Search Results (566)

This study explores the optimization of foam ceramic materials through experimental research and mathematical modeling. The goal was to enhance mechanical strength, thermal insulation, porosity, water absorption, and density by adjusting composition and firing conditions. Regression analysis and response surface methodology were used to assess the effects of loam, fly ash content, and the firing temperature. The optimal composition of 60–65% loam, 10% fly ash, and a firing temperature of 950–1000 °C yielded foam ceramics with a bulk density of 680–700 kg/m³, a compressive strength of 3.5–4 MPa, and a thermal conductivity of 0.135–0.140 W/(m·K). Controlled porosity (70–72%) enhanced insulation while maintaining structural integrity. X-ray diffraction confirmed mullite, quartz, and cristobalite phases, with mullite improving mechanical properties. This research demonstrates the potential of optimized foam ceramics for energy-efficient construction. Mathematical modeling and experimental validation provide a pathway for developing lightweight, high-performance ceramic materials. Future work should refine sintering processes, explore new additives, and evaluate the long-term performance. Full article

Substantial tooth bonding is the defining characteristic of effective minimally invasive all-ceramic restorations. Natural and synthetic cross-linkers that could strengthen the bonding quality are currently drawing enormous interest. Thus, this study aimed to assess the microtensile bond strength and nanoleakage of computer-aided design/computer-aided manufacturing (CAD/CAM)-fabricated ceramics to pretreated dentin with chlorhexidine or Salvadora persica extract, compared to no pretreatment, after thermomechanical cyclic loading. Consequently, forty-five extracted third-molar teeth (n = 45) were utilized to obtain mid-coronal dentin and assigned into three groups (n = 15) in accordance with dentin pretreatment; (group I: no dentin pretreatment (control), group II: 2% chlorhexidine, and group III: Salvadora persica extract pretreatments). Ceramic onlays were milled from lithium disilicate IPS e.max CAD/CAM blocks and cemented to prepared teeth with etch-and-rinse resin cement (Variolink Esthetic DC system kit). Microtensile bond strength and interfacial nanoleakage were accessed after thermomechanical cyclic loading. Statistical analysis was performed using one-way ANOVA, followed by Tukey’s post hoc test. Additionally, p-values < 0.05 were considered statistically significant. The chlorhexidine pretreated group showed the most favorable outcome compared to the control group. Conversely, using Salvadora persica pretreatment did not affect the bond strength and nanoleakage compared to the control group (p > 0.05). Consequently, unlike Salvadora persica extract, chlorhexidine–dentin pretreatment maintained superior bonding strength to ceramics after thermomechanical cyclic loading, facilitating minimally invasive, yet lasting, aesthetic restoration. Full article

Objective: The purpose of this investigation was to assess and compare the internal adaptation of different distinct CAD (Computer-aided design)/CAM (Computer-aided manufacturing) endocrown materials: feldspathic porcelain, indirect composite, hybrid ceramic, reinforced lithium disilicate, and lithium disilicate, utilizing microcomputed tomography. Methods: Standardized endocrown restorations were fabricated for mandibular first molar models. A total of seventy-five restorations were evenly allocated into five groups (n = 15 each): Group I (Cerec Blocks), Group II (Lava Ultimate), Group III (PICN Vita Enamic), Group IV (Celtra Duo), and Group V (Cerec Tessera). The restorations were bonded using PANAVIA V5 adhesive resin cement. To evaluate internal adaptations within the restorations, three distinct locations were selected for the acquisition of high-resolution micro-CT scans: the margin, the axial wall, and the pulpal floor. Data were analyzed using SPSS. To identify statistically significant differences among groups, a two-way ANOVA was conducted, followed by post hoc Tukey tests. Results: The statistical analysis did not reveal significant differences in internal gap measurements across the various material groups (p = 0.055). However, significant variations were observed within individual material groups (p < 0.001) at distinct locations, with the most pronounced discrepancies in thickness evident at the pulpal floor. Conclusion: While no significant differences were observed in internal adaptations among the various endocrown materials, substantial intra-group variability, particularly in terms of pulpal floor thickness, was evident. Since the study maintained a consistent preparation design across all groups, the observed variations in internal adaptation are likely attributed to differences in material behavior rather than changes in preparation geometry. Full article

