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Letteratura scientifica selezionata sul tema "Dynamic dielectric properties"

Autore: Grafiati

Pubblicato: 22 febbraio 2025

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Articoli di riviste sul tema "Dynamic dielectric properties"

Zhuravlev, V. I., e T. M. Usacheva. "Dynamic dielectric properties of butanediols". Moscow University Chemistry Bulletin 65, n. 2 (aprile 2010): 70–74. http://dx.doi.org/10.3103/s0027131410020033.

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Cosby, Tyler, David P. Durkin, Robert A. Mantz e Paul C. Trulove. "Interplay of Local Dynamic Heterogeneity, Mesoscale Aggregate Dynamics, and Transport Properties of Imidazolium Ionic Liquids". ECS Meeting Abstracts MA2022-02, n. 55 (9 ottobre 2022): 2099. http://dx.doi.org/10.1149/ma2022-02552099mtgabs.

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Ion dynamics and charge transport in 1-methyl-3-octylimidazolium ionic liquids with chloride, bromide, tetrafluoroborate, tricyanomethanide, hexafluorophosphate, triflate, tetrachlorodialuminate, bis(trifluoromethylsulfonyl)imide, and heptachlorodialuminate anions are investigated by broadband dielectric spectroscopy, rheology and viscometry. A detailed analysis reveals anion and temperature-dependent separation of characteristic relaxation rates extracted from various representations of the dielectric spectra. The degree of separation is interpreted as an experimental signature of significant heterogeneity of the local ion dynamics associated with the structural glass transition, viscosity, and dc ion conductivity. It is found that the degree of dynamic heterogeneity correlates closely with the strengths of slow dielectric and mechanical relaxations previously attributed to the dynamics of mesoscale solvophobic aggregates. Increasing local dynamic heterogeneity correlates with an increase in the strength of the slow, aggregate dielectric relaxation and a decrease in the strength of the slow, aggregate mechanical relaxation. Accordingly, the local dynamic heterogeneity correlates with an increase in the static dielectric permittivities and a decrease in the contribution of aggregate dynamics to the zero-shear viscosities. These results are presented within a broader framework of current understanding of dynamics in ionic liquids and the interplay of dynamics, solvophobic aggregation, and charge transport in these technologically important systems.

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Saad, A., U. Becker, M. Stockhausen e Y. Barakat. "Notiz: Dynamic Dielectric Properties of Some Alkylamino Ethoxylates". Zeitschrift für Naturforschung A 50, n. 11 (1 novembre 1995): 1083–84. http://dx.doi.org/10.1515/zna-1995-1116.

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Abstract Nine ethoxylated (EO) alkyl amines, (CnH2n + 1) N(EO)x; H(EO)y H, with n = 10 to 16 and p = x + y = 7.6 to 14.5, were studied as pure liquids with respect to their dielectric relax ation behaviour over the frequency range 5 MHz to 36 GHz at 20 °C. The broad and structureless dielectric loss spectrum is similar for all samples. It can be described by a main lower frequency spectral component of Havriliak-Negami type plus two minor, higher frequency Debye type components. The relaxation parameters are reported. Dynamic Dielectric Properties of Some Alkylamino Ethoxylates

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Zakharov, A. V., e L. V. Mirantsev. "Dynamic and dielectric properties of liquid crystals". Physics of the Solid State 45, n. 1 (gennaio 2003): 183–88. http://dx.doi.org/10.1134/1.1537433.

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CUI, LIAN, HAIYING CUI, CHUNMEI WU, GUIHUA YANG, ZELONG HE, YULING WANG e JIXIN CHE. "DYNAMIC PROPERTIES OF DIELECTRIC SUSCEPTIBILITY IN FERROELECTRIC THIN FILMS". Surface Review and Letters 23, n. 03 (3 maggio 2016): 1650010. http://dx.doi.org/10.1142/s0218625x16500104.

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In this paper, frequency, temperature, film thickness, surface effects, and various parameters dependence of dielectric susceptibility is investigated theoretically for ferroelectric thin films by the modified Landau theory under an AC applied field. The dielectric susceptibility versus AC applied field shows butterfly-shaped behavior, and depends strongly on the frequency and amplitude of the field and temperature. Our study shows that the existence of the surface transition layer can depress the dielectric susceptibility of a ferroelectric thin film. These results are well consistent with the phenomena reported in experiments.

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Chakraborty, Sudhangshu. "Frequency-dependent dielectric properties of sodium silicate". Modern Physics Letters B 32, n. 33 (30 novembre 2018): 1850411. http://dx.doi.org/10.1142/s0217984918504110.

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The dielectric properties of sodium silicate (Na2SiO3) (SS) have been investigated in a wide range of frequencies and temperatures. A strong dielectric dispersion is found to exist in low-frequency region. The frequency-dependent dielectric properties of SS follow the universal dynamic response proposed by Jonscher. The measured dielectric data strongly depends on dielectric dispersion and controls the basic relaxation property. However, the parameters that control the frequency-dependent dielectric properties such as coupling of ions or polarizability are found to have peak values at the frozen out condition or critical point.

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Baklanov, Mikhail R., e Karen Maex. "Porous low dielectric constant materials for microelectronics". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 364, n. 1838 (29 novembre 2005): 201–15. http://dx.doi.org/10.1098/rsta.2005.1679.

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Materials with a low dielectric constant are required as interlayer dielectrics for the on-chip interconnection of ultra-large-scale integration devices to provide high speed, low dynamic power dissipation and low cross-talk noise. The selection of chemical compounds with low polarizability and the introduction of porosity result in a reduced dielectric constant. Integration of such materials into microelectronic circuits, however, poses a number of challenges, as the materials must meet strict requirements in terms of properties and reliability. These issues are the subject of the present paper.

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Rabii, Sanaa, Ayoub Lahmidi, Samir Chtita, Mhammed El Kouali, Mohammed Talbi e Abdelkbir Errougui. "Molecular dynamics modelling of the structural, dynamic, and dielectric properties of the {LiF - ethylene carbonate} energy storage system at various temperatures". Journal of the Serbian Chemical Society, n. 00 (2024): 61. http://dx.doi.org/10.2298/jsc240205061r.

