High-k polymer nanocomposites have received increased research interest by virtue of integrating high dielectric constant nanofiller with high breakdown strength, flexibility, and ease of processing ...of a matrix. With outstanding anisotropy, high-aspect-ratio nanofillers have proved to be much more efficient enhancers of the dielectric properties of nanocomposites when compared with traditional zero-dimensional (0D) fillers, leading to many dielectric and energy storage applications. This review summarizes the latest research on one-dimensional (1D) and quasi-1D fillers based high-k polymer nanocomposites with the focus on the superiority of 1D or quasi-1D high-k fillers in enhancing the dielectric properties and energy storage capability of polymer nanocomposites. Dielectric anisotropy, which plays a critical role in determining the dielectric properties and energy storage capability of polymer nanocomposites, was highlighted and the experimental methodologies for achieving anisotropic dielectric polymer nanocomposites were reviewed. The fundamental electrical parameters, such as dielectric constant, dielectric nonlinearity, dielectric loss and electrical conduction, and breakdown strength of dielectric polymer composites, are also discussed. Given the recent progress, guidelines for the future development of high-k polymer nanocomposites with dielectric and energy storage applications were proposed.
In this paper, the error of dielectric predictions for moist soils was estimated, regarding the semiempirical mixing dielectric model (SMDM) developed by Dobson , which is a universally recognized ...one, and the generalized refractive mixing dielectric model (GRMDM) recently elaborated by Mironov The analysis is based on the measured dielectric data presented in by Curtis and the papers of Dobson These data cover a broad variety of grain-size distributions observed in 15 soils and the frequency range from 45 MHz to 26.5 GHz, with the temperature being from 20 deg C to 22 deg C. The SMDM was found to deliver predictions with substantially larger error for the soils, whose dielectric data were not used for its development, while the GRMDM ensured dielectric predictions for all the soils analyzed with as small error as the SMDM did in the case of the soils that it was based on. To secure the same convenience in application of the GRMDM, which the SMDM possesses, the spectroscopic parameters of that model were correlated with the clay percentages of the respective soils. As a result, a new mineralogy-based dielectric model was developed. For the moist soils other than those whose dielectric data were used for its development, this model was shown to demonstrate noticeably smaller error of dielectric predictions, with clay percentage being the only input parameter, as compared with the error observed in the case of the SMDM.
Stretchable high‐dielectric‐constant materials are crucial for electronic applications in emerging domains such as wearable computing and soft robotics. While previous efforts have shown promising ...materials architectures in the form of dielectric nano‐/microinclusions embedded in stretchable matrices, the limited mechanical compliance of these materials significantly limits their practical application as soft energy‐harvesting/storage transducers and actuators. Here, a class of liquid metal (LM)–elastomer nanocomposites is presented with elastic and dielectric properties that make them uniquely suited for applications in soft‐matter engineering. In particular, the role of droplet size is examined and it is found that embedding an elastomer with a polydisperse distribution of nanoscale LM inclusions can enhance its electrical permittivity without significantly degrading its elastic compliance, stretchability, or dielectric breakdown strength. In contrast, elastomers embedded with microscale droplets exhibit similar improvements in permittivity but a dramatic reduction in breakdown strength. The unique enabling properties and practicality of LM–elastomer nanocomposites for use in soft machines and electronics is demonstrated through enhancements in performance of a dielectric elastomer actuator and energy‐harvesting transducer.
A liquid‐metal (LM)–elastomer nanocomposite is presented as a stretchable dielectric material. This material's architecture shows a unique combination of enhanced electric permittivity, controlled dielectric breakdown strength, and rubber‐like mechanical properties. These properties enable LM–elastomer nanocomposites to have potentially transformative impact on soft materials actuation, energy storage, and energy harvesting.
