Materials Literature
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MAxTe2 (M=Ta, Nb and A=Si, Ge) compounds show a great variety of commensurately and incommensurately modulated structures depending on the value for x. It is shown that the theory of superspace groups can be used to standardize the structures and to predict the 3D symmetry of the commensurately modulated structures. T…
Abstract The physicochemical changes of silk fibers irradiated with γ‐rays was studied in relation to the amount of absorbed does in the range 0–21 Mrad. The yellowing index ( b/L ) suddenly increased at low dose for both raw and degummed silk fibers. An equilibrium value was attained from 10 Mrad upward. The tensile…
Abstract Low‐density polyethylene (LDPE) has been investigated with respect to the diffusion of hindered phenol antioxidants added to the polymer matrix. In the study, a simple method was used to measure the diffusion coeficient, with the aid of FTIR spectroscopy without any extraction or refining steps in the analysi…
Scanning tunneling microscopy (STM) has been used to investigate the interaction of nanoscale structural elements associated with rutile ${\mathrm{TiO}}_{2}$(100)-(1\ifmmode\times\else\texttimes\fi{}3). These are the 1\ifmmode\times\else\texttimes\fi{}3 reconstruction, vicinal off-cut steps in the [001] direction, and…
Diamond homoepitaxial films were grown on an off-angle (001) substrate with a misorientation of 4.3° toward the [110] direction by microwave plasma-assisted chemical vapor deposition from a methane-hydrogen gas mixture. The single domain 2×1 surface was observed by low-energy electron diffraction (LEED) and scanning t…
Temperature-dependent conductivity and Hall measurements have been carried out on heavily in situ B-doped polycrystalline diamond films in a temperature range from ∼100 to 750 K. The slope of the conductivity is clearly non-Arrhenius leading to a pronounced tail at low temperatures. Carrier transport at low temperatur…
A full phase field model of eutectic growth is proposed, which incorporates the generic features of a eutectic phase diagram and reduces to the sharp-interface model in the appropriate limit. Large scale two-dimensional simulations are presented for the isothermal solidification of a uniformly undercooled eutectic mel…
We have measured the magnetoresistance (MR) and Hall coefficient of state-of-the-art graphite nanotubule bundles. The apparent Hall coefficient is positive in the temperature and field ranges studied. At low temperatures, the conductivity \ensuremath{\sigma} shows two dimensional weak localization behavior and the MR…
Using the Car-Parrinello method, we have obtained unforeseen structures for the low-lying isomers of ${\mathrm{Si}}_{45}$ and other midsized Si clusters. They are formed by two shells of atoms, the outer one (cage) being fullerenelike and inner one (core) consisting of a few atoms saturating dangling bonds. These nove…
We have measured the optical transmission of quasiperiodic dielectric multilayer stacks of ${\mathrm{SiO}}_{2}$ (A) and ${\mathrm{TiO}}_{2}$ (b) thin films which are ordered according to a Fibonacci sequence ${\mathit{S}}_{\mathit{j}+1}$={${\mathit{S}}_{\mathit{j}\mathrm{\ensuremath{-}}1}$}, with ${\mathit{S}}_{0}$={B…
Abstract Short branch (methyl branch) effects on the creep properties of the ultra‐high strength polyethylene fibers were investigated. The temperature and the stress dependence of creep rates of several high‐strength polyethylene fibers having different branch contents, which were prepared by blending of two polymers…
Abstract The complexation of ultrahigh‐molecular‐weight poly(ethylene oxide) (PEO) with urea in both the solid and molten states was studied by infrared spectroscopy. Information about the temperature dependences of the absorption bands in the 3600–2600 and 1300–600 cm −1 region on heating and cooling was obtained. So…
Abstract Several 2,5‐bisaryloxyterephthalic acids were prepared by a new method, namely arylation of diethyl‐2,5‐bistrimethylsiloxyterephthalate. Rigid‐rod polyaramides were prepared by polycondensation of silylated diamines with a terephthaloylchloride with two diphenylsulfone side chains. Another polyamide was prepa…
Abstract Novel methyl‐substituted aromatic poly (ether sulfone)s and poly (ether ketone)s were synthesized from combinations of 3,3′,5,5′‐tetramethylbipheny‐4,4′‐diol and 2,2′,3,3′,5,5′‐hexamethylbiphenyl‐4,4′‐diol, and 4,4′‐dichlorodiphenyl sulfone and 4,4′‐difluorobenzo‐phenone by nucleophilic aromatic substitution…
Abstract Elastomeric molecular networks have been prepared by endlinking polydimethyl siloxane molecules having functional chain ends, both in the presence of an unreactive polymeric diluent and in the undiluted state. Values of tensile (Young) modulus were found to be in good agreement with the simple molecular theor…
Abstract Effects of solvent and electrolyte on the electrochromic behavior and degradation of polyaniline in nonaqueous aprotic media, as well as its electrochemical redox and degradation mechanisms, were investigated with chemically prepared polyaniline‐poly (vinyl alcohol) composite films and polyaniline homogeneous…
Abstract In a previous article, 1 we reported on the interaction of cellulose with NH 3 /NH 4 SCN by using solid state CP / MAS 13 C‐NMR, wide‐angle X‐ray and other techniques. It appears that during an imposed temperature cycling sequence, specific cellulosic inter‐ and intramolecular hydrogen bonds are broken as pol…
Abstract Ammonia/ammonium thiocyanate (NH 3 /NH 4 SCN) is an excellent swelling agent and solvent for cellulose, even at a high degree of polymerization. Because polymorphic conversion in cellulose has been a long‐standing, perplexing, troublesome problem, we have undertaken to study that mechanism. Solid state CP/MAS…
Abstract An improved technique for casting highly oriented films of block copolymers from solutions subjected to flow is presented. Polymer solutions were rolled between two counter‐rotating adjacent cylinders while at the same time the solvent was allowed to evaporate. As the solvent evaporated, the block copolymers…
Abstract Bilayer film Fourier transform infrared (FTIR) model experiments are designed to provide a well‐defined interface for study which can be probed by infrared spectroscopy during the interdiffusion and reaction of two reactive polymers. This provides a model experiment to determine the kinetics and extent of rea…