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Artykuły w czasopismach na temat "Dielectric Properties - Nanocomposites"
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Feng, Zunpeng, Yanan Hao, Jiameng Zhang, Jing Qin, Limin Guo i Ke Bi. "Dielectric Properties of Two-Dimensional Bi2Se3 Hexagonal Nanoplates Modified PVDF Nanocomposites". Advances in Polymer Technology 2019 (3.07.2019): 1–8. http://dx.doi.org/10.1155/2019/8720678.
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Topological insulator two-dimensional (2D) Bi2Se3 hexagonal nanoplates, which are highly insulating in the bulk and have a conductive topological surface state, have been prepared via an “EG- (ethylene glycol-) sol” method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Bi2Se3/PVDF (polyvinylidene fluoride) nanocomposites with various Bi2Se3 contents have been fabricated by a tape-casting method. The microstructure and dielectric performance of the Bi2Se3/PVDF nanocomposites are studied. The dielectric constant of the dense nanocomposite films keeps a relatively low value of about 16 when the Bi2Se3 content is lower than 12 vol.% then suddenly increases to 36 with a critical Bi2Se3 content of 13 vol.% due to the percolation effect of the large aspect ratio of the 2D Bi2Se3 nanoplates. The study of the Bi2Se3/PVDF nanocomposite system is conducive to the exploration of high-performance dielectrics.
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Li, Qi, Feihua Liu, Tiannan Yang, Matthew R. Gadinski, Guangzu Zhang, Long-Qing Chen i Qing Wang. "Sandwich-structured polymer nanocomposites with high energy density and great charge–discharge efficiency at elevated temperatures". Proceedings of the National Academy of Sciences 113, nr 36 (22.08.2016): 9995–10000. http://dx.doi.org/10.1073/pnas.1603792113.
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The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge–discharge efficiency at elevated temperatures. At 150 °C and 200 MV m−1, an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge–discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present.
3
Yang, Jiaming, Congji Liu, Changji Zheng, Hong Zhao, Xuan Wang i Mingze Gao. "Effects of Interfacial Charge on the DC Dielectric Properties of Nanocomposites". Journal of Nanomaterials 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/2935202.
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The interfacial charge phenomenon of MgO/low-density polyethylene (LDPE) and SiO2/LDPE nanocomposites was measured by synchrotron radiation small-angle X-ray scattering. Based on the Porod theory, the Porod curve of SiO2/LDPE nanocomposite shows negative divergence but the LDPE and MgO/LDPE do not, which reveals that interfacial charge may exist in the SiO2/LDPE nanocomposite. The DC dielectric properties of the nanocomposites are closely related to the interfacial charge. Experimental results show that the SiO2/LDPE nanocomposite has lower DC conductivity, less space charge, and higher DC breakdown strength than the MgO/LDPE nanocomposite. It is thought that the interfacial charge has a positive effect on the DC dielectric performance of nanocomposites, and the mechanism could be attributed to the scattering effects of the interfacial charge on the carrier migration. There is no obvious interfacial charge in the MgO/LDPE nanocomposite, but it still has excellent DC dielectric properties compared with LDPE, which indicates that the interfacial charge is not the only factor affecting the dielectric properties; the dipole interface layer and the reduction of free volume can also inhibit the migration of carriers and decrease electrons free path, improving the dielectric performance.
4
Polsterova, Helena. "Dielectric Properties of Nanocomposites Based on Epoxy Resin". ECS Transactions 105, nr 1 (30.11.2021): 461–66. http://dx.doi.org/10.1149/10501.0461ecst.
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Nanocomposites are subject of research in many fields of science. Electrical technology focused on the study of electrical properties of nanocomposites including breakdown strength, relative permittivity, resistivity and other. This paper describes the results of measurement of electrical parameters of a nanocomposite at various temperatures. The nanocomposite matrix was casting epoxy resin and nanoparticles were made of TiO2 powder at different concentrations.
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Li, Yan Xia, Jin Long Xie, Zhen Ming Chu, Xu Sheng Wang i Xi Yao. "Dielectric and Energy Storage Properties of Polyvinylidene Fluoride/Barium Titanate Nanocomposites". Advanced Materials Research 833 (listopad 2013): 365–69. http://dx.doi.org/10.4028/www.scientific.net/amr.833.365.
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The combination of nanoparticles with high relative permittivity and polymers with high dielectric strength offers a potential to obtain processable nanocomposites with high dielectric performance. In this work, polyvinylidene fluoride (PVDF)-barium titanate (BT) nanocomposites were prepared by spin-coating technique. The surface of BT nanoparticles was treated by titanate coupling agent NDZ101. The dielectric and energy storage properties of the system were studied as a function of BT content. The experimental results showed that the dielectric constant of the nanocomposites increased with the increase of BT content. Although pure PVDF material has the strongest dielectric breakdown strength, the discharged energy storage density Ue of the nanocomposites was greatly improved from 2.8 J/cm3 in pure PVDF film to 6.2 J/cm3 in PVDF/20 wt% BT film; due to larger polarization of the nanocomposite.
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Pattanshetti, Virappa Virupaxappa, G. M. Shashidhara i Mysore Guruswamy Veena. "Dielectric and thermal properties of magnesium oxide/poly(aryl ether ketone) nanocomposites". Science and Engineering of Composite Materials 25, nr 5 (25.09.2018): 915–25. http://dx.doi.org/10.1515/secm-2016-0273.
