Materials Literature
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Low frequency impedance spectroscopy was applied on a Langmuir monolayer of alkylthiol passivated 35 \AA{} diameter silver quantum dots, as a function of interparticle separation distance. As interparticle spacing decreases below 30% of particle diameter, a reduction in interparticle charge tunneling time is observed.…
Optical conductivity spectra of La_{0.7-y}Pr_{y}Ca_{0.3}MnO_3 were systematically investigated. For metallic samples, the spectral weight below 0.5 eV, whose magnitude can be represented by the effective carrier number N_{eff}(0.5 eV), increases as temperature becomes lower. Regardless of the Pr doping, all the measur…
X-ray absorption and photoemission spectra have been used to measure the band edges of silicon nanocrystals with average diameters ranging from 1 to 5 nm. We compare the experimentally measured band edges to recent electronic structure calculations and find that the experimentally measured band gap is smaller than tha…
A model for the formation of holographic surface relief gratings in azobenzene functionalized polymers is presented. Forces leading to migration of polymer chains upon exposure to light in the absorption band of the azo chromophore are attributed to dipoles interacting with the gradient of the electric field present i…
Pulsed laser vaporization of a heated, Fe/Ni or Co/Ni catalyzed, carbon target in argon gas has been used to synthesize single-wall carbon nanotubes (SWNTs). Electron microscopy, x-ray diffraction, and Raman spectroscopy were all used to study the effect of the catalyst on the tube yield, and the evolution of the tube…
Electrokinetic surface characterization is sensitive to both charge groups (p K and surface density) and neutral polymer coatings (molecular weight, surface density, grafting chemistry). It allows nondestructive, semiquantitative evaluation of coating stability, as regards alteration of the above parameters in relatio…
Blends of nylon 6 (Ny6) with ethylene-co-vinyl alcohol (EVOH) and EVOH modified with the introduction of carboxyl groups (EVOH–COOH) have been studied by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and dynamic-mechanical thermal analysis. The thermal and th…
Polycaprolactone (PCL) was gamma-irradiated at different phases such as solid state at 30 to 55°C, molten state, and supercooled state, under vacuum or air atmosphere, to elucidate its crosslinking behavior. Irradiation in the molten state (80°C) gave higher gel content compared to room temperature. The resulting gel,…
Hemp, banana, and agave fibers were employed for the preparation of wood–polymer composites using polystyrene in the ratio of 50 : 50 w/w. These fibers were esterified with maleic anhydride (MA) and the effect of MA was studied on the absorption of water at ambient temperature and steam in wood–polymer composites made…
This study investigates the effect of deacetylation degree and molecular weight of chitosan on molybdate sorption on both raw and glutaraldehyde crosslinked samples. It appears that the physicochemical parameters affect the crystallinity of the samples: a high crystallinity reduces the accessibility of both water and…
The article describes the preparation of cast acrylic sheets by copolymerizing methyl methacrylate (MMA) with varying mole fractions of N-o-chlorophenyl maleimide (OC), N-m-chlorophenyl maleimide (MC), and N-p-chlorophenyl maleimide (PC) using benzoyl peroxide as an initiator. The effect of incorporation of varying mo…
In order to elucidate the mechanism of cavitation erosion, the dynamics of a single laser-generated cavitation bubble in water and the resulting surface damage on a flat metal specimen are investigated in detail. The characteristic effects of bubble dynamics, in particular the formation of a high-speed liquid jet and…
A heterogeneous 1D dynamic model of SCR−de-NO x (SCR = selective catalytic reduction) monolith reactors is developed, based on the concept of the “active” catalyst region. Its predictions are practically equivalent to those of a previous 2D model, but its numerical solution is faster by 1 order of magnitude, making it…
We have investigated the ordering dynamics and mechanism of a nearly symmetric polystyrene- block -polyisoprene by quenching the specimen from a temperature above the order−disorder transition temperature, T ODT, to temperatures below T ODT, by using time-resolved small-angle X-ray scattering (SAXS) and transmission e…
We demonstrate the relation between supercooling of n -alkane melts and the appearance or nonappearance of rotator phases. Supercooling occurs for the shorter, even chain lengths. The lack of supercooling in most n -alkane melts is discussed in terms of surface crystallization. We argue that melt crystallization of th…
Future developments in circuit design and magnetic data storage will demand smaller and smaller structures. In his Research Commentary, Fasol reviews recent methods for fabricating metallic and magnetic nanowires. In some cases, the precision of existing technology can be applied to creating tiny wires with useful pro…
We discuss a self-avoiding walk model of the adsorption of a copolymer at a plane surface, where the copolymer contains two types of monomers. We concentrate on the case where one type of monomer ( A ) has a short-range interaction with the surface and the other ( B ) has no interaction with the surface. We show that…
An approach based on He scattering is used to develop an atomic-level structural model for an epitaxially grown disordered sub-monolayer of Ag on Pt(111) at 38K. Quantum scattering calculations are used to fit structural models to the measured angular intensity distribution of He atoms scattered from this system. The…
We study experimentally the molecular weight $M$ dependence of spreading rates of molecularly thin precursor films, growing at the bottom of droplets of polymer liquids. In accord with previous observations, we find that the radial extension R(t) of the film grows with time as R(t) = (D_{exp} t)^{1/2}. Our data substa…
We have used scanning probe microscopy to investigate self-assembled monolayers of chemically synthesized peptides. We find that the peptides form a dense uniform monolayer, above which is found a sparse additional layer. Using scanning tunneling microscopy, submolecular resolution can be obtained, revealing the alpha…