Materials Literature
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A single crystal has been the subject of a combined investigation by high-resolution x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES) with both electron and energy-selective x-ray excitation ( , and emission) and x-ray absorption spectroscopy (XAS) . We performed first-principles tight-binding…
The first self-consistent computations of piezoelectricity in a ferroelectric are presented. Bulk spontaneous polarization, dynamical charges ( ${Z}^{*}$), and the full piezoelectric stress tensor of ${\mathrm{PbTiO}}_{3}$ were determined from ground-state Berry's phase calculations using the all-electron linearized a…
The piezoelectric and dielectric constants in different crystal orientations of the lead zirconate titanate (PZT) have been phenomenologically calculated for the compositions near the morphotropic phase boundary at room temperature. For a tetragonal PZT, the effective piezoelectric constant d33 monotonously decreases…
With the help of band structure calculations $(\mathrm{LSDA}+U)$ a clear picture of the physics behind the metallic ferromagnetic properties of ${\mathrm{CrO}}_{2}$ is revealed. It is concluded that ${\mathrm{CrO}}_{2}$ is a negative charge transfer gap material which leads to self-doping and explains why it is a meta…
Using a near-field optical antenna effect, we measure the homogeneous line shape of the surface-plasmon resonance in single gold nanoparticles. The surface-plasmon dephasing times extracted from the near-field spectra of the individual particles vary around 8 fs. This mean value agrees with calculations based on Mie t…
We propose a widegap II–VI semiconductor alloy, MgxZn1−xO, for the fabrication of heteroepitaxial ultraviolet light emitting devices based on ZnO. The c-axis oriented MgxZn1−xO films were epitaxially grown by pulsed laser deposition on ZnO epitaxial films and sapphire (0001) substrates using ceramic targets. Solid sol…
The first synthesis and characterization of sigma-bonded and N-substituted cobalt porphycenes is reported. The investigated compounds are represented as (Pc)Co(R) and (N-CH(3)OEPc)CoCl, where R is CH(3) or C(6)H(5), Pc is the dianion of 2,3,6,7,12,13,16,17-octaethylporphycene (OEPc), 2,7,12,17-tetrapropylporphycene (T…
The synthesis of novel bisaxially coordinated ruthenium(II) complexes of octaphenyltetraazaporphine (L(2)Ru(OPTAP); L = NH(3), pyridine (py), pyrazine (pyz), s-tetrazine (tz), tert-butyl isocyanide (t-BuNC), and p-diisocyanodurole (did)) is reported. Template condensation of diphenylfumaronitrile with pentaammine(dini…
The structural gradients developed along and across the flow direction of injection-molded PVDF and PVDF/PMMA parts were investigated by optical microscopy and thermal analysis techniques. The spatial variation of crystallinity across the thickness direction was found to be insensitive to the process variables: inject…
The degradation of poly(oxyethylene)–poly(ε-caprolactone) (POE–PCL) multiblock copolymers was investigated at 37°C in a 0.13M, pH 7.4 phosphate buffer selected to mimic in vivo conditions. The copolymers were obtained by coupling polycaprolactone diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide a…
The antimony-containing polymer of bisphenol-A (BPA) and triphenyl antimony dinitrate was used as a flame retardant (FR) for chloroprene rubber (CR) and natural rubber (NR). The flame retardancy of this additive was monitored by the limiting oxygen index (LOI) measurements of the rubber vulcanizates and compared with…
Tire rubber has been pyrolyzed at various temperatures under a nitrogen atmosphere. The resulting chars have been analyzed for their porosity using nitrogen gas adsorption and for their aqueous adsorption characteristics using phenol, methylene blue, and the reactive dyes Procion Turquoise H-A and Procion Red H-E3B. N…
A model of localized classical electrons coupled to lattice degrees of freedom and, via the Coulomb interaction, to each other, has been studied to gain insight into the charge and orbital ordering observed in lightly doped manganese perovskites. Expressions are obtained for the minimum energy and ionic displacements…
We present a phenomenological theory describing the self-similar coarsening stage in the collapse of a long flexible homopolymer chain in a dilute solution upon a sudden quench. The approach is based on the “necklace” picture of the collapsing chain being composed of clusters separated by strands as demonstrated by co…
Orientation behavior of acrylate-based liquid crystalline (LC) networks containing different types of cross-links is studied and discussed. Cross-links incorporated by chemical reaction with cross-linking agent presumably distort LC order, whereas cross-links induced by γ-irradiation preserve and even stabilize the ne…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTLow Band Gap Cyanovinylene Polymers Based on EthylenedioxythiopheneGregory A. Sotzing, Christopher A. Thomas, John R. Reynolds, and Peter J. SteelView Author Information Center for Macromolecular Science and Engineering, Department…
We report the results of a computer simulation of the evolution of structure in a two component fluid consisting of a liquid phase and a dispersed colloidal phase subjected to a biaxial field. A biaxial field, such as a rotating field, can induce the organization of polarizable particles into two-dimensional sheets, i…
Posttransfer modification of preformed Langmuir-Blodgett films of poly(tert-butyl methacrylate) and poly(tert-butyl acrylate) by gaseous hydrochloric acid yields films with layered architecture of poly(methacrylic acid) and poly(acrylic acid), respectively. X-ray reflectivity and infrared spectroscopy confirm monolaye…
A model polymer−solid interface, aluminum- (Al-) carboxylated polybutadiene (cPBD), was designed to investigate the influence of the sticker group (−COOH) on the fracture energy ( G IC ). A model polymer, cPBD, was synthesized through high-pressure carboxylation of polybutadiene (PBD) and contained −COOH randomly dist…
The optical transitions of neutral and charged oxygen vacancies in the bulk and on the surface of MgO have been studied by means of first principles calculations. Using rather large cluster models representing the MgO F+ and F centers, oxygen vacancies with one and two electrons trapped in the cavity, respectively, we…