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AbstractIn the present study, dielectric and thermal properties of poly(aryl ether ketone) (PAEK)-nanocomposites with varying weight percentage of magnesium oxide (MgO) have been reported. The thermal properties of PAEK/MgO nanocomposites were studied using differential scanning calorimetry, thermogravimetric analysis, thermo-mechanical analysis and thermal conductivity. Transmission electron microscopy of the developed nanocomposites shows agglomerate-free dispersion of MgO nanoparticles in PAEK matrix. From the dielectric properties, dielectric constant of 13 was achieved for 10 wt% PAEK/MgO nanocomposite at 230°C. Further, minimum tan δ and maximum volume resistivity were found for 10 wt% PAEK/MgO nanocomposite. Data from thermal studies indicate that the incorporation of MgO into PAEK significantly enhanced the glass transition temperature and slightly deteriorated the thermal stability, char yield, and flame-retardant properties. Also, highest thermal conductivity and lowest coefficient of thermal expansion were achieved at 10 wt% of the MgO content. An excellent combination of both dielectric and thermal properties of the PAEK/MgO nanocomposites developed in the present study finds its potential application in microelectronics and electrical insulation in power equipments.
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Alam, Rabeya Binta, Md Hasive Ahmad, S. F. U. Farhad i Muhammad Rakibul Islam. "Significantly improved dielectric performance of bio-inspired gelatin/single-walled carbon nanotube nanocomposite". Journal of Applied Physics 131, nr 12 (28.03.2022): 124103. http://dx.doi.org/10.1063/5.0077896.
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In this study, the dielectric properties of gelatin/single-walled carbon nanotube (Gel/SWCNT) nanocomposite were evaluated. The nanocomposites were synthesized by a simple solution casting method. The electron transport properties of the nanocomposites were studied by the dielectric and impedance spectroscopy techniques. A dielectric constant as high as 104 and a loss tangent of 0.91 were obtained for the Gel/SWCNT nanocomposite material at 100 Hz. The dielectric permittivity data of the nanocomposites were fitted by the modified Cole–Cole model to estimate the dielectric strength and the relaxation time. The addition of SWCNT into the gelatin reduces the relaxation time of the nanocomposite from 3.03 to 1.01 μs. The complex impedance spectra analyses show an increase in alternating current conductivity due to the incorporation of SWCNT and can be attributed to the change in bulk resistance together with a reduction in relaxation time of the nanocomposite. A quantitative analysis from the fitting of the Cole–Cole plot also reveals that the incorporation of SWCNT into the nanocomposite decreases the grain boundary resistance from 16 950 to 53 kΩ and increases the capacitive element from 67 to 275 nF. The mechanism behind the improved dielectric performance of the Gel/SWCNT nanocomposites has been elucidated in this study.
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Dang, Yue-Mao, Ming-Sheng Zheng i Jun-Wei Zha. "Improvements of dielectric properties and energy storage performances in BaTiO3/PVDF nanocomposites by employing a thermal treatment process". Journal of Advanced Dielectrics 08, nr 06 (grudzień 2018): 1850043. http://dx.doi.org/10.1142/s2010135x18500431.
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The influence of thermal treatment on the dielectric properties and energy storage performances of a classical dielectric nanocomposite system (barium titanate/polyvinylidene fluoride PVDF) was discussed systematically. The results demonstrated that the permittivity of thermal treated nanocomposites increased and dielectric loss decreased compared with the untreated system. In addition, the energy density was also greatly improved due to the inclined residual polarization. For example, the energy density of the treated nanocomposite with 50[Formula: see text]vol.% nanofillers was 3.14 times higher than the untreated nanocomposite at 50[Formula: see text]MV/m. Moreover, the charge–discharge efficiency was also promoted from 6.36% to 56.89%. According to the viewpoint of microstructure, the improvement of the dielectric and energy storage properties would be ascribed to the suppression on void defects in the interphase of dielectric nanocomposite by employing the thermal treatment process. Finally, thermal treatment turns out to be a simple and an effective method to improve the dielectric performances and energy storage properties in the dielectric nanocomposites.
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Niaz, N. A., A. Shakoor, F. Hussain, M. Iqbal, N. R. Khalid, M. K. Saleem, N. Anwar i J. Ahmad. "Structural and electronic properties of PANI-ZnO-TiO2 nanocomposite". Journal of Ovonic Research 18, nr 5 (3.11.2022): 713–22. http://dx.doi.org/10.15251/jor.2022.185.713.
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The nanocomposites of doped Polyaniline (PANI) with ZnO-TiO2 nanoparticles have been prepared by in-situ polymerization method. The structural properties of synthesized PANI and PANI/ZnO-TiO2 were studied by X-ray diffraction (XRD) analysis. XRD pattern show that PANI is intercalated into the layers of ZnO-TiO2 successfully and thus the degree of crystallinity increases due to crystalline nature of ZnO-TiO2. FTIR analysis indicated that there is a strong interaction between ZnO-TiO2 nanoparticles and PANI. Electronic properties (Dielectric and Conductivity) of PANI and PANI/ZnO-TiO2 nanocomposite have been investigated between frequency ranges from 20Hz to 01MHz, higher dielectric constants and dielectric losses of PANI/ZnO-TiO2 nanocomposites were found. As the content of ZnO-TiO2 increased, the dielectric constant and loss also increased. The value of dielectric constant for all samples is very high at low frequency but decreases with increase in frequency. Synthesis of PANI/ZnO-TiO2 nanocomposite materials with a large dielectric constant is promising for charge storage devices applications
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Novruzova, A. A. "STRUCTURE AND ELECTROPHYSICAL PROPERTIES OF PVDF+PbS/CdS NANOCOMPOSITES". NNC RK Bulletin, nr 2 (17.10.2021): 53–56. http://dx.doi.org/10.52676/1729-7885-2021-2-53-56.
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In the given paper were investigated structure and electrophysical properties of PVDF+PbS/CdS nanocomposites. Distribution and the size of PbS and CdS nanoparticles in the polymer matrix has been studied by scanning electron microscopy (JEOL JSM-7600 F). The structure of the nanocomposite samples was investigated by the X-ray diffraction spectroscopy. The dependence of dielectric permittivity at frequency and temperature was investigated. It was shown that the dielectric permittivity of PVDF+PbS/CdS nanocomposite samples was increase in small nanoparticles content. Further increase in the concentration of the filler leads to decrease in the dielectric permittivity. The subsequent decrease in dielectric permittivity at higher nanoparticles content can be explained by the increase in defects in the structure of the nanocomposite.
