The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Pingkai Jiang - One of the best experts on this subject based on the ideXlab platform.
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fluoro polymer functionalized graphene for flexible ferroelectric polymer based high k nanocomposites with suppressed Dielectric Loss and Low percolation threshold
Nanoscale, 2014Co-Authors: Ke Yang, Xingyi Huang, Lijun Fang, Jinliang He, Pingkai JiangAbstract:Flexible nanoDielectric materials with high Dielectric constant and Low Dielectric Loss have huge potential applications in the modern electronic and electric industry. Graphene sheets (GS) and reduced-graphene oxide (RGO) are promising fillers for preparing flexible polymer-based nanoDielectric materials because of their unique two-dimensional structure and excellent electrical and mechanical properties. However, the easy aggregation of GS/RGO significantly limits the potential of graphene in enhancing the Dielectric constant of polymer composites. In addition, the poor filler/matrix nanoscale interfacial adhesion also causes difficulties in suppressing the Dielectric Loss of the composites. In this work, using a facile and environmentally friendly approach, polydopamine coated RGO (PDA-RGO) and fluoro-polymer functionalized RGO (PF-PDA-RGO) were prepared. Compared with the RGO prepared by the conventional methods [i.e. hydrazine reduced-graphene oxide (H-RGO)] and PDA-RGO, the resulting PF-PDA-RGO nanosheets exhibit excellent dispersion in the ferroelectric polymer matrix [i.e. poly(vinylidene fluoride-co-hexafluoro propylene), P(VDF-HFP)] and strong interfacial adhesion with the matrix, leading to a Low percolation threshold (fc = 1.06 vol%) and excellent flexibility for the corresponding nanocomposites. Among the three nanocomposites, the P(VDF-HFP)/PF-PDA-RGO nanocomposites exhibited the optimum performance (i.e. simultaneously having high Dielectric constant and Low Dielectric Loss). For instance, at 1000 Hz, the P(VDF-HFP) nanocomposite sample with 1.0 vol% PF-PDA-RGO has a Dielectric constant of 107.9 and a Dielectric Loss of 0.070, showing good potential for Dielectric applications. Our strategy provides a new pathway to prepare high performance flexible nanoDielectric materials.
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combining raft polymerization and thiol ene click reaction for core shell structured polymer batio3 nanoDielectrics with high Dielectric constant Low Dielectric Loss and high energy storage capability
ACS Applied Materials & Interfaces, 2014Co-Authors: Ke Yang, Xingyi Huang, T Tanaka, Pingkai JiangAbstract:NanoDielectric materials with high Dielectric constant, Low Dielectric Loss, and high energy storage capability are highly desirable in modern electric and electronics industries. It has been proved that the preparation of core–shell structured Dielectric polymer nanocomposites via “grafting from” method is an effective approach to these materials. However, by using this approach, the deep understanding of the structure–Dielectric property relationship of the core–shell structured nanoDielectrics has been limited because of the lack of detailed information (e.g., molecular weight, grafting density) about the macromolecules grafted onto the nanoparticle surfaces. In this work, by the combination of reversible addition–fragmentation chain transfer (RAFT) polymerization and thiol–ene click reaction, two types of core–shell structured polymer@BaTiO3 (polymer@BT) nanocomposites with high Dielectric constant and Low Dielectric Loss were successfully prepared via a “grafting to” method. Compared with the “grafti...
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core double shell structured batio3 polymer nanocomposites with high Dielectric constant and Low Dielectric Loss for energy storage application
Journal of Physical Chemistry C, 2013Co-Authors: Xingyi Huang, Yanhui Huang, Ke Yang, Pingkai JiangAbstract:Polymer nanocomposites with high Dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and Low cost. Blending and in situ polymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high Dielectric Loss and Low Dielectric constant and thus show Low energy density and Low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior Dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended...
