Electrodeposited nanostructured α-Fe2O3 thin films for solar water splitting: Influence of Pt doping on photoelectrochemical performance

Electrochemically deposited α-Fe₂O₃ thin films, whose composition was tuned by Pt doping, were investigated as photoanode for photoelectrochemical water splitting. Morphological and structural characteristics of the nanostructured α-Fe₂O₃ thin films were studied by scanning electron microscopy and X-ray diffraction techniques. The films were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy to determine the effect of Pt doping on the α-Fe₂O₃ structure. The photoelectrochemical performance of the films was examined by linear sweep voltammetry and electrochemical impedance spectroscopy. Results of these studies showed that Pt doping increased the density of small-sized nanoparticles in α-Fe₂O₃ thin films. The Pt doped films exhibited higher photoelectrochemical activity by a factor of 1.4 over un-doped α-Fe₂O₃ films. The highest photocurrent density of 0.56 mA cm⁻² was registered for 3% pt doped film at 0.4 V versus Ag/AgCl in 1 M NaOH electrolyte and under standard illumination conditions (AM 1.5 G, 100 mW cm⁻²). This high photoactivity can be attributed to the high active surface area and increased donor density caused by Pt doping in the film. Electrochemical impedance analysis also revealed significantly low charge transfer resistance of Pt doped films, indicating its superior electrocatalytic activity for water splitting reaction compared to un-doped α-Fe₂O₃ thin films.     

Batch process schedule optimization under parameter volatility

A general strategy to treat the uncertainties in parameters of batch process scheduling has been developed. The strategy consists of three algorithms: flexible planning, flexible scheduling and reactive schedule adaptation. In this paper, we introduce the flexible scheduling and the reactive schedule adaptation algorithms. The flexible scheduling algorithm is based on both a Monte Carlo simulation and a simulated annealing. It can deal with multiple uncertain parameters and any type of probability density function for the uncertain parameter. We seek the flexible schedule that maximizes the expected profit, including net present values of products less raw material and processing costs, as well as due date penalties, inventory costs and setup costs. In reality, the values of uncertain parameters always change after the batch process schedule and plan are set up. Since the flexible schedule has periods of free time that can be used to accommodate uncertainties during the actual production, the reactive schedule adaptation algorithm can modify the flexible schedule in response to any change in an uncertain parameter with little or no penalty. This algorithm finds a new optimal or suboptimal solution under the new condition by using a combination of different local search methods, which are described.     

Poly(o-anisidine) on brass: Synthesis and corrosion behavior

The electrochemical synthesis of poly(o-anisidine) (POA) was achieved on brass (CuZn) electrode by applying two scan rates (50 and 20 mVs⁻¹). The synthesized polymer films were strongly adherent and homogeneous in both cases. Their corrosion performance was investigated by AC impedance spectroscopy (EIS) technique, anodic polarization plots and open circuit potential-time curves, in 3.5% NaCl solution. It was clearly seen that poly(o-anisidine) films provided a significant physical protection for longer exposure time. It was shown that polymer film coated at high scan rate (CuZn/POA-H) exhibited better barrier property against the attack of corrosive agents when compared with polymer film obtained at low scan rate (CuZn/POA-L). It was found out that poly(o-anisidine) film synthesized at high scan rate caused a significant increase in corrosion resistance by its catalytic behavior on formation of protective oxide layers on the surface in longer time.     

Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors: Deep-Level Transient Spectroscopy (DLTS) Measurements

We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48?eV. The absence of a V_Cd trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[Pb_Cd]⁺-V _Cd ^2? ]^?. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36?meV and a deep donor trap at around 0.82?eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18?eV (A-centers) and 0.31?eV (V_Cd), and a deep trap at around 1.1?eV.     

Continuous Control of Charge Transport in Bi‐Deficient BiFeO3 Films Through Local Ferroelectric Switching

It is demonstrated that electric transport in Bi‐deficient Bi_1‐δFeO₃ ferroelectric thin films, which act as a p‐type semiconductor, can be continuously and reversibly controlled by manipulating ferroelectric domains. Ferroelectric domain configuration is modified by applying a weak voltage stress to Pt/Bi_1‐δFeO₃/SrRuO₃ thin‐film capacitors. This results in diode behavior in macroscopic charge‐transport properties as well as shrinkage of polarization‐voltage hysteresis loops. The forward current density depends on the voltage stress time controlling the domain configuration in the Bi_1‐δFeO₃ film. Piezoresponse force microscopy shows that the density of head‐to‐head/tail‐to‐tail unpenetrating local domains created by the voltage stress is directly related to the continuous modification of the charge transport and the diode effect. The control of charge transport is discussed in conjunction with polarization‐dependent interfacial barriers and charge trapping at the non‐neutral domain walls of unpenetrating tail‐to‐tail domains. Because domain walls in Bi_1‐δFeO₃ act as local conducting paths for charge transport, the domain‐wall‐mediated charge transport can be extended to ferroelectric resistive nonvolatile memories and nanochannel field‐effect transistors with high performances conceptually.     