This work presents the design and synthesis of novel high-entropy perovskite oxides (HEPOs) derived from BaCeO₃, formulated using the cluster-plus-glue atom model. Particularly, through a carbonate-based co-precipitation technique, we synthesized three novel high-entropy perovskite oxides (HEPOs) derived from barium cerate by substituting cerium with different combinations of five different elements (Ce, Zr, Yb, Sm, La, Gd, Nd) in equal molar ratios, i.e., Ba(Ce_0.2Zr_0.2Yb_0.2La_0.2Sm_0.2)O_2.7, Ba(Ce_0.2Sm_0.2Yb_0.2Nd_0.2Gd_0.2)O_2.6, and Ba(Ce_0.2Zr_0.2Nd_0.2La_0.2Sm_0.2)O_2.7. Upon calcination of the as-synthesized samples at different temperatures and subsequent quenching, the formation of an entropy-stabilized single phase was analyzed and assessed. To rationalize the observed differences in phase evolution, a novel set of empirical descriptors, including configurational entropy, Goldschmidt tolerance factor, and B-site size mismatch, was proposed and discussed. With the aim of studying the sinterability of the single-phase samples, the calcination treatment was optimized by reducing its temperature and duration (i.e., 1300 °C for 6 h) so that subsequent densification higher than 95% was achieved by sintering at 1500 °C for 6 h. Full article

During the Islamic period, ceramic workshops were commonly established in settlements throughout the Gharb al-Andalus region (Western Iberia at the time), to produce ceramics for local supply. Along the middle valley of the Tagus river (i.e., nowadays central Portugal), hundreds of Islamic ceramic sherds, either glazed or common wares, were recovered over different archaeological excavations. At the archaeological site of Serradinho, located at Muge (Municipality of Salvaterra de Magos, Santarem District, Portugal), a fortuitous finding was unearthed during agricultural works in which ceramic sherds from the Emiral (8–9th century) to the Almoravid (mid–12th century) period were recorded. The uninterrupted time lapse evidenced by these ceramic artefacts is a one-off opportunity to trace back early Islamic ceramic production and to link it with the long-lasting ceramic tradition documented at Muge by ethnographic studies. In this study, insights into the provenance of raw materials and the pottery-manufacturing processes will be approached by means of different optical and analytical methods, namely Optical Microscopy (OM), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy (SEM-EDS) and granulometric tests on sediments offering some interesting parallels between archaeological and modern ceramic production. Results suggested that most ceramics were locally produced, while others were imported into the settlement during the Islamic Middle Ages. Moreover, data indicate that a locally available raw material which is still used nowadays for the production of traditional ceramics had been employed. This result confirms the exploitation of the same raw material over time, linking Islamic Middle Ages ceramic production to the modern one. Full article

The development of energy-efficient and sustainable construction materials is essential for reducing environmental impact and enhancing building performance. This study investigates the incorporation of coffee grounds and expanded perlite waste—two underutilized industrial byproducts—into clay-based ceramics to improve thermal insulation while maintaining mechanical integrity. Unlike previous studies that explore these additives separately or in impractically high dosages, this research focuses on their combined effect at low, industrially viable ratios to ensure large-scale feasibility. Four clay mixtures were analyzed: a reference clay (TZ), clay with coffee grounds (TZCF), clay with expanded perlite waste (TZPW), and clay with both additives (TZCFPW). Laboratory testing and computational fluid dynamics (CFD) simulations were employed to assess the physical, mechanical, and thermal properties of these formulations. The results indicated that coffee grounds increased plasticity, while expanded perlite waste reduced it, requiring adjustments in processing parameters. Both additives contributed to lower shrinkage and drying sensitivity, improving dimensional stability during production. Although mechanical strength declined due to increased porosity—most notably in the TZPW mixture—the fired bending strength remained within acceptable limits for masonry applications. The most significant finding was the substantial improvement in thermal performance, with all the modified formulations exhibiting reduced thermal conductivity and enhanced insulation. The best performance was observed in the TZPW mixture, which demonstrated the lowest thermal conductivity, highest thermal resistance, and optimal U-values in masonry wall testing, confirming its potential for energy-efficient construction. CFD simulations further validated these enhancements, providing detailed insights into heat transfer mechanisms. These findings demonstrate the feasibility of repurposing industrial waste materials to create scalable, eco-friendly building products. Future research should refine formulation ratios to optimize the balance between strength and insulation, ensuring widespread adoption in sustainable construction. Full article