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Lithium-ion batteries (LIBs) play a vital role in advancing the hybrid industry, especially in electric vehicles, as clean and sustainable electrochemical energy sources. However, the prevalent use of organic solvents in the liquid electrolytes of these energy storage systems raises environmental concerns. In this study, we investigated the impact of a polar aprotic solvent, Ethylene Carbonate (EC), on the structural, dynamic, and dielectric properties of the LiF electrolyte using molecular dynamics simulations. By employing the CHARMM 36 force field, our goal was to comprehend the various physicochemical phenomena occurring in this electrolytic system across different temperatures within the saturation region. The structural properties were analyzed through the computation of the radial distribution function (RDF) for various pairs, while the dynamic and dielectric behaviors were elucidated by simulating the self-diffusion coefficient (D) and the dielectric constant (?).

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Pascariu, Petronela, Mihaela Homocianu, Loredana Vacareanu e Mihai Asandulesa. "Multi-Functional Materials Based on Cu-Doped TiO2 Ceramic Fibers with Enhanced Pseudocapacitive Performances and Their Dielectric Characteristics". Polymers 14, n. 21 (4 novembre 2022): 4739. http://dx.doi.org/10.3390/polym14214739.

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In this work, pure TiO2 and Cu (0.5, 1, 2%)-doped TiO2 composites prepared by electrospinning technique followed by calcination at 900 °C, and having high pseudocapacitive and dielectric characteristics were reported. These nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, and dynamic water sorption vapor measurements. The structural characterization of these nanostructures highlighted good crystallinity including only the rutile phase. The electrochemical characteristics were investigated by cyclic voltammetry and galvanostatic charge–discharge measurements, which were performed in a KOH electrolyte solution. Among the Cu-doped TiO2 nanostructures that were prepared, the one containing 0.5% Cu exhibited superior electrochemical properties, including high specific gravimetric capacitance of 1183 F·g−1, specific capacitance of 664 F·g−1, energy density of 45.20 Wh·kg−1, high power density of 723.14 W·kg−1, and capacitance retention of about 94% after 100 cycles. The dielectric investigation shows good dielectric properties for all materials, where the dielectric constant and the dielectric loss decreased with the frequency increase. Thus, all the interconnected studies proved that these new materials show manifold ability and real applicative potential as pseudocapacitors and high-performance dielectrics. Future work and perspectives are anticipated for characterizing electrochemical and dielectric properties for materials including larger amounts of Cu dopant.

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Czechowski, Grzegorz, e Jan Jadżyn. "Static and Dynamic Dielectric Properties of Mesogenic n-Nonyloxycyanobiphenyl (9OCB)". Zeitschrift für Naturforschung A 62, n. 1-2 (1 febbraio 2007): 61–66. http://dx.doi.org/10.1515/zna-2007-1-209.

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The dielectric properties of n-nonyloxycyanobiphenyl in the isotropic (I), nematic (N) and smectic A (SA) phases were investigated. The dielectric relaxation spectra, recorded in the frequency range 50 kHz - 100 MHz, were analyzed with use of the Cole-Cole equation. An anomalous temperature behavior of the static permittivity, the rotational diffusion exponent and the activation energy of mesogenic molecules rotating around their short axis, observed in the vicinity of the phase transitions, are discussed.

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Più fonti

Tesi sul tema "Dynamic dielectric properties"

Comer, Anthony C. "DYNAMIC RELAXATION PROPERTIES OF AROMATIC POLYIMIDES AND POLYMER NANOCOMPOSITES". UKnowledge, 2011. http://uknowledge.uky.edu/cme_etds/1.

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The dynamic relaxation characteristics of Matrimid® (BTDA-DAPI) polyimide and several functionalized aromatic polyimides have been investigated using dynamic mechanical and dielectric methods. The functionalized polyimides were thermally rearranged to generate polybenzoxazole membranes with controlled free volume characteristics. All polyimides have application in membrane separations and exhibit three motional processes with increasing temperature: two sub-glass relaxations (ƴ and β transitions), and the glass-rubber (α) transition. For Matrimid, the low-temperature ƴ transition is purely non-cooperative, while the β sub-glass transition shows a more cooperative character as assessed via the Starkweather method. For the thermally rearranged polyimides, the ƴ transition is a function of the polymer synthesis method, thermal history, and ambient moisture. The β relaxation shows a dual character with increasing thermal rearrangement, the emerging lower-temperature component reflecting motions encompassing a more compact backbone contour. For the glass-rubber (α) transition, dynamic mechanical studies reveal a strong shift in Tα to higher temperatures and a progressive reduction in relaxation intensity with increasing degree of thermal rearrangement. The dynamic relaxation characteristics of poly(ether imide) and poly(methyl methacrylate) nanocomposites were investigated by dynamic mechanical analysis and dielectric spectroscopy. The nanoparticles used were native and surface-modified fumed silicas. The nanocomposites display a dual glass transition behavior encompassing a bulk polymer glass transition, and a second, higher-temperature transition reflecting relaxation of polymer chain segments constrained owing to their proximity to the particle surface. The position and intensity of the higher-temperature transition varies with particle loading and surface chemistry, and reflects the relative populations of segments constrained or immobilized at the particle-polymer interface. Dielectric measurements, which were used to probe the time-temperature response across the local sub-glass relaxations, indicate no variation in relaxation characteristics with particle loading. Nanocomposite studies were also conducted on rubbery poly(ethylene oxide) networks crosslinked in the presence of MgO or SiO2 nanoparticles. The inclusion of nanoparticles led to a systematic increase in rubbery modulus and a modest positive offset in the measured glass transition temperature (Tα) for both systems. The sizeable increases in gas transport with particle loading reported for certain other rubbery nanocomposite systems were not realized in these crosslinked networks.

