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Search Results (1,153)

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Keywords = Si/Al ratio

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13 pages, 3683 KB  
Article
Mineral Characteristics and Color-Causing Mechanisms of Beryl from Xinjiang, Northwest China: Insights from Multi-Spectroscopic Analyses and Chemical Compositions
by Yanan Bi, Cun Zhang, Bin Lin, Nan Ma and Weiliang Wang
Spectrosc. J. 2026, 4(2), 8; https://doi.org/10.3390/spectroscj4020008 (registering DOI) - 21 Apr 2026
Abstract
Beryllium (Be), a critical strategic metal element, is predominantly extracted from beryl, which serves as a key mineral combining significant strategic importance with essential industrial applications. Significant debate remains, however, regarding the mineralogical characteristics and color-causing mechanisms of beryl. In this study, we [...] Read more.
Beryllium (Be), a critical strategic metal element, is predominantly extracted from beryl, which serves as a key mineral combining significant strategic importance with essential industrial applications. Significant debate remains, however, regarding the mineralogical characteristics and color-causing mechanisms of beryl. In this study, we integrate Electron Probe Microanalysis (EPMA), Fourier transform infrared spectrometer (FTIR), laser Raman spectrometer (LRS), X-ray diffractometer (XRD), and ultraviolet–visible spectrophotometer (UV-VIS) to elucidate the mineralogy and spectral characteristics of pegmatitic beryl from Xinjiang, Northwest China. The results indicate that the beryl mainly presents a yellowish-green color, associated with minerals such as feldspar, quartz, and garnet. The EPMA results confirm the chemical composition of the typical beryl and indicate that the Al content is lower than the theoretical value, reflecting the substitution of Al3+. The FTIR shows characteristic vibrations of Si-O tetrahedral groups within the range of 1400~400 cm−1, along with distinct bending and stretching vibration peaks of H2O molecules observed in the range of 1700~1500 cm−1 and 3500~3800 cm−1, respectively. Combined with spectral analysis, it can be determined that both Type I water and Type II H2O are present in the samples. Raman spectroscopy reveals that the two distinct peaks of beryl are located at approximately 685 cm−1 (attributed to the stretching vibration of Be-O) and 1067 cm−1 (corresponding to the bending vibration of Si-O), respectively. The XRD analysis shows that the ratio of unit cell parameters c/a of the samples ranges from 0.9950 to 1.0068, and the isomorphous substitution in its structure is mainly manifested as the replacement of octahedral coordination sites by Al3+. The UV-VIS shows that Fe3+ exhibits a broad absorption band in the range of 200~300 nm, while no obvious absorption peaks are observed in the range of 300~800 nm. The above characteristics indicate that Fe3+ has a significant impact on the color of beryl. For green beryl samples, a portion of Fe3+ occupies the structural channel sites and interacts with H2O molecules within the channels, which contributes to the yellowish hue of beryl. Our study highlights crucial data for mineralogical identification, genetic tracing, as well as efficient utilization of beryl resources. Full article
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18 pages, 2791 KB  
Article
Phase Formation Features in the Metallothermal Reduction of Natural Coltan
by Kirill V. Pikulin, Stanislav N. Tyushnyakov, Roza I. Gulyaeva, Sofya A. Petrova, Andrey N. Dmitriev and Galina Yu. Vitkina
Metals 2026, 16(4), 436; https://doi.org/10.3390/met16040436 - 17 Apr 2026
Viewed by 170
Abstract
Phase formation characteristics during the thermochemical reduction of metals from natural coltan using aluminum and calcium–aluminum alloy at 1400–1450 °C were investigated to develop methods for extracting niobium and tantalum from rare metal raw materials. The studied coltan sample consists of a columbite–tantalite [...] Read more.