Rozprawy doktorskie na temat "Dielectric Properties - Nanocomposites"
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Ayoob, Raed. "Dielectric properties of hexagonal boron nitride polymer nanocomposites". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/417272/.
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There is a growing research interest in polymer nanocomposite materials due to their potential in enhancing dielectric properties. However, a considerable amount of variability exists in the literature regarding the electrical performance of polymer nanocomposites, and therefore the underlying mechanisms underpinning their electrical properties are still far from fully understood. Possible reasons for the existing inconsistencies could be due to different material preparation techniques, different nanoparticle dispersion states, unknown filler content, inconsistent sample storage conditions, and unknown water level content in the samples. Determining the principal factors that dominate the electrical behaviour of polymer nanocomposites could allow engineers to tailor the electrical properties of dielectrics for their specific application. As a result, the work reported in this thesis was mainly set out to explore the factors governing the electrical properties of polymer nanocomposites such that the inconsistencies in the literature can be better understood, and consequently eliminated. This thesis investigated the performance of hexagonal boron nitride (hBN) nanocomposites based on two thermoplastic polymers: polystyrene and polyethylene. Prior to producing any nanocomposites, the hBN particles were characterised using different techniques. The characterisation primarily revealed that the boron nitride particles are in the hexagonal form and the surface of hBN contains a scarce amount of hydroxyl groups. Polystyrene nanocomposites were prepared containing identical amounts of hBN dispersed in different solvents in an attempt to obtain different dispersion states, as a result of different hBN/solvent interactions. The effect of solvent processing was negligible on the dispersion state of the hBN in the polystyrene; no observable difference in the dispersion and electrical properties was reported although the presence of hBN resulted in a slight increase in the breakdown strength relative to the unfilled polystyrene. A range of polyethylene nanocomposites were produced containing different amounts of hBN to understand the effect of the dispersion or aggregation state of the hBN on the breakdown strength. The results revealed that the nanocomposites, regardless of the morphology, exhibited a monotonic increase in breakdown strength with increasing hBN content from 2 wt % to 30 wt %, while maintaining the low dielectric losses of the unfilled polyethylene. While the hBN was found to have a strong nucleating effect on the polyethylene, it was determined that the local change in morphology was not the cause of the enhanced breakdown strength as both the polyethylene nanocomposites obtained by rapid crystallisation, where the development of spherulites was suppressed, and the amorphous polystyrene nanocomposites, also exhibited an improved breakdown strength. Further experiments indicated that the polyethylene nanocomposites did not absorb any moisture from the environment in ambient conditions, and absorbed a very small amount of water even in the 30 wt % polyethylene/hBN nanocomposite when completely immersed in water. Dielectric spectroscopy measurements revealed that the surface hydroxyl groups on the hBN are most likely located only on the edge surfaces of the hBN rather than basal surfaces. The water was most likely loosely bound to the hBN particles, where local water clusters formed. It was remarkable that a percolating water network was not formed in a nanocomposite consisting of an already percolating hBN network, which was largely attributed to the surface chemistry of hBN. Despite the presence of water in the system, the hBN nanocomposites continued to exhibit an enhanced breakdown strength in comparison to the unfilled polyethylene. Therefore, this thesis demonstrated that the electrical behaviour of polymer nanocomposites is most likely dominated by the surface state of the nanoparticles and how the particles interact with the charge carriers; any other effects due to local morphological changes or nanoparticle dispersion are considered to be secondary reasons for changes in the electrical properties.
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Xu, Jianwen. "Dielectric Nanocomposites for High Performance Embedded Capacitors in Organic Printed Circuit Boards". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11525.
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Conventionally discrete passive components like capacitors, resistors, and inductors are surface-mounted on top of the printed circuit boards (PCBs). To match the ever increasing demands of miniaturization, cost reduction, and high performance in microelectronic industry, a promising approach is to integrate passive components into the board during PCB manufacture. Because they are embedded inside multilayer PCBs, such components are called embedded passives.
This work focuses on the materials design, development and processing of polymer-based dielectric nanocomposites for embedded capacitor applications. The methodology of this approach is to combine the advantages of the polymer and the filler to satisfy the electric, dielectric, mechanical, fabrication, and reliability requirements for embedded capacitors. Restrained by poor adhesion and poor thermal stress reliability at high filler loadings, currently polymer-ceramic composites can only achieve a dielectric constant of less than 50. In order to increase the dielectric constant to above 50, effects of high-k polymer matrix, bimodal fillers, and dispersing agent are systematically investigated. Surface functionalization of nanofiller particles and modification of epoxy matrix with a secondary rubberized epoxy to form sea-island structure are proposed to enhance the dielectric constant, adhesion and high-temperature thermal stress reliability of high-k composites. To obtain photodefinable high-k composites, fundamental understanding of the photopolymerization of the novel epoxy-ceramic composite photoresist is addressed. While the properties of high-k composites largely depend on the polymer matrix, the fillers can also drastically affect the material properties. Carbon black- and carbon nanotubes-filled ultrahigh-k polymer composites are investigated as the candidate materials for embedded capacitors. Dielectric composites based on percolation typically show a high dielectric constant, and a high dielectric loss which is not desirable for high frequency applications. To achieve a reproducible low-loss percolative composite, a novel low-cost core-shell particle filled high-k percolative composite is developed. The nanoscale insulating shells allow the electrons in the metallic core to tunnel through it, and thereby the composites exhibit a high dielectric constant as a percolation system; on the other hand, the insulating oxide layer restricts the electron transfer between filler particles, thus leading to a low loss as in a polymer-ceramic system.
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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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Chen, Zou. "The effect of humidity and surface functionalisation on the dielectric properties of nanocomposites". Thesis, University of Leicester, 2007. http://hdl.handle.net/2381/859.