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Wang, Yunfei. "Correlation of dynamic dielectric properties to reaction kinetics and changing mechanical properties of epoxy resins during cure". W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623894.

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The principal objective of this paper is to describe how complex impedance, obtained from frequency dependent dielectric sensing technique, can be used as an effective diagnostic tool for in situ real-time investigation in the fabrication of thermoset structures.;Two epoxy systems (Pr500 from 3M and My720 from Ciba Geigy) with different functionality are characterized in terms of their dielectric, thermal, and rheological behavior. It is observed that there is a one to one relationship between Tg and conversion which is independent of cure temperature. The chemical kinetics of the reaction is satisfactorily described by an autocatalyzed reaction mechanism. The chemical rate constant has the usual Arrhenius form, whereas the diffusion rate constant is assumed to be given by a modified form of the Williams-Landel-Ferry (WLF) equation. The overall reaction rate constant is modeled by a combination of the chemical rate constant and the diffusion rate constant. The ability of the frequency dependent dielectric sensing technique to monitor the progress of curing reaction, build up in glass transition temperature, viscosity and to detect the time of occurrence of gel during thermoset cure are explored. The temperature dependence of the dielectric relaxation time, ionic conductivity and viscosity are described by the modified WLF equation. This approach provides a common framework for describing and comparing different related properties.

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Marashdeh, Wajeeh. "Relaxation Behavior and Electrical Properties of Polyimide/Graphene Nanocomposite". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1595850361812632.

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BRUNENGO, ELISABETTA. "Engineered poly(vinylidene fluoride) based composites containing inorganic inclusions as materials for energy-related applications: process-structure-properties correlations". Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1041104.

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In recent years the continuous and rapid development of the electronic industry together with the need for more efficient electric energy harvesting have notably increased the demand for: (i) high dielectric constant and breakdown strength materials for high energy density capacitors and (ii) piezoelectric flexible materials, with the ability to bend into diverse shapes, for powering low-power portable devices and self-powered electronic systems. Polymer-based composites and nanocomposites with inclusions of a ceramic active phase are very attractive for these applications because they combine materials with different characteristics, allowing the possibility to tune and optimize the dielectric and piezoelectric properties in the ensuing composite systems. In particular, many parameters can affect the material performance: (i) the nature of the polymer matrix and active component; (ii) the phases connectivity; (iii) the filler concentration, shape and dimensions; (iv) the filler/matrix interactions; (v) the preparation technique and processing. All this variability expands the possible applications of polymer-composites for energy-related purposes but also increases the difficulty in realistically predicting their ultimate properties. The design of polymer composites thus requires a rational selection of components, good interface engineering and proper processing optimization. To achieve this, a thorough comprehension of the process-structure-properties correlations is very important. This is the principal aim of this thesis work, which focus on the preparation of poly(vinylidene fluoride) homopolymer (PVDF) or poly(vinylidene fluoride-co-hexafluoropropylene) copolymer (PVDF-HFP) based composites with 0-3 connectivity containing different perovskite fillers, namely, BaTiO3 (BT), Pb(Zr,Ti)O3 (PZT) and Na0.5Bi0.5TiO3 - BaTiO3 (BNBT). The filler particles were used as prepared or properly surface modified and several techniques were employed for the composites preparation (i.e., solvent casting, melt blending, hot-pressing, compression moulding). Initially, a study of the neat polymer matrices was performed, by using, for the first time in literature, the compression moulding technique to tune the polymorphism of PVDF. A principal component analysis was performed on the infrared spectra of the moulded films to validate the equation usually employed for determining the electroactive phase amount (FEA) then multiple linear regression was applied to better understand how the processing parameters affect the FEA value. A double-step procedure was proven fundamental in inducing the formation of PVDF β phase and improving the dielectric properties of the ensuing polymer films. After this preparatory investigation, the study of the process-structure-properties correlations was extended to PVDF-based composites, addressing three main issues: (i) the influence of processing on the ultimate properties of the prepared samples; (ii) the influence of particles dimensions and surface modification on the dielectric behaviour of the composite materials; (iii) the response of flexible piezoelectric composites. The preparation technique affects the microstructure at different levels, but it was found that not always a flawless particles dispersion necessary leads to the best final performance of the composite. Whereas, a proper moulding method, by affecting the polymorphism of the polymer matrix and the compactness of the film, can improve significantly the dielectric response. The presence of an inorganic shell around BT particles allows a modulation of the effective permittivity of the composites; if intrinsic factors (i.e., the permittivity of the components) prevail on extrinsic ones (i.e., interfacial polarization), the composites response can be predicted by FEM calculations. However, in these conditions, the reduction in the dielectric constant compensates for the increase of the breakdown strength promoted by the shell and, as a whole, the stored energy decreases. It is worth noting that the composites containing core-shell particles are characterized by low tunability, a condition which is important for application as dielectric capacitors. The functionalization of the ceramic particles with the tested coupling agents, despite decreasing to a certain extent the dielectric permittivity of the ensuing composites (due to the intrinsic low permittivity of the silane moieties), increases the maximum electric field, thus leading to an energy recovering capability comparable or slightly higher than that of the composite containing pristine BT particles. The dielectric response of the composites is affected by the particles dimensions even though the films containing pristine BT and those containing TiO2-coated particles exhibit a different trend of dielectric permittivity with filler size; this suggests a not negligible contribution of the interfaces, which varies with the method of particles synthesis. As concerns the piezoelectric composites, the piezoelectric coefficient (d33), in general, increases if the filler dimensions increase significantly. The higher response of the samples containing sintered and crushed PZT or BNBT particles (with respect to simply calcined powders) probably derived from the higher particles connectivity inside the agglomerates, which in turn leads to higher local stresses inside the material. As far as we know, the piezoelectric properties of composites made of fluorinated polymer matrices and BNBT filler had not been studied yet. The obtained d33 are in line with those of many flexible lead-free composites made with particles different from BNBT, suggesting the potentiality of these composites in the field of energy harvesting. As principal achievements, I obtained: (i) an alternative and smart method to tune the polymorphism of PVDF homopolymer and its copolymers, by exploiting a simple and easily-scalable processing technique; (ii) solvent-free fabrication of polymer-based composites with dielectric properties improved by the moulding process; (iii) a better comprehension about the role of the interfaces, useful to tune the final performance of the dielectric composites; (iv) flexible lead-free polymer-based composites with a good piezoelectric response for potential application as safe energy harvesting devices.

