Materials Literature
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The glass transition of a two-dimensional melt of lattice polymers is discussed. The glass temperature Tg is determined by the free volume approach, by the isothermal compressibility as well as by other methods. The decay of the bond autocorrelation function displays typical glasslike behavior. The time temperature su…
Abstract The reaction of maleic anhydride (MAH) with molten 2 MI poly(ethylene‐ co ‐butene‐1) (LLDPE) at 160°C in the presence of peroxyesters ( t 1/2 < 10 s) as catalysts resulted in the formation of a mixture of cross‐linked and trichlorobenzene‐soluble LLDPE‐ g ‐MAH. The soluble fraction constituted more than 50…
The coadsorption of oxygen and carbon monoxide on the stepped Pt(112) surface has been studied using electron stimulated desorption–ion angular distribution (ESDIAD), temperature programmed desorption (TPD), and low energy electron diffraction (LEED). It has been possible to preferentially adsorb different isotopic CO…
Spectral shapes of optical absorptions in the charge density wave states of halogen-bridged mixed-valent metal complexes are theoretically determined for the first time, using a one-dimensional extended Peierls-Hubbard model. Two important effects beyond the mean field theory are taken into account; the electron-hole…
We present theoretical studies of the electronic and optical properties of free-standing Si quantum wires which exist in porous Si. We use a second-neighbor empirical tight-binding model which includes d orbitals and spin-orbit interaction. The excitonic effects are included within the effective-mass approximation. We…
Recent reports describing photoluminescence in porous silicon have heightened the level of interest in it as a unique electronic material, and have created a need for a more complete understanding of the mechanism of porous silicon formation. The various models describing porous silicon formation are reviewed and the…
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” opt…
Polarized electrons were scattered from zinc, cadmium and indium atoms which were unpolarized. Elastic scattering asymmetries were observed at energies ranging from 0.3 (for Cd) to 14 eV and at angles from 30' to 125'. For indium inelastic scattering asymmetries were also measured. Comparing the asymmetries obtained f…
This paper presents experimental results of space-charge distribution in cross-linked polyethylene (XLPE) by a pulsed electroacoustic method. The influence of polarity reversal on space-charge distribution in degassed XLPE and as-received XLPE is studied to understand the transport and injection of charges under DC vo…
It is shown that the diffusion of Cu into the Ni layer of a Ni/Cu bilayer film after thermal annealing is significantly reduced when the deposition temperature of the Ni layer is raised from approximately 50 to 200 °C. The effect of the deposition temperature on the physical structure of the Ni layer and the possible…
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992.
Diamond films were grown using microwave-plasma enhanced chemical vapor deposition. Boron doping in these films were achieved by using 0–1 ppm diborane (B2H6) in the reaction gas mixture during the deposition process. Some samples were deposited using 0.1% oxygen in the reaction gas mixture. We have employed cathodolu…
We report neutron inelastic scattering measurements of the dispersion of the phase mode of the charge-density-wave (CDW) collective excitations in the blue bronze. Anisotropy and temperature-dependence analysis yields phase elasticity parameters relevant for a classical deformable model of CDW. The considerable stiffe…
Thin films (0.3–5 μm) of an amorphous fluoropolymer (AF) derived from the copolymeric material Teflon AF 1600 were deposited on Si (100) wafers by vacuum pyrolysis. Infrared spectroscopy indicated that the composition of the deposited films was similar to the source material. The deposited films were amorphous by x-ra…
We present calculations of the electronic structure for higher-order rational approximations to quasicrystals up to 12 380 atoms in the unit cell, based on a tight-binding linear-muffin-tin-orbital technique. The dispersion relations of the electronic states of quasicrystals are related to those of quasiperiodic free-…
Room-temperature photoluminescence (PL) from Si chemically etched (CE) in HF-HNO3-based solution has been observed. Scanning electron microscopy reveals that the etched Si has a surface morphology similar to that of luminescent porous Si fabricated by conventional anodization. PL spectra show an order of magnitude sma…
The temperature dependence of the characteristic length for the dynamic glass transition in ortho-terphenyl is determined, for the first time, from combined results of depolarized dynamic light scattering, photon correlation spectroscopy, and viscosity experiments. The length is found to vary according to ${\ensuremat…
Structural studies on aqueous solutions of PEO-PPO-PEO block copolymers show three phases as the temperature is varied. At low T, the tri-block units are dissolved Gaussian chains. As T is increased still more unimers aggregate in micelles, until a volume fraction of 0.52 is reached. The micelles then crystallize in a…
This new study of the hard ellipsoids system by Monte Carlo simulations invalidates previous simulation work on the localization of the isotropic-nematic phase transition (Molec. Phys., 55, 1171 (1985)). The discrepancies are demonstrated to originate in size effects. Our main result is that the system of hard ellipso…
Abstract Melting parameters and transport coefficients in the melt are collated for halides of monovalent, divalent and trivalent metals. A number of systems show a deficit of entropy of melting relative to the linear relations between entropy change and relative volume change on melting that are found to be approxima…