Mioara Zagrai

In this study, a series of xFe₂O₃–Na₂O–CaO–SiO₂ glass-ceramics containing 0–28 wt.% Fe₂O₃ were prepared via the conventional melt-quenching technique. The resulting samples, designated S1–S4, were subsequently subjected to thermal treatment and investigated with respect to their structural, thermal, and optical characteristics. Differential scanning calorimetry analysis revealed the influence of the Fe₂O₃ concentration on the glass transition temperature and crystallization behavior of the samples. Structural analysis of the samples revealed that crystalline silicate and iron oxide phases constituted the predominant crystalline phases, with their overall crystallinity being strongly dependent on the Fe₂O₃ content and thermal treatment. Fourier transform infrared spectroscopy evidenced structural modifications of the silicate network induced by iron incorporation, while ultraviolet–visible–near infrared spectroscopy highlighted the presence of Fe²⁺/Fe³⁺ ions and their associated electronic transitions. The results indicate that increasing the Fe₂O₃ content significantly affects the network structure, redox state, and thermal behavior of the glass-ceramic system, leading to enhanced absorption properties.

Flexible electrode materials with tailored electrical and mechanical properties are essential for reliable electrocardiographic (ECG) sensing. In this work, p-toluenesulfonic-acid-doped polypyrrole (PPy–TSA) films were modified using polymeric and inorganic fillers, as well as their combinations (polyethylene glycol, graphene, carbon nanotubes, and zeolite), to tune their functional performance. The reference PPy–TSA film exhibits typical morphological and chemical characteristics of doped polypyrrole and serves as a reliable baseline for comparison. All composite films retain electrical conductivity within the range required for ECG applications while showing improved mechanical compliance (i.e., enhanced ability to conform to the skin and sustain deformation). Based on the optimized balance between electrical and mechanical properties, flexible ECG electrodes were fabricated using the TSA-doped PPy-based composite film. ECG recordings obtained with the several proposed electrodes show good agreement with those acquired using a commercial ECG electrode, demonstrating the potential of PPy-based composite films for flexible bioelectronic sensing applications.

Flexible electrode materials with tailored electrical and mechanical properties are essential for reliable electrocardiographic (ECG) sensing. In this work, p-toluenesulfonic-acid-doped polypyrrole (PPy–TSA) films were modified using polymeric and inorganic fillers, as well as their combinations (polyethylene glycol, graphene, carbon nanotubes, and zeolite), to tune their functional performance. The reference PPy–TSA film exhibits typical morphological and chemical characteristics of doped polypyrrole and serves as a reliable baseline for comparison. All composite films retain electrical conductivity within the range required for ECG applications while showing improved mechanical compliance. Based on the optimized balance between electrical and mechanical properties, flexible ECG electrod were fabricated using the TSA doped PPy based composite film. ECG recordings obtained with the several proposed electrodes show good agreement with those acquired using a commercial ECG electrode, demonstrating the potential of PPy-based composite films for flexible bioelectronic sensing applications.

Phase change materials (PCMs) have emerged as an innovative solution in thermal energy storage and thermal management systems (TMS) owing to their outstanding latent heat of fusion during the phase change process. This study is especially addressed to the battery TMS based on Organic PCMs for fast charging/discharging applications of lithium-ion batteries (LIBs). These fast processes generate excessive heat during operation, degrade battery performance, decrease energy efficiency, and reduce the lifespan and safety of batteries. Organic PCMs exhibit desirable properties, including high latent heat capacity, good thermal characteristics, low cost, and ease of integration. The major challenge for the successful application of organic PCM comprises its low thermal conductivity, which impacts the heat storage and release rates. PCM-based Paraffin Wax (PW) has been designed by including expanded graphite (EG) as a high thermal conductivity additive in high latent heat of paraffin wax. Experiments focused on the effects of heating methods (microwaves/S-type EG composition and conventional electric oven/S′-type EG composition) of expandable graphite on the thermophysical properties of different PW/EG composites. The crystal and chemical structure of the study samples were analyzed by X-ray diffraction and Fourier-Transform Infrared spectroscopy. The battery module created with PW/EG composites were ample examined using charging/discharging experiments at five different C-rates. The effect of current rates on battery surface temperature is investigated in two cases: with PCM cooling and with air cooling. A 20.43% decrease in battery temperature is found at 5C rate with PCM cooling and a maximum reduction in battery charging time of 43.77%.

