Magnetoelectric nanocomposites based on electroactive polymers

Tese de doutoramento em Ciências (especialidade de Física)The magnetoelectric (ME) effect is a physical phenomenon with a wide range of device applications such as computer memories, smart sensors, actuators and high frequency microelectronic devices. There are few single-phase ME materials and most of them show weak ME coupling at room temperature. In order overcome this limitation, composite materials with increased ME effect are being developed. Most of the ME investigations have used as piezoelectric matrix ceramic materials, but ceramic composites may become fragile and are limited by deleterious reactions at the interface regions leading to low electrical resistivities and high dielectric losses, making those ceramic composites not attractive for applications. In this way, new multifunctional Poly(vinylidene fluoride) (PVDF) and copolymers based nanocomposites were produced with magnetostrictive NiFe2O4, CoFe2O4 and Ni0.5Zn0.5Fe2O4 nanoparticles. PVDF and copolymers were used due to their flexibility and high piezoelectric coefficient and ferrite nanoparticles due to their good magnetostrictive properties and distinct magnetic response. The piezoelectric, dielectric, ferroelectric, magnetic and ME properties of the resulting nanocomposites were determined and discussed. It was found that the dispersed ferrite nanoparticles strongly enhanced the nucleation of the -phase of the PVDF matrix, essential for the ME response. The origin of such - phase nucleation was attributed to the electrostatic interactions resulting from the presence of negative nanoparticle surfaces that interact with the polymeric CH2 groups that have positive charge density. It was also verified that macroscopic magnetic and dielectric responses of the composites strongly depend on the ferrite nanoparticle content, with both magnetization and dielectric constant increasing for increasing filler content. The -relaxation in the composite samples was similar to the one observed for -PVDF obtained by stretching. A superparamagnetic behaviour was observed for PVDF/NiFe2O4 composites, whereas PVDF/CoFe2O4 samples show a magnetic hysteresis cycle with coercivity of 0.3 T. Ferroelectric and piezoelectric properties were improved when small amount of CoFe2O4 nanoparticles (up to 7% in weight percent (wt.%)) were added to the P(VDFTrFE) matrix. The highest ME response of 41.3 mV/cm.Oe was found in the P(VDFTrFE)/ CoFe2O4 (28/72 wt.%) composite when a HDC=0.25T was transversely applied to the sample surface and a ME voltage coefficient of 5mV/cm.Oe was obtained at a HDC=0.5T for the PVDF/CoFe2O4 (93/7 wt.%) sample. This ME response for the PVDF based composites was possible after stretching of the samples, which also led to the formation of voids. Direct ME effects up to 1.35 mV/cm.Oe were obtained in a HDC =0,5T, for the P(VDFTrFE)/ Ni0.5Zn0.5Fe2O4 (15/85 wt.