Improved dielectric and touch sensing performance of surface modified zinc ferrite (ZF)/Polyvinylidene fluoride (PVDF) composite

The continuous demand of fabricating self-powered body implantable devices have raised the development of new lead free polymer-ceramic composites. Herein, we have fabricated Zinc Ferrite (ZF)/Polyvinylidene Fluoride (PVDF) composite by simple solution casting technique. The inherent difficulty of compatibility between two phases (polymer and ceramic) for homogeneous film was addressed by addition of two different modifiers: Sodium dodecyl sulphate (SDS) and Tetraethyl orthosilicate (TEOS). Similarity in the piezo/ferro electrical properties between the externally poled unmodified nanocomposite with that of the surface modified composites were observed which were basically attributed to higher dispersion of nanoparticles in the polymer matrix and improved interfacial interaction between organic and inorganic matrix. It indicates that a self polarization effect has been induced in the surface modified composites. The mechanism for the interaction between two phases was discussed on the basis of zeta potential results and spectroscopic analysis. Further, external poled MSDS-ZF(C)-PVDF composite offered the highest energy storage density (0.25 Jcm(-3)), whereas poled TEOS modified ZF-PVDF composite exhibited an output open circuit voltage of 2.2 V with power density of 3.7 mu Wcm(-3) under repeated single finger touch. (c) 2017 Elsevier B.V. All rights reserved

Surface Modified Zinc Ferrite (ZF) / Polyvinylidene fluoride (PVDF) Nanocomposite: A Novel Material for Application as a Flexible Energy Harvester

A simple cost effective method to enhance the electroactive phase of PVDF by developing nanocomposite with surface modified ascorbic acid assisted phase pure Zinc Ferrite (ZF(ASC)) has been demonstrated. High energy storage density (0.271 J/cm(3)) and piezoelectric energy harvesting performance (similar to 2.20 V output voltage with single finger impact of human touch) was obtained after polling 1.5 wt% surface modified Zinc Ferrite nanoparticle loaded nanocomposite. There is a possibility of transformation of nonpolar phase to electroactive phase in PVDF which has occurred due to the orientation effect of -CH2 bond in PVDF over the surface modified nanoparticle. (C) 2017 Elsevier Ltd. All rights reserved

Influence of nanoparticle size on nucleation of electroactive phase and energy storage behaviour of zinc ferrite/ poly(vinylidene fluoride) nanocomposite

The incorporation of different size of nanoparticles in polymer matrix plays a dominating role in determining the overall structural, microstructural and electrical properties of the fabricated composites. In this paper, an investigation was done in order to establish the effect of incorporating different size of zinc ferrite (ZF) nanoparticles in poly(vinylidene fluoride) (PVDF) matrix. The incorporated spherical ZF nanoparticle induced nucleation of electroactive phases in PVDF matrix by means of electrostatic interaction between the surface charge of the filler and the dipoles of PVDF. The fraction of nucleated electroactive phases is strongly dependent on the size of the nanoparticles. There is a critical size of the nanoparticle, below which the nucleation efficiency of the filler diminishes as it may be swelled by the polymer macromolecules. On the other hand, if the filler size is too large, there is a possibility of formation of mixed conformation of polar and nonpolar phase. Further, this behaviour was correlated with the electrical response of composite where nanoparticle with the critical radius incorporated PVDF composite, exhibited maximum dielectric and ferroelectric property. Finally, a number of participating dipoles of polymer chain interact with ZF nanoparticle of different size were calculated by a model analysis and were represented schematically

Flexible, hybrid nanogenerator based on Zinc Ferrite nanorods incorporated poly(vinylidene fluoride-co-hexafluoropropylene) nanocomposite for versatile mechanical energy harvesting

