O principal objetivo da presente dissertação foi o estudo e calibração de sensores baseados em PVDF (Fluoreto de polivinilideno) para a medição de pressão dinâmica e de ondas de choque.Este sensor é uma solução promissora e fácil de usar que possui uma grande banda de medição e que pode ser fixado ou colado à maioria das superfícies, eliminando a necessidade de furagem das superfícies ao contrário dos sensores piezoelétricos comuns (normalmente usados na medição de pressão dinâmica e de ondas de choque) disponíveis no mercado.No entanto, os sensores PVDF tem algumas limitações e requerem alguma habilidade para que sejam propriamente integrados numa cadeia de aquisição. Além disso, as medições deste sensor ainda são bastante dependentes da experiência (Arrigoni et al. 2018).Várias experiências foram realizadas de modo a estudar os efeitos do invólucro do sensor no sinal obtido. Parte das experiências focou se no tipo de adesivo utilizado para a fixação do sensor na instalação, enquanto a outra parte focou se na proteção e apoio do sensor. Dois diferentes modos de aquisição de sinal foram considerados: medição em modo de voltagem e medição em modo de carga. Um segundo conjunto de experiências foi realizado para estudar a capacidade de medição de pressão dos sensores PVDF quando submersos. A criação de um setup experimental permitiu a geração de cavitação induzida por choque através do disparo de um pulso laser para um alvo submerso. Resultados interessantes foram obtidos ao utilizar sensores PVDF para a medição da pressão dinâmica e ondas de choque geradas por bolhas de cavitação. Um invólucro para o sensor PVDF que permite a obtenção de resultados com maior precisão e reprodutibilidade foi descoberto.

LiMn2O4 and LiMn1.5M0.5O4 (M: Ni, Cu, Co) doped particles have been synthetized by sol-gel. Particles between 50 and 200 nm were obtained with the cubic spinel structure of the LiMn2O4. Ni doping shows a more efficient substitution in the octahedral 16d site, replacing the Mn3+ thorn ion, improving the important drawback of poor cycling behavior of LiMn2O4. The average pore size decrease with the addition of the doped elements in the LiMn2O4 structure from 2.9 to 2.6 nm. Thermal analysis shows that the doped particles present higher thermal stability that the undoped ones. Electrochemical behavior of the cathodes prepared with each of the active materials show that the doping influenced the electrochemical performance of the active material. Thus, a specific capacity of 33, 74, 44 and 53 mAh g(-1) (at C) and 74, 89, 59 and 69 mAh g(-1) (at C/10) were obtained for LiMn2O4, LiMn1.5Ni0.5O4, LiMn1.5Cu0.5O4 and LiMn1.5Co0.5O4 cathodes, respectively. All cathodes present good electrochemical stability with low capacity fade of 0.5 and 3.1% for LiMn1.5Ni0.5O4 and LiMn1.5Cu0.5O4, respectively, after 50 cycles. These results show an improvement of electrochemical performance for LiMn2O4 doped with Ni, Cu and Co, demonstrating their suitability for lithium-ion battery systems.

Rapid technological developments in biomedicine, sensors, actuators and energy areas are taken place in the context of the global digital transformation, supported by the “Industry 4.0″ and “Internet of Things” (IoT) concepts. Those developments must include circular economy considerations in the scope of the 2030 sustainable developments goals to ensure easy access to affordable, sustainable, reliable, and modern services for all. To fulfil these advances, materials with high-performance based on biopolymers with tailored dielectric, magnetic and conducting properties are needed for improving devices performance while reducing environmental impact. Within this scope, bio-based resources are considered as next-generation materials for a broader range of applications. In this context, we present on the molecular structure, organization, main physical-chemical and functional properties of the most promising biopolymers. Further, the various possible modifications and processing methods are discussed to reach specific morphological, structural and/or functional characteristics. Finally, bio polymers-based blends and composites are discussed, alongside with their main application areas, opportunities, and challenges.

A circular economy world action plan has been assumed to support sustainability and circular product design in the most intensive sectors such as construction, textiles, plastics, and electronics. A transition to a more circular economy is essential to improve the future quality of life. This chapter discusses how the circular economy offers an excellent opportunity to reinvent the economical paradigms, making them more sustainable and competitive. In this scope, energy companies must systematically pursue their transition to affordable, reliable, and more sustainable energy and set ambitious targets in terms of reducing CO 2 emissions. In the following, different energy generation and storage systems are presented and their perspectives and contributions to a sustainable future are discussed. The increasing use of renewable energy generation and energy storage systems brings new perspectives and represents an essential contribution to a sustainable approach. Further, new affordable recycling technologies for raw materials recovery, new ecodesigns, and reutilization by second use are some of the necessary procedures to be considered for an environmentally friendlier and sustainable future.

