Suibin Luo

Nano Ag-Deposited BaTiO3 Hybrid Particles as Fillers for Polymeric Dielectric Composites: Toward High Dielectric Constant and Suppressed Loss

Nano Ag-deposited BaTiO3 (BT-Ag) hybrid particles usable as fillers for flexible polymeric composites to obtain high dielectric constant, low conductivity, and low dielectric loss were developed. BT-Ag hybrid particles were synthesized via a seed-mediated growing process by a redox reaction between silver nitrate and ethylene glycol. Nano Ag particles with a size less than 20 nm were discretely grown on the surface of the 100 nm BaTiO3. The similar lattice spacing of the (1 1 1) planes of BT and Ag led to the hetero-epitaxial growth of Ag on the BT surface. The thickness of the coherent interface was about 3 nm. The adhesion of Ag to BT efficiently prevented the continuous contact between Ag particles in the polyvinylidene fluoride (PVDF) matrix and suppressed the formation of the conducting path in the composite. As a result, with a filler loading of 43.4 vol %, the composite exhibited a dielectric constant (Dk) value of 94.3 and dielectric loss (tan δ) of 0.06 at 1 kHz. An even higher Dk value of 160 at 1 kHz (16 times larger than that of PVDF) was obtained when the content of BT-Ag was further increased, with low conductivity (σ < 10(-5) S m(-1)) and low dielectric loss (tan δ = 0.11), demonstrating promising applications in the electronic devices.

Construction of a 3D-BaTiO3 network leading to significantly enhanced dielectric permittivity and energy storage density of polymer composites

Herein, the designed 3D-BaTiO3 network in polymer composites results in enhanced permittivity and energy storage density. High permittivities of 200 (eeff/em ∼ 55.4) and 34.5 are achieved in the composites with only 30 vol% and 16 vol% 3D-BaTiO3, respectively. The latter exhibits a discharged energy density that is over 16 times larger than the polymer matrix.

Mechanism of high dielectric performance of polymer composites induced by BaTiO3-supporting Ag hybrid fillers

BaTiO3-supporting Ag hybrid particles (BT-Ag) with varied fraction of Ag were synthesized by reducing silver nitrate in the glycol solution containing BaTiO3 (BT) suspensions. The Ag nano particles with a size of about 20 nm were discretely grown on the surface of the BT. The dielectric performance of the composites containing the BT-Ag as fillers in the matrix of polyvinylidene fluoride (PVDF) was investigated. The relative permittivity (er) of the BT-Ag/PVDF composites increased prominently with the increase of BT-Ag loading amount, and the typical conductive path of the conductor/polymer system was not observed even with a high loading of BT-Ag. The er at 100 Hz for the three BT-(0.31, 0.49, 0.61)Ag/PVDF composites at room temperature were 283, 350, and 783, respectively. The er of the composites was enhanced by more than 3 times compared with that of the composite containing untreated BT nanoparticles at frequencies over 1 kHz and the loss tangent (tan δ) was less than 0.1 which should be attributed to the low conductivity of the composites. Theoretical calculations based on the effective medium percolation theory model and series-parallel model suggested that the enhanced permittivity of BT-Ag/PVDF composites should arise from the ultrahigh permittivity of BT-Ag fillers, which was over 104 and associated with the content of Ag deposited on the surface of BT.BaTiO3-supporting Ag hybrid particles (BT-Ag) with varied fraction of Ag were synthesized by reducing silver nitrate in the glycol solution containing BaTiO3 (BT) suspensions. The Ag nano particles with a size of about 20 nm were discretely grown on the surface of the BT. The dielectric performance of the composites containing the BT-Ag as fillers in the matrix of polyvinylidene fluoride (PVDF) was investigated. The relative permittivity (er) of the BT-Ag/PVDF composites increased prominently with the increase of BT-Ag loading amount, and the typical conductive path of the conductor/polymer system was not observed even with a high loading of BT-Ag. The er at 100 Hz for the three BT-(0.31, 0.49, 0.61)Ag/PVDF composites at room temperature were 283, 350, and 783, respectively. The er of the composites was enhanced by more than 3 times compared with that of the composite containing untreated BT nanoparticles at frequencies over 1 kHz and the loss tangent (tan δ) was less than 0.1 which should be attributed t...

Critical interparticle distance for the remarkably enhanced dielectric constant of BaTiO3-Ag hybrids filled polyvinylidene fluoride composites

Discrete nano Ag-deposited BaTiO3 (BT-Ag) hybrids with varied Ag content were synthesized, and the hybrids filled polyvinylidene fluoride (PVDF) composites were prepared. The effect of Ag content on the dielectric properties of the composites were analyzed based on the diffused electrical double layer theory. Results showed that with a higher Ag content in BT-Ag hybrids, the dielectric constant of BT-Ag/PVDF composites increases fast with the filler loading, while the dielectric loss and conductivity showed a suppressed and moderate increase. The dielectric constant of BT-0.61Ag/PVDF (61 wt. % of Ag in BT-Ag hybrid) composites reached 613, with the dielectric loss of 0.29 at 1 kHz. It was deduced that remarkably enhanced dielectric constant appeared when the interparticle distance decreased to a critical value of about 20 nm.

