Study On? ULTRA ? Short Pulse Laser Controlled Fabrication Of Functional Microstructure On ZrO₂ Bioceramics

ZrO₂ ceramic, as a representative bio-ceramic, has excel ent performances, such as high temperature resistance, corrosion resistance and wear resistance. It also maintains good fracture toughness and bending strength which makes the material can be competent for the clinical application of dental and orthopedics replacement prosthesis. In practical application, the structural accuracy achieved by the technology of ceramic molding and sintering is far from satisfying for the medical acceptable accuracy which is always in microscale. Therefore, it is essential to post-process for the ceramics parts. In this paper, in terms of the requirements of practical applicatio n, taking ZrO₂ ceramic?TZP? which is the most common dental and orthopedics bioceramic as the experimental materials, the ablation characteristics and removal mechanism of by nanosecond/picosecond lasers with short and ultrashort pulse respectively were researched systematically. Based on the foundation study on the two kinds of lasers interaction with the material, the laser precise process of TZP ceramic were optimized, and different functional fine micro-structures of ceramic were achieved.Firstly, the ablation characteristics of TZP ceramic by nanosecond short pulse laser?pulse width: 6 ns? were studied. Fine structures with size accuracy of one hundred micrometer scales by the controllable laser process with high efficiency were achieved via the optimization of the process. The 532 nm short wavelength pulse laser is beneficial for material absorption of laser energy and reducing heat effect. In the experiment, the ablation characteristics of TZP ceramic under different energy density were studied by the variable controlling method. Based on the relationship between ablation depth and machining threshold, the influence of pulse number and scanning speed on the processing threshold was studied. Based on these fundame nta l experiments and optimization of process parameters, fine ladder structure with each step width of 500 ?m and height of 100 ?m was fabricated by focusing shift scanning method with high controllability, as well as, blind hole structure with diameter of 500 ?m and smooth edges was also achieved with high speed using a designed multichannel overlap scanning method. In addition, taking advantage of the slope surface of processed cavity structure resulted from the Gaussian laser beam mode and the limitation of the focusing depth, embedded step with width of 24 + 2 ?m that was smaler than the focused beam size?60 ?m diameter? were obtained on the cavity inner wall by the combination of optimized parameters and processing path..The controllability of high precision fabrication of TZP ceramics by UV picosecond laser whose pulse width is short than that of nanosecond one was studied. Through the experimental study of UV ultrashort pulse picosecond laser interactio n with TZP ceramic, the basic interaction rules of 355 nm UV picosecond laser parameters including laser power, the amount of defocus, the scanning times and the scanning speed on TZP ceramics were studied by variable controlling method, the range of process parameters for high quality process of TZP ceramic was determined as well as. To design responding micro arc groove and columnar structures based on the Wenzel and Cassie model for wettability, the surface wettability of TZP ceramic can be adjusted by changing the characteristic value of structure due to the changing of laser processing parameters. The wetting angle can be variable from 10°to 133°. Adjustment material wettability by laser surface modification has the advantages on efficiency, pollutio nfree and long service time. The hydrophilic surface of TZP ceramics is good for cell adhesion and orientation growth while the hydrophobic surface of TZP ceramic can resist the hydrolysis of the adhesive surface and with a certain antibacterial effect. Through this research, the free bidirectional conversion between hydrophilicity and hydrophobicity of ceramic functional surface was achieved by picosecond laser surface modification according to the various practical applications of TZP ceramics in the biomedical field. It provides a good foundation for further research on the applicatio n of ZrO₂ ceramic materials in the field of biomedicine.