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fluoro polymer batio3 hybrid nanoparticles prepared via raft polymerization toward ferroelectric polymer nanocomposites with high Dielectric constant and Low Dielectric Loss for energy storage application
Chemistry of Materials, 2013Co-Authors: Ke Yang, Yanhui Huang, Xingyi Huang, Liyuan Xie, Pingkai JiangAbstract:Polymer nanocomposites with high energy density and Low Dielectric Loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable Dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the Dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high Dielectric constant nanoparticles (i.e., BaTiO3) and ferroelectric polymer [i.e., poly(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO3 nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The Dielectric properties and energy storage c...
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fabrication of two dimensional hybrid sheets by decorating insulating pani on reduced graphene oxide for polymer nanocomposites with Low Dielectric Loss and high Dielectric constant
Journal of Materials Chemistry, 2012Co-Authors: Mi Li, Pingkai Jiang, Xingyi Huang, Chao Wu, Haiping Xu, Toshikatsu TanakaAbstract:Novel polyaniline decorated reduced graphene oxide (rPANI@rGO) two-dimensional (2D) hybrids sheets were successfully prepared by in situ polymerization of aniline on graphene oxide (GO) sheets and successive reduction by hydrazine. PANI is heavily reduced, thus it is electrically insulating. The hybrid sheets were used as a novel filler for high performance poly(methyl methacrylate) (PMMA) nanocomposites. Our results show that, when compared with the PMMA/rGO composites, the PMMA/rPANI@rGO nanocomposites not only show a high Dielectric constant but also have Low Dielectric Loss. For example, at 1000 Hz, a Dielectric constant of 40 and a Dielectric Loss of 0.12 were observed in the PMMA/rPANI@rGO nanocomposite with rGO/PMMA volume ratio of 6%, whereas the Dielectric constant and Dielectric Loss of PMMA/rGO composite with rGO/PMMA volume ratio of 6% are about 20 and 1250, respectively. More importantly, the Dielectric properties of PMMA/rPANI@rGO nanocomposites can be tuned by controlling the addition of the hybrid sheets. The improved Dielectric properties in PMMA/rPANI@rGO nanocomposites should originate from the isolation effect of rPANI on the rGO in PMMA matrix, which not only improves the dispersion of rGO but also hinders the direct electrical contact between rGO. This research sets up a novel route to polymer composites with high Dielectric constants and Low Dielectric Loss, and also expands the application space of graphene-based fillers.
Hong Wang - One of the best experts on this subject based on the ideXlab platform.
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novel organic inorganic composites with high thermal conductivity for electronic packaging applications a key issue review
Polymer Composites, 2017Co-Authors: Yongcun Zhou, Feng Liu, Hong WangAbstract:Significant progress has been made recently in developing the organic–inorganic composites with high thermal conductivity, Low Dielectric constant, and Dielectric Loss, for applications in the electronic packaging and substrates. Many studies have shown that some polymers filled with high thermal conductivity and Low Dielectric Loss ceramics are suitable for electronic packaging for device encapsulation. Until now, extensive attentions have been paid to the preparation of polymeric composites with high thermal conductivity and Low Dielectric Loss for the application in electronic packaging. In contrast, the thermal conductivities of these Dielectric materials are still not high enough and that might restrict their serviceable range. Herein, we briefly reviewed recent progress in this field and introduced a kind of novel composites with surface insulation modified metal aluminum cores to form multilayer coating structures as fillers in polyimide matrix for electronic applications. This structure can significantly improve the thermal conductivity and Dielectric properties of composites and give some insights into the effects of modified fillers of composite materials. Such multilayer core–shell structures should have great potentials for the improvement of nanoparticle-based fillers and applications of electronic packaging. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers
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Enhanced electric breakdown strength and high energy density of barium titanate filled polymer nanocomposites
Journal of Applied Physics, 2013Co-Authors: Ke Yu, Yujuan Niu, Feng Xiang, Yongcun Zhou, Yuanyuan Bai, Hong WangAbstract:We report improved electric breakdown strength, high energy density, and Low Dielectric Loss of nanocomposites using surface modified BaTiO3 (BT) nanoparticles filling in poly(vinylidene fluoride) polymer matrix. Dielectric and electric breakdown properties of the nanocomposites have been investigated as a function of BT content. The electric breakdown strength of 285 MV/m has been achieved at the nanocomposite with 10 vol. % BT nanoparticles. The results indicate that functionalized and produced passivation layers on the surface of ceramic fillers can improve the homogeneity of the nanocomposites, promote space charge and interface effects, and significantly enhance electric breakdown strength of the nanocomposites.
