Materials Literature
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We report on investigations of one-dimensional thermal transport in compositionally modulated metal films produced with a systematic variation in atomic lattice mismatch. In the case of Ni-Cu, Ni-Mo, Ni-Ti, and Ni-Zr, we observe the relative effects of interfacial disorder on thermal diffusion. Our observations demons…
Experimental characterization of the bulk absorption properties of sapphire, spinel, yttria, and ALON as a function of temperature is accomplished using a Bomem DA3.02 vacuum Fourier transform spectrometer and a heated cell. The measurements are performed between 2 and 20 microm from room temperatures to 775 K. Spectr…
Infrared multiphoton dissociation (IRMPD) of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a molecular beam has been performed in order to investigate the mechanism of RDX thermal decomposition. A beam of molecules was crossed by a pulsed TEA CO2 laser and velocity distributions of the various products were measure…
Reflectance vs incidence angle measurements have been performed from 24 A to 1216 A on electron-beam evaporated samples of Ti, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au, and using a nonlinear least-squares curve-fitting technique, the optical constants have been determined. Independently measured v…
We analyze theoretically the oscillator strength and the third-order optical polarizability ${\ensuremath{\chi}}^{(3)}$ due to excitons in semiconductor microcrystallites. The nonlinear optical polarizability is shown to be greatly enhanced for an assembly of such microcrystallites as the exciton is quantized due to t…
The thermal properties of the 14 nonmagnetic cubic metals through the 4d transition series are derived from first-principles electronic-structure calculations coupled with a Debye treatment of the vibrating lattice. Debye temperatures and Gr\"uneisen constants are derived from an analysis of the compressional characte…
Using the electron-beam-induced barrier currents and the Monte Carlo simulation methods it was possible to determine the depth-dose function as well as the distribution function of the generation source for electron-hole pairs perpendicular to the injection direction. The depth-dose function was compared with results…
The properties of electrically conducting, semiconducting, and semi-insulating polymers are surveyed and their conduction mechanisms, mechanical properties, and suitability for space-based use and other advanced applications are evaluated.
Thermoluminescence emission spectra of six phosphors commonly used for TL dosimetry are presented at doses between 15 mGy and 1 Gy. The use of a Fourier transform spectrometer has made it possible to obtain spectra at doses considerably lower than those for spectra previously reported. The spectra are in the form of i…
Previous studies of the gas sensitivity of CuPC (copper phthalocyanine) and ZnPC have been extended to include CoPC and NiPC, with particular reference to ammonia detection. Ammonia sensitivity is found to depend on the crystal structure of the films, ammonia concentration and temperature. The alpha - beta phase trans…
The conductivity of four graphite powders was measured as a function of the volume fraction of graphite (or air) along (axial) and across (transverse) the direction of compression. The conductivity varies by between two and four orders of magnitude during these measurements. The results are shown to fit an equation wh…
Over recent years, Rolls-Royce plc has committed significant research resources to the development of diffusion bonding processes for the manufacture of existing and advanced titanium alloy aeroengine components and structures. Both aspects of the joining technique, i.e. 'solid-state ' and '…
Thin layers of ZnO were grown on (0001) oriented sapphire by organometallic chemical vapor deposition. Low-temperature photoluminescence indicates that near-band-edge luminescence dominates the spectrum. In contrast to bulk grown material deep level luminescence for the layers is relatively weak.
Electron paramagnetic resonance of trivalent terbium ions is reported in a glass based on zirconium fluoride at liquid helium temperatures and at frequencies in the range 9 to 30 GHz. The results are interpreted as arising from a nonKramers doublet ground state with g/sub ///=17.3+or-0.5, A/sub ///=0.209+or-0.001 cm -…
An overview of the synthesis and characterization of a unique class of polymers with a phosphorus-nitrogen backbone is presented, with a focus on poly(dichlorophosphazene) as a common intermediate for a wide variety of poly(organophosphazenes). Melt and solution polymerization techniques are illustrated, including the…
Organometallic polymer precursors offer the potential to manufacture shaped forms of advanced ceramic materials using low temperature processing. Polysilazanes, compounds containing Si-N bonds in the polymer backbone, can be used as precursors to silicon nitride containing ceramic materials. This chapter provides an o…
When bonds are removed one by one and at random from a finite-size resistor network, the conductance (or resistance) does not change continuously, but rather a sequence of conductance (resistance) jumps for various sizes occurs. The larger jumps arise from those bonds which carry a relatively large current just before…
The epipelic diatoms from various water bodies from the south-western part of the Hornsund fiord area are presented. Altogether, 157 taxa (127 species together with their variants and forms) have been identified. The flora consists almost entirely of diatoms from the order Pennales which is represented predominantly B…
Films were produced by pulsed laser evaporation of various solid polymer targets in vacuum. Smooth films and relatively low deposition power thresholds (<107 W/cm2 peak) were observed for strongly absorbed ultraviolet wavelengths. Poorly absorbed wavelengths gave powdery deposits. For many polymers the evaporat…
Heavy metal fluoride glass materials are attractive for optical applications in the near ultraviolet through infrared wavelength regions. However, many compositions are relatively soft and hygroscopic, and possess low softening temperature (250°C-300°C). We have applied ion assisted deposition (IAD) techniques to depo…