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Rotaru, Andrei. "Novel polar dielectrics with the tetragonal tungsten bronze structure". Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4184.

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There is great interest in the development of new polar dielectric ceramics and multiferroic materials with new and improved properties. A family of tetragonal tungsten bronze (TTB) relaxors of composition Ba₆M³⁺Nb₉O₃₀ (M³⁺ = Ga³⁺, Sc³⁺ and In³⁺, and also their solid solutions) were studied in an attempt to understand their dielectric properties to enable design of novel polar TTB materials. A combination of electrical measurements (dielectric and impedance spectroscopy) and powder diffraction (X-ray and neutron) studies as a function of temperature was employed for characterising the dynamic dipole response in these materials. The effect of B-site doping on fundamental dipolar relaxation parameters were investigated by independently fitting the dielectric permittivity to the Vogel-Fulcher (VF) model, and the dielectric loss to Universal Dielectric Response (UDR) and Arrhenius models. These studies showed an increase in the characteristic dipole freezing temperature (T[subscript(f)]) with increase B-cation radius. Crystallographic data indicated a corresponding maximum in tetragonal strain at T[subscript(f)], consistent with the slowing and eventual freezing of dipoles. In addition, the B1 crystallographic site was shown to be most active in terms of the dipolar response. A more in-depth analysis of the relaxor behaviour of these materials revealed that, with the stepwise increase in the ionic radius of the M³⁺ cation on the B-site within the Sc-In solid solution series, the Vogel-Fulcher curves (lnf vs. T[subscript(m)]) are displaced to higher temperatures, while the degree of relaxor behaviour (frequency dependence) increases. Unfortunately, additional features appear in the dielectric spectroscopy data, dramatically affecting the Vogel-Fulcher fitting parameters. A parametric study of the reproducibility of acquisition and analysis of dielectric data was therefore carried out. The applicability of the Vogel-Fulcher expression to fit dielectric permittivity data was investigated, from the simple unrestricted (“free”) fit to a wider range of imposed values for the VF relaxation parameters that fit with high accuracy the experimental data. The reproducibility of the dielectric data and the relaxation parameters obtained by VF fitting were shown to be highly sensitive to the thermal history of samples and also the conditions during dielectric data acquisition (i.e., heating/cooling rate). In contrast, UDR analysis of the dielectric loss data provided far more reproducible results, and to an extent was able to partially deconvolute the additional relaxation processes present in these materials. The exact nature of these additional relaxations is not yet fully understood. It was concluded application of the Vogel-Fulcher model should be undertaken with great care. The UDR model may represent a feasible alternative to the evaluation of fundamental relaxation parameters, and a step forward towards the understanding of the dielectric processes in tetragonal tungsten bronzes.

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Bao, Congyu. "Cellulose acetate / plasticizer systems : structure, morphology and dynamics". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10049/document.

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Les polysaccharides sont l'une des principales options à retenir pour progresser dans l'utilisation ou la conception de polymères renouvelables. Depuis les années cinquante, le développement industriel de ce type de polymères s'était considérablement réduit du fait de l'avènement des polymères synthétiques. Cependant, cet intérêt a cru considérablement ces dernières années en raison de la sensibilisation du public sur la limite des ressources fossiles. Ces biopolymères sont donc devenus un sujet d'importance, tant sur le plan industriel que sur celui de la recherche fondamentale. Toutefois, les systèmes à base de polysaccharides sont le plus souvent transformés via l'utilisation d'importantes quantités de solvants (y compris l'eau), ce qui globalement pénalise le procédé associé en l'affligeant d'une charge environnementale supplémentaire. Par la voie ‘fondue', le développement de polymères thermoplastiques à base de dérivés de la cellulose est un véritable défi, qui concerne autant le mode de transformation de ces systèmes que le niveau des propriétés du matériau final. Pour exemple, la température de dégradation de l'acétate de cellulose (CA) (dont le degré de substitution 2,5 est développé par le Groupe Solvay) est si proche de sa température de fusion que son procédé de mise en oeuvre ne peut être envisagé qu'avec l'ajout d'une quantité importante de plastifiants externes (entre 20 et 30 en poids selon le type d'additif). Le comportement d'un mélange CA-plastifiant est principalement régi par un «réseau» de très fortes interactions polaires, dont la force et la densité dépendent de 3 paramètres spécifiques: le degré de substitution de CA, la typologie de plastifiant et la quantité de plastifiant. Pour expliquer les différents mécanismes de plastification, il est donc important pour nous d'étudier et de comprendre les propriétés dynamiques (en ce qui concerne les phénomènes de relaxation) de ce type de systèmes et comment les trois leviers que nous avons identifiés peuvent influencer ou moduler les différentes interactions échangées dans les mélanges
Polysaccharides are one of the main options to the on-going move towards the use of renewable polymers. The industrial interest in this type of polymers drastically shrunk by the advent of synthetic polymers in the fifties, but is currently reviving due to the public awareness on the limit of fossil resources. These biopolymers are nowadays offering a challenging and industrially profitable playground for researchers. However, current polysaccharides based materials are mostly processed with extensive use of solvents (including water) making the total process an environmental burden despite the advantage of the starting material. Development of thermoplastic cellulose-based materials is very challenging regarding both final material properties and polymer processing. The degradation temperature of Cellulose Acetate (CA) (degree of substitution 2.5) is so close to its melting temperature that it can only be processed with a significant amount of external plasticizers (between 20 et 30 wt.% depending on the type of the additive). Behavior of a CA-plasticizer blend is mainly governed by a ‘network’ of high polar interactions, the strength and the density of which clearly depend of 3 specific parameters: the CA’s degree of substitution, the typology of the plasticizer, the amount of plasticizer. In an attempt to explain the different plasticization mechanisms, it is thus of utmost importance for us to study and understand the dynamic properties (regarding the relaxation phenomena) of this kind of systems and how the three levers that we identified can influence or modulate the different interactions exchanged within the blends

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Fakraoui, Oumaima. "Corrélation entre les propriétés diélectriques et mécaniques de nanocomposites à matrice polymère". Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0161.

