Materials Literature
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The new oxygen-ion conductor La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-x has been prepared by conventional solid-state reaction at high temperatures and characterised by X-ray diffraction, scanning and transmission electron microscopy, and conductivity (four-probe dc and impedance) measurements. The room-temperature structure i…
Electrical wear-out and dielectric breakdown of insulating polymers involve dissipation to the lattice of the energy of mobile or trapped space charges. Optical emissions are proof of such energy releases and can be used to define the onset of electrical aging and to investigate the dissipation mechanisms. They also c…
In a real system the heating is nonuniform, and a second-order phase transition to a broken-symmetry phase occurs by propagation of a temperature front. Two parameters, the cooling rate τ Q and the transition front velocity ν T determine the nucleation of topological defects. Depending on the relation of these paramet…
This paper presents a new arc furnace model which copes with the two main voltage disturbances normally associated with arc furnaces: voltage fluctuations; and harmonics. The model is based on the stochastic nature of the electric arc current-voltage characteristic. The model has been estimated from measurements made…
The Current Status of IPNs Phase Separation During Synthesis of Polyetherimide/Epoxy Semi-IPNs A Review of Kinetic Studies on the Formation of IPNs IPNs Based on Polyurethane and Poly(butyl-methacrylate): Interrelation Between Reaction Kinetics and Microphase Structure Latex IPNs: From Structures to Properties Poly(et…
CO chemisorption on Pt catalysts supported on non-acidic alumina prepared from platinum acetylacetonate has been studied by FTIR spectroscopy. The stretching frequency for isolated CO species is observed at 2032 cm−1 for highly dispersed Pt samples (dispersion 0.99) and at 2067 cm−1 for poorly dispersed samples (dispe…
This paper presents nanoscopic aspects of electronic aging in dielectrics, as the result of the interaction of excess non-thermalized carriers with the media. Hot electrons are hypothesized as the major source of non-thermal carriers and shown to be a decisive factor in electrical breakdown. The interaction of hot ele…
BACKGROUND AND OBJECTIVE: Linear birefringence is an anisotropic property of rat tail tendon, which is largely composed of collagen. Our goal is to show that the dynamic range and sensitivity of the linear birefringence loss of collagen during heating are sufficient for kinetic modeling of the reaction. STUDY DESIGN,…
A new, ambient-temperature method for the direct synthesis of organo-substituted polyphosphazenes is described. It involves the initiation of a series of organophosphoranimines R(R‘)XP NSiMe 3 ( 3, R = Ph, R‘ = X = Cl; 5, R = R‘ = Ph, X = Cl; 7, R = Me, R‘ = Et, X = Cl; 9, R = R‘ = CF 3 CH 2 O, X = Br) with catalytic…
Ruthenium porphyrin and porphycene complexes catalyse stereospecific cyclopropanation of styrenes; high product turnovers with up to 90.8% ee were achieved with the [Ru(P*)(CO)(EtOH)] catalyst (H 2 P* = chiral D 4 porphyrin).
The crystal structure of the R-phase was determined by combined use of the electron diffraction and the powder X-ray diffraction method. The Rietveld method was applied for the analysis of the powder diffraction data. The structure of the R-phase belongs to the space group P3 and is similar to that of ζ′2 Au–Cd marten…
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Peter Hoppe, Ulrich Ott; Mainstream silicon carbide grains from meteorites. AIP Conference Procee…
The reaction of silica gel with 3-(trimethoxysilyl)propane-1-thiol, MPTS, produced a thiol-modified silica gel, Sil–SH. This material removes silver, mercury, copper, zinc and nickel ions from aqueous solutions. Enthalpy changes that occur in the interactions between Sil–SH and these cations were obtained by a calorim…
Radiation grafted and sulfonated poly(vinylidene fluoride), PVDF, membranes have been studied by thermal analysis and X-ray diffraction to determine the changes in membrane crystallinity and structure during preparation. Commercial PVDF films were irradiated with an electron beam, grafted with styrene and finally sulf…
We have used digital video microscopy to study the equilibrium structure of quasi-two-dimensional suspensions of sterically stabilized uncharged polymethylmethacrylate spheres. The spheres are confined between the surfaces of a very thin glass cell. Our experiments reveal the existence of an equilibrium hexatic phase…
Nature learned long ago how useful proteins are as a diverse set of building blocks to make materials with very diverse properties. Spider webs, egg whites, hair follicles, and skeletal muscles are al
Both spirooxazine and spiropyran dyes have been embedded into two different hybrid matrices, which were formed from hydrolysis and cocondensation between diethoxydimethylsilane and zirconium propoxide and between methyldiethoxysilane (DH) and triethoxysilane (TH) respectively. The nature and the kinetics of the photoc…
The physico-chemical properties of biodegradable polylactide-co-glycolide (PLGA) microspheres containing the peptide salmon calcitonin (sCT) were affected by the processing parameters. The microsphere size increased with an increase in the viscosity of the polymer solution. Concentration of methanol and peptide in the…
Carbon films have been produced on the surface of β-SiC particles by reaction with Ar–Cl 2 and Ar–Cl 2 –H 2 gas mixtures at atmospheric pressure and temperatures of 600–1000 °C. The structure and composition of the carbon films have been investigated using XRD, SEM, EDS, TEM, FTIR and Raman spectroscopy. BET and TG we…
Palladium grafted mesoporous MCM-41 materials, prepared by vapor grafting, show remarkable activity in Heck carbon–carbon coupling reactions.