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19 pages, 6729 KB  
Article
High-Entropy (Ce0.2Pr0.2Zn0.2Nd0.2Tb0.2)2Zr2O7 Zirconate Pyrochlore: A Promising Photocatalyst for Diverse Environmental Applications
by Mariappan Anandkumar, Shanmugavel Sudarsan, Venkata Ramesh Naganaboina, Naveen Kumar Bandari, Ksenia Sergeevna Litvinyuk, Shiv Govind Singh and Evgeny Alekseevich Trofimov
Nanomaterials 2025, 15(21), 1668; https://doi.org/10.3390/nano15211668 - 2 Nov 2025
Viewed by 375
Abstract
Although fast-paced ongoing industrial growth, on the one hand, enhances the lifestyle of the population, on the other hand, it affects human health and the environment as a result of the discharge of pollutants. To address this, designing a novel and effective photocatalyst [...] Read more.
Although fast-paced ongoing industrial growth, on the one hand, enhances the lifestyle of the population, on the other hand, it affects human health and the environment as a result of the discharge of pollutants. To address this, designing a novel and effective photocatalyst is necessary to mitigate increasing environmental pollutants. In the present work, we aim to synthesize a single-phase high-entropy zirconate pyrochlore oxide (Ce0.2Pr0.2Zn0.2Nd0.2Tb0.2)2Zr2O7 using a modified Pechini method. The physicochemical properties of the prepared nanoparticles were investigated using X-ray diffraction, UV-visible spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic properties were examined using cationic dye (methylene blue), anionic dye (Congo red), and Cr(VI). Photocatalytic degradation experiments demonstrate exceptional efficiency in the removal of persistent organic pollutants. The photocatalytic results indicate that the prepared high-entropy (Ce0.2Pr0.2Zn0.2Nd0.2Tb0.2)2Zr2O7 zirconate pyrochlore oxide could effectively degrade dyes and reduce Cr(VI). Radical trapping experiments indicate that the degradation of dyes was driven by the hydroxyl radicals, superoxide radicals, and holes. Furthermore, the position of the valence band and conduction band promoted efficient photocatalytic reaction kinetics. The prepared photocatalyst remains structurally stable and can be reused three times without losing activity. Full article
(This article belongs to the Special Issue Semiconductor-Based Nanomaterials for Catalytic Applications)
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21 pages, 1765 KB  
Review
A Critical Review of Recent Inorganic Redox Flow Batteries Development from Laboratories to Industrial Applications
by Chivukula Kalyan Sundar Krishna and Yansong Zhao
Batteries 2025, 11(11), 402; https://doi.org/10.3390/batteries11110402 - 1 Nov 2025
Viewed by 559
Abstract
Redox flow batteries (RFBs) are an emerging class of large-scale energy storage devices, yet the commercial benchmark—vanadium redox flow batteries (VRFBs)—is highly constrained by a modest open-circuit potential (1.26 V) while posing an expensive and volatile material procurement costs. This review focuses on [...] Read more.
Redox flow batteries (RFBs) are an emerging class of large-scale energy storage devices, yet the commercial benchmark—vanadium redox flow batteries (VRFBs)—is highly constrained by a modest open-circuit potential (1.26 V) while posing an expensive and volatile material procurement costs. This review focuses on recent progress in diversifying redox-active species to overcome these limits, highlighting chemistries that increase overall cell voltage, energy density, and efficiency while maintaining long cycle life and safety. The study dwells deeper into manganese-based systems (e.g., Mn/Ti, Mn/V, Mn/S, M/Zn) that leverage Mn’s high positive potential while addressing Mn(III) disproportionation reactions; iron-based hybrids (Fe/Cr, Fe/Zn, Fe/Pb, Fe/V, Fe/S, Fe/Cd) that exploit the low cost, and its abundance, along with membrane and electrolyte strategies to prevent the potential issue involving crossover; cerium-anchored catholytes (Ce/Pb, V/Ce, Eu/Ce, Ce/S, Ce/Zn) that deliver high operational voltage by implementing an acid-base media, along with selective zeolite membranes; and halide systems (Zn–I, Zn–Br, Sn–Br, polysulfide–bromine/iodide) that combine fast redox kinetics and high solubility with advances such as carbon-coated membranes, bromine complexation, and ambipolar electrolytes. Across these various families of RFBs, the review highlights the modifications made to the flow-fields, membranes, and electrodes by utilizing a zero-gap serpentine flow field, sulfonated poly(ether ether ketone) (SPEEK) membranes, carbon-modified and zeolite separators, electrolyte additives to enhance the voltage (VE%), and thereby energy (EE%) efficiency, while reducing the overall system cost. These modifications to the existing RFB technology offer a promising alternative to traditional approaches, paving the way for improved performance and widespread adoption of RFB technology in large-scale grid-based energy storage solutions. Full article
(This article belongs to the Special Issue Batteries: 10th Anniversary)
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14 pages, 6629 KB  
Article
Near-Zero Thermal Expansion and High Strength in Multi-Phase La0.6Ce0.4(Fe0.91Co0.09)11.9Si1.1/Ag Compounds Produced Through Spark Plasma Sintering
by Yuyu Wang, Kai Xu, Hanyang Qian, Rui Cai, Xiang Lu and Jian Liu
Metals 2025, 15(10), 1131; https://doi.org/10.3390/met15101131 - 11 Oct 2025
Viewed by 411
Abstract
The significant negative thermal expansion (NTE) that occurs in La(Fe,Si)13-based alloys during magnetic transition make them promising to combine with positive thermal expansion (PTE) materials to obtain near-zero thermal expansion (NZTE) materials. However, La(Fe,Si)13-based alloys with NTE generally show [...] Read more.
