Materials Literature
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Schottky diodes were fabricated using gold and aluminum contacts to thin diamond films obtained by a microwave plasma assisted chemical vapor deposition process. The current-voltage and capacitance-voltage-frequency characteristics of these devices are similar to those fabricated on a crystalline diamond base formed b…
Symmetrically strained Si/Ge superlattices with an overall thickness of 0.2 \ensuremath{\mu}m, well above the critical thickness (\ensuremath{\cong} 10 nm) of unsymmetrically strained superlattices of the same composition, are studied. Strain adjustment is obtained by growing thin homogeneous ${\mathrm{Si}}_{0.4}$${\m…
Measurements performed on the in-plane thermoelectric power of first-stage graphite-acceptor intercalation compounds in the temperature range $3<T<300$ K are reported. At high temperature, the thermoelectric power is close to that obtained for higher-stage compounds while in the lower-temperature range it drops…
Small-angle x-ray scattering from the segmental density fluctuations of a starblock copolymer with a given arm number n of 6 as well as that of a linear diblock copolymer (corresponding to the starblock copolymer with n=1) were studied in both ordered and disordered states. In the ordered state the characteristic wave…
Raman spectra of LiClO4 complexed in poly(propylene-glycol) (PPG) have been obtained for concentrations of the monomer to salt ratio (ether oxygen):Li in the range 30:1–5:1. Splitting of the symmetric stretching mode of the ClO4− anion was observed with an intensity profile that varied with salt concentration. This ph…
Some characteristics of reversible phase-change optical data storage based on an amorphous-crystalline transformation in InSbTe alloys are given. The reversible phase change was observed in a wide region of composition. The laser amorphized spot of a ternary compound In3SbTe2 film could be crystallized using a diode l…
Band-structure calculations are presented for different lattice conformations of doped polyacetylene and polythiophene. At intermediate doping levels, the intraband transition energies are found to be in good agreement with experimental optical-absorption data for a soliton lattice conformation in polyacetylene and a…
A b initio calculations have been performed to study the structures and energies of intermediate-sized silicon clusters (Sin, n=7–10). All geometries have been optimized at the Hartree–Fock (HF) level of theory with the polarized 6-31G* basis set. The harmonic vibrational frequencies have been evaluated at the HF/6-31…
An investigation is made of the surface morphology and growth of polycrystalline diamond films deposited on Si substrates using the microwave plasma chemical-vapor-deposition (CVD) method. For the source gas, ${\mathrm{CH}}_{4}$ and ${\mathrm{H}}_{2}$ gases mixed in different concentrations are used. Scanning electron…
A novel x-ray diffraction technique, multiple-wavelength anomalous dispersion (MAD) phasing, has been applied to the de novo determination of an unknown protein structure, that of the "blue" copper protein isolated from cucumber seedlings. This method makes use of crystallographic phases determined from measurements m…
Anharmonicity in the lattice vibrations of oxygens in UO 2 has been examined by using EXAFS of the UL III absorption edge. Whilst the EXAFS-determined U-U distance of 3.89 AA closely matches the crystallographic separation, the U-O distance of 2.43 AA is 0.06 AA longer. This shift is interpreted on the basis of an anh…
Self-consistent spin-polarised electronic band structure calculations have been performed for La 2 NiO 4 in its nonmagnetic, ferromagnetic and antiferromagnetic states. The principal results are: the band structure of nonmagnetic tetragonal La 2 NiO 4 is similar to the isostructural La 2 CuO 4 , but with two Ni-O (3d(…
In an investigation of self-diffusion in bcc $\ensuremath{\beta}$-Ti single crystals by means of both quasielastic and inelastic neutron scattering, the elementary diffusion jump has been determined directly, and the lattice vibrations which trigger the jump have been elucidated. The elementary jump for self-diffusion…
We report preliminary dynamical structure-factor $G(q,t)$ measurements performed on polydisperse polymer cluster solutions at concentrations such that the largest clusters are partly penetrated by smaller clusters. Upon increase of the polymer concentration, the $G(q,t)$ profile goes from a stretched-exponential funct…
The authors introduce a new microscopic model for microemulsions. The model applies to continuum fluids as well as to lattice systems. In a mean-field treatment they show that, below a critical temperature, a microemulsion is formed. Different geometrical structures of the microemulsion (lamellar, tubular and cubical)…
Abstract A series of polyether block amide copolymers based on poly(tetramethylene oxide) of molecular weight 1000 or 2000 and polyamide 12 of molecular weight between 600 and 4000 with varying PE/PA weight ratio (from 80 to 20%) were studied by using dynamic mechanical spectroscopy and differential scanning calorimet…
Abstract A modified diffuse reflectance technique is used to characterize the surface hydrolysis of Kevlar‐49 fibers. Treatment with 10 wt% NaOH solution produces carboxylate groups on the surface which increase rapidly up to treatment times of about 20 min at room temperature or 50 min in boiling solution. After this…
Abstract The mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol‐A carbonate) (PC) has been investigated. These compounds are capable of inducing a self‐extinguence in PC even when present in very low amounts (0.2–1%). Thermogravimetric and flash pyrolysis–GC–MS data show the th…
Abstract The integral of loss modulus versus temperature plots in the vicinity of the glass transition temperature (loss area, LA) was characterized for various homopolymers, statistical copolymers, and interpenetrating polymer networks (IPNs), based on acrylics, vinyls, and styrenic mers. The quantity LA was found to…
Abstract Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were used to characterize the morphology of solvent cast hydroxypropyl cellulose (HPC) films. DSC results were indicative of a semicrystalline material with a melt at 220°C and a glass transition at 19°C ( T 1 ), although a…