Author: Xin Chen Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The objective of this research aims at developing dielectric polymers for improved performance in applications of energy storage, electrocaloric cooling, and electro-actuators. In dielectrics for electric energy storage, dielectric constant, dielectric loss, electrical breakdown strength, charge-discharge efficiency (loss at high electric fields), and operation temperature are the key parameters. Compared with inorganic counterpart, dielectric polymers possess low dielectric loss, low cost, and high breakdown strength. Biaxially oriented polypropylene (BOPP), the state of art dielectric polymer, possesses high breakdown strength (Eb > 600 MV/m) and low dielectric loss (0.02%).. However, the low dielectric constant (K = 2.2) limits the energy density of BOPP capacitors to 2 J/cm3, since the energy density of capacitors Ue = 1/2 K[epsilon]0E2, where [epsilon]0 is the vacuum permittivity. The low working temperature ( 80 oC) of BOPP capacitors also limits their applications and often requires additional cooling loops to maintain safe operation. Hence, recent efforts on new high-performance dielectric polymers focus on high glass transition temperature polymers (Tg 200 oC), for example, how to improve the performance of polyimide (PI) and polyetherimide (PEI). Polymer nanocomposites have been investigated for decades in raising K and Ue. However, the traditional approach of adding high dielectric constant (K 1000) inorganic nanomaterials, which usually needs the fillers to be 15 vol%, has achieved limited success. The large dielectric contrast between the nanofillers and polymer matrix results in intensification of local electric fields in the polymer matrix, leading to a large reduction of the dielectric breakdown strength in polymer composites with high-volume loading of nanofillers. In recent years, Zhang's group discovered and developed a class of dilute nanocomposites. For example, it has been shown that in polyetherimide (PEI) (K~3.2), very low volume loading ( 0.5 vol%) of nanofillers can lead to more than 50% increase in the dielectric constant K while retaining the high breakdown strength and low dielectric loss. The enhancement of dielectric constant does not depend on the dielectric constant of the fillers, but depends on the geometry size of the fillers, which suggests a strong interfacial effect. In this thesis, I will present the in-depth study on the change of polymer morphologies in the presence of ultra-low nanoparticles. The studies will focus on 1) the influence of nanoparticle surface, 2) solvents induced change of polymer morphologies, and 3) in-situ structural analysis of polymer matrix around nanoparticle surface. The thesis also studied the topological effect of nanofillers in the dilute nanocomposites. The results show that 1-D nanofillers (nanorods) at ultralow volume loading ( 1 vol%) generate larger dielectric enhancement of the dielectric response of PEI (from 3.2 to 6.1), compared with 0-D nanofillers (nanoparticles). Different from a spherical shell interface nano-topology of 0-D nanofillers, the cylindrical shell nanostructures generated by 1-D nanofillers are much more efficient in raising the dipolar response in terms of extending the high K in the interfacial region and reducing the influence of low K polymer regions. One driving force for the dielectric enhancement in the dilute nanocomposites is the increased local free-volumes. In this thesis, the approach of polymer blending will also be used control and tailor the free-volumes in high Tg polymers. It was observed that the chain packing in the blends can be tuned by the electrostatic interactions between polymer chains. Consequently, by properly matching the two polymers in the blends, one can achieve enhanced breakdown strength or enhanced dielectric constant. PVDF based ferroelectric polymers have been used for electromechanical (EM) energy conversion applications. On the other hand, there is a great need to improve the EM performance of ferroelectric polymers (due to their low EM performance compared with the inorganic counterpart). This thesis studied "defect modifications" of the relaxor ferroelectric P(VDF-TrFE-CFE) terpolymers and show that small amount of FA (fluorinated alkynes) units ( 2 mol%) in the relaxor polymers can effectively suppress the polarizations which do not contribute much to the EM response while enhancing the polarizations which have a strong EM coupling. As a result, the FA modified terpolymers exhibit marked enhancement of EM responses at low electric fields (
Author: Tian Zhang Publisher: ISBN: Category : Languages : en Pages :
Book Description
