<b>Plasma-Involving Laser-based Manufacturing, Laser Fabrication of Metal Composites and Ceramics</b>

<p dir="ltr">This dissertation presents research work related to laser micro sintering, laser-induced plasma deburring, laser fabrication of ceramics and CNT-metal composite.</p><p dir="ltr">Firstly, we present the development of a physics-based model for double pulse laser micro sintering (DP-LMS), which typically utilizes long nanosecond (ns) laser pulses to melt metal powders and a followed short ns laser pulse to generate plasma-induced high pressure that promotes melt flow and fills voids. Chapter 2 shows a thermal model that predicts the temperature history in the power bed under ns laser irradiation. The model has been validated by comparison with the measured temperature. Chapter 3 shows an integrated physics-based model that simulates the thermal and hydrodynamic processes in DP-LMS. The model is used to evaluate the effect of plasma-induced pressure on the densification enhancement, and also reveals the effects of the long ns laser pulses on the plasma generated by the following short ns laser pulse.</p><p dir="ltr">Secondly, we present extensive experimental studies of laser-induced plasma micro-deburring (LPD). Chapter 4 shows LPD on an aluminum-alloy workpiece using plasma generated from sacrifice plates made of different materials. Residual effects of LPD on the workpiece have been discussed. Chapter 5 shows time-resolved imaging and optical emission spectroscopy (OES) measurements of the plasma generated by high intensity ns laser in a channel with and without burrs on the channel sidewalls. The effects of the burrs on laser-induced plasma have been revealed.</p><p dir="ltr">Thirdly, in Chapter 6 we present preliminary work on an additive manufacturing process for ceramics, which is called pulsed-continuous dual-beam selective laser melting (PC-DB-SLM). In this process, a pulsed laser beam is used to generate melt pool, and a CW laser beam is used to reduce the temperature gradient. The work shows that the PC-DB-SLM process has a great potential to address challenges associated with SLM of ceramic parts.</p><p dir="ltr">Finally, we present the experimental work on laser fabrication of carbon nanotube-metal composite in Chapter 7, showing high densification and hardness.</p>