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41.
Corrosion experiments on iron were performed in boiling 55% Ca(NO3)2 solution (115°C) to elucidate the kinetics of intergranular corrosion (IGC) of iron. After the time-current curve was recorded for the specimen exposed for 30 h to the IGC test solution at 1000 mVSHE (passive region), the specimen was examined for IGC by optical microscopy. The current-time curves and optical micrographic observations suggested that the kinetics of IGC of iron is based upon the periodic passivation-grain boundary dissolution process. IGC occurs mainly between the first passivation and the second repassivation periods. Average current density during this period can be regarded as a measure of the susceptibility to IGC. The excess dissolved nitrogen or nitride at the grain boundaries does not lead to a definite IGC. 相似文献
42.
Jeong Soo Kim Seung Won Lee Hyung Mun Kim Dae Kon Oh Heung Ro Choo Dong Hoon Jang Hong Man Kim Kwang Eui Pyun Hyung Moo Park 《Journal of Electronic Materials》1995,24(11):1697-1701
We have investigated the effect of diethylzinc (DEZn) on the lattice constant and the growth rate of InGaAs. Introducing DEZn
for p-type doping induces the contraction of lattice constant and the reduction of growth rate compared to undoped InGaAs.
Depletion of indium is responsible for these effects. These effects are reduced at lower growth temperatures or at lower growth
pressures. From the observed effects of the growth temperatures and the growth pressures on the contraction of the lattice
constant, it is concluded that depletion of indium occurs in the gas phase. 相似文献
43.
The hydrogen evolution reaction (h.e.r.) at a 10 wt % palladium-dispersed carbon (Pd/C) electrode in 0.1 m NaOH solution has been investigated with reference to that on carbon (Vulcan XC-72) and palladium foil electrodes by analysing the a.c.-impedance spectra combined with cyclic voltammograms. From the coincidence of the maximum charge transfer resistances and the minimum hydrogen evolution resistances for the h.e.r. at the respective electrode potential for the Pd/C, carbon and Pd foil electrodes, it is suggested that the h.e.r. at the Pd/C electrode takes place along with the absorption and diffusion of hydrogen above –1.10 V vs SCE, whereas the former dominates over the latter below –1.10V vs SCE. In the case of the Pd foil electrode the transition of absorption and diffusion to evolution occurs at –0.96V vs SCE. In contrast to the Pd/C and Pd foil electrodes the h.e.r. occurs strongly at the carbon electrode below –1.20V vs SCE. The hydrogen evolution overpotential on the Pd/C electrode is decreased by 0.10 V in comparison to the carbon electrode due to the larger electrochemical active area of the finely dispersed Pd particles. 相似文献
44.
Hydrogen trapping at spheroidized and elongated sulphidic inclusions-matrix interfaces in mild steel
The present work is concerned with those factors which determine the hydrogen trapping at the interfaces between spheroidized and elongated sulphidic inclusions, and matrix in mild steel by using gas-phase charging and electrochemical detection techniques. Three kinds of specimens A, B and C were prepared from the calcium-treated mild steel by water quench from 950°C, and from the ordinary mild steel by water quench from 950 and 1150°C, respectively. Specimen A was characterized by the interface between the spheroidized sulphidic inclusions and matrix, but the specimens B and C were characterized by the elongated sulphide-matrix interface. The values of time-lag decreased with increasing hydrogen input pressure for the specimens A, B and C. The results indicated that the defects produced at the interfaces act as saturable trap sites for hydrogen. The hydrogen trap density and binding energy were obtained from the plot of [(tT/tL)–1] vs. . The trap densities for the specimens A, B and C were found to be about 5.0 × 10?8, 2.1 × 10?7 and 5.0 × 10?7 mol cm?3, respectively. The trap-binding energy was determined to be ?(56.4 ± 1.1) kJ mol?1 for the specimens A, B and C as well. The experimental results indicated that the nature of the interfaces is determined by the number of defects produced in the interfaces per unit volume, regardless of the inclusion shape. The defects distributed in the interfaces included namely microvoids and water-quench-created dislocations which act as deep trap sites for hydrogen. 相似文献
45.
Universal one‐pot,one‐step synthesis of core–shell nanocomposites with self‐assembled tannic acid shell and their antibacterial and catalytic activities 下载免费PDF全文
Facile synthesis of metal@polymer nanocomposites were achieved using self‐assembled tannic acid (TA) shells without crosslinkers. The TA shell was assembled under mildly alkaline conditions in reaction time of 20 min under constant vortexing. Universal synthesis method was demonstrated by the synthesis of Ag@TA and Au@TA nanocomposites. We propose that the shell formation is due to TA undergoing oxidative self‐polymerization to poly(tannic acid) or a supramolecular aggregate of oxidized TA held together by charge transfer, hydrogen bond, and π–π interactions, similar to dopamine polymerization. Gibbs free energy calculations suggest that polymerization is energetically favorable. Synthesized Ag@TA exhibited antibacterial functionality with Escherichia coli minimum inhibitory concentration of 100 µg mL?1 up to 48 h. The population of E. coli was also reduced by 99% within 5 h when incubated with 100 µg mL?1 of Ag@TA nanocomposite. Au@TA also functions as a reduction catalyst. It reduces 4‐nitrophenol to 4‐aminophenol in the presence of NaBH4 with a rate constant of k = 0.63 min?1 μmol?1. For comparison, using Au nanoparticles yields a rate constant of 0.14 min?1 μmol?1. The ease of synthesis renders the nanocomposites superior to others, with potential for large‐scale application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45829. 相似文献
46.
