Vibration induced refrigeration using ferroelectric materials.

This article aims to propose a cantilever based cooling device employing non-axis symmetric placement of bulk ferroelectric patches. Ambient mechanical vibrations produce large stresses in cantilevers resulting in elastocaloric effect associated with ferroelectrics. Further, design allows cascading of several cantilevers to achieve large cooling response. A finite element analysis of the system was performed using material properties of bulk 0.50Ba(Zr0.2Ti0.8)O3-0.50(Ba0.7Ca0.3)TiO3. An individual element could produce a peak elastocaloric effect of 0.02 K (324 K); whereas the proposed system could achieve a temperature drop of 0.2 K within 50 seconds (10 elements, 1.5 Hz). Furthermore, net cooling can be further improved about ~2 K (using 10 cantilevers) for a starting temperature of 358 K. This study shows that elastocaloric effect in ferroelectric materials is capable of converting waste mechanical vibration into refrigeration effect which is not reported so far

Negative Poisson’s ratio polyethylene matrix and 0.5BaCa0.8Zr0.2O3-0.5Ba0.7Ca0.3TiO3 based piezocomposite for sensing and energy harvesting applications

Abstract Finite element studies were conducted on 0.5Ba(Zr0.2 Ti0.8) O3–0.5(Ba0.7 Ca0.3)TiO3 (BCZT) piezoelectric particles embedded in polyethylene matrix to create a piezocomposite having a positive and negative Poisson's ratio of −0.32 and 0.2. Polyethylene with a positive Poisson's ratio is referred to as non-auxetic while those with negative Poisson's ratio are referred to as auxetic or inherently auxetic. The effective elastic and piezoelectric properties were calculated at volume fractions of (4%, 8% to 24%) to study their sensing and harvesting performance. This study compared lead-free auxetic 0–3 piezocomposite for sensing and energy harvesting with non-auxetic one. Inherently auxetic piezocomposites have been studied for their elastic and piezoelectric properties and improved mechanical coupling, but their sensing and energy harvesting capabilities and behavior patterns have not been explored in previous literatures. The effect of Poisson's ratio ranging between −0.9 to 0.4 on the sensing and energy harvesting performance of an inherently auxetic lead free piezocomposite composite with BCZT inclusions has also not been studied before, motivating the author to conduct the present study. Auxetic piezocomposite demonstrated an overall improvement in performance in terms of higher sensing voltage and harvested power. The study was repeated at a constant volume fraction of 24% for a range of Poisson's ratio varied between −0.9 to 0.4. Enhanced performance was observed at the extreme negative end of the Poisson's ratio spectrum. This paper demonstrates the potential improvements by exploiting auxetic matrices in future piezocomposite sensors and energy harvesters

Nonlinear characterization of a bistable energy harvester dynamical system

International audienceThis chapter explores the nonlinear dynamics of a piezo-magneto-elastic bistable energy device system regards the influence of external forcing parameters influence on system response. Time series, Poincaré maps, phase space trajectories, and bifurcation diagrams are employed in order to reveals system dynamics complexity and nonlinear effects, such as chaos incidence and hysteresis

Finite element analysis of vibration energy harvesting using lead-free piezoelectric materials: A comparative study

In this article, the performance of various piezoelectric materials is simulated for the unimorph cantilever-type piezoelectric energy harvester. The finite element method (FEM) is used to model the piezolaminated unimorph cantilever structure. The first-order shear deformation theory (FSDT) and linear piezoelectric theory are implemented in finite element simulations. The genetic algorithm (GA) optimization approach is carried out to optimize the structural parameters of mechanical energy-based energy harvester for maximum power density and power output. The numerical simulation demonstrates the performance of lead-free piezoelectric materials in unimorph cantilever-based energy harvester. The lead-free piezoelectric material K0.5Na0.5NbO3-LiSbO3-CaTiO3 (2 wt.%) has demonstrated maximum mean power and maximum mean power density for piezoelectric energy harvester in the ambient frequency range of 90–110 Hz. Overall, the lead-free piezoelectric materials of K0.5Na0.5NbO3-LiSbO3 (KNN-LS) family have shown better performance than the conventional lead-based piezoelectric material lead zirconate titanate (PZT) in the context of piezoelectric energy harvesting devices

Mechanochemical Synthesis of Bi2VO5.5 for Improved Photocatalytic Dye Degradation

Abstract A single‐phase Bi2VO5.5 powder is formed effectively through a mechanochemical ball milling approach at 650 °C in 5 h and its photocatalytic performance on methylene blue dye is explored. X‐ray diffraction and Raman spectroscopy analytical instruments are utilized to confirm the phase formation. The evident presence of irregular‐shaped grains is affirmed using a scanning electron microscope. To ascertain the chemical condition of the components present, the Bi2VO5.5 powdered sample undergo an X‐Ray photoelectron spectroscopy investigation. The sample is analyzed using a time‐dependent photocurrent to discern its charge carrier transportation behavior. A photocatalytic study using Bi2VO5.5 powder produced through the mechanochemical ball milling method has not been explored till now. The efficacy of the ball‐milled Bi2VO5.5 powder to attain enhanced photocatalytic efficiency which hasn't been investigated till now, is explored. The ball‐milled Bi2VO5.5 sample achieved 70% degradation efficiency when performing the photocatalysis investigation. The photocatalytic dye degradation discerns pseudo‐first‐order kinetics and achieves a notable k value of 0.00636 min−1. The scavenger test indicates that h+ radicals are the prominent active species during the photocatalysis experiment. The germination index is determined by conducting a phytotoxicity test with the use of Vigna radiata seeds. Here ball‐milled Bi2VO5.5 powder attains enhanced dye degradation efficiency

