| Piezoelectric ceramics are functional materials that can achieve force-to-electric conversion through the piezoelectric effect and are widely used in many fields such as biology,military,optoelectronic information and renewable energy.Among them,barium titanate(BTO)is one of the most widely used lead-free piezoelectric ceramics and is preferred because of its higher safety and environmental friendliness.Therefore,how to manufacture complex structures and shape of piezoelectric devices with high efficiency,high utilization and low production cost has become a hot topic of discussion.Additive manufacturing(AM)technology is considered to be the best process for complex structured devices due to its unique two-dimensional stacked molding method.The existing AM technologies that can realize the molding of piezoelectric ceramics include stereo light-curing molding(SLA),extrusion molding(EFF),fused deposition molding(FDM),direct paste writing(DIW),digital light processing molding(DLP).Among them,DLP molding technology has become the first choice for piezoelectric ceramic printing due to its high molding efficiency and the good performance of the molded piezoelectric devices in terms of piezoelectric performance,print resolution,surface quality and,denseness.However,the performance of DLP printed parts is influenced by various factors,such as the selection of raw materials,the choice of the printing method,and the choice of heat treatment scheme.In summary,this thesis focuses on the preparation of lead-free piezoelectric ceramics with high-performance and complex structures,including the optimization of the printing process(ceramic paste configuration,lightcuring molding,heat treatment process,and polarization process),the addition of printing substrates,the influence of printing orientation and part structure,and its application to energy harvesting and force sensors.The main studies are as follows:(1)The influence of individual raw material choices during ceramic paste configuration on the print performance of the paste was discussed.The results showed that either too large or too small a powder particle size negatively affected both the viscosity and the curing properties of the paste.The highest solids content of 80 wt% was achieved with this particle size,but the slurry was less formable at this solids content.In addition,the addition of dispersant contributes to a better dispersion of the ceramic powder in the resin,so its specific content is also information of interest.The effect of different printing orientations on the piezoelectric properties of the piezoelectric devices was found,and finally,the least loss of piezoelectric properties was achieved by a reasonable printing orientation.(2)The influence of parameter settings of the three core processes of degreasing,carbon removal,and sintering on the heat treatment effect during the heat treatment process was found.Information on the holding point of the degreasing process was obtained by thermogravimetric analysis of the raw printed ceramic parts.One of the ramping rates needs to be as fast as possible to maintain piezoelectric part integrity and high densities.The sintering temperature during the sintering process is also an extremely important process parameter that has a significant impact on the surface quality and piezoelectric properties of the piezoelectric ceramic devices.The effects of polarization field strength,polarization time,and polarization temperature on the piezoelectric constants of piezoelectric ceramics during the polarization process are discussed.(3)A piezoelectric model with adjustable porosity was designed based on the P-type TPMS structure and printed with an optimized printing process.It was found that the model piezoelectric device not only has good piezoelectric performance but also has a high degree of lightweight.The application of this high-porosity device in energy harvesting and force electrical sensors is also explored. |
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