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27 pages, 7899 KB

Open AccessArticle

Microfluidic Fabrication of TiO₂–Hydrogel Photocatalytic Composites for Water Treatment

by Sergio J. Peñas-Núñez, Diego Lecumberri, Adrián Durán and Francisco J. Peñas

Crystals 2026, 16(3), 175; https://doi.org/10.3390/cryst16030175 - 5 Mar 2026

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Abstract

Water purification and treatment methods are becoming increasingly complex due to the use of new additives, solvents, pesticides, dyes, and other emerging pollutants in industry, agriculture, and households. Consequently, the search for new water treatment techniques and materials that can help reduce this [...] Read more.

Water purification and treatment methods are becoming increasingly complex due to the use of new additives, solvents, pesticides, dyes, and other emerging pollutants in industry, agriculture, and households. Consequently, the search for new water treatment techniques and materials that can help reduce this environmental impact has become a major focus in the field of green chemistry. In this work, the photocatalytic degradation capacity of composites containing TiO₂ nanoparticles (TNPs) for the removal of organic pollutants in water was studied. The TNPs were immobilized in bio-based hydrogel microparticles, which were prepared using microfluidic techniques. The composition of the dispersed phase was optimized with a lab-on-a-chip device, resulting in composite microparticles with a narrow size distribution. UV–visible spectroscopy results indicated that increasing the concentration of TNPs in the hydrogel microparticles enhanced the photodegradation performance of the new composite. Remarkably, it was able to efficiently degrade nearly 90% of reference dyes after four adsorption–desorption cycles. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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12 pages, 2331 KB

Open AccessArticle

Structural and Proton Conduction Modifications in RbH₂PO₄ Crystals upon Heating Under Different Environments

by Cristian E. Botez and Alex D. Price

Crystals 2026, 16(2), 147; https://doi.org/10.3390/cryst16020147 - 17 Feb 2026

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Abstract

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. [...] Read more.

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. Nyquist plots collected on RDP samples sealed in a small volume (~50 mL) of dry air show a gradual increase in σ upon heating from 180 to 260 °C, but not the three-order-of-magnitude superprotonic jump observed in the Cs-based compound CsH₂PO₄ (CDP) within the same temperature range. Correspondingly, XRD measurements using synchrotron radiation (λ = 0.922 Å) on RDP crystalline powders sealed in a quartz capillary exhibit no evidence of a monoclinic-to-cubic superprotonic phase transition like the one observed in CDP. Instead, these temperature-resolved powder XRD patterns demonstrate that the intermediate-temperature RDP monoclinic phase (P2₁/m, a = 7.733 Å, b = 6.189 Å, c = 4.793 Å, and β = 109.21 deg) persists up to the melting point of the title compound. Our most significant finding comes from heating RDP under high pressure (P = 1 GPa), which leads to markedly different structural behavior. Indeed, our full profile refinements against XRD data collected on RDP crystals compressed at ~1 GPa show evidence of a polymorphic phase transition (at T_c = 300 °C) to a high-temperature cubic phase (Pm-3m, a = 4.784 Å) that is isomorphic with its CDP counterpart. This is significant, as it indicates that the superprotonic conduction in phosphate solid acids is not cation-specific, and a general highly efficient proton conduction mechanism is present in the high-temperature phases of these materials. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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18 pages, 4011 KB

Open AccessArticle

Thermodynamic Assessment of Reactions in the Sodium-Oxide Fluxed Aluminothermic Reduction of Manganese Ore with Si, Cr, and Cu Collector Metals

by Theresa Coetsee and Frederik De Bruin

Crystals 2026, 16(2), 120; https://doi.org/10.3390/cryst16020120 - 6 Feb 2026

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Abstract

This study investigates the reaction thermodynamics of the sodium oxide-fluxed aluminothermic reduction of pyrolusite-based manganese ore under self-propagating high-temperature synthesis (SHS) conditions, using Si, Cr, and Cu as collector metals. The experimental results are compared with thermochemical equilibrium calculations using FactSage 7.3 thermochemistry [...] Read more.

