Materials Literature
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We have synthesized samples in the system CaTi 1 - x Fe x O 3 - x /2 with x = 0.05 - 0.38 at temperatures of 900 - 1320 °C under controlled conditions of oxygen fugacity. After drop quenching, samples were characterized by x-ray diffraction, transmission electron microscopy (TEM) and Mössbauer spectroscopy. Electrical…
Most stable structures and physical properties are studied for silicon-doped ${\mathrm{Al}}_{13},$ ${\mathrm{Al}}_{19},$ and ${\mathrm{Al}}_{23}$ clusters using the ab initio molecular-dynamics method within the framework of a plane-wave pseudopotential approach and the local density as well as the generalized gradien…
The surface loss probabilities of hydrocarbon radicals on the surface of amorphous hydrogenated carbon (C:H) films are investigated by depositing films inside a cavity with walls made from silicon substrates. This cavity is exposed to a discharge using different hydrocarbon source gases. Particles from the plasma can…
We have investigated, in single crystals of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3},$ the insulator-metal (IM) transition at the ground state induced by carrier doping or applying pressure around the critical doping level ${(x}_{c}\ensuremath{\approx}0.22).$ The up turn of the resistivity…
Transient photoconductivity in thin-film ${\mathrm{Nb}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ and ${\mathrm{TiO}}_{2}$ was studied as a function of temperature, light intensity, illumination time, and ambient composition in a time range of ${10}^{\ensuremath{-}2}--{10}^{7}\mathrm{s}.$ Both excitation an…
Ultrasonic microspectroscopy technology, using the line-focus-beam and plane-wave ultrasonic material characterization system, is applied to characterization of silica glass. Eight types of commercial silica glasses fabricated by different production methods and conditions are used as specimens to measure their acoust…
Luminescence and excitation spectra of ${\mathcal{R}}^{3+}$-doped thorium oxide $({\mathcal{R}}^{3+}={\mathrm{Eu}}^{3+}{,\mathrm{}\mathrm{Dy}}^{3+})$ are reported and analyzed. ${\mathrm{ThO}}_{2}$ was synthesized and grown as crystal using the flux technique. Usually, ${\mathcal{R}}^{3+}$ ions substitute ${\mathrm{Th…
A “coupling to” approach was developed for the synthesis of hybrid dendritic–linear block copolymers. Fréchet-type polyether dendrons were prepared by the convergent growth approach and coupled with well-defined functionalized polystyrene backbones prepared by living free radical procedures. The subtle interplay betwe…
The chronic inflammatory response associated with the abluminal surface of polymeric vascular grafts has been suggested to affect adversely graft neovascularization, the cellular response at the luminal surface of vascular grafts, and overall graft patency. To better understand the source for this chronic inflammation…
Photoemission and x-ray absorption spectroscopy have been used to study silicon nanowires prepared by a laser ablation technique together with Si(100) and porous silicon. Si $2p$ and valence-band spectra show that the Si nanowires are essentially crystalline Si encapsulated by silicon oxide. HF etching removes the sur…
A thermally stimulated luminescence (TSL) study in the temperature range 20--300 \ifmmode^\circ\else\textdegree\fi{}C has been performed after x-ray irradiation on mixed ${\mathrm{Lu}}_{x}{\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{AlO}}_{3}:\mathrm{C}\mathrm{e}$ crystals $(x=0.1--0.3)$ and on ${\mathrm{YAlO}}_{3}:\mathrm…
Activated carbon fibers (ACFs) are microporous carbons consisting of a three-dimensional disordered network of nano-graphites with a mean in-plane size of about 30 Å. We investigated the structure, electronic properties and iodine doping effects for ACF samples heat-treated up to 2800° C. The samples heat-treated belo…
The competitive ablation and polymerization (CAP) principle relates the ablation of materials in plasma to the deposition of materials in plasma. Plasma polymerization and plasma treatment cannot be elucidated without consideration of the fragmentation of molecules in both the gas and solid phases. The general fragmen…
By a judicious choice of implantation and annealing conditions, an n-type conducting layer with activation energy of about 0.32 eV has been created in oxygen-implanted diamond. This conclusion was reached as a result of performing three similar implantations in identical, high-purity (type IIa) diamonds. They have bee…
We have measured high resolution absorption spectra for the ${}^{4}{\stackrel{\ensuremath{\rightarrow}}{{I}_{15/2}}}^{4}{I}_{13/2}{,}^{4}{I}_{11/2}$ infrared transitions of ${\mathrm{Er}}^{3+}$ ions in ${\mathrm{LiYF}}_{4}.$ Positions of crystal-field levels and their widths were precisely determined and analyzed. Hyp…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTRational Synthesis of Meso-Substituted Porphyrins Bearing One Nitrogen Heterocyclic GroupDorota Gryko and Jonathan S. LindseyView Author Information Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204 Cite this: J. Org. Chem. 2000, 65, 7…
A novel flame-retardant epoxy resin, (4-diethoxyphosphoryloxyphenoxy)(4-glycidoxyphenoxy)cyclotriphosphazene (PPCTP), was prepared by the reaction of epichlorohydrin with (4-diethoxyphosphoryloxyphenoxy)(4-hydroxyphenoxy)cyclotriphosphazene and was characterized by Fourier transform infrared, 31P NMR, and 1H NMR analy…
Recently discovered boron nitride (BN) nanoscale cone particles are shown to consist of an ordered stacking of seamless conical shells. High-resolution transmission electron microscopy and nanobeam electron diffraction allowed the orientation of the BN hexagonal rings to be determined. In all but one case, the results…
Recrystallization and structural recovery in -decay damage in zircon samples have been studied using Raman spectroscopy. Fifteen zircon samples with different degrees of radiation damage have been thermally annealed between 600 K and 1800 K for up to 28 days and 8 hours. The experimental results from this study reveal…
The analysis of Raman spectra obtained for different germanium nanostructures grown on silicon substrates is presented. Comparison of these spectra with a Raman spectrum of a silicon wafer reveals a one-to-one correspondence of features located around 229, 300, and 435 cm−1. It is argued that the peaks observed at the…