Experimental and numerical study of nanoparticles for potential energy applications
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This thesis investigates both experimentally and numerically the oxidation, sintering, melting and solidification processes of different nanoparticles under various thermodynamic scenarios, with a background for energy applications. Two sets of main techniques are adopted in this work, which are isoconvensional kinetic analysis and molecular dynamics simulation. Based on the techniques of simultaneous Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), for first time the isoconvensional kinetic analysis is applied to study the oxidation of nickel and tin nanoparticles. This method is demonstrated capable of modelling one-step nanoscale oxidation and revealing underling kinetic mechanisms. Moreover, some distinct features of nanoparticle oxidation compared with their bulk counterparts are found such as melting depression, oxidation kinetic change in the vicinity of Curie point of nickel and pressure-related two-step oxidation of tin nanoparticles. The detailed study from Molecular Dynamics (MD) simulation establishes a three-stage sintering process of two nickel nanoparticles, which is unable to be described by bulk continuum-level models. MD is applied to study the interaction between nickel and aluminium and its consequent thermo-mechanical and structural property evolution in a nickel-coating aluminium particle in a heating and cooling cycle. The simulation successfully predicts the atomic diffusion during melting and the formation of glass and crystal phases, and allows for the estimation of interior core-shell pressure. Reactive MD is then applied to simulate the oxidation of silicon nanoparticles. It predicts well the exothermal reaction process and experimentally reveals the oxygen exchange process.
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