The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD) is discussed and experimentally illustrated. Cyclic Voltam...
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ISBN:
(纸本)9781566774925
The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD) is discussed and experimentally illustrated. Cyclic Voltammetry and Scanning Tunneling Microscopy are employed to carry out and monitor a "quasi-perfect", two-dimensional growth of up to 35 monolayers (MLs) of Ag on Au(111) by repetitive galvanic displacement of underpotentially deposited Tl and Pb monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology, The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process. An X-ray Photoelectron Spectroscopy analysis finds no traces of Pb in the Ag deposit. copyright The Electrochemical Society.
The Toying With TechnologySMprogram (TWT) has been offered to preservice elementary and secondary teachers for ten years. This program is designed to explain the principles behind many of the technological innovations...
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The tribological properties of sputter-deposited MoS2 and MoS2-Ti films were investigated in this study. The deposited films were characterized using microprobe analysis for composition and x-ray diffraction (XRD) for...
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The tribological properties of sputter-deposited MoS2 and MoS2-Ti films were investigated in this study. The deposited films were characterized using microprobe analysis for composition and x-ray diffraction (XRD) for structure. The frictional properties of the films were examined using a pin-on-disk (POD) with counterfaces of 440C steel, aluminum, tungsten carbide and alumina. The tests were run under low (25%), medium (50%) and high (70%) humidity levels. MoS2 films without Ti were first examined under cyclic humidity conditions between 25 and 50% R/H. The results showed that for steel, WC and alumina counterfaces, the effect of the higher humidity was to increase the friction, but lower friction could be recovered when the humidity was reduced back to 25%. For films containing Ti, the best results were obtained at a concentration of 20 at. % Ti. These films performed well for steel and WC counterfaces, but poorly against aluminum. The effect of deposition temperature (up to 450oC) was examined for MoS2 and MoS2-5% Ti films. Higher temperatures yielded more crystalline films, but the addition of Ti partially countered this effect. The POD test showed that at medium humidity levels the friction decreased with temperature, but increased slightly when tested under low humidity. In all cases, the 5% Ti-containing films had a fiction coefficient of about 0.1 below that for films without Ti.
Controlled defects were created on DNA linked 2-D colloidal photonic crystals using a Nd:YAG pulsed laser. The 2-D photonic crystals were self-assembled using 1.8 μm polystyrene (PS) microspheres on functionalized gl...
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Controlled defects were created on DNA linked 2-D colloidal photonic crystals using a Nd:YAG pulsed laser. The 2-D photonic crystals were self-assembled using 1.8 μm polystyrene (PS) microspheres on functionalized glass substrates. To synthesize the hexagonal close packed crystalline samples, both substrate and particles attached single-strand DNA, sequence A on the substrate and sequence B on the particles. The DNA was hybridized using the DNA linker with complementary single-strand A’B’ that anchored the particles to the substrate during self-assembly. The 532 nm second harmonic wavelength beam of the pulsed Nd:YAG laser (1064 nm) with a pulse width of 10 ns was used for the removal of individual colloidal particles from the self assembled photonic crystals. In the present tests, the diameter of the laser beam was optically reduced from 7 mm to about 1.8 μm. Controlled line defects and geometrical shapes (e.g., hexagonal and triangle) were created in the 2D arrays in an aqueous medium.
Commercial polyurethane foams with a monomodal pore size distribution were used to produce LZSA glass ceramic foams by the polymeric sponge method. A suspension containing LZSA glass ceramic, bentonite and sodium sili...
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ISBN:
(纸本)0470080507
Commercial polyurethane foams with a monomodal pore size distribution were used to produce LZSA glass ceramic foams by the polymeric sponge method. A suspension containing LZSA glass ceramic, bentonite and sodium silicate, was prepared in water and isopropanol media to impregnate the polymeric foams by dip coating. The suspension was characterized by Theological measurements. The effect of the solvent on the microstructure and physical properties on the LZSA foams was also evaluated. The cellular microstructure of the glass-ceramic foams was characterized by scanning electron microscopy (SEM) and micro-computer X-ray tomography (μ-CT). The LZSA foam prepared with isopropanol suspension exhibited higher mechanical strength under compression than those prepared with water.
The objective of the proposed paper is to present a processing technique, test methods, experimental results, and manufacturing concerns related to mechanical performance of composite laminates with selective reinforc...
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Three possible functions of Ti-peroxy gel are: reduction of the inflammatory response through the reduction of hydrogen peroxide and other reactive oxygen species;creation of a favorable surface for calcium phosphate ...
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With a careful handling of the chemically desodiated Na0.75−xCoO2 [0.32⩽(0.75−x)⩽0.75] samples, the oxidation state of Co is found to be in agreement with the theoretically expected values. The apparent lowering of th...
With a careful handling of the chemically desodiated Na0.75−xCoO2 [0.32⩽(0.75−x)⩽0.75] samples, the oxidation state of Co is found to be in agreement with the theoretically expected values. The apparent lowering of the oxidation state reported in the literature at low sodium contents is due to a rapid absorption of water from ambient air and the lack of appropriate corrections in the molecular weight used in the oxidation state calculation. However, a significant decrease in the oxidation state of cobalt is found for the bilayer hydrate sample obtained by immersing the anhydrous Na0.75−xCoO2 in water due to a reduction of the highly oxidized Co4+ ions by water and a possible insertion of oxonium (H3O+) ions into the lattice as evident from the redox titration and thermogravimetric analysis data. On the other hand, the analogous layered Li0.3CoO2 does not absorb any water on exposure to air. More importantly, the Li1−xCoO2 system incorporates protons into the lattice during chemical delithiation while the Na0.75−xCoO2 system does not down to a sodium content of 0.32. The differences between the two systems are discussed based on the differences in the structures and the position of the Co3+∕4+:3d band relative to the top of the O2−:2p band.
Heteronuclear Bi1-x La x [Fe(CN)6] ·nH2O complexes were synthesized, and their crystal structures and thermal decomposition process were investigated by X-ray diffraction (XRD), thermogravimetry analysis (TG...
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Heteronuclear Bi1-x La x [Fe(CN)6] ·nH2O complexes were synthesized, and their crystal structures and thermal decomposition process were investigated by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Auger electron spectroscopy (AES) with scanning electron microscope (SEM), and transmission electron microscopy (TEM). The crystal system of the complexes was orthorhombic having n = 4 for x = 0-0.7 and was hexagonal having n = 5 for x = 1.0. Their mixture was confirmed for x = 0.8 and 0.9. The lattice parameters for the orthorhombic increased with increasing the x value for the complexes. The single phase of trimetallic perovskite-type Bi1-x La x FeO3 was obtained by its thermal decomposition at low temperature. The crystal system was hexagonal for BiFeO3 (x = 0) and orthorhombic for x = 0.1-1.0. In the case of the decomposed perovskite sample, the lattice parameters decreased with increasing x values for Bi1-x La x FeO3. The particle size was ca. 30 nm for Bi0.2La0.8FeO3 obtained by thermal decomposition at 500 °C and it grew with an increase in decomposition temperature. For the Bi0.5La0.5FeO 3, AES showed that the elemental distributions of Bi, La, and Fe on the surface were very homogeneous for the sample decomposed at 700 °C.
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