% ). P(VDF-TrFE)/Ni0.5Zn0.5Fe2O4 nanocomposites show, as compared to P(VDF-TrFE)/CoFe2O4 nanocomposites, linear and nonhysteretic direct magnetoelectric responses up to 0.5 T. It is in this way, novel polymer based ME composites were produced and characterized in such way that it was demonstrated their suitability for sensor applications.O efeito magnetoeléctrico (ME) é um fenómeno físico que tem uma vasta gama de aplicações de que são exemplo as memórias de computador, sensores inteligentes, atuadores e aparelhos microeletrónicos de alta frequência. Existem muito poucos materiais ME de fase única e a maior parte deles exibem um efeito ME muito baixo à temperatura ambiente. Para ultrapassar esta limitação, estão a ser desenvolvidos materiais compósitos com efeito ME melhorado. Contudo, a maior parte das investigações no âmbito dos materiais ME têm usado como matriz piezoelétrica materiais cerâmicos, estes podem-se tornar frágeis e são limitados por reações deletérias nas interfaces levando a resistividades elétricas muito baixas e a elevadas perdas dielétricas, o que faz com que estes compósitos cerâmicos não sejam atrativos do ponto de vista ads aplicações. Desta forma, novos compósitos multifuncionais baseados no Poli(fluoreto de vinilideno) (PVDF) ou nos seus copolímeros foram produzidos através da incorporação de partículas magnetostrictivas de NiFe2O4, CoFe2O4 e Ni0.5Zn0.5Fe2O4. O PVDF e os seus copolímeros foram utilizados devido à sua flexibilidade e alto coeficiente piezoelétrico. Por sua vez, as nanopartículas de ferrites foram usadas devido às suas propriedades magnetostritivas e resposta magnética distinta. As propriedades piezoelétricas, dielétricas, ferroelétricas, magnéticas e ME dos nanocompósitos resultantes foram determinadas e discutidas. Foi descoberto que as nanopartículas de ferrites dispersas no PVDF melhoravam, significativamente a nucleação da fase do polímero, fase essa que é essencial à resposta ME do compósito.A origem desta nucleação foi atribuída às interações eletrostáticas resultantes da presença de nanopartículas com superfícies negativas que interagiam com os grupos CH2 do polímero que possuem densidade de carga negativa. Verificou-se também que a resposta magnética e dielétrica dos compósitos era fortemente dependente da quantidade de ferrites adicionada, com a magnetização e constante dielétrica a aumentarem com o aumento da quantidade de partículas adicionadas. A relaxação nos compósitos foi similar aquela observada no -PVDF obtido através de estiramento.Foi ainda observado um comportamento superparamagético nos compósitos PVDF/NiFe2O4 enquanto que, nas amostras PVDF/CoFe2O4 observou-se um ciclo de histerese magnética com coercividade de 0.3 T. As propriedades piezoelétricas e ferroelétricas também foram melhoradas quando se adicionaram pequenas quantidades de nanopartículas de CoFe2O4 (até 7 % de percentagem em massa (wt.%)) ao P(VDF-TrFE). A maior resposta ME foi verificada na amostra P(VDF-TrFE)/CoFe2O4 (28/72 wt.%) quando um campo magnético HDC=41.3 mV/cm.Oe foi aplicado transversalmente à superfície da amostra, foi também obtido um coeficiente ME de 5mV/cm.Oe na amostra PVDF/CoFe2O4 (93/7 wt.%) quando se aplicou um HDC=0.5T. Esta resposta ME em amostras baseadas em PVDF foi possível graças ao estiramento da amostra, estiramento esse que também deu origem a vazios dentro do compósito. Foram também obtidas respostas ME diretas até 1.35 mV/cm.Oe na amostra P(VDFTrFE)/ Ni0.5Zn0.5Fe2O4 (15/85 wt.% ). Quando sujeitas a HDC até 0.5T estas amostras mostraram um comportamento linear e sem histerese. Desta forma, novos compósitos ME baseados em polímeros foram produzidos e caracterizados de tal forma que foi demonstrada a sua adequação para aplicações na área dos sensores

