Materials Literature
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Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may als…
Hygrothermal aging at elevated temperatures tends to induce degradation in epoxy resins. To predict the effects of this degradation, a knowledge of absorption and transport behavior of water is needed. In this work, a model material (DGEBA/DDA) has been employed to study the water absorption and absorption/desorption…
The ring-opening polymerization of lactide cyclic monomers in the bulk in the presence of tin(II) 2-ethylhexanoate (stannous octoate or SnOct2) was reexamined under conditions allowing for the end group characterization of growing chains by high-resolution 1H-NMR. Data collected for low values of the monomer/initiator…
This article reports a new method of forming protective coatings on metal surfaces. The process is very simple and environmentally friendly. Polymerization occurs spontaneously on the metal surface after the immersion of a cleaned metal substrate into a dominantly aqueous monomer solution. A layer of coating with unif…
Cure kinetics for the formation of copolyurethane networks of various compositions based on hydroxy-terminated polybutadiene (HTPB), poly(12-hydroxy stearic acid-co-TMP) ester polyol(PEP), and different isocyanates has been studied through viscosity build up during the cure reaction. The viscosity(N)—time (t) plots co…
Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. It is also a useful method for preparation of polymers with unusual monomer sequences. Natural rubber (NR) could be quantitatively hydrogenated to a strictly alternating eth…
A new process that combines the excellent morphology control of Ti-based catalysts with the unique features of polyolefins from mettalocenes has been devised. First, propylene is polymerized with the Ti-based catalysts, having spherical form; then, activated mettalocene catalysts are introduced into the porous PP sphe…
Evaluation of different types of lignins and lignin derivatives, representing a spectrum of significant differences in regard to delignification processes and the nature of wood, in blending with a rigid poly(vinyl chloride) (PVC) compound for outdoor application is discussed. The influence of lignins on the processab…
Low-field tunneling magnetoresistance was observed in films of half-metallic CrO2 that were grown by high-pressure thermal decomposition of CrO3. High-temperature annealing treatments modified the intergrain barriers of the as-grown films through surface decomposition of CrO2 into insulating Cr2O3, which led to a thre…
We show that Bayesian inference, like that used in statistical mechanics, can guide the systematic construction of Fourier dark-field methods for localizing periodicity in near-field (e.g. scanning-tunneling and electron-phase-contrast) images. For crystals in an aperiodic field, the Fourier coefficient Ze^{i phi} com…
We investigate the cooling rate of a gas of inelastically interacting particles. When we assume velocity dependent coefficients of restitution the material cools down slower than with constant restitution. This behavior might have large influence to clustering and structure formation processes.
The synthesis of polypropylene (PP) oligomer—clay intercalation compounds was studied by using three kinds of PP oligomers and organophylic clay. PP oligomers were two types of maleic-anhydride-modified PP oligomers containing different amount of maleic anhydride groups and one type of hydroxy modified PP oligomer. Or…
Lattice relaxations, surface phonon spectra, surface energies, and work functions are calculated for Rh(100) and Rh(110) surfaces using density-functional theory and the full-potential linearized augmented plane wave method. Both, the local-density approximation and the generalized gradient approximation to the exchan…
We present a comment on a recent letter by B. Edwards, N.W. Ashcroft, Nature 388 (1997) 652, in which the dielectric instabilty of the phase III of the solid molecular hydrogen system is suggested on the basis of electrostatics.
In this note microgels with and without excluded volume interactions are considered. Based on earlier exact computations on Gaussian mircogels, which are formed by self-crosslinking (with $M$ crosslinks) of polymer chains with chain length $N$ Flory type approximations are used to get first insight to their behavior i…
The elpasolite compound lead magnesium tellurate undergoes a structural phase transition at about 194 K. This phase transition has been characterized by calorimetry, by dielectric permittivity measurements and by Raman spectroscopy. The main features of the Raman spectra, collected between 35 K and room temperature, a…
We study a model for the nematic--to--smectic- $A$ (NA) transition in aerogel, and find that even arbitrarily weak quenched disorder (i.e., low aerogel density) destroys translational (smectic) order. Ignoring elastic anharmonicities, but keeping anharmonic couplings to disorder, leads to the prediction that there is…
Novel field emission devices with electron path lengths an order of magnitude less than the elastic mean free path of electrons in air have been fabricated and tested at atmospheric pressure. The nanoscale-tip field emission system consisted of multiple emitter tips of radii about 1 nm within an extractor aperture of…
Crystallographic orientations between thin-sputtered Cu film and β-Ta adhesion layer have been studied using high resolution electron microscopy and electron diffraction. Tetragonal β-Ta deposited on SiO2 has a strong texture with its closest packed plane (002) parallel to the film surface. On (002) β-Ta, the growth o…
The surface structure of nonstoichiometric ${\mathrm{CeO}}_{2}(111)$ has been studied by scanning tunneling microscopy (STM). By using extremely small tunneling currents it was possible to obtain the first ever reported atomically resolved images of this oxide. STM imaging was possible at a sample bias voltage between…