Materials Literature
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Lead-based single crystal relaxor ferroelectrics have been developed with fundamental properties that in theory should dramatically enhance the bandwidth and sensitivity-bandwidth product for ultrasound transducers. High sensitivity array elements with fractional bandwidths of over 120% have been modeled using the pro…
We use a nondestructive technique of fluorescence confocal polarizing microscopy to visualize three-dimensional director patterns of defects in Grandjean-Cano wedges filled with a cholesteric liquid crystal of pitch p=5 microm. Strong surface anchoring of the director causes a stable lattice of dislocations in the bul…
We present an ultra-low temperature study (down to T = 20 mK) of the nuclear spin-lattice relaxation (SLR) in the 55Mn nuclei of the molecular magnet Mn12-ac. The nuclear spins act as local probes for the electronic spin fluctuations, due to thermal excitations and to tunnelling events. In the quantum regime (below T…
This work presents new experimental results on low-temperature (LT) characterization of local rf properties of passive superconducting (SC) microwave devices using a novel Laser Scanning Microscope (LSM). In this technique, a modulated laser beam is focused onto and scanned over the surface of a resonant SC device to…
We report a systematic study of xenon gas diffusion NMR in simple model porous media: random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding…
We have extended the utility of NMR as a technique to probe porous media structure over length scales of ~ 100 - 2000 micron by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We…
The segmental relaxations of poly(4-vinylphenol)/poly(vinyl ethyl ether) [PVPh/PVEE] blends, with PVPh content from 10 to 50 wt % and having a very large T g difference between the components, have been investigated using broadband dielectric spectroscopy. Although a single T g was observed for all compositions in DSC…
Terpyridine capped gold nanoparticles (ca. 2.0 nm diameter) form large aggregates in the presence of metal ions [Fe(II), Zn(II), Cu(I), Ag(I)]. The assembly process is a result of metal coordination between two terpyridines that are attached to separate nanoparticles. The stability of the aggregates in various solvent…
We have designed and synthesized new, novel photochromic copolymers composed of photochromic 2-indolyl fulgides or fulgimides and methyl methacrylate. The spectroscopic and photochromic properties of these copolymers have been determined and compared to their liquid solution analogues. The utilization and advantages o…
The effect of chemical surface treatment on the sensitivity, specificity, and stability of mesoporous Si thin film vapor sensors is studied. The vapor sensors operate by measurement of Fabry−Pérot interference from the porous Si layer, probed using a diode laser operating at a wavelength of 687 nm. Four chemically dis…
Exfoliated PS/Na−MMT nanocomposites were obtained up to 3 wt % of clay without modifying clay organically and DBS−Na affected the degree of exfoliation of silicate layers. The feed rate of monomers also had an effect on polymerization, and it was a key to controlling the total monomer concentration and maintaining a c…
Polyamidoamine (PAMAM) dendrimers are used as carriers to deliver complexed Fe(III) ions uniformly onto silicon oxide substrates for the formation of iron oxide nanoparticles with a narrow diameter in the range of 1−2 nm. Chemical vapor deposition (CVD) synthesis with these nanoparticles affords single-walled carbon n…
Recent studies on the Portevin - Le Chatelier effect report an intriguing crossover phenomenon from a low dimensional chaotic to an infinite dimensional scale invariant power law regime in experiments on CuAl single crystals and AlMg polycrystals, as a function of strain rate. We devise a fully dynamical model which r…
Polyelectrolyte brushes were formed at the interface between hydrophobized mica and water by adsorbing amphiphilic diblock copolymers consisting of a hydrophobic and a charged block. We measured force−distance profiles with the surface force apparatus (SFA) for several polyelectrolyte brushes of different lengths as a…
We report initial NMR studies of i) xenon gas diffusion in model heterogeneous porous media, and ii) continuous flow laser-polarized xenon gas. Both areas utilize the Pulsed Gradient Spin Echo techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion c…
We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients.…
We report a new method for the purification of HiPCO single-wall carbon nanotubes (SWNT), which consists of the following sequence: (a) organic functionalization of the as-produced nanotubes (pristine tubes, p-SWNT), (b) purification of the soluble functionalized nanotubes (f-SWNT), (c) removal of the functional group…
Gold nanorods have been synthesized by photochemically reducing gold ions within a micellar solution. The aspect ratio of the rods can be controlled with the addition of silver ions. This process reported here is highly promising for producing uniform nanorods, and more importantly it will be useful in resolving the g…
This paper introduces the curing curve analysis, the polymerizing reaction kinetic parameter calculation, and the determination of the relationship between the curing degree and the curing temperature and curing time. For the materials used as the ground insulation of the generator winding, measurements have been made…
The dynamic mechanical properties of epoxy/mica glass-fiber reinforced composites were studied at different aging stages under electrical-thermal stresses and thermal-mechanical stresses. A new method was proposed to calculate the apparent activation energy of glass transition (AAEGT) of epoxy/mica based on dynamic me…