Materials Literature
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Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH(3))(2)NH(2)]K(4)[V(10)O(10)(H(2)O)(2)(OH)(4)(PO(4))(7)].4H(2)O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadi…
Abstract Starch‐ g ‐poly(methyl acrylate) (S‐ g ‐PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted P…
Abstract The effect of diethylene glycol (DEG) on the crystallization of poly(ethylene terephthalate) (PET) was studied under isothermal and dynamic conditions. The strain‐induced crystallization of PET and its relationship to DEG content was also studied. The samples were isothermally and dynamically crystallized in…
Abstract Sisal fibers (Agave‐Veracruz) have been used as reinforcements in low‐density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during ble…
The angular dependences of the free energy, thickness and stresses are calculated for the antiphase boundaries (APBS) parallel to the tetragonal z axis but otherwise arbitrarily oriented. The general results are applied to Hg 2 Br 2 and KSCN. The APB in the former case is shown to decay into two ferroelastic domain wa…
Abstract The crystal growth behaviour of the important organic nonlinear optical material 2-(a-methylbenzylamino)-5-nitropyridine (MBANP) (space group P21) has been investigated and techniques have been developed for the preparation of large (up to 7 cm x 4 cm x 3 cm) high-quality single crystals suitable for detailed…
The influence of grain boundary scattering of lattice waves in high quality diamond films has been determined by the measurement of thermal conductivity down to 0.15 K. We find that the mean free path for lattice vibrations (phonons) exceeds substantially the crystallite size and approaches the physical size of the sa…
The cross-luminescence (CRL) resulting from radiative electronic transitions from the mainly anion-related valence band to the uppermost cation core band has been studied in a number of complex halides containing CsCl, RbF, KF, and BaF 2 . The energy of the CRL photons is determined by the energy difference of the two…
We report novel biphotonic holographic storage of text and gratings on unoriented films of a side-chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye molecules. We believe tha…
Polyethylene propylene films of various molecular weights, which would normally wet native-oxide-covered Si surfaces, were observed to dewet the surface when the film thickness became less than the polymer radius of gyration. These films could be made to wet either by increasing the annealing temperature or by chemica…
Polycrystalline thin films of Ba0.5Sr0.5TiO3 were deposited by excimer laser (248 nm) ablation. Films deposited near 575 °C exhibited good crystallinity, a dielectric constant of 330, a dissipation factor of 0.02, a leakage current density of 2×10−7 A/cm2, a charge storage density of 36 fC/μm2, and breakdown time of 3…
FTIR spectra reported by Brandt et al. [Solid State Commun. 81, 307 (1992)], Tischler et al. [Appl. Phys. Lett. 60, 639 (1992)], and Tsai et al. [Appl. Phys. Lett. 59, 2814 (1991), and 60, 1700 (1992)] have shown the presence of Si-H and Si-H2 lines in porous Si which Canham [Appl. Phys. Lett. 57, 1046 (1990)], Tischl…
A boiling water treatment of light emitting porous silicon can give rise to a large blue shift of its photoluminescence spectrum and meanwhile strengthen the skeleton of porous Si by filling up many pores with aqueous oxide. A stable blue-green light emission at the peak wavelength down to 500 nm is achieved. FTIR mea…
Theory predicts that an electron or hole added to a conjugated polymer chain causes the chain to distort, forming a large polaron. Recent calculations of the three-dimensional band structure of trans-polyacetylene, t-PA, and poly(phenylene vinylene), PPV, have obtained values for the interchain coupling that are large…
We report results from an experimental study of coarsening in thin layers of succinonitrile in the presence of impurities. We quench the latter from the liquid phase to different temperatures within the liquid-solid coexistence region thus controling the solid area fraction \ensuremath{\varphi}. As \ensuremath{\varphi…
This study presents optical transmission measurements performed on free-standing homogeneous porous silicon (PS) films of different porosities and substrate doping levels. The absorption coefficient curves deduced from these measurements, taking into account the total quantity of matter in the PS film, exhibit signifi…
The dynamics of simultaneous ordering and phase separation in the presence of a long-range Coulomb interaction is investigated by a computer simulation. It is shown that an intermediate nonstoichiometric ordered single phase appears as a transient phase during decomposition of a binary homogeneous disordered solid sol…
Reciprocating shear is found to increase the isotropic-to-lamellar transition temperature in a symmetric diblock copolymer melt. The temperature at which the isotropic state becomes unstable rapidly approaches the ordering transition as the shear rate increases. Shear-induced ordering results in lamellae orientation w…
Brightness traces of the solidification of highly undercooled Ta and Re droplets processed in an ultrahigh vacuum drop tube give evidence of two successive phase transformations. First-principles calculations of the structural stability of these metals are developed in order to appreciate the possibilities of obtainin…
A simple dynamical criterion for crystallization of a colloidal fluid which undergoes Brownian motion is proposed, similar in spirit to the classic Lindemann melting rule. It states that the ratio of the long-time and short-time self-diffusion coefficients is a universal number very close to 0.1 along the freezing lin…