1-3-2型压电陶瓷/聚合物复合材料的理论模型

根据Chan的1-3型复合材料理论模型和Newnham的复合材料串并联理论,提出了一种用于计算新型1-3-2型压电陶瓷/聚合物复合材料的介电常数和压电常数的理论模型.并制备了一批1-3-2型压电复合材料样品,把理论模型的计算值与实际测量的材料参数进行了比较,结果表明两者符合较好,误差小于10%.     

1-3型压电纤维复合材料的制备及性能研究

用粉末-溶胶混合物挤出法制备了直径为300μm和400μm的PZT压电纤维,研究了纤维的显微结构、密度和收缩率.采用排列-浇铸法制备了纤维体积分数为25%的1-3型压电纤维复合材料,计算了材料的介电常数、机电耦合系数和机械品质因数.结果表明:1-3型压电复合材料的Kp小于压电陶瓷片,Kt和Kt/Kp都大于陶瓷片;相同体积分数的压电纤维复合材料,直径为400μm的纤维制备的复合材料其εT,d33,Kt和Kt/Kp都大于直径为300μm的纤维制备的复合材料.     

基于ANSYS的0-3型压电复合材料电荷分布

通过MATLAB软件对陶瓷颗粒均匀分布的0-3型压电陶瓷/聚合物复合材料进行了建模,通过有限元分析软件ANSYS,研究了压电复合材料受力时内部应力分布及电荷分布状态,同时研究了压电陶瓷颗粒体积分数及静态载荷变化时,压电陶瓷/聚合物复合材料中压电陶瓷产生的最大节点电压的变化情况.研究表明:压电陶瓷/聚合物复合材料在受力时,压电相受到的应力远远大于聚合物相,压电相棱角处受到的应力最大,产生的电荷最多.随着压电陶瓷体积分数变化,压电复合材料中压电陶瓷产生的最大节点电压也增加,当压电陶瓷体积分数达到30％时,产生的最大节点电压达到2.86×10-5V.随着静态载荷的增加,压电复合材料产生的最大节点电压呈线性增加,阻尼效果越明显,与文献中的实验结果吻合.     

3-2型压电复合材料的静水压特性研究

基于压电复合材料的串并联理论以及等效参数理论,推导了3-2型压电复合材料的等效性能参数的计算公式,并针对PZT5/环氧树脂618构成的3-2型复合材料,将计算值与实验结果进行了比较,对理论公式进行了验证,结果表明二者吻合较好.应用理论公式对3-2型压电复合材料的压电性能进行了分析,得出3-2型压电复合材料比1-3型压电复合材料具有更高的静水压压电常数,同时确定了3-2型复合材料中压电陶瓷体积百分比的优选范围.     

1-3型水泥基压电复合材料的制备及性能

采用切割-浇注法, 以硫铝酸盐水泥为基体, 制备了1-3型水泥基压电复合材料。详细阐述了1-3型水泥基压电复合材料的制备过程; 研究了0.375Pb(Mg_1/3Nb_2/3)O₃-0.375PbTiO₃-0.25PbZrO₃压电陶瓷柱的宽厚比w/t对1-3型水泥基压电复合材料的压电性能、 介电性能和声阻抗的影响。结果表明: 压电陶瓷柱的宽厚比w/t对1-3型水泥基压电复合材料性能有很大影响, 随着w/t的增加, 其压电应变常数d₃₃、 机电耦合系数K_p与K_t、 机械品质因数Q_m、 介电常数ε_r和介电损耗tanδ均随着w/t的增加而减小, 而压电电压常数g₃₃值几乎不受w/t的影响。在压电陶瓷体积分数仅为22.72%的条件下, 调节压电陶瓷柱的宽厚比w/t至0.130, 可使复合材料的声阻抗与混凝土的声阻抗十分接近, 从而有效地解决了智能材料在土木工程中的声阻抗相容性问题。     

水泥基压电复合材料的研究进展

综述了水泥基压电复合材料的研究进展.对于0-3型水泥基压电复合材料,压电陶瓷相的性能、复合材料的制备工艺以及微观结构等对其压电及介电性能有重要影响.压电陶瓷相含量越高、粒度越大,复合材料的压电响应就越大.提高极化电压有助于增强复合材料的压电响应.增加成型压力可提高复合材料微观结构的致密性,从而提高压电性能.总结了压电陶瓷的体积分数、形貌以及环境湿度与1-3型水泥基压电复合材料的性能关系,介绍了2-2型水泥基压电复合材料的传感效应及驱动效应的相关研究成果,最后展望了该领域的发展前景.     