The significant negative thermal expansion (NTE) that occurs in La(Fe,Si)13-based alloys during magnetic transition make them promising to combine with positive thermal expansion (PTE) materials to obtain near-zero thermal expansion (NZTE) materials. However, La(Fe,Si)13-based alloys with NTE generally show intrinsic poor mechanical properties. Here, thermal expansion properties are optimized by adding Ag in La0.6Ce0.4(Fe0.91Co0.09)11.9Si1.1 to form a multi-phase structure exhibiting enhanced compressive strength. Through spark plasma sintering (SPS) and annealing, the samples consisted of α-Fe(Co,Si), NaZn13-type, and LaAg2 phases. When the annealing temperature reaches 1323 K, LaAg2 disappears and is replaced by La2O3. The LaAg2 phase and α-Fe(Co,Si) phase contribute as PTE materials to compensate for the NTE of the NaZn13-type phase. Near-zero thermal expansion was achieved in the temperature range of 240–294 K, with a coefficient of thermal expansion (CTE) of 3.5 ppm/K at a 9.581 at.% Ag content. Benefiting from the uniform phase distribution and coordinated deformation, the samples obtained high mechanical strengths, with fracture stresses of 1481.1 MPa for the 15 wt.% Ag sample. This work provides a promising route for high-strength and near-zero thermal expansion Ag/La(Fe,Si)13 composites. Full article
(This article belongs to the Section Metallic Functional Materials)
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45 pages, 7902 KB  
Review
Artificial Intelligence-Guided Supervised Learning Models for Photocatalysis in Wastewater Treatment
by Asma Rehman, Muhammad Adnan Iqbal, Mohammad Tauseef Haider and Adnan Majeed
AI 2025, 6(10), 258; https://doi.org/10.3390/ai6100258 - 3 Oct 2025
Viewed by 1490
Abstract
Artificial intelligence (AI), when integrated with photocatalysis, has demonstrated high predictive accuracy in optimizing photocatalytic processes for wastewater treatment using a variety of catalysts such as TiO2, ZnO, CdS, Zr, WO2, and CeO2. The progress of research [...] Read more.
Artificial intelligence (AI), when integrated with photocatalysis, has demonstrated high predictive accuracy in optimizing photocatalytic processes for wastewater treatment using a variety of catalysts such as TiO2, ZnO, CdS, Zr, WO2, and CeO2. The progress of research in this area is greatly enhanced by advancements in data science and AI, which enable rapid analysis of large datasets in materials chemistry. This article presents a comprehensive review and critical assessment of AI-based supervised learning models, including support vector machines (SVMs), artificial neural networks (ANNs), and tree-based algorithms. Their predictive capabilities have been evaluated using statistical metrics such as the coefficient of determination (R2), root mean square error (RMSE), and mean absolute error (MAE), with numerous investigations documenting R2 values greater than 0.95 and RMSE values as low as 0.02 in forecasting pollutant degradation. To enhance model interpretability, Shapley Additive Explanations (SHAP) have been employed to prioritize the relative significance of input variables, illustrating, for example, that pH and light intensity frequently exert the most substantial influence on photocatalytic performance. These AI frameworks not only attain dependable predictions of degradation efficiency for dyes, pharmaceuticals, and heavy metals, but also contribute to economically viable optimization strategies and the identification of novel photocatalysts. Overall, this review provides evidence-based guidance for researchers and practitioners seeking to advance wastewater treatment technologies by integrating supervised machine learning with photocatalysis. Full article
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14 pages, 1352 KB  
Article
Ecological Imprint of Rare Earth Mining on Microbial Communities and Water Quality Across Depth and Distance Gradients in Ganzhou, China
by Yian Wang, Fei Shi, Fengxiang Lang, Guohua Wang, Yan Mao, Yingjie Xiao, Li Yin, Genhe He and Yonghui Liao
Microorganisms 2025, 13(10), 2236; https://doi.org/10.3390/microorganisms13102236 - 24 Sep 2025
Viewed by 659
Abstract
Rare earth element (REE) mining exerts profound impacts on aquatic ecosystems, yet the microbial community responses and water quality under such stress remain underexplored. In this study, the surface (0.2 m) and subsurface (1.0 m) water along a spatial transect from proximal to [...] Read more.