The objective of my research is to develop energy storage device and electrocaloric cooling device based on dielectric materials. The first part of research work is to develop energy storage capacitor with high energy density by nanocomposite approach based on dipolar polymers. The second part of my research work is to develop electrocaloric effect (ECE) based cooling device.Dielectric constant, dielectric breakdown strength, dielectric loss (at high voltage application, conduction loss is also critical), and operating temperature are critical parameters in dielectric materials and their applications. This thesis investigates innovative approaches to enhance these properties of polymer-based dielectrics.Dielectric polymers are widely used in modern electronics due to the low loss and high breakdown strength. The state-of-art material is biaxially oriented polypropylene (BOPP) which has high breakdown strength (>700 MV/m) and low dielectric loss (0.02%). However, it is limited by its low energy density (2 J/cm3) due to the low dielectric constant (k~2.2) and low working temperature (80 C). In order to raise the dielectric constant K of polymer-based dielectrics and hence improve the energy density, nanocomposites in which high volume loading ( 15 vol%) of high dielectric constant nanofillers (K 1000) is added to a polymer matrix have been widely studied. However, the large dielectric contrast between the nanofillers and polymer matrix and high volume loading of nanofillers result in intensification of local electric fields in the polymer matrix, leading to a large reduction of the dielectric breakdown strength.Recently, Dr. Y Thakur at our group discovered that in dipolar polymer polyetherimide (PEI) (k~3.2), very low volume loading ( 0.5 vol%) of nanofillers can lead to more than 50% increase in the dielectric constant K and remain high breakdown strength. This thesis investigates whether such an approach can be applied to other dipolar polymers with higher dielectric constant, such as polyimide (PI) (k~3.5) and poly (ether methyl ether urea) (PEMEU) (k~4). The results reveal that the nanocomposites based on these amorphous polymers also have large enhancement of dielectric constant. However, the breakdown strength in these nanocomposites cannot be further improved. Moreover, the presence of nanofillers in amorphous polymers does not reduce the conduction loss at high fields, and hence do not enhance the breakdown strength and do not generate a large improvement in the high temperature performance. I investigated semi-crystal polymer poly (arylene ether urea) (PEEU) and discovered that PEEU nanocomposite with very low volume loading (~ 0.2 vol%) of alumina nanoparticles can significantly enhance the energy density, charge/discharge efficiency and breakdown strength at high temperature. Specifically, we show that PEEU nanocomposite with 0.2 vol% of 20 nm size alumina nanofillers increases both the dielectric constant K and breakdown field E over a broad temperature range to 150 oC. The dielectric constant K is raised from K = 4.7 of the base PEEU to 7.4. At 150 oC, the nanocomposite films exhibit a breakdown strength of 600 MV/m, increased from 400 MV/m of the base PEEU films. Moreover, nanofiller at such a low loading also significantly reduces the high field conduction loss and, as a result, the PEEU films deliver a discharged Ue of 5 J/cm3 with a high C/D efficiency (> 90%) at 150 oC.I further investigated how the surface modification affect the dielectric constant of nanocomposite. The results show that the dielectric constant enhancement of the nanocomposite with modified surface is reduced. It demonstrates the enhancement of dielectric constant is related to the elastic coupling between polymer matrix and nanoparticles.For nanocomposite approach, the nanofiller dimension is another critical variable. (i) I studied nanocomposite with 1-D nanofiller and found the enhancement is reduced compared with nanocomposites with 0-D nanoparticles. (ii) Poly-p-phenylene benzobisoxazole (PBO) (k~4.5) nanocomposite with 2D nanosheet is also studied (in collaboration with Dr. Cheng Huang of Suzhou University). The results reveal a very large dielectric enhancement. K ~8.7 (loss ~ 1%) was measured for nanocomposites with 1.8 vol% TiO2 nanosheet loading, which is about 2X of the neat PBO. Among all the known polymers, such a high dielectric constant can only be obtained in ferroelectric polymers (such as Polyvinylidene fluoride (PVDF) based polymers). In contrast to PVDF based polymers, the dielectric response of PBO nanocomposites remain linear under high field (200 MV/m). All the above results demonstrates that nanofillers beyond nanoparticles can generate additional variable to enhance the dielectric performance and the dielectric enhancement is determined by the combination of the polymer matrix (structure) and nanofiller (size and dimension).This thesis also investigated another important application of dielectric material, e.g., the electrocaloric effect (ECE) based cooling. The proposed device is based on a counter-rotating disks structure to achieve internal thermal regeneration, thus eliminates the external regenerators and enhances the efficiency. To demonstrate the concept, a commercial multilayer ceramic capacitor (MLCC) was chosen for the EC elements, which generated an EC temperature change of 0.9 K under 200 V. For the EC cooler with two EC rings, which is the minimum required to form a counter-rotating disks device, and at 5 rpm, the device exhibits a temperature lift between the cold and hot ends which is 3X of the EC temperature change of single EC element, demonstrating the concept.