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a novel magneto Dielectric solid solution ceramic 0 25life5o8 0 75li2znti3o8 with relatively high permeability and ultra Low Dielectric Loss
Journal of the American Ceramic Society, 2012Co-Authors: Di Zhou, Jing Guo, Haibo Yang, Hong WangAbstract:In this study, a 0.25LiFe5O8–0.75Li2ZnTi3O8 solid solution ceramic was developed via the solid-state reaction method. Its phase evolution, microstructure, and sintering behavior were investigated and it was found that the 25 mol.% LiFe5O8 phase is almost fully soluble in Li2ZnTi3O8, and only the Li2ZnTi3O8 type spinel phase was formed in the 0.25LiFe5O8–0.75Li2ZnTi3O8 ceramic. The ceramic sample sintered at 1050°C for 2 h was found to possess both good magnetic properties and Dielectric properties in the frequency range from 1 to 10 MHz, with permeability between 38.2 and 15 and magnetic Loss tangent between 0.25 and 0.75, permittivity between 19.6 and 19.3 and Dielectric Loss tangent between 8 × 10−3 and 2 × 10−3. The sample also possesses good microwave Dielectric properties with a relative permittivity of 19.1, a high quality factor (Qf) ~11,770 GHz (at 6.84 GHz). The ceramic is a novel magneto-Dielectric ceramic with both high permeability and good Dielectric properties, which might be a good candidate for the applications in novel electronic devices.
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Low temperature firing microwave Dielectric ceramics k0 5ln0 5 moo4 ln nd and sm with Low Dielectric Loss
Journal of The European Ceramic Society, 2011Co-Authors: Di Zhou, Hong Wang, Jing Guo, Lixia Pang, Gaoqun Zhang, Xi YaoAbstract:Abstract In the present work, novel Low temperature firing microwave Dielectric ceramics (K0.5Ln0.5)MoO4 (Ln = Nd and Sm) were prepared via the traditional solid state reaction method. A pure monoclinic phase can be formed at a Low sintering temperature around 680 °C for both (K0.5Nd0.5)MoO4 and (K0.5Sm0.5)MoO4 ceramics. The densification temperature for the (K0.5Nd0.5)MoO4 and (K0.5Sm0.5)MoO4 ceramics are 700 °C and 800 °C for 2 h, respectively. The best microwave Dielectric properties for (K0.5Nd0.5)MoO4 was obtained in ceramic sample sintered at 760 °C for 2 h, with a Dielectric permittivity of 9.8, a Qf about 69,000 GHz and a temperature coefficient of frequency about −62 ppm/°C. The best microwave Dielectric properties for (K0.5Sm0.5)MoO4 was obtained in ceramic sample sintered at 800 °C for 2 h, with a Dielectric permittivity of 9.7, a Qf about 20,000 GHz and a temperature coefficient of frequency about −65 ppm/°C.
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temperature stable microwave Dielectric ceramic 0 3li2tio3 0 7li zn0 5ti1 5 o4 with ultra Low Dielectric Loss
Materials Letters, 2011Co-Authors: Di Zhou, Hong Wang, Jing Guo, Lixia Pang, Xi YaoAbstract:Abstract In the present work, the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic was prepared via the conventional solid state reaction route, and the phase composition, microstructure, and sintering behavior were investigated. The ceramic sample sintered at 1100 °C for 2 h demonstrated high microwave Dielectric performance with a relative permittivity of 23.5, a high quality factor (Qf) ~ 88,360 GHz (at 7.4 GHz), and near zero temperature coefficient of resonant frequency about − 0.8 ppm/°C. These results indicate that the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic might be a good candidate for Dielectric resonators, filters and other microwave electronic device applications.