Rare earth element (REE) mining exerts profound impacts on aquatic ecosystems, yet the microbial community responses and water quality under such stress remain underexplored. In this study, the surface (0.2 m) and subsurface (1.0 m) water along a spatial transect from proximal to distal points was investigated in a REE-mining area of Ganzhou, China. Physicochemical analyses revealed pronounced gradients of nitrogen (e.g., NH4+−N, NO3−N), heavy metals (e.g., Mn, Zn, Pb), and REEs (e.g., La, Nd, Ce), with higher accumulation near mining sources and partial attenuation downstream. Dissolved oxygen and redox potential indicated mildly reducing conditions at contaminated points, potentially promoting denitrification and altering nitrogen cycling. Metagenomic sequencing showed significant shifts in microbial community composition, with enrichment of metal- and nitrogen-tolerant taxa, and key denitrifiers (e.g., Acidovorax, Bradyrhizobium, Rhodanobacter), particularly at upstream polluted points. KEGG-based gene annotation highlighted dynamic nitrogen transformations mediated by multiple pathways, including nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and nitrogen fixation. Notably, genes associated with nitrite and nitrate reduction (e.g., nir, nar, nrf) were enriched near mining sources, indicating enhanced nitrogen conversion potential, while downstream activation of nitrogen-fixing genes suggested partial ecosystem recovery. Meanwhile, some microbial such as Variovorax carried metal tolerant genes (e.g., ars, chr, cnr). These findings demonstrate that REE and heavy metal contamination restructure microbial networks, modulate nitrogen cycling, and create localized ecological stress gradients. This study provides a comprehensive assessment of mining-related water pollution, microbial responses, and ecological risks, offering valuable insights for monitoring, restoration, and sustainable management of REE-impacted aquatic environments. Full article
(This article belongs to the Section Environmental Microbiology)
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52 pages, 7164 KB  
Review
Binary Oxide Ceramics (TiO2, ZnO, Al2O3, SiO2, CeO2, Fe2O3, and WO3) for Solar Cell Applications: A Comparative and Bibliometric Analysis
by Yana Suchikova, Serhii Nazarovets, Marina Konuhova and Anatoli I. Popov
Ceramics 2025, 8(4), 119; https://doi.org/10.3390/ceramics8040119 - 23 Sep 2025
Cited by 3 | Viewed by 1880
Abstract
Binary oxide ceramics have emerged as key materials in solar energy research due to their versatility, chemical stability, and tunable electronic properties. This study presents a comparative analysis of seven prominent oxides (TiO2, ZnO, Al2O3, SiO2 [...] Read more.
Binary oxide ceramics have emerged as key materials in solar energy research due to their versatility, chemical stability, and tunable electronic properties. This study presents a comparative analysis of seven prominent oxides (TiO2, ZnO, Al2O3, SiO2, CeO2, Fe2O3, and WO3), focusing on their functional roles in silicon, perovskite, dye-sensitized, and thin-film solar cells. A bibliometric analysis covering over 50,000 publications highlights TiO2 and ZnO as the most widely studied materials, serving as electron transport layers, antireflective coatings, and buffer layers. Al2O3 and SiO2 demonstrate highly specialized applications in surface passivation and interface engineering, while CeO2 offers UV-blocking capability and Fe2O3 shows potential as an absorber material in photoelectrochemical systems. WO3 is noted for its multifunctionality and suitability for scalable, high-rate processing. Together, these findings suggest that binary oxide ceramics are poised to transition from supporting roles to essential components of stable, efficient, and environmentally safer next-generation solar cells. Full article
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17 pages, 1878 KB  
Article
Transition Metal Exchanged β Zeolites: CoM/β (M = Zn, Ce, and Cu) as Oxygen Electrode in Alkaline Media
by Jadranka Milikić, Katarina Rondović, Ljiljana Damjanović-Vasilić, Vladislav Rac, Rastko Vasilić and Dalibor Stanković
Processes 2025, 13(9), 2996; https://doi.org/10.3390/pr13092996 - 19 Sep 2025
Viewed by 396
Abstract
The zeolite structure, with its precisely distinct pores, settled cages, and adsorption sites, enables the formation and stabilization of isolated metal centers. These well-defined structures make metal-loaded zeolites promising catalysts. Three different β zeolites were synthesized by an aqueous ion-exchange procedure, firstly with [...] Read more.