基于ANSYS的0-3型压电复合材料电荷分布

通过MATLAB软件对陶瓷颗粒均匀分布的0-3型压电陶瓷/聚合物复合材料进行了建模, 通过有限元分析软件ANSYS, 研究了压电复合材料受力时内部应力分布及电荷分布状态, 同时研究了压电陶瓷颗粒体积分数及静态载荷变化时, 压电陶瓷/聚合物复合材料中压电陶瓷产生的最大节点电压的变化情况。研究表明: 压电陶瓷/聚合物复合材料在受力时, 压电相受到的应力远远大于聚合物相, 压电相棱角处受到的应力最大, 产生的电荷最多。随着压电陶瓷体积分数变化, 压电复合材料中压电陶瓷产生的最大节点电压也增加, 当压电陶瓷体积分数达到30%时, 产生的最大节点电压达到2.86×10^-5 V。随着静态载荷的增加, 压电复合材料产生的最大节点电压呈线性增加, 阻尼效果越明显, 与文献中的实验结果吻合。     

压电复合材料用于透镜式聚焦换能器的研究

为了增加聚焦换能器的带宽, 抑制其多模振动耦合现象, 提高电声转换效率, 实验采用1-3型压电复合材料代替压电陶瓷作为超声发射材料, 设计并制作了一种新型的1-3型压电复合材料透镜式聚焦换能器。通过频率特性的对比研究, 证明了1-3型压电复合材料透镜式聚焦换能器不仅能增加换能器的带宽, 达到PZT压电陶瓷透镜式聚焦换能器带宽的3.13倍, 而且能明显抑制径向振动, 得到单一纯净的厚度振动模态。另外, 1-3型压电复合材料透镜式聚焦换能器的电声转换效率达到PZT压电陶瓷透镜式聚焦换能器的1.88倍, 为高效率聚焦超声换能器的实现提供了理论及实验基础。     

1-3-2压电陶瓷/聚合物复合材料圆柱型换能器制备

改进的1-3(1-3-2)型压电复合材料由1-3压电复合材料与陶瓷基底沿陶瓷极化方向串联而成,其不仅具有与1-3复合材料相同的优点,而且克服了1-3复合材料遇热和受压容易变形等缺点。利用改进的1-3型压电复合材料制作的圆柱型水声换能器在直径为70mm时,其谐振频率为72kHz;发射电压响应为139dB;在20～60kHz频率范围内接受电压灵敏度为-212(起伏±4dB)。换能器水平方向具有基本均匀的指向性,垂直方向波束宽度为12°。     

1-3型聚合物改性水泥基压电复合材料的制备及其性能

采用切割-浇注法，以聚合物改性硫铝酸盐水泥为基体，铌锂锆钛酸铅(简称P(LN)ZT)为功能体制备了1-3型聚合物改性水泥基压电复合材料。研究了P(LN)ZT陶瓷体积分数对复合材料的压电和介电性能的影响。结果表明：随着P(LN)ZT陶瓷体积分数的增加，压电应变常数d₃₃、相对介电常数εr和声阻抗率Z呈现明显的增大趋势；而压电电压常数g₃₃和介电损耗tanδ则呈现下降趋势。与P(LN)ZT陶瓷相比较，1-3型压电复合材料厚度方向振动增强，机械品质因素明显降低，当P(LN)ZT陶瓷体积分数为30.86%时，其声阻抗率为8.24×106 N·s/m3，接近于混凝土的声阻抗率9.0×106 N·s/m3，适用于制作混凝土超声无损检/监测换能器。     

Modeling 1-3 composite piezoelectrics: thickness-mode oscillations

A simple physical model of 1-3 composite piezoelectrics is advanced for the material properties that are relevant to thickness-mode oscillations. This model is valid when the lateral spatial scale of the composite is sufficiently fine that the composite can be treated as an effective homogeneous medium. Expressions for the composite's material parameters in terms of the volume fraction of piezoelectric ceramic and the properties of the constituent piezoelectric ceramic and passive polymer are derived. A number of examples illustrate the implications of using piezocomposites in medical ultrasonic imaging transducers. While most material properties of the composite roughly interpolate between their values for pure polymer and pure ceramic, the composite's thickness-mode electromechanical coupling can exceed that of the component ceramic. This enhanced electromechanical coupling stems from partially freeing the lateral clamping of the ceramic in the composite structure. Their higher coupling and lower acoustic impedance recommend composites for medical ultrasonic imaging transducers. The model also reveals that the composite's material properties cannot be optimized simultaneously; tradeoffs must be made. Of most significance is the tradeoff between the desired lower acoustic impedance and the undesired smaller electromechanical coupling that occurs as the volume fraction of piezoceramic is reduced.     