Author: Jun-Wei Zha Publisher: John Wiley & Sons ISBN: 3527351825 Category : Languages : en Pages : 405
Book Description
Provides a complete overview of the state-of-the-art high temperature polymer dielectrics, with a focus on fundamental background and recent advances.
Author: Zhi-Min Dang Publisher: William Andrew ISBN: 0128132167 Category : Technology & Engineering Languages : en Pages : 502
Book Description
Dielectric Polymer Materials for High-Density Energy Storage begins by introducing the fundamentals and basic theories on the dielectric behavior of material. It then discusses key issues on the design and preparation of dielectric polymer materials with strong energy storage properties, including their characterization, properties and manipulation. The latest methods, techniques and applications are explained in detail regarding this rapidly developing area. The book will support the work of academic researchers and graduate students, as well as engineers and materials scientists working in industrial research and development. In addition, it will be highly valuable to those directly involved in the fabrication of capacitors in industry, and to researchers across the areas of materials science, polymer science, materials chemistry, and nanomaterials. Focuses on how to design and prepare dielectric polymer materials with strong energy storage properties Includes new techniques for adjusting the properties of dielectric polymer materials Presents a thorough review of the state-of-the-art in the field of dielectric polymer materials, providing valuable insights into potential avenues of development
Author: Haibo Zhang Publisher: CRC Press ISBN: 1040123988 Category : Science Languages : en Pages : 217
Book Description
Due to growing energy demands, the development of high-energy storage density dielectric materials for energy storage capacitors has become a top priority. Dielectric Materials for Capacitive Energy Storage focuses on the research and application of dielectric materials for energy storage capacitors. It provides a detailed summary of dielectric properties and polarization mechanism of dielectric materials and analyzes several international cases based on the latest research progress. • Explains advantages and development potential of dielectric capacitors. • Discusses energy storage principles of dielectric materials as well as effects of polarization and breakdown mechanisms on energy storage performance. • Summarizes achievements and progress of inorganic and organic dielectric materials as well as multidimensional composites. • Details applications and features international case studies. • Offers unique insights into existing issues and forecasts for future research priorities. With its summary and large-scale analysis of the fields related to dielectric energy storage, this book will benefit scholars, researchers, and advanced students in materials, electrical, chemical, and other areas of engineering working on capacitors and energy storage.
Author: Tatiana Correia Publisher: Springer Science & Business Media ISBN: 364240264X Category : Technology & Engineering Languages : en Pages : 255
Book Description
Since the 1997 Kyoto protocol of reduction of greenhouse gas emissions, the development of novel refrigerators has been a priority within the scientific community. Although magnetocaloric materials are promising candidates, they still need a large magnetic field to induce a giant ΔT as well as powerful and costly magnets. However, in electrocaloric materials (ECMs) a temperature change may be achieved by applying or removing an electric field. Since a giant electrocaloric effect on ferroelectric thin films was reported in Science in 2006, researchers have been inspired to explore such effect in different ferroelectric thin films. This book reviews electrocaloric effects observed in bulk materials as well as recent promising advances in thin films, with special emphasis on the ferroelectric, antiferroelectric and relaxor nature of ECMs. It reports a number of considerations about the future of ECMs as a means of achieving an efficient, ecologically sustainable and low cost refrigerator.