The zeolite structure, with its precisely distinct pores, settled cages, and adsorption sites, enables the formation and stabilization of isolated metal centers. These well-defined structures make metal-loaded zeolites promising catalysts. Three different β zeolites were synthesized by an aqueous ion-exchange procedure, firstly with cobalt (Co), and secondly with zinc (Zn), cerium (Ce), and copper (Cu), to make three bimetallic CoZn/β, CoCe/β, and CoCu/β zeolites, respectively. X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and low-temperature nitrogen adsorption analysis revealed the structural, morphological, and surface properties of the studied materials, while optical properties were investigated by UV-Vis diffuse reflectance spectroscopy. The lowest onset potential of 1.67 V was obtained for both CoZn/β and CoCe/β, while the somewhat positive value of 1.70 V was observed for CoCu/β. CoZn/β exhibited the lowest value of Tafel slope of 89 mV dec−1, while slightly higher values of 109 and 113 mV dec−1 were calculated for CoCe/β and CoCu/β during ORR, respectively. CoZn/β showed four-electron pathways of ORR, CoCu/β showed a mixed ORR mechanism, while CoCe/β offered two-electron pathways of ORR. All presented results established that CoZn/β had the highest OER/ORR activity, followed by CoCu/β, while CoCe/β had the lowest activity detected. Full article
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24 pages, 1991 KB  
Article
Dietary Intakes and Exposures to Minerals and Trace Elements from Cereal-Based Mixtures: Potential Health Benefits and Risks for Adults
by Martina Mrázková, Daniela Sumczynski, Lenka Šenkárová and Richardos Nikolaos Salek
Nutrients 2025, 17(17), 2848; https://doi.org/10.3390/nu17172848 - 31 Aug 2025
Viewed by 1270
Abstract
Background: Foods containing nutraceuticals from the mineral element group are being developed to compensate for the problem of deficiency in billions of people around the world. This research focuses on essential elements of patented cereal-based mixtures to complement the deficiencies of these elements [...] Read more.
Background: Foods containing nutraceuticals from the mineral element group are being developed to compensate for the problem of deficiency in billions of people around the world. This research focuses on essential elements of patented cereal-based mixtures to complement the deficiencies of these elements and, at the same time, assesses their safety in terms of toxic elements in the human diet. Methods: The mineral and trace element contents in the mixtures were determined using the ICP-MS method with a subsequent evaluation of the contributions of the mixtures to the essential and toxic reference values based on dietary intakes and exposures for adults at 60, 80 and 100 kg of adult body weight and a portion size of 50 g. The potential health risk was evaluated using a metal pollution index. Results: The concentrations of minerals and trace elements in the cereal-based mixtures analyzed were as follows: K (up to 4150 µg/g) ≥ P > Mg > Ca > Na > Fe > Zn > Mn > Cu > Al > Ba (up to 4.40 µg/g) > Sr (up to 480 ng/g) ≥ Ti ≥ Ni > Ce ≥ Co > As ≥ Cs > Ag ≥ Li > Se > Be > Cr > Tl > Pb ≥ Hg > Ho > Cd > Sn (up to 1.12 ng/g). The mixtures contribute significantly to the reference values for Mn, Cu, Zn, Fe, and P for adults. Individual dietary exposure values of toxic elements for adults weighing 60 kg decrease in this order: Al (10.1 µg/kg bw/day) > Ni (362 ng/kg bw/day) > As ≥ Pb > Ag > Hg > Cd > and Sn (0.93 ng/kg bw/day). Conclusions: In terms of Regulation (EU) No 1924/2006 of the European Parliament and of the Council on nutrition and health claims made on foods, the cereal-based mixtures could be labelled “source of” Mn, Cu, Zn, Fe, and P when their contributions to the reference values exceeded 15%; in addition, “low sodium/salt” or “very low sodium/salt” can be applied. The mixtures contribute insignificantly to the toxic reference values of Al, Sn, Hg, Cd, Ni, and Ag, and the exposure values of Pb for developmental neurotoxicity, nephrotoxicity, and cardiovascular effects were considered safe. Regarding the metal pollution index of mixtures, there is no concern for potential health effects. Cereal-based mixtures are suitable for use in the food industry as a potential source of beneficial micronutrients for the human diet, although bioaccessible studies should not be neglected. Full article
