Materials Literature
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Stabilized by the tailor-made coordination in the crystal, B4 tetrahedra were characterized for the first time in a solid-state structure (shown on the right). Some of the Al atoms are replaced by B4 tetrahedra in the cubic τ-boride Ni20AlB14. The B–B distances of 1.681(15) Å are similar to those in the molecular stru…
An F−/Cl− ligand exchange in the stable organopalladium fluoro complex 1 generates naked fluoride ions in unusually high concentrations. The released F− readily fluorinates dichloromethane under exceedingly mild conditions and deprotonates chloroform to produce dichlorocarbene.
The resistance of polycrystalline doped LaMnO3 materials has been shown to be highly sensitive to low magnetic fields. To enable direct study of the properties of isolated grain boundaries we have grown epitaxial La0.7Sr0.3MnO3 films on a series of bicrystal substrates with different misorientation angles and patterne…
The thermoelectric properties (resistivity and thermopower) of single crystals of the low dimensional pentatelluride materials, HfTe5 and ZrTe5, have been measured as a function of temperature from 10 K<T<320 K. The effect of small amounts of Ti substitutional doping (M1−xTixTe5, where M=Hf, Zr) on the t…
45 \AA{} diameter dodecanethiol capped gold nanocrystals self-organize during solvent evaporation on a carbon substrate, with the final thickness of the nanocrystal film depending on solvent polarity. A quantitative model for the film thickness is presented, showing the film structure (thickness) to depend on the bala…
The molecular dynamics of glass-forming liquids is strongly affected by nm-scale confinements. Our dielectric data provide strong evidence both for the ``cooperativity'' concept and for the existence of two states (interfacial layer and volume liquid). With decreasing size of confinement the orientational relaxation a…
Despite their larger separation, the porphyrin groups in 1 are more strongly conjugated than in analogous compounds in which butadiyne is the bridging unit. This stronger electronic coupling in 1 results in a bathochromic shift in its absorption and emission spectra.
Boron nitride nanotubes (BN-NTs) were synthesized by using excimer laser ablation at 1200 °C in different carrier gases. The main characteristic of the BN-NTs produced by this method is that nanotubes are of only one to three atomic layers thick, which could be attributed to the dominance of the axial growth rate over…
We show that the method used by Ogut, Chelikowsky and Louie (Phys. Rev. Lett. 79, 1770 (1997)) to calculate the optical gap of Si nanocrystals omits an electron-hole polarization energy. When this contribution is taken into account, the corrected optical gap is in excellent agreement with semi-empirical pseudopotentia…
Mechanically induced degradation of diamond, as occurs during polishing, is studied using total-energy pseudopotential calculations. The strong asymmetry in the rate of polishing between different directions on the diamond (110) surface is explained in terms of an atomistic mechanism for nanogroove formation. The post…
The structure of the skutterudite ${\mathrm{CoSb}}_{3}$ contains two large empty cages, or voids, per unit cell. Compounds obtained by filling these cages with rare earth atoms possess an enhanced thermoelectric figure of merit. Control of the electronic and thermal transport properties of these materials can be achie…
Abstract Optimization of foam treatments requires modeling or simulation of the process using a foam model that is capable of reproducing the critical properties of foam. The present work present a simple model that is based on the relative permeability concept, and is well suited for simulation of foam processes with…
Poly(ethylene terephthalate) (PET) and bisphenol-A polycarbonate (PC) are melt-mixed in equimolar ratios under various conditions to get a series of PET–PC copolymers. Samples from each copolymer are characterized by differential scanning calorimetry, 1H and 13C nuclear magnetic resonance (NMR), size exclusion chromat…
Crystalline structure were studied on both block and random propylene–ethylene copolymer fractions, which were obtained by temperature rising elution fractionation. The peak characteristic of α-polypropylene (PP) was observed for all fractions, except the fraction eluted at room temperature. A characteristic peak of p…
The present work compared the recrystallization process of Nylon 6 with Nylon 6.6 fibers. For such a study, the fibers were submitted to different annealing conditions (slack and restrained conditions) in a wide range of temperatures. For the structural analysis, several techniques were applied, and among them, differ…
Nylon 6 and 6.6 fibers were submitted to thermal annealing in a wide range of temperatures (below and above their glass transition temperatures) under inert atmosphere and slack condition, allowing free shrinkage. The structural changes due to the heat settings were analyzed by several techniques (differential scannin…
An investigation about the possibilities of atactic polypropylene in order to be chemically modified either in solution or in molten state processes, and further predictions about the reaction conditions' influence in the process, have been carried out. For those purposes the Box–Wilson experimental design method has…
The reactions between polymeric diphenyl methane diisocyanate (polymeric MDI) and conventional polyols to produce foamed polyurethane products are well documented and published. Current polyurethane foams are predominantly produced from these reactions whereby the polyol components are usually obtained from petrochemi…
The critical temperature of thin Fe layers on Ir(100) is measured through Mößbauer spectroscopy as a function of the layer thickness. From a phenomenological finite-size scaling analysis, we find an effective shift exponent lambda = 3.15 +/- 0.15, which is twice as large as the value expected from the conventional fin…
Novel solvent systems for cellulose are reviewed in terms of their potential for supporting chemical modification reactions that lead to highly engineered derivatives. Systems capable of sustaining homogeneous phase conditions include (1) dissolution with non-derivatizing solvents; (2) dissolution with partial derivat…