Magnetic field into multifunctional materials: magnetorheological, magnetostrictive and magnetocaloric

Society is facing serious challenges towards achieving highly efficient utilization of materials and devices. Magnetoactive lightweight materials, such as magnetorheological, magnetostrictive and magnetocaloric materials are attracting increasing interest once they allow a high number of applications such as energy generation, conversion, storage, sensing and actuation, as well as in the biomedical field. In this chapter, the latest research and development in multifunctional lightweight magnetorheological, magnetostrictive and magnetocaloric materials is summarized and discussed in the scope of different application areas. Furthermore, it will be also illustrated the unique functions of inorganic nanomaterials to improve performance of organic materials, as well as combination of the functions of nanomaterials into a device. Final remarks and future perspectives allow to look into a “magnetoactive crystal ball” aiming to foresee what will/should happen in this fascinating research field.The authors thank the FCT- Fundação para a Ciência e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2019 and under project PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. P. Martins thanks FCT for the contract under the Stimulus of Scientific Employment, Individual Support – 2017 Call (CEECIND/03975/2017). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018- 06) programs, respectively. Funding from the European Union’s Horizon 2020 Programme for Research, ICT-02-2018 - Grant agreement no. 824339 – WEARPLEX is also acknowledged

Additive manufacturing of multifunctional materials

In the last decade, there have been significant advances on multifunctional materials development through additive manufacturing techniques, boosted by the Industry 4.0 and the Internet of Things revolution. However, in the particular case of the use of lightweight materials, the performance and multifunctionality is sometimes limited. After a short introduction, this chapter provides a comprehensive assessment of those limitations at the same time as the materials, techniques and challenges on the additive manufacturing of multifunctional materials. In the final paragraphs of this work, the future trends will be presented and discussed.FCT- Fundação para a Ciência e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2020 and under project PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. P. Martins (CEECIND/03975/2017- assistant researcher contract Individual Support – 2017 Call) and V. Correia (DL57/2016 junior researcher contract) thank FCT for the contract under the Stimulus of Scientific Employment. The authors acknowledge funding from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively. Funding from the European Union’s Horizon 2020 Programme for Research, ICT-02-2018 - Grant agreement no. 824339 – WEARPLE

Tailored magnetic and magnetoelectric responses of polymer-based composites

The manipulation of electric ordering with applied magnetic fields has been realized on magnetoelectric (ME) materials, however, their ME switching is often accompanied by significant hysteresis and coercivity that represents, for some applications, a severe weakness. To overcome this obstacle, this work focus on the development of a new type of ME polymer nanocomposites that exhibits tailored ME response at room temperature. The multiferroic nanocomposites are based on three different ferrite nanoparticles, Zn0.2Mn0.8Fe2O4 (ZMFO), CoFe2O4 (CFO) and Fe3O4 (FO), dispersed in a piezoelectric co-polymer poly(vinylindene fluoride-trifluoroethylene), P(VDF-TrFE), matrix. No substantial differences were detected on the time-stable piezoelectric response of the composites (≈ -28 pC.N−1) with distinct ferrite fillers and for the same ferrite content of 10wt.%. Magnetic hysteresis loops from pure ferrite nanopowders showed different magnetic responses. ME results of the nanocomposite films with 10wt.% ferrite content revealed that the ME induced voltage increases with increasing DC magnetic field until a maximum of 6.5 mV∙cm−1∙Oe−1, at an optimum magnetic field of 0.26 T, and 0.8 mV∙cm−1∙Oe−1, at an optimum magnetic field of 0.15T, for the CFO/P(VDF-TrFE) and FO/P(VDF-TrFE) composites, respectively. On the contrary, the ME response of the ZMFO/P(VDF-TrFE) exposed no hysteresis and high dependence on the ZMFO filler content. Possible innovative applications such as memories and information storage, signal processing, ME sensors and oscillators have been addressed for such ferrite/PVDF nanocomposites.We thank Dr. E. Carbó-Argibay for his assistance with TEM analysis. This work is funded by FEDER funds through the “Programa Operacional Factores de Competitividade – COMPETE” and by national funds from FCT – Portuguese Foundation for Science and Technology in the framework of the strategic project Strategic Project PEST-C/FIS/UI607/2014. The authors also thank funding from Matepro –Optimizing Materials and Processes”, ref. NORTE-07-0124 FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). P. Martins acknowledges also support from FCT GRANT SFRH/BPD/96227/201

Magnetic materials for magnetoelectric coupling: An unexpected journey

Magnetic materials for magnetoelectric coupling are reported. After an introduction of magnetoelectric effect and materials, an historical on the main developments in this field are presented. Then, the main concepts related to multiferroic and magnetoelectric materials are introduced, together with the description of the main types of magnetoelectric materials and structures. Finally, the magnetic materials used the development of magnetoelectric composites are presented and discussed, highlighting their main physico-chemical characteristics and processing methods. In this way, a complete account on concepts, materials and methods is presented in this strongly evolving research field, with strong application potential in the areas of sensors and actuators, among others.FCT- Fundação para a Ciência e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2020 and under projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. P.M., A.C.L. and N.P. also support from FCT (for the contract under the Stimulus of Scientific Employment, Individual Support – 2017 Call (CEECIND/03975/2017, for the SFRH/BD/132624/2017 and for the SFRH/BD/131729/2017 grant, respectively). Finally, the authors acknowledge funding by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033 and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) program

Magnetoelectrics: Three centuries of research heading towards the 4.0 industrial revolution

