Materials Literature
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Employing absorption, excitation and luminescence spectroscopy in a wide spectral range, the upconversion processes are investigated in at low temperature. From the detailed analysis of the spectroscopic data and the power dependence of the upconverted intensity, excited state absorption and energy transfer between ex…
The authors report the design, fabrication and characterisation of a planar gradient index (GRIN) PECVD lens. The PECVD-based heilcon plasma reactor was used to deposit graded layers onto a silicon wafer. Ray tracing and beam propagation methods were used to simulate the periodic refocussing of the nominally parabolic…
Zinc oxide ceramic varistors with simplified compositions show nonlinear current - voltage characteristics with in the range 45 - 130. Addition of enhances the nonlinearity tremendously and the concentration range of needed for high is around 3 mol%. Formation and involvement of a liquid phase during sintering is indi…
The reinforcement of a natural rubber compound by various surface-modified precipitated silicas was compared. Compound physical properties were determined for two silicas differing in surface area and were used as controls to evaluate these silicas after surface modification by using either a bifunctional organosilane…
A model of vertical dynamic penetration of projectiles in granular soils was developed based on known experiments and the theory of dimensions. The depth of penetration is derived as a function of initial velocity and material properties. Velocity and acceleration are obtained as functions of time and depth of penetra…
The partial discharge activity (the number of discharges per second) during electrical tree growth in the flexible epoxy resin CY1311 was measured using a phase-resolved synchronous counting system. The experimental conditions, voltage and pin - plane spacing were varied to produce a wide range of tree structures from…
The real AC electrical conductivity was studied as a function of frequency f, temperature T and composition x for a series of samples prepared using the double-sintering ceramic technique. The experimental results indicated that increases as the temperature and frequency increase and as the Ni ion substitution decreas…
Flame reactors have high potential for synthesis of inexpensive nanosize powders since submicron size particles are made this way on an industrial scale at a rate of 100 ton/day. Thus, the formation of nanosize titania and silica powders by oxidation of TiCl 4 and SiCl 4 in a diffusion flame reactor were investigated…
Epoxy-clay nanocomposites have been synthesized by exfoliation of organoclays during the epoxy thermosetting process. The extent of silicate layer separation is governed by the chain length of gallery cations, the clay layer charge density and the acidity of the gallery cations. By using different curing agents, we ob…
We investigate the elastic properties of small droplets under compression. The compression of a bubble by two parallel plates is solved exactly and it is shown that a lowest-order expansion of the solution reduces to a form similar to that obtained by Morse and Witten. Other systems are studied numerically and results…
We present a new model to describe the unusual elastic properties of compressed emulsions. The response of a single droplet under compression is investigated numerically for different Wigner-Seitz cells. The response is softer than harmonic, and depends on the coordination number of the droplet. Using these results, w…
First-principles calculations have been performed in order to determine effective exchange integrals between {\it strongly} and {\it weakly} exchange-coupled Co monolayers in certain modulated periodic $CoCu_2/CoCu_n$-type superlattices with three non-equivalent Co planes, which have not yet been studied hitherto. For…
In order to understand the electronic structure of the incommensurate misfit layer compound we carried out an ab initio band structure calculation in the supercell approximation. The band structure is compared with that of the components and hypothetical SnS with a similar structure as in . The calculations show that…
We measure optically the dynamics of the nematic order parameter S induced by an electric field in the isotropic phase of the nematogenic 4\ensuremath{'}-n-pentyl-4-cyanobiphenyl. Using S as a thermometer, we observe transient heating and cooling when orientational order is induced, or decays. This electrothermal effe…
Highly oriented diamond films with {001} facets were grown on Si{001} using microwave plasma enhanced chemical vapor deposition. The tilt and rotation of the diamond crystals were measured by polar x-ray diffraction. The full widths at half-maximum of {004} and {220} diffraction peaks were 5° and 10°, respectively. It…
Using neutron spin echo and dielectric spectroscopy we have studied the molecular motions of 1-4 polybutadiene in the $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\beta}$ relaxation regime. At the first peak of the static structure factor the relaxation times follow the temperature dependence of the viscosity, while…
A structural study of a electric-field-induced ferroelectric phase has been performed using single-crystal x-ray diffraction and EXAFS techniques. The polar axis was found to be orthogonal to the direction of atomic displacements in the initial antiferroelectric phase. The ferroelectric properties of the phase are due…
compounds with x = 0, 0.5, 1.0, 1.5 and 2.0 have been studied in this paper. All compounds crystallize in the -type structure (space group, P6/mmm). The substitution of Ti for Mn in results in a linear increase in the lattice constants and the unit-cell volume from a = 5.531 Å, c = 9.025 Å and V = 239.10 at x = 0, to…
The critical splay-to-bend-alignment transition in a liquid-crystal cell treated by parallel rubbing (π cell) was investigated to improve the optical performance of the display mode using this cell with a compensator. By analyzing the free energy in liquid crystal cells, it was found that nematic media with a smaller…
Potassium niobate (KNbO3) thin films and potassium niobate/tantalate (KNbO3/KTaO3) superlattices have been grown on KTaO3 (001) substrates by pulsed laser deposition. The thin-film structures were analyzed by Rutherford backscattering/ion-channeling techniques, x-ray θ–2θ and Φ scans, and both conventional and Z-contr…