In order to improve battery performance by tuning battery separator membranes, this work reports on porous poly(vinylidene fluoride-co-trifluoroethylene) - P(VDF-TrFE)- membranes with surface pillar microstructures. Separators with tailored pillar diameter, height and bulk thickness were fabricated by template patterning and computer simulations, allowing to evaluate the effect of the pillar microstructure characteristics on battery performance. It is shown that the different pillar microstructures of the separators affect the uptake value (150–325%), ionic conductivity value (0.8–1.6 mS·cm−1) and discharge capacity of the lithium ion batteries (LIB) when compared with the separator without pillars. The experimental charge-discharge behavior demonstrates that the pillar parameters affect battery performance and the best microstructure leading to 80 mAh·g−1 at 2C. Battery performance can be thus optimized by adjusting pillar diameter, height and bulk thickness of the separators keeping its volume constant, as demonstrated also by the simulation results. The parameter with most influence in battery performance is the bulk thickness of the separator, allowing to obtain a maximum discharge capacity value of 117.8 mAh·g−1 at 90C for a thickness of 0.01 mm. Thus, this work shows that the optimization of the pillar microstructure of the separator membranes allows increasing the capacity towards a new generation of high-performance LIBs.

Increasing mobility, sensing, and interconnection needs is driving the need for low cost and environmental friendly energy storage systems, and therefore, printed batteries represent one of the most appealing solutions. To identify materials‐processing conditions–performance relationships to design improved screen‐printed batteries, the effects of the ink preparation method and the chemical structure of the polymer binder on batteries performance are studied. Screen‐printed cathodes with “green” solvent cyclopentyl methyl ether (CPME) are produced using different styrene‐block‐copolymers (SBC) with different ethylene/butylene ratios and using three dispersion methods of the cathode components. It is shown that a limited amount of ethylene in the copolymer binder enhances the discharge capacity for 5C and C/5 rates (105 and 142 mAh g−1, respectively). The ink preparation methods affect cathode performance in a larger extent than the chemical structure of the binder. The sequential addition of active and conductive materials to the styrene–ethylene/butylene–styrene solution results in a higher cathode charge/discharge capacity compared with the other explored dispersion methods (150/147 mAh g−1 for charge/discharge capacity). The optimized cathode performance is related with the improved degree of dispersion of the cathode components, as assessed by rheological properties of inks and by the morphological characterization of the printed cathodes

The low dimensionality open a new roads of opportunities and challenges. At the nanoscale some materials present new interesting effects that should be studied and understood. The nanostructured materials present a great potential functionalities due the large surface to volume ratio when compared with the bulk. With the miniaturization of the ME materials size, applications on medical and biomedical engineering could be then explored. Different morphologies with different connectivities between the magnetostrictive and piezoelectric materials have been produced allowing the obtainment of innovative structures. In this chapter the low dimensionality of polymer based ME composites will be presented, challenges that need to be addressed in pursuing practical applications of ME devices will be discussed and promising future for research and technology in this field evaluated.

The synthetic analogue of the mineral giniite is a promising material for capture of phosphopeptides from complex tryptic digests, photocatalysis and cathode for lithium battery applications. In all these applications, the crystal morphology of giniite shows to be extremely important, however, the reported synthesis and crystal morphologies are scattered among a variety of approaches. Here we report a hydrothermal synthesis that allows achieving five different morphologies of giniite only by changing the pH by addition of three different alkaline cations (Na+, Li+ and K+) in form of hydroxides. At pH 2, micrometric sphere-like assemblies of nanoparticles were obtained. At pH 4, fractal dendritic crystals as well as intergrown flower-like and asterisk-like crystals were synthesized. At pH 6, the synthesis resulted in dagger-like crystals of dissolved dendritic structures.

The rapid technological evolution and population growth require more sustainable materials that are compatible with the circular economy paradigm. Sustainable energy storage can be applied to a number of areas that differ in power and energy requirements and also suitable for political organizations and NGOs focusing on this subject and/or organizing related funding schemes. In this chapter, the summary and outlook on diverse sustainable materials for energy storage devices are summarized.

