MECHANICAL ENERGY HARVESTING POTENTIAL OF BiFeO3-PVDF FLEXIBLE COMPOSITES

Bismuth ferrite (BiFeO3) powders were synthesized by sol-gel methods and incorporated into flexible composites by hot pressing with polyvinylidene fluoride (α-PVDF). Several metal ions with various valances were used to dope BiFeO3 in order to examine their influence on electrical properties. XRD characterization confirmed that almost all of the dopants incorporated very well into the perovskite structure. Microstructural study showed that the composites are homogeneous with thickness of 50 to 140 μm. Dielectric, impedance and ferroelectric properties of composite samples showed that all of the dopants even those with smaller valence than the ions they substitute enhance the capability to handle the electric field. α-PVDF matrix also helped in preventing electrical breakdown comparing to BiFeO3 ceramics, which is usually susceptible to high leakage. Flexible composites were subjected to impact piezoelectric test with the idea to study their potential to collect mechanical energy from the surrounding vibrations

LEAD BASED (PZT) AND LEAD FREE (BZT) COMPOSITES FLEXIBLE FILMS AS LOW-ENERGY PIEZOELECTRIC HARVESTERS

Various alternative renewable sources such as solar, wind, thermal energy and mechanical vibrations are available for the energy generations. For the last decades, energy harvesters based on piezoelectricity from mechanical vibration are explored extensively for its functionality in energy technologies [1,2]. Flexible piezoelectric energy harvesters (FPEHs) and energy storage system were fabricated by employing solid state synthesized lead-free BZT (BaZr0.2Ti0.8O3) and PZT (PbZr0.52Ti0.48O3) nanopowders prepared by autocombustion method with polyvinylidene fluoride (PVDF) in different volume percentage (xBZT/PZT-(1-x)PVDF, x=30, 40, 50). Both flexible films with quite homogeneous distribution of piezo-active filler were confirmed by XRD and SEM analysis. In addition, the remnant polarization (Pr) and dielectric constant are also investigated to evaluate the breakdown strength in flexible films. The improved dielectric loss tangent (< 0.02) and dielectric permittivity of 120 at room temperature and frequency 1 MHz of BZT-PVDF (50- 50) in comparison with neat PVDF films is found beneficial for both energy harvesting and storage. Calculations of storage energies obtained for the investigated materials revealed an increasing trend with increasing amount of active phase (BZT and PZT). The maximum storage energy of 0.11 J/cm3 and 0.13 J/cm3, and energy efficiency (η) of 72% and 39% was obtained for BZT-PVDF (50-50) and PZTPVDF (40-60) films, respectively. Test of the force impact showing similar output voltage of around 4 V for both, BZT and PZT flexible films

TWO-PHASE AND THREE-PHASE FLEXIBLE THICK FILMS: POTENTIAL USE AS ENERGY STORAGE AND ENERGY HARVESTING SYSTEMS

For the last decades, energy harvesters based on piezoelectricity from mechanical vibration (wind, human activities, vibrations of machines and traffic, ocean waves, and acoustic waves) are explored extensively for its functionality in energy technologies. Typical applications that could benefit from mechanical energy harvesting are that many sensors, alarms, LED lights, and other low-power and ultra-low-power devices can be driven energetically completely independently [1]. To fabricate a flexible piezoelectric energy harvester (FPEHs) that operates under various conditions, ceramic particles were blended with a polymer to form composite films. Two-phase lead-free BaZr0.2Ti0.8/PVDF and lead-based PbZr0.52Ti0.48/PVDF piezocomposites, as well as three-phase PbZr0.52Ti0.48/Ni0.7Zn0.3Fe2O4/PVDF composites films with variable filler content (up to 50 vol.%) have been prepared by hot pressing method. Structure and morphology of piezo-active phase powders as well as distribution of filler in obtained flexible films were characterized by XRD and SEM analysis. Total amount of electroactive phase (% FEA) of PVDF in all films were investigated by FTIR analysis. In all composites dielectric permittivities was increased in contrast to their polymer PVDF host matrix, but also displayed decreased breakdown strength and raised energy loss. In addition, the remnant polarization (Pr) and leakage current were also investigated to evaluate the breakdown strength in all types of flexible films. Also, ferromagnetic response was established in PZT/ferrite/PVDF films under magnetic field of 10 kOe. Calculations of storage energies and output voltage obtained for the investigated materials revealed an increasing trend with increasing amount of active phase. The maximum storage energy of 0.42 J/cm3 at 390 kV/cm3 was obtained for PZT-PVDF (40-60) films while the maximum output voltage of about 10 V was obtained for PZT-PVDF (50-50) flexible film. In addition, comparisons between properties of

Lead Free (BaZr0.2Ti0.8O3) and Lead Based (PbZr0.52Ti0.48O3) Flexible Thick Films: Structural Properties and Potential Use as Energy Storage and Energy Harvesting Systems

