R. L. Hadimani

An investigation of energy harvesting from renewable sources with PVDF and PZT

Piezoelectric materials have been in use for many years; however, with an increasing concern about global warming, piezoelectricity has gained significant importance in research and development for extracting energy from the environment. In this work the voltage responses of ceramic based piezoelectric fibre composite structures (PFCs) and polymer based piezoelectric strips, PVDF (polyvinylidene fluoride), were evaluated when subjected to various wind speeds and water droplets in order to investigate the possibility of energy generation from these two natural renewable energy sources for utilization in low power electronic devices. The effects of material dimensions, drop mass, releasing height of the drops and wind speed on the voltage output were studied and the power was calculated. This work showed that piezoelectric polymer materials can generate higher voltage/power than ceramic based piezoelectric materials and it was proved that producing energy from renewable sources such as rain drops and wind is possible by using piezoelectric polymer materials.

Novel “3-D spacer” all fibre piezoelectric textiles for energy harvesting applications

The piezoelectric effect in poly(vinylidene fluoride), PVDF, was discovered over four decades ago and since then, significant work has been carried out aiming at the production of high β-phase fibres and their integration into fabric structures for energy harvesting. However, little work has been done in the area of production of “true piezoelectric fabric structures” based on flexible polymeric materials such as PVDF. In this work, we demonstrate “3D spacer” technology based all-fibre piezoelectric fabrics as power generators and energy harvesters. The knitted single-structure piezoelectric generator consists of high β-phase (∼80%) piezoelectric PVDF monofilaments as the spacer yarn interconnected between silver (Ag) coated polyamide multifilament yarn layers acting as the top and bottom electrodes. The novel and unique textile structure provides an output power density in the range of 1.10–5.10 μW cm−2 at applied impact pressures in the range of 0.02–0.10 MPa, thus providing significantly higher power outputs and efficiencies over the existing 2D woven and nonwoven piezoelectric structures. The high energy efficiency, mechanical durability and comfort of the soft, flexible and all-fibre based power generator are highly attractive for a variety of potential applications such as wearable electronic systems and energy harvesters charged from the ambient environment or by human movement.

Continuous production of piezoelectric PVDF fibre for e-textile applications

Polymers have been widely used as piezoelectric materials in the form of films and bulk materials but there are limited publications on piezoelectric fibre structures. In this paper the process of preparing piezoelectric polyvinylidene fluoride (PVDF) fibres from granules by continuous melt extrusion and in-line poling is reported for the first time. The poling of PVDF fibres was carried out at an extension ratio of 4:1, a temperature of 80 C and a high voltage of the order of 13 000 V on a 0.5 mm diameter fibre in a melt extruder. The entire process of making PVDF fibres from granules and poling them to make piezoelectric fibres was carried out in a continuous process using a customized melt extruder. The prepared piezoelectric fibres were then tested using an impact test rig to show the generation of voltage upon application of an impact load. PVDF granules, unpoled fibres and poled fibres were examined by Fourier transform infrared spectroscopy (FTIR) which showed the presence of phase in the poled fibres. The ultimate tensile stress and strain, Young’s modulus and microstructures of poled and unpoled fibres were investigated using a scanning electron microscope (SEM). (Some figures may appear in colour only in the online journal)

Structural, magnetic, and magnetoelastic properties of magnesium substituted cobalt ferrite

The effects of substituting Mg on the structural, magnetic, and magnetostrictive properties of cobalt ferrite have been investigated. Comparable values of lattice parameter were obtained for the Mg-substituted samples. Saturation magnetization continuously decreased with increase in Mg concentration. Peak-to-peak magnetostriction amplitude and strain sensitivity had a similar dependence on Mg concentration.

Estimation of second order phase transition temperature of the orthorhombic phase of Gd5(SixGe1−x)4 using Arrott plots

Gd5(SixGe1−x)4 for 0.41 ⩽ x ⩽ 0.5 is orthorhombic and ferromagnetic at lower temperature, monoclinic and paramagnetic at higher temperature, and shows a first order magnetic-structural phase transition between the two. Magnetic moment versus magnetic field (MH) isotherms were measured just above the first order transition temperature for Gd5Si1.95Ge2.05 and Gd5Si2Ge2 samples and the field-induced coupled phase transition from paramagnetic/monoclinic to ferromagnetic/orthorhombic phase was observed. Using the method developed by Arrott [Phys. Rev. 108, 1394 (1957) ], the ferromagnetic portions of the MH isotherms were used to project the second order magnetic phase transition temperature of the orthorhombic phase, a region where the transition does not occur due to the first order transition at a lower temperature. These data points fall on the extrapolated line of the second order phase transition, drawn from the Si-rich region of the phase diagram.