Oxide coatings formed by plasma electrolytic oxidation (PEO) of tungsten substrate for 10 min in a phosphate alkaline electrolyte (PAE, 2 g/L Na₃PO₄·12H₂O) with an addition of 2 g/L, 3 g/L, and 4 g/L NaAlO₂ were investigated by SEM/EDS and XRD. In PAE + 2 g/L NaAlO₂, a weakly crystalline coating is formed, consisting of amorphous Al₂O₃, the triclinic phase of WO₃, the cristobalite phase of AlPO₄ and the gamma and alpha phases of Al₂O₃. Strong micro-discharges during PEO in PAE with the addition of 3 g/L and 4 g/L NaAlO₂ lead to the crystallization of amorphous Al₂O₃ into gamma-Al₂O₃ and alpha-Al₂O₃ phases. The coating formed in PAE + 4 g/L NaAlO₂ is well crystallized and rich in alpha-Al₂O₃, which makes it suitable for high-temperature applications. To explain the composition of the formed coatings and the transformation of the amorphous Al₂O₃ into gamma and alpha phases, we followed the change in morphology, thickness, chemical and phase composition of the coatings during PEO in PAE + 4 g/L NaAlO₂. Full article

In response to environmental challenges and primary resource scarcity, sustainable approaches that rely on recycling and reusing waste materials are becoming valuable and highly appealing options in modern society. This paper deals with the usage of porous glass and glass-ceramic products derived from waste in the field of thermal insulation in buildings. After providing an overview of the current state of the art with a focus on existing commercial products and related manufacturing methods (foaming strategies), this review discusses the emerging trends toward greener approaches, including the use of by-products or waste substances as foaming agents (e.g., eggshells or mining residues), the use of vitrified bottom or fly ashes from municipal solid waste incinerators as starting materials, the application of surface treatment to reduce post-processing temperatures, and the promise of additive manufacturing technologies in this field. The increased use and spread of sustainable practices are expected to significantly contribute to glass recycling, to minimize landfilling, and to generally reduce energy consumption as well as greenhouse emissions. Full article

The expansion, cracking and deterioration of properties during utilisation and solidification of municipal solid waste incineration bottom ash are key problems that are caused by the reaction of metallic aluminium in the bottom ash in the highly alkaline environment of hardened Portland cement. In this study, polyaluminium sulphate (PAS) was introduced into ordinary Portland cement (OPC) to inhibit the corrosion of aluminium alloy. The results indicate that PAS successfully inhibited the corrosion of Al in hardened OPC paste, prevented the expansion and cracking, reduced the amount of hydrogen gas release and formed a thinner and dense corrosion layer on the Al plate surface. The mechanism of corrosion inhibition of Al by PAS was the increase of initial Al(OH)₄⁻ concentration by hydrolysis, which expanded the pH range of passivation and transformed the porous loose bayerite layer to a dense homogeneous one around the Al plate without modification of the corrosion product (bayerite). The corrosion rate of the Al alloy in hardened OPC paste was reduced by 213 times by the addition of PAS, from 288.30 mm a⁻¹ without PAS addition to 1.35 mm a⁻¹ with PAS addition. This study casts light on the effective inhibition of corrosion of the Al alloy in OPC. Full article

In this work, the impact resistance of three zirconia ceramics was investigated: two yttria-stabilized zirconia (3Y-TZP and 1.5Y-TZP) and a ceria-stabilized-zirconia (Ce-TZP) composite. The impact resistance was evaluated through drop-ball impact tests on disk-shaped samples. The results are discussed in terms of the materials’ transformability, which was correlated to the size of tetragonal-to-monoclinic (t-m) transformation zones observed after the impact tests and to the volume fraction of the monoclinic content on fractured surfaces. The findings show that impact resistance increases with the ability of the material to undergo t-m transformation. The Ce-TZP composite exhibited the highest transformability and consequently the highest impact resistance, followed by 1.5Y-TZP, and then 3Y-TZP. Full article

The present study analyzes experimental data using qualitative and quantitative methods to identify significant statistical changes. These methods were employed to evaluate the results from the structural characterization of annealed TiWN and TiWC coatings elaborated by magnetron sputtering. The as-grown coatings were thermally treated at 500 °C in a furnace under an Ar atmosphere. Structural characterization was performed by X-ray diffraction and optical and electronic microscopy. The chemical composition was determined by energy dispersive X-ray spectroscopy. The data were analyzed using the Kruskal–Wallis (K-W) and Spearman correlation tests as non-parametric methods, employing free statistical software. The response variable—the crystallite size calculated through the Scherrer formula—is statistically tested. The data of the crystallite size of each sample were forecasted using the simple moving average (SMA) method to increase the number of data points of each sample to 12. The crystallite size of each sample remained unchanged before and after thermal treatment. However, microscopy analyses revealed strong surface cracking. The average crystallite size before and after the thermal treatment was analyzed by the K-W correlation, revealing significant changes considering a reliability level of 95% and a significance error of 5%. The analysis revealed a strong correlation between experimental data and statistical treatment results. Full article

