Matching the Directions of Electric Fields from Triboelectric and Ferroelectric Charges in Nanogenerator Devices for Boosted Performance

This research was supported by Riga Technical University's Doctoral Grant program. This research was also supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.Embedding additional ferroelectric dipoles in contacting polymer layers is known to enhance the performance of triboelectricnanogenerator (TENG) devices. However, the influence of dipoles formed between the triboelectric surface charges on two contacting ferroelectric films has been ignored in all relevant studies. We demonstrate that proper attention to the alignment of the distinct dipoles present between two contacting surfaces and in composite polymer/BaTiO3 ferroelectric films can lead to up to four times higher energy and power density output compared with cases when dipole arrangement is mismatched. For example, TENG device based on PVAc/BaTiO3 shows energy density increase from 32.4 μJ m−2 to 132.9 μJ m−2 when comparing devices with matched and mismatched dipoles. The presented strategy and understanding of resulting stronger electrostatic induction in the contacting layers enable the development of TENG devices with greatly enhanced properties.Riga Technical University's Doctoral Grant program; European Regional Development Fund 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Hybrid Tribo-Piezo-Electric Nanogenerator with Unprecedented Performance Based on Ferroelectric Composite Contacting Layers

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.It was recently reported that more efficient triboelectric nanogenerator (TENG)-like devices can be prepared using inversely polarized ferroelectric films made of same material as the contacting layers. In the present work, a clear correlation between the piezoelectric response of inversely polarized ferroelectric PVDF/BaTiO3 nanocomposite films and the performance of the TENG-like device based on these films is demonstrated. This observation is explained by magnified electrostatic induction that is driven by piezoelectric charges and ferroelectric properties of these films. A double capacitor model is proposed that effectively portrays the interactions between ferroelectric layers during contact-separation and subsequent charge redistributions in the external circuit. The new understanding has allowed the result of 3-fold higher open circuit voltages (2.7 kV from 5 cm2) as compared to that of a state of the art TENG. Furthermore, findings uncover the potential for vast improvement in the field of nanogenerators for mechanical energy harvesting as a significantly better piezoelectric performance of flexible nanogenerators has been reported elsewhere.ERDF 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

The role of intermolecular forces in contact electrification on polymer surfaces and triboelectric nanogenerators

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.The contact electrification of polymer interfaces provides an energy harvesting function to triboelectric (nano)generators (TEG). The electron transfer between contacted-separated surfaces has been considered as the main electrification mechanism for polymers in TEG. The electron transfer mechanism widely proposed in literature requires a contact between chemically different polymer materials, as well as subsequent increase of the specific contact area, which is commonly accomplished via nanostructuring. Herein, we showed that contact electrification could be controlled by intramolecular forces in the polymer bulk and adhesive forces at the contact interface, and the chemical contact between different polymers was not needed for contact electrification. The results also confirm the breaking of the covalent bond as a mechanism of the contact electrification of polymer insulators.ERDF 1.1.1.1./16/A/013; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Emaljas seguma nepārtrauktības nodrošināšana, pielietojot sol-gēla pārklājumus

Sola-gēla pārklājumi ir ļoti perspektīvi un plaši pielietojami dažādās nozarēs. Eksperimentos izmantotā borsilikātu emalja ar augstu SiO2 saturu tika uzklāta uz elektrotehniskā tērauda (DI143) vienā slānī, kā arī dažādas sola-gēla sistēmas, sākot ar vienu komponentu TiO2 un SiO2, kā arī divkomponentu TiO2-SiO2 sistēmām

Sola-gēla pārklājumi emaljas virsmas porainības samazināšanai

Viena no potenciālajām sola-gēla pārklājumu izmantošanas jomām ir augstas jaudas Saules enerģijas izmantošanas (kolektori) iekārtas. Šādi pārklājumi būtu jāuzklāj emaljētām tērauda caurulēm, nodrošinot saules gaismas augstu absorbcijas koeficientu un zemu atstarošanas koeficientu, vienlaicīgi jāsamazina emaljai raksturīgā virsmas porainība Darbā tika izmantotas dažādas sola-gēla sistēmas sākot ar vienkāršākajām, vienkomponentu TiO2 un SiO2 sistēmām, kā arī divkomponentu un trīskomoponentu TiO2 - SiO2, TiO2 - SiO2 - ZrO2 sistēmas. Sola-gēla pārklājumus ieguva ar iemērkšanas-izvilkšanas paņēmienu. Iegūtie materiāli pētīti ar skenējošo elektronu, atomu spēka un optisko mikroskopiju, rentgenfāžu analīzi, emaljas-sola-gēla pārklājumu porainība tika noteikta ar poroskopu

