Materials Literature
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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…
Extremely large spontaneous polarization (>10/sup -7/ C/cm/sup 2/) and permittivity (>10000) are observed in appropriately designed ferroelectric liquid crystals. The permittivity and its temperature dependence are found to be influenced strongly by the electric field and a wall effect. These results are discussed in…
This paper reports a new method of measuring the work function of meterials. The method is based on accurate measuring of energy distribution of secondary electrons and contact potential difference of meterials. We call it the method of secondary electron emission-contact potential difference (SEE-CPD method). The wor…
In order to investigate microscopically the effects of crystallinity and temperature on the fatigue crack growth behavior of polypropylene, the microfractographs were discussed based on the fatigue crack growth curves (a-N curves).The results obtained were as follows:(1) Two kinds of damage zone occurred at the crack…
A method of utilizing an adjustable-frequency controller (AFC) with a line bypass, to provide the energy saving potential of an AFC coupled with the inherent reliability of a simple magnetic starter, is presented. The proposed system allows the transfer of the motor between the AFC and the power line, even after a con…
Describes soil characteristics, uses, management, and productivity of vertisols in Ghana and discusses the potential for improved management using draught oxen. Includes recommendations.
The main object of this study is to examine the sintering behavior of pure materials in low pressure plasmas. Here, Mo, Al2O3, and Si3N4 were chosen as examples of metallic, ionic, and covalent materials. The compacts were heated in a radio frequency inductively coupled plasma under low pressure, N2, H2, Ar, and H2+Ar…