Research On Mechanism And Technology Of Laser Near-field Micro-texturing Based On Nanoparticles

With the development of laser technology,laser near-field manufacturing technology using near-field enhancement effect can achieve the resolution beyond the diffraction limit.Among them,the laser near-field processing technology based on nanoparticles is an attractive method,which can produce controllable micro holes in large area.The method comprises the following steps: depositing monolayer nanoparticles on the surface of the workpiece,using the nanoparticles to modulate the light field,and forming a local field enhancement effect,which can produce a large area of micro holes on the workpiece surface with high flexibility and low cost.A wide range of applications can be applied to surface nano-patterning,nano-scale deformation,biophotonics and other fields.In this paper,combining with simulation and experiment,we conducted the study of laser near-field micro-modeling technology on titanium alloy surface by using nanosecond laser as a processing light source.The near-field enhancement effect of two different particle types was simulated by means of simulation software to realize the micro holes fabrication on titanium alloy surface.The effects of energy density and lap ratio on the morphology and distribution of micro holes were studied,and the morphology of laser drilling as well.The main contents of this paper are as follows:1.The effect of local field enhancement on the titanium alloy surface under different nanoparticles was simulated.The FDTD software was used to find near-field enhancement mechanism formation produced by the dielectric nanoparticles and the noble metal nanoparticles.The electric field distribution on titanium alloy surface under the processing parameters such as the wavelength of the laser,the angle of incidence and the background refractive index in the simulation model were investigated,which provided theoretical guidance for the follow-up experiment.2.The optimization of the deposition parameters of monolayer silica nanoparticles on titanium alloy surface.By analyzing the behavior between nanoparticles,the spin coating method was used to carry out particle deposition,and the effect of single layer deposition on the metal surface under different spin coating parameters was studied.The addition of super wetting agent to form hydrophilic film was used to improve the surface hydrophilic,to achieve a large area of nano-particles arranged on titanium alloy surface.3.The effect of nanoparticles on the micro holes fabrication and perforation of single pulse was studied on titanium alloy surface.The effects of parameters such as energy density and spot lap on the distribution of micro holes and pore size were studied.The "connection line" phenomenon between the micro holes was found in the experiment section,which was related to the spacing between the nanoparticles and the energy density of the pulsed laser properly.In order to explore the regulation of nanoparticles on laser pulse energy,the nanoparticles were found out to maintain the shape of laser single pulse punching,reducing the generation of spatter,and played a certain role in the pore size constraint.