Phase formation characteristics during the thermochemical reduction of metals from natural coltan using aluminum and calcium–aluminum alloy at 1400–1450 °C were investigated to develop methods for extracting niobium and tantalum from rare metal raw materials. The studied coltan sample consists of a columbite–tantalite solid solution with the composition (Mn,Fe)(Nb,Ta)2O6, cassiterite Sn0.9O2, tapiolite (Ta,Nb)2(Mn,Fe)O6, and calcioolivine Ca2SiO4. This study established that the choice of reducing agent determines the sequence of oxide phase transformations. During the aluminothermic process, orthorhombic columbite–tantalite is completely reduced, while tetragonal tapiolite persists even at 1400 °C. The use of a calcium–aluminum alloy containing 69.4 wt.% Ca results in a reversal of this trend: tapiolite is reduced at the early stages (800–1250 °C) through an intermediate (Ta,Nb)O2 phase, whereas the columbite–tantalite solid solution remains up to 1250 °C. Calcium, having a high affinity for oxygen, forms intermediate perovskite-type oxide phases that act as diffusion barriers, limiting the access of the reducing agent to residual mineral inclusions (mainly Nb-Ta minerals of the orthorhombic crystal system). A temperature rise to 1450 °C initiates the redistribution of oxide components: the content of CaNbO3 decreases, the Ca2(Nb,Ta)AlO6 phase disappears, and its components are involved in the formation of Ca(Nb,Ta)0.25MnO2.74 and Ca4Nb2O9. Diffusion constraints are reduced, and the residual columbite–tantalite solid solution is reduced, as confirmed by its complete absence in the products at 1450 °C. In the metallic phase, solid solutions of tantalum and niobium, Ta-Nb-Sn intermetallic compounds (Ta,Nb)3Sn, titanium aluminide, and ferroalloys with an increased (Ta,Nb)/(Fe,Mn) ratio are formed. The phase transformations elucidated during metallothermic reduction of coltan using different reducing agents, together with the formation of metallic and intermetallic phases, establish a scientific foundation for the development of advanced rare metal extraction processes. Full article
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19 pages, 6056 KB  
Article
A Novel Pressure-Assisted Induction Melting Technique for Synthesis of Lightweight High-Entropy Alloys: A Concept, Process Development and Hardware Design
by Peter Newcombe and Frank Czerwinski
Materials 2026, 19(8), 1588; https://doi.org/10.3390/ma19081588 - 15 Apr 2026
Viewed by 274
Abstract
Lightweight high-entropy alloys are primarily designed to overcome the strength-to-density ratio limitations of conventional counterparts and often consist of elements with drastically different melting temperature and vapor pressure. Their chemistry, therefore, imposes challenges on alloy synthesis, particularly through liquid metal engineering routes, since [...] Read more.
Lightweight high-entropy alloys are primarily designed to overcome the strength-to-density ratio limitations of conventional counterparts and often consist of elements with drastically different melting temperature and vapor pressure. Their chemistry, therefore, imposes challenges on alloy synthesis, particularly through liquid metal engineering routes, since elements with high vapor pressure (e.g., Mg, Zn, Li) vaporize before the higher-melting-point ingredients (e.g., Cu, V, Ni) are fully molten, resulting in volatile element loss. To overcome this challenge, a novel pressure-assisted induction melting (PAIM) process was developed and the proprietary furnace for its implementation was designed and built. The system allows precision melting of up to 10 cm3 of an alloy at temperatures up to 1700 °C while addressing the partial pressure requirements during the melting progress. The chamber is prepared using rough vacuum and re-filled with inert gas such as argon with the operating pressure range from about 10−4 MPa up to maximum of 1.6 MPa (233 psi). The alloy chemical composition can be modified in situ by feeding solid additives at specific melting stages through the isolated airlock without disrupting the pressure conditions within the chamber. The viability of the concept was verified by synthesis of two lightweight non-equimolar high-entropy alloys: Mg-rich Mg50(MnAlZnCu)50 and Al-rich Al35Mg30Si13Zn10Y7Ca5. The experiments showed that sequential multi-step melting procedures, designed based on inputs from FactSage computational analysis, when combined with PAIM synthesis, allowed manufacturing fully dense and chemically homogenous complex alloy compositions with optimal volumes for materials discovery research. Full article
(This article belongs to the Section Metals and Alloys)
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23 pages, 4582 KB  
Article
A Hybrid Clustering–Classification Approach for Predicting Strength and Analyzing Material Composition of Geopolymers
by Yıldıran Yılmaz, Talip Çakmak and İlker Ustabaş
Polymers 2026, 18(8), 959; https://doi.org/10.3390/polym18080959 - 14 Apr 2026
Viewed by 404
Abstract
The development of geopolymers as sustainable alternative binders has been accelerated by the environmental requirement to reduce the carbon footprint of cement. However, predicting their key properties, such as compressive strength, from their complex chemical composition remains a significant challenge. Although mixture ratios [...] Read more.