In this paper, a complete analysis of the complex dielectric constant of a flexible substrate from the silicon-based polymer- Polydimethylsiloxane (PDMS) is performed, and the obtained results are ...discussed. Two experimental methods are applied in this research. The first Two-resonator method is based on resonance measurements by excitation of two types of TE- and TM-mode cylinder resonators with PDMS disks, ensure an accurate determination of the dielectric constant and dielectric loss tangent in both parallel and perpendicular directions (e.g., <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {par}} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {perp}} </tex-math></inline-formula>). The second method is based on the tight coverage of planar microstrip ring resonators with non- metalized PDMS samples gives reliable information for the equivalent dielectric parameters (e.g., <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {eq}} </tex-math></inline-formula>, tan<inline-formula> <tex-math notation="LaTeX">\delta _{\varepsilon \textit {eq}} </tex-math></inline-formula>). The obtained results show that PDMS substrates have relatively weak but measurable uniaxial anisotropy and well-expressed frequency dependencies of the extracted dielectric parameters in the range 1-40 GHz, namely <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {par}} \sim 2.82 </tex-math></inline-formula>-2.7; <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {perp}} \sim 2.73 </tex-math></inline-formula>-2.52 and <inline-formula> <tex-math notation="LaTeX">\varepsilon _{\textit {eq}} \sim 2.75 </tex-math></inline-formula>-2.64, tan<inline-formula> <tex-math notation="LaTeX">\delta _{\varepsilon eq} \sim 0.017 </tex-math></inline-formula>-0.048. The results are confirmed by several other complementary methods. The considered pair of methods are also applied in the temperature interval-40/<inline-formula> <tex-math notation="LaTeX">+ 70^{\circ }\text{C} </tex-math></inline-formula>; the measured temperature dependencies on the dielectric parameters turn out to be relatively strong. The possible origin of the measured PDMS uniaxial anisotropy has been discussed; in fact, it appears mainly in the temperature range-30/<inline-formula> <tex-math notation="LaTeX">+ 40^{\circ }\text{C} </tex-math></inline-formula>.
Over the past decades, polysiloxane-based dielectric elastomers (DEs) have attracted significant research attention; however, the low dielectric constant and poor breakdown strength of polysiloxane ...limit its application in DEs. In this study, the effect of phenyl side groups on the dielectric properties and unique dielectric relaxation behavior of polymethyl phenyl siloxane (PMPS) was investigated. The dielectric constant of PMPS was slightly improved from 3.45 to 3.60 by introducing appropriate amount of the phenyl side groups into polysiloxane. Moreover, the electrical breakdown strength of PMPS increased from 31.70 to 35.91 kV mm−1. The contribution of the α- and β-relaxations significantly increased the dielectric loss of PMPS. To better understand the effect of the phenyl side groups on these properties, the dielectric relaxation behavior of copolymers with different phenyl contents was studied in detail via broadband dielectric spectroscopy and thermally stimulated depolarization current measurements. This study paves a new path to design and prepare polysiloxane-based soft materials with high dielectric constant and improved electrical breakdown strength.
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•1, Polymethyl phenyl siloxanes random copolymers were synthesized.•2, Breakdown strength of polysiloxanes were significantly improved.•3, The relationship between polymer chains structure and dielectric behavior was revealed.
Dielectric materials with higher energy storage and electromagnetic (EM) energy conversion are in high demand to advance electronic devices, military stealth, and mitigate EM wave pollution. Existing ...dielectric materials for high‐energy‐storage electronics and dielectric loss electromagnetic wave absorbers are studied toward realizing these goals, each aligned with the current global grand challenges. Libraries of dielectric materials with desirable permittivity, dielectric loss, and/or dielectric breakdown strength potentially meeting the device requirements are reviewed here. Regardless, aimed at translating these into energy storage devices, the oft‐encountered shortcomings can be caused by either of two confluences: a) low permittivity, high dielectric loss, and low breakdown strength; b) low permittivity, low dielectric loss, and process complexity. Contextualizing these aspects and the overarching objectives of enabling high‐efficiency energy storage and EM energy conversion, recent advances in by‐design inorganic–organic hybrid materials are reviewed here, with a focus on design approaches, preparation methods, and characterization techniques. In light of their strengths and weaknesses, potential strategies to foster their commercial adoption are critically interrogated.