Li Yuan - One of the best experts on this subject based on the ideXlab platform.
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getting self healing ability and ultra Low Dielectric Loss for high k epoxy resin composites through building networks based on li0 3ti0 02ni0 68o grafted carbon nanotube bundles with unique surface architecture
Applied Surface Science, 2021Co-Authors: Bihuan Peng, Li Yuan, Guozheng LiangAbstract:Abstract Getting self-healing ability and ultra-Low Dielectric Loss is effective to achieve high service reliability and sustainable development for high Dielectric constant (high-k) polymer composites. Herein, new functional fillers with special surface architecture (sLTNO@mAC) were synthesized by grafting Li0.3Ti0.02Ni0.68O particles (sLTNO) on surfaces of carbon nanotube bundles (mAC), which was then embedded in epoxy resin (EP) with disulfide bonds to develop new composites (sLTNO@mAC/EP). Compared with composites based on mAC (mAC/EP) or a blend of sLTNO and mAC (sLTNO/mAC/EP) with the same filler loading, sLTNO@mAC/EP composites have much higher Dielectric constant and self-healing efficiency as well as much Lower Dielectric Loss at the same frequency. For the composite based on sLTNO@mAC with 8.2 wt% of sLTNO, coded as sLTNO1@mAC/EP, its Dielectric Loss is only 0.02, about 1.1 × 10 -3 and 9.4 × 10 -3 times of that of mAC/EP and sLTNO/mAC/EP, respectively; meanwhile its Dielectric constant (216.1, 100 Hz) is the highest value among self-healable Dielectric composites reported so far, and sLTNO1@mAC/EP has higher self-healing efficiency (97.7%) than mAC/EP and sLTNO/mAC/EP. The mechanism behind these attractive properties reveals that Dielectric properties of sLTNO@mAC/EP mainly depend on interface polarization, while those of mAC/EP and sLTNO/mAC/EP are mainly related to the integrity of conductive networks.
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an in situ k0 5na0 5 nbo3 doped barium titanate foam framework and its cyanate ester resin composites with temperature stable Dielectric properties and Low Dielectric Loss
Materials Chemistry Frontiers, 2019Co-Authors: Longhui Zheng, Li Yuan, Guozheng LiangAbstract:Lower Dielectric Loss, higher Dielectric constant and wider service temperature are prerequisites of high Dielectric constant materials for renewable and new energy generation technology. Herein, an in situ doping strategy was set up to prepare a new foam ceramic (dBTF), in which the 3D skeleton is (K0.5Na0.5)NbO3 (KNN)-doped barium titanate (BT). On this basis, a series of composites (dBTF/CE/cPES) using a blend of dBTF and cyanate ester/phenolphthalein poly(ether sulfone) (CE/cPES) as the matrix were prepared. Effects of both spatial and chemical structures on the Dielectric properties of composites were studied. When the ceramic content is only 31.5 vol%, the resultant composite (6dBTF5/CE/cPES) not only has about a 6.3 times higher Dielectric constant than the dBTF powder-filled CE/cPES composite (6dBTFp5/CE/cPES), but also exhibits outstanding temperature stability from −100 to 110 °C; moreover, the two composites have extremely Low Dielectric Loss. The reason behind these attractive properties has been discussed.
