Materials Literature
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The characteristics of PVC pyrolysis dechlorination has been studied in a fixed bed reactor under different operating conditions such as temperature, time, heating rate. It is found that about 90% chlorine in PVC can be effectively removed within 3 h with heating rate of 5 μ/min at temperature 300 °C, with 10% chlorin…
A series of ZnO films with various thicknesses were prepared on (0001) sapphire substrate by pulsed laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis were utilized to investigate the effects of thickness variation on the surface morphology and the crystallinity. The electr…
A series of axial and equatorial diastereomers of (coumarin-4-yl)methyl-caged adenosine cyclic 3',5'-monophosphates (cAMPs), 1-6, having methoxy, dialkylamino, or no substituent in the 6- and/or 7-positions, and their corresponding 4-(hydroxymethyl)coumarin photoproducts 7-12 have been synthesized. The photochemical a…
We propose a method to determine the direction of surface magnetization and local magnetic moments on the atomic scale. The method comprises high resolution scanning tunneling microscope experiments in conjunction with first principles simulations of the tunneling current. The potential of the method is demonstrated o…
The acoustic emission of fracture precursors, and the failure time of samples of heterogeneous materials (wood, fiberglass) are studied as a function of the load features and geometry. It is shown that in these materials the failure time is predicted with a good accuracy by a model of microcrack nucleation proposed by…
Throughout a complete electron spin resonance (ESR) and magnetization study of La0.5Ca0.5MnO3, we discuss about the nature of the complex phase-segregated state established in this compound below T∼210 K. Between TN⩽T⩽TC, the ESR spectra shows two lines characteristic of two different magnetic phases. From the resonan…
Nanocrystals of CuO and NiO have been produced by an alkoxide-based synthesis involving the corresponding metal chlorides, ethanol, and water. The resulting oxides are in the form of powders, with the CuO having crystallites in the size range of 7−9 nm and the NiO having crystallites in the size range of 3−5 nm. These…
Surface growth models may give rise to unstable growth with mound formation whose tipical linear size L increases in time. In one dimensional systems coarsening is generally driven by an attractive interaction between domain walls or kinks. This picture applies to growth models for which the largest surface slope rema…
We showed that a wetting layer in epitaxially strained thin films which decreases with increasing lattice mismatch strain arises due to the variation of nonlinear elastic free energy with film thickness. We calculated how and at what thickness a flat film becomes unstable to perturbations of varying size for films wit…
Mesoporous titanosilicates (MTS-9) are successfully prepared in strong acidic media by a two-step synthesis. MTS-9 has an ordered hexagonal structure and exhibits superior hydrothermal stability and high catalytic activity for the oxidation of the small molecules of phenol and styrene and also of the bulky molecule of…
The correlation between the structural (average size and density) and optoelectronic properties [band gap and photoluminescence (PL)] of Si nanocrystals embedded in SiO2 is among the essential factors in understanding their emission mechanism. This correlation has been difficult to establish in the past due to the lac…
Dense ceramic composites consisting of two phases, ferroelectric BaTiO3 and ferrite (Ni0.3Zn0.7)Fe2.1O4, were synthesized via the solid state reaction route. The results indicate that insulating BaTiO3 can be well compatible to the conductive phase (Ni0.3Zn0.7)Fe2.1O4. The electrical conduction and dielectric behavior…
We present an interpretation of the x-ray absorption spectra of arsenic chalcogenide glasses, As4Se4 and As2Se3, from a first-principles calculation. Our calculation identifies the atomistic origins of the observed photoemission data. The importance of structural "building blocks" present in a particular glass to the…
Formulation of the Fourier modal method for multilevel structures with spatially adaptive resolution is presented, using a slightly reformulated representation for the spatial coordinates. Projections to Fourier base in boundary value problem are used allowing extensions to multilayer profiles with differently placed…
A generalized theoretical approach of the transverse susceptibility, χT, in the case of uniaxial ferromagnets is presented. This advances the classical model of transverse susceptibility where only the first-order anisotropy constant, K1, is taken into account and makes possible the study of the influence of the secon…
Spectral dependence of two-photon absorption in a chalcogenide glass, As2S3, has been studied using a tunable light source. The result shows that two-photon and two-step absorptions occur, and the two-photon absorption spectrum appears to be exponential. These results and roles of nonlinear processes in photoinduced p…
We consider the $t\ensuremath{-}J$ model for doped manganites, and show that double exchange for correlated ${e}_{g}$ electrons favors in the ferromagnetic metallic phase an orbital liquid (i.e., orbital-disordered) state. Therefore the spin-wave stiffness is isotropic, and increases with hole doping x, providing a di…
We have employed the quartz-crystal microbalance technique to measure the sliding friction of krypton films physisorbed on gold. By slowly increasing the amplitude of the substrate oscillations, we have observed a sharp transition from a film locked to the substrate to a sliding one. This transition is characterized b…
Branching structure in carbon nanotubes (CNT) are of great importance in developing CNT-based mechanical or electrical applications. For this purpose, CNTs exhibiting two-dimensional and three-dimensional junctions are being sought. Among them, only two-dimensional branching structures of Y-junction and T-junction CNT…
Based on epitaxial layer transfer silicon on insulator wafers, crystalline Si/SiO2 quantum wells have been made. The chemical composition of the quantum wells was studied by Auger electron spectroscopy depth profile. The crystalline structure of the well was confirmed by x-ray photoelectron diffraction. Band-edge shif…