Magnetoelectric (ME) materials composed of magnetostrictive and piezoelectric phases have been the subject of decades of research due to their versatility and unique capability to couple the magnetic and electric properties of the matter. While these materials are often studied from a fundamental point of view, the 4.0 revolution (automation of traditional manufacturing and industrial practices, using modern smart technology) and the Internet of Things (IoT) context allows the perfect conditions for this type of materials being effectively/finally implemented in a variety of advanced applications. This review starts in the era of Rontgen and Curie and ends up in the present day, highlighting challenges/directions for the time to come. The main materials, configurations, ME coefficients, and processing techniques are reported.This research was funded by FCT—Fundação para a Ciência e Tecnologia: projects UID/FIS/04650/2019, PTDC/EEI-SII/5582/2014, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017 and grants CEECIND/03975/2017, SFRH/BD/132624/2017 and SFRH/BD/131729/2017; the SpanishState Research Agency (AEI) and the European Regional Development Fund (ERFD): project PID2019-106099RB-C43/AEI/10.13039/501100011033; Basque Government Industry and Education Departments:ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs.The authors thank the FCT—Fundação para a Ciência e Tecnologia- for financial supportin the framework of the Strategic Funding UID/FIS/04650/2019 and under projects PTDC/EEI-SII/5582/2014, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. P.M., A.C.L. and N.P. also support from FCT (forthe contract under the Stimulus of Scientific Employment, Individual Support—2017 Call (CEECIND/03975/2017, forthe SFRH/BD/132624/2017 and for the SFRH/BD/131729/2017 grant, respectively). Finally, the authors acknowledgefunding by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD)through the project PID2019-106099RB-C43/AEI/10.13039/501100011033.and from the Basque Government Industryand Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively

Environmentally friendlier wireless energy power systems: the coil on a paper approach

Paper is ubiquitous in everyday life and a low-cost environmentally friendly material. Thus, the printing of advanced conductive/magnetic nanomaterials on paper will allow the scalable production of flexible smart electronics, including energy-storage devices, sensors, inductors or antennas, among others, contributing towards more sustainable electronics. Particularly, wireless charging technologies are becoming essential for internet-of-things (IoT)-related electronic devices due to the ever-decreasing dimensions of portable/mobile devices that limits the quantity of energy that can be stored. Here, screen-printed paper-based coils and inductors operating on the 1MHz - 20MHz range are presented based on Poly(vynil alcohol)/Fe3O4 and Ag inks. The ability of the printed cores and inductors to be incorporated on flexible wireless power transfer modules (WPTM) is technologically demonstrated by wireless powering light-emitting diodes (LEDs). The achieved induction efficiency of 94% is the highest reported on printed WPTM. The printed coils are also characterized by mechanical, hydrophobic and electrical properties that are suitable for IoT and industry 4.0 applications.All authors thank the FCT- Fundação para a Ciência e Tecnologia the financial support in the context of the Strategic Funding UID/FIS/04650/2019 and under projects PTDC/EEI-SII/5582/2014, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. Pedro Martins and Clarisse Ribeiro thank the FCT for the contracts under the Stimulus of Scientific Employment, Individual Support: CEECIND/03975/2017, and 2020.04163.CEECIND, respectively. Ricardo Brito-Pereira also acknowledges the FCT for the SFRH/BD/140698/2018 grant. Finally, the authors acknowledge funding by the Basque Government Industry and Education Department under the ELKARTEK, and PIBA (PIBA 2018-06) programs, respectively. Finally, funding from European Union’s Horizon 2020 Program for Research, ICT-02-2018 - Flexible and Wearable Electronics, Grant agreement no. 824339 – WEARPLEX is also acknowledgedinfo:eu-repo/semantics/publishedVersio

Magnetic proximity sensor based on magnetoelectric composites and printed coils

Magnetic sensors are mandatory in a broad range of applications nowadays, being the increasing interest on such sensors mainly driven by the growing demand of materials required by Industry 4.0 and the Internet of Things concept. Optimized power consumption, reliability, flexibility, versatility, lightweight and low-temperature fabrication are some of the technological requirements in which the scientific community is focusing efforts. Aiming to positively respond to those challenges, this work reports magnetic proximity sensors based on magnetoelectric (ME) polyvinylidene fluoride (PVDF)/Metglas composites and an excitation-printed coil. The proposed magnetic proximity sensor shows a maximum resonant ME coefficient (α) of 50.2 Vcm−1 Oe−1, an AC linear response (R2 = 0.997) and a maximum voltage output of 362 mV, which suggests suitability for proximity-sensing applications in the areas of aerospace, automotive, positioning, machine safety, recreation and advertising panels, among others.This research was funded by CT- Fundação para a Ciência e Tecnologia in the framework of the Strategic Funding UID/FIS/04650/2019 and under projects PTDC/EEI-SII/5582/2014, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. A.C.L. and N.P. acknowledge also support from FCT (SFRH/BD/132624/2017 and SFRH/BD/131729/2017 grants respectively). P. Martins also thanks FCT for the contract under the Stimulus of Scientific Employment, Individual Support—2017 Call (CEECIND/03975/2017). Finally, the authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectivel

Wide-range magnetoelectric response on hybrid polymer composites based on filler type and content

Abstract: In order to obtain a wide-range magnetoelectric (ME) response on a ME nanocomposite that matches industry requirements, Tb0.3Dy0.7Fe1.92 (Terfenol-D)/CoFe2O4/P(VDF-TrFE) flexible films were produced by solvent casting technique and their morphologic, piezoelectric, magnetic and magnetoelectric properties investigated. The obtained composites revealed a high piezoelectric response (≈-18 pC.N-1) that is independent of the weight ratio between the fillers. In turn, the magnetic properties of the composites were influenced by the composite composition. It was found that the magnetization saturation values decreased with increasing CoFe2O4 content (from 18.5 to 13.3 emu.g-1) while the magnetization and coercive field values increased (from 3.7 to 5.5 emu.g-1 and from 355.7 to 1225.2 Oe, respectively) with increasing CoFe2O4 content. Additionally, those films showed a wide-range dual-peak ME response at room temperature with the ME coefficient increasing with weight content of Terfenol-D, from 18.6 mV.cm-1.Oe-1 to 42.3 mV.cm-1.Oe-1.FCT-Fundação para a Ciência e Tecnologia—for financial support in the framework of the Strategic Funding UID/FIS/04650/2013 and under project PTDC/EEI-SII/5582/2014. Pedro Martins, Silvia Reis and Marco Silva also acknowledge support from FCT (SFRH/BPD/96227/2013, SFRH/BDE/406 and SFRH/BD/70303/2010 grants, respectively). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support). Financial support from the Basque Government Industry Department under the ELKARTEK program is also acknowledged. The authors thank INL, International Iberian Nanotechnology Laboratory, Braga, Portugal, for offering access to their instruments and expertiseinfo:eu-repo/semantics/publishedVersio

Multifunctional magnetoelectric sensing and bending actuator response of polymer-based hybrid materials with magnetic ionic liquids

With the evolution of the digital society, the demand for miniaturized multifunctional devices has been increasing, particularly for sensors and actuators. These technological translators allow successful interaction between the physical and digital worlds. In particular, the development of smart materials with magnetoelectric (ME) properties, capable of wirelessly generating electrical signals in response to external magnetic fields, represents a suitable approach for the development of magnetic field sensors and actuators due to their ME coupling, flexibility, robustness and easy fabrication, compatible with additive manufacturing technologies. This work demonstrates the suitability of magnetoelectric (ME) responsive materials based on the magnetic ionic liquid (MIL) 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim][FeCl4]) and the polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE) for magnetic sensing and actuation device development. The developed sensor works in the AC magnetic field and has frequency-dependent sensitivity. The materials show voltage responses in the mV range, suitable for the development of magnetic field sensors with a highest sensitivity (s) of 76 mV·Oe−1. The high ME response (maximum ME voltage coefficient of 15 V·cm−1·Oe−1) and magnetic bending actuation (2.1 mm) capability are explained by the magnetoionic (MI) interaction and the morphology of the composites.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2020, UID/QUI/00686/2020, LA/P/0008/2020, UIDB/50006/2020 and UIDP/50006/2020. The authors are grateful for funds through FCT under the projects 2022.05932.PTDC, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017 and grant SFRH/BD/145345/2019 (L.C.F). D.M.C. and P.M. thank FCT—Fundação para a Ciência e Tecnologia for the contract under the Stimulus of Scientific Employment, Individual Support 2020.02915.CEECIND and CEECIND/03975/2017, respectively. This study forms part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by the Basque Government under the IKUR program. Funding from the Basque Government Industry Departments under the ELKARTEK program is also acknowledged. Technical and human support provided by IZO-SGI, SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully acknowledged