Aikaterini Sanida

Structured electrolytes based on deep eutectic solvents (DESs) face electrochemical limitations of vehicular diffusion due to high viscosities often leading to low conductivities. Here, we demonstrate that the inverse relationship between viscosity and conductivity in DESs can be circumvented by leveraging their hydrogen bonding networks for Grotthuss proton transport. Using DESs comprising imidazole and levulinic acid, we show that the existence of extended hydrogen‐bonded chains coupled with rapid reorientation of protonated imidazoles result in enhanced Grotthuss proton diffusion in these concentrated hydrogen‐bonded electrolyte systems. Key machine‐learning driven simulations – crucially incorporating nuclear quantum effects (NQEs) – validate our experimental findings, which classical simulations fail to capture. This study demonstrates that NQEs promote imidazole protonation, catalyze the hydrogen‐bonded chain formation, and influence chain reorientation, resulting in enhanced dynamics surpassing classical predictions in structured electrolytes. While the conclusions are drawn here for a particular imidazole/acid system, they are expected to apply broadly to protic DESs that support chain‐like structures and exploit Grotthuss diffusion as the primary charge‐transport mechanism.

In this work magnetic nanoparticles (Fe₃O₄, or ZnFe₂O₄, or SrFe₁₂O₁₉) and BaTiO₃ microparticles were embedded in an epoxy resin for the synthesis of three series of hybrid magnetic polymer nanocomposites. Barium titanate content was kept constant, while magnetic phase content was varied. Fabricated specimens were structurally and morphologically characterized by employing scanning electron microscopy images and X-ray diffraction patterns. Results implied successful synthesis of the hybrid nanocomposites. The magnetic behavior of the pure magnetic nanoparticles and the fabricated nanocomposites was investigated via a Vibrating Sample Magnetometer. The magnetic performance of each type of magnetic phase (i.e., soft and hard) was induced in the nanocomposites, and magnetic performance is strengthened with the increase in magnetic phase content. Initial magnetization curves were used for the determination of mass magnetic susceptibility of all nanocomposites. Magnetic saturation and magnetic remanence have been found to follow a linear relationship with magnetic phase content, giving the opportunity to predict the system’s response in advance.

The present study explores the energy storage and harvesting properties of nanocomposite systems reinforced with carbon black and magnetite nanoparticles (Fe₃O₄). The systems’ energy storage performance was evaluated under both AC and DC conditions to analyze the impact of temperature, DC charging voltage levels, and varying filler contents on the stored and recovered energy. The experimental findings demonstrated that these systems are capable of efficiently storing and releasing energy on demand via a rapid charge–discharge mechanism. Dynamic mechanical and dielectric analyses revealed significant enhancements in the storage modulus and the energy efficiency of these materials due to the synergistic effects of the nanoparticles and the interactions between them and the polymer matrix. The incorporation of the carbon black and magnetite nanoparticles improves the energy-storage capabilities, supported by augmented interfacial polarization phenomena, which facilitate charge migration and accumulation. These systems exhibit rapid charge and discharge behavior, making them suitable for applications requiring high power density and fast energy storage and recovery cycling. These findings underscore the aptitude of these nanocomposites for high-performance energy-storage solutions, emphasizing their adaptability to applications requiring both high energy density and efficient recovery in tandem with adequate thermomechanical performance.

Polymer matrix nanocomposites are widely studied because of the versatility of their physical and mechanical properties. When these properties are present simultaneously, responding at relative stimuli, multifunctional performance is achieved. In this study, hybrid nanocomposites of SrFe₁₂O₁₉ and BaTiO₃ ceramic particles dispersed in an epoxy resin matrix were fabricated and characterized. The content of SrFe₁₂O₁₉ was varying, while the amount of BaTiO₃ was kept constant. The successful fabrication of the nanocomposites and the fine dispersion of the ceramic particles was verified via the morphological and structural characterization carried out with X-ray Diffraction patterns and Scanning Electron Microscopy images. Dielectric response and related relaxation phenomena were studied by means of Broadband Dielectric Spectroscopy. Dielectric permittivity augments with filler content, while the recorded relaxations, with descending relaxation time, are: (i) interfacial polarization, (ii) glass-to-rubber transition, (iii) intermediate dipolar effect, and (iv) re-orientation of polar-side groups of the main polymer chain. SrFe₁₂O₁₉ nanoparticles induce magnetic properties to the nanocomposites, which alter with the magnetic filler content. Static and dynamic mechanical response improves with filler content. Thermogravimetric analysis shown that ceramic particles are beneficial to the nanocomposites’ thermal stability. Glass transition temperature, determined via Differential Scanning Calorimetry, was found to slightly vary with filler content, in accordance with the results from dynamic mechanical and dielectric analysis, indicating the effect of interactions occurring between the constituents. Examined systems are suitable for energy storing/retrieving.