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Work is reported on composites comprising either epoxy resin or crosslinked polyethylene (XLPE) filled with silica nanoparticles (surface functionalisated and unfunctionalisated). Measurements were made of the dielectric spectra, charging and discharging currents under high electric fields, and space charge dynamics using the pulsed electroacoustic (PEA) technique. Considerable studies were made of the effect of humidity on epoxy nanocomposites. It was found that the epoxy composites filled with nanoparticles could absorb up to 60% more water by weight than the unfilled epoxy. For composites filled with microparticles, nearly all the water was absorbed by the resin. The glass transition temperature (Tg) for all epoxy samples, measured by both differential scanning calorimetry (DSC) and dielectric spectroscopy, showed a monotonic reduction with increase of hydration resulting in a 20K decrease for fully hydrated samples. This led to the conclusion that the extra hydration found in the nanocomposites was not in the bulk resin but was likely to be located on the surface of the nanoparticles. This is further supported by measurement of the hydration isotherms at room temperature and the resultant swelling as a function of humidity. A "water shell" model is developed in which there is an inner layer of approximately 5 – 10 bound water molecules on the surface of the nanoparticles, a further layer, approximately 25nm thick, in which water is in sufficient concentration to allow conduction, and an outer layer, approximately 50nm thick, which cannot support true conduction (i.e. the continuous movement of charge carriers.) This model is used to explain the sub-hertz dielectric results (in terms of percolation limited conduction) as well as those at around 1 – 10Hz that indicate the presence of bound or free water.
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Kanbur, Yasin. "Conductive Polymer Nanocomposites Of Polypropylene And Organic Field Effect Transistors With Polyethylene Gate Dielectric". Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613312/index.pdf.
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One of the aim of this study is to prepare conductive polymer nanocomposites of polypropylene to obtain better mechanical and electrical properties. Composite materials based on conductive fillers dispersed within insulating thermoplastic matrices have wide range of application. For this purpose, conductive polymer nanocomposites of polypropylene with nano dimentional conductive fillers like carbon black, carbon nanotube and fullerene were prepared. Their mechanical, electrical and thermal properties were investigated.
Polypropylene (PP)/carbon black (CB) composites at different compositions were prepared via melt blending of PP with CB. The effect of CB content on mechanical and electrical properties was studied. Test samples were prepared by injection molding and compression molding techniques. Also, the effect of processing type on mechanical and electrical properties was investigated. Composites become semiconductive with the addition of 2 wt% CB.
Polypropylene (PP) / Carbon Nanotube (CNT) and Polypropylene / Fullerene composites were prepared by melt mixing. CNT&rsquos and fullerenes were surface functionalized with HNO3 : H2SO4 before composite preparation. The CNT and fullerene content in the composites were varied as 0.5, 1.0, 2.0 and 3.0 % by weight. For the composites which contain surface modified CNT and fullerene four different compatibilizers were used. These were selected as TritonX-100, Poly(ethylene-block-polyethylene glycol), Maleic anhydride grafted Polypropylene and Cetramium Bromide. The effect of surface functionalization and different compatibilizer on mechanical, thermal and electrical properties were investigated. Best value of these properties were observed for the composites which were prepared with maleic anhydride grafted polypropylene and cetramium bromide. Another aim of this study is to built and characterize transistors which have polyethylene as dielectric layers. While doing this, polyethylene layer was deposited on gate electrode using vacuum evaporation system. Fullerene , Pentacene ve Indigo were used as semiconductor layer. Transistors work with low voltage and high on/off ratio were built with Aluminum oxide - PE and PE dielectrics.
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Preda, Ioana. "Modélisation et caractérisation des matériaux nanocomposites par des méthodes diélectriques". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20013/document.
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"Il ya beaucoup de place vers le bas!", ait déclaré Richard Feynman dans son discours sur les nanotechnologies en 1959, ouvrant un nouveau monde de la science et de la technologie! L'idée d'utiliser des nanoparticules afin d'améliorer les propriétés diélectriques des polymères qui étaient déjà en cours d'utilisation a suscité l'intérêt des chercheurs dans les deux dernières décennies. Nanocharges tels que la silice, l'alumine, l dioxyde de titan, etc, mais aussi des particules plus grosses comme les argiles ou les nanotubes de carbone ont été mélangés avec les polymères «classiques» afin d'améliorer les propriétés du polyéthylène, des résines époxy, de polypropylène, etc.De nos jours, le rendement de conversion d'énergie de générateurs électriques est limitée par des problèmes thermiques et électriques, limitations étant surtout liées à la qualité des rubans isolants appliqués sur les barres en cuivre. En conséquence, des rubans isolants innovants basés sur des de matériaux nanostructurés ont été envisagés pour augmenter le rendement énergétique des alternateurs et le but de ce travail est d'étudier ces matériaux innovants et de comparer leurs propriétés avec celles des matériaux déjà utilisés, afin d'aider à choisir le meilleur matériau composite pour les futurs rubans. Après une brève introduction sur le contexte de ce travail, on a présenté bref état de l'art les propriétés des polymères époxy, avec un débat sur les propriétés électriques de la matrice polymère choisie (résine époxyde), ses propriétés chimiques et thermiques. Ensuite, les nanocharges choisies et leurs propriétés spécifiques sont présentés, en discutant les différentes étapes du procédé de fabrication, aussi qu'un débat sur les phénomènes qui apparaissent à l'échelle nanométrique et leur éventuelle influence sur les propriétés du matériau composite fini.Différents groupes de matériaux composites à base d'époxy remplis de silice nanométrique, argile organique ou de nitrure de bore sont analysés dans ce travail. Afin de caractériser et interpréter leurs propriétés, plusieurs outils ont été utilisés: la microscopie imagerie, la caractérisation thermique ainsi que les méthodes d'investigation à fort ou faible champ électrique. Leur caractéristiques