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fabrication and origin of high k carbon nanotube epoxy composites with Low Dielectric Loss through layer by layer casting technique
Carbon, 2015Co-Authors: Binghao Wang, Guozheng Liang, Li Yuan, Lizhen Huang, Aijuan GuAbstract:Abstract The distribution of polarized space charges and their relaxation behavior in high Dielectric constant electric conductor/polymer composites are main factors that determine the frequency-dependent Dielectric constant and Dielectric Loss. However, few reports focus on this motif. We present here the Dielectric performance and mechanism of a unique kind of composites with multi-layers (coded as [MWCNT/EP] x , where x refers to the number of layers), fabricated by using layer-by-layer casting technique. Each composite layer with same thickness was composed of multi-walled carbon nanotubes (MWCNTs) and epoxy (EP) resin. When the loading of MWCNTs is 0.5 wt%, the four-layer [MWCNT0.5/EP] 4 material shows the highest Dielectric constant (465 at 1 Hz) and Low Dielectric Loss tangent (0.7 at 1 Hz), about 4 and 2.1 × 10 −2 times the values of traditional MWCNT0.5/EP composite, respectively. By investigating the space charge polarization (SCP), Debye polarization and Dielectric moduli in [MWCNT/EP] x materials, the complex relationships and the origin among Dielectric constant, Dielectric Loss, frequency and the content of filler were clearly elucidated. The SCP within each layer is different from that between layers. The greatly improved Dielectric properties of [MWCNT/EP] x materials are believed to be the reinforced SCP and blocked transport of carriers between every two layers.
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Low cost and facile fabrication of titanium dioxide coated oxidized titanium diboride epoxy resin composites with high Dielectric constant and extremely Low Dielectric Loss
RSC Advances, 2013Co-Authors: Longcheng Gu, Guozheng Liang, Aijuan Gu, Wei Zhang, Tongxing Wang, Li YuanAbstract:A series of titanium dioxide (TiO2) coated titanium diboride (TiB2) particles, On-TiB2, were facilely prepared using an oxidation process; interestingly, the surface morphology of TiO2 on TiB2 can be controlled from some unconnected TiO2 particles to a full coating of TiO2 by simply adjusting the oxidation time. Based on the synthesis of On-TiB2, On-TiB2–epoxy (EP) resin composites with high Dielectric constant and very Low Dielectric Loss are developed. The influences of the structure and content of On-TiB2 on the electric and Dielectric properties of On-TiB2–EP composites were intensively studied, and the corresponding study on TiB2–EP composites was also carried out for comparison. Results show that the Dielectric properties of On-TiB2–EP composites are greatly dependent on the oxidation time for preparing On-TiB2 and the content of On-TiB2 used. 20 min is proved to be the optimum oxidation time, the structure of the resultant fillers (O20-TiB2) shows that lots of TiO2 particles exist on the surface of TiB2 but do not form a full coating. For the composite with 25 vol% O20-TiB2, the Dielectric constant is as high as 407 (at 1 Hz), about 1.8 times of the maximum value that can be reached by the TiB2–EP composites; meanwhile, the Dielectric Loss of the O20-TiB2–EP composite is as Low as 1.5 (at 1 Hz), only about 0.06 times of the corresponding value of the TiB2–EP composite. Two different equivalent circuit models are setup for O20-TiB2–EP and TiB2–EP composites to evaluate the nature behind these attractive results.
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two layer materials of polyethylene and a carbon nanotube cyanate ester composite with high Dielectric constant and extremely Low Dielectric Loss
Carbon, 2013Co-Authors: Binghao Wang, Guozheng Liang, Li Yuan, Yicheng Jiao, Limei Liu, Wei ZhangAbstract:Abstract Double-layer materials with one layer being a polyethylene (PE) film and the other layer a multi-wall carbon nanotube (MWCNT)/cyanate ester (CE) resin composite, PE-MWCNT/CE, were prepared. They have high Dielectric constant and extremely Low Dielectric Loss. For comparison, MWCNT/CE composites with different contents of MWCNTs were also prepared. Results show that the two kinds of materials have greatly different Dielectric properties. With the same content of MWCNTs, the PE-MWCNT/CE material shows a higher Dielectric constant and much Lower Dielectric Loss than the MWCNT/CE composite. More specifically, the Dielectric constant and Loss tangent at 10 Hz of the PE-MWCNT/CE material with 0.5 wt.% MWCNTs are respectively 168 and 0.006, about 1.4 and 2.5 × 10−5 times the values of the corresponding MWCNT/CE composite. The nature behinds these interesting data was detected from the space charge polarization effect and equivalent circuits. The mechanism for the unique Dielectric behavior of the PE-MWCNT/CE materials is that the presence of PE film not only reinforces the space charge polarization, but also subdues the leakage current. On the other hand, based on the discussion on the Cole–Cole plots, an effective method is developed to accurately calculate the relaxation time of space charge polarization in electric conductor/polymer materials.
