Laser induced plasma in liquid/solid-liquid interface and implication on nucleation of nanoparticles
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2011
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Abstract
The present work focuses on transient evolution of pulsed laser induced breakdown process in liquid and solid-liquid interface. The focusing of high power laser inside a liquid media leads to plasma formation and shockwave emission. When the same process takes place at a solid-liquid interface, the plasma from the solid target interacts with the surrounding liquid and under suitable condition results into formation of nanoparticulates. On a larger time scale, plasma is replaced by cavitation vapor bubbles which expands and collapses in order to maintain the pressure gradient with the surrounding liquid. In the present work, the complete dynamics of laser induced breakdown in water and metal-water interface is studied. For this various diagnostics; beam deflection set-up, shadowgraphic technique, electric probes and plasma spectroscopy were devloped. Beam deflection was employed to study the spatial and temporal evolution of shockwave velocity and cavitation bubble dynamics at the breakdown region. The shockwave velocity and cavitation bubble expansion velocity at the breakdown region were found to be in the range of 104 m/s and 102 m/s respectively. The multiple bubble hydrodynamics was studied via shadowgraphic technique to unleash the bubble evolution and bubblebubble interaction. The electric probe was used to record the transient conduction and corresponding thermal diffusivity of laser produced water plasma. The plasma spectroscopy was performed to detect the Hydrogen bonded OH, O2 and HO2* produced during laser induced breakdown of water. Laser induced breakdown at metal-water interface is used to synthesize Titanium breakdown is altered to tailor the size and structural properties of the nanoparticles. The measurement of pressure and temperature using beam deflection set-up and plasma spectroscopy during laser induced breakdown at solid-liquid interface is used to estimate the nucleation time, growth velocity and size of nanoparticles and compared with experimentally observed size of nanoparticles. The nanoparticles are characterized using TEM, Raman, UV-Vis and Photo Luminescence spectra. The applicability of the synthesized titanium oxide nanoparticles as photocatalyst and copper oxide nanoparticles as antibacterial agent are also reported....
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Supervisor: Alika Khare
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PHYSICS