Search Results (416)

The Bi/Bi₂O₃-type oxygen sensor is extensively employed for oxygen monitoring in liquid lead-bismuth eutectic (LBE)-cooled reactors, yet its low-temperature measurement accuracy remains a critical bottleneck limiting engineering deployment. This study aims to extend the lower operating temperature limit of the sensor through synergistic optimization of the reference electrode and solid electrolyte. The effects of the Bi/Bi₂O₃ mass ratio, filling amount, and yttria-partially stabilized zirconia (YPSZ) electrolyte wall thickness on sensor performance were systematically investigated over 300–600 °C. Electrochemical impedance spectroscopy and finite element simulations (COMSOL Multiphysics^® 6.3, COMSOL Inc., Stockholm, Sweden) were used to elucidate the underlying mechanisms. The results show that the optimized sensor with a Bi/Bi₂O₃ mass ratio of 95:5, a filling amount of 10 g, and a YPSZ wall thickness of 1.5 mm extended the stable operating limit from 350 °C to 300 °C, achieving a relative electromotive force error of 3.13% at 300 °C and maintaining over 4000 h of drift-free service. The improved low-temperature accuracy is attributed to the reduced oxygen ion migration activation energy (0.48 eV) and lower bulk impedance of the thick-walled YPSZ after high-temperature activation. These findings provide a material optimization strategy and theoretical basis for wide-temperature-range, long-lifetime oxygen sensing in lead-based reactors. Full article

Reversible Solid Oxide Cells (rSOCs) are highly efficient energy conversion systems for power generation in fuel cell mode (SOFC) and energy storage in electrolysis mode (SOEC). These devices are typically manufactured through multi-step processing routes based on conventional functional ceramic fabrication techniques, such as tape-casting, extrusion, screen-printing and spraying. In this work, an alternative mold-casting approach is proposed for the fabrication of planar electrolyte-supported rSOCs. Electrolytes made of 8 mol% yttria-stabilized zirconia (YSZ) were prepared via an aqueous gel-casting process using agarose as the gelling agent. The casting molds were fabricated by 3D printing with polylactic acid (PLA) filament. Dense electrolytes with well-controlled geometries were successfully obtained. Complete cells were produced using porous Ni–YSZ as a fuel electrode and porous lanthanum strontium manganite–YSZ. The cells were microstructurally characterized, and their electrochemical performance was evaluated under both SOFC and SOEC operating conditions at 800–900 °C. At 900 °C, the cell achieved a peak power density of 220 mW cm⁻² in fuel cell mode and an injected current density of 340 mA cm⁻² at 1.3 V in electrolysis mode. Mid-term galvanostatic testing in SOFC mode at 850 °C for 400 h demonstrated good durability and structural stability of the fabricated cells. After the initial stabilization period, the cell exhibited a low degradation rate of 3 mV kh⁻¹. Full article

This study evaluated the influence of the manufacturing method and cementation protocol on the fracture load of zirconia molar crowns. A total of 32 full-contour crowns with a wall thickness of 1 mm were fabricated from 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP). Sixteen crowns were produced by 3D printing (LithaCon 3Y 210, Lithoz) and 16 by milling (e.max ZirCAD LT, Ivoclar Vivadent). Within each manufacturing group, eight crowns were adhesively luted with a dual-cure resin cement (Bifix QM, VOCO) and eight were conventionally cemented with a glass ionomer cement (Ketac Cem, Solventum). All crown–die complexes underwent thermomechanical aging (6000 thermal cycles between 5 °C/55 °C; 1.2 × 10⁶ cycles at 50 N) as a correlate of five years of clinical service, followed by axial loading to failure. The statistical analysis was a two-way ANOVA on log10-transformed fracture loads with manufacturing and cement as fixed effects (α = 0.05). All crowns survived thermomechanical loading without failure. Milled zirconia crowns showed significantly higher fracture loads when adhesively luted (7162 ± 1294 N) compared with conventional cementation (4021 ± 1126 N; p < 0.001). In contrast, no significant differences were observed between adhesive (4986 ± 1301 N) and conventional cementation (5581 ± 1618 N) for 3D-printed zirconia crowns. Additively manufactured crowns exhibited greater variability in fracture loads (broader interquartile ranges) than their milled counterparts. Two-way ANOVA detected a significant Manufacturing × Cement interaction (p < 0.001), indicating that the effect of cementation differed by manufacturing route. Adhesive cementation increased fracture load for milled zirconia, whereas no statistically significant cementation effect was detected for 3D-printed zirconia under the present conditions. Given the sample size and the observed variability, the study was powered to detect very large effects but not medium or small ones; therefore, this non-significant difference should not be interpreted as proof of no effect. Full article

Background/Objectives: This study evaluated the influence of sintering conditions and acidic environments on the wear of 5 mol% yttria-stabilized zirconia (5Y-ZP). Methods: Sixty zirconia specimens were divided into two sintering groups (conventional and speed) and three immersion media (n = 10): distilled water, Coca-Cola, and vinegar. Wear testing was performed using a chewing simulator under a 49 N load for 120,000 cycles, simulating 6 months of clinical function. Volume loss, mean wear depth, and surface roughness were measured using a 3D profilometer. Surface and compositional analyses were performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Results: Significant differences in wear were observed (p < 0.05). The greatest wear occurred in distilled water (58.927 ± 13.199 µm; 0.3518 ± 0.1062 mm³ for speed-sintered and 53.408 ± 6.784 µm; 0.3211 ± 0.0546 mm³ for conventional). Vinegar produced moderate wear (15.478 ± 2.584 µm; 0.0482 ± 0.0142 mm³ and 11.575 ± 3.334 µm; 0.0360 ± 0.0116 mm³), whereas Coca-Cola produced the least (2.899 ± 1.377 µm; 0.0049 ± 0.0027 mm³ and 1.870 ± 0.688 µm; 0.0027 ± 0.0012 mm³). Sintering condition affected only wear depth. SEM showed localized surface alterations in acidic media, EDS revealed reduced yttria content, and XRD revealed no detectable monoclinic phase, with no interaction between variables. Conclusions: Acidic environments had a greater influence on the wear of 5Y-ZP zirconia than sintering conditions. Speed sintering influenced wear far less than the immersion medium, supporting its use in patients exposed to acidic conditions. Full article

