Dielectric Response of Glass-forming Liquids in the Nonlinear Regime PDF Download
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Author: Subarna Samanta
Publisher:
ISBN:
Category : Dielectric relaxation
Languages : en
Pages : 178
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Book Description
Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be slaved to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein beta-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the electro-optical Kerr effect. A model was discussed which quantitatively captures the observed magnitudes and time dependencies of the NDE. Asymmetry in these rise and decay times was demonstrated as a consequence of the quadratic field dependence of the entropy change. It was demonstrated that the high bias field modifies the polarization response to the field, even including the zero field limit.
Author: Subarna Samanta
Publisher:
ISBN:
Category : Dielectric relaxation
Languages : en
Pages : 178
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Book Description
Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be slaved to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein beta-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the electro-optical Kerr effect. A model was discussed which quantitatively captures the observed magnitudes and time dependencies of the NDE. Asymmetry in these rise and decay times was demonstrated as a consequence of the quadratic field dependence of the entropy change. It was demonstrated that the high bias field modifies the polarization response to the field, even including the zero field limit.
Author: Ranko Richert
Publisher: Springer
ISBN: 331977574X
Category : Science
Languages : en
Pages : 377
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Book Description
This book introduces the ideas and concepts of nonlinear dielectric spectroscopy, outlines its history, and provides insight into the present state of the art of the experimental technology and understanding of nonlinear dielectric effects. Emphasis is on what can be learned from nonlinear experiments that could not be derived from the linear counterparts. The book explains that nonlinear dielectric spectroscopy can be used as a tool to measure structural recovery or physical aging, as well as connections between dynamics and thermodynamic variables such as enthalpy and entropy. Supercooled liquids in their viscous regime are ideal candidates for investigating nonlinear effects, because they are particularly sensitive to changes in temperature, and thus also to changes in the electric field. Other interesting materials covered are plastic crystals and complex liquids near criticality. The book also points out that, compared with other techniques such as mechanical shear experiments, the nonlinear regime of dielectric spectroscopy is special in the sense that the energies involved always remain small compared with thermal energies. To demonstrate this, nonlinear features of mechanical experiments are discussed. Theoretical approaches to nonlinear effects are particularly complicated because the tools available for the linear regime no longer apply. As a result, there is no single generally accepted theory to nonlinear dielectric responses of real liquids. Various approaches to nonlinear dielectric features have been reported, and the different aspects are communicated in several chapters. The book communicates recent progress most effectively through individual contributions from specialists in their respective fields. Chapter 'Third and Fifth Harmonic Responses in Viscous Liquids' is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.
Author: George Floudas
Publisher: Springer Science & Business Media
ISBN: 3642049028
Category : Technology & Engineering
Languages : en
Pages : 183
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Book Description
Pressure is one of the essential thermodynamic variables that, due to some former experimental difficulties, was long known as the “forgotten variable.” But this has changed over the last decade. This book includes the most essential first experiments from the 1960's and reviews the progress made in understanding glass formation with the application of pressure in the last ten years. The systems include amorphous polymers and glass-forming liquids, polypeptides and polymer blends. The thermodynamics of these systems, the relation of the structural relaxation to the chemical specificity, and their present and future potential applications are discussed in detail. The book provides (a) an overview of systems exhibiting glassy behavior in relation to their molecular structure and provides readers with the current state of knowledge on the liquid-to-glass transformation, (b) emphasizes the relation between thermodynamic state and dynamic response and (c) shows that the information on the pressure effects on dynamics can be employed in the design of materials for particular applications. It is meant to serve as an advanced introductory book for scientists and graduate students working or planning to work with dynamics. Several scientific papers dealing with the effects of pressure on dynamics have appeared in leading journals in the fields of physics in the last ten years. The book provides researchers and students new to the field with an overview of the knowledge that has been gained in a coherent and comprehensive way.
Author: Sylwester J. Rzoska
Publisher: Springer Science & Business Media
ISBN: 9781402022609
Category : Science
Languages : en
Pages : 412
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Book Description
Proceedings of the NATO ARW on Nonlinear Dielectric Phenomena in Complex Liquids, Jaszowiec-Ustron, Poland, 10-14 May 2003
Author: Sylwester J. Rzoska
Publisher: Springer Science & Business Media
ISBN: 1402027044
Category : Science
Languages : en
Pages : 395
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Book Description
Complex liquids constitute a basic element in modern materials science; their significant features include self-assembly, mesoscale structures, complex dynamics, unusual phases and enormous sensitivity to perturbations. Understanding their nature and properties are a great challenge to modern materials science that demands novel approaches. This book focuses on nonlinear dielectric phenomena, particularly on nonlinear dielectric spectroscopy (NDS), which may be considered a possible successor to broadband dielectric spectroscopy (BDS). NDS phenomena directly coupled to mesoscale heterogeneity fluctuations, so information obtained in this way is basically complementary to BDS tests. The book also discusses the application of NDS in a set of complex liquid systems: glassy liquids, liquid crystals, liquids with critical point phenomena, and bio-relevant liquids. The complementary application of NDS and BDS may allow the discovery of universal patterns for the whole category of complex liquids. Written by specialists in the field of nonlinear dielectric studies, theoreticians and experimentalists, ranging from solid state physics to biophysics, the book is organized so that it can serve as a basic textbook for a non-experienced reader.
Author: Zbigniew Dendzik
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Matthew Almar Miller
Publisher:
ISBN:
Category : Glass transition temperature
Languages : en
Pages : 290
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Book Description
Author: Yuri P. Kalmykov
Publisher: Springer
ISBN: 9400750129
Category : Science
Languages : en
Pages : 206
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Book Description
This volume considers experimental and theoretical dielectric studies of the structure and dynamics of complex systems. Complex systems constitute an almost universal class of materials including associated liquids, polymers, biomolecules, colloids, porous materials, doped ferroelectric crystals, nanomaterials, etc. These systems are characterized by a new "mesoscopic" length scale, intermediate between molecular and macroscopic. The mesoscopic structures of complex systems typically arise from fluctuations or competing interactions and exhibit a rich variety of static and dynamic behaviour. This growing field is interdisciplinary; it complements solid state and statistical physics, and overlaps considerably with chemistry, chemical engineering, materials science, and biology. A common theme in complex systems is that while such materials are disordered on the molecular scale and homogeneous on the macroscopic scale, they usually possess a certain degree of order on an intermediate, or mesoscopic, scale due to the delicate balance of interaction and thermal effects. In the present Volume it is shown how the dielectric spectroscopy studies of complex systems can be applied to determine both their structures and dynamics.
Author: Robert L. Leheny
Publisher:
ISBN:
Category : Boron compounds
Languages : en
Pages : 80
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Book Description
Author: Kristine Niss
Publisher:
ISBN:
Category :
Languages : en
Pages : 140
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Book Description