Interdigital pair bonding for high frequency (20-50 MHz) ultrasonic composite transducers

Interdigital pair bonding is a novel methodology that enables the fabrication of high frequency piezoelectric composites with high volume fractions of the ceramic phase. This enhancement in ceramic volume fraction significantly reduces the dimensional scale of the epoxy phase and increases the related effective physical parameters of the composite, such as dielectric constant and the longitudinal sound velocity, which are major concerns in the development of high frequency piezoelectric composites. In this paper, a method called interdigital pair bonding (IPB) is used to prepare 1-3 piezoelectric composite with a pitch of 40 microns, a kerf of 4 microns, and a ceramic volume fraction of 81%. The composites prepared in this fashion exhibited a very pure thickness-mode resonance up to a frequency of 50 MHz. Unlike the 2-2 piezoelectric composites with the same ceramic and epoxy scales developed earlier, the anticipated lateral modes between 50 to 100 MHz were not observed in the current 1-3 composites. The mechanisms for the elimination of the lateral modes at high frequency are discussed. The effective electromechanical coupling coefficient of the composite was 0.72 at a frequency of 50 MHz. The composites showed a high longitudinal sound velocity of 4300 m/s and a high clamped dielectric constant of 1111 epsilon 0, which will benefit the development of high frequency ultrasonic transducers and especially high frequency transducer arrays for medical imaging.     

Simple model for piezoelectric ceramic/polymer 1-3 composites used in ultrasonic transducer applications

A theoretical model is presented for combining parameters of 1-3 ultrasonic composite materials in order to predict ultrasonic characteristics such as velocity, acoustic impedance, electromechanical coupling factor, and piezoelectric coefficients. Hence, the model allows the estimation of resonance frequencies of 1-3 composite transducers. This model has been extended to cover more material parameters, and they are compared to experimental results up to PZT volume fraction ν of 0.8. The model covers calculation of piezoelectric charge constants d₃₃ and d₃₁. Values are found to be in good agreement with experimental results obtained for PZT 7A/Araldite D 1-3 composites. The acoustic velocity, acoustic impedance, and electromechanical coupling factor are predicted and found to be close to the values determined experimentally     

相扩散阻挡法制备铁酸钴/改性钛酸铋钠0-3复合多铁性陶瓷

通过溶胶-凝胶工艺在CoFe₂O₄(简称CFO)粉体表面包覆二氧化锆陶瓷层来阻挡烧结过程中铁磁相与铁电相之间的离子扩散. 包覆后的CFO与0.92(Bi_0.5Na_0.5)TiO3-0.02(Bi_0.5K_0.5)TO₃-0.06BaTiO₃(简称BNBT) 陶瓷粉体分别按照xCFO/(1-x) BNKLABT (质量分数x = 0.05、0.10、0.15、0.20、0.25、0.30)混合均匀, 并用聚乙烯醇为粘结剂模压成圆片; 再经过1050℃烧结制备了铁磁/铁电0-3型复合材料. XRD分析表明: 二氧化锆在高温烧结过程中对离子扩散具有良好的阻挡作用. 复合陶瓷的耐击穿电压大于75kV/cm. 测量结果表明: 复合陶瓷的压电应变常数、机电耦合系数、介电常数和剩余极化随CFO含量的增加而降低; 磁电耦合系数、介电损耗随CFO含量的增加而有所增大. -35mm×1.5mm的复合陶瓷样品(x=0.05)在谐振频率(90kHz)和199kA/m 偏置磁场下的磁电系数为1.39V/A.     

Fabrication and properties of piezoelectric composites designed for process monitoring of cement hydration reaction

A series of receiving type piezoelectric composites were designed and fabricated by cutting and filling technique. The piezoelectric composites were also optimized from such aspects as matrix phase, functional phase and composite connectivity. The researches show that these piezoelectric composites have larger piezoelectric voltage factor, thickness electromechanical coupling coefficient and lower acoustic impedance than the pure piezoelectric ceramic. The early cement hydration reaction process monitoring result indicates that the ultrasonic wave receiving ability of the piezoelectric composite is obviously better than that of the pure piezoelectric ceramic. Therefore, these kinds of piezoelectric composites have potential application prospect in cement hydration reaction process monitoring.     