The development of geopolymers as sustainable alternative binders has been accelerated by the environmental requirement to reduce the carbon footprint of cement. However, predicting their key properties, such as compressive strength, from their complex chemical composition remains a significant challenge. Although mixture ratios prepared on a macro-scale are widely used for quality control purposes, they do not account for the chemical structure, despite this having a direct impact on the materials’ structural properties. Predicting fundamental properties such as compressive strength from complex chemical compositions remains a significant challenge due to the nonlinear relationships between the elemental components. This research paper introduces a tailored hybrid machine learning framework that combines K-means clustering with classification algorithms. The method uses energy-dispersive X-ray spectroscopy (EDS) data to classify geopolymer samples into their specific mixture numbers, which allows scientists to predict material properties through compositional analysis. A new dataset featuring the elemental compositions of Si, Al, Na, Ca, O, and C, as well as the critical ratios of Si/Al and Ca/Si, was analyzed. The initial step involved clustering the data to discover natural compositional clusters, which served as the basis for training and testing five different classifiers, which included Random Forest (RF), Artificial Neural Networks (ANN), LightGBM, Naive Bayes (NB), and Linear Discriminant Analysis (LDA). The consequences proved that the hybrid method worked with outstanding efficiency. RF achieved the highest performance results through its 98% accuracy, 96% recall, 94% precision, and 95% F1-score results when it classified samples according to their clustered groups. SHAP (SHapley Additive exPlanations) and permutation feature importance analyses both showed that Si/Al proportion functioned as the most crucial predictive variable, while oxygen (O) content and silicon (Si) content followed in importance. The K-means cluster labels produced high accuracy results because they demonstrated that compositional data had strong natural groups, which matched the target property. The system delivers an efficient method which enables fast and dependable geopolymer property forecasts through direct analysis of chemical composition with chemical composition analysis, thus delivering essential information to enhance mix design processes and boost sustainable building material production. Full article
(This article belongs to the Section Polymer Physics and Theory)
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37 pages, 10729 KB  
Article
Surface Microstructural Characteristics of Textured Multicomponent TiN-Based Coated Cemented Carbides
by Xin Tong, Xiaolong Cao, Shucai Yang and Dongqi Yu
Coatings 2026, 16(4), 470; https://doi.org/10.3390/coatings16040470 - 14 Apr 2026
Viewed by 212
Abstract
To address the issues of high cutting temperatures and severe tool wear during titanium alloy machining, this study proposes a hybrid surface modification strategy combining micro-textures and multicomponent titanium nitride (TiN)-based coatings on cemented carbide tools. Using YG8 cemented carbide as the substrate, [...] Read more.
To address the issues of high cutting temperatures and severe tool wear during titanium alloy machining, this study proposes a hybrid surface modification strategy combining micro-textures and multicomponent titanium nitride (TiN)-based coatings on cemented carbide tools. Using YG8 cemented carbide as the substrate, micro-dimple textures were fabricated by fiber laser, and three coatings with different architectures (TiAlSiN, TiSiN/TiAlN, and TiSiN/TiAlSiN/TiAlN) were deposited via multi-arc ion plating technology. Based on a two-factor (texture diameter and texture spacing) and three-level orthogonal experiment, the evolution behaviors of surface morphology, phase composition, and mechanical properties of the textured multicomponent TiN-based coatings were systematically characterized and comparatively analyzed. The results reveal that: compared to the monolithic-structured TiAlSiN coating, the TiSiN/TiAlSiN/TiAlN and TiSiN/TiAlN composite coatings with multilayered composite structures can effectively relieve the residual stress inside the film–substrate system, and significantly suppress the phenomena of coating cracking and localized spallation caused by irregular protrusions of the recast layer at the micro-texture edges. X-ray diffraction (XRD) and crystallite size analyses indicate that the amorphous Si3N4 phase promoted by the Si element in the composite coatings effectively impedes the growth of TiN columnar crystals, achieving significant grain refinement. Mechanical property tests confirm that the existence of multicomponent composite interfaces effectively hinders dislocation movement. Among them, the textured TiSiN/TiAlSiN/TiAlN composite coating exhibits the optimal comprehensive performance; its microhardness, nanohardness, and H/E ratio (characterizing the resistance to plastic deformation) are increased by 17.94%, 8%, and approximately 45%, respectively, compared to those of the textured TiAlSiN coating. This study deeply elucidates the synergistic strengthening and toughening mechanisms between micro-texture parameters and the internal structures of the coatings, providing important theoretical guidance and experimental data support for the surface design of long-lifespan tools oriented towards the high-efficiency machining of titanium alloys. Full article
(This article belongs to the Special Issue Cutting Performance of Coated Tools)
18 pages, 5533 KB  
Article
Crystallization Behavior of CaO-SiO2-Al2O3-MgO-TiO2-FeO Slag with Different CaO/SiO2 Ratios
by Wu Zhu, Qianqian Ren, Shuang Cai, Junguo Li, Lanjie Li, Luyang Duan, Yanan Zeng, Yajun Wang and Bao Liu
Materials 2026, 19(8), 1574; https://doi.org/10.3390/ma19081574 - 14 Apr 2026
Viewed by 313
Abstract
Titanium-extracted tailing is a by-product generated during titanium-bearing blast furnace slag treatment process. The crystallization behavior of the titanium-extracted tailing during the cooling process is significant to its utilization for glass ceramics preparation. In this work, the CaO-SiO2-Al2O3 [...] Read more.
