Materials Literature
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A quenchable superhard high-pressure carbon phase was synthesized by cold compression of carbon nanotubes. Carbon nanotubes were placed in a diamond anvil cell, and x-ray diffraction measurements were conducted to pressures of approximately 100 GPa. A hexagonal carbon phase was formed at approximately 75 GPa and prese…
The direct calculation of the elastic and piezoelectric tensors of solids can be accomplished by treating homogeneous strain within the framework of density-functional perturbation theory. By formulating the energy functional in reduced coordinates, we show that the strain perturbation enters only through metric tenso…
The electronic structure and magnetism in the sodium nickelate NaNiO_2 in the low-temperature phase is studied from density-functional calculations using the linear muffin-tin orbitals method. An antiferromagnetic solution with a magnetic moment of 0.7 m_B per Ni ion is found. A ferrodistorsive orbital ordering is sho…
We study the Aharonov-Bohm effect in the optical phenomena of single wall carbon nanotubes (SWCN) and also their chirality dependence. Specially, we consider the natural optical activity as a proper observable and derive it's general expression based on a comprehensive symmetry analysis, which reveals the interplay be…
Hole spin relaxation time due to the hole-acoustic phonon scattering in GaAs quantum dots confined in quantum wells along (001) and (111) directions is studied after the exact diagonalization of Luttinger Hamiltonian. Different effects such as strain, magnetic field, quantum dot diameter, quantum well width and the te…
We propose and numerically simulate novel reconfigurable logic gates employing spin metal-oxide-semiconductor field-effect transistors (spin MOSFETs). The output characteristics of the spin MOSFETs depend on the relative magnetization configuration of the ferromagnetic contacts for the source and drain, that is, high…
Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segre…
We observe field emission from an isolated nano-machined gold island. The island is able to mechanically oscillate between two facing electrodes, which provide recharging and detection of the emission current. We are able to trace and reproduce the transition from current flow through a rectangular tunneling barrier t…
Oxide superlattices and microstructures hold the promise for creating a new class of devices with unprecedented functionalities. Density-functional studies of the recently fabricated superlattices of lattice-matched perovskite titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential originating from the C…
We report the first experimental evidence of a magnetic phase arising due to the thermal blocking of antiferromagnetic clusters in the weakened charge and orbital ordered system ${\mathrm{P}\mathrm{r}}_{0.5}{\mathrm{C}\mathrm{a}}_{0.5}{\mathrm{M}\mathrm{n}}_{0.975}{\mathrm{A}\mathrm{l}}_{0.025}{\mathrm{O}}_{3}$. The t…
Self-assembly of robust perylenediimide chromophores is used to produce an artificial light-harvesting antenna structure that in turn induces self-assembly of a functional special pair that undergoes ultrafast, quantitative charge separation. The structure consists of four 1,7-(3',5'-di-tert-butylphenoxy)perylene-3,4:…
"Green" nanocomposites have been successfully fabricated from cellulose acetate (CA) powder, eco-friendly triethyl citrate (TEC) plasticizer and organically modified clay. The effect of the amount of plasticizer varying from 15 to 40 wt % on the performance of the nanocomposites has been evaluated. The morphologies of…
Abstract Two novel two‐tail surfactants, dicetyldimethylammonium 4‐vinyl benzoate (DDVB) and dicetyldimethylammonium 3,5‐divinyl benzoate (DDDB), were synthesized by neutralizing the corresponding quaternary ammonium hydroxide with the appropriate benzoic acid. As expected, these surfactants formed both homo and mixed…
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Abstract Summary: The isothermal crystallization process of poly( ε ‐caprolactone) (PCL) and its blend with styrene‐acrylonitrile random copolymer containing 27.5 wt.‐% acrylonitrile has been investigated as a function of crystallization and melting temperatures for different melting times in the vicinity of the lowes…
The layer-by-layer (LBL) assembly of a polypeptide, poly-L-lysine (PLL), with poly(styrenesulfonate) sodium salt (PSS) on flat template-stripped gold (TSG) surfaces precoated with a self-assembled monolayer of alkanethiols terminated with positive (pyridinium), negative (carboxylic acid), and neutral [hexa(ethylene gl…
We report results of computer simulations of the deformation and failure behavior of a thin crystalline strip of "hard disks" in two dimensions confined within a quasi-one-dimensional "hard-wall" channel of fixed width corresponding to a few disk diameters. Starting from a commensurate triangular solid, stretching the…
Abstract A novel aryl trifluorovinyl ether monomer, 1,1,1‐tris(4‐trifluorovinyloxyphenyl)‐2,2,2‐trifluoroethane ( 5 ), was prepared via a multistep reaction sequence adapted from previously reported procedures. Monomer 5 polymerizes by free‐radical mediated thermal cyclodimerization to produce a crosslinked perfluoroc…
Abstract Most of commercial dosimetric phosphors consist of suitably doped polycrystalline compounds. Whereas the activation issue has been usually addressed, less attention has been paid to the influence of host preparation in the final perfomance of the products. In this paper different routes have been followed to…
Y 4 Al 2 O 9:Pr 3+ was prepared by two methods: starting from the citrates and direct sintering of the oxides. The latter method gave more single-phased samples. Optical spectroscopy was utilized to obtain the emission spectra from the individual sites of the crystal structure. Absorption, excitation spectra, and site…