Materials Literature
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We estimate the rate at which randomly stacked hard-sphere crystals transform into the thermodynamically stable face-centered cubic phase. As an input for this estimate we need both the free-energy difference between bulk face-centered cubic (fcc) and hexagonal close packed (hcp) phases, and the hcp–fcc interfacial fr…
Hierarchical ordering of mesoporous silica induced by fluoride addition is described for aqueous acid-syntheses. The authors report that small amounts of fluoride make it possible to control the organization of the mesoporous materials on different length scales. At low pH, fluoride addition brings about the formation…
Programmed with an unusual number of functions, the tetraethynylethene derivative 1 exhibits three addressable switching subunits, which can undergo individual reversible switching cycles that are controllable by pH and light. Three "write/erase" processes and one "AND" logic gate process can be separately addressed,…
Summary 1. Diatoms were sampled in the spring of 1994 and the autumn of 1995 at 137 pristine or near‐pristine reference sites on large and small streams at various altitudes in eastern New South Wales and Victoria. Scrapings were taken from five firm substrata across a range of microhabitat conditions at each site on…
Self-assembly of predesigned angular and linear dipyridylporphyrin modules with bisphosphine-coordinated Pd(II) and Pt(II) angular and linear modules leads to cyclic porphyrin arrays containing two or four units and ranging in size from 15 to 39 Å. Multinuclear NMR spectra indicate high symmetry for these macrocycles.…
A new and simple chemical route has been used to synthesize mixed‐oxide powders. The method uses long‐chain polymers, such as poly(vinyl alcohol) and poly(ethylene glycol). The chemistry of the precursor solution differs from other solution‐polymerization techniques. The stabilization of the cations in the precursor i…
The effect of near-by-electrode charge injection on switching of a thin film ferroelectric capacitor is theoretically analyzed. We develop a model of switching affected by charge injection through a surface dielectric layer to calculate the coercive field of the capacitor as a function of both film thickness and maxim…
A novel hexagonal columnar liquid crystalline superlattice is coassembled from backbone(s) coated with a three-cylindrical bundle supramolecular dendrimer self-assembled from polymers containing twin dendritic benzamide side groups and their low molar mass side groups which self-assemble into supramolecular cylinders.
It is argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C–H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative ch…
We have made a high-resolution quasielastic incoherent neutron scattering (QENS) study of the translational dynamics of supercooled water contained in micropores of Vycor glass at different hydration levels. QENS spectra from the confined ${\mathrm{H}}_{2}\mathrm{O}$ are analyzed in terms of the \ensuremath{\alpha}-re…
1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene ( 1a ) was found to undergo photochromism in a single crystalline phase. Upon irradiation with ultraviolet light the colorless crystal turned red with keeping the crystal shape. The red color is due to the closed-ring form 1b . The red color was bleached by irradiat…
The electric field dependence of the piezoelectric properties of rhombohedral 0.955Pb(Zn1/3Nb2/3)O3–0.045PbTiO3 crystals were investigated as a function of orientation with respect to the prototypic (cubic) axes. For 〈111〉 oriented fields, depolarization and subsequent domain reorientation resulted in an apparent maxi…
Alumina molecular sieves with continuously adjustable pore sizes are achieved by use of cationic surfactant-assisted synthesis, a technique which is reported for the first time. The “hydrolysis-retarding” role played by triethanolamine allows control of the competition between aluminum hydrolysis/condensation reaction…
Preparation by morphosynthesis–the chemical construction and patterning of inorganic materials with complex forms–will only be technologically relevant if inexpensive routes with high product yields can be developed. A facile, one-step, high-yield preparation of vaterite (calcium carbonate) microsponges is presented,…
Communication: The efficiency of electroluminescent devices is strongly affected by charge carrier mobilities, in that electrons and holes must be able to be quickly transported for high quantum efficiency. Hole mobility data are reported here for a new family of five conjugated copolymers consisting of triarylamines—…
In this paper, the research on the vanadium dioxide thin film, which can be used as intelligent windows, is reviewed, including the basic properties of V2, energy band structure, model of electronic energy and the origin of metal-to-insulator transition (MIT). Finally, the problems existing in the research and the pos…