Materials Literature
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Halogenation and addition of some heavy metallic oxides have been in use for a few decades to impart flame-retarding properties to polymers. In this study bromine was added to the polymer (polyester of propylene glycol + phthalic anhydride) by means of decabromodiphenyloxide (DBDPO) at varying concentrations. In addit…
The biodegradability of low density polyethylene (LDPE)/starch and LDPE/starch/starch acetate (STAc) blends was tested and observed to be dependent on STAc content. The binary and ternary blends containing up to a maximum concentration of 30% starch were examined for their thermal, mechanical, and morphological proper…
An amorphous selenium network structure was constructed by combination of a lattice random walk and ab initio molecular dynamic (MD) simulation. The static structure factor, pair correlation function, and vibrational and electronic density of states simultaneously agree with experiment. For the first time, we study st…
The electron dynamics is studied in silver nanoparticles of different sizes embedded either in a silicate glass or in a porous alumina matrix, using time-resolved optical spectroscopy. The femtosecond pump–probe measurements, made under various conditions of excitation, reveal that the energy relaxation is faster as t…
Scaling of the ferroelectric and piezoelectric properties in Pt/SrBi2Ta2O9/Pt thin films was studied. Focused ion beam milling was used to fabricate submicron devices (1×1, 0.5×0.5, 0.25×0.25, 0.09×0.09, and 0.07×0.07 μm2) and scanning force microscopy was used to examine their piezoelectric response. It was found tha…
Neutral $\mathrm{Ti}{}_{8}\mathrm{C}{}_{12}$ and $\mathrm{Ti}{}_{14}\mathrm{C}{}_{13}$ clusters are produced in the gas phase with pulsed-nozzle laser vaporization. Infrared multiphoton excitation with a pulsed free-electron laser results in thermionic electron emission for these clusters, and the parent molecular ion…
Optical experiments, involving photoluminescence (PL), the PL excitation and quenching spectra, as well as transmission and its quenching, were used to analyse the photochromic behaviour of some vacancy-related complexes in diamond. The 2.156 eV, 1.945 eV and 1.68 eV optical centres in CVD diamond are attributed to th…
Polycrystalline ordered double perovskite Sr2FeMoO6 bulk samples with grain size in the range of 29–45 nm have been synthesized at temperatures from 900 to 1000 °C, using a sol-gel method. We find that the intergrain magnetoresistance is closely correlated with the grain size. The sample with the grain size of 29 nm s…
We investigate the growth of B-doped carbon nanotubes combining experimental and theoretical techniques. Electron microscopy observations and electron diffraction patterns reveal that B doping considerably increases the length of carbon tubes and leads to a remarkable preferred zigzag chirality. These findings are cor…
The resistivity and magnetoresistance of a magnetite single crystal and Fe 3 O 4 films of various thicknesses were measured in the temperature range 70 K< T <300 K and in magnetic fields in the range -1 T µ 0 H 1 T. The magnetoresistance depends on both current and magnetic field direction. The anisotropic magnetoresi…
The fluctuation-dissipation theorem (FDT), connecting dielectric susceptibility and polarization noise, was studied in glycerol below its glass transition temperature ${T}_{g}$. Weak FDT violations were observed after a quench from just above to just below ${T}_{g}$, for frequencies above the $\ensuremath{\alpha}$ pea…
The physical properties of the new high-pressure spinel phase of ${\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ and ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ were studied by first-principles calculations. The presence of Si at the octahedral site and the elongated Si-N bonds under pressure have a profound effect on many properties of $…
Epitaxial zinc oxide films have been prepared on gallium nitride (0002) substrates by cathodic electrodeposition in an aqueous solution containing a zinc salt and dissolved oxygen at 85 °C. The films have the hexagonal structure with the c axis parallel to that of GaN and the [100] direction in ZnO parallel to the [10…
An explanation is given for the charge order, orbital order, and insulating state observed in half-doped manganese oxides, such as ${\mathrm{Nd}}_{1/2}{\mathrm{Sr}}_{1/2}{\mathrm{MnO}}_{3}$. The competition between the kinetic energy of the electrons and the magnetic exchange energy drives the formation of effectively…
Direct beam x-ray imaging, with intense coherent monochromatic synchrotron radiation and a fast readout low noise detector has been used for in situ studies of cellular and dendritic solidification of Sn-Pb alloys. Temporal and spatial resolutions down to $\ensuremath{\sim}0.7\mathrm{s}$ and $\ensuremath{\sim}2.5\ensu…
We calculate the properties of $p\ensuremath{-}n$ junctions, $n\ensuremath{-}i$ junctions, and Schottky barriers made on a single-wall carbon nanotube. In contrast to planar bulk junctions, the depletion width for nanotubes varies exponentially with inverse doping. In addition, there is a very long-range (logarithmic)…
We address the effects of disorder on the conducting properties of metal and semiconducting carbon nanotubes. Experimentally, the mean free path is found to be much larger in metallic tubes than in doped semiconducting tubes. We show that this result can be understood theoretically if the disorder potential is long ra…
We report the first ab initio density-functional study of <111> screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Co…
Spectroscopic and magnetic studies on α-Li 3 Fe 2 (PO 4 ) 3 show an interesting behavior below the transition temperature (29 K). The compound orders antiferromagnetically, presenting a weak ferromagnetic moment, which diminishes with temperature. In the same region of temperatures, the Mössbauer spectra split in two…
Siloxane-anchored monolayer films are best prepared by the self-assembly of trichlorosilanes. The moisture sensitivity and chemical reactivity of the trichlorosilane moiety complicates the synthesis and purification of the ω-functionalized alkyltrichlorosilanes that are the building blocks for functionalized monolayer…