Titanium-extracted tailing is a by-product generated during titanium-bearing blast furnace slag treatment process. The crystallization behavior of the titanium-extracted tailing during the cooling process is significant to its utilization for glass ceramics preparation. In this work, the CaO-SiO2-Al2O3-MgO-TiO2-FeO slag was used to explore the effect of CaO/SiO2 ratios on titanium-extracted tailing crystallization. FactSage 8.2 calculation and mineralogical characterizations were conducted to investigate the phase and microstructure evolution during the slag cooling process. Single hot thermocouple technique (SHTT) was employed for in situ observation of the crystallization process of the slag during the cooling process. The obtained results indicated that the perovskite, melilite, spinel, diopside and anorthite phases would be crystallized during the cooling process when the CaO/SiO2 ratios of the slag were 0.7–1.1. Increasing the CaO/SiO2 ratio to 1.3 and 1.5 promoted the crystallization of olivine and merwinite phases, however, inhibited the crystallization of diopside and anorthite phases. The initial crystallization temperature and the liquid phase disappeared temperature of the slag enhanced with improving CaO/SiO2 ratios. The initial crystallization temperature was controlled by perovskite phase precipitation when the CaO/SiO2 ratios of slag reached 0.7–1.3. Whereas the initial crystallization temperature was controlled by the crystallization of spinel phase when the CaO/SiO2 ratio of slag was 1.5. The incubation time for crystal nucleation reduced with increasing CaO/SiO2 ratios that promoted slag crystallization. Moreover, increasing the CaO/SiO2 ratio from 0.7 to 1.5 enhanced the critical cooling rate from 4 °C s−1 to 11 °C s−1. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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20 pages, 8787 KB  
Article
All-Solid-Waste-Derived High-Temperature Ceramic Glazes Enable Mechanism-Informed Sustainable Color and Texture Design via Phase–Microstructure Tuning
by Yixuan Du, Lanlan Cheng, Yumeng Huang, Minxuan Chen and Haoran Li
Coatings 2026, 16(4), 466; https://doi.org/10.3390/coatings16040466 - 13 Apr 2026
Viewed by 357
Abstract
Glazes primarily utilize raw minerals like kaolinite. However, considering sustainable development, employing industrial solid waste offers greener design solutions and high economic efficiency. This study employs multiple analytical methods, including XRF, XRD, and SEM, to investigate the feasibility of replacing traditional glaze materials [...] Read more.
Glazes primarily utilize raw minerals like kaolinite. However, considering sustainable development, employing industrial solid waste offers greener design solutions and high economic efficiency. This study employs multiple analytical methods, including XRF, XRD, and SEM, to investigate the feasibility of replacing traditional glaze materials entirely with solid waste. It elucidates the mechanisms underlying changes in texture and color resulting from alterations in microstructure and chemical composition. Research on five different ratios of ceramic glaze composed of fly ash, blast furnace slag, silica fume, coal gangue, and desulfurization gypsum reveals that the implementation of solid waste-based glazes is feasible. The glazes formed a SiO2–Al2O3–CaO system surface, all exhibiting anorthite and diopside as the primary crystalline forms. The results are as follows: 1. The content of Ca and Mg depends on the overall proportion of elements, with a Ca threshold of approximately 28%. Below this threshold, characteristics such as surface roughness and porosity are observed. Above this threshold, as seen in G3 and G4, crystal distribution becomes more dense. 2. Si is the key factor controlling crystal variation. Sample G5 exhibits good crystal continuity. Visually, its color appears distinctly deep red. 3. Samples G1 and G2 both contain approximately 4.8 wt% Fe2O3, but G2 exhibits more crystalline precipitation. Visually, G2 appears more reddish-yellow than G1. Higher crystallinity yields superior coloration. Full article
(This article belongs to the Section Ceramic Coatings and Engineering Technology)
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23 pages, 51149 KB  
Article
Age-Dependent Effects of Graphene Oxide on Hydration-Gel Evolution and Strength Development of Fly Ash-Blended Cementitious Materials
by Hai-Sheng Huang, Ying Peng, Xiu-Cheng Zhang and Xue-Fei Chen
Gels 2026, 12(4), 312; https://doi.org/10.3390/gels12040312 - 6 Apr 2026
Viewed by 286
Abstract
Fly ash is an effective supplementary cementitious material for reducing clinker consumption and carbon emissions, but its low early reactivity often results in delayed hydration and insufficient early-age strength. This study investigated the age-dependent role of graphene oxide (GO) in fly ash-blended cementitious [...] Read more.