Lead–bismuth eutectic alloy (LBE, Pb_44.5Bi_55.5) has emerged as a promising candidate for use in advanced nuclear and solar energy systems due to its favorable thermophysical characteristics and radiation shielding capabilities. The aim of this research is to assess the applicability of the induction melting technique to synthesize LBE. This paper presents a comprehensive evaluation of the structural, thermophysical, and radiation shielding properties of the obtained LBE sample. Various techniques were employed to investigate the solid-to-liquid eutectic transformation, phase composition, morphology, and homogeneity of the obtained material. Experimental and theoretical determinations on density, void, molar volume, thermal conductivity, heat capacity, thermal diffusivity, and electrical conductivity were performed. Radiation shielding performance over photon energies ranging from 0.015 to 15 MeV was simulated using the Phy-X/PSD program. The results revealed the eutectic structure comprising Pb₇Bi₃ and Bi phases with near-ideal stoichiometry and a melting point of 127.6 °C. The alloy demonstrated a small void that corresponds to a high degree of sample compaction, high specific heat capacity, moderate thermal conductivity, low thermal diffusivity, and effective radiation shielding. These findings confirm that LBE obtained by the induction melting technique possesses the necessary structural stability and functional properties for integration into nuclear reactor and solar thermal technologies.

Our research aims to determine the optical properties of binary composites based on TiO₂ and SiO₂ oxides combined with additional metal oxides such as CuO and SrO. The inclusion of CuO and SrO together with TiO₂ and SiO₂ nanoparticles is driven by their ability to introduce intermediate energy levels in the forbidden band, acting as electron traps that reduce the recombination rate and increase the efficiency of solar conversion. Morphological and structural characterization of the materials was carried out to evidence the homogeneity of the final composite materials as well as their high specific surface area. Additionally, an extensive characterization of the optical properties was performed, revealing that the optical parameters of the studied samples depend on their composition. The results indicate that the optical performance of TiO₂-CuO and SiO₂-SrO composites is significantly superior to that of the pure sample. Therefore, these materials are proposed as promising candidates for enhancing the efficiency of solar cells.

This study explores the physical, radiation shielding, optical, and photoluminescent properties of PbO₂-SiO₂-based glass systems. Traditional radiation shielding materials, like lead and concrete, face challenges due to toxicity and weight. Glass materials provide an alternative, offering transparency and efficiency. Four glass systems were analyzed: PbO₂-SiO₂ (PS), PbO₂-SiO₂-CeO₂ (PSC), PbO₂-SiO₂-Eu₂O₃ (PSE), and PbO₂-SiO₂-Yb₂O₃ (PSY). The results show that rare earth elements densify the glass network, thereby enhancing radiation attenuation properties, quantified through parameters like the linear attenuation coefficient (μ), the half-value layer (HVL), and the mean free path (MFP). The PSY system exhibited the best shielding properties, demonstrating its potential for use in gamma ray shielding. Samples PS0–PS3 revealed semiconducting behavior and may be considered a promising host matrix for solar cells and w-LED applications.

The present study aimed to test the solubility of SiO₂ in a PbO₂ host glass matrix. The new glass system with chemical composition xSiO₂∙(100-x)∙PbO₂ (in mol%) was obtained at low temperature using the melt-quenching technique. The method proposed for the characterization of the glass system includes X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), inductively coupled plasma mass spectrometry (ICP-Ms), Fourier Transform Infrared (FTIR), and Electron Spin Resonance (ESR) spectroscopy. Understanding the relationship between the oxide composition, structure, chemical durability, and thermal characteristics of obtained materials is essential for further developing the new glass crystalline material (GCM) compositions with specific desired properties.

In this paper, we propose a simple procedure to obtain multi-walled carbon nanotubes (MWCNTs) decorated with TiO₂–Ag nanoparticles (MWCNT–TiO₂–Ag). The MWCNTs were decorated with TiO₂–Ag via combined functionalization with –OH and –COOH groups and a polymer-wrapping technique using poly(allylamine)hydrochloride (PAH). TiO₂-modified Ag nanoparticles were synthesized via the Pechini method using a mixture of acetylacetonate-modified titanium (IV) isopropoxide with silver nitrate (with Ag⁺/Ti⁴⁺ atomic ratios of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) and L(+)-ascorbic acid as reducing agents. XRD analysis revealed the formation of nanocomposites containing CNT, anatase TiO₂, and Ag. The presence of nanoparticles on the MWCNT surfaces was determined using TEM. The morphology of the TiO₂–Ag nanoparticles on the MWCNT surfaces was also determined using TEM. UV–Vis investigations revealed that an increase in the ratio between Ag⁺ and Ti⁴⁺ decreased the band gap energy of the samples. The characteristic vibrations of the TiO₂, Ag, and C atoms of the graphite were identified using Raman spectroscopy. The photocatalytic activity of the MWCNT–TiO₂–Ag nanocomposite was assessed by examining the degradation of Allura Red (E129) aqueous solution under UV irradiation. The dye photodegradation process followed a pseudo-first-order kinetic with respect to the Langmuir–Hinshelwood reaction mechanism. The spin-trapping technique evidenced that •O²⁻ was the main species generated responsible for the Allura Red degradation.