Materials Literature
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We report 27 Al and 29 Si Nuclear Magnetic Resonance (NMR) spectra, collected at magnetic fields of 14.1 and 18.8 Tesla on samples as small as 1 mg, for Al‐bearing MgSiO 3 perovskite synthesized at 26–28 GPa. For Al, we find a 1∶1 ratio of two types of sites: a symmetrical, octahedral site and a low symmetry, distorte…
The thermal oxidation of polypropylene was probed, in situ, by a novel technique that simultaneously monitors chemically induced light emission (chemiluminescence) and changes in FTIR emission spectra of an oxidizing sample. The results obtained from this technique demonstrated that the chemiluminescence intensity ( I…
Relaxation dynamics of electrons in gold nanocrystals with diameters of 3.0--17.5 nm embedded in ${\mathrm{SiO}}_{2},$ ${\mathrm{Al}}_{2}{\mathrm{O}}_{3},$ and ${\mathrm{TiO}}_{2}$ matrices have been investigated by means of femtosecond pump and probe spectroscopy. The experiments show that the energy relaxation rates…
Shell-core structures of Fe(C), Co(C) and Fe-Co(C) nanocapsules, prepared by an arc discharge process in a mixture of methane and helium, have been demonstrated by means of high-resolution transmission electron microscopy (HRTEM). These nanoscale magnetic cores are protected by graphite shells. It has been found that…
The mechanical stability of amorphous carbon (a-C) films deposited on ultrasmooth Si(100) substrates by radio-frequency sputtering under different energetic ion bombardment conditions was investigated in light of results obtained from aging and annealing experiments. The a-C films were annealed at 495 °C in the high-v…
The mechanism for the pressure-induced transformation of cristobalite to stishovite and post-stishovite phases has been obtained from constant pressure ab initio molecular dynamics simulations. The cristobalite to stishovite transformation is found to be a two step process where ${\mathrm{SiO}}_{4}$ tetrahedra first r…
A density-functional theory of the isotropic–nematic phase transition in both rigid and semiflexible hard-sphere chain fluids is described. The theory is based on an exact analytical evaluation of the excluded volume and second virial coefficient B2 for rigid chain molecules, which demonstrates that B2 in these cases…
We present the first results on (0001) ZnO/(0001) epi-GaN/(0001) α-Al 2 O 3 heterostructure fabrication combining metal-organic vapour phase epitaxy and low-pressure chemical vapour deposition methods. The surface morphologies of the films were studied, and x-ray and reflection high-energy electron diffraction measure…
Fully saturated hydrocarbon polymers often exhibit superior stability toward thermal, oxidative, and radiation-induced degradation. Recent improvements in catalyst technology allow for the convenient synthesis of the saturated hydrocarbon poly(cyclohexylethylene) (PCHE) from polystyrene (PS) by heterogeneous catalytic…
Fluorinated surfaces are sought for a number of technologies requiring low surface energy, low adhesion, chemical robustness, among other desired properties. Bulk fluorinated materials (e.g., polymers) can be used, but their relative expense and difficult processing problems preclude widespread application. Small mole…
The structures of PrAlO 3 have been studied from room temperature to 10 K, using a combination of high resolution neutron and synchrotron powder diffraction data. At room temperature, PrAlO 3 has a rhombohedral structure in space group R c which transforms to an orthorhombic structure in Imma on lowering the temperatu…
We report on ${}^{13}\mathrm{C}$ nuclear magnetic resonance from $10$ up to $350$ K on single wall carbon nanotubes. The magic angle spinning NMR spectrum shows one isotropic line at $126$ ppm and the static spectrum a powder pattern typical for a curved graphene sheet. The T dependence of the spin-lattice relaxation…
Nanocomposite (Pr,Dy)2Fe14B/α-Fe magnets with compositions Pr8−xDyxFe86B6 (x=0, 0.5, 1, 1.5, and 2) have been synthesized by melt spinning using low wheel speeds in the range from 18 to 21.7 m/s. It has been found that the coercivity is significantly increased by Dy substitution. An optimum coercivity of 6.6 kOe is ob…
High-speed experimentation techniques have been applied in the synthesis and testing of silsesquioxane-based titanium catalysts (see picture) for the epoxidation of alkenes. Different solvents and organotrichlorosilanes were employed in the optimization of the hydrolytic condensation of silanes to open silsesquioxane…
Transamination reactions of [{(Me3Si)2N}2Sm(thf)2] with the dianion of either 1,1-di-(α-pyrrolyl)cyclohexane or diphenyl dipyrromethane led to the octanuclear complex shown in the picture and the hexanuclear complex [{[Ph2C(α-C4H3N)2]Sm}6(thf)3], respectively. Both clusters possess flat macrocyclic structures and reac…
We have reported conductivity spectra at different temperatures for fluoride glasses of compositions 0.50ZrF4–(0.40−x)BaF2–0.10YF3–xNaF in the frequency range from 10 Hz to 2 MHz. We have analyzed the spectra using conductivity formalism and obtained the frequency exponent, concentration, and hopping frequency of char…
By locating all relevant transition structures with a hybrid density functional method, we explored the three most reasonable mechanisms for H2O2 epoxidation of propenol catalyzed by methyltrioxorhenium (MTO), namely: (i) coordination of propenol as lone pair donor to rhenium mono- and bis-peroxo complexes followed by…
We have grown LaCa(4)O (BO(3))(3) (LaCOB), an isostructural member of GdCa(4)O(BO(3))(3) (GdCOB) family and characterized its nonlinear optical properties. At 1064nm, d(eff) of 0.52+/-0.05 pm /V and an angular sensitivity of 1224+/-184(cm rad)(-1) for type I frequency doubling in LaCOB were determined relative to thos…
Stable free radicals can be trapped inside a three-dimensional (3D) inorganic network. The formation of a new type of mixed-metal oxalate [MnII(H2O)CrIII(ox)3]− is induced by the presence of a cationic nitronyl nitroxide radical (rad+). The figure shows a stylized view of the 3D network ○ = Mn, • = Cr). This hybrid or…
We apply the Mori-Zwanzig projection operator formalism to obtain an expression for the frequency dependent specific heat $c(z)$ of a liquid. By using an exact transformation formula due to Lebowitz et al., we derive a relation between $c(z)$ and $K(t),$ the autocorrelation function of temperature fluctuations in the…