Ceramics, Volume 8, Issue 2 (June 2025) – 16 articles

In this study, we highlight the use of the alkaline earth metal barium (Ba) for the impregnation of Ag₃PO₄ (AgP). AgP was synthesized via co-precipitation and subsequently impregnated with a Ba²⁺-containing solution, followed by hydrothermal treatment to obtain Ba-AgP. The addition of barium significantly influenced both the crystallinity and crystallite size. Ba impregnation enhanced the crystallinity of AgP and promoted the growth of its crystallites. It was confirmed that Ba²⁺ was homogeneously distributed on the surface of AgP, with only a slight effect on particle shape. Ba-impregnated Ag₃PO₄ (Ba-AgP) exhibited improved photocatalytic activity for the degradation of methyl orange (MO) under visible light compared to bare AgP. The optimal impregnation concentration of Ba²⁺ was determined to be 6%. This enhancement is attributed to the role of Ba²⁺ in facilitating the separation of photogenerated electron–hole pairs, which also contributed to the improved stability of AgP. The active species h⁺, ·OH, and O₂·⁻ were all identified as essential for the MO degradation process, with h⁺ being the most significant contributor. Full article

Silicon carbide (SiC) is a highly valued material in structural ceramics due to its exceptional properties, including low thermal expansion, high mechanical strength, thermal conductivity, hardness, and corrosion resistance. These attributes make SiC suitable for a wide range of applications, from filters and electrodes to refractory and structural materials. In this study, SiC samples were produced under various conditions and characterized through techniques such as diffraction, SEM, TGA, and optical microscopy. The results indicated a band gap of 3.195 eV, an apparent density of 1.317 g/cm³, and Vickers hardness ranging from 1193 to 536 HV. Additionally, the Young’s modulus of the sample was found to be 0.4 GPa. These findings demonstrate the potential of starch consolidation for the cost-effective production of SiC ceramics with promising mechanical properties. Full article

SiAlCN coatings were first obtained by the method of reactive evaporation of aluminum and plasma chemical activation of an organosilicon precursor in a hollow cathode arc discharge. The spectrum of discharge plasma was studied by optical emission spectroscopy under conditions of evaporation of Al in an Ar+N₂+hexamethyldisilazane vapor/gas medium, and it was shown that in the presence of a metal component in the plasma, not only did intensive activation of various components of the media occur but also an increased ionic effect on the surface of the coating was provided, with a deposition rate of up to 10.1 µm/h. The films had a dense and homogeneous structure and had a hardness of up to 31 GPa and good adhesion on stainless steel. The results of SEM, FTIR, and XRD showed that their structure was a nanocomposite consisting of an amorphous matrix based on SiCN and AlN with inclusions of AlCN nanocrystals. Full article

In this study, the structural, electronic, and elastic properties of cubic zirconium dioxide (c-ZrO₂) were investigated using the Density Functional Theory (DFT) approach. Lattice parameter optimization revealed that the lattice constant is 5.107 Å, the Zr–O bond length is 2.21 Å, and the unit cell density is 6.075 g/cm³ for the B3LYP functional. The bandgap width was determined to be 5.1722 eV. The investigation of the elastic properties of the cubic ZrO₂ crystal determined the Young’s modulus, bulk modulus, Poisson’s ratio, and hardness, which were found to be 315.91 GPa, 241 GPa, 0.282, and 13 (Hv), respectively, under zero external pressure. These results confirm the mechanical stability of ZrO₂. Full article

Nickel-doped iron oxide/graphene oxide powders were synthesized by the co-precipitation method varying the Ni/Fe ratio, and the activity of the materials towards the oxygen reduction reaction in a microbial fuel cell (MFC) was studied. The samples presented X-ray diffraction peaks associated with magnetite, maghemite and Ni ferrite, as well as evidence of hematite. Raman spectra confirmed the presence of maghemite (γ-Fe₂O₃) and NiFe₂O₄. Scanning electron micrographs showed exfoliated sheets decorated with nanoparticles, and transmission electron micrographs showed spherical nanoparticles about 10 nm in diameter well distributed on the individual graphene sheet. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied by cyclic voltammetry in an air-saturated electrolyte, finding that the best catalyst was the sample with a 1:2 Ni/Fe ratio, using a catalyst concentration of 15 mg·cm⁻² on graphite felt. The 1:2 Ni/Fe catalyst provided an oxygen reduction potential of 397 mV and a maximum oxygen reduction current of −0.13 mA; for comparison, an electrode prepared with GO/γ-Fe₂O₃ showed a maximum ORR of 369 mV and a maximum current of −0.03 mA. Microbial fuel cells with a vertical proton membrane were prepared with Ni-doped Fe₃O₄ and Fe₃O₄/graphene oxide and tested for 24 h; they reached a stable OCV of +400 mV and +300 mV OCV, and an efficiency of 508 mW·m⁻² and 139 mW·m⁻², respectively. The better performance of Ni-doped material was attributed to the combined presence of catalytic activity between γ-Fe₂O₃ and NiFe₂O₄, coupled with lower wettability, which led to better dispersion onto the electrode. Full article

