發(fā)布時間：2018-08-03 08:52

【摘要】：基于壓電材料的高頻超聲波換能器能夠發(fā)射并接收短波脈沖并具有極佳的圖像的空間分辨率,在醫(yī)學影像以及無損探傷等領(lǐng)域應用廣泛。具有精細尺寸(20μm)壓電單元的2-2型壓電復合物是一種理想的高頻換能器用功能材料,具有聲阻抗低,機電耦合系數(shù)高,機械強度高等一系列優(yōu)勢。此外,該復合物精細的壓電單元尺寸可以有效地抑制側(cè)向諧振對主振蕩模式的干擾,從而提高換能器的信噪比。近凈成形技術(shù)可以制備無缺陷的精細壓電單元,但該技術(shù)存在的一個問題是燒結(jié)后壓電單元的彎曲導致較差的結(jié)構(gòu)均勻度,因此通過研究壓電單元在近凈成形中的彎曲機制,從而制備出結(jié)構(gòu)精細、均勻的壓電復合物具有重要的意義。 本文首先探討了鈮酸鈉鉀(KNN),鈮鎂酸鉛鈦酸鉛(PMN-PT)與鋯鈦酸鉛(PZT)三種常用壓電體系的合成與性能。采用固相法合成了高純鈮酸鈉鉀(KNN)系壓電粉體。Li、Ta、Sb摻雜顯著的提高了KNN系壓電陶瓷的性能,隨著Ta含量的提高,KNN的壓電性能得到提高。采用熔鹽法合成了高純鈮鎂酸鉛鈦酸鉛(PMN-PT)粉體,在有效抑地制焦綠石相形成的同時,顯著地縮短了合成時間。 通過近凈成形技術(shù)制備了精細結(jié)構(gòu)2-2型壓電復合物,并研究了壓電單元的變形機制。聚合物軟化是近凈成形中導致壓電單元變形的主要因素。采用惰性氣氛脫酯可以有效地抑制壓電單元的變形,從而使獲得的壓電單元尺寸可以達到20μm,并具有±2μm的精度誤差。 研究了壓電復合物結(jié)構(gòu)域性能的關(guān)系。隨著壓電單元高徑比的提高,復合物的機電耦合系數(shù)先增高再降低。對PZT基壓電復合物而言,在高徑比為3.5時,機電耦合系數(shù)最高達到0.61。壓電相體積分數(shù)對復合物性能的影響并不顯著,提高壓電相體積分數(shù),復合物的性能有一定程度的下降。 將PZT基2-2型精細結(jié)構(gòu)壓電復合物封裝為高頻換能器,并進行脈沖-回波測試。結(jié)果表明,基于2-2型精細結(jié)構(gòu)壓電復合物的高頻換能器中心頻率達到23.09MHz,帶寬達到5.5MHz。圖32幅,表7個,參考文獻63篇。
[Abstract]:High frequency ultrasonic transducers based on piezoelectric materials can transmit and receive short wave pulses and have excellent spatial resolution of images. They are widely used in medical images and nondestructive flaw detection. The 2-2 piezoelectric composite with fine size (20 渭 m) piezoelectric element is an ideal functional material for high frequency transducer. It has a series of advantages such as low acoustic impedance, high electromechanical coupling coefficient and high mechanical strength. In addition, the fine piezoelectric element size of the composite can effectively suppress the interference of the lateral resonance to the main oscillation mode, thus improving the signal-to-noise ratio (SNR) of the transducer. Near-net forming technology can fabricate fine piezoelectric elements without defects, but one of the problems in this technology is that the bending of the sintered piezoelectric elements leads to poor structural uniformity, so the bending mechanism of piezoelectric elements in near-net forming is studied. It is of great significance to prepare fine and homogeneous piezoelectric composites. In this paper, the synthesis and properties of (KNN), lead titanate (PMN-PT) and lead zirconate titanate (PZT) are studied. The high purity sodium and potassium niobate (KNN) system piezoelectric powder 路Li-TaTa-Sb doped with high purity sodium and potassium niobate was synthesized by solid state method. The properties of KNN system piezoelectric ceramics were greatly improved by doping. The piezoelectric properties of KNN system were improved with the increase of Ta content. Lead magnesium niobate titanate (PMN-PT) powder was synthesized by molten salt method. The fine structure 2-2 piezoelectric composites were prepared by near-net forming technique and the deformation mechanism of piezoelectric elements was studied. Polymer softening is the main factor leading to deformation of piezoelectric element in near net forming. The deesterification in inert atmosphere can effectively suppress the deformation of the piezoelectric element, and the size of the obtained piezoelectric element can reach 20 渭 m, and the precision error of 鹵2 渭 m can be obtained. The relationship between the domain properties of piezoelectric composites was studied. With the increase of the aspect ratio of piezoelectric elements, the mechatronic coupling coefficient of the composite increases first and then decreases. For PZT based piezoelectric composites, the maximum electromechanical coupling coefficient is 0.61when the aspect ratio is 3.5. The effect of the piezoelectric phase volume fraction on the properties of the composites is not significant. The performance of the composites decreases to a certain extent when the piezoelectric phase volume fraction is increased. The PZT based 2-2 fine structure piezoelectric composite was encapsulated into a high frequency transducer and the pulse echo was measured. The results show that the center frequency of high frequency transducer based on 2-2 fine structure piezoelectric composite is 23.09 MHz and the bandwidth is 5.5 MHz. There are 32 pictures, 7 tables and 63 references.
【學位授予單位】：中南大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TB33;TB552

【共引文獻】

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相關(guān)碩士學位論文 前10條

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本文編號：2161232