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Dans le domaine des sciences des matériaux, la corrélation entre les propriétés diélectriques et mécaniques des nanocomposites polymères revêt une importance significative. Cette approche permet de prédire les comportements diélectriques à partir des caractéristiques mécaniques, et inversement, offrant ainsi une méthode alternative pour la caractérisation des matériaux, notamment lorsque les essais expérimentaux sont restreints. L'intégration de modèles fractionnaires pour établir cette corrélation représente une avancée innovante, permettant d'optimiser les performances des matériaux dans diverses applications. Dans ce contexte, l'attention accrue portée aux enjeux environnementaux a conduit à une exploration des matériaux issus de la biomasse, en raison de leur biodégradabilité et de leur impact réduit sur l'environnement. Cette recherche s'est donc également concentrée sur l'utilisation de charges cellulosiques, développant et étudiant des nanoparticules de cellulose comme renforts dans une matrice polymérique biodégradable. Les travaux ont examiné les propriétés thermiques, structurales, diélectriques et mécaniques des nanocomposites obtenus, avec pour objectif central de corréler ces deux dernières propriétés à l'aide de modèles fractionnaires. Cette corrélation vise à prédire les réponses diélectriques à partir des résultats mécaniques, et inversement. Les résultats expérimentaux mettent en évidence l'influence des biorenforts sur les caractéristiques de la matrice PVA/CS, avec une analyse détaillée des propriétés diélectriques et mécaniques dynamiques. Une corrélation classique entre ces propriétés a également été établie. Le cœur de l'étude explore la sensibilité des modèles fractionnaires et valide l'approche en établissant une corrélation entre les réponses diélectriques et mécaniques dynamiques de l'acide polylactique (PLA), puis en appliquant cette corrélation au mélange PVA/CS, démontrant ainsi la capacité à prédire la permittivité à partir du module de conservation, et réciproquement
In materials science, correlating the dielectric and mechanical properties of polymer nanocomposites is of significant importance. This correlation allows for predicting dielectric behaviors from mechanical characteristics and vice versa, offering an effective alternative for material characterization, particularly when experimental testing is limited. The application of fractional models to establish this correlation is a significant innovation, enabling the optimization of material performance across various applications. With growing environmental awareness, this research also addresses the use of biomass-derived materials due to their biodegradability and lower environmental impact. Specifically, it explores the incorporation of cellulosic fillers, developing and studying cellulose nanoparticles as reinforcements in a biodegradable polymer matrix. The research investigates the thermal, structural, dielectric, and mechanical properties of the resulting nanocomposites. The primary focus is on correlating dielectric and mechanical properties using fractional models. This correlation enables the prediction of dielectric responses from mechanical results and vice versa. Experimental results demonstrate the impact of bio-based reinforcements on the PVA/CS matrix, with a detailed examination of dynamic dielectric and mechanical properties. The study establishes a traditional correlation between these properties and further explores the sensitivity of fractional models. It validates the approach by correlating the dynamic dielectric and mechanical responses of polylactic acid (PLA) and then applies this correlation to the PVA/CS blend, showing the capability to predict permittivity from the storage modulus and vice versa

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Cavallo, Valentina. "Tailoring intermolecular interactions in methacrylate-based copolymers and nanocomposites : Effect on molecular dynamics and thermal properties". Electronic Thesis or Diss., Lyon, INSA, 2023. http://www.theses.fr/2023ISAL0103.