Pyroelectric energy conversion using Ba₀.₈₅Sr₀.₁₅Zr₀.₁Ti₀.₉O₃ ceramics and its cement-based composites

In this article, we focus on cement-binded Ba₀.₈₅Sr₀.₁₅Zr₀.₁Ti₀.₉O₃ ceramics for pyroelectric applications. It was prepared with the Ba₀.₈₅Sr₀.₁₅Zr₀.₁Ti₀.₉O₃ -to-cement ratios of 85%:15% and 80%:20% by weight. In order to improve the effectiveness of thermal-to-electric energy conversion, the synchronized switch harvesting on inductor technique is experimentally tested on cement composites. Our experimental findings reveal that this concept based on synchronized switch harvesting on inductor can significantly increase the amount of power extracted from pyroelectric materials. Furthermore, the optimized power across 15% and 20% cement composites were found to be 7.2 and 6 nW, respectively, in series synchronized switch harvesting on inductor and 8.5 and 7 nW, respectively, in parallel synchronized switch harvesting on inductor. These values are significantly higher when compared with non-switched circuit for pyroelectric applications. Although, from the obtained results for the prepared composites, the power output is less when compared with pure Ba₀.₈₅Sr₀.₁₅Zr₀.₁Ti₀.₉O₃, they have some advantages: these composites can be made without any sintering process and are compatible for structural applications

Piezoelectric materials selection for sensor applications using finite element and multiple attribute decision-making approaches

This paper examines the selection and performance evaluation of a variety of piezoelectric materials for cantilever-based sensor applications. The finite element analysis method is implemented to evaluate the relative importance of materials properties such as Young's Modulus (E), piezoelectric stress constants (e31), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based sensor applications. An analytic hierarchy process (AHP) is used to assign weights to the properties that are studied for the sensor structure under study. A technique for order preference by similarity to ideal solution (TOPSIS) is used to rank the performance of the piezoelectric materials in the context of sensor voltage outputs. The ranking achieved by the TOPSIS analysis is in good agreement with the results obtained from finite element method simulation. The numerical simulations show that K0.5Na0.5NbO3–LiSbO3 (KNN–LS) materials family is important for sensor application. Young's modulus (E) is most influencing material's property followed by piezoelectric constant (e31), dielectric constant (ε) and Poisson's ratio (υ) for cantilever-based piezoelectric sensor applications

Functionally Graded Piezoelectric Energy Harvester: A Numerical Study

The performance of linear energy harvesters is primarily confined to a very narrow operating frequency bandwidth around its natural frequency. Even a slight deviation of the excitation frequency from the fundamental frequency of the system tremendously reduces the harvester’s performance. In order to minimize this shortcoming, the presented study considers the piezoelectric energy harvester with magnets introducing non-linearity in the system. The simple harmonic balance method is used to solve the non-linearity and for computing the voltage output and power in the frequency domain. In addition, the study also incorporates the functionally graded piezoelectric materials because of their superior properties. The distance between magnets (d0) has been varied from 0.4 mm to 10 mm along with grading index (n) in the range of 0 to ∞. Finally, voltage and power across the resistance were computed. The effective harvesting frequency range for d0 = 0.4 mm and n = 1 is observed in the range of 20 Hz to 85 Hz, while it was only between 35 Hz and 65 Hz for d0 = 10 mm, yielding a 216% increase in the frequency bandwidth. Under different case studies, the peak output power varied from 2 mW (d0 = 0.4 mm and n = ∞) to 6 mW (d0 = 10 mm and n = 0)

Piezo-photocatalytic activity of Bi2VO5.5 for methylene blue dye degradation

This study comprises the combined effect of piezocatalytic and photocatalytic activity to obtain improved piezo-photocatalytic dye degradation efficiency in visible light. Single-phase Bi2VO5.5 powder was prepared through solid-state synthesis at 750 °C in 8 h. Time-dependent photocurrent responses were conducted to understand the phenomenon of charge carrier transport in visible light. Bi2VO5.5 powder sample demonstrated high photocatalytic efficiency and good reusability possessing a bandgap value of 2.13 eV. Bi2VO5.5 powder sample attained ∼70% and ∼58% degradation efficiency during photocatalysis and piezocatalysis respectively. The piezo-photocatalytic methylene blue dye attained ∼82% degradation efficiency in 240 min duration of visible light illumination. The scavenger test depicted holes (h+) as the principal active species in the piezo-photocatalytic dye degradation. There incurred no severe loss in photocatalytic efficiency even after 4 cycles which proclaims the reusability of the Bi2VO5.5 powder sample. A study on the kinetic rate constant with varying dye concentrations was conducted. With varied dye concentration of 5, 10, 15 mg/L, the kinetic rate constant obtained was 0.00528, 0.0030, and 0.00125 min−1, respectively. Germination index was found through a phytotoxicity test using vigna radiata seeds. Here visible light along with mechanical energy has been used to achieve higher MB dye degradation efficiency through piezo-photocatalysis