Zirconolite is a wasteform that can immobilize Pu. Herein, zirconolites comprising Ce as a Pu simulant and Al as a charge compensator of Ce/Pu were synthesized by sintering raw CaO, ZrO₂, TiO₂, CeO₂, and Al₂O₃ powder mixtures at 1400 °C in static air. The reduction behavior and phase transformation of zirconolites during their heat treatment in an Ar–H₂ gas flow were investigated. In pure and Ce–Al co-doped zirconolite compositions, 2M-zirconolite and small amounts of perovskite were obtained after sintering. In contrast, 2M-, 4M-zirconolite and relatively large amounts of perovskite were obtained in Ce-doped zirconolite composition. All zirconolite compositions first underwent reduction at ~1050 °C by forming a small domain of perovskite phase. Ce–Al co-doped zirconolite showed a smaller fraction of phase transformation in perovskite than Ce-doped zirconolite, indicating the advantage of using a charge compensator to prevent perovskite formation. Full article

This study investigates the thermal shock behavior of three Al₂O₃-SiO₂ commercial insulating refractory materials (JM23, JM26, and JM28) used in high-temperature industries (>1000 °C). Thermal shock resistance was evaluated through experimental tests and compared with theoretical parameters (R, R⁗, R_st) based on thermoelastic and thermomechanical models. The tests revealed that JM23 did not withstand thermal shock due to its fragility when in contact with water at room temperature, resulting in its immediate collapse. In contrast, JM26 and JM28 maintained their mechanical strength after several thermal shock cycles, although JM28 experienced a more significant decrease in compressive strength. The mechanical behavior under compression changed from semi-fragile to apparently plastic after severe heat treatments. Porosity analysis showed that JM26 had a lower pore size distribution, which contributed to its better thermal shock performance. Theoretical parameters were calculated, confirming that JM26 exhibited the highest resistance to thermal shock. These findings suggest that controlled porosity and microstructure are key factors in improving the thermal performance and durability of insulating refractory materials in high-temperature applications. Full article

The direct hot modification and subsequent preparation of qualified building materials from molten slag has gained significant attention at present due to its characteristics of saving energy and reducing CO₂ emissions. Molten silicomanganese slag, discharged at 1500–1600 °C with high content of SiO₂ and Al₂O₃ (above 50 mass%), was suitable for the preparation of casting stone. To ensure a qualified casting stone, the study focused on improving the crystallization properties and fluidity of molten silicomanganese slag by modifying of its composition, crystallization, structure, and viscosity. The raw slag and two modified slags were compared, and the physical properties of their final cast stone were discussed. The results showed that after being modified by addition of 10 mass% chromite and serpentine or 20 mass% ferrochrome slag into the silicomanganese slag, both the crystallization ability and fluidity of the molten slag were improved simultaneously. Augite and spinel precipitated in the modified slag, compared with glass phase in the raw slag. The precipitation of spinel, on the one hand, acted as a nucleation agent, dynamically promoting the formation of augite, and on the other hand, increased the proportion of SiO₂ and its polymerization of [SiO₄] structural units in the residual liquid slag, further promoting the generation of augite in the composition and structure. The gradual precipitation of crystals effectively mitigated sudden viscosity fluctuations resulting from crystallization, contributing to a smooth casting process for molten slag. Both cast stones from the modified slag exhibited qualified physical properties, compared with the broken glass from the raw slag. This indicated the feasibility of low-cost modification during the discharging process of molten silicomanganese slag by blending 10 mass% cold modifiers or 20 mass% molten ferrochrome slag into it. Full article

In this work, a new methodology for dispersing metal particles supported in clay has been described. For this purpose, a sepiolite has been modified by a microwave-assisted treatment to increase the surface area and pore volume due to the progressive leaching of the Mg²⁺-species located in the octahedral sheet. These materials have been used as support to incorporate Cu species on the surface by a precipitation-deposition process from the thermal decomposition of urea at 95 °C. Once calcined and reduced, the Cu-based catalysts showed a Cu⁰-particle size lower than 5 nm in the case of catalysts whose support is a sepiolite subjected to acid treatment. On the other hand, when raw sepiolite is used as a support, the Cu⁰-crystal size is much larger (15–20 nm). This difference in Cu⁰-crystal size showed a variable catalytic behavior for the hydrogenation reaction of furfural in gas-phase. Catalysts with larger particle size promote the hydrogenation reaction, obtaining a yield towards furfuryl alcohol close to 60% after 5 h at 190 °C. In contrast, catalysts with smaller particle size promote the hydrogenation reaction and subsequently the hydrogenolysis reaction, obtaining methylfuran as a product with a yield of 58% after 1 h of reaction at 190 °C; however, the sites where hydrogenolysis are involved are more prone to be deactivated. Full article