Advanced Materials Research Vols. 123-125

Abstract: A new type of EVA-g-PU/OMMT nanocomposites was synthesized through the method of chemical modification and melt intercalation. FTIR testing showed that the PU prepolymer was grafted on EVA main chains successfully. The structures of EVA-g-PU/OMMT nanocomposites were characterized by X-ray diffraction (XRD) and by high-resolution transmission electron microscopy (HRTEM). The enhanced storage modulus of EVA-g-PU/OMMT nanocomposites was characterized by dynamic mechanical analysis (DMA). The thermal stabilities of EVA/clay nanocomposites were also studied by thermal gravimetric analysis (TGA). Mechanical testing showed that the tensile strength and tear strength of EVA-g-PU/OMMT nanocomposites were far superior to pure EVA.

Abstract: The synthesis of uniform and monodispersed magnetic and optical nanocrystals has received much attention in recent years due to the size-dependent physicochemical properties. In this study, we have demonstrated a general approach for the synthesis of size-tunable ferrite and gold nanocrystals and their nanocomposite. The monodispersed magnetite nanocrystals were obtained by thermal decomposition of iron-oleate complex in a high boiling point solvent in presence of oleylamine and oleic acid. The size of magnetite nanocrystal can be tuned from 7 – 11nm by changing the amount of iron-oleate complex. The other key parameters such as temperature, amount of capping agents, types of solvent were also discussed. This synthetic procedure could also apply to synthesis other type of ferrite nanocrystals. When Mn-acetate was partially substituted for iron-oleate in a 1:2 ratio in the same reaction conditions as in the synthesis of Fe3O4, monodispersed MnFe2O4 nanocrytals with 14nm could be obtained. Except those magnetic nanocrystals, we also synthesized various sizes of monodispersed gold nanocrystals by reducing HAuCl4 in presence of t-butylamine-borane and oleylamine. By varying the reaction temperature, the particle size could be well-tuned from 2nm to 8nm with the characteristic surface plasmon absorption between 510 and 520 nm. For Fe3O4/Au composite, it was prepared via the decomposition of iron-oleate over the surface of the Au nanoparticles. The mean size of the Fe3O4/Au nanocomposite was ∼17 nm which shows a saturation magnetization of 46.92 emu/g and absorption peak at 512nm. These composites with both magnetic and optical properties would make them very promising in the fields of biomedine and environment.

Abstract: A detonation method for synthesizing carbon-encapsulated metal nanoparticles (CEMNPs) is reported. The composite precursors containing various nitrate dissolved in absolute ethanol is ignited by a nonelectric detonator in nitrogen gas in an explosion vessel. The material characteristics of these nanoparticles are then examined with the XRD,TEM,EDX and RS. The results show that the composite particles whose coating shell were graphite carbon could be dispersed finely. The core of nanoparticles were composed of iron, cobalt and nickel crystal to that of the above explosive precursors.

Abstract: The magnetic photocatalysts can provide both a high specific surface area and an alternative for recovering used catalyst from treated water by the application of a magnetic field. In this study, the Fe3O4 nanoparticles were synthesized by co-precipitation. After chemical co-precipitation of ferric and ferrous solution under alkaline condition, the suspension of magnetite nanoparticles were then mixed with TEOT (Titanium (Ⅳ) ethoxide) for sol-gel coating. The separated MPCs (magnetic photocatalyst nanoparticle) were then dried and calcined in 400oC. Magnetic properties of MPCs were identified by superconducting quantum interference device magnetometer (SQUID). The bactericidal ability of synthesized MPCs was evaluated by counting the residual numbers of E. coli after irradiation under a light intensity of 1.0 mW/cm2 at 365 nm. The results show that the MPCs were both anatase and had good crystallinity with clear peaks and insignificant noises after calcination. The SQUID test also reveals that calcination only affects the magnetic susceptibility of the MPC nanoparticles slightly (< 8%). The bactericidal ability of the synthesized MPCs was compared with the commercial TiO2 nanoparticle DegussaTM P25; P25 provided a faster inactivation rate for E. coli in water than MPCs did at the same dosage. The calculated photocatalytic bactericidal rate by P25 is about 3.6 times faster than that by MPCs synthesized in this work. However, the bactericidal rate of magnetic TiO2 synthesized in this work was 5 times than that of other MPCs in the literature. The particles size and surface area of MPCs from this work were about 135 nm and 210 m2/g, respectively. The MPCs from this work have much smaller size and larger surface area; hence there are more active sites for bactericidal reaction.

Abstract: Closed form expressions for the Cosserat constants for circular cell honeycombs are derived using a combination of non-dimensional analysis and numerical analysis. The expressions for the four in-plane Cosserat compliances, which are the plane strain bulk compliance, the shear compliance, the micropolar compliance and the bending compliance are derived in terms of the cell size, cell thickness and the linear elastic properties of the cell wall material. Numerical analyses are performed to verify the accuracy of the derived constants by considering different combinations of geometric parameters and different numbers of cells for the honeycombs. It is shown that the closed form expressions are an accurate representation of the Cosserat constants of circular cell honeycombs.

