Browsing by Author "Mahendran, A.R."

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A study on electroactive PVDF/mica nanosheet composites with an enhanced ?-phase for capacitive and piezoelectric force sensing
(Royal Society of Chemistry, 2021) Khalifa, M.; Schoeffmann, E.; Lammer, H.; Mahendran, A.R.; Wuzella, G.; Anandhan, S.
Herein, a multifunctional poly(vinylidene fluoride) (PVDF)/mica nanosheet composite (PMNC) thin film was developed for preparing a capacitive and piezoelectric force sensor. A high electroactive ?-phase content (89%) of PVDF was achieved through a facile rapid cooling process of PMNC films. The crystallinity of PVDF decreased upon the addition of mica nanosheets, while the dielectric constant increased significantly (?300%). The capacitance-based PMNC pressure sensor was found to be sensitive to the applied pressure. On the other hand, piezoelectric voltages of 18 V (single layer) and 32 V (multi-layer) were generated for PMNCs loaded with 1% mica nanosheets. Furthermore, a PMNC based nanogenerator generated a power density of 8.8 ?W cm?2and showed excellent durability (>60?000 cycles). High flexibility, lightweight and skin-friendly PMNCs could be a potential material in applications such as energy harvesting, energy storage, actuators, and self-powered and smart wearable electronic devices. © The Royal Society of Chemistry 2021.
Development of a new flexible nanogenerator from electrospun nanofabric based on PVDF/talc nanosheet composites
(Royal Society of Chemistry, 2020) Shetty, S.; Mahendran, A.R.; Anandhan, S.
Herein, a flexible piezoelectric nanogenerator composed of electrospun talc/PVDF [poly(vinylidene fluoride)] nanocomposite fabrics has been developed. These nanocomposite fabrics demonstrated enhanced mechanical and piezoelectric properties compared with pristine PVDF nanofabrics. In particular, nanocomposite fabrics with 0.50 wt% talc yielded 89.6% of polar ?-phase in the PVDF matrix, thereby augmenting its piezoelectric response. X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry conclusively affirmed the promotion of polar ?-phase in the talc/PVDF nanocomposite fabrics. The 0.50 wt% talc/PVDF nanocomposite fabric based nanogenerator produced an open-circuit voltage and power density of 9.1 V and 1.12 ?W cm-2, respectively, under repetitive finger tapping mode (under a load of 3.8 N). Furthermore, the nanogenerator was also subjected to frequency modulated-shaker mode, wherein an output voltage of 8.9 V was produced. Improved flexibility, mechanical robustness, and enhanced piezoelectric responsiveness of this nanogenerator could possibly pave the way for its use in portable self-powered devices. This journal is © 2020 The Royal Society of Chemistry.
Effect of polarization switching on piezoelectric and dielectric performance of electrospun nanofabrics of poly(vinylidene fluoride)/Ca–Al LDH nanocomposite
(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Shamitha, C.; Mahendran, A.R.; Anandhan, S.
At present, highly flexible, durable, and lightweight piezoelectric nanogenerators with high-power density and energy conversion efficiency are of great interest. The present study reports a new synthetic route for Ca–Al layered double hydroxide (LDH) nanosheets and incorporation of these two-dimensional nanosheets as filler material into poly(vinylidene fluoride) (PVDF) to produce composite nanofabrics by electrospinning. The polymorphism, crystallinity, and the interaction between PVDF and LDH were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry techniques. The synergetic effect of PVDF–LDH interaction and in situ stretching due to electrospinning facilitates the nucleation of electroactive ? phase up to 82.79%, which makes it a suitable material for piezoelectric-based nanogenerators. The piezoelectric performance of PVDF/Ca–Al LDH composite nanofabrics was demonstrated by hand slapping and frequency-dependent mechanical vibration mode, which delivered a maximum open circuit output voltage of 4.1 and 5.72 V, respectively. Moreover, the composite nanofabrics exhibited a high dielectric constant and low dielectric loss due to superior interfacial polarization at low-frequency region with LDH loading, promising its potential applications in electronic devices. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48697. © 2019 Wiley Periodicals, Inc.
Extruded poly(ethylene-co-octene)/fly ash composites - Value added products from an environmental pollutant
(2012) Anandhan, S.; Sundar, S.M.; Senthil, T.; Mahendran, A.R.; Shibulal, G.S.
