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Same Thickness (same + thickness)
Selected AbstractsMesoporous Hydrous Manganese Dioxide Nanowall Arrays with Large Lithium Ion Energy Storage CapacitiesADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Dawei Liu Abstract Novel nanowall arrays of hydrous manganese dioxide MnO2,·,0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1,M solution possess a surface area of ,96,m2 g,1 and exhibit a stable high intercalation capacity of 256,mA hg,1 with a film of 0.5,µm in thickness, far exceeding the theoretical limit of 150,mA hg,1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ,230,mA hg,1 for films of ,2.5,µm) than that of anodic deposited films of the same thickness (,80,mA hg,1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro- and mesoporosity of the MnO2,·,0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid-state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de-intercalation. [source] Electroactivity of Polyaniline Multilayer Films in Neutral Solution and Their Electrocatalyzed Oxidation of ,-Nicotinamide Adenine DinucleotideADVANCED FUNCTIONAL MATERIALS, Issue 6 2003S. Tian Abstract In this paper, we report an alternative simple method to shift the electroactivity of polyaniline (PANI) films to neutral pH conditions by forming multilayer assemblies with poly(anions) using the layer-by-layer (LBL) deposition method. A series of self-assembled PANI multilayer films with poly(anions), such as sulfonated polyaniline (SPANI), poly(acrylic acid) (PAA), poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS), were prepared by the LBL method. Their electrochemical behavior and catalytic ability for the oxidation of ,-nicotinamide adenine dinucleotide (NADH) in neutral solution were investigated by electrochemistry (EC) combined with surface plasmon spectroscopy (SPS) and the quartz crystal microbalance (QCM) technique. Results indicated that all the films showed very good stability, reversibility, and electroactivity in neutral solution. All the multilayer films can electrocatalyze the oxidation of NADH, with the catalytic ability of PANI/SPANI being higher than that of the other assemblies under the same conditions. The catalytic abilities of the films with the same thickness prepared by the copolymerization method and the LBL method were also compared. [source] INFLUENCE OF SAMPLE SIZE AND SHAPE ON TRANSPORT PARAMETERS DURING DRYING OF SHRINKING BODIESJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2007NAJMUR RAHMAN ABSTRACT An experimental investigation on the influence of sample size and shape on heat and mass transport parameters under natural convection air-drying is presented. Potato cylinders with length of 0.05 m and thicknesses of 0.005, 0.008, 0.010 and 0.016 m, and circular slices with diameter of 0.05 m and thickness of 0.01 m were dried in a laboratory scale hot-air cabinet dryer. Results indicate that each transport parameter exhibits a linear relationship with sample thickness. Convective heat and mass transfer coefficients (hcand hm) decreased whereas moisture diffusion coefficient (Deff) increased with increasing thickness. Considering no sample shrinkage effect in the parameter analysis, for the thickness range considered, the values of hcare found to be underestimated in the range of 29.0,30.6%, whereas those of hmand Deff are overestimated in the range of 33.7,38.0% and 75.9,128.1%, respectively. Using Levenberg,Marquardt algorithm for optimization, a correlation for Biot number for mass transfer (Bim) as a function of drying time and sample thickness is proposed. A close agreement was observed between dimensionless moisture contents predicted by this relation and those obtained from experiments for different sample thicknesses at drying air temperature of 60C. For the same thickness and drying conditions, circular slices caused an increase in each transport parameter significantly. [source] Tunneling current in gate dielectric stack in sub-45 nanometer CMOS devicesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Hitender Kumar Tyagi Abstract Direct tunneling current through dual layer SiO2/high-K dielectric structures are investigated for substrate injection. Correlation of dielectric constants and band offsets with respect to silicon has been taken into consideration in order to identify possible materials to construct these devices. The direct tunneling current in oxide/high-K dielectric structures with equivalent oxide thickness (EOT) of 2.0 nm can be significantly lower than that through single layer oxides of the same thickness. Various structures and materials of high-K stacks of interest have been examined and compared to access the reduction of gate current in these structures. It is estimated that HfO2/SiO2 dual stack structure can reduce gate leakage current by four orders of magnitude as compared with pure SiO2 layer of same EOT. The importance of interfacial layer in dual stack structure is high-lighted for the reduction of gate leakage current. The present approach is capable of modeling high-K stack structures consisting of multiple layers of different dielectrics (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface Modification by Compositionally Modulated Multilayered Zn-Fe Alloy CoatingsCHINESE JOURNAL OF CHEMISTRY, Issue 12 2008V. THANGARAJ Abstract Compositionally modulated multilayered alloy (CMMA) coatings of Zn-Fe were developed from acid chloride baths by single bath technique. The production and properties of CMMA Zn-Fe coatings were tailored as a function of switching cathode current densities (SCCD's) and thickness of individual layers. Corrosion rates (CR) were measured by electrochemical methods. Corrosion resistances were found to vary with SCCD's and the number of sub layers in the deposit. SCCD's were optimized for production of Zn-Fe CMMA electroplates showing peak performance against corrosion. The formation of discrete Zn-Fe alloy layers having different compositions in the deposits were demonstrated by scanning electron microscopy (SEM). Improvements in the corrosion resistance of multilayered alloys are due to the inherent barrier properties of CMMA coatings as evidenced by electrochemical impedance spectroscopy (EIS). Corrosion resistance afforded by Zn-Fe CMMA coatings are explained in terms of the n-type semiconductor films at the interface, supported by Mott-Schottky's plot. It was observed that the alloy with high w(Fe) on the top showed better corrosion resistance compared to that with the less w(Fe) on top. At optimum SCCD's of 3.0,5.5 A·dm,2, a Zn-Fe CMMA coatings with 600 sub layers showed ca. 45 times better corrosion resistance than conventional Zn-Fe alloy of the same thickness. The deposit showed no red rust even up to 1130 h in salt spray test. [source] | ||||||||||