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State-of-the-Art and Perspectives for Electroactive Polymers
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Adil A. Gobouri, Electroactive Polymeric Materials, 2022
Rita Martins, Parastou Sadeghi, Ana P.M. Tavares, Goreti Sales
Ferroelectricity is a property associated with spontaneous electric polarization that occurs in a non-conducting crystal or dielectric material. Polymers with ferroelectric behavior are called ferroelectric polymers, typified by a change in the spontaneous/reversible polarization of the material, under exposure to an external electric field (Bar-Cohen and Anderson, 2019; Kim and Tadokoro, 2007; Qian et al., 2015; Bar-Cohen et al., 2017; Katsouras et al., 2016). Besides ferroelectricity, ferroelectric materials can exhibit a piezoelectric and pyroelectric behavior, in which it can convert mechanical vibrations or thermal fluctuations into electrical energy, respectively (Bar-Cohen et al., 2017). Although ferroelectrics are termed with the prefix ferro which means iron (Fe), these materials do not contain iron atoms in their chemical structure. However, they exhibit analogous characteristics to ferromagnetics, and therefore, the origin of the name ferroelectric (Li and Wang, 2016; Huang and Scott, 2018).
Piezoelectric and Ferroelectric Polymer/Ceramic Composites
Published in Noureddine Ramdani, Polymer and Ceramic Composite Materials, 2019
Recently, ferroelectric materials have attracted much attention due to their large industrial applications, including nonvolatile memory and transducers in sensors and actuators, electrostriction, electric energy storage, electrocaloric cooling, fuel injectors for high efficiency-low emission diesel engines, and ultrasonic rotary inchworm motors with high power and torque densities. These materials are essentially divided into two groups: ceramics and polymer ferroelectrics. Ceramic ferroelectrics demonstrate a highly desirable properties; however, they are brittle and heavy materials. By contrast, the ferroelectric polymers are light, flexible, easy to process and low cost; but, their polar properties are an order of magnitude lower. Among these polymers, PVDF and its composites are a widely utilized class of polymer ferroelectrics showing marked ferroelectric properties due to their b polymorph characteristic [70].
Measurement Techniques for Refractive Index and Second-Order Optical Nonlinearities
Published in Hari Singh Nalwa, Seizo Miyata, Nonlinear Optics of Organic Molecules and Polymers, 2020
Toshiyuki Watanabe, Hari Singh Nalwa, Seizo Miyata
The SHG efficiency of ferroelectric polymers with and without NLO chromophores range between 0.5 and 234 pm/V, depending on the chemical structures and measurement wavelength. Cyano copolymers seem interesting because they offer excellent optical transparency, high Tg, and large SHG efficiency. Likely, materials performance and SHG efficiency can be tailored for polyureas using NLO chromophores with large " values. Ferroelectric polymers are advantageous because they show stable SHG efficiency over an extended period at room temperature.
Enhancement investigations on dielectric and electrical properties of niobium pentoxide (Nb2O5) reinforced poly(vinylidene fluoride) (PVDF)- graphene oxide (GO) nanocomposite films
Published in Journal of Asian Ceramic Societies, 2021
Srikanta Moharana, Ram Naresh Mahaling
Niobium pentoxide (Nb2O5), one of the most important transition metal oxides has immense interest due to their potential applications in gas sensors, catalysts, micro-electronics, and optoelectronic industries [11]. However, the Nb2O5 is an n-type semiconductor with a band gap of about 3.4 eV, low in comparison with other oxide [12]. This niobium pentoxide has several advantageous characteristics including surface area enables for easy modification by intercalation, superficial modification and formation of nanosheets or nanoscrolls [13–15]. Moreover, it is also used as promising doping agent for tailoring nanostructured composites materials for potential applicability in the various fields. Niobium pentoxide is biocompatible as well as it enhances bioactivity and corrosion resistance of the respective nanocomposites [16–18]. In this study, the niobium pentoxide-reinforced graphene-oxide-based polymer nanocomposites have achieved significant increase in dielectric constant with improved conductivity and suppressed loss. Besides, polymers are most normally used as dielectric materials with high mechanical flexibility, good process ability, low cost, and high dielectric strength [19]. Especially, the ferroelectric polymers such as poly(vinylidene fluoride) (PVDF) and its co-polymers poly(vinylidene fluoride co-hexa fluoropropylene) (PVDF-HFP), which is a semi-crystalline thermoplastic polymeric materials with extraordinary high piezo and pyro electric coefficient, better thermal stability, chemical resistance, high dielectric constant (≈10) and high break down strength [20–22].
Medical textiles
Published in Textile Progress, 2020
Piezoelectric polymers become electrically polarised in response to the application of mechanical stress, and the reverse is also true, they will deform on the application of an electric charge. Such responses are rapid and the power requirements to achieve them are small, so this makes them attractive for the generation of electrical signals in sensors, and also as nano-generators in the case of electro-spun versions of the piezoelectric polymer. There are subsets of piezoelectric materials, some of which may demonstrate pyroelectric properties (by responding to changes in temperature by emitting an electric signal) and others, ferroelectric polymers, whose polarisation can be reversed by the application of an electric field. PVDF, Poly (vinylidene fluoride), falls into the last category and it is currently the most-important piezoelectric polymer with the highest electromechanical response over a broad temperature range of all known synthetic polymers; the fact that having been electrospun to yield nanofibres, it can be adjusted to match its surface properties to that of the host environment whilst retaining its piezoelectric properties [173], makes it an attractive material to employ in nanofibrous-textile-based bone bio-implants [174].