Materials Literature
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Abstract A sol‐gel granulation process was developed to prepare porous nanostructured γ‐alumina granules as supports for catalysts and adsorbents. The process, which starts with an aqueous sol of gelatinous boehmite, involves droplet formation, gelation in paraffin oil, conditioning in ammonia solution, and drying and…
The excitation and radiative recombination mechanisms of carriers in electroluminescent porous silicon (PS) have been studied for the device with the structure of Au/PS/n-type Si. Experiments focus on the electroluminescence (EL) and photoluminescence (PL) spectra, the current-voltage-EL intensity relationship and its…
The birefringence induced by partially ordered polymer networks dispersed in an isotropic phase of liquid crystals is studied. Polymer networks were formed by the polymerization of 1--4 % mixtures of prepolymer in the nematic phase of liquid crystals. The partial nematic (paranematic) ordering is analyzed in terms of…
The surface reduction of amorphous poly(aryl ether ether ketone) (PEEK) film was successfully achieved by wet chemistry using a solution of NaBH 4 in DMSO at 120 °C for 3 h. The resulting PEEK-OH film was fully characterized by MIR, UV−visible, and 1 H NMR spectroscopies; all the data were consistent with those of the…
Mandelate racemase (EC 5.1.2.2) catalyzes the abstraction of a proton from a carbon atom adjacent to a carboxylate function, a reaction which is kinetically and thermodynamically unfavorable. Proton NMR spectroscopy and polarimetry were used to measure the rates of deuterium incorporation into the alpha-position of ma…
Three series of copolymers have been prepared by the reaction of a mesogenic methacrylate, 6-((4-((4-methoxyphenyl)azo)phenyl)oxy)hexyl methacrylate, with either 4-vinylpyridine, 2-vinylpyridine or styrene. These copolymers were blended with either a mesogenic acid, 6-((4-((4-methoxyphenyl)azo)phenyl)oxy)hexanoic acid…
We present the results of ab initio calculations of the spin-polarized electronic structure of disordered bcc ${\mathrm{Cr}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Fe}}_{\mathrm{x}}$ and ${\mathrm{Mn}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Fe}}_{\mathrm{x}}$ alloys. The self-consistent calculations we…
Perovskite PbTiO 3 powders were prepared by a polymerized complex technique at relatively low temperatures, viz. 400−600 °C. Heating of a mixed solution of citric acid (CA), ethylene glycol (EG), and Pb and Ti ions with a molar ratio of Pb/Ti/CA/EG = 1/1/10/40 at 130 °C produced a yellowish transparent polymeric gel w…
A simple derivation is given to arrive at an expression for the Coulomb energy of a polar crystal with emphasis on its dependence on the external form of the crystal. It is found that the existing treatments are incomplete, since they refer to the central cell in the crystal, which may have an energy different from th…
This article relates to an investigation of injection moulding a new commercial polymer, an aliphatic polyketone (PK). A terpolymer and a 30% glass-filled grade were used as study materials together with an isotactic polypropylene that was used as a basis for comparison. Both conventional injection moulding and shear-…
To study the size effects in ferroelectric thin film, we measured the optical transmittance and Raman spectra in BaTiO3 thin films deposited by the rf-magnetron sputtering technique on fused quartz and (111) Si substrates. A variation in the energy gap and Raman peaks with film thickness and grain size was observed an…
Dihydrodipicolinate synthase (DHDPS) catalyzes the formation of dihydrodipicolinate from pyruvate and L-aspartate beta-semialdehyde (ASA). A parallel initial velocity pattern that displays competitive substrate inhibition by ASA and dead-end inhibition patterns obtained at pH 8 are consistent with a ping pong kinetic…
The coverage dependencies of the differential heats of adsorption for CO and NO on Pd{100}, at room temperature, are reported using single crystal adsorption calorimetry (SCAC). The initial heat for CO is 165 kJ/mol, falling markedly with increasing coverage due to anomalously strong repulsive interactions between mol…
Elastic forces within very lightly cross-linked seed latex particles are able to compete with interfacial forces to influence latex particle morphology. At higher levels of cross-linking the elastic forces dominate those at the interfaces. PMMA seed latices were prepared at (nominally) 0, 0.015, 0.10, and 0.2 mol % (b…
Abstract The viscoelastic properties of fourteen syndio‐ and isotactic polypropylenes (PPs) were measured in the molten state at several temperatures by means of oscillatory rheometry. Metallocene catalysis allows the control of molecular mass of both PP families and provides narrow molecular mass distributions (MMD)…
Organic compounds in aqueous solution submitted to an ultrasonic irradiation behave differently according to their physical and chemical properties. In this work, degradation rate of phenol and carbon tetrachloride, has been studied at different frequencies, 20 kHz, 200 kHz, 500 kHz and 800 kHz. Whatever the frequency…
New hybrid organic−inorganic materials which incorporate the bisimide functionality were synthesized by sol−gel condensation of bisimide monomers containing pendant triethoxysilyl groups. Monomers were prepared by transimidation of bis (2-aminopyridyl)imides with (3-aminopropyl)triethoxysilane. This synthesis was appl…
Diffusion profiles have been recorded in situ and evaluated using an optical technique. In this way, bulk diffusion coefficients have been reliably and quantitatively measured. It is shown that the values agree with calculations without using adjustable parameters if the coupling of the diffusing species to internal r…
Molecular dynamics simulations have been used to examine the friction between the hydrogen-terminated (111) faces of diamond with small hydrocarbon (third-body) molecules trapped between them. In general, the presence of the trapped third-body molecules reduced the friction between the diamond surfaces with the most p…
The synthesis of controlled molecular weight semicrystalline polyimides based on 1,3-bis(4-aminophenoxy)benzene (TPER diamine) and 3,3‘,4,4‘-biphenyltetracarboxylic dianhydride (BPDA), end capped with phthalic anhydride, is reported herein. The above polyimide henceforth referred to as TPER polyimide ( M n = 20k, 30k)…