The dissolution mechanism and kinetics of a number of strontium master alloys in liquid aluminum and A356 alloys have been investigated. The dissolution behaviour of the strontium alloys was found to show marked differences depending on strontium content. Dilute strontium alloys containing less than 63 weight percent Sr were observed to exhibit simple dissolution in both melts. The dissolution rate and the recoveries of these alloys were found to increase with increasing melt temperature. Over the temperature interval of 675-775$ sp circ$C dissolution was determined to be mass-transfer controlled with associated activation energies of 10-20 kcal/mole. Experimental rate constants for dissolution showed good agreement with a mass transfer correlation expressed as k = (0.67(Gr.Sc)$ sp{1/4}$ + 0.58(h/r)) (D/h). The dissolution of high strontium master alloys $(>$63 wt. pct. Sr), unlike the dilute alloys, was accompanied by the formation of various intermetallics. Additions at low melt temperatures yielded the exothermic formation of those intermetallics that have the lowest Sr content as seen in the relevant phase diagram, i.e., SrAl$ sb4$ in liquid Al and SrAl$ sb2$Si$ sb2$ in liquid A356. Due to low reaction rates at these low melt temperatures, these intermetallics formed as dispersed particles that could easily dissolve in the melt yielding high recoveries. At high melt temperatures, the associated chemical reactions yielded, as products, the higher Sr intermetallics which formed with little or no exothermicity. These intermetallics were observed to be scarcely soluble in the melt resulting in low strontium recoveries. The dissolution times of these alloys were found to show good agreement with calculated values based on a two-stage dissolution model comprising an initial exothermic reaction period and a subsequent free dissolution period. The strontium master alloys were classified in two groups; the high Sr alloys that are efficient at low temperatures of 675-7

Isotope shifts of twenty-two isotopes of strontium, $ sp{78}$Sr to $ sp{100}$Sr excluding $ sp{99}$Sr, and three isomers of strontium, $ sp{83 rm m,85m,87m}$Sr, have been measured using laser spectroscopy. The nuclear spins, magnetic and quadrupole moments, have been extracted from the data for all odd isotopes. The changes in mean square charge radii have also been evaluated for all isotopes and isomers. / The changes in mean square charge radii, which are compared to the predictions of the droplet model and Hartree-Fock plus B.C.S. calculations, show a pronounced shell effect at the closed neutron shell at N = 50 and a sharp increase at N = 60. The theoretical analysis suggests that the change in mean square charge radii for N = 60, 62 is due to the onset of a large static deformation. For the remaining isotopes, the changes are attributed to a change in size, a change in the predominantly dynamic deformation, and a change in the diffuseness of the nuclear charge distribution.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 38-43).

Thesis (Ph. D.)--Harvard University, 1987. / Includes bibliographical references.

This thesis describes a simple method for the separation of strontium from an excess of barium using ion exchange techniques. This process has been applied to the separation of strontium and rubidium in barites. The resin used is Dowex-50 (200-400 mesh, hydrogen form) and the column dimensions are 1.1 by 8 cm. The column is eluted at room temperature with 1.5 M hydrochloric acid at a flow rate of approximately 1 ml/ min. Strontium and rubidium from two samples of barites were analysed using a solid-source mass spectrometer to determine strontium-87/strontium-86 ratios. The above chemical techniques have also been employed in the separation of strontium and rubidium from galenas. The concentration of strontium in one sample of galena (U.B.C. No. 1) has been determined using isotope dilution techniques. The results show an absence of strontium in the galena sample studied. Finally the common strontium ratios of two barite samples are compared with common lead ratios of associated galenas (Slawson and Austin, 1962) and a possible correlation between these ratios has been observed. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

I performed first principles studies of the site occupancy and magnetic properties of zinc-tin-substituted strontium hexaferrite by using density functional theory. In this study, I determined the site preference of zinc and tin atoms when they are restricted to occupy the same sublattice in strontium-hexaferrite. I found that Zn and Sn atoms prefer to replace Fe ions at 2a sublattice under this restriction and caused the saturation magnetization to decrease.

No description available.

No description available.

The various concepts of the fission process, mass and charge distribution, and fine structure in fission yields are reviewed. Details and results of mass spectrometric analyses of fission-product samples of cesium, rubidium, and strontium are reported. Absolute yield values have been assigned to the mass 87, 135, and 137 chains. Relative yields of the mass 88 and 90 chains have been determined. A mechanism is postulated to account tor anomalies in fission fine structure. The Glendenin mechanism of instantaneous neutron emission is found to require modification. / Thesis / Master of Science (MS)

No description available.