Alkaline niobate based lead-free ceramic fiber/polymer 1-3 composites: processing and electromechanical properties

The 1-3 type lead-free piezofiber/epoxy composites were prepared using Li, Ta and Sb modified (Na, K)NbO₃ compositions as the ceramic phase by means of fiber arrangement and epoxy cast. The dense and smooth piezoelectric ceramic fibers with a diameter of 250 μm or less were fabricated by extruding plastic mud pie through micro-holes drilled in a hard mould by means of a laser-cutter. The dielectric, piezoelectric, electromechanical coupling properties and acoustic impedance characteristic of the as-prepared 1-3 composites with different ceramic volume fractions were characterized and compared with the theoretical values as well as those of monolithic ceramics. A nearly pure thickness vibration mode with a resonance frequency over 2 MHz (sample thickness ~1 mm) was formed, together with a high electromechanical coupling coefficient (k _t  ~ 0.55–0.6), low acoustic impedances (Z ~ 9–14 MRayl) and relatively high piezoelectric voltage coefficient (g ₃₃ ~ 30 × 10⁻³ m²/C). The results indicate that those composites have potential to be transducer elements in various applications.     

PVDF/PZNZT压电复合材料的结构与性能

为了扩展压电复合材料的应用领域,首先,通过固相合成法制备了0-3型聚偏氟乙烯(PVDF)/Pb(Zn_1/3Nb_2/3)_0.05Zr_0.47Ti_0.48O₃ (PZNZT)压电复合材料;然后,研究了PVDF含量对PVDF/PZNZT复合材料物相、显微结构及性能的影响。结果表明:PZNZT陶瓷粉料与PVDF粉料混合后,其平均粒度接近于纯PVDF粉料的。于220℃下烧结后, PVDF/PZNZT复合材料在XRD谱图中主要显现出PZNZT钙钛矿结构的衍射峰。当PVDF含量较低时, PZNZT陶瓷晶粒间的结合较松散;随着PVDF含量的增加,陶瓷晶粒几乎都被PVDF相包围。因显微结构不同,不同PVDF含量的PVDF/PZNZT复合材料在极化电场中呈现出不同的串、并联电路。极化后, 5wt% PVDF/PZNZT复合材料的电性能最佳,其介电常数为116、介电损耗tan δ为0.04、压电常数为48 pC/N且机电耦合系数为0.28。随PVDF含量的增加, PVDF/PZNZT复合材料的居里温度降低,维氏硬度有所增加,但仍小于纯PZNZT压电陶瓷的硬度。所得结论显示PVDF/PZNZT压电复合材料的性能可以满足水声、电声及超声换能器等的要求。      

25 MHz ultrasonic transducers with lead- free piezoceramic, 1-3 PZT fiber-epoxy composite, and PVDF polymer active elements

This paper presents the fabrication and characterization of single-element ultrasonic transducers whose active elements are made of lead-free piezoceramic, 1-3 PZT/polymer composite and PVDF film. The lead free piezoelectric KNNLT- LS(K_0.44Na_0.52Li_0.04)(Nb_0.84Ta_0.10S_0.06b)O₃ powders and ceramics were prepared under controlled humidity and oxygen flow rate during sintering. Due to its moderate longitudinal piezoelectric charge coefficient (175 pC/N) and k_t of 0.50, the KNN-LT-LS composition may be a good candidate for highfrequency transducer applications. PZT fibers with 25 μm diameter formed by the viscose suspension spinning process were incorporated into epoxy to fabricate 1-3 composites with the averaged k_t = 0.64 and d₃₃ = 400 pC/N. Using KNN-LS-LT ceramic, 1-3 PZT fiber composite, and PVDF film, 3 different unfocused single element transducers with center frequencies of 25 MHz were fabricated. The acoustic characterization of the transducers demonstrated that wideband and low insertion loss could be obtained employing KNN-LS-LT ceramic. The ?6 dB bandwidth and insertion loss were 70% and ?21 dB, respectively. In comparison, the insertion loss of the ceramic transducer was much smaller than those made with 1-3 composite and PVDF film. This was attributed to closer electrical impedance match to 50 Ω and higher thickness coupling coefficient of the ceramic transducer.