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Une corrélation entre l’intensité et la nature des interactions intermoléculaires et les propriétés physiques, comme la conductivité thermique, a été rapportée pour des polymères amorphes. En particulier, une augmentation de la conductivité thermique a été associée à l’ajout d’interactions plus fortes par rapport aux liaisons de Van der Walls faibles, c’est-à-dire des liaisons hydrogène et ioniques. Dans ce travail, une tentative d'adapter la conductivité thermique dans les polymères amorphes a été réalisée par ingénierie des interactions intermoléculaires. Le poly(méthylméthacrylate) PMMA a été utilisé comme modèle et des copolymères poly(méthylméthacrylate-co-acide méthacrylique) (PMMA-co-MAA) ont été synthétisés par copolymérisation radicalaire afin d'introduire des liaisons H inter-chaînes et, après neutralisation, des liaisons ioniques. Des copolymères ont été obtenus avec succès jusqu'à 30 % en poids de MAA et caractérisés. Différents comonomères ont été utilisés pour évaluer l'influence d'une unité flexible apportant des liaisons H, le 2-hydroxyéthylméthacrylate (HEMA) ou le 2-carboxyéthylacrylate (CEA). La conductivité thermique a légèrement augmenté en augmentant la teneur en MAA et HEMA, tandis que pour les copolymères CEA, la présence de défauts a empêché la mesure. Le copolymère PMMA-co-MAA a été utilisé comme matrice pour les nanocomposites à base de cellulose afin d'adapter la compatibilité des charges, grâce à la présence de liaisons H entre l'unité MAA et la surface de la cellulose. Des nanofibres de cellulose (CNF) jusqu'à 15 % en poids ont été efficacement dispersées par coulée de solvant dans un mélange de deux solvants (THF/MeOH). La conduction thermique n'a montré aucun changement significatif après l'introduction des CNF. L'analyse mécanique dynamique (DMA) et la spectroscopie diélectrique à large bande (BDS) ont été utilisées en combinaison pour caractériser pleinement la dynamique moléculaire du PMMA-co-MAA copolymère suite à l'introduction de liaisons H inter-chaînes et à l'ajout ultérieur de CNF. Une relaxation β’ supplémentaire, caractérisée par une énergie d’activation (Ea) presque quatre fois plus élevé que le Ea(β), a été trouvée pour les nanocomposites et attribuée à l’établissement de liaisons H entre les groupes -COOH de la matrice et les groupes hydroxyles du CNF. Ainsi, une étude plus approfondie de la relaxation α a permis de révéler l’influence du CNF confirmant la présence de liaisons H interfaciales. En effet, malgré les Tgs similaires caractérisant la matrice et les nanocomposites, un décalage de leurs temps de relaxation vers des températures plus élevées a été observé suite à l’ajout de CNF. Les résultats rapportés dans cette thèse ont mis en évidence que les améliorations de la conductivité thermique obtenues par la modification des interactions entre les chaînes dans les matrices amorphes restent un défi extrêmement complexe
A correlation between the strength of the intermolecular interactions and physical properties has been reported for amorphous polymers. In particular, an increment of thermal conductivity has been associated to the addition of stronger interactions compared with weak van der Walls, i.e. hydrogen and ionic bonds. In this work, an attempt to tailor thermal conductivity in amorphous polymers has been made by engineering intermolecular interactions. Poly(methylmethacrylate) PMMA was used as standard and poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) copolymers were synthesised by free radical copolymerization in order to introduce inter-chain hydrogen bonds and, after neutralisation, ionic bonds. Copolymers were successfully obtained up to 30wt% of MAA and characterized. Also, different comonomers were used to evaluate the influence of a flexible unit bringing H-bonds, 2-hydroxyethylmethacrylate (HEMA) or 2-carboxyethylacrylate (CEA). Thermal conductivity slightly increased increasing MAA and HEMA content, while for CEA copolymers the presence of defects prevented the measurement. Later, PMMA-co-MAA was used as a matrix for cellulose-based nanocomposites to tailor filler compatibility, thanks to the presence of H-bonds between MAA unit and cellulose surface. Cellulose nanofibers (CNF) up to 15wt% were efficiently dispersed by solvent casting in a mixture of two solvents (tetrahydrofuran/methanol). Thermal conduction showed no significant changes following the introduction of CNF. Dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) were used in combination to fully characterize the macromolecular mobility of PMMA-co-MAA following the introduction of inter-chain H-bonds and the subsequent addition of CNF. An additional β’-relaxation, characterized by an activation energy (Ea) nearly four times higher than the Ea(β), was found for the nanocomposites and ascribed to the establishment of H-bonds between the -COOH groups of the matrix and the hydroxyl groups of CNF, as confirmed by the lower values found for the thermal expansion coefficient of the free volume and the fragility of the material. A deeper investigation about the α-relaxation was able to reveal the influence of CNF confirming the presence of interfacial H-bonds. Indeed, despite the similar glass transition temperatures characterising the matrix and the nanocomposites, a shift of their relaxation times to higher temperatures was observed following the addition of CNF. Results reported in this thesis evidenced that the enhancements of thermal conductivity obtainable by the modification of the interchain interactions between chains in amorphous matrices remains an extremely complex challenge

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Cherqaoui, Bennaceur. "Etude du comportement rhéologique à l'état fondu et du comportement diélectrique du polyfluorure de vinylidène chargé de titanate de baryum". Saint-Etienne, 1986. http://www.theses.fr/1986STET4007.

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Etude en régime dynamique et en régime statique. L'addition de titanate augmente la constante diélectrique tout en gardant un niveau faible des pertes diélectriques. Essais d'extrusion difficiles compte tenu des temps de relaxation et viscosité élevées de la matrice

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Riedel, Clément. "Dielectric and mechanical properties of polymers at macro and nanoscale". Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20073.

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Le but de cette thèse était tout d'abord de comprendre les théories physiques qui décrivent la dynamique des polymères à l'échelle macroscopique. Le modèle de Rouse et la théorie d'enchevêtrement de De Gennes décrivent la dynamique des polymères non enchevêtrés et enchevêtrés, respectivement. Nous avons étudiés les différentes transitions entre ces deux régimes en utilisant deux techniques expérimentales: Broadband Dielectric Spectroscopy (BDS) et rhéologie. Les effets d'enchevêtrement sur les spectres diélectriques ont été discutés. Un test complet du modèle de Rouse à été effectué sur en comparant les prédictions de ce modèle pour la dépendance en fréquence de la permittivité diélectrique et du module de cisaillement aux données expérimentales. Ensuite nous avons développés des méthodes bas"s sur la microscopie à force électrostatique afin d'étudier les propriétés diélectriques locales. En utilisant la simulation numérique de la Méthode des Charges Equivalentes la constante diélectrique a été quantifiée à partir de la mesure du gradient de force crée par un potentiel statique entre une pointe et un diélectrique. Cette méthode permet d'imager la constante diélectrique avec une résolution spatial de 40 nm. Le retard de phase de la composante en 2ω de la force ou du gradient de force crée par un voltage alternatif est relié aux pertes diélectriques. En mesurant cette quantité nous avons montré que la dynamique était plus rapide proche d'une interface libre et nous avons développé un mode d'imagerie des pertes diélectriques. Cette méthode simple pourrait être appliqué en biologie ou matière molle en générale afin d'étudier des variations locales de constantes diélectriques
The aim of this thesis was first to understand the physical theories that describe the dynamics of linear polymers at the macroscopic scale. Rouse and the reptational tube theory describe the large scale dynamics of unentangled and entangled polymers respectively. Using Broadband Dielectric Spectroscopy (BDS) and rheology we have studied the different transition between these two regimes. Effects of entanglement on dielectric spectra will be discussed (Rheologica Acta. 49(5):507-512). Avoiding the segmental relaxation contribution and introducing a distribution in the molecular weight we have been able to perform a comparison of the Rouse model with experiment dielectric and rheological data (Macromolecules 42(21): 8492-8499) Then we have developed EFM-based methods in order to study the local dynamics. Using the numerical simulation of the Equivalent Charge Method, the value of the static dielectric permittivity has been quantified from the measurement of the force gradient created by a VDC potential between a tip and a grounded dielectric (Journal of Applied Physics 106(2):024315). This method allows a quantitative mapping of dielectric properties with a 40 nm spatial resolution and is therefore suitable for the study of nano-defined domains (Physical Review E 81(1): 010801). The electrical phase lags in the 2ω components of the force or force gradient created by VAC voltage, ΔΦ2ω, are related with dielectric losses. Measuring the frequency dependence of ΔΦ2ω Crieder et al (Applied Physics Letters 91(1):013102) have shown that the dynamics at the near free surface of polymer films is faster than the one in bulk. We have used this method in order to visualize the activation of the segmental relaxation with temperature and frequency (Applied Physics Letters 96(21): 213110). All this measurements can be achieved using standard Atomic Force Microscope (and a lock-in) for VAC measurements

