Materials Literature
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A highly soluble, conjugated Zn-porphyrin polymer was synthesized and found to strongly interact with the surface of single-walled carbon nanotubes, producing a soluble polymer-nanotube complex. Successful complexation required the addition of trifluoroacetic acid to the solvent (THF). It was found that the complex re…
Abstract The present contribution reports the fabrication and characterization of ultrafine polyacrylonitrile (PAN) fibers by electrospinning and further development of the as‐spun PAN fibers into ultrafine carbon fibers. The effects of solution conditions (i.e., solution concentration, viscosity, conductivity, and su…
The Y_0.5Ca_0.5BaCo_4O_7 compound exhibits four magnetic anomalies at the temperatures 387, 281, 52, and 14 K; all anomalies show characteristics typical for spin freezing into disordered states: frequency dependent transition temperature in the AC magnetic susceptibility together with relaxation of thermoremnant magn…
In this work we studied, by means of high-resolution neutron diffraction as a function of temperature, the La1.4Sr0.8Ca0.8Mn2O7 bilayered manganite for two different annealing treatments. Out data allowed us to shown, for the first time, the absence of long-range magnetic order in this optimally doped bilayered mangan…
We theoretically study localization of quasi-two-dimensional negatively charged excitons X^- on isolated charged donors in magnetic fields. We consider donors located in a barrier at various distances L from the heteroboundary as well as donors in the quantum well. We establish how many different singlet X_s^- and tri…
We have developed a linear scaling algorithm for calculating maximally-localized Wannier functions (MLWFs) using atomic orbital basis. An O(N) ground state calculation is carried out to get the density matrix (DM). Through a projection of the DM onto atomic orbitals and a subsequent O(N) orthogonalization, we obtain i…
Point defect species and concentrations in metastable Fe-C alloys are determined using density functional theory and a constrained free-energy functional. Carbon interstitials dominate unless iron vacancies are in significant excess, whereas excess carbon causes greatly enhances vacancy concentration. Our predictions…
It is demonstrated, by numerical simulations of a 2D assembly of polydisperse disks, that there exists a range (plateau) of coarse graining scales for which the stress tensor field in a granular solid is nearly resolution independent, thereby enabling an `objective' definition of this field. Expectedly, it is not the…
We use highly accurate density functional calculations to study the band structure and Fermi surfaces of . We calculate the real part of the noninteracting susceptibility, , which is the relevant quantity for a charge density wave (CDW) instability and the imaginary part, , which directly shows Fermi surface (FS) nest…
We report surface-bound growth of single-wall carbon nanotubes (SWNTs) at temperatures as low as 350 degrees C by catalytic chemical vapor deposition from undiluted C2H2. NH3 or H2 exposure critically facilitates the nanostructuring and activation of sub-nanometer Fe and Al/Fe/Al multilayer catalyst films prior to gro…
Optical microscope images of graphite oxide (GO) reveal the occurrence of fault lines resulting from the oxidative processes. The fault lines and cracks of GO are also responsible for their much smaller size compared with the starting graphite materials. We propose an unzipping mechanism to explain the formation of cr…
The present study demonstrates a surface structure that mimics the water harvesting wing surface of the Namib Desert beetle. Hydrophilic patterns on superhydrophobic surfaces were created with water/2-propanol solutions of a polyelectrolyte to produce surfaces with extreme hydrophobic contrast. Selective deposition of…
In this work, we present the influence of rare-earth element additions on this new composite material. A great improvement of the electromagnetic properties was obtained. The constituent chemicals were mixed in the stoichiometric composition, calcined at 850degC for 2 h and blended with PVA to press into steroidal or…
The texture of high Si and Al electrical steel produced by hot dipping and diffusion annealing can be significantly modified by the thermomechanical processing. The diffusion of Si and Al from the coating affects the final texture depending on the Si content of the substrate. In low Si substrates a phase transformatio…
Two concentration ranges of activating hydrofluoric acid additions were distinguished when dissolving zinc in a 2.5 M CrO 3 solution. Zinc dissolves slowly in a range of 0.05 to 0.3 and quickly from 0.4 to 1 mol/l HF. The effect is explained by the involvement of F - ions in the formation of Cr(III) fluoride complexes…
An important part of the investigation into the loss of the Space Shuttle Columbia was numerical modeling of the foam impact event. Because of this work, as well as the failure during flight of available tools to provide helpful information, the Columbia Accident Investigation Board recommended the development of phys…
QSSPC (quasi-steady-state photo-conductance) is a well-known technique for lifetime measurement, but up to now its use has been limited to silicon. In this paper we describe a simple method to extend this technique to germanium samples. The significant differences between silicon and germanium are separately analyzed.…
In this paper, CdSe (nanotubes, nanorods) and ZnSe (nanorods, nanoslats) were simultaneously synthesized through a biomineralization process through biomembrane bitemplates of mungbean sprouts at room temperature. The XRD patterns indicated that these nanocrystals were crystallized in the hexagonal structure and cubic…
Photochemical deposition of silver nanoparticles in poly(butyl acrylate) and poly(butadiene-styrene) under the action of monochromatic UV light (254 nm) was studied. Changes in the polymer structure in the course of photolysis were revealed and analyzed. A mechanism of formation of silver nanoparticles was suggested.…
Sensitometric and holographic properties of photoresist layers made from carbazolylalkyl methacrylate copolymers and polyepoxypropylcarbazole sensitized with triiodomethane and, additionally, spiropyran photochromic compounds were studied. It was found that the introduction of photochromic 6′-bromo-8′-nitro-1,3,3-trim…