Fly ash (FA) is a by-product generated during combustion of coal and has caused serious environmental concerns. In an effort to utilize FA beneficially, we developed composites from an ethylene-octene random copolymer (EOC) and unmodified as well as surfacemodified class-F fly ash (MFA) by twin screw extrusion. Addition of 20 wt% of MFA to EOC improves its tensile strength by 150%; also, MFA improves stress at 100% and 300% strains (M100 and M300) of EOC. Thermal stability of EOC matrix is appreciably improved by the addition of either FA or MFA, while the melting behavior is not appreciably influenced by either. Fractography study reveals an improved adhesion between the EOC and MFA particles up to a filler loading of 20%, beyond which the adhesion between EOC and MFA is weakened causing a reduction in mechanical properties. The 'flammable' nature of EOC changes to 'self extinguishing' on addition of even 10 wt% of FA or MFA, as found out from LOI study. Springer Science+Business Media B.V. 2012.
Extruded poly(ethylene-co-octene)/fly ash composites - Value added products from an environmental pollutant
(Kluwer Academic Publishers, 2012) Anandhan, S.; Sundar, S.M.; Senthil, T.; Mahendran, A.R.; Shibulal, G.S.
Fly ash (FA) is a by-product generated during combustion of coal and has caused serious environmental concerns. In an effort to utilize FA beneficially, we developed composites from an ethylene-octene random copolymer (EOC) and unmodified as well as surfacemodified class-F fly ash (MFA) by twin screw extrusion. Addition of 20 wt% of MFA to EOC improves its tensile strength by 150%; also, MFA improves stress at 100% and 300% strains (M100 and M300) of EOC. Thermal stability of EOC matrix is appreciably improved by the addition of either FA or MFA, while the melting behavior is not appreciably influenced by either. Fractography study reveals an improved adhesion between the EOC and MFA particles up to a filler loading of 20%, beyond which the adhesion between EOC and MFA is weakened causing a reduction in mechanical properties. The 'flammable' nature of EOC changes to 'self extinguishing' on addition of even 10 wt% of FA or MFA, as found out from LOI study. © Springer Science+Business Media B.V. 2012.
Influence of multiwalled carbon nanotubes on the structure and properties of poly(ethylene-co-vinyl acetate-co-carbon monoxide) nanocomposites
(John Wiley and Sons Inc, 2021) George, G.; Mahendran, A.R.; SelvaKumar, S.; Anandhan, S.
In this work, composites of poly(ethylene-co-vinyl acetate-co-carbon monoxide) (EVACO)/surface-modified multiwalled carbon nanotubes (m-MWCNTs) were prepared using a solution casting technique. Acid treatment was employed for the surface modification of MWCNTs to improve the compatibility between polar EVACO and MWCNTs. The influences of m-MWCNTs on the crystalline, mechanical, thermal, and electrical properties of EVACO at very low filler loading were systematically evaluated. The presence of m-MWCNTs in the EVACO matrix influenced the crystallinity, and the respective changes were determined and quantified using dynamic scanning calorimetry and X-ray diffraction. The mechanical properties of the composites were improved remarkably by the addition of a minute quantity (0.05, 0.1, 0.15, 0.2, and 0.25 wt%) of m-MWCNTs. Additionally, m-MWCNTs in the EVACO matrix improved the thermal stability and electrical properties of EVACO. However, the filler loading is below the threshold loading of the fillers, and there was no drastic improvement in the electrical conductivity of the composite. © 2021 Society of Plastics Engineers.
Physicochemical characteristics of bio-based thermoplastic polyurethane/graphene nanocomposite for piezoresistive strain sensor
(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Khalifa, M.; Ekbote, G.S.; Anandhan, S.; Wuzella, G.; Lammer, H.; Mahendran, A.R.
Herein, we report the physicochemical characteristics and piezoresistive strain sensing performance of flexible thin film comprising graphene and bio-based thermoplastic polyurethane (TPU) prepared by solution cast method. A detailed analysis was carried to study the influence of graphene nanoplatelets on the morphological, thermal, mechanical, and electrical properties of TPU nanocomposite. Upon increasing the graphene nanoplatelets loading, the thermal stability and tensile properties improved remarkably, while glass transition temperature decreased slightly. Owing to better dispersion of graphene, the electrical conductivity was significantly increased, which broaden the utilization of the nanocomposite for various applications. The piezoresistive sensor was able to respond to various stress modes such as tapping, bending, and finger touch. The piezoresistive sensor was sensitive and achieved a gauge factor of 11. Sensor attached to finger, showed distinctive response upon bending at different angles and showed high stability and reproducibility even after >10,000 cycles under repetitive constant load. Also, the nanocomposite was able to detect any breakage or fracture in the form of change in electrical resistance. A combination of bio-based TPU and graphene offered improved physical properties and high sensing performance, which could be a potential material in flexible electronics and structural health monitoring systems. © 2020 Wiley Periodicals, Inc.