The incorporation of ceramic nanoinclusions in carbon nanocomposites can induce additional functionality in the field of magnetic properties, piezoelectricity, etc. In this study, series of nanocomposites, consisting of different carbon nanoinclusions (carbon black, MWCNTs, graphene nanoplatelets, nanodiamonds) and magnetite nanoparticles incorporated into a commercially available epoxy resin were developed varying the filler type and concentration. Experimental data from the static tensile tests and dynamic mechanical analysis (DMA) demonstrated that the elastic tensile modulus and storage modulus of hybrid nanocomposites increase with an increase in filler content up to almost 100% due to the inherent filler properties and the strong interactions at the interface between the epoxy matrix and the nanoinclusions. Strong interactions are implied by the increasing values of the glass transition temperature recorded by differential scanning calorimetry (DSC). On the contrary, tensile strength and fracture strain of the nanocomposites were found to decrease with filler content. The results highlight the potentials and capabilities of developing hybrid multifunctional nanocomposites with enriched properties while holding their structural integrity.

In this study, hybrid nanocomposites consisting of Fe₃O₄/BaTiO₃/epoxy resin were prepared with varying amounts of filer content. Structural and morphological characterization, conducted via X-Ray Diffraction patterns and Scanning Electron Microscopy images, revealed the successful fabrication of composites and fine dispersion of inclusions. Thermomechanical properties are studied via Differential Scanning Calorimetry, Thermogravimetric Analysis, Dynamic Mechanical Analysis and static mechanical tests. Hybrid composites exhibit enhanced thermal stability and improved mechanical response. Indicatively, Young’s modulus, tensile strength and fracture toughness increase from 1.26 GPa, 22.25 MPa, and 3.03 kJ/m³ for the neat epoxy to 1.39 GPa, 45.73 MPa, and 41.08 kJ/m³ for the composites with 20 or 15 parts per hundred resin per mass (phr) of Fe₃O₄, respectively. Electrical behavior is investigated via Broadband Dielectric Spectroscopy and ac conductivity measurements. The real part of dielectric permittivity reaches the value of 11.11 at 30 °C for the composite with 40 phr of Fe₃O₄. The ability to store and retrieve electric energy on the nanocomposites is examined with the following parameters: the filler content and the applied voltage under dc conditions. Retrieved energy reaches 79.23% of the stored one, for the system with 15 phr of Fe₃O₄. Magnetic response is studied via a Vibrating Sample Magnetometer. Magnetic saturation, for the system with the highest magnetic filler content, obtains the value of 25.38 Am²/kg, while pure magnetic powder attains the value of 86.75 Am²/kg. Finally, the multifunctional performance of the nanocomposites is assessed regarding all the exerted stimuli and the optimum behavior is discussed.

The present work aims at the development and characterization of carbon/polymer matrix nanocomposites, which will be able to operate as compact materials systems for energy storage and harvesting. Series of polymer nanocomposites employing different types of carbon allotropes (carbon black nanoparticles, multi-walled carbon nanotubes, graphene nanoplatelets and nanodiamonds) were developed varying the filler type and content. The energy storage ability of the systems was examined under AC and DC conditions to evaluate the influence of temperature, DC voltage and different types of filler content upon the stored and harvested energy. Experimental data confirmed the ability of the examined systems to store energy and release it on demand via a fast charge/discharge process. The addition of carbon nanoparticles significantly enhances the energy density of the systems. The coefficient of energy efficiency (n_eff) was determined for all systems, reaching up to 80% for the nanocomposite with 5 phr (parts per hundred resin per mass) carbon black content. In order to examine the optimal operational conditions of the systems, their structural integrity and thermomechanical properties were also investigated by means of static tensile tests, Dynamic Mechanical Analysis (DMA) and Differential Scanning Calorimetry (DSC).