Herein, an efficient, low-cost, scalable in-situ poled fabrication strategy to construct a large area, highly sensitive, flexible piezocomposite nanogenerator comprising of rod shaped Zinc Ferrite (ZF-R) and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was developed. ZF-R with an average length of 330 nm was synthesized via a facile two-pot hydrothermal method and its PVDF-HFP-based composites with different weight ratio were prepared. Fabricated 3 wt% ZF-R incorporated PVDF-HFP flexible piezocomposite (3H) was used as an effective nanogenerator which could generate an output voltage of 8.5 V and current density similar to 0.5 mu A/cm(2) upon repetitive mechanical stresses. The generated power could enlighten 21 commercial light emitting diodes (LEDs). Furthermore, 3H demonstrated the capability to monitor height with level of accuracy upto +/- 3 cm. Moreover, this flexible hybrid film can scavenge environmental sensations such as air flow (maximum 3.2 V peak to peak voltage) and muscular vibration when integrated with arm, wrist and finger in conjunction with superior integratebility and nontoxicity. Thus, this nanocomposite can be explored for application as ultrasensitive height monitor, mechanical energy scavenger and effective power source for driving portable electronics and wearable devices

Conducting polyaniline decorated in-situ poled Ferrite nanorod-PVDF based nanocomposite as piezoelectric energy harvester

PVDF-metal oxide based piezo-nanocomposite is an promising substitute of flexible nanogenerator. Herein, a ternary nanocomposite system Zinc Ferrite nanorod/Polyvinylidenefluoride (PVDF)/Polyaniline (PANI) nanochains was presented as alternative energy harvesting material. The inherent problem of low short-circuit current and high internal resistance of the nanocomposite was minimised by introducing a third phase cost-effective conducting supplementary filler, PANI nanochain.PANI assist to overcome the local dielectric dissimilarity by easy formation of conduction pathways via delocalization of pi-electrons present in the benzene ring and reduce the internal resistance of composite. Besides, it serves the role of dispersing agent by floating nanofillers throughout the volume and improves the homogeneity of filler distribution. Additionally, PANI reinforces composite with respect to stress accumulation and modulates the release behaviour by entangling with nanofillers by means of Van Der Waals force and helps to stabilize the polar PVDF. This lead to an improvement in electro-mechanical response and piezo-response behaviour of nanocomposite. The nanocomposite exhibits a similar to 42 V ac open circuit voltage and short circuit current density similar to 0.85 mu A/cm(2) with an overall increase in power density 35% compare to its binary metal-oxide/PVDF nanocomposite counterpart in response to single finger tapping and releasing. The generated power was utilized to illuminate twenty six number of red LEDs without any external energy storage unit. Also, the nanocomposite could charge up a commercial capacitor (10 mu F) within 115 s which can be used for alternative powersource in self-powered devices and sensors. (C) 2019 Published by Elsevier B.V

Enhanced dielectric and energy storage performance of surface treated gallium ferrite/polyvinylidene fluoride nanocomposites

The ceramic-polymer nanocomposites composed of gallium ferrite (GFO) nanoparticles and employing sodium dodecylsulphate (SDS) as surfactant and polyvinylidene fluoride (PVDF) as matrix have been fabricated by solvent casting followed by hot-press technique. It was found that modified GFO nanoparticles favours nucleation and stabilization up to similar to 84% electroactive phase (b-and g-phase) in PVDF. Fourier transform infrared spectroscopy (FTIR) results revealed that the interfacial electrostatic interaction between nanoparticle surface charge and CH2/CF2 - molecular dipole of PVDF favoured nucleation of electroactive phase. Compared to the pristine PVDF, much higher dielectric constant (epsilon(r) similar to 25 at 10 kHz frequency) with low loss factor (tan delta similar to 0.02 at 10 kHz) was achieved in the composite film. In addition, the nanocomposite showed higher electrical energy density (U-d similar to 3.88 mJ cm(3) at an electric field 6 kV mm(-1)) compared to pristine PVDF which determined their applicability as flexible energy density capacitor

Polyglycolated zinc ferrite incorporated poly(vinylidene fluoride)(PVDF) composites with enhanced piezoelectric response