Fly ash is an effective supplementary cementitious material for reducing clinker consumption and carbon emissions, but its low early reactivity often results in delayed hydration and insufficient early-age strength. This study investigated the age-dependent role of graphene oxide (GO) in fly ash-blended cementitious materials by combining compressive strength testing with X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), 29Si magic-angle spinning nuclear magnetic resonance (29Si MAS NMR), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). Fly ash replacement levels of 10%, 20%, and 30% were considered, and 0.07% GO was introduced to evaluate its effect at 3, 7, and 28 days. The results showed that fly ash reduced the 3-day compressive strength, whereas the strength differences became much smaller at 28 days. GO enhanced the compressive strength of all fly ash-blended mixtures. XRD and TG-DTG results showed that GO refined Ca(OH)2 crystallization and reduced the retained CH content, indicating more effective CH utilization during hydration and pozzolanic reaction. At 28 days, the incorporation of 0.07% GO increased the compressive strength of the 30% fly ash mixture from 47.38 MPa to 56.58 MPa, while reducing the total CH content from 14.20% to 12.89%, indicating enhanced CH utilization and gel development. 29Si MAS NMR further demonstrated that GO promoted a more mature and polymerized silicate gel structure, as evidenced by lower Q0 fractions, higher mean chain length, and higher proportions of more polymerized silicate species. SEM-EDS observations confirmed that GO led to a denser matrix, less dominant coarse CH, and lower Ca/Si and Ca/(Si + Al) ratios. Overall, GO improved the mechanical performance of fly ash-blended cementitious materials through coupled regulation of hydration products, silicate gel polymerization, and matrix densification. Full article
(This article belongs to the Section Gel Chemistry and Physics)
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49 pages, 7199 KB  
Article
Machine Learning-Enhanced Modeling of Heavy Metal Adsorption onto Coal Fly Ash-Derived Zeolite P
by Benito A. Hernández-Guerrero, Lorena Martínez, Gabriel Peña-Rodríguez and Fernando Trejo
Water 2026, 18(7), 857; https://doi.org/10.3390/w18070857 - 2 Apr 2026
Viewed by 504
Abstract
Zeolite P was synthesized by hydrothermal treatment of coal fly ash and applied to the individual removal of six heavy metals (Pb2+, Ni2+, Cu2+, Cr3+, Hg2+, Cd2+) from aqueous solutions. Characterization [...] Read more.
Zeolite P was synthesized by hydrothermal treatment of coal fly ash and applied to the individual removal of six heavy metals (Pb2+, Ni2+, Cu2+, Cr3+, Hg2+, Cd2+) from aqueous solutions. Characterization by SEM-EDS, FTIR, BET, XRD, zeta potential, and XPS revealed a BET surface area of 30 m2/g, Si/Al ratio of 1.63, and pHpzc of 3.2. Batch experiments at the natural solution pH of 3.9 in all cases (C0 = 10, 100, 200 mg/L; t = 1–60 min) yielded an apparent selectivity sequence at C0 = 200 mg/L of Hg2+ (10.47 mg/g) > Pb2+ (9.12) > Ni2+ (2.18) > Cr3+ (2.05) > Cu2+ (1.82) > Cd2+ (1.26), where Hg2+ and Pb2+ reached near-equilibrium while the remaining metals were still approaching it at t = 60 min. Weber–Morris and Boyd analyses confirmed three sequential diffusion stages with a concentration-dependent shift from film to intraparticle diffusion control through the narrow GIS channels (3.1 × 4.5 Å). Ion exchange was identified as the dominant mechanism based on convergent kinetic, diffusion, XPS, and selectivity–electronegativity evidence (r = +0.76). A leakage-free machine learning framework combining physicochemical descriptors with experimental variables was tested under three cross-validation strategies of increasing stringency. Gradient Boosting achieved R2 = 0.979 ± 0.043 (repeated K-Fold) and R2 = 0.880 on six completely held-out kinetic curves. An ablation study confirmed that physicochemical descriptors are essential (experimental-only models yielded negative R2). SHAP feature importance rankings were consistent with established ion exchange selectivity theory. This work demonstrates that group-level validation, physics-informed descriptors, and systematic ablation testing are able to identify both the capabilities and the boundaries of small-dataset ML when testing for metal kinetics prediction. Full article
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12 pages, 2880 KB  
Proceeding Paper
Multiaxial Static and Fatigue Strength of LPBF-Manufactured AlSi10Mg in as-Built and T6 Conditions
by Francesco Lombardi, Alessandro Pirondi, Francesco Musiari and Federico Uriati
Eng. Proc. 2026, 131(1), 24; https://doi.org/10.3390/engproc2026131024 - 31 Mar 2026
Viewed by 213
Abstract
Laser powder bed fusion (LPBF) technology has now reached a significant level of commercial maturity, offering some of the most reliable solutions in the additive manufacturing (AM) field. However, AM processes may introduce defects that result in high variability of mechanical properties and [...] Read more.
