One step NaBH_4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells : Synthe sis and characte rization

The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R(f-CB),functionalized multi-walled carbon nanotubes(f-MWCNT),and mesoporous carbon(PC-Zn-succinic)by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction(EOR)for direct ethanol fuel cell(DEFC).It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion.The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping,which was relevant to the efficiency of the catalysts.Moreover,the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding.The activity and stability for ethanol electrooxidation reaction(EOR)were investigated using cyclic voltammetry and chronoamperometry,respectively.The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction.Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR.Moreover,the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.

Microhardness and Biocompatibility of Silicon Nitride Ceramic Developed for Dental Applications

Silicon nitride (Si3N4) ceramic is an attractive material for dental applications, especially used as a dental core material, due to its unique properties including high fracture toughness, high strength, high wear resistance and non-cytotoxicity. In this study, the Si3N4 ceramic was fabricated by a non-pressure sintering technique at a relatively low sintering temperature of 1650℃ in nitrogen atmosphere. Borosilicate glass and 5 wt% ZrO2-added borosilicate glass were used for coating on the Si3N4 core surface because of their compatibility in thermal expansion, high chemical resistance and bio-inert. The specimens were then fired in electric tube furnace at 1100℃. The Vickers microhardness of borosilicate glass and 5 wt% ZrO2-added borosilicate glass veneering materials were measured and compared with the commercial dental veneer porcelain as a control (VITA VMK 95). The cytotoxicity of the Si3N4 ceramic and the veneering materials were tested by MTT assay, using human gingival fibroblasts (HGF) and periodontal ligament fibroblasts (HPDLF). The results indicate that the Si3N4 ceramic and Si3N4 ceramic veneered with borosilicate glass or 5 wt% ZrO2-added borosilicate glass veneering materials tested in this study are not toxic to oral tissue and can be used to produce dental prostheses.

PDMS Microchip Capillary Electrophoresis for Determination of Thiol Compounds

A fast and sensitive method for the determination of thiol compounds including homocysteine, glutathione and N-aeetyl-l-cysteine using microchip capillary electrophoresis was proposed. The mierochip was made from an elastomerie material-poly （dimethylsiloxane） （PDMS）. The microehip configureation consists of a top layer of PDMS containing of injection and separation channels, reservoirs and a gold microwire sealed with a bottom layer of PDMS. A gold microwire was used as the working electrode and platinum mierowire was used as counter electrode. The pulsed amperometric detection （PAD） was applied for determination of these thiol compounds. The experiments were carried out with 20 mM MES and 1 mM SDS buffer （pH 6.0）. In order to optimize the conditions, detection and separation potential, pH buffer, injection time, and PAD parameters were studied. Homocysteine, glutathione and N-aeetyl-L-cysteine can be separated and detected in less than 2 rain at the detection potential of ＋0.8 V, separation potential of ＋1200 V, and injection time of 20 s, with good reproducibility and sensitivity.

Extraction of Palladium from Acidic Chloride Media into Emulsion Liquid Membranes using LIX 984N-C^®

The extraction of palladium from hydrochloric acid solutions into emulsion liquid membranes (ELMs) using LIX 984N-C as the extractant was investigated. The influential factors and the total capacities of palladium extraction were determined by a batch method. The behavior of palladium extraction by ELMs under the operational conditions-pH of the external feed phase, surfactant and extractant concentration, internal stripping phase concentration, treat ratio and agitation speed were reported. Using LIX 984N-C, palladium was effectively extracted from the external acidic chloride feed phase into the internal receiving phase of W/O emulsions. More than 92% of palladium could be extracted at a feed pH of 2 with 3% Span 80, 9% LIX 984N-C and 7M HCl at a stirring speed of 300 rpm.

Methane partial oxidation over NiO-MgO/Ce0.75Zr0.25O2 catalysts

Methane partial oxidation （MPO） is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H2/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce0.75Zr0.2502 （CZO） supported catalysts were prepared via the co-impregnation （C） and sequential incipient wetness impregnation （S） methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO2 over CZO support led to the difficulty in reducing NiO to active Ni~ and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO （S） catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750℃. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature.