Download or read book Experimental Studies of Flexoelectricity in Polyvinylidene Fluoride PVDF Homopolyner Films written by Hyun Heo and published by . This book was released on 2010 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: The electric polarization induced by the non-uniform deformation, i.e. the direct flexoelectric effect, in polyvinylidene fluoride (PVDF) has been investigated based on a beam bending method in this thesis. The primary goal of my research is to understand the properties of both ferroelectricity and flexoelectricity of PVDF homopolymer films under the unaligned state. Generally speaking, bulk PVDF materials exists in three phase structures, α phase (TGTG'), β phase (TTTT), and γ phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. Only β phase and γ phase possess piezoelectric responses; however the direct flexoelectric effect can exist in any phase. This is because the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric crystalline materials.^In my experimental study, the unaligned PVDF homopolymer films were initially synthesized using solution polymerization process and then characterized by using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the polymer films. My studies have shown that both the effect and the behavior largely depend on the molecular chain configuration of PVDF films. Compared with certain aligned PVDF films, the flexoelectric properties of the unaligned PVDF film could be significantly different. My experimental results also demonstrate that the ferroelectric-like behavior in the unaligned PVDF film might be induced by its spatially distributed space electric charges.^The measured flexoelectric coefficient (μ13) and the piezoelectric coefficient (d13) can also give us valuable information about the property degradation, or aging phenomena, in polymer films and the related polymer devices. Finally I summarize my research and discuss some possible future research topics which could follow my thesis.
Download or read book Flexoelectric and Ferroelectric Properties of Quenched Polyvinylidene Fluoride PVDF Homopolymer Films written by Sankar Thiruvannamalai and published by . This book was released on 2010 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flexoelectric and ferroelectric properties of quenched polyvinylidene fluoride (PVDF) homopolymer films have been investigated in this thesis. It is well known that PVDF homopolymer mainly has three phase structures, alpha phase (TGTG'), beta phase (TTTT), and gamma phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. However, the quenched PVDF homopolymer has different molecular chain conformations, which may render some unique mechanical and electric properties. Quenching is a mechanical process in which PVDF homopolymer is strengthened and hardened. This is done by heating PVDF solution at a certain temperature, where the polymerization cannot be formed, then rapidly cooling the polymer; in annealing process, only in certain local microscopic areas, polymerization can occur to let PVDF monomer molecules aggregate together to form the alpha, beta, and gamma phases.^So the regions between those areas in the polymer have amorphous structures. Thus, the piezoelectric behavior of the quenched PVDF homopolymer might be altered since only beta phase and gamma phase in PVDF possess piezoelectric responses and the volume, in which both beta phase and gamma phase exist, in the quenched polymer is reduced. However, whether the direct flexoelectric effect is influenced or not in the quenched PVDF homopolymer is still unknown. This is because the direct flexoelectric effect can exist in polymers of any phase; the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric phase. In our experimental studies, the quenched PVDF homopolymer films were initially synthesized using solution polymerization process and then were quenched in ice-water. We further characterized our samples by using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM).^The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the quenched polymer films. Our studies have shown that both the effect and the behavior largely depend on the molecular chain configurations of the quenched PVDF films. Our experimental results also demonstrate that the ferroelectric-like behavior in the quenched PVDF film might be induced by its spatially distributed space electric charges. The measured flexoelectric coefficient (mu13) may also give us valuable information about how aging phenomena would be induced in polymer films.
Download or read book Experimental Investigation on Ferroelectric and Flexoelectric Properties of Poly vinylidenefluoride hexafluoropropylene PVDF HFP Copolymer Films written by Ho Joon Lee and published by . This book was released on 2010 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The electric polarization induced by the non-uniform deformation, i.e. the direct flexoelectric effect, in poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) has been investigated. The ferroelectric properties of PVDF-HFP copolymer films were measured. The primary goal of the research in this thesis is to understand the properties of both ferroelectricity and flexoelectricity of PVDF-HFP copolymer films under different circumstances. It is well known that PVDF homo polymer mainly has three phase structures, α phase (TGTG'), β phase (TTTT), and γ phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. Only β phase and γ phase possess piezoelectric responses. The direct flexoelectric effect can exist in any phase. This is because the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric crystalline materials.^However, in PVDF-HFP copolymer, the molecular chain conformations of PVDF are modified by HFP monomers. Although the mixture of two polymers can be regarded as a random amorphous structure, their molecular chain conformations may splay to different directions if a non-uniform deformation is applied to them. Therefore both ferroelectric and flexoelectric properties of PVDF-HFP copolymers might be significantly different from that of PVDF homo polymers. In our experimental studies, the unaligned PVDF-HFP copolymer films were initially synthesized by using the solution polymerization process and then characterized via X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the polymer films.^However, the flexoelectric coefficient of PVDF-HFP copolymers we measured is almost 50% smaller than that of the unaligned PVDF homo films. The experimental results also demonstrate that the ferroelectric-like behavior in PVDF-HFP copolymers under different conditions might be induced by their spatially distributed space electric charges. The measured flexoelectric coefficient (μ13) and the piezoelectric coefficient (d13) can also give us valuable information about the property degradation, or aging phenomena, in polymer films and the related polymer devices.
Download or read book A Study of the Mechanism of Pyroelectricity in Polymer Films written by B. Oh and published by . This book was released on 1975 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study was undertaken of both theoretical and experimental aspects of the phenomenon of pyroelectricity in polymer films, focussing on polyvinylidene fluoride. Four theoretical models were considered in detail: a 'rigid rod' model; a 'perimeter of separation' model; a 'molecular rearrangement' model; and a 'space charge' model. Experimental studies developed some methods which may be useful in obtaining mechanistic information, and also determined that a copolymer of vinylidene fluoride and tetrafluoroethylene had a significantly larger pyroelectric coefficient than polyvinylidene fluoride homopolymer.
Download or read book New Properties and Applications of Polyvinylidene Based Ferroelectric Polymer written by J.L. Wang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There are different kinds of novel properties and applications of polyvinylidene difluoride (PVDF)-based ferroelectric polymer films. Several issues associated with the structure, properties, and applications of PVDF-based ferroelectric polymer films are discussed. The main achievements of the research include high electric tunability of relaxor ferroelectric Langmuir-Blodgett (LB) terpolymer films, the creep process of the domain switching in poly(vinylidene fluoride-trifluoroethylene) ferroelectric thin films, transition from relaxor to ferroelectric-like phase in poly(vinylidene fluoride-trifluoroethylene -chlorofluoroethylene) terpolymer ultrathin films, abnormal polarization switching of relaxor terpolymer films at low temperatures, huge electrocaloric effect in LB ferroelectric polymer thin films, self-polarization in ultrathin LB polymer films, enhanced dielectric and ferroelectric properties in artificial polymer multilayers, and transition of polarization switching from extrinsic to intrinsic in ultrathin PVDF homopolymer films.
Download or read book Investigation of phase Poly vinylidene Fluoride Films Using Small angle X ray Scattering written by and published by . This book was released on 2006 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: Piezoelectric materials undergo a change in polarization in response to mechanical stress. The phenomenon is used in a variety of devices from sonar detectors to actuators. Although most piezo-materials are ceramics, some polymers have been found to display piezoelectric response. Poly (vinylidene fluoride) (PVDF) exhibits the strongest piezoelectric response of any commercially available polymer. The origin of piezoelectricity in PVDF is extensively debated in the literature. Studies have been attempted to understand structure-piezoelectric property relationships. Very little information is available on the morphology observed in PVF2. 2-dimensional small-angle and wide-angle x-ray scattering studies were performed to understand the lamellar morphology of PVDF (beta phase) films. This investigation revealed that there are two populations of lamellae of average spatial orientation. The lamellae are not perpendicular or parallel to the machine direction (MD), implied by the literature. It is found that lamellar plane normals make +/- 42 - 48 degree angle with the MD and that lamellar long period was 80 - 89 Â. The effect of such a lamellar morphology on piezoelectric response and specifically bending piezoelectricity is discussed. It is thought that stress-induced lamellar rotation may play a role in piezoelectric response. Bending piezoelectric response in single films can be explained on the basis of a heterogeneous mesoscale structure. Structural features which need to be incorporated in models of piezoelectricity for PVDF films are discussed.
Download or read book Ferroelectric Polymers written by Hari Singh Nalwa and published by CRC Press. This book was released on 1995-06-20 with total page 904 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work covers the chemistry and physics of polymeric materials and their uses in the fields of electronics, photonics, and biomedical engineering. It discusses the relationship between polymeric supermolecular structures and ferroelectric, piezoelectric and pyroelectric properties.
Download or read book Piezoelectric Nanomaterials for Biomedical Applications written by Gianni Ciofani and published by Springer Science & Business Media. This book was released on 2012-03-31 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoscale structures and materials have been explored in many biological applications because of their novel and impressive physical and chemical properties. Such properties allow remarkable opportunities to study and interact with complex biological processes. This book analyses the state of the art of piezoelectric nanomaterials and introduces their applications in the biomedical field. Despite their impressive potentials, piezoelectric materials have not yet received significant attention for bio-applications. This book shows that the exploitation of piezoelectric nanoparticles in nanomedicine is possible and realistic, and their impressive physical properties can be useful for several applications, ranging from sensors and transducers for the detection of biomolecules to “sensible” substrates for tissue engineering or cell stimulation.
Download or read book Infrared and Raman Spectroscopy of Polymers written by J. L. Koenig and published by iSmithers Rapra Publishing. This book was released on 2001 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vibrational spectroscopy is advantageous as an analytical tool for polymers and comprises two complementary techniques: infrared (IR) and Raman spectroscopy. This report is an absorbing overview of how these methods can be employed to provide information about complex polymeric macromolecules with respect to composition, structure, conformation and intermolecular interactions. The review is supported by several hundred abstracts selected from the Polymer Library giving useful references for further reading.
Download or read book Polymeric Biomaterials Structure and function written by Severian Dumitriu and published by CRC Press. This book was released on 2013 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt: The third edition of a bestseller, this comprehensive reference presents the latest polymer developments and most up-to-date applications of polymeric biomaterials in medicine. Expanded into two volumes, the first volume covers the structure and properties of synthetic and natural polymers as well as bioresorbable hybrid membranes, drug delivery systems, cell bioassay systems, and electrospinning for regenerative medicine. This substantially larger resource includes state-of-the-art research and successful breakthroughs in applications that have occurred in the last ten years.
Download or read book Ferroelectrics written by Mickaël Lallart and published by BoD – Books on Demand. This book was released on 2011-08-23 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferroelectric materials have been and still are widely used in many applications, that have moved from sonar towards breakthrough technologies such as memories or optical devices. This book is a part of a four volume collection (covering material aspects, physical effects, characterization and modeling, and applications) and focuses on the application of ferroelectric devices to innovative systems. In particular, the use of these materials as varying capacitors, gyroscope, acoustics sensors and actuators, microgenerators and memory devices will be exposed, providing an up-to-date review of recent scientific findings and recent advances in the field of ferroelectric devices.
Download or read book Ferroelectric Materials written by Aimé Peláiz-Barranco and published by BoD – Books on Demand. This book was released on 2015-07-29 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferroelectric materials receive great attention from the scientific international community because of the interesting phenomena they exhibit and their multiple applications such as transducers, capacitors, pyroelectric sensors, sonars, random access memories, etc. The demand for ferroelectric materials for technological applications enforced the in-depth research, in addition to the improvement of processing and characterization techniques. This book contains nine chapters and offers the results of several researches covering fabrication, properties, theoretical topics, and phenomena at the nanoscale.
