Materials Literature
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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)…
The relation between the suspension state and the rheological properties, the consolidation, and packing of a very fine (nanosized) BaTiO 3 powder has been investigated. The BaTiO 3 powder was suspended in a nonaqueous medium by adsorbing fatty acids and a polymeric dispersant, poly(12‐hydroxy stearic acid), (PHS), at…
In recent years there has been a rapid development in the area of temperature-resistant thermosets. Polyimides in particular are gaining wide acceptance by the industry because they combine a number of unique features, including excellent physical property retention at elevated temperatures and in wet environments, al…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDendritic Catalysts: Reactivity and Mechanism of the Dendritic Bis(oxazoline)metal Complex Catalyzed Diels−Alder Reaction†Chi Ching Mak and Hak-Fun ChowView Author Information Department of Chemistry, University Science Centre, Chin…
Abstract A critical overview of different synthetic approaches to poly( p ‐xylylene)s (PPXs) is coupled with perspectives on particular structure–property relationships and challenging applications. An attempt is made to emphasize the potential of different synthetic approaches to PPXs focused on different application…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTTunable Redox and Optical Properties Using Transition Metal-Complexed PolythiophenesJerry L. Reddinger and John R. ReynoldsView Author Information Center for Macromolecular Science and Engineering, Department of Chemistry, Universit…
One-dimensional Fibonacci-class quasilattices are proposed and studied, which are constructed by the substitution rules B\ensuremath{\rightarrow}${\mathrm{B}}^{\mathrm{n}\mathrm{\ensuremath{-}}1}$ A, A\ensuremath{\rightarrow}${\mathrm{B}}^{\mathrm{n}\mathrm{\ensuremath{-}}1}$ AB. We have proved that this class of bina…
An approach to material strain tolerance, which basically makes it possible to lower the elastic modulus while retaining strength, was experimentally confirmed using as an example a porous silicon nitride composed of oriented anisotropic grains and pores. The porous structure consisting of tightly tangled rodlike grai…