Materials Literature
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Electrochemical polymerization of aniline, on a Pt foil electrode coated with poly(methyl methacrylate) (PMMA), produces a homogeneous, free-standing, flexible, and conductive polymer film. The conductivity of the films depends on the aniline content and reaches 0.1–0.2 S/cm for films having aniline content of 15% or…
Rubber particle size is an important issue in toughening of engineering thermoplastics. Use of core-shell impact modifiers offers the advantage of a predetermined particle size; however, these particles must be appropriately dispersed in the matrix polymer to be effective for toughening. Recent work has shown that cor…
To improve the performance of rubber compounds using precipitated silica as a reinforcing filler, the silica surface was directly modified by (1) adsorption of a surfactant onto the surface, (2) adsolubilization of an organic monomer, (3) in situ polymerization of the monomer in the surfactant bilayer, and (4) partial…
Blends of chitosan with strongly crystalline polyamides (nylon-4 and nylon-6) and weakly crystalline polyamides (caprolactam/laurolactam and Zytel®) were investigated. Phase behavior, morphology, interactions with water, mechanical properties, and catalytic reactivity were studied. Films were made from formic acid sol…
The effect of hydrogen on the stacking-fault energy has been evaluated in a 310 austenitic stainless steel. The stacking-fault energy was calculated from measurements of the radius of curvature of dislocation nodes, which were imaged using weak-beam conditions. Preliminary results indicate that the presence of 40 torr…
We have investigated the effect of hydrostatic pressure on interdiffusion in multilayers composed of alternating layers of amorphous Si (2.7 nm) and Ge (3.1 nm). Samples were annealed at 420 °C at pressures between 0 and 2.8 GPa in an externally heated diamond anvil cell. Interdiffusion was measured by monitoring the…
The symmetry classification of three-dimensional periodic or aperiodic crystals is given a coordinate independent formulation which establishes the precise connection between Fourier-space and superspace crystallography. Superspace groups emerge without having to embed an aperiodic crystal in a higher-dimensional spac…
The crystallographic and magnetic structures of at 77 K have been refined by Rietveld analysis of the high-resolution neutron powder diffraction data. The analysis indicates that has -type structure ( ). The Cr atoms occupy 12j, 6g and 4f sites with occupancies 0.12, 0.10 and 0.50 respectively, but Cr atoms are absent…
High-quality homoepitaxial diamond films having large terrace width have been successfully grown on (001) diamond substrates. Schottky contact properties as well as the surface morphology and the film crystallinity of the deposited films were characterized in order to examine a potential for electronic applications. I…
The role of ion energy over the range 5 eV≤E≤20 keV in the production of the dense diamondlike sp3-bonded phase of carbon films deposited from ion beams has been investigated. Films with a significant sp3 component (≳40%), as determined by electron energy loss spectroscopy (EELS), can be formed over the wide energy re…
We report on studies using the x-ray surface forces apparatus (XSFA) to compare the structure of a liquid crystal confined between hard surfaces and, for the first time, between soft surfaces that can deform due to the stresses imposed by the confined fluid. We find that the alignment of smectic domains in confined fi…
Core and valence band photoemission data of hydrogen passivated Si(111):H surfaces yield surface Fermi level positions that are indicative of a near-surface depletion layer for n- as well as p-type samples. The bulk Fermi level positions are attained after annealing at ∼400 °C. These observations are explained in term…
Stable blue photoluminescence (PL) at 580 nm visible to the naked eye has been observed for the samples consisting of Ge nanocrystals (nc-Ge) embedded in a silicon oxide (SiO2) solid matrix, fabricated by atmospheric pressure chemical vapor deposition techniques. Raman spectroscopy measurement strongly suggests the ex…
c-axis oriented Bi4Ti3O12films have been prepared on Pt/Ti/Si(111) substrates by sol-gel process. Crack-free films of 0.5 μm thickness were fabricated using a multilayer spinning technique and calcination at 600 °C for 30 min. The average grain size of the film is about 0.15 μm. The film exhibits ferroelectric hystere…
Band-structure calculations, semiempirical as well as ab initio , have been applied to study the electronic band gap of the new exotic natural low-dimensional MX systems (where M = Pb or Sn and X = I, Br or Cl). Moreover, variational calculations are employed to calculate the excitonic binding energies, whose amplific…
We demonstrate electronic energy transfer between close packed quantum dots using cw and time resolved photoluminescence. Optically clear and thin, close packed quantum dot solids were prepared from mixtures of small and large CdSe quantum dots (38.5 and 62 \AA{}, $\ensuremath{\sigma}<4.5%$). Quenching of the lumin…
Overview. Historical Perspective and Current Status of Development. Atomization. Heat Transfer and Solidification of Droplets. Deposition. Spray Deposition Processing of Composites. Physical and Mechanical Properties of Spray--deposited Materials. Diagnosis and Characterization Techniques. References. Indexes.
Two hot areas in chemistry are dendrimers—highly branched polymers that are synthesized in stages from a core, in a manner resembling a snowflake—and self-assembly, the synthesis of molecules through molecular recognition. These ideas have been combined by Zimmerman et al. (p. 1095) in a report in this week's issue of…
Hydrogen bond-mediated self-assembly is a powerful strategy for generating large structures from smaller subunits. The synthesis of molecules containing two isophthalic acid units covalently attached to a rigid aromatic spacer is described. By normal pairing of carboxylic acids into hydrogen-bonded dimers, these molec…
The melting behavior of the alternating copolymer of ethylene and tetrafluoroethylene (ETFE) was investigated by differential scanning calorimetry (DSC). A complex melting pattern is observed, strongly influenced by the thermal history. Three melting processes can be identified, whose heats of fusion and peak temperat…