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19 pages, 3882 KB  
Article
Olivine and Whole-Rock Geochemistry Constrain Petrogenesis and Geodynamics of Early Cretaceous Fangcheng Basalts, Eastern North China Craton
by Qiao-Chun Qin, Lu-Bing Hong, Yin-Hui Zhang, Hong-Xia Yu, Dan Wang, Le Zhang and Peng-Li He
Minerals 2025, 15(9), 928; https://doi.org/10.3390/min15090928 - 30 Aug 2025
Viewed by 590
Abstract
The profound Phanerozoic destruction of the eastern North China Craton (NCC) is well documented, yet its mechanism remains debated due to limited constraints on thermal state and lithospheric thickness during the Early Cretaceous—the peak period of cratonic destruction. We address this gap through [...] Read more.
The profound Phanerozoic destruction of the eastern North China Craton (NCC) is well documented, yet its mechanism remains debated due to limited constraints on thermal state and lithospheric thickness during the Early Cretaceous—the peak period of cratonic destruction. We address this gap through integrated geochemical analysis (major/trace elements, Sr-Nd-Pb isotopes, olivine chemistry) of Early Cretaceous (~125 Ma) Fangcheng basalts from Shandong. These basalts possess high MgO (8.14–11.31 wt%), Mg# (67.23–73.69), Ni (126–244 ppm), and Cr (342–526 ppm). Their trace elements show island arc basalt (IAB) affinities: enrichment in large-ion lithophile elements and depletion in high-field-strength elements, with negative Sr and Pb anomalies. Enriched Sr-Nd isotopic compositions [87Sr/86Sr(t) = 0.709426–0.709512; εNd(t) = −12.60 to −13.10], unradiogenic 206Pb/204Pb(t) and 208Pb/204Pb(t) ratios (17.55–17.62 and 37.77–37.83, respectively), and slightly radiogenic 207Pb/204Pb(t) ratios (15.55–15.57) reflect an upper continental crustal signature. Covariations of major elements, Cr, Ni, and trace element ratios (Sr/Nd, Sc/La) with MgO indicate dominant olivine + pyroxene fractionation. High Ce/Pb ratios and lack of correlation between Ce/Pb or εNd(t) and SiO2 preclude significant crustal contamination. The combined isotopic signature and IAB-like trace element patterns support a lithospheric mantle source that was metasomatized by upper crustal material. Olivine phenocrysts exhibit variable Ni (1564–4786 ppm), Mn (903–2406 ppm), Fe/Mn (56.63–85.49), 10,000 × Zn/Fe (9.55–19.55), and Mn/Zn (7.07–14.79), defining fields indicative of melts from both peridotite and pyroxenite sources. High-MgO samples (>10 wt%) in the Grossular/Pyrope/Diopside/Enstatite diagram show a clinopyroxene, garnet, and olivine residue. Reconstructed primary melts yield formation pressures of 3.5–3.9 GPa (110–130 km depth) and temperatures of 1474–1526 °C, corresponding to ~60 mW/m2 surface heat flow. This demonstrates retention of a ≥110–130 km thick lithosphere during peak destruction, arguing against delamination and supporting a thermo-mechanic erosion mechanism dominated by progressive convective thinning of the lithospheric base via asthenospheric flow. Our findings therefore provide crucial thermal and structural constraints essential for resolving the dynamics of cratonic lithosphere modification. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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17 pages, 5692 KB  
Article
Investigating the Influence of Cerium Doping on the Structural, Optical, and Electrical Properties of ZnCexCo2xO4 Zinc Cobaltite Thin Films
by Abdellatif El-Habib, Mohamed Oubakalla, Samir Haloui, Youssef Nejmi, Mohamed El Bouji, Amal Yousfi, Fouad El Mansouri, Abdessamad Aouni, Mustapha Diani and Mohammed Addou
Crystals 2025, 15(8), 742; https://doi.org/10.3390/cryst15080742 - 20 Aug 2025
Viewed by 795
Abstract
Cerium-doped zinc cobaltite spinel thin films, ZnCexCo2xO4 (0.00x0.05), were synthesized via spray pyrolysis, and their structural, morphological, optical, and electrical properties were analyzed. X-ray [...] Read more.