sont ressemblés et différents observations sur des propriétés «générales» ou «spécifiques» des matériaux composites ont été observés et discutés par rapport à l'influence du type de charge utilisée, de son traitement ou de son poids total sont débattues.Enfin, un modèle numérique basé sure une généralisation de la loi des mélanges sera utilisée afin de prédire la réponse diélectrique des matériaux composites ainsi que les paramètres (taille, permittivité) de l'interphase, «l'ingrédient« magique du mélange matrice de remplissage. Le modèle présenté nous a permis de donner un lien entre les différents matériaux et de valider les résultats obtenus expérimentalement. Une approche par éléments finis est utilisée.Ce manuscrit s'achève par des conclusions sur le travail présenté et il laisse entrevoir les perspectives dans l'analyse complexe des polymères nanocomposites“There's plenty of room of the bottom!” said Richard Feynman in his talk on top-down nanotechnology in 1959, bringing into the spot light a new world of science and technology ! The idea of using nanoparticles in order to improve the dielectric properties of the polymers that were already in use attracted the interest of researchers for the last two decades. Nanofillers such as silica, alumina, titania etc, but also larger particles such as clays or carbon nanotubes were mixed with the “classic” polymers in order to improve the properties of polyethylene, epoxy resins, polypropylene etc. Since nowadays the energy conversion efficiency of electrical generators is restricted by thermal and electrical issues, these limitations can be related to the electrical insulator tapes themselves. Thus, innovative insulating tapes based on nanostructured material scenarios to address the energy saving concern are intended and the purpose of this work is to investigate these innovative materials and to compare their properties with those of the materials already in use, in order to help choosing the best composite material for the future tapes.This works begins with a state of the art regarding the properties of epoxy polymers. Their chemical, thermal and dielectric properties are presented. Afterwards, the chosen fillers and their specific properties are presented. The influence of the chosen fillers as well as different steps of the nanocomposite materials manufacturing process are presented and the discussion ends with a debate on the phenomena appearing at the nanometric scale and their possible influence on the properties of the finite composite material .Different materials groups of epoxy based composites filled with nanometric silica, organoclay or boron nitride are analyzed afterwards. In order to characterize and interpret their properties, several tools were used: imaging microscopy, thermal characterization as well as high and low electric field investigation methods. A debate trying to distinguish between so called “general” or “specific” behavior of the composite materials with respect to the normal, unfilled polymer is also presented. The influence of the type of filler, its treatment or its weight total percentage will be are chosen as comparison criteria. Finally, a numerical model based on Finite Element Method approximation was used in order to predict the dielectric response of the composite materials as well as the specific parameters (size, permittivity) of the interphase, the magic “ingredient” of the matrix-filler mix. The presented model allowed us to give a connection between the different materials and validate the experimentally obtained results. This manuscript ends with conclusions on the presented work and suggests possible future works in the complex analysis of polymer nanocomposites
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Ben, ghzaiel Tayssir. "Synthèse, caractérisation et étude des propriétés magnétiques et diélectriques de nanocomposites Polyaniline/hexaferrite pour l'absorption des micro-ondes". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN003/document.
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Ces travaux de thèse consistent à élaborer des nanocomposites Polyaniline/hexaferrite pour l’absorption des micro-ondes. L’idée principale est la mise en œuvre de matériaux composites à base de polymères conducteurs intrinsèques telle la Polyaniline que nous avons dopée avec différents types d’acides (HCl, CSA, NSA et TSA…) et l’hexaferrite de baryum de type magnétoplombite (M) stœchiométrique ou substitué. Au niveau de l’hexaferrite de baryum, la substitution du Fe3+ s’est faite par les ions Al3+, Bi3+, Cr3+ et Mn3+.L’hexaferrite de baryum et les hexaferrites substitués par les différents ions cités ci-dessus ont été synthétisés par voie hydrothermale dynamique en faisant varier divers paramètres au cours de la synthèse (pH, température, temps, rapport [OH-]/[NO3-]…).L’élaboration des composites Polyaniline/hexaferrite (pur ou substitués) a été effectuée par polymérisation oxydative en utilisant plusieurs techniques de synthèse : la polymérisation chimique en solution (en tenant compte de la nature de l’acide utilisé) avec ou sans agitation (Aqueous-Based Polymerization with or without stirring) et la polymérisation oxydative par voie solide (Solid-Based Polymerization). L’optimisation de ces différentes techniques de synthèse après caractérisations physicochimiques (DRX, FTIR, ATG, MEB, EDX), diélectriques (ε’, ε’’, σdc) et magnétiques (Mr, Ms, Hc, Tc, µ’, µ’’) des échantillons, a montré que la polymérisation par voie solide se trouve la méthode la plus facile, économique et respectueuse de l’environnement. Elle est aussi adaptée à la production du composite Pani/BaFe12O19 avec de bonnes propriétés structurales, physiques et magnétiques. L’étude de la substitution du Fe3+ dans le BaFe12O19 par Al3+, Bi3+, Cr3+ et Mn3+ a montré une forte dépendance des propriétés structurales et magnétiques avec la distribution de ces ions dans la maille cristalline hexagonale. En effet, les ions Al3+, Cr3+ et Mn3+ ont une tendance à occuper les sites tétraédriques, alors que le Bi3+ occupe les sites octaédriques. Une augmentation de Hc associée à la taille des cristallites a été observée pour les particules substituées avec l'Al et le Cr alors qu’une modification de l'anisotropie magnetocristalline (fort terme d'ordre supérieur) a été mise en évidence pour les substitutions Bi et Mn, dû à leur grand rayon ionique. L’incorporation des hexaferrites substitués dans la Polyaniline pour obtenir des composites Pani/BaMeFe11O19, où Me = Al, Bi, Cr et Mn, révèle une variation des propriétés électromagnétiques dans la gamme de fréquences allant de 1 à 18 GHz. En effet, ces variations sont dues à la formation de dipôles entre l’ion de substitution et les cations O2- dans le ferrite qui sont responsables de la résonance ferromagnétique, de l'anisotropie magnétocristalline et des interactions avec la matrice polymérique. Le composite Pani/BaFe12O19 