【作者】 黄世峰；

【导师】 程新；

【作者基本信息】 武汉理工大学 ， 材料学， 2005， 博士

【摘要】 水泥基压电复合材料可有效解决传统智能材料与混凝土母体结构材料之间的相容性问题,它不但具有感知功能,而且具有驱动功能,其制备工艺简单,造价低,非常适合于土木工程领域中智能材料的发展需要,因此,研究与开发该类压电复合材料对于推动各类土木工程结构向智能化方向发展有着广泛的工程应用意义和学术价值。 本文采用压制成型法和切割-填充法分别制备了0-3型和1-3型水泥基压电复合材料,重点研究了其压电性能和介电性能,并初步进行了水泥基压电复合材料的应用研究。 研究了极化条件对0-3型水泥基压电复合材料压电性能的影响,结果表明,对硫铝酸盐水泥基压电复合材料来说,最佳极化工艺参数为:极化电场强度为4kV/mm;极化时间为30min;极化温度应在80^C～100℃之间。 系统研究了压电陶瓷含量、粒度和水泥基体对0-3型水泥基压电复合材料压电性能和介电性能的影响规律,结果表明,随着PLN含量的增加,压电应变常数d₃3和压电电压常数g₃3、介电常数ε_r和介电损耗tgδ、机电耦合系数K_p和K_t、剩余极化强度P_r和矫顽电场强度E_c均增大,而机械品质因数Q_m则在19～50之间波动。只有当PLN含量超过70%时,水泥基压电复合材料才显示出较好的压电性能;随着PLN粒度的增大,压电常数d₃3和g₃3、机电耦合系数K_p和K_t与剩余极化强度P_r和矫顽电场强度E_c均随之增大。当PLN粒度大于1001μm时,d₃3和g₃3值几乎不受PLN粒度的影响;以硫铝酸盐水泥为基体的压电复合材料的压电性能明显高于以普通硅酸盐水泥为基体的压电复合材料的压电性能,而介电性能则恰恰相反,这主要是由于硫铝酸盐水泥无论是早期的力学性能还是后期的力学性能均优于普通硅酸盐水泥的,与陶瓷颗粒的结合更为致密的缘故。在PLN陶瓷含量相同的条件下,前者的K_p和K_t值随PLN含量的增加均呈增大趋势,而后者的K_p和K_t值则呈减少趋势,且波动较大;随着频率的增大,两种不同基体的压电复合材料的极化机制基本相同,即在低频段,均以界面极化为主,高频时呈现良好的介电频率稳定性。 介频谱和介温谱分析结果表明,在40～100kHz频率范围内,0-3型水泥基压电复合材料的介电常数均随频率的增大而迅速降低,这主要受水泥基体内的各种极化和复合材料中的界面极化所影响。高频时,介电常数变化较小,损耗较低,表明水泥基压电复合材料的高频稳定性较好;在-40^C～150℃之间,水更多还原

