Caizhen Yao

Preparation of broadband absorption ceramic coatings by using plasma electrolytic deposition

Two types of black ceramic coatings with high spectrum absorptivity were prepared on Al alloy substrate by using plasma electrolytic deposition method. The spectrum absorption properties of coatings were tested by using 355 nm ultraviolet laser pulses. Particle counter device was employed to collect and analyze the particles formed during the irradiation process. Experimental results showed that the coatings have porous structures. The sample coatings 1 and 2 have thickness of 120 μm and 60 μm with holes’ diameter of about 70 μm and 15 μm, respectively. The coating 1 is mainly composed of Al2O3 and SiO2 while coating 2 consists of Al2O3. The reflectivity of both coatings is much lower than that of Al alloy substrate. The absorptivity of samples 1 and 2 is about 99.88% and 99.92% for wavelength from 300 nm to 800 nm. The mechanisms of spectrum absorption were also explored.

The formation of periodic micro/nano structured on stainless steel by femtosecond laser irradiation

Stainless steel surface was irradiated by linear polarized laser (800 nm, 35 fs, 4 Hz and 0.7 J/cm2) with different pulse numbers. Environmental scanning electron microscope (ESEM/EDS) was used for detailed morphology, microstructure and composition studies. The wettability of irradiated steel surface was tested by Interface Tensiometer JC-2000X and compared with untreated stainless steel. Results showed that micro/nanostripes with different periods were formed. The period increased with the increasing pulse numbers from 450 nm for 90 pulses to 500 nm for 180 pulses. The orientation of those stripes was parallel with the laser beam polarization. Nanoparticles were observed on those periodic structures. EDS indicated that the atomic ratio of Cr increased and the atomic ratios of Fe and Ni decreased after laser irradiation, which may enhance the corrosion resistance due to the Cr-rich layer. The prepared structure exhibited hydrophobic property without further treatment. The formation mechanism of micro/nanoperiodic structures was also explored.

Laser cleaning of the contaminations on the surface of tire mould

During the manufacturing of tires, surface pollutants on tire mould will lead to the production of unqualified tires. Tire moulds need to be regularly cleaned. Laser cleaning is recognized as a non...

Cleaning mechanism of particle contaminants on large aperture optical components by using air knife sweeping technology

The cleaning mechanism of optical surface particle contaminants in the light pneumatic tube was simulated based on the static equations and JKR model. Cleaning verification experiment based on air knife sweeping system and on-line monitoring system in high power laser facility was set up in order to verify the simulated results. Results showed that the removal ratio is significantly influenced by sweeping velocity and angle. The removal ratio can reach to 94.3% by using higher input pressure of the air knife, demonstrating that the air knife sweeping technology is useful for maintaining the surface cleanliness of optical elements, and thus guaranteeing the long-term stable running of the high power laser facility.

Influence of secondary treatment with CO2 laser irradiation for mitigation site on fused silica surface

The ablation debris and raised rim, as well as residual stress and deep crater will be formed during the mitigation of damage site with a CO2 laser irradiation on fused silica surface, which greatly affects the laser damage resistance of optics. In this study, the experimental study combined with numerical simulation is utilized to investigate the effect of the secondary treatment on a mitigated site by CO2 laser irradiation. The results indicate that the ablation debris and the raised rim can be completely eliminated and the depth of crater can be reduced. Notable results show that the residual stress of the mitigation site after treatment will reduce two-thirds of the original stress. Finally, the elimination and the controlling mechanism of secondary treatment on the debris and raised rim, as well as the reasons for changing the profile and stress are analyzed. The results can provide a reference for the optimization treatment of mitigation sites by CO2 laser secondary treatment.