Smart Woven Fabrics In Renewable Energy Generation

Initially, the first purpose of fabric making was only for covering the body and sheltering. However, with a growing population and ever improving advanced technologies, today’s fabrics are mostly used for fashion and performance thus enhancing the standard of people’s everyday life and enjoyment. Most of the technologies which increase the standard of living also increase carbon emission and adversely affect human life indirectly. Warming buildings, using cars, provide hot water, cooking food etc. need energy generated by using coal, gas, fuel or electricity. Burning gas and fuel accelerate the threat of nature and eventually contribute to global warming. Even electricity generation causes carbon emission unless it is generated by using renewable energy sources. Interest in providing renewable usable electrical power from the environment has grown, particularly in the elimination of battery usage, because of their sizeable dimensions, weight and limited lifetime. Since global warming is being considered as the biggest danger for the nature, many scientists and researchers have brought a new breath to their researches. As almost all areas of renewable science and technology, researchers are now working in the field of textile fabrics capable of generating green electricity. Undoubtedly, weaving is the oldest fabric making method which has been a part of human life for protection from nature’s elements and hazards. It is now possible to produce smart woven fabrics by combining the oldest fabric making method with smart fibre material technologies. The chapter named “Smart Woven Fabrics in Renewable Energy Generation“ contains a brief introduction to smart materials, focusing on piezoelectricity and polymer based piezoelectric fibre production. The rest of the chapter explains how to produce smart woven structures by integrating smart fibres into the fabric during weaving process and examples for possible applications for energy regeneration from nature’s elements are given.

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models

Transcranial magnetic stimulation (TMS) offers the possibility of non-invasive treatment of brain disorders in humans. Studies on animals can allow rapid progress of the research including exploring a variety of different treatment conditions. Numerical calculations using animal models are needed to help design suitable TMS coils for use in animal experiments, in particular, to estimate the electric field induced in animal brains. In this paper, we have implemented a high-resolution anatomical MRI-derived mouse model consisting of 50 tissue types to accurately calculate induced electric field in the mouse brain. Magnetic field measurements have been performed on the surface of the coil and compared with the calculations in order to validate the calculated magnetic and induced electric fields in the brain. Results show how the induced electric field is distributed in a mouse brain and allow investigation of how this could be improved for TMS studies using mice. The findings have important implications in f...

Gd5(Si,Ge)4 thin film displaying large magnetocaloric and strain effects due to magnetostructural transition

Magnetic refrigeration based on the magnetocaloric effect is one of the best alternatives to compete with vapor-compression technology. Despite being already in its technology transfer stage, there is still room for optimization, namely, on the magnetic responses of the magnetocaloric material. In parallel, the demand for different magnetostrictive materials has been greatly enhanced due to the wide and innovative range of technologies that emerged in the last years (from structural evaluation to straintronics fields). In particular, the Gd5(SixGe1−x)4 compounds are a family of well-known alloys that present both giant magnetocaloric and colossal magnetostriction effects. Despite their remarkable properties, very few reports have been dedicated to the nanostructuring of these materials: here, we report a ∼800 nm Gd5Si2.7Ge1.3 thin film. The magnetic and structural investigation revealed that the film undergoes a first order magnetostructural transition and as a consequence exhibits large magnetocaloric ef...

Evolution of Griffith's phase in La0.4Bi0.6Mn1−xTixO3 perovskite oxide

Samples of La0.4Bi0.6Mn1−xTixO3 have been prepared and their microstructure, composition, and magnetic properties have been investigated for x = 0.05, 0.1, and 0.5.The deviation in the inverse susceptibility behavior from Curie-Weiss law and increase in susceptibility exponent indicates the evolution of the Griffiths phase in La0.4Bi0.6Mn1−xTixO3 around TC. The presence of Griffiths Phase is inferred due to magnetic frustration with increasing Ti concentration. The deviation between field cooled and zero field cooled magnetization curves is observed in these samples and is attributed to the appearance of the spin glass or cluster glass state that arises due to the magnetic anisotropy.

Field induced structural phase transition at temperatures above the Curie point in Gd5(SixGe1-x)4

Gd5(SixGe1−x)4 exhibits a field induced first order phase transition from a monoclinic paramagnetic to an orthorhombic ferromagnetic at temperatures above its Curie temperature for 0.41 ≤ x ≤ 0.51. The field required to induce the transition increases with temperature. This field induced first order phase transition was observed even above the projected second order phase transition temperature of the orthorhombic phase. This may be due to the fact that the applied magnetic field is so high that it causes the broadening to a wider range of higher temperatures of the second order phase transition of the orthorhombic phase, and at such high magnetic fields the magnetic moment is still quite large, therefore, causing the transition. This hypothesis seems to be confirmed by the various magnetic moment versus magnetic field, magnetic moment versus temperature, and strain versus magnetic field measurements carried out on single crystal Gd5Si1.95Ge2.05 and Gd5Si2Ge2 samples at magnetic fields of 0–9 T and at temperatures of 265–305 K.