Preparation And Characterization Of Gradient Piezoelectric Composite Based On Freezing Orientation

In recent years,traditional fossil energy has been depleted due to excessive consumption,and the resulting energy crisis and environmental problems have become more and more serious.Therefore,accelerating the development of renewable clean energy to alleviate the current crisis has become the development trend of the times.Piezoelectric nanogenerators have the characteristics of converting the tiny mechanical vibration energy in the surrounding environment into electrical energy,adapting to the development trend of low power consumption,miniaturization,and portability of modern electronic components,and are expected to lead a revolution based on new energy technology.However,the development of piezoelectric nanogenerators is also facing new challenges,how to effectively improve its electromechanical conversion efficiency is currently a key issue that needs to be resolved.In view of the above problems,this article was based on the PZT ceramic material with high voltage electric constant and high electromechanical coupling coefficient,and the piezoelectric composite based on the gradient PZT framework structure was prepared by freezing orientation technology,and its microstructure and electrical output performance were studied.The main research contents are as follows:(1)The gradient PZT/PDMS composite was prepared.Based on the ice crystal growth mechanism,the pore structure and ceramic particle connection methods in four different regions of cellular region,transition region,progressive lamellar region and homogenous lamellar region were studied,and the electrical output properties of different regions of the composite were discussed.It was found that the tight connection of the PZT particles in cellular region and transition region resulted in uneven stress distribution,and the larger pores in homogenous lamellar region resulted in too few piezoelectric phases.The progressive lamellar region had a three-dimensional network structure and the pore size and content of PZT particles was moderate,which could effectively improve the electromechanical conversion efficiency of the piezoelectric composite.Compared with other regions,it had better electrical output performance.For example,the output voltage and current of 5.2 vol%PZT/PDMS could reach 152 V and 17.5?A respectively.The output power density could reach 110?W/cm~2 when the external load was 7 M?,which could drive 96 LED lights.(2)The gradient PZT/CNT/PDMS composite was prepared.The influence of different conductive materials and the distribution regions of conductive materials in composite on the electrical properties of composite were discussed.It was found that the internal resistance of the material was reduced and the degree of polarization was enhanced due to the closer contact with the PZT particles when the CNT was in the inner layer of the sheet,it had better electrical output performance than the composite formed between the layers.The output voltage and current of the composite prepared by 5.2 vol%PZT and 4 wt%CNT reached 186V and 26.7?A,respectively,and the output power density was 137?W/cm~2.Adding 5.2 vol% PZT@Ag to the above composite could continue to increase its output voltage to 196 V,output current to 30.6?A,and output power density to 143.5?W/cm~2.This was mainly due to the conductive particles Ag establishing a good contact between the PZT and the CNT to increase the conductive path and at the same time promote the transfer of space charges.(3)The sintered PZT framework-based composite were prepared,and the morphology and electrical output performance of the composite under different framework structures were analyzed and compared.It was found that compared with the unsintered PZT framework,the ceramic framework structure was denser after high temperature sintering,and it had better electrical output performance.The composite prepared with 40 vol%PZT had an output voltage of 174 V,an output current of 28.2?A,and an output power density of 125?W/cm~2under 100 N.The linear relationship of the dynamic pressure sensitivity of the composite was constructed,and it was found that the sensitivity was increased from 0.897 V/N to 1.163 V/N before and after sintering.