Thermal and mechanical phenomena in laser-material interaction

Nanoscience has attracted significant attention in recent years due to the nanomaterials and nonostructures' potential application in many different fields. Laser assisted micro/nano-machining has been widely applied for micro/nano material processing. For laser material interaction, beginning with the every first step of laser-based processing, the fundamental thermal and mechanical property in laser material interaction is of great importance. In this dissertation, four aspects of the laser material interaction, laser induced shock wave, nanomaterial fabrication and laser infrared photothermal techniques are studied.;First, large-scale hybrid atomistic-macroscale simulation is performed to study the long-time material behavior in nanosecond laser material interaction. Molecular dynamics simulation is conducted to investigate the fundamental mechanism and thermal property in laser material interaction and parallel processing techniques are applied to accelerate the large computing load. Different phase change phenomena are studied, including solid-liquid interface speed, temperature, maximum melting depth, and ablation rate.;Second, dynamic structure and mass penetration of shock wave in laser-material interaction are studied. In this work, the atomistic study of the shock wave formation, its dynamic structure, and mutual mass penetration in picoseconds laser material interaction are reported. An effective mixing length was designed to quantitatively evaluate the mutual mass penetration between the plume and background gas. It is also observed that the relative movement between the plume and the background gas has a significant contribution to this mass penetration.;Third, polymer nanofiber synthesis by using the electrospinning technique is described in Chapter 4. The process parameters to control the polymer nanofiber formation and the characterization of the nanofiber are discussed in detail. The potential application of polymer nanofiber is also discussed.;Finally, the photothermal experiment is designed and conducted to characterize and image the human tooth with early tiny defect. The measure results present an obvious difference between the good area and bad area on the same tooth. The initial pilot study has demonstrated the potential for photothermal technology to measure and detect the tiny defect and deep lesions of the human tooth.