Materials Literature
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We have found quite a new type of transport phenomenon in an organic crystal α-(BEDT-TTF) 2 I 3 under high pressure. Essentially, it is a semimetal or a narrow gap semiconductor. But, the transport property is peculiar. The conductivity of this the carrier (hole) density and mobility change by a about 6 orders of magn…
We report how the structural arrangement of germanium nanowires optimizes surface stability and enables the formation of very thin free-standing crystalline wires. Ge nanowires consisting of a crystalline Ge core and an amorphous ${\mathrm{GeO}}_{2}$ sheath have been formed by laser ablation of a mixture of Ge and ${\…
Using empirical potential molecular dynamics we compute dynamical matrix eigenvalues and eigenvectors for a 4096 atom model of amorphous silicon and a set of models with voids of different sizes based on it. This information is then employed to study the localization properties of the low-energy vibrational states, ca…
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O7-d as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O7-d and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by…
Using the photoluminescence Auger saturation phenomenon, we deduce the values of the absorption cross section of silicon nanocrystals in a wide range of energies. The very large variation of their values versus energy of the absorbed light is attributed to the enhanced optical transition oscillator strength but reduce…
A new technique, dissipative particle dynamics (DPD), appears promising as a means of studying the dynamical behaviour of polymers. Real polymers are known to obey a number of scaling laws, and a simulation method should reproduce these if it is to be relied on. The present work is a study of the properties of polymer…
In this article we report on the temperature dependencies of the longitudinal and shear sound velocities in Ti4AlN3, Ti3Al1.1C1.8, and Ti3SiC2. The velocities are measured using a phase sensitive pulse-echo ultrasonic technique in the 90–300 K temperature range. At room temperature, Young’s, ERT, and shear, μRT, modul…
High-speed optical communication requires ultrafast all-optical processing and switching capabilities. The Kerr nonlinearity, an ultrafast optical nonlinearity, is often used as the basic switching mechanism. A practical, small device that can be switched with ~1-pJ energies requires a large Kerr effect with minimal l…
Single molecule confocal microscopy is used to study fluorescence intermittency of individual ZnS overcoated CdSe quantum dots (QDs) excited at 488 nm. The confocal apparatus permits the distribution of “on” and “off” times (i.e., periods of sustained fluorescence emission and darkness) to be measured over an unpreced…
Scanning tunneling microscopy, spectroscopy, and tight-binding calculations have been used to elucidate the unique structural and electronic properties of single-walled carbon nanotubes (SWNTs). First, the unique relationship between SWNT atomic structure and electronic properties, and the richness of structures obser…
The cooperative Jahn-Teller coupling between the Mn e(g) electrons and the oxygen octahedral distortions in LaMnO3 is studied using ab initio density-functional calculations and tight-binding models. The linear and quadratic vibronic coupling parameters are calculated using density-functional methods. It is shown that…
We have developed the ability to grow reproducible La0.67Sr0.33MnO3/SrTiO3/Al tunnel junctions with high quality gap characteristics for spin-polarization measurements. A YBa2Cu3O7 counterelectrode was required to prevent current crowding. In order to fit our data, we have numerically solved Maki’s equations which inc…
The loss from polypropylene (PP) of sterically hindered amines with molecular weight ranging from 1364 to 2758 in heptane, chloroform, and methanol at room temperature was studied. The additives leak from polymer in heptane and in chloroform and some residual concentration remains in the polymer; the stabilizers show…
Results of the dynamic mechanical behavior of atactic polystyrene (PS) and high-impact polystyrene (HIPS) for temperatures between 300 and 425 K at a frequency of the order of 50 kHz are presented. The storage Young's modulus, (E′), of the HIPS is lower than the PS value, being the relationship between them a function…
The general behavior of the magnetostriction coefficients for Fe, Co, and Ni and their alloys is reproduced by first-principles theory. It is shown that the low magnetostriction coefficient of soft magnetic materials, observed for specific alloy concentrations, such as permalloy, can be explained theoretically by empl…
The kinetics of the bulk polymerization reaction of 1-iso-cyan-a-to-3-isocyanato methyl-3,5,5-trimethylcyclohexane or isophorone diisocyanate (IPDI) with poly(oxytetramethylene) glycol (POTM) was studied by 13C nuclear magnetic resonance (13C-NMR). The difference of reactivity of the NCO groups in this unsymmetrical d…
The optical properties of a new family of neodymium doped BPG (Bi2O3-PbO-Ga2O3 ) glasses are presented. We measured a high refractive index, of 2.5, and a transmission cutoff in the far infrared at 8microm. Three intense emission bands are observed centered at 877nm, 1066nm and 1341nm. The emission cross-section is 10…
During the plastic deformation of crystalline material the dislocations, being the carriers of the plastic flow, tend to form different patterns. Because of the long range nature of dislocation-dislocation interaction, the origin of this self-ordering phenomenon is still an open question. The paper presents a stochast…
A new class of biodegradable poly(ester-amide)s was prepared by a two step method. At first isosorbide or isomannide were esterified with α-amino acids in the presence of p-toluenesulfonic acid, and the resulting esters bisammonium tosylates were isolated. Second, the amino groups were liberated and polycondensed with…
Copolymers of ε-caprolactone and L-lactide (PCLLA) with different monomer ratio were synthesized by ring opening polymerization, and drug-loaded nanoparticles of poly-ε-caprolactone (PCL), poly-L-lactide (PLLA), and their copolymers were prepared by precipitation method, respectively. The results of differential scann…