Materials Literature
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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…
Anomalous x-ray diffraction studies show that the charge ordering in $α^\prime$-NaV$_2$O$_5$ is of zig-zag type in all vanadium ladders. We have found that there are two models of the stacking of layers along \emph{c-}direction, each of them consisting of 2 degenerated patterns, and that the experimental data is well…
The article is focused on low temperature intermetallic A15 superconducting wires development for Nuclear Magnetic Resonance, NMR, and Nuclear Magnetic Imaging, MRI, magnets and also on cryogen-free magnets. There are many other applications which would benefit from new development such as future Large Hadron Collider…
The new class of Mg-B superconducting conductors was prepared using the standard in-situ powder-in-tube, PIT, method where Mg+2B mixture was used to fill the copper and silver tubes. Study of the intergranular current, grain connectivity and superconducting phases in wires were conducted by AC susceptibility measureme…
We measured the low temperature specific heat of a sputtered $(Fe_{23Å}/Cr_{12Å})_{33}$ magnetic multilayer, as well as separate $1000Å$ thick Fe and Cr films. Magnetoresistance and magnetization measurements on the multilayer demonstrated antiparallel coupling between the Fe layers. Using microcalorimeters made in ou…
The recent discovery of coexisting ferromagnetism and superconductivity in ZrZn2, and the fact that they are simultaneously suppressed on applying pressure suggest the possibility of a pairing mechanism which is mediated by exchange interactions and connected with the proximity to a magnetic quantum critical point. On…
A new class of matching conditions between the atomistic and continuum regions is presented for the multiscale modeling of crystals. They ensure the accurate passage of large scale information between the atomistic and continuum regions and at the same time minimize the reflection of phonons at the interface. These ma…
The mechanisms of charge injection, transport and trapping in low-density, high-density and cross-linked polyethylene (LDPE, HDPE and XLPE) are investigated in this paper through charging-discharging current measurements and space-charge observations. The conductivity of LDPE is much larger than that of XLPE and HDPE.…
Low concentrations of hydrogen peroxide induced random degradation of partially deacetylated chitin and chitosan. Average molecular weight decreased in accordance with first-order kinetics. The degradation rate was much faster than that of the ultrasonic degradation, and it was comparable to that of the enzymatic hydr…
Abstract Poly(lactic acid) (PLA) is a biodegradable polymer, but its applications are limited by its high cost. Blending granular starch with PLA reduces the cost, but the blend has poor strength properties. In this study, a 55/45 (w/w) mixture of PLA (weight‐average molecular weight = 120,000 Da) and dried wheat star…
An atmospheric pressure non-equilibrium plasma (APNEP) developed in the UK by EA Technology Ltd is currently being investigated in collaboration with the University of Surrey. Of the many applications of surface modification that can be induced using plasmas, adhesion enhancement is one of the most commercially import…