This study investigates the reaction thermodynamics of the sodium oxide-fluxed aluminothermic reduction of pyrolusite-based manganese ore under self-propagating high-temperature synthesis (SHS) conditions, using Si, Cr, and Cu as collector metals. The experimental results are compared with thermochemical equilibrium calculations using FactSage 7.3 thermochemistry software. Experimental mixtures were prepared with controlled additions of aluminium, sodium silicate, calcium oxide, and collector metals and heated to the ignition temperature in a muffle furnace preheated to 1350 °C. The resulting alloys and slags were analysed for bulk composition. Collector metals significantly influence alloy carbon saturation and manganese recovery. The individual reaction’s Gibbs free energy values and the gas–slag–metal equilibrium were calculated. Discrepancies between the experimental and equilibrium-predicted results highlight the kinetic factors of SHS processes, particularly with respect to aluminium uptake and manganese volatilisation. The main difference is the alloy’s aluminium uptake. The difference between the calculated and experimental aluminium levels is, in part, due to the higher partial oxygen pressure predicted in the gas–slag–metal equilibrium calculations, compared with that of the likely Al–Al₂O₃ governing reaction equilibrium. Short-circuiting of aluminium to the alloy is also a possible contributing factor. The findings provide insights into optimising feed formulations and process parameters for improved manganese recovery. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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18 pages, 1815 KB

Open AccessArticle

Influence of Isopropanol on Kinetics of Hydrogen Evolution Reaction Examined at Nickel Foam Electrodes in Alkaline Solution

by Wiktoria Abramczyk, Bogusław Pierożyński, Tomasz Mikołajczyk and Kazimierz Warmiński

Crystals 2026, 16(2), 114; https://doi.org/10.3390/cryst16020114 - 5 Feb 2026

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Abstract

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of [...] Read more.

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of 20–40 °C. Comparative HER/IPA examinations are presented for a highly catalytic polycrystalline Pt electrode. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and cathodic Tafel polarization experiments were carried out in this work, where the IPA concentrations ranged from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M. The introduction of small amounts of isopropyl alcohol into the working electrolyte noticeably facilitated the catalytic efficiency of the hydrogen evolution reaction on the surface of Ni foam electrodes. This is most likely related to the fact that IPA molecules undergo partial electrooxidation to acetone (qualitatively confirmed by GC-MS analysis) during initial CV cycling, which is believed to significantly diminish the surface tension phenomenon during the HER, thus promoting hydrogen bubble separation from the electrode surface. It should also be noted that acetone will continuously be produced at the Pt anode, making it essential to consider further migration of (CH₃)₂CO molecules to the working cell compartment. Most importantly, isopropanol was found not to undergo significant surface electrosorption on the nickel foam-based catalysts, which could otherwise significantly inhibit the hydrogen evolution reaction On the contrary, the presence of IPA in the electrolyte solution seems to have a detrimental effect on the kinetics of both the HER and the UPDH (underpotential deposition of H) processes on the surface of the polycrystalline Pt electrode, which is a superior electrochemical catalyst for HER, but highly susceptible to surface contamination. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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15 pages, 2486 KB

Open AccessArticle

Structure and Thermophysical Properties of Phase Change Materials Used in a Lithium-Ion Coin Battery Thermal Management System

by Mioara Zagrai, Olivia-Ramona Bruj, Alexandru Turza, Teodora Radu and Vasile Rednic

Crystals 2026, 16(2), 93; https://doi.org/10.3390/cryst16020093 - 28 Jan 2026

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Abstract

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 [...] Read more.

