Materials Literature
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Defect structures in a homoepitaxial diamond film grown by chemical vapor deposition have been studied by cross-sectional transmission electron microscopy. Many interstitial dislocation loops are discerned in the (001) interface. The internal region grown on the (11̄1) facet comprises stacking faults and twins, while…
We present the results of large-area (20 cm2) diamond deposition from a scaled-up stagnation-flow reactor. The reactor uses a unique nozzle geometry that optimizes reagent gas usage. The premixed acetylene–oxygen–hydrogen flames were operated in a highly strained configuration, allowing uniform deposition of diamond w…
Impulsive stimulated light scattering experiments were carried out on an ionic glass former Ca0.4K0.6(NO3)1.4 to determine the temperature dependence of the Debye–Waller factor fq(T) in the q→0 limit and to investigate the structural relaxation dynamics. A square-root cusp anomaly was observed in fq→0(T) at a crossove…
We report the realization of a bright and stable electroluminescent Schottky diode based on aluminum-porous silicon junction. White light, visible in normal daylight, is emitted when a reverse bias is applied to the device, promoting the junction breakdown. The device has a fast (100 ns) rise time of the light emissio…
Several reports of electron paramagnetic resonance experiments performed on the spin - Peierls compound have appeared so far, but none of them have precisely explained the origin of the line broadening and the temperature dependence of both the linewidth and the resonance field, all of which differ from those of conve…
We present an extensive study of the approximant phases present in the Al - Cu - Fe phase diagram in the vicinity of the icosahedral phase. In addition to the rhombohedral and the two pentagonal phases previously observed, a new orthorhombic approximant has been identified. The identification of these structures, via…
A complete process compatible with conventional Si technology has been developed in order to produce a bipolar light-emitting device. This device consists of a layer of light-emitting porous silicon annealed at high temperature (800–900 °C) sandwiched between a p-type Si wafer and a highly doped (n+) polycrystalline S…
We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to study the cation distribution in a series of spin-sprayed NiZn-ferrite films. A least-squares fitting of experimental EXAFS data with theoretical, multiple-scattering, EXAFS data allowed the quantitative determination of site distribution…
The C 1s and O 1s core-level photoabsorption spectra of poly[2-methoxy,5-(2′-ethyl- hexoxy)-1,4-phenylene vinylene] (MEH-PPV) before and after exposure O2 and broadband visible light were recorded to determine the degradation pathway for this polymer. The change in the O 1s spectra as a function of exposure demonstrat…
In a series of papers, we have reported the results of dielectric, magnetic and magnetoelectric studies of (R = rare earth between Nd and Lu, Y or Bi), proposing the possibility of ferroelectricity in these oxides, but the direct demonstration of ferroelectricity was lacking. In this paper we present the results of py…
The preoxidation cleaning of silicon carbide surfaces (3C, 4H, 6H polytypes) by exposing them to ultraviolet radiation and oxygen is shown to produce a significant improvement in the electronic properties of SiC/SiO2 interfaces. It is found that this treatment results in a removal of defect species, otherwise present…
We perform long molecular dynamics simulations of liquid water in normal and supercooled states for times up to 50 ns. We observe the onset of a cage effect at 0.25 ps followed by diffusion at much longer time. The diffusion constant has a power-law temperature dependence. The long-time single-particle dynamics of sup…
Magnetoresistance resulting in a drop in resistivity of more than three orders of magnitude that is strongly coupled to lattice striction has been observed under a relatively low magnetic field (0.4 tesla at 115 kelvin) for a single crystal of perovskite-type manganese oxide with finely controlled ionic radii of the A…
Spiders produce a variety of silks that range from Lycra-like elastic fibers to Kevlar-like superfibers. A gene family from the spider Araneus diadematus was found to encode silk-forming proteins (fibroins) with different proportions of amorphous glycine-rich domains and crystal domains built from poly(alanine) and po…
Negative thermal expansion was found for ZrW 2 O 8 from 0.3 kelvin to its decomposition temperature of about 1050 kelvin. Both neutron and x-ray diffraction data were used to solve and refine the structure of this compound at various temperatures. Cubic symmetry persists for ZrW 2 O 8 over its entire stability range.…
The miscibility in the melt and solid state of blends made of poly(p-phenylene sulphide) (PPS) with a liquid crystalline polymer (LCP) from DuPont was studied by polarized light optical microscopy (PLOM) and dynamic thermal mechanical analysis. Both techniques showed that the PPS and the LCP are immiscible in both sta…
The one-pot method polymerization of polyimide was carried out from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) by the use of p-chloro-phenol as the solvent. The behavior of the polymerization was compared with that of the two-step method. The imidization reaction in the one-pot m…
Oil-containing poly(vinyl alcohol) (PVA) microcapsules in the size range of 5–20 μm were prepared by the simple coacervation of PVA followed by chemical crosslinking of the coacervated PVA membrane with glutaraldehyde. Coacervation of the aqueous polymer solution was achieved by the addition of a phase separation indu…
Two series of samples, one of PET and another of PBT, were received after chain extension at different reaction times with two new chain extenders (diimidodiepoxides). These samples showed different intrinsic viscosity and degree of branching or crosslinking. The effect of this differentiation on thermal properties wa…
The water-soluble solids comprised of the ionic complex between chitosan and acetic acid, chitosonium acetate, are converted into chitin by heating. The thermally-induced conversion of a water-soluble chitosonium acetate in film form into a water-insoluble chitin film was examined by thermal analysis (DMTA, TGA, DSC,…