Materials Literature
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A New Monte Carlo code (EBUF) is developed to calculate improved point isotropic photon exposure buildup factors in media. Variance reduction techniques are used to perform calculations up to 60 mean free paths. EBUF accounts for coherent scattering and bound-electron Compton scattering. Bremsstrahlung photons and ann…
Self-reinforced silicon nitride ceramics with additions of either yttrium oxide or ytterbium oxide have been investigated at room temperature after various processing heat treatments. Devitrification of the intergranular phase in these materials is very sensitive to the heat treatment used during processing and does n…
Two series of MgCuZn ferrites are prepared by addition of Ta5+ and Pb2+ ions, separately. The variations of the sintered density, initial permeability, saturation magnetization, Curie temperature and electrical resistivity with the dopant concentration have been studied. The sintered density was found to increase when…
The activities of a several titanium-based constrained geometry metallocenes (CGM) have been examined with respect to their central-metal net charges. A simple method consisting of a combination of the molecular mechanics and the charge equilibration method was adopted here to determine the structure and the net charg…
It was found that use of hydrophilic poly(ethylene oxide) (PEO) as a dispersion agent could disstack phthalocyanine (PC) in water and enhance its luminescence quantum yield. A combination of laser light scattering, UV−vis, and fluorescence spectroscopy was used to study the PEO/PC interaction. Our results revealed tha…
Abstract Structure determination or refinement by diffraction methods on solid solutions containing more than one type of central ion in certain ployhedra of their crystal structures, e.g. (M 1-x M x ′)O 6 octahedra, yield crystal-averaged mean distances R̅(M 1-x M x ′)-O depending on the site fraction x M′i of the su…
The dynamics of a model for amorphous and supercooled silica (SiO2), a strong glass former, is studied using instantaneous normal mode (INM) analysis. The INM spectra at a variety of temperatures are calculated via molecular dynamics simulation. At temperatures below the glass transition temperature, the dominant cont…
We report, to our knowledge, the first polarization-resolved measurement of the frequency dependence of both the electronic and the electrostrictive contributions to the dc Kerr coefficient in silica. At the acoustic resonance the perpendicular polarization phase shift is a factor of 2.3 times greater than in the para…
From cathodoluminescence (CL) investigations of synthetic and natural calcium phosphates it can be concluded that the CL of pure synthetic apatite is mainly characterized by intrinsic luminescence, whereas the luminescence of naturally occurring apatites is frequently activated by trace elements. CL revealed internal…
Abstract Integrated processes for nylon and polyester production were simulated. The polyester process includes four stages: esterification, prepolycondensation, finishing stage, and solid‐state polycondensation. Three stages are involved in the nylon process: prepolycondensation, melt polycondensation, and the solid‐…
Ceramic matrix composites containing TiB2 as a particulate phase have been produced by hot pressing. The problems of the reactivity of TiB2 with the Si3 N4 matrix and with the sintering environment have been successfully addressed. A novel dual atmosphere sintering profile combined with low temperature hot pressing ha…
The use of fibre-reinforced polymer matrix composite materials is growing at a faster rate than the gross domestic product (GDP) in many countries. An improved understanding of their processing and mechanical behaviour would extend the potential applications of these materials. For unidirectional composites, it is pre…
A numerical hopping model is developed to investigate the temperature dependence of electrical conductivity in a distribution of localized states. An exponential energy dependence of the density-of-states (DOS) distribution (N 0/E 0)exp(E/E 0) is assumed, together with a high DOS value (1 × 1018-1 × 1021cm−3 eV−1) at…
Abstract Degradation of poly(butylene terephthalate) (PBT) induced by blending time at 260°C leads to an increase of both carboxylic end groups and melt viscosity index and a decrease of the molecular weights. Crystallization kinetics of pure PBT and PBT blended with and epoxide, which was used to reduce the free carb…
The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffract…
This review examines in some detail the effect of introducing nitrogen-containing fused heterocycles into the molecular core of calamitic liquid crystals on their physico-chemical properties. The results of this study are compared with those obtained for other molecular fragments, and are rationalized in terms of exis…
This review surveys the work developed in the field of functional hybrid materials, especially those containing conducting organic polymers (COPs), in combination with a variety of inorganic species, from molecular to extended phases, including clusters and nano-sized inorganic particles. Depending on the dominating s…
Abstract The three step synthesis of pentadecavanadate, (n-Bu4N)4[V15O36(Cl)] has been achieved by a stepwise growth process. The reaction of (n-Bu4N)VO3 with [(η3-C4H7)PdCl]2 gives a tetravanadate supported organometallic compound [{(η3-C4H7)Pd}2V4O12]2−. The thermal decomposition of [{(η3-C4H7)Pd}2V4O12]2− leads to…
High-resolution X-ray diffraction of high-purity multiwall carbon nanotubes has been performed and unusual diffraction physics was observed. Fourier analysis confirms that the multiwall nanotubes are made of concentric cylinders and that there is a non-uniform distribution of inner tube diameter. The interference effe…
The purpose of this study was to clarify the effect of the reducing agent on the oxygen-inhibited layer of the cross-linked reline material. A commercial autopolymerizing reline resin containing 1,6-hexanediol dimethacrylate as cross-linking agent and 1 wt.% sodium sulphite solution as a reducing agent was prepared. T…