Materials Literature
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Abstract The radical polymerization of acrylic acid and sodium 4‐styrenesulfonate in the presence of chitosan as a template gives insoluble products, identified as the polyelectrolyte complexes chitosan‐poly(acrylic acid) and chitosan‐poly(4‐styrenesulfonate). Kinetic results do not permit to propose any mechanism in…
Abstract A backscattered electron energy spectrometer, based on a toroidal energy analyser and an annular detector, has been devised and adapted for use in a scanning electron microscope. Computer simulations have been carried out for equipotentials and trajectories of electrons in the toroidal deflector, which permit…
We have studied the scaling behavior of the bulk structure in a symmetric diblock copolymer system using small-angle scattering. We have identified a crossover between the inter mediate-segregation regime and the strong-segregation limit at χ N ≃ 29. In the inter mediate-segregation regime (χ N ≃ 5 − 29), the characte…
Abstract Ferroelectricity and thus piezoelectricity are well known features of low molar mass chiral smectic C (S c * ) liquid crystals. We present a new technique to orientate macroscopically the director as well as the smectic layers of a S c * ‐polymer network by applying a suitable mechanical field. The uniform or…
Interposition of a fine-scale X-ray absorbing mesh between a Laue-diffracting crystal specimen and the photographic plate recording its topographic image splits the diffracted beam into an array of individually identifiable microbeam elements. Direction differences between the microbeams in the array, which are twice…
Using light scattering, the thickness dependence of the isotropic-nematic phase transition temperature ${\mathit{T}}_{\mathit{NI}}$ in a thin film of octylcyanobiphenyl (8CB) is studied in two distinct geometries: with and without strain. We observed a large stress induced shift in ${\mathit{T}}_{\mathit{NI}}$, as a f…
Recent experiments on the Tokamak Fusion Test Reactor have afforded an opportunity to measure the retention of tritium in a graphite limiter that is subject to erosion, codeposition, and high neutron flux. The tritium was injected by both gas puff and neutral beams. The isotopic mix of hydrogenic recycling was measure…
Current‐voltage ( I‐V ) and anodic polarization characteristics were measured for the H 2 ‐fueled solid oxide fuel cell with an 8 mole percent yttria‐stabilized zirconia (YSZ) electrolyte and Ni‐YSZ anode. For a H 2 ‐rich H 2 ‐ H 2 O system, the I‐V curve was characterized by a high open‐circuit voltage and significan…
Systematic studies of the specific-heat anomaly and of the entropy changes at the Verwey transition in the ${\mathrm{Fe}}_{3\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ti}}_{\mathit{x}}$${\mathrm{O}}_{4}$ and ${\mathrm{Fe}}_{3\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Zn}}_{\mathit{y}}$${\mathrm{O}}_{4}$ series are…
Observations of the expanding vapor cloud generated by the hypervelocity impact have been carried out. Under usual laboratory conditions, rock or ice materials cannot be vaporized completely. In order to investigate the expansion of a large amount of the vapor by complete vaporization caused by hypervelocity impact, w…
We have used a high-intensity tunable picosecond infrared laser source to measure the spectral content of light scattered near the second harmonic for two well-known organic dyes, p-Nitroaniline and Disperse Red 1, at a number of wavelengths in the near infrared. We found that in Disperse red 1 a broad two-photon fluo…
Solid solutions along the magnesite-siderite join have been synthesized from mechanical mixtures of iron oxalate and basic magnesium carbonate using hydrothermal synthesis techniques at 500°C and about 2 kilobars. The double capsule method was used to provide the atmosphere necessary to prevent decomposition and oxida…
All articles of this category Improved procedures are described for the synthesis of meso -tetrakis(2,6-dichlorophenyl)porphyrin and for subsequent perhalogenation of the porphyrin ring. halogenated porphyrins - metalloporphyrins halogenation - oxidation catalysts
The frequencies of the Si-Si, Si-Ge, and Ge-Ge Raman modes in ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Ge}}_{\mathit{x}}$${\mathrm{C}}_{\mathit{y}}$ alloys with y\ensuremath{\leqslant}0.03 have been measured. All frequencies are found to increase as a function of t…
The exciton binding energy ɛb for a conducting polymer can only be defined unambiguously in the long chain limit. In that limit it can be taken as the difference between the bandgap or the ‘single particle bandgap’ — the former if the exciton dissociates into a free electron and hole, the latter if it dissociates into…
We analyzed the magnetic, transport, and magnetotransport properties of ${\mathrm{La}}_{0.67}$${\mathrm{Ca}}_{0.33}$${\mathrm{Mn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$${\mathrm{O}}_{\mathit{y}}$ as a function of aluminum concentration, temperature, and magnetic field and we found that when…
In situ Fourier transform infrared spectroscopic studies have been carried out on the nature of a metal complex‐immobilized polyaniline (PAn)/Prussian blue‐modified electrode and on the application of this electrode to the electroreduction of in an aqueous solution. On cathodic polarization, the ring structures of PAn…
The physical and electrical properties of xPb(Sc1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-zPbTiO3(PSMNT 100x/100y/100z) ternary ceramic materials near the morphotropic phase boundary (MPB) were investigated. The MPB follows on almost linear region between the PSMNT 58/00/42 and PSMNT 00/68/32 MPB compositions of the binary system…
The Brillouin light scattering technique has been used to study the elastic properties of a number of silicon dioxide films deposited by plasma-enhanced chemical vapor deposition on Si substrates. In addition to stoichiometric undoped glass films produced from either silane or tetraethylorthosilicate, we have also stu…
Paramagnetic centers in Nb-doped BaTiO3 ceramics are measured at 77–500 K by electron paramagnetic resonance (EPR) for investigating the role of the centers on the well-known positive temperature coefficient of resistivity (PTCR) effect (PTCR at the Curie temperature). EPR detects four signals; an anisotropically broa…