Cerium-doped zinc cobaltite spinel thin films, ZnCexCo2xO4 (0.00x0.05), were synthesized via spray pyrolysis, and their structural, morphological, optical, and electrical properties were analyzed. X-ray diffraction (XRD) confirmed a cubic spinel structure with a predominant (311) orientation across all compositions. Raman spectroscopy further verified this phase, revealing four active vibrational modes at 180 cm−1, 470 cm−1, 515 cm−1, and 682 cm−1. Scanning electron microscopy (SEM) indicated a uniform grain distribution, while energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of Ce, Zn, Co, and O. Optical measurements revealed two distinct bandgaps, decreasing from 2.32 eV to 2.20 eV for the lower-energy transition and from 3.38 eV to 3.18 eV for the higher-energy transition. Hall effect measurements confirmed p-type conductivity in all films. Electrical analysis showed a reduction in resistivity, from 280.3 Ω·cm to 15.4 Ω·cm, along with an increase in carrier concentration from 1.15 × 1016 cm−3 to 8.15 × 1017 cm−3 with higher Ce content. These results demonstrate that spray pyrolysis is a cost-effective and scalable method for producing Ce-doped ZnCo2O4 thin films with tunable properties, making them suitable for electronic and optoelectronic applications. Full article
(This article belongs to the Special Issue Advances in Thin-Film Materials and Their Applications)
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22 pages, 10413 KB  
Article
Metallogenic Mechanisms of the Lower Triassic Dongping Sedimentary Manganese Deposit in the South China Block: Mineralogical and Geochemical Evidence
by Rong-Zhi Li, Sha Jiang, Peng Long, Tao Long, Da-Qing Ding, Ling-Nan Zhao, Yi Zhang and Qin Huang
Minerals 2025, 15(8), 847; https://doi.org/10.3390/min15080847 - 8 Aug 2025
Viewed by 532
Abstract
The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical [...] Read more.
The Dongping manganese (Mn) deposit, located within the Lower Triassic Shipao Formation of the Youjiang Basin, is one of South China’s most significant sedimentary Mn carbonate ore deposits. To resolve longstanding debates over its metallogenic pathway, we conducted integrated sedimentological, mineralogical, and geochemical analyses on three drill cores (ZK5101, ZK0301, and ZK1205) spanning the Mn ore body. X-ray diffraction and backscatter electron imaging reveal that the ores are dominated by kutnohorite, with subordinate quartz, calcite, dolomite, and minor sulfides. The low enrichment of U/Al, V/Al, and Mo/Al, as well as positive Ce anomalies, consistently suggest that Mn, in the form of oxides, was deposited in an oxic water column. Carbon isotope compositions of Mn carbonate ores (δ13CVPDB: −2.3 to −6.1‰) and their negative correlation with MnO suggest that Mn carbonate, predominantly kutnohorite, show a diagenetic reduction in pre-existing Mn oxides via organic-matter oxidation in anoxic sediments pore waters. Elemental discrimination diagramms (Mn-Fe-(Co+Ni+Cu) × 10 and Co/Zn vs. Co+Cu+Ni) uniformly point to a hydrothermal Mn source. We therefore propose that hydrothermal fluids supplied dissolved Mn2+ to an oxic slope-basin setting, precipitating initially as Mn oxides, which were subsequently transformed to Mn carbonates during early diagenesis. This model reconciles both the hydrothermal and sedimentary-diagenetic processes of the Dongping Mn deposit. Full article
(This article belongs to the Section Mineral Deposits)
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28 pages, 4848 KB  
Article
Mineralogical and Geochemical Features of Soil Developed on Rhyolites in the Dry Tropical Area of Cameroon
by Aubin Nzeugang Nzeukou, Désiré Tsozué, Estelle Lionelle Tamto Mamdem, Merlin Gountié Dedzo and Nathalie Fagel
Standards 2025, 5(3), 20; https://doi.org/10.3390/standards5030020 - 6 Aug 2025
Viewed by 625
Abstract
Petrological knowledge on weathering processes controlling the mobility of chemical elements is still limited in the dry tropical zone of Cameroon. This study aims to investigate the mobility of major and trace elements during rhyolite weathering and soil formation in Mobono by understanding [...] Read more.