Download or read book Polymer Gels written by Vijay Kumar Thakur and published by Springer. This book was released on 2018-08-07 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses a range of synthesis and characterization techniques that are critical for tailoring and broadening the various aspects of polymer gels, as well as the numerous advantages that polymer gel-based materials offer. It presents a comprehensive collection of chapters on the recent advances and developments in the science and fundamentals of both synthetic and natural polymer-based gels. Topics covered include: synthesis and structure of physically/chemically cross-linked polymer-gels/polymeric nanogels; gel formation through non-covalent cross-linking; molecular design and characterization; polysaccharide-based polymer gels: synthesis, characterization, and properties; modified polysaccharide gels: silica-based polymeric gels as platforms for the delivery of pharmaceuticals; gel-based approaches in genomic and proteomic sciences; emulgels in drug delivery; and organogels. The book provides a cutting-edge resource for researchers and scientists working in various fields involving polymers, biomaterials, bio-nanotechnology and functional materials.
Download or read book Energy Harvesting Properties of Electrospun Nanofibers written by Jian Fang and published by . This book was released on 2019-12-27 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a state-of-the-art review on the applications of electrospun nanofibers for piezoelectric and triboelectric energy harvesting. It comprises eight chapters, covering the basis of electrospinning, nanofibers, piezoelectricity, triboelectricity and the emerging research on the use of nanofibers in energy harvesting devices. The book is a key referencefor graduate students, researchers and scientists in the fields of energy harvesting, sensors or nanofibers, and would benefit industry specialistsinvolvedwithenergy materials and energy conversion technology.
Download or read book Electrospinning Nanofabrication and Applications written by Bin Ding and published by William Andrew. This book was released on 2018-11-12 with total page 832 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrospinning: Nanofabrication and Applications presents an overview of the electrospinning technique, nanofabrication strategies and potential applications. The book begins with an introduction to the fundamentals of electrospinning, discussing fundamental principles of the electrospinning process, controlling parameters, materials and structures. Nanofabrication strategies, including coaxial electrospinning, multi-needle electrospinning, needleless electrospinning, electro-netting, near-field electrospinning, and three-dimensional macrostructure assembling are also covered. Final sections explore the applications of electrospun nanofibers in different fields and future prospects. This is a valuable reference for engineers and materials scientist working with fibrous materials and textiles, as well as researchers in the areas of nanotechnology, electrospinning, nanofibers and textiles. Explores controllable fabrication of electrospun nanomaterials and their multifunctional applications Explains the electrospinning technique as used in nanofabrication and nanofibers Outlines the applications of electrospun nanofibrous materials in tissue engineering, filtration, oil-water separation, water treatment, food technology, supercapacitors, sensors and so on
Download or read book Ferroelectric Liquid Crystals written by R. Blinc and published by CRC Press. This book was released on 1984 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dielectric Properties of Binary Solutions written by Y. Y. Akhadov and published by Elsevier. This book was released on 2013-10-22 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dielectric Properties of Binary Solutions focuses on the investigation of the dielectric properties of solutions, as well as the molecular interactions and mechanisms of molecular processes that occur in liquids. The book first discusses the fundamental formulas describing the dielectric properties of liquids and dielectric data for binary systems of non-aqueous solutions. Topics include permittivity and dielectric dispersion parameters of non-aqueous solutions of organic and inorganic compounds. The text also tackles dielectric data for binary systems of aqueous solutions, including permittivity of aqueous solutions of organic and inorganic compounds and dielectric dispersion parameters of aqueous solutions of organic and inorganic compounds. The tables that show the measurements of static permittivity, limiting high-frequency permittivity, permittivity and dielectric loss, relaxation time, and coefficient of distribution of relaxation times are presented. The manuscript also presents dielectric data in graphical form. The book is a vital reference for readers interested in the dielectric properties of binary solutions.
