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The objective of this study is to evaluate the radiation induced microstructural and mechanical differences influenced by alloying elements including phosphorus, chromium, and nitrogen and crystal orientation in iron-based binary alloys. Fe-4.5at%P, Fe-9.5at%Cr, and Fe-2.3at%N binary model alloys were irradiated with 4.4 MeV Fe++ ions at 370 °C to 8.5 displacements per atom (DPA). Transmission electron microscopy (TEM) characterization including brightfield scanning electron microscopy (BFSTEM), diffraction, and TEM in situ irradiation, energy dispersive spectroscopy (EDS) compositional analysis, and nanoindentation were used to evaluate the radiation induced microstructural evolution and mechanical responses in these model alloys. Microstructure is of particular interest in irradiated nuclear structural materials because it plays an integral role in the mechanical integrity of these materials. Radiation induced defects present obstacles to dislocation motion and thus lead to hardening and embrittlement. P is highly undersized and forms a strong covalent bond with Fe which progresses to an Fe3P beta phase in BCC iron when the solubility limit is reached. The covalent nature of the bonding as well as the smaller atomic volume of P leads to enhanced radiation induced defect nucleation, phosphorus segregation, and radiation induced precipitation. The high density of defects in the Fe-P alloy contributed to enhanced hardening of the irradiated Fe-P alloy in comparison to the Fe-Cr and Fe-N alloys. The density of these defects and depth of the ion irradiated damaged layer and thus the mechanical response is also heavily dependent on orientation and is made evident by nanoindentation and indentation cross section BFSTEM imaging. 

We explore the consequences of micelle formation for diffusiophoresis of charged colloidal particles in ionic surfactant concentration gradients, using a quasi-chemical association model for surfactant self assembly. The electrophoretic contribution to diffusiophoresis is determined by re-arranging the Nernst–Planck equations, and the chemiphoretic contribution is estimated by making plausible approximations for the density profiles in the electrical double layer surrounding the particle. For sub-micellar solutions we find that a particle will typically be propelled down the concentration gradient, although electrophoresis and chemiphoresis are finely balanced and the effect is sensitive to the detailed parameter choices and simplifying assumptions in the model. Above the critical micelle concentration (CMC), diffusiophoresis becomes much weaker and may even reverse sign, due to the fact that added surfactant goes into building micelles and not augmenting the monomer or counterion concentrations. We present detailed calculations for sodium dodecyl sulfate (SDS), finding that the typical drift speed for a colloidal particle in a ∼100 μm length scale SDS gradient is ∼1 μm s −1 below the CMC, falling to ≲0.2 μm s −1 above the CMC. These predictions are broadly in agreement with recent experimental work. 

The diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γ p relative to the solute diffusivity D s for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.