Materials Literature
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Abstract A study has been made to differentiate between the crosslinking reaction of bis-maleimides and bis-citraconimides in squalene as well as in natural rubber. Bis-maleimides are found to participate in the crosslinking reaction in the absence of curatives such as accelerators and sulfur. Bis-citraconimides take…
A study of recombination kinetics in LiB 3 O 5 (LBO) crystals by time-resolved luminescence and absorption spectroscopy is reported. An investigation of the kinetics of transient optical absorption (TOA) and luminescence under ns-scale electron-beam excitation performed within a broad temperature range of 77–500 K and…
Abstract The effect of shear level on the structure and resultant resistivity of CB‐containing high impact polystyrene/linear low density polyethylene (HIPS/LLDPE) extrudates produced by a capillary rheometer, as a function of blend composition and CB content, was studied. The data were compared with results obtained…
The tritium bred in a deuterium-tritium fusion reactor is removed from its blanket by using helium sweep gas mixed with some amount of hydrogen to promote the release rate. From the viewpoint of uptake capacity at the partial pressure of tritium and ease of tritium transfer to the main fuel cycle, a cryosorption bed,…
In order to examine the mechanisms by which seams age and fail under loads typical of those in use, factors and interactions among factors influencing the change in load required to extend an ISO-301 stitched seam (type ISO 1.01.01) during repeated lon gitudinal extension/recovery cycles at low loads are identified. F…
We propose a phenomenological approach for describing the dynamics of wetting front propagation in porous media. Unlike traditional models, the proposed approach is based on the dynamic nature of the relation between capillary pressure and medium saturation. We choose a modified phase-field model of solidification as…
Abstract Continuous extrusion was studied of self‐reinforced high density polyethylene (HDPE) sheets from flow‐induced crystallization at die pressures varying from 30 to 60 MPa. Their morphology, thermal behavior, tensile strength, and light transmittance were tested. Flow fields of a polymer melt through a convergin…
We present an introduction to Spindt cathode eld emission technology developed at SRI with a focus on possible space applications. The low power and light weight of Spindt cathodes makes them ideally suited to space applications requiring electron emission, while the robustness and eciency of the devices provides the…
Abstract The crystal structure of β -sodium acetate, NaC 2 H 3 O 2 , has been determined from X-ray powder diffraction data. Grid search and Rietveld refinement have been used to determine the structure. The crystal symmetry is orthorhombic (space group Pmn 2 1 , Z = 2) and the unit cell parameters are a = 3.4517(5) Å…
The equilibrium shape of a looped edge dislocation in a vertical smectic-$A$ film allows the determination of its line tension: in agreement with theoretical predictions, it is found to be proportional to its Burgers vector and to increase as $1/\sqrt{d}$ when the film thickness d decreases.
The SIRENS high heat flux facility at NCSU has been used to generate particulate representative of material mobilized during a hard disruption in a fusion reactor. The electrothermal (ET) plasma source in SIRENS has been found to be suitable for disruption simulation. Particulate generation occurs in both the fusion r…
The Flory-Huggins theory of flexible polymers mixtures [P. J. Flory, Principles of Polymer Chemistry (Cornell University Press, Ithaca, 1953)] and the Lebwohl-Lasher model of nematogens [G. Lasher, Phys. Rev. A 5, 1350 (1972); P. A. Lebwohl and G. Lasher, ibid. 6, 426 (1972)] are combined to understand the phase behav…
Novel poly(vinylsulfide)s were prepared by addition polymerization using 2,5-bis(2-thia-3-butenyl)-1,4-dithiane (TBD) with a radical initiator for an optical polymer having a high refractive index (nD) and Abbe number (v). Homopolymerization of TBD (72.9% conversion) and copolymerization with acrylonitrile or acrylate…
We have observed by polarizing microscopy a novel order transition inside the nematic phase and definitely below the clearing point of trans -4-hexylcyclohexane-1-carboxylic acid (C). The substance is known to exhibit the phase sequence Cr 32 C SmB 47 C N 96 C I (where Cr crystal, SmB smectic B, N nematic, I isotropic…
Abstract Banded urea can result in toxicity to corn ( Zea mays L.) germination and growth, due to accumulation of NH 3 and NO ‐ 2 s as a result of urea hydrolysis. Delaying urea hydrolysis through addition of acidic materials may reduce urea toxicity. Laboratory and field experiments were conducted to study phytotoxic…
An average unit cell for the Fibonacci chain has been constructed in physical space. The positions of atoms have been replaced by a statistical probability function of atomic displacements from the nearest point of the reference lattice. An analytical expression for diffraction peak intensities has been derived.
A model for simulating the voltage holding ratio in liquid crystal (LC) cells and investigating the influence of ionic impurities on device performance is proposed. Active matrix addressed liquid crystal displays (AM-LCDs) are composed of insulator materials between two electrodes, and are driven by pulse-voltage appl…
The hydrothermal reaction of (NH4)2B4O7, NaVO3, ethylenediamine, MnCl2·4H2O and H2O in the molar ratio 2.74:4:4:1:175 at 170°C for 5 days yields orange crystals of (H3NCH2CH2NH3)4[(VO)12O4[B8O17(OH)4)2 {Mn(H2O}2]·H2O(1·H2O) in 75% yield. The structure consists of a continuous contorted V12 ring, constructed from edge-…
X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) have been used to examine the near-surface region and outermost atomic layer of air-exposed, solvent-cleaned, LiGaO2(001) substrates, respectively, before and after room-temperature exposures to the flux produced by a novel electron stimulate…
A disordered dodecagonal quasicrystalline tantalum-rich telluride was prepared at the upper thermal stability limit of the related quasicrystalline phase by application of conventional high-temperature synthesis techniques. The structure of the disordered telluride was studied on a mesoscopic scale by means of high-re…