Preparation and characterization of electroplated amorphous gold-nickel alloy film for electrical contact applications

A process for electroplating amorphous gold-nickel alloy with the atomic ratio of unity was developed. The plating bath was prepared by adding potassium cyanoaurate(I) into a known plating bath which produces amorphous nickel-tungsten alloy. At a sufficiently high gold concentration, the alloy deposit did not contain any tungsten. The amorphous nature of the Au-Ni alloy produced in the new bath was confirmed by using TEM and THEED. Hardness, resistivity, and contact resistance of this new alloy were determined, and the results are discussed for applications as an electrical contact material.     

The Wulff Shape of Alumina: II, Experimental Measurements of Pore Shape Evolution Rates

The rate at which a facetted tetragonal cavity of nonequilibrium shape approaches a cubic equilibrium (Wulff) shape via surface diffusion was modeled. The shape relaxation rate of a facetted stretched cylinder was also modeled. For the first geometry, only an approximate solution based on linearizing the mean potential difference between the source and sink facets was obtained. For the stretched cylinder, both an approximate and an exact solution can be obtained; the approximate solution underestimates the evolution rate by a factor of ∼2. To assess the applicability of the models, nonequilibrium shape pores of identical initial geometry (∼20 μm × 20 μm × 0.5 μm) were introduced into (0001), {10[Onemacr]2}, {1120}, and {100} surfaces of sapphire single crystals using microfabrication techniques, ion-beam etching, and hot pressing. The large (∼20 μm × 20 μm) faces of the pore are low-index surfaces whose nature is dictated by the wafer orientation. A series of anneals was performed at 1900°C, and the approach of the pore shape to an equilibrium shape was monitored. The kinetics of shape evolution are highly sensitive to the crystallographic orientation and stability of the low-index surface that dominates the initial pore shape. The measured variations of the pore aspect ratio were compared to those predicted by the kinetic model. The observations suggest that when the initial bounding surface is unstable, shape relaxation may be controlled by diffusion. However, surface-attachment-limited kinetics (SALK) appears to play a major role in determining the pore shape evolution rate in cases where the initial bounding surfaces have orientations that are part of the Wulff shape.     

Kinetics of Enthalpy Relaxation at the Glass Transition in Ternary Tellurite Glasses

The kinetics of enthalpy relaxation (recovery) at the glass transition in x K₂O·(20− x )MgO·80TeO₂ glasses has been examined from heat capacity measurements using differential scanning calorimetry to clarify the features of the structural relaxation in ternary TeO₂-based glasses. Ternary glasses such as 10K₂O·10MgO·80TeO₂ show high thermal resistance against crystallization compared with binary glasses. The degree of fragility m estimated from the activation energy for viscous flow E _η and the glass transition temperature T _g is m = 55–62, indicating a fragile character in TeO₂-based glasses. Large heat capacity changes of 43.1–48.2 J·mol⁻¹·K⁻¹ are also observed at the glass transition. The activation energy for enthalpy relaxation Δ H is evaluated from the cooling rate dependence of the limiting fictive temperature, and values of Δ H = 897–1268 kJ·mol⁻¹ are obtained. Negative deviation from additivity in Δ H is also observed. Values of the Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from Δ H and T _g are 0.33–0.42 K⁻¹. It has been proposed that ternary glasses have more homogeneous and constrained glass structure compared with binary glasses.     

Cathodic performance of LiMn1−xMxPO4 (M = Ti, Mg and Zr) annealed in an inert atmosphere

To improve the cathodic performance of olivine-type LiMnPO₄, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn_1−xM_xPO₄ (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO₄ was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn₂P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn_0.99Mg_0.01PO₄/C was 146 mAh/g at 0.1 mA/cm² and 125 mAh/g even at 2.0 mA/cm².     

