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Evaluation of anelastic evidence for interstitial solute binding in bcc metals

Description: A Direct Spectrum Analysis (DSA) technique has been applied to key internal friction and elastic after-effect data which are involved in the controversy over the existance of interstitial clustering in the refractory metals. It is found that at relatively high interstitial solute concentrations some of the Snoek peak broadening is due to relaxations that are distinct from the main relaxation. This finding supports the view that interstitial solutes have an interaction that produces clusters of interstitials.
Date: January 1, 1985
Creator: Cost, J.R. & Stanley, J.T.
Partner: UNT Libraries Government Documents Department

Cascade diffusion theory of displacement-induced point defect concentration and flux fluctuations

Description: A theoretical approach, which has been developed to assess the fluctuations in point defect concentrations and fluxes to sinks that are induced by the production of point defects in spatially and temporally discrete cascades, is summarized. Solutions for cascade dissipation are outlined for the case where cascades occur in a homogeneous lossy medium as well as for the more involved geometries where cascades occur in the presence of a nearby dislocation or cavity. By superposition of solutions representing discrete cascades under conditions of interest, time profiles of point defect concentrations and fluxes are generated. The profiles exhibit extreme fluctuations. Continuum rate theory results arise by applying limits and approximations to cascade diffusion theory. Application of the theory to microstructural processes shows that property changes, especially creep are affected by the fluctuations.
Date: January 1, 1986
Creator: Mansur, L.K.; Brailsford, A.D. & Coghlan, W.A.
Partner: UNT Libraries Government Documents Department

Effect of microstructure on the arsenic profile in implanted silicon

Description: According to an irradiation damage model, the profile of an implanted ion at temperature great enough for diffusion to occur will depend on the sink density in the material. To test this model, pure silicon wafers were prepared with high and low dislocation densities. These wafers were implanted with about 5 x 10/sup 19/ As/sup +2//m/sup 2/ at 77/sup 0/K, 300/sup 0/C, and 600/sup 0/C. After implanting the profiles were measured using Rutherford backscattering spectroscopy and secondary ion mass spectroscopy. The observed spreading of the As-profile contradicts initial theoretical predictions. Further speculation is presented to explain the differences.
Date: October 1, 1985
Creator: Coghlan, W.A.; Rhee, M.H.; Williams, J.M.; Streit, L.A. & Williams, P.
Partner: UNT Libraries Government Documents Department