Antireflective and Photocatalytic Sol-Gel Coating on Enamel

Sol-gel coatings are widely used for a variety of technological and commercial applications as wear, corrosion , and high-temperature-resistant coatings or with special functions for use in electronics, microelectronics, optics and chemistry . One of the potential areas is production of high capacity devices of solar energy (collectors) and a view to attain self-cleaning surfaces for mirrors, light (thermal energy) reflection and permeability regulating coatings for absorptive elements of solar energy – enameled steel tubes

Enamel as High Temperature Solar Light Receiver

Porcelain enamel coatings for steel possess chemical and mechanical stability in various environments including acid, alkaline, high-temperature and harsh working conditions, and so are widely used for a variety of consumer applications and for the protection of steel in many industrial chemical applications [1-2]. One of their potential uses is production of high-temperature spectral selective material for concentrated solar-power receivers [3]. Concentrated solar power systems use solar absorbers to convert sunlight to thermal electric power. Solar-power applications require spectrally selective coatings that exhibit high solar absorptance, low thermal emittance [4], and excellent stability at elevated temperatures in ambient

Optical, photocatalytical and structural properties of TiO2 – SiO2 sol-gel coatings on high content SiO2 enamel surface

TiO2 – SiO2 films deposited on enamel surface were investigated for self - cleaning applications. The TiO2 – SiO2 optical films prepared from a sol–gel precursor were deposited on enamel surface using dip - coating techniques. Films were calcined different time from one hour till ten hours to investigate effect of calcination on self-cleaning and structural properties. Effects of film crystal structure, microstructure, photocatalytic activity and optical properties of the films were investigated using XRD, AFM and spectrophotometer and contact angle measurement. The TiO2 – SiO2 dip - coating optical films calcined 1 h resulted in high structured surfaces, which found to increase the photocatalytic activity.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5188</p

Optical, Photocatalytical and Structural Properties of TiO2-SiO2 Sol-Gel Coatings on High Content SiO2 Enamel Surface

The TiO2-SiO2 optical films prepared from a sol-gel precursor were deposited on enamel surface using dip-coating techniques. The films were calcined different time from one hour till ten hours to investigate effect of calcination on self-cleaning and structural properties. Effects of film crystal structure, microstructure, photocatalytic activity and optical properties of the films were investigated using XRD, AFM and spectrophotometer and contact angle measurement. The TiO2-SiO2 dip-coating optical films calcined 1 h resulted in high structured surfaces, which were found to increase the photocatalytic activity

Photocatalytic Activity of ZnFe2O4 Nanoparticle Clusters under Visible Light Irradiation

Porous zinc ferrite (ZnFe2O4) nanoparticle clusters have been synthesized by the sol-gel auto-combustion method and the effect of excess iron on structural and visible light photocatalytic activity have been studied. X-ray diffraction (XRD), BET, scanning electron microscopy (SEM) and diffuse reflectance spectroscopy are used to investigate characteristics of synthesized ZnFe2O4 nanomaterials. The XRD patterns show that samples consist of single phase spinel structure with crystallite sizes below 50 nm. SEM analysis indicate that nanosized particles are grown together in clusters with size of several microns. The photocatalytic activity of synthesized ferrite nanomaterials to methylene blue (MB) under visible light irradiation is investigated. Results show that stoichiometric zinc ferrite exhibited higher photocatalytic activity (40%) than excess-iron sample (6%) under visible light irradiation by 3 hours. Lower photocatalytic activity of iron excess samples could be related to oxygen vacancies, which are created by restoring overall charge balance in the material and can behave as recombination centres