Effects of Er:YAG laser on bond strength of self‐etching adhesives to caries‐affected dentin

The erbium:yttrium–aluminum–garnet (Er:YAG) laser may be effective the bond strength of adhesive systems on dentine surfaces, the chemical composition and aggressiveness of adhesive systems in clinical practice. The purpose of this study was to evaluate the effects of the Er:YAG laser system with the bonding ability of two different self‐etching adhesives to caries‐affected dentine in primary molars. Ninety mid‐coronal flat dentine surfaces obtained from sound and caries‐affected human primary dentine were treated with an Er:YAG laser or a bur. The prepared surfaces were restored with an adhesive system (Xeno V; Clearfil S³) and a compomer (Dyract Extra). The restored teeth were sectioned with a low‐speed saw and 162 samples were obtained. The bond strength of the adhesive systems was tested using the micro‐tensile test method. The data were statistically analyzed. A restored tooth in each group was processed for scanning electron microscopy evaluation. The values of the highest bond strength were obtained from the Clearfil S³‐Er:YAG laser‐sound dentine group in all groups. (24.57 ± 7.27 MPa) (P > 0.05). The values of the lowest bond strength were obtained from the Xeno V‐Er:YAG laser‐sound dentine group in all groups (11.01 ± 3.89 MPa). It was determined that the Clearfil S³ increased the bond strength on the surface applied with Er:YAG laser according to the Xeno V. Microsc. Res. Tech. 77:282–288, 2014. © 2014 Wiley Periodicals, Inc.     

Carbon contamination analysis and its effect on extreme ultra violet mask imaging performance using coherent scattering microscopy/in-situ accelerated contamination system

The coherent scattering microscopy/in-situ accelerated contamination system (CSM/ICS) is a developmental metrology tool designed to analyze the impact of carbon contamination on the imaging performance. It was installed at 11B EUVL beam-line of the Pohang Accelerator Laboratory (PAL). Monochromatized 13.5 nm wavelength beam with Mo/Si multilayer mirrors and zirconium filters was used. The CSM/ICS is composed of the CSM for measuring imaging properties and the ICS for implementing acceleration of carbon contamination. The CSM has been proposed as an actinic inspection technique that records the coherent diffraction pattern from the EUV mask and reconstructs its aerial image using a phase retrieval algorithm. To improve the CSM measurement accuracy, optical and electrical noises of main chamber were minimized. The background noise level measured by CCD camera was approximately 8.5 counts (3 sigma) when the EUV beam was off. Actinic CD measurement repeatability was <1 A (3 sigma) at 17.5 nm line and space pattern. The influence of carbon contamination on the imaging properties can be analyzed by transferring EUV mask to CSM imaging center position after executing carbon contamination without a fine alignment system. We also installed photodiode and ellipsometry for in-situ reflectivity and thickness measurement. This paper describes optical design and system performance observed during the first phase of integration, including CSM imaging performance and carbon contamination analysis results.     

Study of effect of binders and loading pressures on the performance of the time delay pyrotechnic compositions

ABSTRACT

An experimental investigation was carried out to determine the effect of binders and loading pressures on burning performance of B/BaCrO₄ and Si/PbO/Pb₃O₄ delay compositions. The consolidated density and percent theoretical maximum density (%TMD) of these compositions were also studied with different binders and at multiple loading pressures. Carboxyl methyl cellulose (CMC), dextrin, and fish glue with varying wt. % were used as binders. It was observed that the burning rate of these delay compositions was inversely proportional to the binder content. The burning rate of B/BaCrO₄ delay composition was 71.0 mm/s without binder. The burning rate decreased to 38.1 mm/s by adding 3.0 % fish glue. When 1.0 % CMC was added to the mixture, the burning rate decreased to 61.8 mm/s. By adding 3.0 % dextrin to the delay composition, the burning rate decreased to 38.2 mm/s. The burning rate of Si/PbO/Pb₃O₄ delay mixture was 38.6 mm/s without binder. The burning of this mixture decreased to 16.4 mm/s by adding 1.0 % fish glue. The loading pressures were varied from 103 to 414 MPa. The effect of loading pressures on the burning rate of both the delay compositions was marginal. The burning rate of B/BaCrO₄ delay mixture decreased with the increase in loading pressure. On contrary, the change in burning rate of Si/PbO/Pb₃O₄ pyrotechnic delay composition was minimal by varying the loading pressures. Results also revealed that loading pressures of 345 and 348 MPa produced the minimum standard deviation in burning rate of B/BaCrO₄ and Si/PbO/Pb₃O₄ compositions. The consolidated density and %TMD of both mixtures increased by adding binders and increasing the loading pressures.     

Fabrication of Micro-pipes of YBa2Cu3O7−δ Superconductor

Synthesis of micro-pipes of YBa₂Cu₃O_7−δ superconductor has been carried out for the first time by using chemical method. The shape, size and length of these micro-pipes depends upon dimensions of growth matrix and structure of geometry, i.e., circular, square, rectangular and hexagonal, etc., which could be uniformly coated with superconductor. The onset temperature of diamagnetism of the material is found to be 93 K, which is not shifted to lower values by the application of DC magnetic field; this is most likely due to large surface area provided by micro-pipes to the shielding currents. These micro-pipes behave as pinning centers, hence they can be used for the fabrication of devices that are capable of working in high magnetic fields.