Research objectives and content
The aim of this work is to investigate the process of crystallization of solid solutions from aqueous solutions by direct in situ observations of different growth mechanisms as a function of supersaturation in a fluid cell of an Atomic Force Microscope. Subsequent surface chemical analysis will be by Time-of-flight Secondary Ion Mass Spectrometry. This work will lead to a better understanding of the factors which control the distribution coefficients of minor elements crystallizing from aqueous solution. The results will have direct relevance to problems as diverse as the way in which precipitation/dissolution of the (Ba,Sr)SO4 solid solution controls the Ba/Sr ratio in ocean water, to the way in which industrial pollutants such as Cd2+ adsorb onto calcite surfaces.
The project involves a number of innovative aspects: (i) thermodynamics of solid solution - aqueous solution systems and the calculation of the supersaturation of a given fluid with respect to each composition of the solid solution. (ii) experimental determination of the crystal growth mechanisms of end member phases and intermediate compositions as a function of supersaturation by direct observation at the unit-cell scale level. (iii) determination of the chemical composition of growth layers only one or two unit cells in thickness.
Training content (objective, benefit and expected impact)
The main training objective is to work in a research group which is active in applying modern techniques of Mineral Surface Science to interactions between mineral surfaces and aqueous fluids. The Institut of Mineralogy in Munster has an Atomic Force Microscopy laboratory and a TOF-SIMS, and is active in promoting the importance of mineral surfaces to many geochemical problems. My Ph.D. research on crystal growth gives me a background in aqueous geochemistry, but this needs to be integrated with a microscopic approach to the subject. Mineral Surface Science is a rapidly expanding field and there is no similar activity in Spain. The transfer of the expertise I would gain in Munster would be of considerable benefit in Spain. It would also strengthen the existing collaborative links between the Mineralogy Institutes in Madrid, Oviedo and Munster.
Links with industry / industrial relevance (22)