Petrological knowledge on weathering processes controlling the mobility of chemical elements is still limited in the dry tropical zone of Cameroon. This study aims to investigate the mobility of major and trace elements during rhyolite weathering and soil formation in Mobono by understanding the mineralogical and elemental vertical variation. The studied soil was classified as Cambisols containing mainly quartz, K-feldspar, plagioclase, smectite, kaolinite, illite, calcite, lepidocrocite, goethite, sepiolite, and interstratified clay minerals. pH values ranging between 6.11 and 8.77 indicated that hydrolysis, superimposed on oxidation and carbonation, is the main process responsible for the formation of secondary minerals, leading to the formation of iron oxides and calcite. The bedrock was mainly constituted of SiO2, Al2O3, Na2O, Fe2O3, Ba, Zr, Sr, Y, Ga, and Rb. Ce and Eu anomalies, and chondrite-normalized La/Yb ratios were 0.98, 0.67, and 2.86, respectively. SiO2, Al2O3, Fe2O3, Na2O, and K2O were major elements in soil horizons. Trace elements revealed high levels of Ba (385 to 1320 mg kg−1), Zr (158 to 429 mg kg−1), Zn (61 to 151 mg kg−1), Sr (62 to 243 mg kg−1), Y (55 to 81 mg kg−1), Rb (1102 to 58 mg kg−1), and Ga (17.70 to 35 mg kg−1). LREEs were more abundant than HREEs, with LREE/HREE ratio ranging between 2.60 and 6.24. Ce and Eu anomalies ranged from 1.08 to 1.21 and 0.58 to 1.24 respectively. The rhyolite-normalized La/Yb ratios varied between 0.56 and 0.96. Mass balance revealed the depletion of Si, Ca, Na, Mn, Sr, Ta, W, U, La, Ce, Pr, Nd, Sm, Gd and Lu, and the accumulation of Al, Fe, K, Mg, P, Sc, V, Co, Ni, Cu, Zn, Ga, Ge, Rb, Y, Zr, Nb, Cs, Ba, Hf, Pb, Th, Eu, Tb, Dy, Ho, Er, Tm and Yb during weathering along the soil profile. Full article
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16 pages, 4770 KB  
Article
Developing a CeS2/ZnS Quantum Dot Composite Nanomaterial as a High-Performance Cathode Material for Supercapacitor
by Shan-Diao Xu, Li-Cheng Wu, Muhammad Adil, Lin-Feng Sheng, Zi-Yue Zhao, Kui Xu and Xin Chen
Batteries 2025, 11(8), 289; https://doi.org/10.3390/batteries11080289 - 1 Aug 2025
Cited by 1 | Viewed by 819
Abstract
To develop high-performance electrode materials for supercapacitors, in this paper, a heterostructured composite material of cerium sulfide and zinc sulfide quantum dots (CeS2/ZnS QD) was successfully prepared by hydrothermal method. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission [...] Read more.
To develop high-performance electrode materials for supercapacitors, in this paper, a heterostructured composite material of cerium sulfide and zinc sulfide quantum dots (CeS2/ZnS QD) was successfully prepared by hydrothermal method. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) showed that ZnS QD nanoparticles were uniformly composited with CeS2, effectively increasing the active sites surface area and shortening the ion diffusion path. Electrochemical tests show that the specific capacitance of this composite material reaches 2054 F/g at a current density of 1 A/g (specific capacity of about 256 mAh/g), significantly outperforming the specific capacitance of pure CeS2 787 F/g at 1 A/g (specific capacity 98 mAh/g). The asymmetric supercapacitor (ASC) assembled with CeS2/ZnS QD and activated carbon (AC) retained 84% capacitance after 10,000 charge–discharge cycles. Benefited from the synergistic effect between CeS2 and ZnS QDs, the significantly improved electrochemical performance of the composite material suggests a promising strategy for designing rare-earth and QD-based advanced energy storage materials. Full article
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23 pages, 4059 KB  
Article
Effect of NiO and ZnO Sintering Aids on Sinterability and Electrochemical Performance of BCZY Electrolyte
by Saheli Biswas, Sareh Vafakhah, Gurpreet Kaur, Aaron Seeber and Sarbjit Giddey
Ceramics 2025, 8(2), 78; https://doi.org/10.3390/ceramics8020078 - 19 Jun 2025
Cited by 1 | Viewed by 1853
Abstract
Proton-conducting ceramics have gained significant attention in various applications. Yttrium-doped barium cerium zirconate (BaCexZr1−x−yYyO3–δ) is the state-of-the-art proton-conducting electrolyte but poses a major challenge because of its high sintering temperature. Sintering aids have been found [...] Read more.