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%. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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18 pages, 8608 KB

Open AccessArticle

The Influence of Silica Template Aging Temperature on the Properties and Catalytic Activity of Nanocast Mesoporous Zirconium-Doped Ceria

by Katarina Mužina, Jakov-Stjepan Pavelić, Filip Car, Filip Brleković, Goran Dražić, Lara Mikac, Gordana Matijašić, Vesna Tomašić and Stanislav Kurajica

Crystals 2026, 16(2), 83; https://doi.org/10.3390/cryst16020083 - 24 Jan 2026

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Abstract

KIT-6 samples were prepared at hydrothermal aging temperatures of 60, 100, and 140 °C, and used as templates for nanocasting of zirconium-doped ceria. In nanocast samples, the ordered 3D structure collapsed, leaving behind nanorods with a diameter roughly in concordance with the corresponding [...] Read more.

KIT-6 samples were prepared at hydrothermal aging temperatures of 60, 100, and 140 °C, and used as templates for nanocasting of zirconium-doped ceria. In nanocast samples, the ordered 3D structure collapsed, leaving behind nanorods with a diameter roughly in concordance with the corresponding KIT-6 template pore diameter. In addition to nanocrystalline ceria, a small amount of cubic zirconia is present in the doped samples, but the formation of a solid solution was confirmed by the decrease in the ceria lattice parameter relative to bulk ceria. The specific surface areas of the nanocast samples decreased with the increase in KIT-6 template aging temperature. Ceria bandgap values were slightly blueshifted in comparison with bulk ceria, which was attributed to quantum confinement. No difference between samples concerning lattice ceria defects has been noted. Conversion curves show apparent three-stage conversion with stagnation at temperatures in the range between 250 °C and 300 °C, which is a consequence of abundant adsorption of toluene below 250 °C and desorption above 250 °C. Slight differences in catalytic activity are only due to a difference in the amount of adsorbed toluene caused by differences in the specific surface area of the samples. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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23 pages, 8282 KB

Open AccessArticle

Investigation of Copper as Collector Metal in Sodium-Oxide Fluxed Aluminothermic Reduction of Manganese Ore

by Theresa Coetsee and Frederik De Bruin

Crystals 2026, 16(1), 50; https://doi.org/10.3390/cryst16010050 - 11 Jan 2026

Cited by 1 | Viewed by 357

Abstract

Aluminothermic reduction is gaining renewed interest as an alternative processing route for the circular economy. A unique Na₂O-fluxed MnO₂ ore formulation with a small quantity of carbon reductant was applied to ensure rapid pre-reduction to MnO. This approach negates the [...] Read more.

Aluminothermic reduction is gaining renewed interest as an alternative processing route for the circular economy. A unique Na₂O-fluxed MnO₂ ore formulation with a small quantity of carbon reductant was applied to ensure rapid pre-reduction to MnO. This approach negates the pre-roasting step. The Na₂O flux enables the formation of the water-soluble compound, NaAlO₂, which enables recycling of Al₂O₃ for aluminium production. The addition of copper as a collector metal improved the overall alloy yield from 43% to 57%, which includes a 6% increase in Mn recovery to the alloy. The product alloy is a medium-carbon Fe–Mn–Si–Al–Cu complex ferroalloy that can be used as a steelmaking ferroalloy additive. The ferroalloy consists of 54% Mn, 19% Fe, 2.1% Si, 2.6% Al, 21% Cu, and 1.2% C. This carbon content is modulated by low-carbon solubility copper, despite the use of a graphite crucible. The formulated slag exhibits high Al₂O₃ solubility, enabling effective alloy–slag separation from the high Al₂O₃ content slag of 52% Al₂O₃. Gas–slag–metal equilibrium calculations for 1650 °C–1950 °C overlap with the experimentally produced alloy chemistry in %C and %Si, but not the %Al, as the uptake of aluminium exceeds the equilibrium calculation at 0.03–0.17%. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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22 pages, 8413 KB

Open AccessArticle

Characterization of Copper-Modified Clinoptilolite for the Photocatalytic Removal of Congo Red Dye from Wastewater

by Hristina Lazarova, Liliya Tsvetanova, Borislav Barbov, Stela Atanasova-Vladimirova and Aleksandar Nikolov

Crystals 2026, 16(1), 32; https://doi.org/10.3390/cryst16010032 - 30 Dec 2025

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Abstract

In this study, the photocatalytic performance of natural clinoptilolite was enhanced through copper modification, achieved via ion exchange followed by KOH-induced precipitation, leading to materials with different copper speciation. Physicochemical characterization using WDXRF, PXRD, FTIR and N₂ physisorption revealed a transition from [...] Read more.

