Materials Literature
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The kinetics of the site exchange reaction of Al 3+ cations between tetrahedral and octahedral sites in MgAl 2 O 4 and ZnAl 2 O 4 spinel in natural and synthetic powdered samples was determined by 27 Al MAS‐NMR spectroscopy with a high‐speed magic‐angle‐spinning probe using samples heat‐treated for different time peri…
Many chemical and physical methods, such as plasma, e-beam, sputtering, CVD and others, have been used to modify the structure of polymer surfaces by depositing thin inorganic films. Most of these techniques are based upon the use of high energy sources that ultimately can damage either chemically or physically polyme…
We present a model for the motion of hard spherical particles on a two-dimensional surface. The model includes both the interaction between the particles via collisions and the interaction of the particles with the substrate. We analyze in detail the effects of sliding and rolling friction, which are usually overlooke…
A renewed interest in the Laue diffraction technique has been brought about by the development of new, more intense and brilliant synchrotron sources along with their insertion devices such as wigglers and undulators, and by the prospect of using these sources to study structural dynamics by time-resolved crystallogra…
The conventional 1 M NH 4 OAc‐exchangeable potassium (K + ) soil test is inadequate in soils where nonexchangeable K + contributes significantly to crop nutrition. Studies were conducted (i) to compare the abilities of the 1 M NH 4 OAc method with a modified NaBPh 4 method to estimate critical soil K + levels, (ii) to…
Due to the ubiquitous presence of a Berry phase, in most cases of dynamical Jahn-Teller systems the symmetry of the vibronic ground state is the same as that of the original degenerate electronic state. As a single exception, the linear H x h icosahedral model, relevant to the physics of C60 cations, is determined by…
The correlation between the spin polarization of the tunneling current in ferromagnet/Al2O3/Al tunnel junction experiments and the magnetic moment in ferromagnets has been a mystery [Phys. Rev. B 16, 4907 (1977) and Phys. Rep. 238, 173 (1994)]. In this study, an attempt is made to explain this correlation. By assuming…
The ab initio linear muffin-tin-orbital formalism and the semiempirical method of the intermediate neglect of the differential overlap based on the Hartree-Fock formalism are combined for the study of the hole polarons (a hole trapped nearby the cation vacancy) in a cubic phase of ${\mathrm{KNbO}}_{3}$ perovskite crys…
A resonant method based on a tunnel-diode oscillator for precision measurements of relative impedance changes in materials is described. The system consists of an effective self-resonant LC tank circuit driven by a forward-biased tunnel diode operating in its negative resistance region. Samples under investigation are…
Continued innovations in the polymer industry have made polymer surface modification methods a subject of intense research. The importance and necessity of surface modification of plastics are explained, and the advantages of physical surface treatments over the less-sophisticated chemical methods are outlined. Curren…
This article compares the cure behavior and properties of phthalonitrile polymers derived from three different monomers, namely, 4,4′-bis(3,4-dicyanophenoxy)biphenyl, 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]hexafluoropropane and 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]propane. Rheometric measurements with monomer melt in th…
A range of methods for the detection of barium carbonate contaminant in barium titanate powder has been assessed, namely: X‐ray diffraction (XRD), scanning electron microscopy (SEM), with EDS‐X‐ray microanalysis, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), gas chromatography (GC)…
Transparent and conductive thin films of multicomponent oxides composed of binary and/or ternary compounds with varied chemical compositions have been prepared by rf or dc magnetron sputtering. Transparent conducting oxide (TCO) films were prepared in multicomponent oxides composed of ZnO, SnO2, Ga2O3, or MgO combined…
Thermal decomposition of boehmite and bayerite has been studied by X-ray diffraction and by NMR and IR spectroscopies. Coordination and site distortion of Al polyhedra have been estimated by 27 Al NMR spectroscopy while IR optical properties of transitional aluminas, η-, γ-, δ-, and θ-Al 2 O 3 were derived from IR nea…
Abstract Poly(lactide) (PLA), a biodegradable aliphatic polyester with excellent properties for different polymer applications, has been used mostly in the biomedical field, mainly because of its high price, resulting from expensive polymerization and purification techniques. Although this polymer can play a major rol…
Arsenic contamination of groundwater has recently commanded widespread public attention. Under many conditions, arsenic, and certain other environmentally relevant toxic metals such as chromium, exist in nature as oxyanions. Selective binding of anions is one of the most challenging problems in chemistry, biology, and…
The melting behavior of isothermally crystallized poly(butylene succinate) (PBS) has been investigated using differential scanning calorimetry (DSC) and wide-angle X-ray analysis. The samples crystallized between 80°C to 100°C show middle endotherm at the position just before the high exotherm, while the others under…
A high‐pressure burner rig was developed to evaluate the response of chemical‐vapor‐deposited SiC material during exposure to simulated gas turbine combustor conditions. Linear weight loss and surface recession rates of SiC were observed in both fuel‐lean and fuel‐rich gas mixtures. This response was shown to result f…
Internal stresses in tension and compression in an extruded and artificially aged Mg-7.7at.% Al alloy have been determined by in-situ neutron diffraction. Measurements were made on grains having the c axis normal to, parallel to and at 62° from the stress axis, and on the reinforcing phase. The results are consistent…
In combustion environments, volatilization of SiO 2 to Si‐O‐H( g ) species is a critical issue. Available thermochemical data for Si‐O‐H( g ) species were used in the present study to calculate boundary‐layer‐controlled fluxes from SiO 2 . Calculated fluxes were compared to volatilization rates of SiO 2 scales grown o…