Laser powder bed fusion (LPBF) technology has now reached a significant level of commercial maturity, offering some of the most reliable solutions in the additive manufacturing (AM) field. However, AM processes may introduce defects that result in high variability of mechanical properties and low reproducibility. This entails the need to thoroughly understand the behavior of the materials used, studying their response to the different types of stresses typical of real-world applications. The research activity presented consists of the analysis of the mechanical properties of the aluminum alloy AlSi10Mg, which is widely used due to its good strength-to-density ratio. Focus is put on the response to axial, torsional, and combined axial-torsional static and fatigue strength, comparing as-built T6 heat-treated conditions. Full article
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35 pages, 2568 KB  
Review
Waste Glass Powder as a Circular-Economy Precursor in Geopolymer Binders
by Sri Ganesh Kumar Mohan Kumar, John M. Kinuthia, Jonathan Oti and Blessing O. Adeleke
Materials 2026, 19(7), 1357; https://doi.org/10.3390/ma19071357 - 29 Mar 2026
Viewed by 479
Abstract
The transition toward low-carbon and resource-efficient construction materials has intensified interest in geopolymer binders incorporating industrial and post-consumer wastes. Waste glass powder (WGP), a silica-rich component of the global glass waste stream, has emerged as a promising circular-economy precursor in alkali-activated systems; however, [...] Read more.
The transition toward low-carbon and resource-efficient construction materials has intensified interest in geopolymer binders incorporating industrial and post-consumer wastes. Waste glass powder (WGP), a silica-rich component of the global glass waste stream, has emerged as a promising circular-economy precursor in alkali-activated systems; however, reported durability trends remain inconsistent and are often interpreted without mechanistic integration. This review synthesises current knowledge of WGP reactivity, gel chemistry, and long-term performance through an explicit reaction–transport–ageing (R–T–A) framework that links dissolution behaviour and phase assemblage development to pore connectivity, ion ingress, and time-dependent degradation. Under alkaline activation, the amorphous structure of WGP promotes silica release, modifying Si/Al ratios and governing the formation of N-A-S-H or hybrid N-A-S-H/C-(A)-S-H gels. These reaction products determine transport characteristics and ageing evolution, which collectively control chemical resistance, chloride ingress, alkali–silica reaction-type instability, and dimensional stability. Variability across studies is shown to arise from imbalances in particle fineness, replacement level, precursor chemistry, and activator design rather than intrinsic inconsistency in WGP behaviour. The R–T–A framework clarifies how reaction completeness, pore network architecture, and long-term phase stability interact to produce system-dependent durability outcomes. WGP demonstrates strong potential as a circular-economy precursor in alkali-activated binders; however, reliable structural application requires durability-informed mix design grounded in coupled reaction–transport–ageing mechanisms and supported by extended exposure testing under realistic service conditions. Full article
(This article belongs to the Special Issue Advanced Sustainable Cement-Based Materials)
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32 pages, 9247 KB  
Article
Deciphering Middle–Late Eocene Paleoenvironmental Conditions Using Geochemical Trends: Insights from the Beni Suef Area, Northeastern Desert, Egypt
by Mostafa M. Sayed, Michael Wagreich, Petra Heinz, Ibrahim M. Abd El-Gaied, Susanne Gier, Erik Wolfgring, Ramadan M. El-Kahawy, Ahmed Ali, Ammar Mannaa, Rabea A. Haredy and Dina M. Sayed
Minerals 2026, 16(4), 361; https://doi.org/10.3390/min16040361 - 29 Mar 2026
Viewed by 519
Abstract
The reconstruction of detrital flux, paleoclimate, paleosalinity, paleo-primary productivity, paleohydrodynamic conditions, and paleo-water depth enhances understanding of sedimentary processes and their drivers during deep-time greenhouse-icehouse transitions, such as the Eocene–Oligocene transition. This study uses detailed geochemical analyses of major oxides and trace elements [...] Read more.