In the last year energy harvesters based on piezoelectricity from mechanical vibration has emerged as the very promising devices that are explored extensively for its functionality in energy technologies. In this paper a series of flexible lead- free BZT/PVDF and lead based PZT/PVDF piezocomposites with variable filler content up to 50 vol. % have been prepared by hot pressing method. Structure and morphology of BZT and PZT powders as well as distribution of piezo-active filler in obtained flexible films were characterized by XRD and SEM analysis. Total amoun of electro active phase (% FEA) of PVDF is higher in PZT-based films in comparison with BZT based ones but the contribution of more desirable β- phase is higher in BZT-PVDF films. In both composite dielectric permittivity's was increased in contrast to their polymer PVDF host matrix, but also displayed decreased breakdown strenght and raised energy loss. In addition, the remnant polarization (Pr) and leakage current were also investigated to evaluate the breakdown strength in both types of flexible films. Calculations of storage energies and output voltage obtained for the investigated materials revealed an increasing trend with increasing amount of BZT and PZT active phase. The maximum storage energy of 0.42 J/cm3 at 390 kV/cm3 was obtained for PZT-PVDF (40-60) films while the maximum output voltage of about 10 V was obtained for PZT-PVDF (50-50) flexible film. In addition, comparisons between properties of lead based and lead free flexible films as well as potential use of those films as energy storage and energy harvesting systems were considered

Istraživanje stanja i mogućnosti za unapređenje toplotno distributivnog sistema grada Kragujevca

Razvoj toplotno‑distributivnog sistema grada Kragujevca (TDS‑K) sledio je urbanističko, populaciono i privredno napredovanje grada i danas predstavlja, zajedno sa svojim toplotnim izvorištem, jedan od najvrednijih komunalnih infrastrukturnih sistema u Srbiji. Pošto je dinamika razvoja grada, istorijski gledano, bila neujednačena, u današnjoj strukturi TDS‑K uočljive su tehničko‑tehnološke neujednačenosti koje limitiraju dalji razvoj, a ne retko, predstavljaju i smetnju visoko kvalitetnom snabdevanju svih potrošača. Zbog toga su Upravni odbor i poslovodni tim „Energetike“, d.o.o., preduzeća koje brine o razvoju i održavanju TDS‑K, oslanjajući se na snažnu podršku uprave grada Kragujevca, započeli pre dve godine, zajedno sa Regionalnim evrocentrom za energetsku efikasnost Mašinskog fakulteta i preduzećem „Geopremer“ iz Kragujevca, opsežan projekat čiji je cilj da se obezbedi: – precizna elektronska GIS mapa kompletnog TDS‑K; – elektronska baza podataka o svim pogonskim podstrukturama, cevovodima, cevnim armaturama i toplotnim podstanicama; – pouzdan softver za simulaciju ponašanja TDS‑K u različitim režimima eksploatacije, koji se može koristiti i za uvođenje proaktivnog sistema tekućeg i investicionog održavanja, kao i za stvaranje kvalitetnih osnova za dalje širenje i povećanje broja konzumenata usluga „Energetika“ d.o.o.; – kreiranje internet portala za brzu internu i eksternu komunikaciju sa dispečerskim centrom TDS‑K i – definisanje sistema organizacionih i tehničko‑tehnoloških mera za povećanje energetske efikasnosti TDS‑K i smanjivanje troškova u proizvodnji i distribuciji toplotne energije. U ovom radu je ukratko prikazan deo do sada ostvarenih rezultata na napred opisanim poslovima.Publishe

Composite flexible films prepared by hot pressing for low-energy harvesting and storage

The important task of scientific community nowadays is finding the way to use enormous amount of mechanical energy released everywhere around us as a renewable and safe energy source. This research was focused on the preparation of flexible composite films, by combining a highly flexible polyvinylidene fluoride (PVDF) polymer matrix with lead-free piezoelectric perovskites, 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3 (NBT-BT), in different ratios, using the hot pressing method. A crucial point of this investigation is to show that this material is quite versatile and possesses functional properties which are sensitive to both microscopic and chemical modifications. Detailed investigation of processed flexible films led to the main conclusion that electrical properties of these composites can be affected by different factors. Firstly, the hotpressing method itself induces the formation of electroactive β-phase of PVDF polymer, the NBT-BT as filler with negatively charged surface enables a predominant formation of desirable piezoelectric PVDF phase as well and additionally, there is an influence of concentration and type (pre-preparation method) of the added filler. Dielectric permittivity values of composites were up to 110 and highly depend on the filler amount. A very useful zone around room temperature as a plateau with relatively constant dielectric permittivity and losses was noticed in each film`s dielectric spectra. Anelastic measurements have shown a complete agreement with dielectric properties in which the temperature dependence of the Young’s modulus and the losses are dominated by those of the polymer. Regarding the resulting dielectric and ferroeletric properties of the flexible composites, the potential of these materials for the energy storage application was investigated. Energy density efficiencies obtained for investigated materials have shown a decreasing trend with increasing amount of filler with values of 66-74 %. Assembled energy harvesting units were made by proper wiring and covering the flexible film with Kapton protection layer. The obtained output voltage while applying the impact force was from 1 V to 7 V, depending on the type of the flexible film. The main conclusion derived from this study is that composite flexible films made of lead-free NBT-BT filler and PVDF, have high potential to be used for environmentally safe lowenergy storage and energy harvesting devices