【Abstract】 Cement-based piezoelectric composites can overcome the deficiency which the traditional piezoelectric materials have bad compatibility with civil engineering’s main structural material—concrete. It not only has sensing function, but also actuating property, which is very suitable for application in civil engineering fields. Therefore, research and development of the cement-based piezoelectric composite play an extremely important role in advancing all kinds of civil engineering structure to be intelligent.0-3 cement-based piezoelectric composites and 1-3 cement-based piezoelectric composites were fabricated by compressing technique and cut-filling process, respectively. The piezoelectric properties and dielectric properties of two kinds of composites were studied in detail, and its applications were investigated.The dependences of piezoelectric properties of composites on poling conditions were studied. The results show that for the 0-3 sulphoaluminate cement-based piezoelectric composites, the optimum poling field E, poling time t and poling temperature Tare 4.0kV/mm, 30min and 80℃¹00℃, respectively.The influence of piezoelectric ceramic content, particle size and cement matrix on the 0-3 cement-based piezoelectric composites was researched in detail. The results show that with increasing the PLN content, piezoelectric strain factor d₃₃, piezoelectric voltage factor g33, dielectric constant ε_r and dielectric loss tgδ, electromechanical coupling coefficient K_p and K_t, remanent polarization P_r and coercive field E_c increase, but mechanical quality Q_m fluctuate between 19 and 50. Only when PLN content is larger than 70%, can the cement-based piezoelectric composites show good piezoelectric properties. With increasing the PLN particle size, the d₃₃, g33, K_p, K_t, P_r and E_c all increase. When PLN particle size is larger than 100 urn, the value of d₃₃ and g33 is nearly independent of the PLN particle size. The piezoelectric properties of the composites made from sulphoaluminate cement are superior than that of the piezoelectric composites made from Portland cement, which is just contrary to the dielectric properties. This is attributed to that the sulphoaluminate cement has better early and late mechanical properties and better combination with ceramic particles than Portland cement. Under the samecondition, for the former, K? and Kt increase with increasing PLN ceramic content, but for the latter, Kp and Kt decrease and fluctuate sharply. With increase of the frequency, the polarization mechanism of two different matrix composites is nearly the same, that is, at the low frequency, the interface polarization is dominant. At the high frequency, it shows good dielectric-frequency stability.From relation between dielectric constant and frequency, temperature, it is obtained that the dielectric constant of 0-3 cement-based piezoelectric composites decreases sharply with the frequency increasing, which is mainly due to various polarization in the cement matrix and interface polarization in the composite. At high frequency, the dielectric constant and dielectric loss change slightly, which means that the cement-based piezoelectric composites have good high frequency stability. In the temperature range between -40°Cand 150°C, the 0-3 cement-based piezoelectric composites shows excellent dielectric- temperature stability.Influences of cement hydration ages and humidity on the piezoelectric properties and dielectric properties of the 0-3 cement-based piezoelectric composites were studied. The results indicate that the piezoelectric properties of the cement based piezoelectric composites are very different from that of the piezoelectric ceramics and polymer/ceramic piezoelectric composites. For the latter, the piezoelectric properties decrease with the prolonging of time, while that of the cement based piezoelectric composite are improved with increasing the cement hydration age. When the cement hydration age exceeds a certain value, J33 tended to be a constant. The value of t/33 increases slightly with increase of the environmental humidity below 60%, while sharply increases with increase of humidity above 60%. The effect of environmental humidity on dielectric constant of the composite is mainly ascribed to change of water absorbed. Increasing of water absorbed improve ionic mobility and polarizability in interface zone, which leads to the remarkable increase of composites dielectric constant. The contribution of water to the polarization is mainly at low frequency, and conductive loss is dominant in dielectric loss.With increasing volume fraction of PMN, the c/33, Kp, Kt, ex, Pr and Ec value of 1-3 cement-based piezoelectric composites increase, but g33 value reduces. Compared with g33 value of PMN, the #33 value of the composite is much bigger, which greatly improve sensing property of the composites. At lower and higherfrequencies, the dielectric constant and dissipation factor change steadily, which exhibit good dielectric-frequency stability. The temperature has little effect on the dielectric constant in the temperature range between -30 °C and 150°C, which shows that 1-3 cement-based piezoelectric composite has good dielectric -temperature stability.The laws that the properties of the 1 -3 cement-based piezoelectric composite vary with ratio of width to thickness（w/t） of PMN ceramic rod were investigated. The results show that the J33, Kp, Ku Qm, er, tgS and acoustic impedance Z value of 1-3 cement-based piezoelectric composites decrease with increasing w/t of PMN ceramic rod, but the ￡33 value is nearly independent of w/t of PMN ceramic rod. When the volume fraction of PMN is 22.72%, the acoustic impedance Z value similar to that of the concrete can be obtained by adjusting w/t of PMN ceramic rod, which can effectively solve the mismatch problem of intelligent materials and concrete structure.According to the feature of cement-based piezoelectric composites, a date acquisition system suitable for the composites was designed, and the research of its application was carried out. The results show that 0-3 and 1-3 cement-based piezoelectric composites have good mechano-electric effect, that is, the voltage is produced in two kinds composites under compressive stress, which increases or decreases as the load increases or decrease. This indicates that cement-based piezoelectric composites are suitable for health monitoring of structures in the civil engineering.更多还原