présente des absorptions dans la bande X qui se déplacent vers la bande Ku avec la substitution du fer confirmantThis thesis deals with the formulation of Polyaniline/hexaferrite nanocomposite for absorbing electromagnetic waves. The main idea is the process of composite materials based on polymers intrinsic conductors such as polyaniline that we doped with different types of acids (HCl, CSA, NSA, and ... TSA) and barium hexaferrite with magnetoplumbite structure with or without substitution according to desired stoichiometries. In the barium hexaferrite, the substitution of Fe 3+ is made by Al3+, Bi3+, Cr3+ and Mn3+ ions.The barium hexaferrite and its substitutions by different ions mentioned above were synthesized dynamic hydrothermal method by varying various parameters during the synthesis (pH, temperature, time, ratio [OH-]/[NO3-] ...).The elaboration of polyaniline/hexaferrite composite (pure or substituted) was carried out by oxidative polymerization using various synthesis techniques: Aqueous-Based Polymerisation with or without agitation (taking into account the nature of the acid used) (ABP) and Solid-Based Polymerization (SBP). The optimization of these various synthesis techniques after physicochemical (XRD, FTIR, TGA, SEM, EDX), dielectric (ε ', ε' ', σdc) and magnetic (Mr, Ms, Hc, Tc, µ', µ'') characterizations of the samples showed that the solid route is the easiest method, economical and environmentally friendly. It is also suitable for the production of composite Pani/BaFe12O19 with good structural, physical and magnetic properties.The study of the substitution of Fe 3+ in the BaFe12O19 by Al3+, Bi3+, Cr3+ and Mn3+ showed a strong dependence of the structural and magnetic properties with the distribution of these ions in the hexagonal crystal lattice. In fact, Al3+, Cr3+ and Mn3+ ions tend to occupy the tetrahedral sites, while the Bi3+ favoured the octahedral sites. An increase in Hc associated with the small crystallite size observed for particles substituted with Al and Cr and the enhancement magnetocristalline anisotropy (strong higher order term) for Bi and Mn due to their high ionic radius.The incorporation of the substituted hexaferrite in the polyaniline to obtain Pani/BaMeFe11O19 composite, where Me = Al, Bi, Cr and Mn, reveals a variation in electromagnetic properties in the frequency range from 1 to 18 GHz. In fact, these variations are due to the formation of dipoles between the substituting ion and surrounding O2- cations in the ferrite which are responsible for the ferromagnetic resonance, the magnetocrystalline anisotropy and the exchange interaction with the polymer. The composite Pani/BaFe12O19 shows absorption bands at the X-band that shift to the Ku-band with the substitution of iron, confirming the potential of these materials for microwave applications
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Kim, Mu Seong. "Design, Synthesis, Processing, and Thermal Analysis of Nanocomposites with Tunable Properties". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4099.
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Polymer composites containing nanosized fillers have generated explosive interest since the early 1980's. Many recent studies have been conducted incorporating nano-fillers into polymer matrices to design and synthesize materials with tunable mechanical, thermal, and optical properties. Conventional filled polymers, where the reinforcement is on the order of microns, have been replaced by composites with discrete nanosized fillers. Gradually, theories that predicted that composite properties are independent of particle size in the micron range were challenged by nanocomposites. Rather, nanocomposite properties are greatly influenced by the surface area of the. All of this is complicated by the fact that nanoparticles are inclined to aggregate or migrate to interfaces. Much effort has been devoted to optimize dispersion of nanofillers in the polymer matrices, as polymer-nanoparticle interactions and adhesion greatly influence performance of the material. A well- dispersed composite system with various noncovalent interactions such as those that arise from hydrogen bonding, electrostatic attractions and π-π interactions between the filler and the matrix, can transfer stress and the interface will stop the development of cracks and impede stress concentrations. Overall, large reinforcement increases are noted at low nanoparticle loadings. Additionally, functional properties such as thermal, electrical conductivity and porosity can be tailored for specific applications. The design of high performance composites requires optimizing dispersion, nanoparticle-polymer noncovalent interactions and the chemistry of the materials. Therefore polymer composites with different types of nanofillers were investigated to prove various noncovalent interaction and to improve the mechanical, thermal and electrical properties in this study.
Poly (methyl methacrylate) (PMMA) with BaTiO3 and Bi2O3 composites were fabricated by two different methods; sonication of fillers in PMMA and in situ polymerization. Samples were irradiated in air via a JL Shepherd Mark I cesium-137 source. The dose rate was 985 rads/min and the total dose was 2.0 Mrad. The polymer sonication (PSON) method has a greater effect than in situ polymerization on sample uniformity. With the PSON method there was a slight improvement in rad hardness in the barium titanate composites. This is the case with and without MWNTs and coupling agents. The storage modulus and loss modulus were measured via Dynamic Mechanical Analyzer (DMA) under the tension film mode using a heating rate of 5 °C min-1 from -150 °C to 200 °C and a scanning frequency range of 1-100 Hz. Scanning electron microscopy (SEM) provided images of the polymer-nanocomposites.
An aliphatic isocyanate, polyether, polyol thermoplastic polyurethane, Tecoflex® SG-85A, was solution processed with the varying amounts of silica nanowire. A new grade polyurethane, Tecoflex®, was synthesized from the aliphatic 4,4-methylene dicyclohexyl diisocyanate (H12MDI) with polytetramethylene ether glycol. Despite Tecoflex®'s longevity and wide use, this polymer's dielectric behavior has not been widely studied. Therefore, the dielectric response of neat PU, Tecoflex®, and PU composites with silica nanowire from -150 to 150 °C is presented. The mechanism of nanowire growing with diameters ranging from 50 to 500 nm has been established to follow the vapour liquid solid (VLS) model via the PtSi phase acting as the catalyst. Our previous thermal stability study of PU nanowire composites have yielded increased heat stability to 330 °C. In comparison, neat PU only maintains thermal stability in temperatures that range to 250 °C. The onset of decomposition temperature was measured by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) provided images of the polymer-nanocomposites.
