Materials Literature
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Single particle dynamics of water confined in a nanopore is studied through computer molecular dynamics. The pore is modeled to represent the average properties of a pore of Vycor glass. Dynamics is analyzed at different hydration levels and upon supercooling. At all hydration levels and all temperatures investigated…
We have developed a technique to accelerate the acquisition of effectively uncorrelated configurations for off-lattice models of dense polymer melts that makes use of both parallel tempering and large-scale Monte Carlo moves. The method is based upon simulating a set of systems in parallel, each of which has a slightl…
A series of Ce x Ti 1 - x O 2 mixed oxide materials was synthesized by a sol−gel method with x varying from 0.1 to 0.9 and characterized by XRD, Raman, and TPR techniques. The structure of the mixed oxides changes with the Ce/Ti ratio. When the x value is decreased from 1.0 to 0.6 for Ce x Ti 1 - x O 2, only a cubic p…
We discuss our new implementation of the Real-space Electronic Structure method for studying the atomic and electronic structure of infinite periodic as well as finite systems, based on density functional theory. This improved version which we call HARES (for High-performance-fortran Adaptive grid Real-space Electroni…
The NQR on Ba nuclei was studied in four samples of BaBiO3 prepared in different ways and, in addition, in BaPbO3. The spectrum of $^{137}$Ba at T=4.2 K consists of relatively broad line centered near 18 MHz for all BaBiO3 samples and near 13 MHz for BaPbO3. The integrated intensity of $^{137}$Ba resonance in ceramic…
Femtosecond fluorescence upconversion has been utilized to study the band edge and deep trap emission dynamics of cadmium selenide (CdSe) nanocrystals (NC's) ranging in size from 27 to 72 Å in diameter. Both the band edge rise time and decay show a direct correlation to NC size, and a rise time that depends on excitat…
Electron energy-loss spectroscopy (EELS) is widely used to identify elemental compositions of materials studied by microscopy. We demonstrate that the sensitivity and spatial resolution of EELS can be extended to the single-atom limit. A chemical map for gadolinium (Gd) clearly reveals the distribution of Gd atoms ins…
Volatile organic compounds (VOCs) comprise 67% of total hazardous air pollutants (HAPs) that are emitted by major industrial point sources into the U.S. atmosphere (1). Adsorption by activated carbon fiber (ACF) has been recognized as one of the feasible regenerative control processes to separate and recover VOCs for…
Generalizing the mode-coupling theory for ideal liquid-glass transitions, equations of motion are derived for the correlation functions describing the glassy dynamics of a diatomic probe molecule immersed in a simple glass-forming system. The molecule is described in the interaction-site representation and the equatio…
Vanadosilicate V-SBA-1, which incorporated more than 4 wt % vanadium (Si/V < 20) in cubic mesoporous molecular sieves, was directly synthesized under strongly acidic conditions and characterized by various techniques. Powder X-ray diffraction (XRD) showed that the resultant samples had a well-ordered cubic SBA-1 struc…
Thermal stressing of a JP-8 fuel was carried out in an isothermal flow reactor using nickel, stainless steel (316 and 304), Silcosteel, and glass-lined stainless steel tubes at 500 °C wall temperature and 34 atm (500 psig) for 5 h at a liquid fuel flow rate of 1 mL/min. Different length segments along the sample tubes…
Montmorillonite/polyimide (3,3‘,4,4‘-benzophenone tetracarboxylic dianhydride - 4,4‘-oxydianiline, BTDA-ODA) nanocomposites displaying different morphological, thermal, and mechanical characteristics were synthesized by involving mono-, di-, and trifunctional group swelling-agent-modified montmorillonite and poly(amic…
Ferromagnetism and accompanying large negative magnetoresistance in Pb-substituted Bi-Sr-Co-O misfit-layer compound are investigated in detail. Recent structural analysis of (Bi,Pb)${}_2$Sr${}_{3}$Co${}_2$O${}_9$, which has been believed to be a Co analogue of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+δ}$, revealed that it ha…
The structure and density of Mo species in Mo/H−ZSM5 during catalytic CH 4 reactions was investigated using in-situ X-ray absorption spectroscopy (XAS), temperature-programmed oxidation after reaction, and the isotopic exchange of D 2 with OH groups in H−ZSM5 before and after CH 4 reactions. These methods reveal that…
Poly( l -lysine)- g -poly(ethylene glycol) (PLL- g -PEG) is a member of a family of polycationic PEG-grafted copolymers that have been shown to chemisorb on anionic surfaces, including various metal oxide surfaces, providing a high degree of resistance to protein adsorption. PLL- g -PEG-modified surfaces are attractiv…
We have defined ferroic phase transitions as nondisruptive phase transitions involving a change of point-group symmetry. For transitions defined in this way a prototype symmetry can always be assigned or chosen. Ferroelectric phase transitions are a subset of ferroic transitions such that the ferroic phase belongs to…
Single-crystal variable temperature EPR, optical and polycrystalline magnetic susceptibility studies have been made on a novel six-coordinate Ag(II) complex. Temperature dependent EPR studies on pure single crystals of this compound reveal that dynamic Jahn-Teller distortion operates above 230 K, between 230 K and 120…
Three-dimensional Monte Carlo simulations of flexible and semiflexible polymer brushes at various grafting densities are carried out to study their equilibrium structure and attendant properties by using the bond fluctuation model. Our simulation results of long flexible polymer brushes are, in general, consistent wit…
Bis(alkylcyclopentadienyl)arenes have been prepared by sequential lithiation/alkylation of dibromoarenes with alkylcyclopenta-2-en-1-ones. The resulting dicarbinols were dehydrated with p -toluenesulfonic acid to give the bis(alkylcyclopentadienyl)arene. Poly(alkyl-1,1‘-ferrocenylenearylene)s were prepared by the reac…
Two experimental techniques, forward recoil spectrometry (FRES) and size exclusion chromatography with fluorescence detection (SEC/fluorescence), have been used to monitor independently the extent of reaction between model end-functional polymers at a PS/PMMA interface. Bilayer samples comprising a polystyrene layer c…