Guozheng Liang - One of the best experts on this subject based on the ideXlab platform.
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getting self healing ability and ultra Low Dielectric Loss for high k epoxy resin composites through building networks based on li0 3ti0 02ni0 68o grafted carbon nanotube bundles with unique surface architecture
Applied Surface Science, 2021Co-Authors: Bihuan Peng, Li Yuan, Guozheng LiangAbstract:Abstract Getting self-healing ability and ultra-Low Dielectric Loss is effective to achieve high service reliability and sustainable development for high Dielectric constant (high-k) polymer composites. Herein, new functional fillers with special surface architecture (sLTNO@mAC) were synthesized by grafting Li0.3Ti0.02Ni0.68O particles (sLTNO) on surfaces of carbon nanotube bundles (mAC), which was then embedded in epoxy resin (EP) with disulfide bonds to develop new composites (sLTNO@mAC/EP). Compared with composites based on mAC (mAC/EP) or a blend of sLTNO and mAC (sLTNO/mAC/EP) with the same filler loading, sLTNO@mAC/EP composites have much higher Dielectric constant and self-healing efficiency as well as much Lower Dielectric Loss at the same frequency. For the composite based on sLTNO@mAC with 8.2 wt% of sLTNO, coded as sLTNO1@mAC/EP, its Dielectric Loss is only 0.02, about 1.1 × 10 -3 and 9.4 × 10 -3 times of that of mAC/EP and sLTNO/mAC/EP, respectively; meanwhile its Dielectric constant (216.1, 100 Hz) is the highest value among self-healable Dielectric composites reported so far, and sLTNO1@mAC/EP has higher self-healing efficiency (97.7%) than mAC/EP and sLTNO/mAC/EP. The mechanism behind these attractive properties reveals that Dielectric properties of sLTNO@mAC/EP mainly depend on interface polarization, while those of mAC/EP and sLTNO/mAC/EP are mainly related to the integrity of conductive networks.
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an in situ k0 5na0 5 nbo3 doped barium titanate foam framework and its cyanate ester resin composites with temperature stable Dielectric properties and Low Dielectric Loss
Materials Chemistry Frontiers, 2019Co-Authors: Longhui Zheng, Li Yuan, Guozheng LiangAbstract:Lower Dielectric Loss, higher Dielectric constant and wider service temperature are prerequisites of high Dielectric constant materials for renewable and new energy generation technology. Herein, an in situ doping strategy was set up to prepare a new foam ceramic (dBTF), in which the 3D skeleton is (K0.5Na0.5)NbO3 (KNN)-doped barium titanate (BT). On this basis, a series of composites (dBTF/CE/cPES) using a blend of dBTF and cyanate ester/phenolphthalein poly(ether sulfone) (CE/cPES) as the matrix were prepared. Effects of both spatial and chemical structures on the Dielectric properties of composites were studied. When the ceramic content is only 31.5 vol%, the resultant composite (6dBTF5/CE/cPES) not only has about a 6.3 times higher Dielectric constant than the dBTF powder-filled CE/cPES composite (6dBTFp5/CE/cPES), but also exhibits outstanding temperature stability from −100 to 110 °C; moreover, the two composites have extremely Low Dielectric Loss. The reason behind these attractive properties has been discussed.