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Libri sul tema "Dynamic dielectric properties"

United States. National Aeronautics and Space Administration., a cura di. Report for period ending July 31, 1985 ... entitled Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties. Williamsburg, Va: College of William and Mary, Dept. of Chemistry, 1985.

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Classical and Quantum Dynamics of the Multispherical Nanostructures. World Scientific Publishing Co Pte Ltd, 2004.

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The Classical And Quantum Dynamics Of The Multispherical Nanostructures. Imperial College Press, 2004.

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Horing, Norman J. Morgenstern. Graphene. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0012.

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Chapter 12 introduces Graphene, which is a two-dimensional “Dirac-like” material in the sense that its energy spectrum resembles that of a relativistic electron/positron (hole) described by the Dirac equation (having zero mass in this case). Its device-friendly properties of high electron mobility and excellent sensitivity as a sensor have attracted a huge world-wide research effort since its discovery about ten years ago. Here, the associated retarded Graphene Green’s function is treated and the dynamic, non-local dielectric function is discussed in the degenerate limit. The effects of a quantizing magnetic field on the Green’s function of a Graphene sheet and on its energy spectrum are derived in detail: Also the magnetic-field Green’s function and energy spectrum of a Graphene sheet with a quantum dot (modelled by a 2D Dirac delta-function potential) are thoroughly examined. Furthermore, Chapter 12 similarly addresses the problem of a Graphene anti-dot lattice in a magnetic field, discussing the Green’s function for propagation along the lattice axis, with a formulation of the associated eigen-energy dispersion relation. Finally, magnetic Landau quantization effects on the statistical thermodynamics of Graphene, including its Free Energy and magnetic moment, are also treated in Chapter 12 and are seen to exhibit magnetic oscillatory features.

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Nagaosa, N. Multiferroics. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0010.

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This chapter delves into the physics of multiferroics, the recent developments of which are discussed here from the viewpoint of the spin current and “emergent electromagnetism” for constrained systems. It presents the three sources of U(1) gauge fields, namely, the Berry phase associated with the noncollinear spin structure, the spin-orbit interaction (SOI), and the usual electromagnetic field. The chapter reviews multiferroic phenomena in noncollinear magnets from this viewpoint and discusses theories of multiferroic behavior of cycloidal helimagnets in terms of the spin current or vector spin chirality. Relativistic SOI leads to a coupling between the spin current and the electric polarization, and hence the ferroelectric and dielectric responses are a new and important probe for the spin states and their dynamical properties. Microscopic theories of the ground state polarization for various electronic configurations, collective modes including the electromagnon, and some predictions including photoinduced chirality switching are discussed with comparison to experimental results.

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Tiwari, Sandip. Semiconductor Physics. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198759867.001.0001.

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A graduate-level text, Semiconductor physics: Principles, theory and nanoscale covers the central topics of the field, together with advanced topics related to the nanoscale and to quantum confinement, and integrates the understanding of important attributes that go beyond the conventional solid-state and statistical expositions. Topics include the behavior of electrons, phonons and photons; the energy and entropic foundations; bandstructures and their calculation; the behavior at surfaces and interfaces, including those of heterostructures and their heterojunctions; deep and shallow point perturbations; scattering and transport, including mesoscale behavior, using the evolution and dynamics of classical and quantum ensembles from a probabilistic viewpoint; energy transformations; light-matter interactions; the role of causality; the connections between the quantum and the macroscale that lead to linear responses and Onsager relationships; fluctuations and their connections to dissipation, noise and other attributes; stress and strain effects in semiconductors; properties of high permittivity dielectrics; and remote interaction processes. The final chapter discusses the special consequences of the principles to the variety of properties (consequences of selection rules, for example) under quantum-confined conditions and in monolayer semiconductor systems. The text also bring together short appendices discussing transform theorems integral to this study, the nature of random processes, oscillator strength, A and B coefficients and other topics important for understanding semiconductor behavior. The text brings the study of semiconductor physics to the same level as that of the advanced texts of solid state by focusing exclusively on the equilibrium and off-equilibrium behaviors important in semiconductors.

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Capitoli di libri sul tema "Dynamic dielectric properties"

Artemov, Vasily. "The Dielectric Properties and Dynamic Structure of Water and Ice". In Springer Series in Chemical Physics, 131–69. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-72424-5_4.

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Karasz, Frank E., William J. MacKnight e Heung Sup Kang. "Dynamic Mechanical and Dielectric Properties of Sulfonylated Poly(2, 6-Dimethyl-1, 4-Phenylene Oxide) Copolymers". In Frontiers of Polymer Research, 489–95. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3856-1_54.

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Huang, Kama, Xiaoqing Yang e Huacheng Zhu. "Characterization and Measurement of a Chemical Reaction’s Dielectric Properties". In Dynamics in Microwave Chemistry, 5–40. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-9655-1_2.

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Kliewer, K. L., e R. Fuchs. "Theory of Dynamical Properties of Dielectric Surfaces". In Advances in Chemical Physics, 355–541. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470143797.ch4.

