Materials Literature
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Nanopowders of Bi2Ti2O7 with various La modifications were fabricated by chemical coprecipitation. As sintered at high temperature, the phase structure in powders translates into (La0.22Bi0.78)4Ti3O12 and (La0.26Bi0.74)2Ti4O11 with increasing La concentration, respectively. Dielectric and nonlinear resistivity investi…
Rapid thermal annealing of sputter-deposited chalcogenide glasses is demonstrated to yield superior quality films which are used to fabricate low loss (<0.3 dB/cm) photoinduced channel waveguides in chalcogenide glasses. This process also enhances the photosensitivity and the magnitude of photoinduced index cha…
We have studied fragmentation and ionization of ${\mathrm{C}}_{60}$ by ${\mathrm{He}}^{+}$ impact over a velocity range from 0.1 to 1 a.u. where a transition from vibrational to electronic excitation is predicted. With increasing velocity we observe a strong decrease of evaporative processes ( ${\mathrm{C}}_{60\ensure…
Electronic properties of a doped zigzag nanotube are investigated by a self-consistent tight-binding method. We propose that a doped nanotube with donor atoms on one side and acceptors on the other can function as a nano diode. It is shown that a potential step in the tube, created by two different types of doping in…
A novel type of P=Se⋅⋅⋅I−P bridging is found in the solid-state structures of iodophosphane selenides. These molecules can be viewed as new building blocks for the design of directed donor–acceptor interactions (see diagram) within chains, helices and “soft–soft” base pairs.
Elongated honeycombs of interknitted molecular ribbons comprising cyanuric acid and triaminopyrimidine are assembled through a programmed combination of hydrogen-bond triplexes and ion-pairing interactions.
A defect generation mechanism, namely, the grain-boundary Frenkel pair model, and corresponding diffusion mechanisms during electromigration are developed using atomic simulation techniques in Al and Al–Cu. We contend that large numbers of interstitials and vacancies exist at grain boundaries and both contribute to ma…
We present an analysis of the effect of interface stress on strain in bulk in an open system with a large interface-to-volume ratio, at equilibrium with the solute at a controlled chemical potential. The results are relations for interface stress and for solute concentration in the bulk as a function of measurable par…
Several 1(4)- and 2(3)-tetraalkoxy-substituted phthalocyanines (shown) were synthesized from the corresponding (R,S)-, (R)-, and (S)- alkoxy-substituted phthalonitriles, and the four structural isomers formed for each phthalocyanines were separated by HPLC. The influence of (R,S)-, (R)-, and (S)-substituents on the is…
The binding affinities of [18]crown-6 and La3+, Nd3+, Gd3+, and Yb3+ have been reproduced in MeOH with Monte Carlo free-energy perturbation calculations which used newly derived Lennard-Lones parameters for the Ln3+ ions. The figure shows the complex of a lanthanide ion and the crown ether.
We have measured specific heat, magnetization, and electrical transport properties of ${\mathrm{La}}_{0.875}{\mathrm{Sr}}_{0.125}\ensuremath{-}{\mathrm{MnO}}_{3}$ single crystals in magnetic fields up to 14 T. In addition to a ferromagnetic transition two structural phase transitions are observed with one of the latte…
The multicomponent self-assembly of ditopic linear ligands, circular ligands and copper(I) or silver(I) ions leads to the exclusive formation of a series of cylindrical inorganic architectures containing an internal cavity whose height may be modulated by the nature of the ligands used (see picture: 1: 20 Å; 2: 33 Å).…
Cellular materials (dense emulsions, foams, and vesicles) made out of two different phases, one being dispersed in the other, may coarsen in time through coalescence or rupturing events of the thin liquid domains that separate adjacent cells. In this Letter we study the destruction through coalescence of a model cellu…
The surface conditions favoring a negative electron affinity (NEA) on hexagonal boron nitride (h-BN) grown by radio-frequency plasma-assisted chemical vapor deposition (CVD) have been investigated by ultraviolet photoelectron spectroscopy. The NEA condition on the h-BN film appears to be resistant to oxygen-plasma or…
A liquid crystal with an azobenzene moiety as a photoactive mesogenic unit is investigated in photoinduced birefringence. Measurements reveal that it possesses large magnitude of photoinduced birefringence (Δn∼10−2) and the characteristic of long-term optical storage. The resulting polarization information can be eras…
Interwoven networks have been isolated from the self-assembly of the flexible long-chain sebaconitrile (1,10-decanedinitrile) and different silver(I) salts. These networks include an eightfold interpenetrated diamondoid frame (I), a fourfold interwoven 3D four-connected frame topologically related to the prototypical…
A novel ferromagnetic transition, accompanied by carrier density collapse, is found in doped charge-transfer insulators with strong electron-phonon coupling. The transition is driven by an exchange interaction of polaronic carriers with localized spins; the strength of the interaction determines whether the transition…
Depending on the size, the photoluminescence (PL) of silicon quantum dots present in porous silicon can be tuned from the near infrared to the ultraviolet when the surface is passivated with Si-H bonds. After exposure to oxygen, the PL shifts to the red by as much as 1 eV. This shift and the changes in PL intensity an…
Crystallization of polypropylene (PP) in unvulcanized blends of PP with the butadiene–styrene block copolymer (SBS) was studied through differential scanning calorimetry (DSC) and X-ray diffraction measurements in the composition range of 0–40 wt % SBS content. Analysis of the crystallization exotherms revealed variat…
According to Ehrenfest classification, the glass transition is a second-order phase transition. Controversy, however, remains due to the discrepancy between experiment and the Ehrenfest relations and thereby their prediction of unity of the Prigogine-Defay ratio in particular. In this article, we consider the case of…