Materials Literature
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Abstract The degradation of organic compounds in water is the subject of a number of fundamental and applied investigations. Aquasonolysis of organic compounds is an advanced technology for the purification of contaminated water. The process is based on the phenomenon of acoustic cavitation. Dominant reactions of vola…
Dibenzylidene sorbitol (DBS) is a low-molecular-weight organic molecule that can gel a variety of organic solvents and polymers by self-organizing into a three-dimensional nanofibrillar network through hydrogen-bonding and phenyl interactions. In this work, we investigate the composition dependence of such “organogels…
In part 1 of this series, we proposed a new method to determine the correct equilibrium melting temperature ( T m 0 ). Effects of the “melting kinetics” and lamellar thickening were omitted from T m . The correct T m 0 of isotactic polypropylene (iPP) ([ mmmm ] = 99.6%, M n = 64 × 10 3, and M w / M n = 2.4) was observ…
A new theory for the dynamics of concentrated colloidal suspensions and the colloidal glass transition is proposed. The starting point is the memory function representation of the density correlation function. The memory function can be expressed in terms of a time-dependent pair-density correlation function. An exact…
Novel biodegradable star-shaped polymers that consist of poly( l -lactide) (PLLA) arms and a starburst PAMAM dendrimer core were prepared by ring-opening polymerization of l -lactide with PAMAM-OH dendrimer (generation 1−4) initiators and a stannous octoate catalyst in bulk at 130 °C. The molecular weights of the star…
A new method to determine the correct Gibbs−Thomson plot and equilibrium melting temperature ( T m 0 ) of polymers was proposed. The Gibbs−Thomson plot method is reliable, because the Gibbs−Thomson equation is directly derived from thermodynamical relations. In this method, the heating rate dependence of melting tempe…
The DC transport properties of and the radio-frequency (RF) wave absorption (at 1.33 MHz) in a ceramic sample of La_{0.5}Sr_{0.5}CoO_{3-δ} are measured. The Curie temperature, T_{c}, of the sample is about 250 K. A giant negative magnetoabsorption effect is found. In the vicinity of T_{c}, the absolute value of the ma…
The relaxation of axisymmetric crystal surfaces with a single facet below the roughening transition is studied via a continuum approach that accounts for step energy g_1 and step-step interaction energy g_3>0. For diffusion-limited kinetics, free-boundary and boundary-layer theories are used for self-similar shapes cl…
We complete our earlier [Phys. Rev. B 66, 134435 (2002)] study of the electronic structure, exchange interactions, and Curie temperature in (GaMn)As and extend the study to two other diluted magnetic semiconductors (GaCr)As and (GaFe)As. Four concentrations of the $3d$ impurities are studied: 25, 12.5, 6.25, 3.125 %.…
In the present article, a detailed study of the optical properties of the Er-doped Si nanocrystals system, obtained through ion implantation of Er in samples containing Si nanocrystals formed by plasma enhanced chemical vapor deposition is reported. In particular, we present a phenomenological model based on an energy…
Nonlinear optical response and optical coherence of excitons in semiconductor dense quantum dots in GaAs single quantum wells has been studied by using photon echo techniques. At low temperatures, the optical coherence is estimated to be 2 ns from the decay curve in the photon echo signal. Rabi oscillations are also o…
The superconducting properties of copper-sheathed MgB2 wires fabricated by conventional powder-in-tube techniques and the in-situ reaction procedure are analysed. The influence of the processing conditions and initial (1+x)Mg + 2B (x = 0, 0.1, 0.2) proportions of the precursors on the critical current values of the wi…
Cu(OH) 2 and CuO nanoribbon arrays aligned approximately perpendicular to copper substrate surfaces are synthesized by the solution-treatment and subsequent heat-treatment processes. The Cu(OH) 2 nanoribbons are fabricated by a simple coordination self-assembly method in an alkaline solution with Cu 2+ ions being from…
We report different approaches to the synthesis of size series of highly luminescent CdSe/CdS core−shell nanocrystals. The mixture of hexadecylamine (HDA)−trioctylphosphine oxide (TOPO)−trioctylphosphine (TOP) as stabilizing solvent was found to be very suitable for one-pot synthesis of nearly monodisperse CdSe nanocr…
Prepared within biocompatible poly(amidoamine) dendrimer hosts, blue emitting Au8 nanodots were prepared with fluorescence quantum yields more than 100 times larger than any previously prepared. The strong size-dependent blue emission from these from monodisperse Au8 nanodots was measured to be 41% in aqueous solution…
The local environment surrounding ferromagnetically ordered Mn in Mn/GaAs digital layers and (Ga, Mn)As random alloys has been selectively probed using a combination of local structural information obtained by x-ray magnetic circular dichroism (XMCD) and extended x-ray absorption fine structure (EXAFS) techniques. The…
Melting of semicrystalline polymers typically occurs over a temperature range of 10 °C or more, throughout which the long period L increases by 50%−100%. Less recognized is the evolution of the small-angle X-ray scattering (SAXS) pattern from peaked to monotonic before the final stages of melting. These two features a…
The structure evolution of iPS during isothermal cold-crystallization and subsequent melting processes is studied by in situ monitoring its FTIR spectra. Through following the intensity changes of the characteristic bands associated with its crystalline status and 3 1 helix conformation chains, the multiple melting be…
The paper explores the capacity of small angle neutron neutron scattering (SANS) to characterize the dispersion of an exchanged clay in an organic solvent. As an illustration, results are reported for 1% and 2% by mass suspensions of a representative commercial complex, known as Cloisite, C15A in toluene. C15A is prep…
Aromatic poly(ether−ketone)s having pendant carboxyl groups have been obtained by direct, one-pot, Friedel−Crafts copolycondensation of 4,4‘-diphenoxybenzophenone with a mixture of terephthaloyl chloride (TC) and trimellitic anhydride acid chloride (TAAC), over a wide range of TAAC/TC molar ratios, in the presence of…