In this study, the photocatalytic performance of natural clinoptilolite was enhanced through copper modification, achieved via ion exchange followed by KOH-induced precipitation, leading to materials with different copper speciation. Physicochemical characterization using WDXRF, PXRD, FTIR and N₂ physisorption revealed a transition from exchanged Cu²⁺ species at low loading to the formation of copper-bearing phases such as brochantite, Cu(OH)₂ and CuO at higher alkalinity. The Cu-modified samples were evaluated for the photocatalytic degradation of Congo red under UV irradiation. Among them, sample NZ-Cu3 exhibited the highest activity, achieving approximately 91% dye degradation within 30–40 min. Kinetic analysis demonstrated that the degradation process is better described by the pseudo-second-order model, indicating that chemisorption plays a dominant role. Radical scavenger experiments revealed that photogenerated holes (h⁺) are the primary reactive species responsible for dye degradation, while hydroxyl radicals contribute to a lesser extent. The enhanced photocatalytic performance is attributed to the synergistic effect of photocatalytic degradation, improved charge separation and the presence of surface copper species, highlighting Cu-modified clinoptilolite as a promising low-cost photocatalyst for wastewater treatment. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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12 pages, 1618 KB

Open AccessArticle

Effect of Mg Alloying on the Mechanical Properties and Phase Transformation of Lithium

by Nicolás Amigo, Rodrigo Vargas-Osorio, Facundo Esquivel and Gonzalo Gutiérrez

Crystals 2026, 16(1), 31; https://doi.org/10.3390/cryst16010031 - 30 Dec 2025

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Abstract

This work presents an atomistic investigation of the structural and mechanical properties of Li–Mg alloys with 5, 10, and 20 at.% Mg using Monte Carlo and Molecular Dynamics simulations, elastic constant calculations, and uniaxial tensile tests. Structural equilibration revealed that Mg species promote [...] Read more.

This work presents an atomistic investigation of the structural and mechanical properties of Li–Mg alloys with 5, 10, and 20 at.% Mg using Monte Carlo and Molecular Dynamics simulations, elastic constant calculations, and uniaxial tensile tests. Structural equilibration revealed that Mg species promote enhanced relaxation and a tendency to form B2-type ordering. The elastic constants showed that Mg primarily increases the longitudinal stiffness while the shear-related components remained nearly unchanged. Derived mechanical properties confirm this strengthening trend, and comparison with recent experimental data shows good qualitative agreement. Tensile tests showed composition-dependent deformation mechanisms: the 0 and 5 at.% Mg samples underwent complete BCC-to-FCC transformation accompanied by strong stress reduction, the 10 at.% Mg alloy exhibited a similar transition while preserving positive stresses, and the 20 at.% Mg alloy displayed an abrupt shear-band instability that interrupted the transformation. These results provide insights into the role of Mg as an element that enhances the structural stability and mechanical stiffness of Li-Mg alloys, supporting their improved performance as electrode materials. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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27 pages, 11334 KB

Open AccessArticle

Study of Bushing Formation in the Process of Joining Thin-Walled Metals and Fiber-Reinforced Composites Using Thermal Drilling

by Anna Guzanová, Dagmar Draganovská, Milan Fiľo and Teodor Tóth

Crystals 2026, 16(1), 2; https://doi.org/10.3390/cryst16010002 - 19 Dec 2025

Viewed by 394

Abstract

This study addresses the issue of adapting the thermal drilling process for joining dissimilar thin-walled materials—sheets made of non-ferrous metal alloys and polymer composites with a thermoplastic matrix reinforced with glass and carbon fibers—without the use of connecting elements and without disrupting the [...] Read more.