Proton-conducting ceramics have gained significant attention in various applications. Yttrium-doped barium cerium zirconate (BaCexZr1−x−yYyO3–δ) is the state-of-the-art proton-conducting electrolyte but poses a major challenge because of its high sintering temperature. Sintering aids have been found to substantially reduce the sintering temperature of BaCexZr1−x−yYyO3–δ. This work evaluates, for the first time, the impact of NiO and ZnO addition in three different loadings (1, 3, 5 mol%), via wet mechanical mixing, on the sintering and electrical properties of a low cerium-containing composition, BaCe0.2Zr0.7Y0.1O3–δ (BCZY). The sintering temperature remarkably dropped from 1600 °C (for pure BCZY) to 1350 °C (for NiOBCZY and ZnOBCZY) while achieving > 95% densification. In general, ZnO gave higher densification than NiO, the highest being 99% for 5 mol% ZnOBCZY. Dilatometric studies revealed that ZnOBCZY attained complete shrinkage at temperatures lower than NiOBCZY. Up to 650 °C, ZnO showed higher conductivity compared to NiO for the same loading, mostly due to a higher extent of Zn incorporation inside the BCZY lattice as seen from the BCZY peak shift to a lower Bragg’s angle in X-ray diffractograms, and the bigger grain sizes of ZnO samples compared to NiO captured in scanning electron microscopy. At any temperature, the variation in conductivity as a function of sintering aid concentration followed the orders 1 mol% > 3 mol% > 5 mol% (for ZnO) and 1 mol% < 3 mol%~5 mol% (for NiO). This difference in conductivity trends has been attributed to the fact that Zn fully dissolves into the BCZY matrix, unlike NiO which mostly accumulates at the grain boundaries. At 600 °C, 1 mol% ZnOBCZY showed the highest conductivity of 5.02 mS/cm, which is, by far, higher than what has been reported in the literature for a Ce/Zr molar ratio <1. This makes ZnO a better sintering aid than NiO (in the range of 1 to 5 mol% addition) in terms of higher densification at a sintering temperature as low as 1350 °C, and higher conductivity. Full article
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23 pages, 7235 KB  
Article
Corrosion Resistance Behavior of Mg-Zn-Ce/MWCNT Magnesium Nanocomposites Synthesized by Ultrasonication-Assisted Hybrid Stir–Squeeze Casting for Sacrificial Anode Applications
by S. C. Amith, Poovazhagan Lakshmanan, Gnanavelbabu Annamalai, Manoj Gupta and Arunkumar Thirugnanasambandam
Metals 2025, 15(6), 673; https://doi.org/10.3390/met15060673 - 17 Jun 2025
Viewed by 666
Abstract
The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze [...] Read more.
The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze (UHSS) casting method with different MWCNT concentrations (0, 0.4, 0.8, 1.2 wt.%) in a Mg-Zn-Ce magnesium alloy matrix. The microstructural characterizations shown using X-ray diffraction revealed the presence of secondary phases (MgZn2, Mg12Ce), T-phase (Mg7Zn3RE), α-Mg, and MWCNT peaks. Optical microscopy results showed grain refinement in the case of nanocomposites. Transmission electron microscope studies revealed well-dispersed MWCNT, indicating the good selection of processing parameters. The uniform dispersion of MWCNTs was achieved due to a hybrid stirring mechanism along with transient cavitation, ultrasonic streaming, and squeeze effect. The higher Ecorr value of −1.39 V, lower Icorr value (5.81 µA/cm2), and lower corrosion rate of 0.1 mm/Yr (↑77%) were obtained by 0.8% nanocomposite at 0.4 M NaCl concentration, when compared to the monolithic alloy. The Mg(OH)2 passive film formation on 0.8 wt.% nanocomposite was denser, attributed to the refined grains. At higher NaCl concentration, the one-dimensional morphological advantage of MWCNT helped to act as a barrier for further Mg exposure to excessive Cl attack, which reduced the formation of MgCl2. Therefore, the UHSS-casted Mg-Zn-Ce/MWCNT nanocomposites present a good potential as sacrificial anodes for use in a wide range of industrial applications. Full article
(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Third Edition))
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