Temperature- and pH-responsive photosensitization activity of polymeric sensitizers based on poly-N-isopropylacrylamide

We previously reported that a copolymer consisting of N-isopropylacrylamide (NIPAM) and benzophenone (BP) units, behaves as a photosensitizer showing temperature-controlled oxygenation activity in water (J. Am. Chem. Soc.2006, 128, 8751). This polymer shows a heat-induced oxygenation enhancement at low temperature region (5-20 °C), while showing a heat-induced oxygenation suppression at high temperature region (20-60 °C), resulting in an off-on-off activity profile against the temperature window. This is driven by a heat-induced phase transition of the polymer from coil to micelle and then to globule states. In the present work, effects of adding an amine component (N-[3-(dimethylamino)propyl]acrylamide: DMAPAM) to the polymer on the sensitization activity were studied, where the relationship between the phase transition behavior and the activity was clarified by several spectroscopic analyses. The polymers, poly(NIPAM_x-co-BP_y-co-DMAPAM_z), show activity controlled by temperature and pH. The off-on-off activity profile shifts to higher temperature with a pH decrease. This is because protonation of the DMAPAM units leads to an increase in the polymer polarity and, hence, the polymer aggregates at higher temperature. In addition, increase in the DMAPAM content of the polymer leads to further shift of the activity profile. In contrast, at pH < 8, no activity enhancement is observed because complete protonation of the DMAPAM units suppresses polymer aggregation.     

Electrochemical insertion and extraction of lithium-ion at nano-sized LiMn2O4 particles prepared by a spray pyrolysis method

Nano-sized LiMn₂O₄ particles were prepared at 1023 K by electrospray pyrolysis in which they were directly deposited on a Pt substrate in gas phase. Cyclic voltammetry gave very sharp and symmetrical redox peaks at ca. 4.0 and 4.1 V vs. Li/Li⁺ owing to the insertion and extraction of lithium-ion at LiMn₂O₄. However, the redox peaks broadened and their peak separation in an electrode potential increased when aggregated nano-sized LiMn₂O₄ particles were used. In Nyquist plots, a semi-circle due to lithium-ion transfer resistance appeared at potentials above 3.90 V. The values of the lithium-ion transfer resistances were small for dispersed nano-sized LiMn₂O₄ particles. On the other hand, the lithium-ion transfer resistances increased and the Warburg impedance became obvious as the nano-sized LiMn₂O₄ particles aggregated. These results clearly indicate that the apparent rapid diffusion of lithium-ion can be attained using well-dispersed nano-sized particles of electroactive materials.     

Removal of proteins from natural rubber with urea and its application to continuous processes

The removal of proteins from natural rubber through a batch process was studied by the incubation of the rubber latex with urea in the presence of sodium dodecyl sulfate. Under suitable conditions, the total nitrogen content of deproteinized natural rubber (DPNR) decreased from 0.38 to 0.02 wt % after incubation for 10 min; this was similar to that of the rubber deproteinized with a proteolytic enzyme for 12 h. For applications, continuous incubation and centrifugation were individually investigated by the use of a semicircular channel and a continuous centrifuge, respectively, to scale up DPNR preparation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microfabrication of U-Shaped Grooves on the Surface of BaO–TiO2–GeO2 Glass by YAG Laser Irradiation and Selective Chemical Etching

A combination technique of Nd:YAG laser (wavelength: 1064 nm) irradiations and chemical etchings was applied to fabricate microsize U-shaped grooves on the surface of CuO-doped BaO–TiO₂–GeO₂ glass, and chemical etching behaviors were examined by using a confocal scanning laser microscope. Continuous-wave Nd:YAG lasers with a power of 0.7–0.8 W were irradiated onto the glass surface and scanned at a speed of 10 μm/s, inducing structural modified lines with refractive index changes. The chemical etching rates for the refractive index changed lines in a nitric acid solution (1 N HNO₃) were larger than those for the base glass (nonirradiated part). The etching profile was changed gradually from W-shaped to U-shaped grooves with increasing etching time. The sharp bending lines with an angle of 150° and the cross-linked lines were also smoothly etched. The U-shaped grooves with a surface covered by nonlinear optical Ba₂TiGe₂O₈ crystals were formed by the crystallization of etched samples. This study proposes that the patterning of microchannels with optical functional surfaces is possible on the glass surface using the present technique.     

Electrochemical reduction of carbon dioxide to ethylene with high Faradaic efficiency at a Cu electrode in CsOH/methanol

The electrochemical reduction of CO₂ with a Cu electrode in CsOH/methanol-based electrolyte was investigated. The main products from CO₂ were methane, ethylene, ethane, carbon monoxide and formic acid. A maximum Faradaic efficiency of ethylene was 32.3% at −3.5 V vs. Ag/AgCl saturated KCl. The best methane formation efficiency was 8.3% at −4.0 V. The ethylene/methane current efficiency ratio was in the range 2.9–7.9. In the CsOH/methanol, the efficiency of hydrogen formation, being a competitive reaction against CO₂ reduction, was depressed to below 23%.