A series of PMMA-dodecyloxy NB and PHEMA-dodecyloxy NB composites were synthesized in situ and characterized. The dodecyl groups significantly alter the solubility of the nanoballs, imparting hydrophobicity to the surface of the nanoball. A comparison study was made between the PMMA-NB and PHEMA-NB nanocomposites. Structure property relations are discussed in terms of interactions between the polymer matrices and nanoball surfaces and interiors. These OC12 NB and the hydroxyl NB polymer composites are the first studies to date that probe relaxations and conductivity in discrete polyhedral metal-organic polymer composites.
A novel ultra-flexible polycarbonate-polyurethane (PCPU) was synthesized with methylene bis(4-cyclohexylisocyanate), 1,4 butanediol as a chain extender and a polycarbonate polyol containing 1,6-hexanediol and 3-methyl-1,5-pentanediol. Through the techniques of water coagulation, the synthesis of self-healing PCPU with various concentrations of SWNT (Single-Walled Nanotubes) is possible. The resulting features of this synthesized rubber-like substance are to be evaluated to determine glass transition temperature. This novel type of polyurethane material targets growing markets for biocompatible polymers. Also, a secondary goal of this project is to obtain information useful to determining whether PCPU-carbon nanotube composites would be good candidates for use as a gel electrolyte in polymer batteries.
All nanocomposites were characterized by differential scanning calorimetry (DSC) to determine glass transition temperatures. The dielectric permittivity (ε’) and loss factor (ε”) were also measured via Dielectric Analysis (DEA) in the frequency range 1Hz to 100 kHz and between the proper temperatures in all polymer composite. The electric modulus formalism was used to reveal structural relaxations including conductivity relaxation. The activation energies for the relaxations are presented.
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Jäverberg, Nadejda. "Dielectric properties of poly(ethyelene-co-butyl acrylate) filled with Alumina nanoparticles". Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31407.
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In this work dielectric properties of the poly(ethylene-co-butyl acrylate)filled with alumina nanoparticles are evaluated. These nanocomposite materialswere manufactured at the department of Fibre and Polymer Technology,KTH.This study is limited to the properties of general importance for the AC applications.The dielectric permittivity of the nanocomposite materials wasstudied as a function of filler size, filler content, coating, temperature and airhumidity used for conditioning of the samples. The ultimate goal with thisproject is to describe the influence of material composition, temperature andair humidity on the dielectric properties and model these dependencies.In this thesis the experimental setup for voltage endurance testing of thenanocomposites, namely studying applied voltage frequency dependence ofpartial discharges in electrical trees, with a possibility of following electricaltreeing optically, was developed and described.The dielectric spectroscopy measurements were performed on thoroughly driednanocomposites - so-called dry DS study. It was shown that the experimentaldata can be fitted with Havriliak-Negami approximation, which justifiesthe correctness of the measurement results. It has been shown that addingnanoparticles to the EBA matrix changes the low frequency dispersion significantlyfor the dried samples. It was also indicated that the particle coatingused has very low impact on the resulting permittivity of the thoroughly driedsamples. From the dry DS studies it was suggested that the main cause ofthe scattering in data between the dry samples is most likely the influenceof the material inhomogeneity and possibly the moisture absorption. Thisleads to a possibility of using dielectric spectroscopy as a tool for probing thedispersion of nanoparticles in the polymer matrix.The dielectric spectroscopy measurements were also carried out on the nanocompositesconditioned in the environments with different humidity levels of air inorder to study the influence of absorbed water on the dielectric permittivity- so-called wet DS study. From the wet study it was shown that for the wetsamples the amplitude of the loss peak is defined by the filler size, filler contentand coating used; while its position in frequency domain is determinedby the coating and the humidity level used for conditioning.QC 20110315
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Briesenick, Daniel [Verfasser]. "Reinforced interphases in PAI-MMT-nanocomposites : synthesis and characterization of effects on thermal, mechanical and dielectric properties / Daniel Briesenick". Paderborn : Universitätsbibliothek, 2015. http://d-nb.info/1073944832/34.
Pełny tekst źródłaCzęści książek na temat "Dielectric Properties - Nanocomposites"
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Fothergill, J. C. "Electrical Properties". W Dielectric Polymer Nanocomposites, 197–228. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1590-0_7.
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Fothergill, J. C. "Electrical Properties". W Dielectric Polymer Nanocomposites, 197–228. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1591-7_7.
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Irwin, Patricia, Wei Zhang, Yang Cao, Xiaomei Fang i Daniel Qi Tan. "Mechanical and Thermal Properties". W Dielectric Polymer Nanocomposites, 163–96. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1590-0_6.
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Irwin, Patricia, Wei Zhang, Yang Cao, Xiaomei Fang i Daniel Qi Tan. "Mechanical and Thermal Properties". W Dielectric Polymer Nanocomposites, 163–96. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1591-7_6.
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Singh, Laxman, Dev Kumar Mahato, K. D. Mandal, Narayan Singh i Youngil Lee. "Dielectric Properties of Barium Titanate Nanocomposites". W Nanocomposites, 203–22. New York: Jenny Stanford Publishing, 2022. http://dx.doi.org/10.1201/9781003314479-10.
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Tanaka, Toshikatsu. "Interface Properties and Surface Erosion Resistance". W Dielectric Polymer Nanocomposites, 229–58. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1590-0_8.
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Tanaka, Toshikatsu. "Interface Properties and Surface Erosion Resistance". W Dielectric Polymer Nanocomposites, 229–58. Boston, MA: Springer US, 2009. http://dx.doi.org/10.1007/978-1-4419-1591-7_8.
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Gong, Guan, i Bin Li. "Chapter 7 Dielectric Properties of Bionanocomposites". W Polymer Nanocomposites for Dielectrics, 139–70. Penthouse Level, Suntec Tower 3, 8 Temasek Boulevard, Singapore 038988: Pan Stanford Publishing, 2016. http://dx.doi.org/10.1201/9781315364490-8.
