Photoelectrochemical and physical properties of tungsten trioxide films obtained by aerosol pyrolysis

Aerosol pyrolysis (AP) was used for preparing semiconducting films of tungsten trioxide using peroxotungstic acid as a precursor. The films were characterized by SEM, XRD, and by their photoelectrochemical response. Porous, polycrystalline (monoclinic) films of thickness up to 3 μm were prepared. An incident photon to current efficiency (IPCE) of 0.55 at 365 nm was obtained for films of 1 μm thickness on conducting F:SnO₂/glass substrates under depletion conditions, in junctions with aqueous electrolytes. The spectral (photocurrent) response extended into the visible region (up to 470 nm) which is of importance for solar applications like photocatalysis.     

Electrochemical cyclability mechanism for MnO2 electrodes utilized as electrochemical supercapacitors

The electrochemical cyclability mechanism of nanocrystalline MnO₂ electrodes with rock salt-type and hexagonal ?-type structures was investigated to determine the relationship between physicochemical feature evolution and the corresponding electrochemical behaviour of MnO₂ electrodes. Rock salt MnO₂ and hexagonal ?-MnO₂ electrodes, with fibrous and porous morphologies, evolve into the antifluorite-type MnO₂ with a petal-shaped nanosheet structure after electrochemical cycling, similar to that observed in nanocrystalline antifluorite-type MnO₂ electrodes after electrochemical cycling. However, a different impedance response was observed for the rock salt MnO₂ and hexagonal ?-MnO₂ electrodes during the charge–discharge cycles, compared with the improved impedance response observed for the cycled antifluorite-type MnO₂. A dissolution–redeposition mechanism is proposed to account for the impedance response of the MnO₂ electrodes with different morphologies and crystal structures.     

Assessment of the thermal stability of anodic alumina membranes at high temperatures

The thermal stability of anodic alumina membranes (AAMs) annealed in air from 750 °C up to 1100 °C was investigated. AAMs were produced by single-step anodising of laminated AA1050 in 0.30 M oxalic acid medium. The barrier layer provided thermal stability to the membranes, since it avoided or minimized bending and cracking phenomena. X-ray diffraction (XRD) analyses revealed that as-synthesized AAMs were amorphous and converted to polycrystalline after heat-treating above 750 °C. However, porous and barrier layers did not re-crystallize in the same way. The porous layer mainly crystallized in the γ-Al₂O₃ phase within the range of 900–1100 °C, while the barrier layer was converted to the α-Al₂O₃ phase at 1100 °C. Different grain sizes were also estimated from Scherrer's formula. Scanning electron microscopy (SEM) images pointed out that cell wall dilation of the porous layer explained membrane cracking, which was avoided in presence of the barrier layer.     

Corrosion behavior of Cr electrodeposited from Cr(VI) and Cr(III)-baths using direct (DCD) and pulse electrodeposition (PED) techniques

A comparison was made between the electrochemical corrosion behaviors of chromium deposited from hexavalent [Cr(VI)] and trivalent [Cr(III)] chromium baths using direct current (DCD) and pulse electro deposited (PED) techniques. Chromium coatings were deposited on mild-steel (MS) substrate. The corrosion behavior of both DCD and PED chromium from Cr(VI) and Cr(III)-baths in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results indicated that PED chromium from Cr(VI) and Cr(III)-baths have higher charge-transfer resistance R_ct and very low I_corr than that of DCD chromium on mild-steel substrate.     

Localized Electrochemical Deposition of Copper Monitored Using Real‐Time X‐ray Microradiography

We have developed a novel strategy for localized electrochemical deposition (LECD) to improve both the lateral resolution of the process and the porosity of the fabricated high‐aspect‐ratio microstructures. The strategy is based on accurately controlling the motion of the anode. Its implementation is made possible by the use of coherent, synchrotron X‐ray microradiography with high time and lateral resolution, enabling the observation of the copper LECD process in real time. Microradiography reveals a deposition mechanism that differs as a function of the distance between the electrode (anode) and the growing structure (cathode). Specifically, the interplay of migration and diffusion of the metal ions in the baths affects the deposition rate and the characteristics of the fabricated structure. This enables us to optimize the anode motion control and greatly improve the quality of the structure grown.     

Characteristics of Polyaniline/Si Heterojunction Solar Cell By Electrochemical Dye Sensitization

Using the electrochemical polymerization dye sensitization （ECDS） method, polyaniline （PAn）, which is used as top region material in solar cells, is sensitized with direct blue dye（DS）, and sensitized Al grid/DS-PAn/n-Si/Al heterojunction solar cells is prepared by ECDS. Influences of the ECDS on the absorption spectrum and the junction characteristics of the solar cell were discussed, and the output characteristics were measured. The results show that the absorption spectrum of the sensitized PAn films is much wider and stronger in Vis-range; the diode quality factor is about 6.3 and the height of latent barrier potential of p-n junction is 0.89 eV; the short-circuit current and the conversion efficiency of sensitized DS- PAn/Si heterojunction solar cells are greatly improved, which the short-circuit current can increase 6 times, the fill factor is 57% and the efficiency can reach 1.42 % under the illumination of 37.2 W/m^2 , respectively.     

Preparatory processes in the task-switching paradigm: Evidence from the use of probability cues.

The purpose of the investigations was to dissociate processes of task preparation from task execution in the task-switching paradigm. The basic assumption was that task repetitions have 2 advantages over task shifts: an activation advantage as a result of the execution of the same task type in the pretrial, and an expectation advantage, because participants, in general, implicitly expect a repetition. In Experiments 1-3, the authors explicitly manipulated expectancies by presenting cues that announced a shift and/or a repetition with probabilities of 1.00, .75, .50, or .25. Increasing latencies with decreasing probability for shifts and repetitions show that the expectation advantage can be equalized by preparation. However, the activation advantage represented by constant shift costs between tasks of the same probability is not penetrable by preparation. In Experiments 4 and 5, the authors found evidence that preparation involves activation of the expected task and inhibition of distracting tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

污泥含炭吸附剂的制备工艺优化及性能表征

采用先活化剂浸泡活化在干燥热解炭化的化学活化法制备污泥含炭吸附剂.实验结果表明,有机污泥在活化温度为450℃、ZnCl2药剂和干泥质量比为0.7:1、活化时间为1.5 h、锯末添加剂投加量为2%的条件下,制得的含炭吸附剂碘值在510 mg/g以上,收率>60%,比表面积>390 m2/g.由扫描电镜观察可见孔径分布以微孔和中孔为主.     

Electrochemical behavior of Cu in the (NaCl-KCl-CuCl) molten salt

The electrochemical reaction mechanism and electrocrystallization process of Cu on copper electrode in the eutectic NaCl-KCl-CuCl molten salt were investigated by means of cyclic voltammetry, chronopotentiometry and chronoamperometry technique at 710 C. The results show that the electrochemical reaction process of Cu is a quasi-reversible process mix-controlled by Cu + diffusion rate and electron transport rate; the electrochemical reduction mechanism is Cu + +e→Cu; the electrocry stallization process of co...     

Cycle stability of birnessite manganese dioxide for electrochemical capacitors

A combination of step potential electrochemical spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS) has been used to examine the electrochemical cycling behaviour of a well-characterized birnessite-phase manganese dioxide sample for use in electrochemical capacitors. The resistance and interfacial properties of the macroscopic electrode were found to be irreversible with cycling. However, the corresponding properties for the individual particles were more reversible, although they did show substantial hysteresis in their behaviour during cycling. This behaviour was discussed in terms of the structural, conductivity and morphological characteristics of the birnessite at different depths of discharge.