Atomic Force Microscopic Study of Piezoelectric Polymers
Atomic Force Microscopic Study of Piezoelectric Polymers
复制标题
压电聚合物的原子力显微镜研究
DOI：
10.1007/978-3-540-85049-6_6
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Hong Liang
中科院分区：
文献类型：
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作者：
Hyungoo Lee;Ke Wang;T. Jee;Hong Liang
材料在原子力显微镜（AFM）分析中起着重要的作用。特别是活性材料，由于它们的性质而提出了令人感兴趣的挑战。活性材料具有由于通过应力、温度、磁场或电场的能量振动而改变的性质或行为。在这一章中，我们讨论了使用AFM表征的压电材料的唯一性。压电现象最早发现于1756年[1]。1880年报道了用于压电的材料[2，3]。迄今为止，压电效应已广泛用于工业和民用应用，例如换能器、传感器、致动器、发电机、压电马达和燃料电池等[4-7]。许多材料都具有压电特性，表23 - 1列出了常见的材料。如图所示，这些材料为单晶多晶聚合物形式。在表23.1所列的材料中，聚偏二氟乙烯（PVDF）是一种独特的聚合物，具有高高温和压电性能。PVDF具有广泛的工程应用[5-8]。除了高压电系数之外，诸如柔性、生物相容性、重量轻以及低声学和机械阻抗的优点使得PVDF成为生物和MEMS（微机电系统）应用的有利材料。与压电陶瓷相比，PVDF具有更高的电压灵敏度和声阻抗更低[12]。作为半结晶聚合物，PVDF具有五种晶型，α、β、γ、δ和ε。其中，后四种晶体结构具有永久偶极矩。与单个分子相关的偶极子在晶胞中彼此平行;因此，整个PVDF表现出非零偶极矩。β相表现出最强的压电、热电和铁电性质。在α相中，分子偶极子在每个晶胞中是反平行的，导致存在非净偶极子。极性相可以通过不同的工艺从非极性α相获得，例如施加张应力（α相→ β相）[13，14]，在外部电场下极化（α相→ β和δ相）
Materials play an important role in atomic force microscopic (AFM) analysis. Active materials, in particular, present interesting challenges due to their nature. Active materials possess properties or behaviors that change due to the vibration of energy through stress, temperature, magnetic, or electrical fields. In this chapter, we discuss the uniqueness of piezoelectric materials characterized using the AFM. Piezoelectricity was firstly discovered in 1756 [1]. Materials made for piezoelectricity were reported in 1880 [2, 3]. To date, piezoelectric effects have been widely used in industrial and civilian applications, such as, transducers, sensors, actuators, power generators, piezo motors, and fuel cells, among others [4–7]. Many materials have piezoelectric properties; common ones are listed in Table 23.1. As seen here, these materials are in single crystal polycrystal, polymeric form. Among the materials listed in Table 23.1, poly (vinylidene fluoride)(PVDF) is a unique polymer that has high pyro-and piezoelectric properties. PVDF has wide engineering applications [5–8]. Besides the high piezoelectric coefficient, advantages such as flexibility, bio-compatibility, lightness, and low acoustic and mechanical impedance make PVDF a favorable material for bio-and MEMS (microelectromechanical systems) applications. Compared to piezoelectric ceramics, PVDF has higher voltage sensitivity and lower acoustic impedance [12]. As a semicrystalline polymer, PVDF has five crystallographic forms, α, β, γ, δ, and ε. Of those, the latter four crystalline structures possess permanent dipole moment. The dipoles associated with individual molecules are parallel to each other in the unit cell; as a result, overall PVDF exhibits non-zero dipole moment. The β phase exhibits the strongest piezo-, pyro-, and ferroelectric properties. In the α phase, the molecular dipoles are antiparallel in each unit cell resulting in no-net dipole present. The polar phases can be obtained from the nonpolar α phase by different processes such as applying tensile stress (α phase→ β phase)[13, 14], poling under external electric fields (α phase→ β and δ phase)