Energy Harvesting Potential of Polymer Composites

Energy is available all around us in different forms and shapes such as from sun, wind, waves, vibrations etc. The enormous amount of mechanical energy released in everyday life by human walking, transportation movement, sound waves and other, represent renewable and safe energy source. Piezoelectric generators exhibit a great potential for powering up low-power portable devices and self-powered electronic systems by extraction of mechanical energy. Employment of lead-free piezoelectric materials will be a breakthrough of a completely new type of safe and harmless production of energy for daily life. Recent challenge in electronics is also utilization of flexible electronics with the ability to bend into diverse shapes which expands the applications of modern electronic devices in different areas.Polymer PVDF/piezoelectric ceramics, flexible composite films were prepared by hot pressing method. The influence of hot pressing method on the formation of electroactive PVDF phases in the polymer was proven by FTIR analysis. DSC analysis have shown the change of PVDF crystallinity degree in the flexible films with addition of ceramics filler particles. The dielectric permittivity value increased with the addition of filler in the polymer matrix while the relaxation processes were governed mostly by the PVDF matrix. Polarization of flexible films enhanced the formation of PVDF electroactive β- phase in the samples. Energy harvesting potential was studied by measuring of voltage output under the impulse hammer load

Advantages and limitations of active phase silanization in PVDF composites: Focus on electrical properties and energy harvesting potential

In order to further improve the performance of 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3/ polyvinylidene fluoride (NBT-BT/PVDF) flexible composite films prepared by the hot-pressing method, the effect of surface modification of the NBT-BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3-aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) were added to enhance dispersion and interfacial adhesion of the active phase powder with the polymer matrix. The highest amount of the electroactive PVDF β-phase was formed in APTES-modified samples while in DDTES samples mainly γ-phase was formed as shown by Fourier-transform infrared spectroscopy analysis. Differential scanning calorimetry measurements indicated that the addition of filler particles reduced the total crystallinity degree of the PVDF. Dielectric permittivity values as well as dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES-modified particles led to enhanced breakdown strength of these samples. The highest level of agglomeration in the DDTES-modified samples induced the deterioration of ferroelectric properties. The highest voltage output of 15 V and 225 μW of powerwas obtained for the APTES-modified harvester, evidencing their potential for energy harvesting applications

ENHANCED PROPERTIES OF PVDF COMPOSITES BY ACTIVE PHASE SILANIZATION

0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO3/polyvinylidene fluoride flexible composite films were prepared by the hot-pressing method. Surface modification of active phase particles was performed using two coupling agents, namely, (3- aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) to enable good adhesion of active phase particles with the polymer matrix. The highest amount of electroactive PVDF β- phase was formed in APTES-modified samples while in DDTES samples mainly γ- phase was formed. Dielectric permittivity values and dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES-modified particles led to enhanced breakdown strength of these samples. After the polarization of films, energy harvesting potential was evaluated for all samples. The highest voltage output of ~ 15 V and power ~ 225 μW were obtained for a single APTES-modified harvester [1-2]

Work it Out : Kompakt och komplett träningsutrustning för hemmet

Fysisk aktivering är en minst sagt väsentlig del av livet. Utan den kan allt från depression till en mängd andra typer av sjukdomar som hjärtsjukdomar uppstå (Henriksson, Sundberg, 2015-11-17). Fetma och hjärtsjukdomar avslutar miljontals liv tidigare varje år världen över(Quinn Mattingly, U.Å). Försummelse av träning i olika former är väldigt vanligt och kan till och med hända de mest erfarna idrottare och tränade personer. De senaste två åren har tvingat oss som samhälle att stanna hemma, arbeta hemifrån och till och med träna hemifrån. Det finns fler anledningar till att någon skulle vilja träna hemma i stället för, till exempel, på ett gym. Vare sig det är för bekvämligheten (ingen transport behövs) integriteten (ingen rädsla för att andra människor ska döma dig) eller som vi har sett under åren 2020-2022, att vi måste stanna hemma för att minska risken för spridning av en särskild sjukdom, kan träning hemma vara ett mycket relevant alternativ för att hålla sig i form i dagens samhälle