This study addresses the issue of adapting the thermal drilling process for joining dissimilar thin-walled materials—sheets made of non-ferrous metal alloys and polymer composites with a thermoplastic matrix reinforced with glass and carbon fibers—without the use of connecting elements and without disrupting the continuity of the reinforcing fibers. An extensive metallographic study was conducted on bushings formed in thin metal sheets made of EN AW 6082 T6 aluminum alloy and AZ91 magnesium alloy obtained during separate drilling procedures. Experiments were also performed where the metal sheet and composite material overlapped, using both direct and sequential drilling above the melting point of the polymer matrix, applying various process parameters. The dimensions of the resulting bushings and the suitability of their profile for joining with composites were evaluated. The results suggest the possibility of joining metals and fiber composites through thermal drilling, and suitable joining process parameters and conditions are specified. To limit composite delamination, it is advisable to make a hem flange on the reverse side of the joints. CT scans confirmed the deflection of fibers around the hole in the composite without compromising their integrity. The load-bearing capacity of the joints and the possibility of creating hybrid mechanical–adhesive joints between these materials are the subject of Part Two of this study. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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33 pages, 6669 KB

Open AccessEditor’s ChoiceArticle

New Scalable Electrosynthesis of Distinct High Purity Graphene Nanoallotropes from CO₂ Enabled by Transition Metal Nucleation

by Kyle Hofstetter, Gad Licht and Stuart Licht

Crystals 2025, 15(8), 680; https://doi.org/10.3390/cryst15080680 - 25 Jul 2025

Cited by 2 | Viewed by 2144

Abstract

The electrochemical conversion of CO₂ into high-purity Graphene NanoCarbon (GNC) materials provides a compelling path to address climate change while producing economically valuable nanomaterials. This work presents the progress and prospects of new large-scale syntheses of GNC allotropes via the C2CNT (CO [...] Read more.

The electrochemical conversion of CO₂ into high-purity Graphene NanoCarbon (GNC) materials provides a compelling path to address climate change while producing economically valuable nanomaterials. This work presents the progress and prospects of new large-scale syntheses of GNC allotropes via the C2CNT (CO₂ to Carbon Nano Technology) process. The C2CNT molten carbonate electrolysis technique enables the formation of Carbon NanoTubes (CNTs), Magnetic CNTs (MCNTs), Carbon Nano-Onions (CNOs), Carbon Nano-Scaffolds (CNSs), and Helical CNTs (HCNTs) directly from atmospheric or industrial CO₂. We discuss the morphology control enabled through variations in electrolyte composition, temperature, current density, and nucleation additives. We present results from scaled operations reaching up to 1000 tons/year CO₂ conversion and propose design approaches to reach megaton scales to support climate mitigation and GNC mass production. The products demonstrate high crystallinity, as evidenced by Raman, XRD, SEM, and TGA analyses, and offer promising applications in electronics, construction, catalysis, and medical sectors. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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20 pages, 3209 KB

Open AccessEditor’s ChoiceArticle

Experimental Evaluation of GAGG:Ce Crystalline Scintillator Properties Under X-Ray Radiation

by Anastasios Dimitrakopoulos, Christos Michail, Ioannis Valais, George Fountos, Ioannis Kandarakis and Nektarios Kalyvas

Crystals 2025, 15(7), 590; https://doi.org/10.3390/cryst15070590 - 23 Jun 2025

Cited by 2 | Viewed by 2527

Abstract

The scope of this study was to evaluate the response of Ce-doped gadolinium aluminum gallium garnet (GAGG:Ce) crystalline scintillator under medical X-ray irradiation for medical imaging applications. A 10 × 10 × 10 mm³ crystal was irradiated at X-ray tube voltages ranging [...] Read more.