The reconstruction of detrital flux, paleoclimate, paleosalinity, paleo-primary productivity, paleohydrodynamic conditions, and paleo-water depth enhances understanding of sedimentary processes and their drivers during deep-time greenhouse-icehouse transitions, such as the Eocene–Oligocene transition. This study uses detailed geochemical analyses of major oxides and trace elements in sediment samples collected from the Beni Suef Formation (Bartonian–Priabonian) and the Maadi Formation (Priabonian) in the southern Tethys shelf (Egypt, northeastern Desert). Detrital proxies, including Si/Al, Ti/Al, and Zr/Al, indicate an enhanced influx of terrigenous sediments in the middle portion of the Qurn Member of the Beni Suef Formation, as further supported by noticeable facies variations, particularly the transition from shale to coarser silt- and sand-sized fractions. Paleoclimate indicators (Sr/Ba, Rb/Sr, K2O/Al2O3, and Sr/Cu) point to a climatic shift from humid to arid conditions, consistent with the regional Late Eocene aridification across the Tethyan realm. Paleosalinity proxies (Sr/Ba, Ca/Al, and Mg/Al×100) suggest episodic intensification of open-marine influence and a reduction in freshwater input, with an upsection increase in Sr/Ba ratios, reflecting phases of enhanced marine water settings or decreased terrestrial runoff. Primary productivity was evaluated using multiple geochemical proxies, including P, Ni/Al, Cu/Al, P/Al, P/Ti, and Babio ratios. These collectively indicate generally low primary productivity interrupted by intervals of enhanced paleoproductivity or increased organic matter export to the sediments. This interpretation is further supported by the low total organic carbon (TOC) values. These results highlight the sensitivity of the southern Tethys shelf to Middle–Late Eocene climatic variability and the key role of prevailing paleoenvironmental conditions in controlling sediment supply, water chemistry, and biological productivity. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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21 pages, 12142 KB  
Article
Systematic Mineralogical and Geochemical Analyses of Magnetite in the Xinqiao Cu-S Polymetallic Deposit, Eastern China
by Lei Shi, Yinan Liu, Xiao Xin and Yu Fan
Minerals 2026, 16(4), 354; https://doi.org/10.3390/min16040354 - 27 Mar 2026
Viewed by 286
Abstract
The Xinqiao Cu-S polymetallic deposit is located in the Tongling ore concentration area of the Middle-Lower Yangtze River metallogenic belt. The orebodies consist of skarn orebodies and stratiform sulfide orebodies, but the genetic link between them remains controversial. In this study, magnetite was [...] Read more.
The Xinqiao Cu-S polymetallic deposit is located in the Tongling ore concentration area of the Middle-Lower Yangtze River metallogenic belt. The orebodies consist of skarn orebodies and stratiform sulfide orebodies, but the genetic link between them remains controversial. In this study, magnetite was used as a proxy to systematically constrain the hydrothermal evolution from the intrusion to the contact zone and further to the stratiform orebodies. A representative drill hole (E603) was logged, and samples were systematically collected from the Jitou pluton outward to the contact zone. Composite samples from the 8–28 m interval were crushed and prepared as resin mounts for integrated TIMA automated mineralogy, BSE textural observation, and in situ LA-ICP-MS trace element analysis. Five types of magnetite (Mt1 to Mt5) were systematically identified. Mt1 occurs as inclusions within feldspar in the quartz monzodiorite. It exhibits typical magmatic magnetite characteristics and contains grid-like ilmenite exsolution, indicating crystallization during the late magmatic stage. Mt2 is distributed in the interstices of magmatic minerals, commonly showing hematitization and replacement of ilmenite exsolution lamellae by titanite. Its trace element geochemistry displays magmatic–hydrothermal transitional features. Mt3–Mt5 in the skarn and stratiform orebodies are paragenetic with retrograde alteration minerals (e.g., epidote, chlorite, and actinolite) and sulfides, and are characterized by low Ti, Al, and V contents and high Mg, Mn, and Sn contents, indicating a hydrothermal origin. From Mt3 to Mt5, (Ti + V) and (Al + Mn) decrease, while Zn and Mn increase, accompanied by a decrease in the (Si + Al)/(Mg + Mn) ratio. This reflects a trend of decreasing fluid temperature and progressively enhanced wall-rock buffering. The Mg-in-magnetite geothermometer yields relatively consistent results for Mt1–Mt3, but anomalously high temperatures for Mt4–Mt5. This suggests that the elevated Mg activity in the fluid, caused by reaction with carbonate wall rocks, can significantly influence the calculated temperatures. Therefore, this geothermometer should be used cautiously for magnetite in the outer skarn zone and interpreted in combination with other temperature constraints. The textures, paragenetic mineral assemblages, and trace element characteristics of magnetite collectively reveal a continuous mineralization process linking the skarn and stratiform orebodies at Xinqiao, providing robust mineralogical and geochemical evidence for the contribution of Yanshanian magmatic–hydrothermal activity to the stratiform mineralization. Full article
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28 pages, 4396 KB  
Article
Optimization of Low-Heat Cementitious Materials Based on Construction Spoil Using Response Surface Methodology
by Xiangsai Guo, Qiang Zeng, Desheng Jin, Hao Wu, Chao Wang and Zhiwei Song
Buildings 2026, 16(6), 1253; https://doi.org/10.3390/buildings16061253 - 22 Mar 2026
Cited by 1 | Viewed by 253 | Correction
Abstract
To address the problem of temperature cracking caused by the concentrated release of hydration heat in mass concrete, this study developed a low-heat composite cementitious material (CWCM) by partially replacing conventional mineral admixtures with construction spoil. A multi-factor synergistic optimization design based on [...] Read more.
