The process of spark erosion employs an electric discharge to break down bulk materials into fine powders and has been developed to produce nanostructured powders of metallic, ceramic, and semiconducting materials. This work demonstrates the optimization of charge morphology, energy parameters, and liquid dielectric of a “shaker-pot” spark erosion process to produce maximum yields and size-specific nanopowders. Nanopowders were assessed using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission scanning electron microscopy (t-SEM), dynamic light scattering (DLS), and a new multispectral advanced nanoparticle tracking analysis (MANTA) technique. Additional efforts were taken to evaluate the new MANTA technique and its performance capabilities and limitations for application in fast and accurate particle size analysis. A single-spark apparatus was also constructed to evaluate the discharge mechanics relevant to nanoparticle formation. High-speed imaging and spectroscopy were used to investigate the characteristic plasma arc, shock wave, and plume evolution in a submerged capacitive discharge system. The effects of varying both the capacitance and liquid dielectric (liquid nitrogen/ethanol) are evaluated. Discharge features such as plume temperature and time are discussed with respect to previous findings and active particle formation mechanisms that influence size-tunability of the spark erosion technique.

Non-conservative processes play a fundamental role in plasticity and are behind important macroscopic phenomena such as creep, dynamic strain aging, loop raft formation, etc. In the most general case, vacancy-induced dislocation climb is the operating unit mechanism. While dislocation/vacancy interactions have been modeled in the literature using a variety of methods, the approaches developed rely on continuum descriptions of both the vacancy population and its fluxes. However, there are numerous situations in physics where point defect populations display heterogeneous concentrations and/or non-smooth kinetics. With this in mind, in this work we present a kinetic Monte Carlo model that discretely captures vacancy generation and transport kinetics acting in conjunction with the evolving elastic fields provided by discrete dislocation dynamics simulations. The two models are coupled via the applied stresses and stress gradients generated by dislocation structures at vacancy locations. To extend the coupled model to the treatment of large systems, we cast the entire elasto-plastic-diffusive problem within a single stochastic framework, taking advantage of a parallel kMC algorithm to evolve the system as a single event-driven process. After introducing the numerical procedure and validation, we compare the method to existing continuum formulations and examine several macroscopic phenomena including non-conservative plastic bypass of a precipitate, dipole coalescence, and vacancy trap formation.