医学超声成像用高频压电复合物的冰模板法制备与性能研究

High frequency biomedical ultrasound can be used for imaging smaller and more superficial structures, which may effectively promote the development of clinical diagnosis and treatment. However, the slow development of this field is mainly limited by the current manufacturing technology for piezocomposites with higher frequency. Ice templating method has attracted more attention due to its simple, versatile, low-cost, and adjustable characteristics. Especially, the lamellae structures obtained from ice templating is quite similar to that of novel randomised 1-3 piezocomposites developed recently, making it a potential way to fabricate piezocomposites. The aims of this project are to utilize ice templating method to manufacture randomised 1-3 piezocomposite for higher frequency, to use several methods such as improving the freezing setup, applying electric field, modifying the surface pattern of the cold finger to control the pattern structures, to study the effects of the single factor and coupling factors on the microstructures, mechanical properties and electrical properties of the lamellae PZT ceramics and composites, to investigate the induction mechanism of the cold finger surface pattern on lamellae structures and its intrinsic features during freezing, to reveal the basic law of ice templating used to fabricate lamellae PZT ceramics, to establish the theoretical model based on influence factors (slurry characteristics, temperature gradient, cold finger surface pattern, electric field), microstructures and properties. The final research results are expected to extend the application fields of ice templating technique potentially as a method for piezocomposite, and promote greatly the development of biomedical ultrasound imaging.

利用高频医学超声可以获得较小、更浅层组织的成像，有力地促进临床诊断与治疗，但此领域发展缓慢，主要受限于当前高频压电复合物的制备技术。冰模板法因简单、灵活、成本低、可调控性强已成为研究热点，特别是片状结构与新近发展的无序列阵压电复合物的结构吻合，有望成为高频压电复合物的制备技术。本项目拟采用冰模板法制备1-3型高频PZT压电复合物，通过改进冷冻装置、施加外电场、改变冷板表面排列样式来调控列阵结构的无序性；研究单一条件、耦合条件下获得的PZT陶瓷列阵结构的特征、力学特性及复合物电学性能；探讨冷板表面样式、外电场对列阵结构的诱导机制及相分离过程的特性，揭示冰模板法制备PZT陶瓷列阵结构的规律，建立影响因素（浆料物性-温度梯度-外加电场-冷板排列样式）、列阵结构、力、电学性能相互间关系的理论模型；本研究有望扩大冰模板技术的应用范围使之成为压电复合物制备新技术，并有力地推动医学超声成像的发展。

利用高频医学超声可以获得较小、更浅层组织的成像，有力地促进临床诊断与治疗，但该领域发展缓慢，主要受限于当前高频压电复合物的制备技术，比如切割填充技术。冰模板法因简单、灵活、成本低、可调控性强已成为研究热点，特别是片状结构与新近发展的无序列阵压电复合物的结构吻合，有望成为高频压电复合物的制备技术。本项目采用冰模板法成功制备了PZT压电复合物，并通过改变冷冻速率、浆料固相含量、改变冷板表面排列样式来调控列阵结构；研究发现浆料的固相含量应当合适，过低或者过高都不易形成片状结构；且冷却速率与PZT片状形貌密切相关，大的冷却速率产生微细的片状结构，小的冷却速率则不然，较为深刻地揭示了冰模板法制备PZT陶瓷列阵结构的规律；本研究有望使冰模板技术成为压电复合物制备新技术，并大大降低生产成本，同时可有力地推动医学超声成像的发展。此外，课题研究了掺杂对BNT-BT-BKT三元无铅压电陶瓷体系性能的影响，对于发展无铅压电陶瓷也有一定的促进作用。