To address the problem of temperature cracking caused by the concentrated release of hydration heat in mass concrete, this study developed a low-heat composite cementitious material (CWCM) by partially replacing conventional mineral admixtures with construction spoil. A multi-factor synergistic optimization design based on response surface methodology (RSM) was conducted. The water–binder ratio, spoil replacement ratio, curing temperature, and ball-milling time were selected as influencing factors, while the 28-day flexural strength, 28-day compressive strength, and 72 h cumulative hydration heat were used as response variables. A four-factor, three-level Box–Behnken model was established. The results show that the regression model exhibits good fitting performance, and the prediction errors between the predicted and experimental values of all response variables are within a reasonable range. Under the optimized mixture proportion (15% spoil replacement), the system achieves a 28-day compressive strength of 61.03 MPa, while the 72 h cumulative hydration heat is reduced by approximately 15%, meeting the requirements for low-heat cement. Microstructural analyses using XRD, SEM, and TG/DTG indicate that a decrease in the Ca/Si ratio and an increase in the Al/Si ratio promote the formation of a denser C-(A)-S-H gel structure, enhancing the pozzolanic reaction. This mechanism plays a key role in achieving the synergistic regulation of strength enhancement and hydration heat reduction. Compared with conventional fly ash or slag systems, this study innovatively utilizes construction spoil as a partial substitute for traditional mineral admixtures. While maintaining satisfactory mechanical performance, the proposed system effectively reduces hydration heat release, providing a new pathway for temperature control design in mass concrete engineering and high-value resource utilization of construction waste. Full article
(This article belongs to the Special Issue A Circular Economy Paradigm for Construction Waste Management)
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20 pages, 4485 KB  
Article
Geochronology, Genesis and Redox Condition of the Lisong Granites in the Guposhan Region, Nanling Range: Constraints from Zircon U-Pb Dating, Whole-Rock Geochemistry, and Apatite Geochemistry
by Weijian Zhou, Mengqing Tang, Wenjing She, Yongxin Zhou, Liu Yang, Gaofeng Du, Na Liu, Jinyu Zhang and Jingya Cao
Minerals 2026, 16(3), 313; https://doi.org/10.3390/min16030313 - 17 Mar 2026
Viewed by 325
Abstract
The Guposhan ore field, located in the Nanling metallogenic belt, is well known for large-scale Sn-W mineralization genetically linked to the Late Jurassic Guposhan pluton. The Lisong pluton, a product of regional magmatism, occurs in the central part of the Guposhan ore field. [...] Read more.
The Guposhan ore field, located in the Nanling metallogenic belt, is well known for large-scale Sn-W mineralization genetically linked to the Late Jurassic Guposhan pluton. The Lisong pluton, a product of regional magmatism, occurs in the central part of the Guposhan ore field. However, the critical factors responsible for the absence of intensive Sn polymetallic mineralization in the Lisong pluton remain poorly understood. Our geochronological results show that the coarse-grained hornblende-bearing and hornblende-free biotite monzogranites of the Lisong pluton were emplaced at 162.9 ± 1.5 Ma and 162.2 ± 2.3 Ma, respectively, which are contemporaneous with the Guposhan pluton. Geochemically, these intrusions are characterized by high SiO2, Al2O3, and total alkalis (K2O + Na2O), high Ga/Al ratios (3.09–3.69), and peraluminous compositions (A/CNK = 1.15–1.23), consistent with high K calc-alkaline A-type granites. Similar to the adjacent Guposhan pluton, the Lisong granites yield variable εHf(t) values from −3.0 to 5.7, apatite 87Sr/86Sr ratios of 0.69747–0.71190, and old two-stage Hf model ages (TDM2) of 0.85–1.40 Ga. These features suggest that the Lisong and Guposhan granites may share a common magma source involving mixing of crustal and mantle-derived melts. Apatite grains from the Lisong granites display negative Eu anomalies (δEu = 0.03–0.22) and near-normal to positive Ce anomalies (δCe = 0.99–1.07), which we interpret to reflect plagioclase fractional crystallization and reduced melt conditions, respectively. Bulk rock geochemistry and multi-element systematics of the Lisong granites indicate that they represent early-stage magmatic products. Their relatively low differentiation signatures were unfavorable for Sn enrichment and mineralization in the melt, which likely explains the lack of intensive Sn polymetallic mineralization in the Lisong pluton. Full article
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