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fabrication and origin of high k carbon nanotube epoxy composites with Low Dielectric Loss through layer by layer casting technique
Carbon, 2015Co-Authors: Binghao Wang, Guozheng Liang, Li Yuan, Lizhen Huang, Aijuan GuAbstract:Abstract The distribution of polarized space charges and their relaxation behavior in high Dielectric constant electric conductor/polymer composites are main factors that determine the frequency-dependent Dielectric constant and Dielectric Loss. However, few reports focus on this motif. We present here the Dielectric performance and mechanism of a unique kind of composites with multi-layers (coded as [MWCNT/EP] x , where x refers to the number of layers), fabricated by using layer-by-layer casting technique. Each composite layer with same thickness was composed of multi-walled carbon nanotubes (MWCNTs) and epoxy (EP) resin. When the loading of MWCNTs is 0.5 wt%, the four-layer [MWCNT0.5/EP] 4 material shows the highest Dielectric constant (465 at 1 Hz) and Low Dielectric Loss tangent (0.7 at 1 Hz), about 4 and 2.1 × 10 −2 times the values of traditional MWCNT0.5/EP composite, respectively. By investigating the space charge polarization (SCP), Debye polarization and Dielectric moduli in [MWCNT/EP] x materials, the complex relationships and the origin among Dielectric constant, Dielectric Loss, frequency and the content of filler were clearly elucidated. The SCP within each layer is different from that between layers. The greatly improved Dielectric properties of [MWCNT/EP] x materials are believed to be the reinforced SCP and blocked transport of carriers between every two layers.
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Low cost and facile fabrication of titanium dioxide coated oxidized titanium diboride epoxy resin composites with high Dielectric constant and extremely Low Dielectric Loss
RSC Advances, 2013Co-Authors: Longcheng Gu, Guozheng Liang, Aijuan Gu, Wei Zhang, Tongxing Wang, Li YuanAbstract:A series of titanium dioxide (TiO2) coated titanium diboride (TiB2) particles, On-TiB2, were facilely prepared using an oxidation process; interestingly, the surface morphology of TiO2 on TiB2 can be controlled from some unconnected TiO2 particles to a full coating of TiO2 by simply adjusting the oxidation time. Based on the synthesis of On-TiB2, On-TiB2–epoxy (EP) resin composites with high Dielectric constant and very Low Dielectric Loss are developed. The influences of the structure and content of On-TiB2 on the electric and Dielectric properties of On-TiB2–EP composites were intensively studied, and the corresponding study on TiB2–EP composites was also carried out for comparison. Results show that the Dielectric properties of On-TiB2–EP composites are greatly dependent on the oxidation time for preparing On-TiB2 and the content of On-TiB2 used. 20 min is proved to be the optimum oxidation time, the structure of the resultant fillers (O20-TiB2) shows that lots of TiO2 particles exist on the surface of TiB2 but do not form a full coating. For the composite with 25 vol% O20-TiB2, the Dielectric constant is as high as 407 (at 1 Hz), about 1.8 times of the maximum value that can be reached by the TiB2–EP composites; meanwhile, the Dielectric Loss of the O20-TiB2–EP composite is as Low as 1.5 (at 1 Hz), only about 0.06 times of the corresponding value of the TiB2–EP composite. Two different equivalent circuit models are setup for O20-TiB2–EP and TiB2–EP composites to evaluate the nature behind these attractive results.
