Materials Literature
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Grain boundaries are known to reduce significantly the electrical dc conductivity of polycrystalline metallic materials. In this paper, we give a quantum mechanical calculation of the grain-boundary resistance based on the transfer-matrix approach. The results show an exponential decrease of the conductivity with resp…
The observation of very-low-frequency bands by Raman scattering in a nucleated cordierite glass is described. The frequency of the maximum of scattering is proportional to the inverse diameter of the particles, which are spherical spinel microcrystallites. It is shown that vibrational surface modes of particles are re…
Abstract A series of [BaxCsy][(Ti, Al)3+2x + yTi4+8-2x-y]O16 hollandites, synthesized at 1250°C and coexisting with ‘reduced ’ rutile, demonstrates complete solid solution between barium and caesium endmembers, and simultaneously between Ti3+ and Al3+. The presence or absence of rutile has only a minor effect on stoic…
Abstract Phosphorous, as sodium dihydrogen phosphate, and nitrogen, in the form of a urea–for‐maldehyde condensate, were applied to cotton fabric. The flame‐retarding character of each treated fabric was assessed by determining the respective limiting oxygen index. Analysis of the results showed that at the lowest lev…
Abstract Radiation induced graft copolymerization of ethyl acrylate onto sisal fibers was investigated. It was fond that the percent added‐on of ethyl acrylate to sisal fibers was prohibitively low when using the direct grafting method due to excessive hompolymerization. The preirradiation method was found to be inval…
Abstract Two hydroxy‐functionalized liquid rubbers, one a commercially available polybutadiene (PB) and the other a specially synthesized polymyrcene (PM), have been converted into homopolyurethane elastomers by reaction with 4,&4prime;‐diphenylmethane diisocyanate (MDI). Additionally, PB and PM, each in admixture…
We have measured Young's modulus $Y$ and internal friction $\ensuremath{\delta}$ of the charge-density-wave (CDW) conductors Ta${\mathrm{S}}_{3}$ and Nb${\mathrm{Se}}_{3}$, in the presence of combined ac and dc electric fields. In the pinned CDW state, the elastic properties are sensitive to even small ac-field amplit…
Poly(2-ethyl-2-oxazoline) is prepared by the ring-opening polymerization of 2-ethyl-2-oxazoline with a cationic initiator. Many of the polymer's characteristics stem from its molecular structure, which has a backbone of alternating two carbon atoms and one nitrogen with a pendent propionyl group off the nitrogen. Rheo…
We report experimental studies of the statics and dynamics of diffusion-limited polymerization. The fractals obtained were produced electrochemically from neutral precursors, and have a Hausdorff dimension of 1.74\ifmmode\pm\else\textpm\fi{}0.03. The width of the active growth zone increases at the same rate as the fr…
Abstract Dipole relaxation dielectric loss behavior of a fiberglass–epoxy composite has been studied as a function of moisture uptake. A single widely distributed loss peak, centered at −16°C for 10 kHz measurement, is observed in the dry composite. Very low moisture concentrations (<0.1%) interact with the composi…
We suggest that dendritic sidebranches may, under some circumstances, be generated by selective amplification of noisy fluctuations near the tip. Our proposal is based on numerical and analytic studies of the dynamics of the two-dimensional boundary-layer model with kinetic crystalline anisotropy. Certain features of…
Abstract not Available.
We obtained the first σ∗-values and Es -values for siloxy groups by spectroscopic and kinetic methods. Detailed mechanistic investigations are performed on the hydrolysis of chlorosiloxanes, the cleavage of Si[sbnd]O[sbnd]Si bonds by HCl, and the substituent exchange reaction between silanols and chlorosilanes.
Thin film induced stresses on silicon substrate were measured at room temperature, using a stress gauge wafer deflection setup. The thermal oxide was in high compressive stress due to CTE mismatch between oxide and Si substrate. As deposited PSG was in tensile stress decreasing in stress level with increasing P conten…
Abstract High temperature curing is feasible with adequate curative modifications. NR-containing compounds are prime considerations. Cure time reductions of about 35% or more are entirely within reason. Use of the modified compounds at conventional or low curing temperatures makes possible significant improvements in…
An account is given of the determination of the thermophysiological properties of two blankets, one made from wool and the other from an acrylic-fibre–cotton blend but otherwise matched in weight and fibre diameter, by laboratory measurements as well as by climatic-chamber tests with human subjects. The tests show tha…
Abstract A recent study by the authors of the effects of pH and organic acids on residual orthophosphate solubility in an acidic, montmorillonitic soil (Typic Chromoxererts) was extended to include variations of ionic strength (NaCl background) and Ca 2+ concentration at fixed ionic strength. The objective of the expe…
Potential‐controlled electrochemical methods were used to characterize the pitting behavior of 6061 alloy aluminum in synthetic ocean water. Irreproducible breakdown potentials (Ebd) and reproducible repassivation potentials (Erp) were determined from cyclic anodic polarization (CAP). Reproducible breakdown and repass…
The analysis of the STS‐7 flight experiments of the system yielded positive results which surpass the original objectives of these experiments. The mass transport rates of observed in microgravity environment are in close agreement with theoretically predicted values for diffusion limited mass transport. This supports…
Rates of cell volume increase in individuals of five genera of centric marine diatoms were measured using time-lapse video microscopy. In continuous light, size increased continuously in Thalassiosira weissflogii and Lauderia borealis, while steps were observed during the growth of Stephanopyxis turris, Biddulphia aur…