Topical Field II Reaction induced stress deformation
Project II.1: Chemically induced stress and deformation in mineral single grains
Int. Coop.: S. Zaefferer (MPI Düsseldorf)
Rationale: In single crystals any compositional heterogeneity induces mechanical stress, which in turn feeds into the free energy of the material. By this mechanism the thermodynamic stability of the material as well as its kinetic behavior during reaction may be influenced. We do cation exchange experiments in rock forming minerals to produce single crystals with chemically distinct domains (domain single crystals) to investigate their thermodynamic properties and kinetic behavior with particular focus on diffusion in self stressed systems.
Methods: cation exchange experiments and material characterization using EPMA, FEG-SEM-FIB, and EBSD; numerical modeling of coupled elastic deformation and diffusion
Project II.2: Hydration reactions and reaction induced deformation
M. Soerenssen (Uni Oslo)
Rationale: The behavior of solid phase aggregates with domains that undergo expansion (swelling systems) is of interest to many fields in scientific (melt extraction, hydration) and applied (recovery of oil, corrosion) research. We design simple systems comprised of calcite and periclase by hot isostatic pressing and then expose the aggregates to a hydrating atmosphere at elevated pressures and temperatures. This leads to formation of brucite from periclase and associated swelling by about 100%. We study the kinetics of the hydration reaction and the mechanical behavior of the hot pressed aggregate to learn about the modes of mechanical response as a function of the periclase to calcite ratio and reaction overstepping.
Methods: hot isostatic pressing and hydrothermal experiments (3 months stay @ GFZ Potsdam); in house material characterization - FEG-SEM-FIB, EBSD, EPMA; continuum mechanical modelling of fracturing (3 months stay @ Uni Oslo),
Project II.3: Irradiation damage induced by MeV heavy-ion irradiation
PI: L. Nasdala
Rationale: Stress in minerals as induced by irradiation damage involves two major phenomena. First, larger-scale stress occurs among growth zones: Zones withelevated U and/or Th concentrations may suffer elevated radiation damage, which results in enhanced volume expansion and eventually in the formation of fractures in adjacent zones. Second, nanometre-scale stress is induced by partial irradiation-induced amorphisation: The volume expansion of nm-sized, amorphous clusters causes dilative stress in the neighbouring crystalline remnants. These effects are planned to be studied in heavy-ion irradiation experiments on FIB lamellae of selected minerals. The main objective is to quantify irradiation effects, and to use the stress (affecting the short-range order around anionic molecular units) to estimate the degree of the self-irradiation damage in unknown geological samples.
Methods: Sample preparation in house using FEG-SEM-FIB; material characterization in house using EPMA, EBSD, PL, and Raman spectroscopy; mineral syntheses at the Memorial University of Newfoundland; Tandem accelerator irradiation at the Forschungszentrum Dresden-Rossendorf