The scope of this study was to evaluate the response of Ce-doped gadolinium aluminum gallium garnet (GAGG:Ce) crystalline scintillator under medical X-ray irradiation for medical imaging applications. A 10 × 10 × 10 mm³ crystal was irradiated at X-ray tube voltages ranging from 50 kVp to 150 kVp. The crystal’s compatibility with several commercially available optical photon detectors was evaluated using the spectral matching factor (SMF) along with the absolute efficiency (AE) and the effective efficiency (EE). In addition, the energy-absorption efficiency (EAE), the quantum-detection efficiency (QDE) as well as the zero-frequency detective quantum detection efficiency DQE(0) were determined. The crystal demonstrated satisfactory AE values as high as 26.3 E.U. (where 1 E.U. = 1 μW∙m⁻²/(mR∙s⁻¹)) at 150 kVp, similar, or in some cases, even superior to other cerium-doped scintillator materials. It also exhibits adequate DQE(0) performance ranging from 0.99 to 0.95 across all the examined X-ray tube voltages. Moreover, it showed high spectral compatibility with commonly used photoreceptors in modern day such as complementary metal–oxide–semiconductors (CMOS) and charge-coupled-devices (CCD) with SMF values of 0.95 for CCD with broadband anti-reflection coating and 0.99 for hybrid CMOS blue. The aforementioned properties of this scintillator material were indicative of its superior efficiency in the examined medical energy range, compared to other commonly used scintillators. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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12 pages, 3008 KB

Open AccessEditor’s ChoiceArticle

Structural, Thermophysical, and Radiation Shielding Properties of Lead–Bismuth Eutectic (LBE) Synthesized by Induction Melting

by Radu Cristian Gavrea, Emanoil Surducan, Răzvan Hirian, Mioara Zagrai and Vasile Rednic

Crystals 2025, 15(6), 581; https://doi.org/10.3390/cryst15060581 - 19 Jun 2025

Cited by 1 | Viewed by 1572

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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11 pages, 1970 KB

Open AccessArticle

Electrochemical and Photoresponsive Behavior of MOF-Derived V₂O₃/C Cathodes for Zinc-Ion Batteries: ZIF-8 as a Nanoscale Reactor and Carbon Source

by Byoungnam Park

Crystals 2025, 15(5), 436; https://doi.org/10.3390/cryst15050436 - 3 May 2025

Cited by 4 | Viewed by 1475

Abstract

In this study, a V₂O₃/carbon (V₂O₃/C) composite was synthesized using zeolitic imidazolate framework 8 (ZIF-8) as both a sacrificial template and in situ carbon source. The composite was prepared by mixing ZIF-8 with NH₄ [...] Read more.

In this study, a V₂O₃/carbon (V₂O₃/C) composite was synthesized using zeolitic imidazolate framework 8 (ZIF-8) as both a sacrificial template and in situ carbon source. The composite was prepared by mixing ZIF-8 with NH₄VO₃, followed by annealing at 800 °C, resulting in nanoscale V₂O₃ embedded in a nitrogen-doped porous carbon matrix. Fabricated into a thin-film cathode via alternating current electrophoretic deposition (AC-EPD), the composite exhibited mixed capacitive–diffusion-controlled charge storage behavior with favorable Zn²⁺ transport kinetics, as confirmed by a b-value analysis (b = 0.72) and diffusion coefficient measurements (D_Zn = 6.2 × 10⁻¹¹ cm²/s). Notably, the cathode displayed photoresponsive redox behavior under 450 nm illumination, enhancing the Zn-ion kinetics. These findings demonstrate the potential of MOF-derived V₂O₃/C composites for high-performance, photo-enhanced zinc-ion energy storage applications. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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18 pages, 6005 KB

