Materials Literature
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The main variables involved in solid-state polymerization of PET homopolymers, originally with molecular weight within the commercial range, were sequentially studied to determine their influence in polymerized products. These variables were precursor crystallinity, catalyst, and time and reaction temperature. An incr…
A high-temperature, high-pressure, tube furnace has been used to evaluate the long term stability of different monolithic ceramic and ceramic matrix composite materials in a simulated combustor environment. All of the tests have been run at 150 psia, 1204°C, and 15 percent steam in incremental 500 h runs. The major ad…
We report results on scanning force microscopy (SFM) studies of epitaxial SrBi2Ta2O9 films which, in conjunction with complementary x-ray diffraction, scanning and transmission electron microscopy data, allow us to establish direct correlation between the crystallographic structure at the submicrometer range and the n…
Die konformative Information, die in einem oligoheterocyclischen Strang aus sich wiederholenden Pyridin-Pyridazin-Kodons kodiert ist, löst einen allgemeinen Selbstorganisationsprozess aus, der zur spontanen Bildung helicaler Strukturen führt. Dabei entsteht zunächst eine helicale molekulare Einheit, die sich dann in D…
Measurement of magnetic susceptibility with temperature of a powdered iron(III) catecholate complex clearly indicated a two-step spin-crossover process S=½↔S=5/2. The picture shows the plot of χMT against temperature.
A series of 1,4-phenylene-bridged ZP-HP hybrid porphyrins (ZP = zinc porphyrin, HP = free-base porphyrin) 1-8 ZH have been prepared in which an electron-donating ZP moiety is kept constant and electron-accepting HP moieties are varied by introducing electron-accepting substituents, so that the energy gap for charge se…
The high propensity of organosilanes towards polycondensation and reaction with nucleophilic moieties has facilitated the formation of new organic-inorganic hybrids based on the lacunary divacant heteropolyanion [gamma-SiW10O36]8-. Depending on the experimental conditions two different types of derivatives were obtain…
Advantages of homo- and heterogeneous catalysts are united in metallodendritic molecules where nickel-based catalysts are bound to carbosilane dendrimers. The first direct indication of a "dendritic effect" in the redox catalysis behavior is described: variation of the dendrimer support controls the proximity of the N…
Various soluble polyimides with bis[4-(3-aminophenoxy)phenyl]sulfone and three kinds of dianhydrides were prepared in a polar N-methyl-2-pyrrolidone solvent by the traditional chemical two-step method. All the polymers synthesized had good solubilities in polar solvents and excellent thermal properties. Wide-angle X-r…
Thermal characteristics of chemically synthesized polyemeraldine base have been experimentally investigated using differential scanning calorimetry and thermogravimetric analysis (TGA), UV-visible, and Fourier transform IR techniques, respectively. Results of the TGA measurements have revealed that the chemically synt…
We present a new technique for porous semiconductor formation which is based on the exposure of semiconductor surfaces to gas phase etchants. The technique offers the possibility of fabricating light-emitting devices by selectively exposing a silicon surface to HF vapor. Photoluminescence measurements reveal an effici…
A nonionic surfactant (CMR-100) containing a mixture of C6–C22 sorbitan esters was tested to improve the filtration rate of phosphogypsum produced from a South Florida phosphate concentrate at different sulfate levels. Tests were carried out on a lab-scale under operating conditions that simulate, to a large extent, t…
Three different experimental techniques [compression experiments at low strain rates, instrumented falling-weight impact tests, and dynamic mechanical analysis (DMA)] have been used for the mechanical characterization of a collection of crosslinked closed-cell polyolefin foams of different chemical compositions, densi…
Recent advances in COI’s oxide–oxide CMC materials will be presented including basic processing steps, updated material properties, and fabrication techniques. Material properties of COI’s alumino-silicate system reinforced with various oxide fabrics will be compared, along with progress in developing a 1200°C oxide m…
Chitosan is effective at removing platinum from dilute solutions, but sorption properties are significantly affected by the presence of competitor anions, such as chloride and, especially, sulfate anions. Sorption capacities in such complex solutions are enhanced by grafting thiourea through glutaraldehyde linkage. Th…
During the last years, two new subjects among the others have raised interest in the field of small scale electric power generation: advanced microturbines and solid oxide fuel cells. This paper investigates the thermodynamic potential of the integration of the solid oxide fuel cell technology with microturbine system…
Simply dipping polyethyleneimine-modified surfaces into aqueous solutions of acid-functionalized Au55 clusters generates two-dimensional hexagonal and cubic arrangements of the clusters. The picture shows the transmission electron micrograph of the cubic arrangement; the bar length corrsponds to 10 nm.
Various segmented polyurethane materials with a polyurethane hard segment (HS) content of 40 wt % were prepared by bulk polymerization of a poly(tetramethylene ether) glycol with Mn of 2000, 1,4-butanediol, and various diisocyanates. The diisocyanates used were pure 4,4′-diphenylmethane diisocyanate (MDI), 2,4-toluene…
Simply dipping polyethyleneimine-modified surfaces into aqueous solutions of acid-functionalized Au(55) clusters generates two-dimensional hexagonal and cubic arrangements of the clusters. The picture shows the transmission electron micrograph of the cubic arrangement; the bar length corrsponds to 10 nm.
The strongest antiferromagnetic coupling to Gd(III) so far reported was found for the complex [Gd(Hbpz(3))(2)(dtbsq)] small middle dot2 CHCl(3) (1; Hbpz(3)=hydrotris(pyrazolyl)borate; dtbsq=3,5-di-tert-butylsemiquinonato; see structure). At 245 K the magnetic susceptibility of 1 is lower than expected for two uncorrel…