Materials Literature
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Direct carrier multiplication (DCM) occurs when a highly excited electron-hole pair decays by transferring its excess energy to the electrons rather than to the lattice, possibly exciting additional electron-hole pairs. Atomistic electronic structure calculations have shown that DCM can be induced by electron-hole Cou…
The KF/hydrotalcite (HT) solid base catalysts were prepared by impregnation and characterized by X-ray diffraction. Biodiesel can be obtained from transesterification of palm oil with methanol over the KF/HT catalysts. The effect factors, such as KF/HT load ratio, methanol/oil molar ratio, catalyst amount, reaction ti…
Different equations have been proposed for estimating the glass transition temperature of amorphous mixtures. All such expressions lack a term to account for the effect of the entropy of mixing on the glass transition. An entropy based analysis for the glass transition of amorphous mixtures is presented. The treatment…
Disk-like surfactant bicelles provide a unique meso-structured reaction environment for templating the wet-chemical reduction of platinum(II) salt by ascorbic acid to produce platinum nanowheels. The Pt wheels are 496 +/-55 nm in diameter and possess thickened centers and radial dendritic nanosheets (about 2-nm in thi…
Sorption of pyrene by regular and nanoscaled aluminum, zinc, and titanium oxides was examined. All oxides had low sorption for pyrene because of sorbed water molecules. Due to the larger surface area (SA) of nanoparticles, they had higher sorption for pyrene than the regular ones. Organic matter (OM) coating greatly e…
Abstract The effect of magnesium carbonate (MgCO 3 ) loading on the compound properties of polychloroprene (CR), natural rubber (NR), and their blends was investigated. The studied properties included Mooney viscosity, cure characteristics, and degree of filler–filler interaction. In addition to MgCO 3 loading, the ef…
Particle-tracking methods are used to study gelation in a colloidal suspension of Laponite clay particles. We track the motion of small fluorescent polystyrene spheres added to the suspension, and obtain the micron-scale viscous and elastic moduli of the material from their mean-squared displacement. The fluorescent s…
Totally tubular: A new tubular germanate is cotemplated by 2-methylpiperazine and an (H2O)16 cluster in a hydro(solvo)thermal synthesis. The germanate features a large, highly symmetric 68126 cavity (see picture; yellow sphere) built from 12 Ge7X19 (X=O, OH, F) clusters (GeX6 red, GeX5 yellow, GeX4 green).
ZrC particles are introduced into carbon fiber reinforced ceramic matrix composites to improve their high‐temperature performances. Composites without interphases have higher densities than those with interphases and most ZrC particles remain in the fiber interbundle areas. All composites show typical noncatastrophic…
Abstract A series of efficient catalysts, based on zinc alkoxides coordinated with NNO‐tridentate Schiff‐base ligands (L 1 H‐L 6 H), for ring opening polymerization of L ‐lactide have been prepared. The reactions of diethyl zinc (ZnEt 2 ) with L 1 H‐L 6 H yielded [(μ‐L)ZnEt] 2 ( 1a–6a ), respectively. Further reaction…
We use nanohole relaxation to study the surface relaxation of films of glassy isotactic poly (methyl methacrylate) (i-PMMA) films. These measurements allow us to obtain the time dependent relaxation function at a number of different sample temperatures for the first 2-3 nm of the free surface in a system often used as…
Abstract This research examines the effect of a microsize/nanosize talc filler on the physicochemical and mechanical properties of filled polypropylene (108MF10 and 33MBTU from Saudi Basic Industries Corp. and HE125MO grade from Borealis) composite matrices. A range of mechanical properties were measured [tensile prop…
A theory of field-induced crystal nucleation is developed and verified experimentally for the case of switching in nanoglasses of phase change memory. For symmetry-breaking strong electric fields, it predicts needle-shaped crystallites with nucleation barriers lower than that of spherical nuclei and a strong field dep…
Abstract In order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)‐reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcani…
Colloidal carbon spheres have been prepared from aqueous α-, β-, and γ-cyclodextrin (CD) solutions in closed systems under hydrothermal conditions at 160 °C. Both liquid and solid-state 13 C NMR spectra taken for samples at different reaction times have been used to monitor the dehydration and carbonization pathways.…
A method to treat the surface of Nb is described which potentially can improve the performance of superconducting RF cavities. We present tunneling and x-ray photoemission spectroscopy (XPS) measurements at the surface of cavity-grade niobium samples coated with a 3 nm alumina overlayer deposited by Atomic Layer Depos…
Transmission probability of a domain wall through a magnetic nanowire is investigated as a function of the external magnetic field. Very intriguing phenomenon is found that the transmission probability shows a significant drop after exceeding the threshold driving field, which contradicts our intuition that a domain w…
Density functional theory based calculations of the energetics of adsorption and diffusion of CO on Pt islets and on the Ru(0001) substrate show that CO has the lowest adsorption energy at the center of the islet, and its bonding increases as it moves to the edge of the island and further onto the substrate. Activatio…
We study the ultrafast dynamics of surface electromagnetic waves photogenerated on aluminum film perforated with subwavelength holes array by means of transient photomodulation with 100 fs time resolution. We observed a pronounced blueshift of the resonant transmission band that reveals the important role of plasma at…
We demonstrate that the discrete character of the vibrational spectrum of a small crystal accounts for size dependence of its thermodynamic properties and melting temperature. Using a self-consistent statistical method [Phys. Rev.B 66, 054302 (2002)] we derive the Gibbs free energy of free nanocrystalline plates and c…