Open AccessArticle

High Optical Performance TiO₂- and SiO₂-Based Composites with CuO and SrO Additions

by Mioara Zagrai, Izabell Craciunescu, Alexandrina Nan, Septimiu Tripon, Alexandru Turza and Vasile Rednic

Crystals 2025, 15(4), 343; https://doi.org/10.3390/cryst15040343 - 5 Apr 2025

Cited by 3 | Viewed by 1480

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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Review

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26 pages, 550 KB

Open AccessReview

Recovery of Critical Metals from Waste-Printed Circuit Boards for Sustainable Energy Transition

by Lucian-Cristian Pop, Szabolcs Szima and Szabolcs Fogarasi

Crystals 2026, 16(1), 67; https://doi.org/10.3390/cryst16010067 - 20 Jan 2026

Viewed by 685

Abstract

It is undeniable that rapid population increase coupled with growing resource constraints are making the demand for smart and sustainable solutions more urgent than ever to secure future resources for the transition to sustainable energy production. To address these issues, it is necessary [...] Read more.

It is undeniable that rapid population increase coupled with growing resource constraints are making the demand for smart and sustainable solutions more urgent than ever to secure future resources for the transition to sustainable energy production. To address these issues, it is necessary to define innovative approaches that can exploit more efficiently and extensively the resources we have at our disposal. Consequently, this paper provides an overview of the potential benefits of processing waste-printed circuit boards (WPCBs) that are generated in large quantities and, due to their high metal content, can emerge as an adequate and profitable supply of critical metals, such as copper, aluminum, and nickel, which are essential for green energy transition. The review promotes the idea of industrial symbiosis as a concept that goes beyond circular economy and can integrate WPCB treatment and manufacturing processes related to sustainable energy transition, although they are different industrial sectors that can be even regionally separated. Major metal recovery processes from WPCBs are examined and discussed, with the primary focus on the performances of copper, aluminum, and nickel production, while additional metals relevant to the energy transition are also highlighted. Finally, the review paper argues and exemplifies that the recovered metals from WPCBs have the required properties to be supplied into the manufacturing processes of wind turbines, solar panels, and lithium-ion batteries. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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22 pages, 4259 KB

Open AccessReview

Stoichiometry-Controlled Surface Reconstructions in Epitaxial ABO₃ Perovskites for Sustainable Energy Applications

by Habib Rostaghi Chalaki, Ebenezer Seesi, Gene Yang, Mohammad El Loubani and Dongkyu Lee

Crystals 2026, 16(1), 37; https://doi.org/10.3390/cryst16010037 - 1 Jan 2026

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Abstract

ABO₃ perovskite oxides are a versatile class of materials whose surfaces and interfaces play essential roles in sustainable energy technologies, including catalysis, solid oxide fuel and electrolysis cells, thermoelectrics, and energy-relevant oxide electronics. The interplay between point defects and surface reconstructions strongly [...] Read more.

ABO₃ perovskite oxides are a versatile class of materials whose surfaces and interfaces play essential roles in sustainable energy technologies, including catalysis, solid oxide fuel and electrolysis cells, thermoelectrics, and energy-relevant oxide electronics. The interplay between point defects and surface reconstructions strongly affects interfacial stability, charge transport, and catalytic activity under operating conditions. This review summarizes recent progress in understanding how oxygen vacancies, cation nonstoichiometry, and electronic defects couple to atomic-scale surface rearrangements in representative perovskite systems. We first revisit Tasker’s classification of ionic surfaces and clarify how defect chemistry provides compensation mechanisms that stabilize otherwise polar or metastable terminations. We then discuss experimental and theoretical insights into defect-mediated reconstructions on perovskite surfaces and how they influence the performance of energy conversion devices. Finally, we conclude with a perspective on design strategies that leverage defect engineering and surface control to enhance functionality in energy applications, aiming to connect fundamental surface science with practical materials solutions for the transition to sustainable energy. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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