Author: Boxue Du Publisher: BoD – Books on Demand ISBN: 9535131478 Category : Technology & Engineering Languages : en Pages : 152
Book Description
The book gives the reader an overview on electrical properties and applications such as converter transformer, transistor, and energy storage. Besides, this book also presents some recent researches on typical polymer material such as silicon rubber and LDPE, which may provide some clues of advanced polymer properties for both engineers and researches. The author has been a professor at the Department of Electrical Engineering, School of Electrical Engineering and Automation, Tianjin University, China, since 2002. He has been active in polymer insulation research since the 1990s. He is a member of IEEJ, senior member of CSEE, member at several WG in CIGRE, and associate editor of the IEEE Transactions on Dielectrics and Electrical Insulation.
Author: Lenore Rasmussen Publisher: Springer Science & Business Media ISBN: 1461408776 Category : Technology & Engineering Languages : en Pages : 163
Book Description
Electroactivity in Polymeric Materials provides an in-depth view of the theory of electroactivity and explores exactly how and why various electroactive phenomena occur. The book explains the theory behind electroactive bending (including ion-polymer-metal-composites –IPMCs), dielectric elastomers, electroactive contraction, and electroactive contraction-expansion cycles. The book also balances theory with applications – how electroactivity can be used – drawing inspiration from the manmade mechanical world and the natural world around us.
Author: Xiaofan Niu Publisher: ISBN: Category : Languages : en Pages : 104
Book Description
Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 degree Celsius. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP in tactile display is investigated by the prototyping of a large scale refreshable Braille display device. Braille is a critical way for the vision impaired community to learn literacy and improve life quality. Current piezoelectrics-based refreshable Braille display technologies are limited to up to 1 line of Braille text, due to the bulky size of bimorph actuators. Based on the unique actuation feature of BSEP, refreshable Braille display devices up to smartphone-size have been demonstrated by polymer sheet laminates. Dots in the devices can be individually controlled via incorporated field-driven BSEP actuators and Joule heater units. A composite material consisting of silver nanowires (AgNW) embedded in a polymer substrate is brought up as a compliant electrode candidate for BSEP application. The AgNW composite is highly conductive (Rs: 10 Ohm/sq) and remains conductive at strains as high as 140% (Rs:
Author: Vivek Bharti Publisher: Cambridge University Press ISBN: 9781107408890 Category : Technology & Engineering Languages : en Pages : 274
Book Description
Increasing research and development efforts have been dedicated to the field of electroresponsive polymers (ERPs), including the development of materials and devices. In addition to their exceptional physical properties and low manufacturing costs, these materials also show remarkable charge storage and electrical properties. One particular class of these materials is the electroactive polymer (EAP), or artificial muscle - a new type of smart material with a broad range of potential applications such as electromechanical devices, energy storage devices, artificial muscles, air filtration, insulation, etc. This book shows research and commercial advances in the field and highlights the significant industry involvement: 3M is implementing piezomaterials in stethoscopes; Measurement Specialties Inc. highlights a range products employing PVDF sensors and EMFIT Ltd. presents ferroelectrets, in which microporous polymers show a piezoelectric coefficient at the level of ~300 pC/N. Additional topics include: sensors and their applications; polymer actuators and their applications; and polymer dielectrics and charge storage applications.
Author: Xin Chen
Author: Tian Zhang
Author: Jun-Wei Zha
Author: Zhi-Min Dang
Author: Haibo Zhang
Author: Tatiana Correia
Author: Boxue Du
Author: Lenore Rasmussen
Author: Xiaofan Niu
Author: Vivek Bharti