Materials Literature
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Antiferromagnetism in stacked nanographite is investigated with using the Hubbard-type model. The A-B stacking is favorable for the hexagonal nanographite with zigzag edges, in order that magnetism appears. Next, we find that the open shell electronic structures can be origins of the decreasing magnetic moment with th…
The paper presents discussion on up to date results on MgB2 conductors from the point of view of their future dc and ac applications. Basic physical parameters of MgB2 compound relevant to conductors are introduced. Different conductor preparation methods and conductor architectures are presented and attainable critic…
We report on a numerical study of quantum diffusion over $\ensuremath{\mu}\mathrm{m}$ lengths in defect-free multiwalled nanotubes. The intershell coupling allows the wave packet spreading over several shells, and when their periodicities along the nanotube axis are incommensurate, electronic propagation is shown to f…
We examine and identify magnetoresistance mechanisms in 2D system containing a sizable concentration of magnetic ions. We argue that some of these mechanisms can serve as a tool to measure spin polarization. Lack of spin degeneracy and enhanced localization make it possible to detect an additional QHE plateau associat…
Abstract The synthesis of boron‐modified polysilazanesof general type {B[C 2 H 4 Si(R)NR′] 3 } n [R = CH 3 , (NR′) 0.5 ; R′ = H, CH 3 ] by dehydrogenative coupling of tris(hydridosilylethyl)boranes B[C 2 H 4 Si(CH 3 ) n H 3− n ] 3 (C 2 H 4 = CHCH 3 , CH 2 CH 2 ; n = 0, 1) and ammonia or methylamine is reported. Deta…
Abstract The dynamic mechanical properties of hybrids of chlorinated polyethylene (CPE) and 3,9‐bis[1,1‐dimethyl‐2{β‐(3‐ tert ‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy}ethyl]‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) were investigated. The CPE/AO‐80 hybrids showed a novel relaxation in addition to the glass tran…
Abstract We have investigated the formation of high‐strength, high‐modulus fibers from four aliphatic polyketone resins. One resin was a perfectly alternating copolymer of ethylene and carbon monoxide, while the other three were terpolymers containing up to 6 mol % propylene. The mechanical properties were measured as…
Abstract Phase equilibria and phase reactions of precursor‐derived ceramics of the Si–C–N and the Si–B–C–N systems at temperatures higher than 1700 K are described. CALPHAD (CALculation of PHAse Diagrams) results confirm quantitatively the data from thermogravimetry and differential thermal analysis of precursor‐deriv…
Abstract Regenerated cellulose fibers from rice straws with a diameter of 10 to 25 μm and initial modulus of 11 to 13 GPa were prepared by wet spinning in rice straw/ N ‐methylmorpholine‐ N ‐oxide (MMNO) solution. X‐ray diffraction analysis indicates that the rice straw regenerated fibers are classified as cellulose (…
l -Lactide macromonomers with an incorporated double bond were successfully synthesized by controlled ring-opening polymerization initiated by two new cyclic tin alkoxides (1,1-di- n -butyl-stanna-2,7-dioxacyclo-4-heptene and 9,9,20,20-tetrabutyl-8,10,19,21-tetraoxa-9,20-distanna-dispiro[5.5.5.5]docosa-2,14-diene). In…
With the goal of developing diverse building blocks for nanocomposite materials, we have now learned to synthesize liquid crystalline materials by appending mesogenic groups to cubic silsesquioxane cores (LC cubes) via hydrosilylation of allyloxy functionalized mesogens ( 4, 5, 8, and 9 ) with octakis(dimethylsiloxy)o…
[reaction: see text] Dendrimers containing an encapsulated tertiary amine were prepared by coupling tris(2-aminoethyl)amine with dendritic branches derived from L-lysine. These dendrimers were used as catalysts in the Henry (nitroaldol) reaction between 4-nitrobenzaldehyde and nitroethane, and their catalytic performa…
Abstract Processing of two precursor‐derived SiCN ceramic monoliths was performed employing different liquid polymers, which were obtained by ammonolysis of functionalized chlorosilanes. Preparation of monolithic samples was performed by mixing liquid polysilazane with cross‐linked SiCN‐powder particles, derived from…
The optical and magneto-optical spectra of charge-ordered magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ below the Verwey transition and ${\mathrm{Mg}}^{2+}$- and ${\mathrm{Al}}^{3+}$-substituted ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ are investigated theoretically from first principles, using the fully relativistic Dir…
The intent of this paper is to cross-correlate the information obtained by space charge distribution analysis and electroluminescence (EL) detection in cross-linked polyethylene samples submitted to dc fields, with the objective to make a link between space charge phenomena and energy release as revealed by the detect…
Abstract Multinuclear ( 29 Si, 13 C, 11 B, 15 N, 1 H) solid‐state NMR and FT IR spectroscopy is employed to investigate the thermolysis of boron‐modified polyhydridovinylsilazane, [B(C 2 H 4 SiHNH) 3 ] n , from which a high‐temperature stable Si–B–C–N ceramic can be formed. The study is focused primarily on the chara…
Abstract Poly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); thei…
Abstract The preparation of silicon nitride‐ and carbide‐based ceramics by solid‐state thermolysis of polysilazanes and polysilylcarbodiimides is described. Results on the ceramization of the preceramic compounds and the architecture of the corresponding amorphous states obtained by spectroscopic means and by X‐ray an…
We use classical molecular dynamics simulations to study the dynamics of sodium atoms in amorphous ${\mathrm{Na}}_{2}\mathrm{O}\ensuremath{-}4{\mathrm{SiO}}_{2}.$ We find that the sodium trajectories form a well connected network of pockets and channels. Inside these channels the motion of the atoms is not cooperative…
Abstract The aim of this work was to study the pyrolytic conversion of a novel commercial polysilazane, poly(ureamethylvinyl)silazane (PUMVS; Ceraset™, Allied Signal Composites Inc., USA), into silicon‐based ceramics. The precursor was thermally cross‐linked and pyrolyzed between 200 and 1700 °C under argon or nitroge…