Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
Large monolithic xerogel silica glasses were successfully made from tetramethyl-orthosilicate and distilled water using the combination of an acidic drying control chemical additive (DCCA) and a specially designed drying chamber. The acidic DCCA increases the gel strength by formation of a fibrillar ultrastructure, an…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA new polymorph of tetraphosphorus triselenide, .alpha.'-P4Se3: an x-ray, Raman, and XPS study of the normal crystalline phases and a DSC study of the crystalline and the orientationally disordered phases of P4Se3Joanne R. Rollo, Gary R. Burns, Ward T. Robinson, Robin J. H.…
The reactions of a sintered α‐SiC with 5% H 2 /H 2 O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O 2 ) > 10 −22 atm) leads to a SiO 2 formatio…
Abstract A rheo‐optical apparatus, based on a linear shear rheometer, has been constructed to study the deformation of liquid–crystalline polymers. This apparatus uses optical techniques such as flow birefringence, small‐angle light scattering, and optical microscopic image analysis. The rheological responses were sim…
Abstract IR and polarized Raman Spectra of Na 4 P 2 O 7 · 10H 2 O were recorded and analysed. From the spectra it is inferred that the P 2 O ion has C 2ν symmetry in the crystal. The δPOP band is found to belong to the A 2 species. Multiple bands observed for the stretching and bending modes of water are probably du…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe reaction of 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphinatoiron(III) hydrate with alkyl and acyl hydroperoxides. The dynamics of reaction of water-soluble and non .mu.-oxo dimer forming iron(III) porphyrins in aqueous solution. 7Kazuhisa Murata, Rick Panicu…
Second order non-linear optical (NLO) effects, such as second harmonic generation, occur only in materials that are acentric. Finding ways to assure that a bulk material is acentric has been a serious hurdle in the design of new organic materials for non-linear optical uses.1 A trivial, albeit useful, solution to the…
The synthesis of colloidal boehmite (AlOOH) is studied by heating basic aluminum chloride solutions under constant stirring. The temperature and Al 2 O 3 : Cl molar ratio influence the product morphology. Synthesis at 140°C generates highly fibrous polycrystalline particles that are on average 360 nm long, 30 nm broad…
The Daresbury station 8.3 powder diffractometer has been used to determine the lattice parameter of tungsten powder to about 3–6 p.p.m. with respect to the National Institute of Standards and Technology SRM640B silicon de facto standard. The measurement and analysis algorithms that have been developed indicate that th…
It is shown that, in the transitional region between the B and C kinetic regimes for grain-boundary diffusion, the product of the grain-boundary width δ, the segregation factor K and the grain-boundary diffusion coefficient D b= KδD b), as well as the grain-boundary diffusion coefficient itself, can be estimated. From…
X-ray studies on a material whose constituent molecules have a weak transverse dipole moment provide clear evidence of a first-order smectic-A--smectic-C transition. In addition, results on materials belonging to the same homologous series of compounds show that this transition can be driven from second order to first…
Previous data for the pressure dependence of the order parameter for ${\mathrm{BaTiO}}_{3}$ at room temperature (RT) as well as new data for the pressure dependence of the order parameter for ${\mathrm{PbTiO}}_{3}$ at RT have been analyzed within the framework of a phenomenological theory for ferroelectrics. It is con…
A dual purpose pyrometer is described that allows both accurate radiance temperature measurement and fast temporal response. The system uses two silicon photodiodes with separate optical paths derived from a common spot on the sample. The optical bandwidths and response times of each detection circuit are tailored to…
We present a field-theoretic treatment of polymer solution dynamics. The method involves the construction of a Martin–Siggia–Rose generating functional for flexible polymer chains dissolved in a low molecular weight solvent. This formalism is shown to be particularly convenient for investigating the dynamics of collec…
Abstract The three series of polyether polyurethane cationomers based on MDI, HDI, and TDI that are the subject of Part I, undergo emulsification (or phase inversion) on addition of water to solutions in MEK. The phase inversion mechanism depends on the structure of hard segment, ionic content, and dispersion temperat…
Absorption saturation and luminescence measurements on semiconductor-doped glasses are reported, and the results are analyzed in terms of a band-filling model that is found to explain adequately the absorption data obtained with fresh as well as with photodarkened samples. With this model the free-carrier densities ar…
The interaction of hydrogen and deuterium with the (OOO1) surface of beryllium has been investigated using resolution electron energy loss spectroscopy, thermal desorption spectroscopy, and work function measurements. Dissociative adsorption of molecular hydrogen is an activated process, and recombinative desorption o…
The aging behaviour of quenched Zn–Al alloys containing small additions of copper was studied using metallography, hardness measurements, and quantitative X-ray diffraction. The kinetics of decomposition of supersaturated α/α′ and β phases were determined and related to structural changes. It was found that the Avrami…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNeutron reflectivity study of block copolymers adsorbed from solutionS. K. Satija, C. F. Majkrzak, Thomas P. Russell, S. K. Sinha, E. B. Sirota, and G. J. HughesCite this: Macromolecules 1990, 23, 16, 3860–3864Publication Date (Print):August 1, 1990Publication History Publis…
Defect creation in 24% densified, high-OH-concentration amorphous ${\mathrm{SiO}}_{2}$ has been studied using 248-nm excimer laser radiation. Combining laser and \ensuremath{\gamma}-ray radiation data, we find correlated growth of oxygen-vacancy and nonbridging oxygen-hole-center defects over a range of concentration…