superplasticity at room temperature. As the temperature increased above 100 °C, however, the contribution from IS was observed at a very low strain rate range. A high elongation of ∼400% was obtained in a specimen of 10-μm-grain-size at 200 °C under a strain rate of 2×10⁻⁴/sec. Jointly appointed at Center for Advanced Aerospace Materials (CAAM)     

Shear strength and aging characteristics of 63Sn−37Pb solder bumps with various solder ball and pad sizes

The shear strength and aging characteristics of 63Sn–37Pb solder bumps were characterized with variation in solder ball and UBM pad sizes. The shear strength increased with shorter effective crack size,a _effs which was determined with the solder ball and pad sizes. The shear strength of the solder bumps on Au/Ni/Cu and Ni/Cu did not change significantly with reflow time. Substantial decrease in the shear strength occurred for the solder bumps formed on Au/Ni/Cu with aging treatment, and the shear strength after aging was also related to the bump shape which was determined with the solder ball and pad sizes.     

Biocompatibility of surface treated pure titanium and titanium alloy by<Emphasis Type="Italic">in vivo</Emphasis> and<Emphasis Type="Italic">in vitro</Emphasis> test

In the present study, commercial pure Ti and Ti-6Al-4V alloy specimens with and without alkali and heat treatments were implanted in the abdominal connective tissue of mice. Conventional stainless steel 316L was also implanted for comparison. After three months, their biocompatibility was evaluated byin vitro andin vivo experiments. Surface structural changes of specimens due to the alkali treatment and soaking in Hank’s solution were analyzed by XRD, SEM, XPS and AES. An apatite layer, which accelerates the connection with bone, was formed more easily on the alkali treated specimens than the non-treated specimens. The number of macrophages, which is known to increase as the inflammatory reaction proceeds, was much lower for the alkali and heat treated specimens than for the others. The average thickness of the fibrous capsule formed around the implant was much thinner for the alkali and heat treated specimens than for the others.     

景海高速公路全—强风化花岗岩隧道塌方机理分析与处置

景海高速公路宾房2#隧道洞室围岩主要为中风化花岗岩,顶板为全—强风化花岗岩,具有浅埋、富水、自稳能力极差、遇水流塑性强、施工扰动作用下围岩液化现象明显等特点.该文从地质、施工、自然等多方面对隧道塌方进行分析,并提出一套隧道塌方综合治理措施.采用FLAC3D对治理地表注浆段进行了数值模拟,通过计算结果和现场K31+565...