Materials Literature
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We report the results of high-level quantum-mechanical calculations on the optical transitions of a series of point defects in \ensuremath{\alpha} quartz. We determined all electron-configuration-interaction wave functions for cluster models of the following bulk defects: neutral oxygen vacancy, \ensuremath{\equiv}Si-…
A rapid screening and enrichment method is reported for exploring the size and shape diversities (libraries) of nanometer-scale colloidal particles. With the use of surface-enhanced Raman scattering, a new class of metal nanoparticles has been identified from heterogeneous silver colloids. These particles are relative…
The (110), (111), and (310) surfaces of cubic CeO 2 −ZrO 2 solid solutions have been studied by computer simulation techniques using atomistic models. Surface energies, Ce 4+ /Ce 3+ reduction energies, and penetration profiles of oxygen vacancy formation have been calculated. The results of the calculations suggest so…
Nanocrystalline diamond thin films have been synthesized in an Ar–CH4 microwave discharge, without the addition of molecular hydrogen. X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy characterizations show that the films consist of a pure crystalline diamond phase with very s…
Organic materials hold a large promise for second- and third-order nonlinear optical and fast electro-optic applications due to the large nonlinearities of the basic molecular units and the almost purely electronic origin of the nonlinearity. We here discuss the new development in this field with respect to molecules,…
Titanium-containing mesoporous materials, Ti-MCM-41 and Ti-MCM-48, have been successfully modified by trimethylsilylation to exhibit enhanced catalytic activity in the oxidation of alkenes and alkanes with H2O2.
The conductive properties of molecular wires constructed by columnar self-assembly of peripherally substituted large aromatic macrocycles are reported. The Figure illustrates how planar, disc-shaped aromatic molecules form a discotic liquid crystal (LC) phase consisting effectively of coaxially insulated wires of “one…
The possibility of using polysorbate 80-coated polybutylcyanoacrylate nanoparticles to deliver low molecular polar hydrophilic drugs to the CNS has been studied. Tubocurarine (a quaternary ammonium salt) does not penetrate the normal intact blood-brain barrier. However, the injection of this drug directly into the cer…
To further examine the structural and thermodynamic basis of hydrophobic stabilization in proteins, all of the bulky non-polar residues that are buried or largely buried within the core of T4 lysozyme were substituted with alanine. In 25 cases, including eight reported previously, it was possible to determine the crys…
Truncated rhombic dodecahedral crystals of the mesoporous molecular sieve MCM-48 are synthesised by a hydrothermal procedure using sodium silicate, hexadecyltrimethylammonium bromide and various kinds of alcohol.
A novel mesoporous silica with a tubular structure has been prepared using organic gel fibers as a template.
Aligned-nanotube bundles have been obtained in copious quantities by the pyrolysis of ferrocene or ferrocene–acetylene mixtures.
The isomorphous rutile-related network structures of Co(dca)2, Ni(dca)2 and Cu(dca)2, dca = dicyanamide, N(CN)2–, are shown to behave as ferromagnets (Tc = 9 and 20 K) and a near-paramagnet, respectively.
Directing the structure and function of polythiophenes (PTs) can lead to remarkable enhancements in the electronic and photonic properties of the resultant materials, as discussed in this comprehensive review of the chemistry and synthesis of PTs. The Figure illustrates the use of heteroatom-functionalized PTs as chem…
The hydrolytic sol-gel polymerization of molecular organosilicon precursors with a rigid geometry C6H4[Si(OMe)3]2-1,4 and C6H3[Si(OMe)3]3-1,3,5 2 was investigated and compared to the results obtained with precursors having a more flexible structure C6H4RR-1,4 [R=R=CH2Si(OMe)3 3; R=R=CH2CH2Si(OMe)3 4]. Compounds 1-4 ha…
The corrosion behavior of austenitic Fe-(17 wt% to 31 wt%) Mn-(1 wt% to 9 wt%) Al-(1 wt% to 7 wt%) Cr alloys in different aqueous solutions and the corrosion protection mechanism induced by adding Al or Al and Cr, were studied by anodic polarization and Auger electron spectroscopic/x-ray photo-electron spectroscopic (…
A highly conducting partially oxidized salt of TPP[Co(Pc)(CN)2 ]2 can be obtained by electrocrystallization of TPP[Co(Pc)(CN)2 ]. The crystal is composed of one-dimensional TPP arrays surrounded by slipped-stacked one-dimensional [Co(Pc)(CN)2 ] chains. The electrical conductivity at room temperature is quite high, 120…
A B S T R A C T: Arid soils in central Iran that evolved from the weathering ofpost-Tethyan sediments contain palygorskite. Clay fractions of gypsiferous oils and their associated sediments from different landforms from central Iran were investigated. Palygorskite was the dominant silicate clay mineral in clay fractio…
The evolution and interdependence of microstructure, stress, and bonding defects of heteroepitaxial diamond films deposited on silicon substrates has been investigated by applying scanning electron microscopy, transmission electron microscopy (TEM), and micro-Raman spectroscopy to the same places in the films. For thi…
Inelastic neutron-scattering spectra were measured to obtain the phonon density of states (DOS) of nanocrystalline fcc ${\mathrm{Ni}}_{3}\mathrm{Fe}.$ The materials were prepared by mechanical alloying, and were also subjected to heat treatments to alter their crystallite sizes and internal strains. In comparison to m…