Enhancement of dielectric performance upto GHz of the composites with polymer encapsulated hybrid BaTiO3–Cu as fillers: multiple interfacial polarizations playing a key role

Cu nanoparticles with diameters of 15–25 nm were grown discretely on the surface of BaTiO3 (about 100 nm) via a hydrothermal method, and a polyethylene glycol 4000 layer was coated on the surface of the obtained BT–Cu hybrid particles. The PEG layer will serve as a robust interface layer to suppress the mobilization of charge carriers and protect Cu from oxidation. The BT–Cu particles were loaded as fillers in the matrix of polyvinylidene fluoride (PVDF) to fabricate the BT–Cu/PVDF composites. Microstructure and dielectric performance have been investigated. The results showed that the relative permittivity (er) of the composites increased prominently with the loading amount and meanwhile the dielectric loss tangent was suppressed at a low level. For instance, the permittivity of BT–Cu/PVDF with the volume fraction of 53.7% reached 150 with a low loss of 0.16 at 1 kHz. The permittivities maintained high values of over 55 and the dielectric loss was less than 0.05 upto 1 GHz. Investigation on the polarization mechanisms has been conducted and the interfacial polarization between different phases should account for the high dielectric permittivity upto GHz. The energy storage characteristics were also studied.

Flexible BaTiO3nf-Ag/PVDF nanocomposite films with high dielectric constant and energy density

Flexible polymer composites with high dielectric constant and breakdown strength thus high energy storage density are highly desired in electrical and electronic technologies. In this study, hybrids of nano Ag particles discretely grown on the surface of BaTiO3 nanofibers (BTnfs) were synthesized and used to fabricate PVDF based nanocomposites. The results demonstrated that the dielectric constant and energy storage density of the composites were largely enhanced. An energy density of 10.25 J/cm3 was obtained for the composite containing only 2.5 vol% hybrids, increased by more than 2 times in comparison with pure PVDF.

Synthesis and characterization of Nano BaTiO 3 /epoxy composites for embedded capacitors

The miniaturization trend of integrated circuits (ICs) calls for replacing discrete passive components with embedded passives. Among the passive components, the embedded decoupling capacitors which are used for simultaneous switching noise suppression have drawn great attention. It is because decoupling capacitors should be placed as near as possible to a chip to reduce parasitic inductance. Important requirements for embedded capacitor materials are high dielectric constant, low capacitor tolerance, good processibility and low cost. BaTiO3-filled epoxy composite is a promising material to meet the above requirements. It utilizes the high dielectric constant of ceramic powders and processibility of polymers. The dielectric behavior of the composite is influenced by the crystal phase type, grain size and dispersability of the BaTiO3 particles distributing in it. In this study, nano-sized BaTiO3 powders have been synthesized with a modified hydrothermal reaction method. The powers possess tetragonal crystal phase with a narrow size range around 50nm. The dielectric constant of the epoxy filled with BaTiO3 is 19.4 at the frequency of 10 kHz when the loading of BaTiO3 was 50 vol% and the dielectric loss factor tanδ is about 0.02. It is believed that the high dielectric constant and low loss are attributed to the pure tetragonal phase and good dispersing of the nano particles.

Investigating the mechanism of catalytic reduction of silver nitrate on the surface of barium titanate at room temperature: oxygen vacancies play a key role

In this study, the formation mechanism of Ag nanoparticles deposited on Barium Titanate (BT) surface was investigated. The surface oxygen vacancies of BT linked with the hydroxyl oxygen of ethylene glycol and catalyzed the reduction of silver nitrate, leading to promoted deposition of Ag nano particles on the BT surface.

ZnO-decorated carbon nanotube hybrids as fillers leading to reversible nonlinear I-V behavior of polymer composites for device protection

Overvoltage protection is becoming increasingly important because of miniaturization and multifunctionality of electronic devices. Flexible, easily processable materials with nonlinear and reversible I-V behavior are highly desired. In this study, hybrid nanoparticles of ZnO-decorated carbon nanotubes (CNT-ZnO) were synthesized via a sol-gel hydrothermal process employed in an epoxy matrix to prepare composites. Microstructure analysis demonstrated that ZnO nanoparticles were well-bonded to the surface of CNT. The CNT-ZnO/epoxy composites exhibited nonlinear I-V behavior under increasingly applied voltage with a nonlinear coefficient of 5.01 (10 wt % filler loading). More importantly, the composites possessed excellent reversibility from dielectric to conductor and vise versa in the recycling of increase and decrease of applied electric field, in contrast to the poor recoverability of pure CNT-filled epoxy. The mechanism of the nonlinear I-V behavior and reversibility was investigated and discussed. A simple circuit was fabricated, which verified well the protection function of the CNT-ZnO/polymer composites.

Dielectric properties of Ag@SiO 2 /epoxy composite for embedded capacitor applications

Nano-sized Ag particles were prepared through a wet chemical reduction route and treated with tetraethoxysilane (TEOS) to form an amorphous SiO2 thin layer on the particles surface (Ag@SiO2). Ag@SiO2/Epoxy composite film was fabricated via coating process. The experimental results showed that the dielectric constant k increased gradually with Ag@SiO2 content before reaching the percolation threshold. The value of dielectric constant k was 28 at 100 Hz for the composite containing 20 vol% Ag@SiO2, which was 5 times larger than that of the pure epoxy resin. In contrast, the value of loss tanδ remained at a low level (<0.02) before reaching the threshold. Tanδ was 0.014 for the composite containing 20 vol% Ag@SiO2, which was even lower than that of the pure epoxy resin (0.018). When the Ag@SiO2 content reached 25 vol%, both of the k and tanδ values increased substantially, indicating formation of conducting pathway between Ag particles. The results implied that when Ag@SiO2 content was at a low level, the insulating SiO2 shell served as electrons barrier layer between Ag cores and prevented electrons from transferring from one Ag core to another under an external field. As a result, the measured k value increased with Ag@SiO2 content, while the tanδ remained low. However, when Ag@SiO2 filler loading reached a higher level and was in the vicinity of critical concentration, Ag cores was so close to each other and the conducting pathway could be developed in the amorphous SiO2 shell, leading to remarkable growth of k and tanδ.