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Devreese, J. T., e F. Brosens. "Basic Concepts in Dielectric Response and Pseudopotentials". In Electronic Structure, Dynamics, and Quantum Structural Properties of Condensed Matter, 9–112. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4757-0899-8_2.

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Kremer, F. "Broadband Dielectric Spectroscopy to Study the Molecular Dynamics of Polymers Having Different Molecular Architectures". In Physical Properties of Polymers Handbook, 385–93. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-69002-5_21.

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Devreese, J. T., P. E. Van Camp e V. E. Van Doren. "Ab-Initio Calculation of the Phonon Frequencies in Covalent Semiconductors Using the Dielectric Screening Method". In Electronic Structure, Dynamics, and Quantum Structural Properties of Condensed Matter, 157–72. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4757-0899-8_4.

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Xi, X. X., A. A. Sirenko, I. A. Akimov, A. M. Clark e J. H. Hao. "Lattice Dynamics and Dielectric Properties of Ferroelectric Thin Films for Frequency Agile Devices". In Recent Developments in Electronic Materials and Devices, 355–68. 735 Ceramic Place, Westerville, Ohio 43081: The American Ceramic Society, 2012. http://dx.doi.org/10.1002/9781118371107.ch34.

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Zhao, Jun, Shu Ping Gong, G. Xiong e X. H. Yu. "Research on Sintering Dynamics and Microwave Dielectric Properties of Bi and Mn Doped Lead-Based Ceramics". In Key Engineering Materials, 316–19. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-410-3.316.

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Liu, Daosheng, Hengcen Zhu e Chele Cui. "Investigation on the Effect of Micro Water Content on the Dielectric Properties of Natural Ester Insulation Oil by Molecular Dynamics Simulation". In Lecture Notes in Electrical Engineering, 593–99. Singapore: Springer Nature Singapore, 2025. https://doi.org/10.1007/978-981-96-1387-8_58.

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Atti di convegni sul tema "Dynamic dielectric properties"

Zhang, Z., e Z. Song. "Terahertz to Mid-infrared Dielectric Properties of the Phospholipid Bilayer Based on Molecular Dynamics Simulation". In 2024 IEEE International Conference on Plasma Science (ICOPS), 1. IEEE, 2024. http://dx.doi.org/10.1109/icops58192.2024.10627407.

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Xiao, Shumin. "Dynamic color displays using all-dielectric metasurfaces (Conference Presentation)". In Photonic and Phononic Properties of Engineered Nanostructures IX, a cura di Ali Adibi, Shawn-Yu Lin e Axel Scherer. SPIE, 2019. http://dx.doi.org/10.1117/12.2513798.

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Czerkas, Susan, A. Burczyk, Grzegorz Czechowski e Jan Jadzyn. "Static and dynamic dielectric properties of 6-OCB and 8-OCB". In International Conference on Dielectric and Related Phenomena '98, a cura di Andrzej Wlochowicz. SPIE, 1999. http://dx.doi.org/10.1117/12.373708.

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Huo, Xiaojing, Bing Feng, Yu Su, Man Xu, Lianjie Zhang e Wuzhou Zhu. "Low-frequency dielectric and dynamic mechanical properties of XLPE retired cables". In 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2015. http://dx.doi.org/10.1109/icpadm.2015.7295387.

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Ghoneim, Ahmed M., Martina Stockhause, U. Becker, R. Biedenkap e R. Elsebrock. "Dynamic dielectric properties of some carboxylic acid esters in benzene solution". In Dielectric and Related Phenomena: Materials Physico-Chemistry, Spectrometric Investigations, and Applications, a cura di Andrzej Wlochowicz. SPIE, 1997. http://dx.doi.org/10.1117/12.276274.

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Masud, Md Abdulla Al, e Zoubeida Ounaies. "Dielectric Properties of Dielectrophoretically Aligned ZnO-PDMS Composites". In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9128.

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ZnO based polymer composite materials are of great interest because of their excellent electrical, optical, semiconductor and biocompatible properties. In this study, we synthesize anisotropic composites of aligned ZnO rods in polydimethylsiloxane (PDMS) elastomer and study their dielectric properties as a function of applied electric field and frequency. Submicron ZnO rods are synthesized using an inexpensive, high yield chemical route. Washed and purified ZnO rods are then aligned in uncured PDMS at different electric field and frequency. We find that under electric field, ZnO rotates with their long axis in the direction of the electric field and before coalescing form chains in the silicone elastomer. From the optical microscopy images and in situ dielectric measurements, the best alignment parameters are found at 4 kV/mm and 10 kHz. These conditions are then selected to prepare aligned ZnO-PDMS composites. Complete curing of composites is confirmed using dynamic mechanical analysis (DMA). Our results show that aligned ZnO in uncured PDMS exhibit higher dielectric permittivity compared to random dispersion with the same composition. For the cured ZnO-PDMS composites, dielectric permittivity increases by 80% compared to random composites.

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Li Yanming, Liu Gang e Chen Xiyang. "Study on dynamic prediction of contamination deposit of insulators". In 2009 IEEE 9th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2009. http://dx.doi.org/10.1109/icpadm.2009.5252339.

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Du, B. X., Yong Liu, Y. S. Xia, B. X. Yang e B. C. Liu. "Dynamic behavior of water droplet for evaluating outdoor insulator". In 2009 IEEE 9th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2009. http://dx.doi.org/10.1109/icpadm.2009.5252430.

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Du Lin, Wang Shibin e Lin Sen. "Dynamic Faraday magneto-optical properties of the water-based Fe3O4 magnetic fluids". In 2010 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP 2010). IEEE, 2010. http://dx.doi.org/10.1109/ceidp.2010.5724042.

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Li, Chuanyang, Jinliang He, Jun Hu, Boya Zhang e Guixin Zhang. "Dynamic observation of dc surface charge dissipation for epoxy-resin/alumina composite". In 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2015. http://dx.doi.org/10.1109/icpadm.2015.7295283.

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