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two layer materials of polyethylene and a carbon nanotube cyanate ester composite with high Dielectric constant and extremely Low Dielectric Loss
Carbon, 2013Co-Authors: Binghao Wang, Guozheng Liang, Li Yuan, Yicheng Jiao, Limei Liu, Wei ZhangAbstract:Abstract Double-layer materials with one layer being a polyethylene (PE) film and the other layer a multi-wall carbon nanotube (MWCNT)/cyanate ester (CE) resin composite, PE-MWCNT/CE, were prepared. They have high Dielectric constant and extremely Low Dielectric Loss. For comparison, MWCNT/CE composites with different contents of MWCNTs were also prepared. Results show that the two kinds of materials have greatly different Dielectric properties. With the same content of MWCNTs, the PE-MWCNT/CE material shows a higher Dielectric constant and much Lower Dielectric Loss than the MWCNT/CE composite. More specifically, the Dielectric constant and Loss tangent at 10 Hz of the PE-MWCNT/CE material with 0.5 wt.% MWCNTs are respectively 168 and 0.006, about 1.4 and 2.5 × 10−5 times the values of the corresponding MWCNT/CE composite. The nature behinds these interesting data was detected from the space charge polarization effect and equivalent circuits. The mechanism for the unique Dielectric behavior of the PE-MWCNT/CE materials is that the presence of PE film not only reinforces the space charge polarization, but also subdues the leakage current. On the other hand, based on the discussion on the Cole–Cole plots, an effective method is developed to accurately calculate the relaxation time of space charge polarization in electric conductor/polymer materials.
Xi Yao - One of the best experts on this subject based on the ideXlab platform.
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Low temperature firing microwave Dielectric ceramics k0 5ln0 5 moo4 ln nd and sm with Low Dielectric Loss
Journal of The European Ceramic Society, 2011Co-Authors: Di Zhou, Hong Wang, Jing Guo, Lixia Pang, Gaoqun Zhang, Xi YaoAbstract:Abstract In the present work, novel Low temperature firing microwave Dielectric ceramics (K0.5Ln0.5)MoO4 (Ln = Nd and Sm) were prepared via the traditional solid state reaction method. A pure monoclinic phase can be formed at a Low sintering temperature around 680 °C for both (K0.5Nd0.5)MoO4 and (K0.5Sm0.5)MoO4 ceramics. The densification temperature for the (K0.5Nd0.5)MoO4 and (K0.5Sm0.5)MoO4 ceramics are 700 °C and 800 °C for 2 h, respectively. The best microwave Dielectric properties for (K0.5Nd0.5)MoO4 was obtained in ceramic sample sintered at 760 °C for 2 h, with a Dielectric permittivity of 9.8, a Qf about 69,000 GHz and a temperature coefficient of frequency about −62 ppm/°C. The best microwave Dielectric properties for (K0.5Sm0.5)MoO4 was obtained in ceramic sample sintered at 800 °C for 2 h, with a Dielectric permittivity of 9.7, a Qf about 20,000 GHz and a temperature coefficient of frequency about −65 ppm/°C.
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temperature stable microwave Dielectric ceramic 0 3li2tio3 0 7li zn0 5ti1 5 o4 with ultra Low Dielectric Loss
Materials Letters, 2011Co-Authors: Di Zhou, Hong Wang, Jing Guo, Lixia Pang, Xi YaoAbstract:Abstract In the present work, the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic was prepared via the conventional solid state reaction route, and the phase composition, microstructure, and sintering behavior were investigated. The ceramic sample sintered at 1100 °C for 2 h demonstrated high microwave Dielectric performance with a relative permittivity of 23.5, a high quality factor (Qf) ~ 88,360 GHz (at 7.4 GHz), and near zero temperature coefficient of resonant frequency about − 0.8 ppm/°C. These results indicate that the 0.3Li2TiO3–0.7Li(Zn0.5Ti1.5)O4 ceramic might be a good candidate for Dielectric resonators, filters and other microwave electronic device applications.
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structures phase transformations and Dielectric properties of pyrochlores containing bismuth
Journal of the American Ceramic Society, 2005Co-Authors: Xiaoli Wang, Hong Wang, Xi YaoAbstract:The structures, phase transformations, and Dielectric properties of pyrochlore ceramics containing bismuth were studied. The relation between the orthorhombic and cubic pyrochlores in the Bi2O3-ZnO-Nb2O5 (BZN) system has been investigated. The effect of bismuth in distorted cubic pyrochlore structures is discussed. BZN compositions with pyrochlore structures have excellent Dielectric properties, very Low Dielectric Loss, and high Dielectric constants with stable frequency and temperature dependence.
