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Theoretical aspects of solid state reactions in a mixed particulate ensemble and kinetics of lead zirconate formation

Description: A theoretical analysis was carried out to estimate the quasi-steady-state external mass transport by lattice, surface and gaseous diffusion in terms of the stereologically measurable microstructural parameters of a mixed powder compact. It was shown that the gaseous transport can be described by a single dimensionless quantity termed sublimation transport modulus. Using these equations, the relative importance of the alternate external transport modes can be evaluated. Experimental work determined the reaction isotherms for the formation of lead zirconate from yellow PbO and monoclinic zirconia between 710/sup 0/C to 810/sup 0/C for two zirconia size distributions. The larger zirconia showed diffusion controlled shrinking core kinetics up to about 90 percent reaction while the smaller zirconia indicated a diffusion controlled spherical growth of up to 85 percent reaction after an instantaneous nucleation at a limited number of sites. The difference was attributed to the differences in the mixing time and not to the particulate sizes. It was observed that for the same size range, a longer mixing operation gave a better dispersion of reactants which resulted in a higher nucleation site density required for a shrinking core type of product morphology and faster kinetics. A microprobe profile analysis of partially reacted particles confirmed that for the shorter mixing period, reaction resultedin a nucleation-growth-impingement type of morphology. The activation energy as calculated from the nucleation-growth model fit to the data was 138 Kcal/mole which is close to 131 Kcal/mole reported for Pb/sup 2 +/ diffusion in PbZrO/sub 3/. Approximate calculations show that the gaseous external mass flux of PbO was negligible compared to the lattice or surface diffusive flux.
Date: September 1, 1979
Creator: Chandratreya, S.S.
Partner: UNT Libraries Government Documents Department

Proton spectra from 800 MeV protons on selected nuclei. Progress report, January 1, 1979-December 31, 1979

Description: The emission of protons from targets of /sup 6/Li, Li, /sup 12/C, /sup 27/Al, /sup 40/Ca, /sup 51/V, /sup 90/Zr, and Pb under bombardment from 800 MeV protons was studied using the high resolution proton spectrometer at the Los Alamos Meson Physics Facility. Laboratory scattering angles of 5, 7, 9, 11, 13, 15, 20, 25, and 30/sup 0/ were measured, with special emphasis on the quasi-free region. Outgoing momenta corresponding to the region of pion production were examined at 11 and 15/sup 0/. Absolute cross sections derived by reference to known (p,p) scattering data at 800 MeV. The quasi-free scattering has been fit with a DWIA analysis by summing over the unobserved (struck) nucleon. The systematics of proton production and the applicability of the DWIA analyses are discussed. 26 references.
Date: September 1, 1979
Creator: Stearns, R.L.
Partner: UNT Libraries Government Documents Department

Multielement geochemical exploration data for the Cove Fort-Sulphurdale Known Geothermal Resource Area, Beaver and Millard counties, Utah

Description: Multielement geochemical exploration data have been acquired for the Cove Fort-Sulphurdale Known Geothermal Resource Area (KGRA). This was accomplished by analysis of both whole rock and +3.3 specific gravity concentrate samples from cuttings composites collected from shallow rotary drill holes. Areal distributions are reported for arsenic, mercury, lead and zinc. These are elements indicated by previous studies to be broadly zoned around thermal centers in geothermal systems and thus to be useful for selecting and prioritizing drilling targets. Results from this work suggest that reservoir temperature and/or reservoir to surface permeability, and thus possibly overall potential for a geothermal resource, increase northward beneath the approximately 18 square mile area containing shallow drill holes, possibly to beyond the northern limits of the area. The data provide a basis for development of three principal target models for the geothermal system but do not permit prioritization of these models. It is recommended that geochemical, geological, and temperature gradient surveys be expanded northward from the present survey area to more fully define the area which appears to have the best resource potential and to aid prioritization of the target models.
Date: September 1, 1979
Creator: Bamford, R.W. & Christensen, O.D.
Partner: UNT Libraries Government Documents Department

Contamination of groundwater by heavy metals from the land disposal of fly ash. Final report

Description: Information is provided on laboratory and field research to assess the aquatic effects and extent of release, migration, and attenuation of trace metals from fly ash into subsurface soil environments for a typical disposal regime. Those metals analyzed were arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc. Laboratory studies indicated that the major effects of fly ash in water were pH alterations, which could be either acidic or basic, and comparatively high proportions of trace metals released from the ash surface, controlled largely by pH. Field studies confirmed the continued importance of pH in defining the attenuation of the metals by the soil but also suggested that pSO/sub 4/, ionic strength, and soil chemical parameters, such as iron and manganese content, could not be ignored. Theoretical thermodynamic analysis in concert with field data indicated that both adsorption onto soil phases and precipitation of metal phases occurred, the dominant attenuation mechanism depending upon the specific metal and soil conditions.
Date: September 1, 1979
Creator: Theis, T.L.
Partner: UNT Libraries Government Documents Department

Composition and octane number of US motor gasolines sampled in the DuPont 1978-1979 winter road octane survey

Description: Samples of US Motor Gasoline obtained from service stations in early December, 1978, were composited by region based on company sales. These composited samples were analyzed for hydrocarbon composition, sulfur, manganese, other specifications (distillation, RVP, gum, gravity) and Research and Motor Octane Number.
Date: September 1, 1979
Creator: Johnson, W.L.
Partner: UNT Libraries Government Documents Department