Abstract: Many methods had been developed to disinfect or sterilize the medical equipment or hospital environment for controlling the spread of nosocomial pathogens. This study was aimed to evaluate the effect of titanium dioxide (TiO2) thin film on preventing nosocomial infection. Firstly, TiO2 thin film was prepared by using the modified impregnation method and further analysis by field-emission scanning electron micrographs and X-ray diffractometer. The nano-size and Anatase crystal structure were confirmed. By using visible light activation of TiO2 thin film for 30 min, the inhibition of Enterococcus faecalis, Streptococcus bovis, Streptococcus agalactiae, and Staphylococcus aureus by TiO2 thin film treatment were 27.4%, 73.3%, 56.6%, and 9.4%, respectively. In addition, several important Gram negative bacteria causing nosocomial infection were also investigated. The inhibition rate of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli were 32.5%, 31.3%, and 22.4%, respectively. The results revealed that TiO2 thin film activated by visible light may be useful for decreasing nosocomial infection.

Abstract: The nosocomial infections caused by opportunistic pathogen Acinetobacter baumannii was increasing in recent years. It was known that the attachment of A. baumannii on solid surface was a key factor for infection. This study was conducted to evaluate the inhibitory effect of titanium dioxide (TiO2)/Ag thin film on A. baumannii. In this study, TiO2 thin films were firstly prepared by using the modified impregnation method, then TiO2/Ag thin films were prepared by using the spin-coating with 5000 ppm Ag+. The TiO2/Ag thin film was analyzed by field-emission scanning electron micrographs and X-ray diffractometer. The nano-size and Anatase crystal structure were confirmed. Twenty clinical A. baumannii isolates were examined for the bactericidal effect of TiO2/Ag thin film either in the dark or under visible light activation for 20 min. The inhibition efficiencies of TiO2/Ag thin film under visible light on these 20 isolates ranged from 41% to 90%. The effects of TiO2/Ag thin film in the dark were slightly lower than visible light-activated group. Our results suggested that coating of TiO2/Ag on solid surface in hospital environment might be helpful for the prevention of nosocomial A. baumannii infection.

Abstract: The La/TiO2 photocatalyst was prepared by lanthanum into TiO2 structure in a sol-gel process. The catalyst was characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), ESCA, and Brunauer Emmett Teller (BET) analyses. Photocatalytic activities of the supported catalysts were examined through decomposition process of azo-dye Acid Yellow 17 solution under UV irradiation. The results showed that the particle size of TiO2 is about 20 nm, and the particle of La/TiO2 is about 10 nm. The crystal structure is mainly in anatase phase, the contents of the rutile phase increase with the increase of the amount of doped lanthanum. The adsorption capacity of La/TiO2 catalysts increases with lanthanum dosage in the acidic solution. The contribution of actual photodecomposition was determined by desorption process, after the photocatalytic reaction. In the acidic solution, better photodecomposition efficiency is achieved than in the neutral or alkaline solution. The experiments demonstrated that the optimum doping of La at 10 mol %, the maximum photodecomposition in dye concertration at 15 mg L-1 and photocatalytic dosage at 0.75 g L-1, achieving the highest effect.

Abstract: The post-buckling of the functionally graded composite plate under thermal environment with aerodynamic loading is studied. The structural model has three layers with ceramic, FGM and metal, respectively. The outer layers of the sandwich plate are different homogeneous and isotropic material properties for ceramic and metal. Whereas the core is FGM layer, material properties vary continuously from one interface to the other in the thickness direction according to a simple power law distribution in terms of the volume fractions. Governing equations are derived by using the principle of virtual work and numerical solutions are solved through a finite element method. The first-order shear deformation theory and von-Karman strain-displacement relations are based to derive governing equations of the plate. Aerodynamic effects are dealt by adopting nonlinear third-order piston theory for structural and aerodynamic nonlinearity. The Newton-Raphson iterative method applied for solving the nonlinear equations of the thermal post-buckling analysis

Abstract: As a kind of semiconducting and promising material, ZnO has been extensively used in dye-sensitized solar cells (DSSCs). Quantum dot sensitized solar cells (QDSSCs) has more potential to increase the efficiency of solar cells compared with DSSCs. Here we developed a simple and effective way to fabricate ZnO porous plate films by electrochemical deposition and anneal in air on ITO-coated glass substrates. CdS quantum dots were attached to the surface of the porous plate films by chemical bath deposition technique. Quantum dot-sensitized ZnO porous plate films solar cells exhibited short-circuit current ranging from 0.22-0.57mA/cm2 and open-circuit voltage of 0.42 -0.57V when illuminated with 100 mW/cm2 simulated AM 1.5 G irradiation.