The introduction of side-emitting lenses into white light-emitting diodes (LEDs) has enabled thin panel lighting technology based on LED technology, but also presents the disadvantage of low color rendering due to insufficient red components in the spectra of typical white LEDs. Additional application of remote quantum dot (QD) components such as QD films or caps presents the issues of increased numbers of components and higher costs. In this study, we incorporated red QDs directly into a lens placed on white LEDs and analyzed the effects of QD lenses on the optical characteristics of a lighting device through experiments and simulations. By incorporating red CdSe/ZnS QDs into UV-curable resin to fabricate QD lenses and applying them to white LEDs, we significantly improved the color rendering index and were able to adjust the correlated color temperature over a wide range between 2700 and 9900 K. However, as the concentration of QDs in the lens increased, scattering by the QD particles was enhanced, strengthening the Lambertian distribution in the intensity plot. Following the development of optical models for QD lenses under experimental conditions, comprehensive optical simulations of white LED lighting systems revealed that increasing the device height proved more effective than modifying TiO₂ scattering particle concentration in the diffuser plate for mitigating QD-induced bright spots and enhancing illumination uniformity. Full article

This paper presents research findings on the turning of AZ31B magnesium alloy using ceramic-coated tungsten carbide tool inserts in a dry environment. Fifteen experiments were conducted according to the Box–Behnken design (BBD) for the straight turning of AZ31B magnesium alloy to investigate the variations in two important machinability indicators, i.e., material removal rate ‘MRR’ and mean roughness depth ‘R_Z’, with variations in cutting speed ‘C_S’, feed rate ‘f_r’, and depth of cut ‘DoC’. The cutting speed and feed rate had the maximum influence on the mean roughness depth and material removal rate, respectively. To address the challenge of optimizing conflicting machining responses, desirability function analysis (DFA) and grey relational analysis (GRA) were employed to identify the optimal turning parameters for conflicting machinability indicators or responses. These techniques enabled the simultaneous maximization of the material removal rate and the minimization of the mean roughness depth, ensuring an effective balance between productivity and surface quality. The optimal turning conditions—cutting speed of 90 m/min, feed rate of 0.2 mm/rev, and depth of cut of 1.0 mm—yielded the best multiperformance results with an MRR of 18,000 mm³/min and an R_Z of 2.21 µm. Scanning electron microscope (SEM) analysis of the chip and flank surface of the cutting tool insert used in the confirmation tests revealed the formation of band-saw-type continuous chips and tool wear caused by adhesion and abrasion. Full article

In the Amazon region, bauxite processing generates significant quantities of clay mineral-rich tailings, which pose a major challenge for bauxite mining operations. This study explores the use of bauxite tailings to produce fired bricks and evaluates their properties. Using a Box–Behnken experimental design, nine specimens were prepared with varying granite content (0%, 5%, 10%, 20%, and 30%) and fired at three different temperatures: 800 °C, 900 °C, and 1000 °C. The bauxite tailings contain gibbsite, kaolinite, Al-goethite, and hematite, while the granite powder comprises quartz, potassium feldspar, sodium plagioclase, muscovite, and occasionally kaolinite. Linear shrinkage values remained within recommended limits, below 8%. Apparent porosity (AP) results ranged from 60.2% to 72%, with maximum water absorption reaching 23.6%. The compressive strength of bricks without granite addition was 11.9 MPa at 900 °C, with the highest value recorded at 14.9 MPa at 800 °C when granite was added. These findings indicate that bauxite tailings, when supplemented with pulverized granite, exhibit promising potential for fired brick production. Full article

Radiation transfer in layers of densely packed aggregates of hydroxyapatite nanoparticles was studied for a spectral range from 300 to 1100 nm using diffuse reflectance measurements and the modeling of the light transfer properties of the layers. The studied samples of dispersed biogenic hydroxyapatite were obtained from animal bone material (bovine bones) using fast pyrolysis followed by grinding and pressing into tablets. A distinctive feature is the high reflectivity (high albedo) of the obtained samples, which is practically independent of the wavelength in the studied spectral range and comparable to the reflectivity of the diffuse reflectance standard based on Spectralon. The modeling of the light transfer properties of the studied samples within the framework of the effective medium theory (using coherent potential approximation) made it possible to establish the weak dependence of the mean scattering-free path and the mean transport-free path of light propagation in the medium on the wavelength, which is consistent with the features observed in the experiment. Possible prospects for the use of nanostructured hydroxyapatite as photonic material are discussed. Full article

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