The underlying principles of dielectric storage and loss mechanism, including their relationships, are discussed. To enable energy storage and electromagnetic energy conversion, design approaches in inorganic–organic hybrid materials are reviewed comprehensively. The preparation and characterization techniques for developing an in‐depth mechanistic understanding of the structure‐property correlations are emphasized. Moreover, the strengths, challenges, and future goals in exploring novel hybrid dielectric materials for future practical applications are critically examined.
Electro-active polymers (EAPs) are emerging as feasible materials to mimic muscle-like actuation. Among EAPs, dielectric elastomer (DE) devices are soft or flexible capacitors, composed of a thin ...elastomeric membrane sandwiched between two compliant electrodes, that are able to transduce electrical to mechanical energy, actuators, and vice versa, generators. Initial studies concentrated mainly on dielectric elastomer actuators (DEAs) and identified the electro-mechanical principles and material requirements for an optimal performance. Those requirements include the need for polymers with high dielectric permittivity and stretchability and low dielectric loss and viscoelastic damping. Hence, attaining elastomeric materials with those features is the focus of current research developments. This review provides a systematic overview of such research, highlighting the advances, challenges and future applications of DEAs.
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•The promising applications of dielectric elastomer actuator composites (DEACs) are highly dependent on the efficacy of filler properties and actuator preparation route.•We present a ...comprehensive summary of recent progress in the development of DEACs based on graphene and its derivatives.•The filler preparation methods, simple & complex filler, and assembly strategies of DEACs overviewed.•Engineering carbonic 2D material as nanofiller can achieve proper electromechanical behavior of actuator at lower percolation threshold.•A key challenge is to increase the performance of DEACs with enhancing dielectric permittivity & electrical breakdown strength, and also maintaining the dielectric loss, loss modulus & elastic modulus.
Dielectric elastomer actuator composites (DEACs) are a class of electroactive polymers that are capable of changing shape or size once applied with an electric field. Such materials have found applications in artificial muscles, micro-robotics and micro air vehicles at industries. The dielectric behavior, mechanical properties, and electric breakdown strength are the main parameters for adjusting actuation behavior of DEACs. This review provides a brief introduction to the effect of 2-dimensional carbonic filler on the percolation threshold during the fabrication of these composites. The design process of graphene nanosheets (GNs) and their derivatives are described based on the filler structure: simple filler and complex filler. For each group, recent remarkable developments are illustrated and the technical issues demanding further improvement are discussed. In general, graphene-oxide (GO) and reduced-GO (rGO), as commutable GNs, numerous cases of use in DEACs have been reported where these materials were employed for controlling the reduction rate of dielectric breakdown strength, maintaining loss parameter (dielectric loss (ε'') and loss modulus (E'')), increasing electromechanical sensitively (β=dielectric permittivity (ε') / elastic modulus) and improving the state of filler dispersion with interfacial engineering. The current review discusses the latest trends in research development in achieving such graphene-enabled enhancements. A systematic approach has been undertaken to highlight the advancements and challenges of graphene-based DEACs and the key research areas that need immediate attention.
This title is part of UC Press's Voices Revived program, which commemorates University of California Press's mission to seek out and cultivate the brightest minds and give them voice, reach, and ...impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1979.
Dielectric materials are eternal jewels in the view of research due to their strong dissipation ability, low density and higher stability compared to those of magnetic materials. Regarding the ...significance of permittivity to characterize the dielectric properties of dielectrics, an in-depth and systematical investigation of dielectric polarization process has become quite necessary. Updated and critical surveys of the key factors determining permittivity, dielectric polarization in single-component system, dielectric polarization in multi-component system and related polarization relaxation are all highlighted. In addition, the challenges for dielectric polarization and polarization relaxation, the prospects for further exploration in electromagnetic wave absorption are also discussed. In short, this review provides a brief but systematic introduction to dielectric polarization and related polarization relaxation in electromagnetic wave absorption, which motivates further study of dielectric absorbers in microwave absorption field.
•Key factors determining permittivity are discussed.•Dielectric polarizations in single-component system are discussed.•Dielectric polarizations in multi-component system are discussed.•Related polarization relaxations are also highlighted.•The prospects for further exploration in electromagnetic wave absorption are proposed.
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