Gook Chan Cha Sukmin Lee Jeom Sik Song Jong Kwon Kim Kyung Hoon Kim Mu Seong Mun Hyoung Soon Youn Do Gi Pyun Yoon So Choi 《应用聚合物科学杂志》2006,100(4):2750-2758
The purpose of this study is to prepare new polyurethane gels that can be used as stress‐ or pressure‐distributing materials, particularly by being combined with selective plasticizers for medical or clinical applications. Because low‐molecular‐weight plasticizer molecules in polymer gels intrinsically tend to migrate to the surface of the gels by the so‐called entropy effect in polymer miscibility, the stress‐distributing function may decrease gradually after a certain amount of time. Correspondingly, both the chemical nature of the plasticizer and polymer gels and the compatibility between the polymer segments and plasticizer should be deliberately considered as important factors in determining the thermophysical properties and stress‐distributing performance of polymer gels. New polyurethane gels comprising separated phases of soft and hard segments, the glass‐transition temperature of which was around the ambient temperature, were prepared, and selective plasticizers were combined to obtain an optimized formulation of gels for stress‐relieving properties. The glassy‐to‐rubbery transition of semicrystalline hard segments occurring around the ambient temperature caused the rearrangement of chain conformations, leading to the reduction of the pressure applied to the surface; this indicated that the pressure buildup or loss was somewhat related to the heat regulation by thermal absorption and release in the phase‐transition range. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2750–2758, 2006 相似文献
47.
The roles of adsorbed hydroxyl radicals, OH, at a high temperature and adsorbed hydrogen atoms, H, in an acidic solution were
investigated in the electrochemical reactions on Pt electrode by using potentiodynamic polarisation experiment, cyclic voltammetry
and constant-potential electrolysis combined with UV/VIS analysis. From the analysis of the polarisation curves obtained from
Pt electrode in a 0.185 M H3BO3 solution at 473 K, it was found that the reducing capability of dissolved hydrogen is significantly enhanced due to the increases
of the mass transfer and the electron transfer rates. Especially, it is suggested that the stable Pt-OHad plays a significant role in the passivation reaction in the potential range from 0.60 to 0.75 VSHE. From the analyses of the experimental results for the electrochemical reduction of UO22+ ions on Pt surface in a 1.0 M HClO4 solution, it is recognised that the reduction reaction of UO22+ to U4+ ions is strongly dependent on the hydrogen atoms adsorbed on Pt electrode (indirect reduction of UO22+) as well as on the electrons transferred from Pt electrode (direct reduction of UO22+). In addition, the reduction mechanism of UO22+ ions involved in Pt-Had is also proposed. 相似文献
48.
Sung-Woo KimSu-Il Pyun 《Electrochimica acta》2002,47(17):2843-2855
Lithium transport through a sol-gel derived LiMn2O4 film electrode was theoretically investigated by analyses of the potentiostatic current transient and the linear sweep voltammogram in consideration of the interactions between lithium ions by using Monte Carlo simulation. The anodic current transients experimentally measured on the film electrode ran with the slope of logarithmic current with logarithmic time flatter than −0.5 in the early stage, and then did in an upward concave shape in the time interval between tT1 and tT2. The linear sweep voltammograms experimentally measured on the film electrode showed two anodic peak currents Ip1 and Ip2 which increased linearly with scan rate v to the power of 0.66 and 0.70, respectively, (i.e. Ip1∝v0.66 and Ip2∝v0.70) at the scan rates higher than 0.5 mV s−1. Moreover, the higher v was, the larger appeared the positive deviations of the first and second peak potentials Ep1 and Ep2 from the first and the second transition potentials E°p1 and E°p2, respectively, in the inverse derivative of the electrode potential curve. The current transients and the linear sweep voltammograms were analyzed in consideration of the interactions between lithium ions in the electrode by using the Monte Carlo simulation under two different constraints of the diffusion-controlled lithium transport and the cell-impedance-controlled lithium transport. The current transients and the linear sweep voltammograms, theoretically calculated under the cell-impedance-controlled constraint in consideration of the interactions between lithium ions, were in good agreement with the experimental results in shape. The disorder to order phase transition in the LiMn2O4 film electrode during the cell-impedance-controlled lithium transport at the potential jump and scan was discussed with the aid of the concentration profiles and the local cross-sectional snapshots of the configuration of lithium ions simulated by the Monte Carlo method. 相似文献
49.
50.