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Piezoresponse Force Microscopy and Electrochemical Strain Microscopy
Published in Cai Shen, Atomic Force Microscopy for Energy Research, 2022
Although the PFM/ESM configuration is designed for ferroelectric studies in the beginning, the subsequent developments and applications have clearly demonstrated that this technique can be broadly used to study multiple physical properties with E-S coupling behavior, such as the piezoelectricity, ferroelectricity, solid state electrochemistry, electrostriction, and flexoelectricity.2,12–14,23,28,45,63–65 Despite the extensive applications in diverse research topics, PFM/ESM in general provides three fundamental functions in these measurements, including the E-S coupling detection, surface domain characterization and manipulation, as well as the voltage spectroscopy measurement. With these basic functions of the PFM/ESM, a wealth of physical properties behind the E-S coupling can be investigated, such as the domain wall growth kinetics, ferroelectric polarization dynamics, electrochemical activity, and even nanomechanics.66–68 In this section, we will discuss the fundamental functions of the PFM/ESM, and the specific studies of material properties by using PFM/ESM will be introduced in other chapters of this book.
A Review of the Gradient and Nonlocal Theories of Electrothermoelastic Polarized Media
Published in Olha Hrytsyna, Vasyl Kondrat, Local Gradient Theory for Dielectrics, 2019
Zholudev (1966) was the first to carry out the laboratory studies of the flexoelectric effect in solid crystalline materials. Bursian and Trunov (1974) observed the flexoelectric phenomena during the bending of crystal plates. Catalan et al. (2004, 2005) investigated the effect of flexoelectricity on the dielectric characteristics of inhomogeneously deformed thin films. Dumitrică et al. (2002) studied the normal polarization in carbon nanoshells due to the bending deformations. Ma and Cross (2001a, 2001b, 2003) investigated the connection between an elastic strain gradient and electric polarization in various ceramic materials.
Comprehensive Reviews on the Computational Micromechanical Models for Rubber-Graphene Composites
Published in Titash Mondal, Anil K. Bhowmick, Graphene-Rubber Nanocomposites, 2023
Kishor Balasaheb Shingare, Soumyadeep Mondal, Susmita Naskar
Alfonso et al. (2016) studied Halpin–Tsai (HT) model and its various dependent parameters in particulate composites. Naskar and his coauthors (Naskar, Mukhopadhyay, and Sriramula 2018; Naskar et al. 2017) reported a probabilistic micromechanical analysis and presented a novel concept of stochastic representative volume element (SRVE). Shingare and Kundalwal (2020) and Shingare, Gupta, and Kundalwal (2020) investigated the electromechanical response of graphene-reinforced piezoelectric composite (GRPC) made of piezoelectric graphene sheets embedded in a polymer matrix. They used graphene as a nanofiber in this study and found that size-dependent features including piezoelectricity, flexoelectricity, and surface effect have an impact on the elastic behavior of GRPC nanobeams. They demonstrated that these effects cannot be ignored at the nanoscale. Afterward, Shingare and Naskar (2021) used different analytical and FE models to determine the elastic and piezoelectric properties of GRPC, including two- and three-phase mechanics of materials (MOM), HT, rules of mixture (ROM), and modified ROM models. They also compared their findings with the existing experimental estimates and found these to be in excellent agreement. These analytical models were also employed by López Jiménez and Pellegrino (2012) in his hyperelastic composite model for validation of the computational findings. Therefore, in this chapter, we studied the computational micromechanical models using different analytical and FE models to study the elastic behavior of rubber-graphene platelets composites (referred to as “GPL/NR nanocomposites”). In this, ROM and HT models are used to validate the results obtained from FE modeling for the proposed GPL/NR nanocomposites, while Ogden model is used to validate the existing experimental findings.