Flexible polymer-ceramic nanocomposite films were fabricated using electrostrictive polymer Poly(vinylidene fluoride)(PVDF) as the matrix and Zinc ferrite (ZF) as the filler. ZF has been synthesized with the diameter of 50 nm by sol-gel auto-combustion method and encapsulated with PEG-6000. Both the unmodified and surface modified ZF/PVDF polymer nanocomposite films were fabricated in different weight percentages of ZF by casting method for optimization of maximum dielectric, ferroelectric, piezoelectric performance. The robust PEG layer act as the coupling agent on the interface between organic and inorganic phases and improved Maxwell-Wagner-Sillars interfacial polarization by forming an interaction zone with Gouy-Chapman diffuse layer of polyglycolated ZF. The induced polar phase and dielectric permittivity of the composites was increased after surface modification and meanwhile, the dielectric loss was decreased at a low level. 10 wt% ZF-PEG/PVDF showed the maximum polar phase of similar to 92% with maximum dielectric constant 35 +/- .05. Evaluation of the energy storage capability indicated that surface modification has improved the energy storage density. The maximum energy storage density (4.3 J/cm(3)) was observed for 12 wt% ZF/PEG-PVDF composites with maximum energy discharge efficiency (similar to 83%). Further, this composite exhibited 18 Voc ac touch sensing performance which can be utilized for powering micro watt power consuming sensor devices. (C) 2017 Elsevier B.V. All rights reserved

Synthesis and characterization of transparent erbium-ytterbium co-doped polymer nanocomposites for fabrication of polymer optical preform

Synthesis of polystyrene (PS) and poly (methylmethacrylate) (PMMA)-grafted Er-Yb co-doped transparent ternary nanocomposite is presented herein. Er-Yb co-doped nanoparticles (NP) were synthesized from their nitrate precursors followed by surface modification using 3-methacryloxypropyltrimethoxysilane (MPS) as surfactant. In situ polymerization of methylmethacrylate (MMA) was performed in presence of benzoyl peroxide as initiator in toluene. The synthesized NP-PMMA composite was blended with PS in tetrahydrofuran (THF). Different material characterizations of synthesized composite were performed to evaluate shape, size and chemical nature of developed composite. UV-visible spectra and DLS technique revealed that optimum particle size in the range of 1.5 at 589 nm) and indicate their potential application as active core material for preparation of rare earth doped polymer optical preform (POP). The POF preform prepared using commercially available cladding tube containing Er-Yb transparent polymer nanocomposites as core material is found to have numerical aperture around 0.19. The photoluminescence (PL) spectrum was also measured and intensity of Er-Yb co-doped composite found to be ten times greater than pure Er-doped system. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Flexible piezoelectric energy harvesters using different architectures of ferrite based nanocomposites

Electroactive phase transition in polyvinylidene fluoride (PVDF) can be economically achieved readily by addition of nanofillers. In this work, we have demonstrated the influence of rational design and structural control of nanofillers on nucleation and stabilization of an electroactive polymorph in PVDF. Different architectures of zinc ferrite (ZF) i.e. nearly spherical, nearly cubic, and rod-like were synthesized and further introduced in PVDF as a nucleating agent with different filler to polymer ratios. A comparative study of the dielectric and ferroelectric properties and energy harvesting performance of the corresponding nanocomposite was performed to obtain the best architecture based composite. It has been observed that one dimensional nanofillers are more favorable for polar phase transformation and stabilization with incorporation of a lower fraction of fillers. Thus, they exhibited maximum electrical performance (an energy storage density of 7.68 mJ cm(-3) with an energy discharge efficiency of similar to 77%, and an output piezoresponse of similar to 39.10 V with a power density of 2.96 mu W mm(-3)). This may be due to the preferred ` in-plane' orientation of the nanorod structure in the polymer matrix which helps to accumulate the entire short chain all-trans (TTTT) conformation and form an extended all-trans conformation corresponding to an electroactive ss-polymorph. This study may open a new strategy to design and fabricate ferrite-PVDF based electroactive nanocomposites with desired shapes for high performance energy storage and harvesting application

Development of Polyaniline-Poly(methylmethacrylate) Blend Coated Optical Fiber RI Sensor for Ammonia Detection

Development of polyaniline-poly(methylmethacrylate) blend coated modified-clad optical fiber as refractive index (RI) sensor is presented. This RI sensor exhibit linear optical intensity modulation with increasing ammonia concentration and promising candidate for ammonia detection