The magnetoelectric (ME) effect is characterized by the variation of the electrical polarization of a material with an applied magnetic field and the variation of the magnetization of a material with an applied electric field. Single-phase materials with intrinsic ME effect are not generally used for practical applications since they typically show weak ME coupling at room temperatures. Such problem has been overcome by the development of ME composites. Strong ME effect at room temperature has been obtained, particularly in those composed by a piezoelectric and a magnetostrictive phase. In such materials, a strain is induced on the magnetostrictive phase once a magnetic field is applied to the composite. This strain is transmitted to the piezoelectric constituent, which undergoes a change in the electrical polarization. In an analogous way, the reverse effect can occur. The main objective of the thesis was the development of high performance polymer-based ME materials, that were characterized, optimized and their potential applications evaluated. Particulate ME composites were produced from materials with strong piezoelectric - poly(vinylidene fluoride) (P(VDF)) - and magnetostrictive - Cobalt iron oxide (CoFe2O4 - CFO) - responses in the form of film, membrane, fibers, and spheres. Related piezoelectric materials, such as the copolymer of P(VDF), poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), and magnetic nanoparticles, such as magnetite (Fe3O4), goethite (δ-FeO(OH)) and CoFeO(OH), were also used. All developed morphologies show the presence of the ME effect. The studies on film morphology addressed the relevance of the magnetostrictive filler dispersion on ME composite response, suggesting that the use of surfactants or ultrasounds to improve the dispersion leads to the same ME response. The filler size and shape shows an important role on the ME measurements. Studies with Fe3O4 nanoparticle with sizes of 9, 30 and 50 nm within a P(VDF-TrFE) matrix show that the largest α31 = 0.97 mV.cm-1Oe-1 is obtained for the lowest nanoparticle size. The shape of the same filler was studied and the results shows that a rod shape, comparing with a spherical, nucleate the β-phase of P(VDF), due to the high interface interaction between the polymer and the filler. Anisotropic nanosheet fillers of δ-FeO(OH) and CoFeO(OH) were synthetized and evaluated for the preparation of ME composites. Thus, δ-FeO(OH) /P(VDF-TrFE) composites lead to a maximum ME response of 0.4 mV.cm-1.Oe-1, which depends on filler content, alignment state as well as on both incident magnetic field direction and magnitude. A new ME effect is proposed based on the magnetic rotation of the nanosheets inside the piezoelectric polymer matrix. New CoFeO(OH) highly magnetostrictive (λ = 507 ppm) and anisotropic nanostructures were synthesized by a coprecipitation method using a modified gas-slugs microfluidic system. CoFeO(OH) /P(VDF-TrFE) composites reveal an interfacial ME coupling strongly dependent on the angle between HDC and filler length direction, with a maximum α31 = 5.10 mV.cm-1.Oe-1. ME membranes were also produced in CFO/P(VDF-TrFE) composites. The porous morphology and ME response were evaluated. The porous composite shows piezoelectricity with an effective piezoelectric coefficient (d33) of -22 pC.N-1, a maximum magnetization of 12 emu.g-1 and a maximum ME coefficient of 9 mV.cm-1.Oe-1. ME nanofibers and microspheres of CFO/P(VDF) produced by electrospinning and electrospray technique, respectively, were studied and evaluated. The average diameter of the nanofibers is ≈325 nm, independently of filler content, and the amount of crystalline polar β-phase was strongly enhanced when compared to pure P(VDF) polymer fibers, due to the introduction of the magnetostrictive fillers. The piezoelectric response of these electroactive nanofibers was modified by an applied magnetic field, thus evidencing the ME character of the CFO/P(VDF) composites. The CFO nanoparticles content in the ME microspheres (3-7 µm diameter) reached values up to 27 wt.%, despite their concentration in the starting solution reaching values up to 70 wt.%. No relevant effect on β-phase content (≈60 %), crystallinity (40 %) and onset degradation temperature (460-465 °C) of the polymer matrix was observed. The ME microspheres show a maximum|d33|≈30 pC.N-1, leading to a ME response of ∆|d33|≈5 pC.N-1 obtained when a 220 mT DC magnetic field was applied. Its also shown that the interface between CFO and P(VDF) (0-55 %) has a strong influence on the ME response of the microspheres. The simplicity and the scalability of the processing methods used in the present work as well as the excellent ME response in a large variety of composite morphologies suggest a large application potential of the developed polymer-based ME composites in areas such as sensors and actuators and tissue engineering, among others.