Torsional vibration of a flexoelectric nanotube with micro-inertia effect
Published in Mechanics of Advanced Materials and Structures, 2023
O. Hrytsyna, J. Sladek, V. Sladek, Q. Deng, M. Hrytsyna
Piezoelectric materials are frequantly utilized in macro- and/or micro/nano-electromechanical systems (MEMS/NEMS) [1]. Recently, the flexoelectric effect has been started to be utilized too. The flexoelectricity describes the coupling between the gradient of a mechanical strain and the electric polarization. Piezoelectric and flexoelectric material properties play an important role in polarized elastic structures at the nanoscale [2–5]. Piezoelectricity describes the electromechanical coupling between the electric polarization and a uniform strain. Piezoelectric effect is absent in centrosymmetric materials. In such materials only direct and converse flexoelectric effects can contribute to the electromechanical coupling phenomena. The ability to transform the mechanical strain gradient to electric polarization is known as the direct flexoelectric effect (the mechanical-to-electrical energy transformation). The converse flexoelectricity is the phenomenon of induction of mechanical stresses and deformations by the electric field gradient (the electrical-to-mechanical energy transformation). Contrary to the piezoelectricity, the flexoelectricity might exist in crystals of any symmetry (including the centrosymmetric materials).
Bending, free vibration and buckling analyses of AFG flexoelectric nanobeams based on the strain gradient theory
Published in Mechanics of Advanced Materials and Structures, 2022
Xie Zhao, Shijie Zheng, Zongjun Li
Electromechanical coupling mechanisms, the interaction between electrical variables and mechanical variables, plays a key role in the application of microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) [1]. Particularly, the electrostatically, thermally and piezoelectrically actuated devices have been widely investigated to promote the developments of MEMS and NEMS [2]. As the most widely known and explored electromechanical coupling property, piezoelectricity represents the linear coupling of electric polarization and uniform strain, and only exists in noncentrosymmetric dielectric materials [3]. Different from piezoelectricity, flexoelectricity reflects the interaction between the strain gradient and the induced electric polarization. Furthermore, flexoelectricity places no restriction on structural symmetry due to the fact that nonuniform strain locally breaks inversion symmetry. In fact, owing to the flexoelectricity is negligibly small on the conventional scale, the flexoelectricity has not caused widespread attention over a long period in the past. However, flexoelectricity becomes non-negligible and dominant when the characteristic sizes of structures decrease to nanoscale [4–6]. Thus, it is of great necessary to get a more thorough and comprehensive understanding of the flexoelectric effect on nanoscale dielectrics.
On size-dependent wave propagation of flexoelectric nanoshells interacted with internal moving fluid flow
Published in Waves in Random and Complex Media, 2022
Amir-Reza Asghari Ardalani, Ahad Amiri, Roohollah Talebitooti
In 1981, Indenbom et al. [27,28] represented the concept of flexoelectricity. A few years later, Tagantsev and Fiziki studied the difference between piezoelectricity and flexoelectricity and mentioned the importance of flexoelectric effect especially at nanoscales and in high-stiffness materials like ferroelectrics [29,30]. Flexoelectricity is a property of the material that describes the coupling between electric field polarization and strain gradient (direct effect) and coupling between induced stress and applied electric field gradients (converse effect). Indeed, when materials are exposed to heterogeneous deformations, the flexoelectric effect can be observed. The flexoelectric effect could be detected in materials of any symmetry, while piezoelectricity, which describes the coupling between polarization and homogeneous strain, is seen only in asymmetric materials. After discovering the concept of flexoelectricity, a number of researchers developed the theory of flexoelectric continuum mechanics by extending the theory of elasticity gradient with nonlocal electrodynamics terms [31]. In recent years, the effect of flexoelectricity on various mechanical problems, including wave propagation problems, static stability and vibration of nanostructures, has been studied by many researchers [32–40]. For example, considering the flexoelectric effect, Zeng et al. [41,42] studied the buckling behavior of the piezoelectric cylindrical nanoshell and analyzed its natural frequencies. Yue et al. [43] represented a new micro-scale Timoshenko beam model by considering flexoelectricity and surface effects and studied the static bending and free vibration of a simply supported piezoelectric nanobeam. Moreover, Masoumi et al. [44] conducted a research study to explore the exact influences of flexoelectricity on wave dispersion response of piezoelectric nanobeams.