多元高频拉胀压电复合材料的制备及构效关系研究

High frequency ultrasonic (HUFS) have received intensive attention for their potential high resolution imaging applications, such as ophthalmology, dermatology and vascular surgery. The preferred active material in HFUS is the 1-3 piezoelectric composites, because of their higher electromechanical coupling coefficient and lower acoustic impedance. However, there are two disadvantages existing in the conventional high frequency piezoelectric composites. First, the spurious mode resulting from the periodic structure will be coupled with the thickness mode at high frequency. Second, the lateral clamping of the rods by the polymer will cause the sharp decrease in the electromechanical coupling coefficient. Therefore, the development of the high frequency auxetic piezoelectric multiple composite with complex structures is imperative. In this work, a modified gelcasting of PZT based piezoelectric ceramics combing with the soft mold is developed for the fabrication of the piezoelectric arrays with complex architectures. The auxetic microporous polyethylene with the inclusion of the Metal Organic Frameworks is severed as the polymeric matrix. And the auxetic piezoelectric composite is obtained after lapping and poling. The influences of the polymer properties and the structural parameters of the PZT pillar array will be studied. This research will develop an understanding of the mechanism for the polymer properties and performance-structure correlation to affect the high frequency performance, offering avenues for optimizing the performance of the piezoelectric composite. And this will greatly promote the development of the high performance HFUS technique.

针对传统压电复合材料存在阵列结构简单且周期性强易引发寄生模式以及聚合物的横向夹持作用导致声-电转换效率低等缺点，本项目拟采用锆钛酸铅基凝胶注模成型技术和软模法相结合的新型陶瓷微加工技术，制备具有复杂结构参数的压电陶瓷阵列，并采用金属有机框架化合物（MOF）/拉胀聚乙烯复合物进行包封，经减薄和极化处理后获得多元高频拉胀压电复合材料，进而探讨MOF/拉胀聚乙烯复合物以及陶瓷阵列结构参数对多元拉胀压电复合材料性能的影响，结合计算机仿真，分析在工作模式下上述因素对各相振动以及陶瓷微柱压电响应的影响，揭示其对复合材料高频性能的影响机理，为压电复合材料结构设计以及性能优化提供依据。本项目的顺利实施将为高性能高频超声成像技术的发展提供理论依据和技术支持，对促进其在临床医学领域的应用具有重要意义。

高频超声成像技术因其微米级空间分辨率，能够为眼睛、皮肤以及血管等精细器官提供高精度成像而受到广泛关注。1-3型压电复合材料具有声阻抗低且机电耦合系数高等优点已成为高频超声成像技术的核心材料。然而传统制备技术如切割填充法等均难以满足高性能压电复合材料中微米级陶瓷阵列制备需求，因此本项目发展了甘油增韧纳米纤维素晶-二甲基丙烯酰胺为凝胶体系的锆钛酸铅凝胶注模成型技术，系统地研究了甘油含量和固相含量对其性能的影响，研究表明，浆料粘度随着固相含量和甘油含量的增加而增大，但即使固相含量达到57.5vol.%或甘油含量达到20.0wt.%，浆料依然能满足浇注需求；陶瓷生坯强度随着甘油含量的增加而降低，但其塑性显著改善，当甘油含量仅为10.0wt.%时，生坯弯曲150°时其表面仍没有裂纹出现；烧结坯平均强度和Weibull模量随着固相含量和甘油含量的增加呈现先增加后降低的变化趋势，当甘油含量为10.0wt.%且固相含量为52.5vol.%时，烧结坯平均强度和Weibull模量达到最大值，分别为84.03±5.58 MPa和16.89，此时烧结坯内微观结构均匀性最佳。将锆钛酸铅陶瓷凝胶注模成型与聚二甲基硅氧烷软模法相结合，制备了具有任意截面形状及无规则排布的PZT陶瓷微柱阵列，且阵列结构完整度好微柱形状保真度高，本项目为高性能高频超声成像技术的发展提供技术支持，对促进其在临床医学领域的应用具有重要意义。