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Berger, Shlomo, i Tamar Tepper. "Dielectric Properties of W-SiO2 Nanocomposites". W Interface Controlled Materials, 137–42. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/352760622x.ch23.
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Gunasekaran, Vijayasri, Mythili Narayanan, Gurusamy Rajagopal i Jegathalaprathaban Rajesh. "Electrical and Dielectric Properties: Nanomaterials". W Handbook of Magnetic Hybrid Nanoalloys and their Nanocomposites, 783–800. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-90948-2_25.
Pełny tekst źródłaStreszczenia konferencji na temat "Dielectric Properties - Nanocomposites"
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Castellon, J., M. Eesaee, E. David, N. Demarquette i M. Frechette. "Dielectric properties of LDPE/clay nanocomposites". W 2018 12th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2018. http://dx.doi.org/10.1109/icpadm.2018.8401026.
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Ciuprina, Florin, Ilona Plesa, Petru V. Notingher, Traian Zaharescu, Pascal Rain i Denis Panaitescu. "Dielectric properties of LDPE-SiO2 nanocomposites". W 2010 10th IEEE International Conference on Solid Dielectrics (ICSD). IEEE, 2010. http://dx.doi.org/10.1109/icsd.2010.5568097.
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Xiaolu Lyu, Haoran Wang, Zihao Guo i Zongren Peng. "Dielectric properties of epoxy-Al2O3 nanocomposites". W 2016 IEEE International Conference on Dielectrics (ICD). IEEE, 2016. http://dx.doi.org/10.1109/icd.2016.7547806.
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Talbi, F., E. David, D. Malec i D. Mary. "Dielectric Properties of Polyesterimide/SiO2 Nanocomposites". W 2019 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP). IEEE, 2019. http://dx.doi.org/10.1109/ceidp47102.2019.9009629.
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Chao Zhang, R. Mason i G. C. Stevens. "Dielectric properties of epoxy and polyethylene nanocomposites". W Proceedings of 2005 International Symposium on Electrical Insulating Materials, 2005. (ISEIM 2005). IEEE, 2005. http://dx.doi.org/10.1109/iseim.2005.193571.
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Ciuprina, Florin, i Laura Andrei. "Interphase dielectric properties of LDPE-TiO2 nanocomposites". W 2019 11th International Symposium on Advanced Topics in Electrical Engineering (ATEE). IEEE, 2019. http://dx.doi.org/10.1109/atee.2019.8724936.
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Han, Zhi-dong, Changjun Diao, Ying Li i Hong Zhao. "Thermal properties of LDPE/silica nanocomposites". W 2006 IEEE Conference on Electrical Insulation and Dielectric Phenomena. IEEE, 2006. http://dx.doi.org/10.1109/ceidp.2006.311931.
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Hui, L., J. K. Nelson, L. S. Schadler, S. G. Prybyla, T. G. Vargo i W. R. Peifer. "Dielectric nanocomposites prepared by gaseous infusion". W 2012 IEEE 10th International Conference on the Properties and Applications of Dielectric Materials (ICPADM). IEEE, 2012. http://dx.doi.org/10.1109/icpadm.2012.6318960.
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Kikuma, Toshiaki, Norikazu Fuse, Toshikatsu Tanaka, Yoshinao Murata i Yoshimichi Ohki. "Dielectric Properties of Low-Density Polyethylene/MgO Nanocomposites". W 2006 IEEE 8th International Conference on Properties and applications of Dielectric Materials. IEEE, 2006. http://dx.doi.org/10.1109/icpadm.2006.284181.
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Tang, Haixiong, Henry A. Sodano i Yirong Lin. "Enhanced Energy Storage in Nanocomposites Through Aligned PZT Nanowires". W ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5141.
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Nanocomposites consisting of a piezoceramic inclusion and polymer matrix offer a combination of electromechanical coupling with high toughness and ductility inherent to polymers. There is a wide range of applications for these types of materials due to their intrinsic piezoelectric and dielectric properties, such as vibration sensing, actuation, energy harvesting and capacitive energy storage. However, the relatively low piezoelectric strain coefficient and dielectric permittivity of these nanocomposites significantly limit their application in energy conversion and energy storage applications. There are mainly two coupled to improve the dielectric permittivity and electromechanical properties of piezoceramic nanocomposites, namely higher aspect ratio active inclusions and alignment of inclusions in the direction of the applied electric field. Previously, we have demonstrated that using higher aspect ratio lead zirconate titanate (PZT) nanowires (NWs) could significantly enhance the energy density and d33 coupling as compared to the samples with lower aspect ratio PZT nanorods [11]. In this paper, we will show that orientation of PZT NWs also influences energy storage capability of nanocomposite. Nanocomposites with aligned PZT NWs in the direction of the applied electric field show increased dielectric permittivity and energy density as compared to those with randomly dispersed inclusions. PZT NWs are hydrothermally synthesized, dispersed into a polyvinylidene fluoride (PVDF), cast into a film and then aligned through uniaxial stretching. Scanning electric microscopy (SEM) shows the PZT NWs are successfully aligned in direction of stretching. This work demonstrates that the energy storage and conversion capability of the nanocomposite can be significantly enhanced through the alignment of PZT NWs in the direction of the applied electric field. The findings of this research could lead to broad interest due to demonstration of developing piezoceramic nanocomposites with enhanced dielectric and electromechanical properties for next generation energy storage and conversion devices.
Raporty organizacyjne na temat "Dielectric Properties - Nanocomposites"
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Hubert, C. A., J. A. Lubin, W. H. Yang i T. E. Huber. Synthesis and Optical Properties of Dense Semiconductor-Dielectric Nanocomposites. Fort Belvoir, VA: Defense Technical Information Center, styczeń 1993. http://dx.doi.org/10.21236/ada271304.
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