The mechanical compatibility between dental restorative materials and the natural tooth structure is a relevant factor for long-term clinical performance. Although zirconia (yttria-stabilized tetragonal zirconia polycrystal, Y-TZP) and lithium disilicate are widely used for full-coverage crowns, their biomechanical interaction with the underlying dentin and pulp under functional loading remains insufficiently characterized. This study reports a comparative finite element analysis (FEA) of a mandibular first molar under vertical (200 N, axial) and oblique (200 N, 30°) loading, evaluating three configurations: an intact healthy tooth, a zirconia Y-TZP full-coverage crown, and a lithium disilicate full-coverage crown. The three-dimensional geometry was obtained from a cone-beam computed tomography (CBCT) study of a caries-free mandibular first molar, previously described and verified by the present group, and was analyzed in ANSYS Workbench (Static Structural). Von Mises equivalent stress, maximum principal stress and total deformation were obtained for enamel or restoration, dentin, and pulp in each configuration. Zirconia produced the highest stress concentrations in the coronal restoration (88.4 MPa vertical; 174.5 MPa oblique), exceeding the healthy enamel baseline by 57.6% and 89.7%, respectively. Both restorative materials reduced dentin stress relative to the healthy tooth, consistent with the stress-shielding effect driven by elastic-modulus mismatch. Under oblique loading, the maximum principal stress in healthy enamel reached 61.7 MPa, approaching or exceeding the upper bound of the reported tensile strength range (~10–40 MPa) and identifying oblique loading as the more demanding of the two conditions analyzed. Within the limitations of the present finite element model, lithium disilicate demonstrated a more favorable stress distribution, with dentin stress values closer to the intact-tooth baseline. The model does not include a luting cement layer, a periodontal ligament, the dentin–enamel junction, anisotropic tissue behavior or cyclic loading, and no experimental validation was performed; the results are therefore presented as a controlled numerical comparison between three configurations under the specific conditions simulated, and not as direct clinical selection criteria. Full article

Yttria-stabilized zirconia (YSZ) thermal barrier coatings suffer from t′ phase destabilization and insufficient thermal insulation above 1200 °C. In this work, YbO_1.5-stabilized ZrO₂ powders (xYbSZ, x = 4–12 mol% YbO_1.5 on a cation basis, equivalent to 2–6 mol% Yb₂O₃) were synthesized by chemical co-precipitation, consolidated by spark plasma sintering, and evaluated at 1300 °C in terms of phase stability, sintering behavior, thermal conductivity, and fracture toughness. A common compositional boundary near 8 mol% YbO_1.5 was identified across all four responses. 8YbSZ retained the metastable t′ phase with a monoclinic content below 10 mol% after 300 h at 1300 °C, whereas grain coarsening accelerated markedly and the thermal conductivity reduction efficiency per unit doping at 1000 °C was approximately halved beyond this composition, with κ decreasing from 2.41 to 1.96 W·m⁻¹·K⁻¹ across the series. The toughness gain produced by thermal treatment fell from 34% (4YbSZ) to about 10% (10–12YbSZ) as the dominant toughening mechanism shifted from transformation and microcrack toughening (4–6 mol%) to ferroelastic domain switching (8 mol%), with both being lost in the compositions in which the cubic phase predominated. These results identify 8 mol% YbO_1.5 as the optimal composition balancing phase stability, sintering resistance, thermal insulation, and mechanical integrity for TBC applications at 1300 °C. Full article

Pitting corrosion is a more insidious and dangerous failure mode than uniform corrosion for protective coatings in marine environments, especially when sulfide ions (S²⁻) are present. In this work, Inconel 625 (IN625) and IN625-5 wt.% yttria-stabilized zirconia (YSZ) composite coatings were fabricated on 20G steel by laser-directed energy deposition (LDED) using optimized parameters. The coatings exhibit dense microstructures, with porosities of 1.87% ± 0.10% and 1.67% ± 0.10%, respectively. The pitting resistance was systematically evaluated by cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution without and with 20 ppm Na₂S. The CPP results show that the addition of YSZ decreases the pitting potential (E_pit) and protection potential (E_prot), indicating reduced resistance to pit initiation, while the smaller hysteresis loop suggests an improved tendency for repassivation. S²⁻ induces a notable drop in E_prot and impairs repassivation for both coatings, yet the IN625-YSZ coating retains a slightly higher E_prot than IN625. EIS analysis reveals that the IN625-YSZ coating in S²⁻-containing solution shows an increased R_ct of 2.738 × 10⁵ Ω·cm² compared with its counterpart in 3.5 wt.% NaCl solution, while the corresponding R_L decreases to 2.513 Ω·cm², suggesting a weakened outer barrier layer despite partial interfacial blocking. Post-corrosion morphology shows that YSZ particles act as preferential pitting nucleation sites; in sulfide-free solution they produce numerous shallow pits, whereas in S²⁻-containing solution they lead to larger and deeper pits. The results may provide a reference for the future design and evaluation of LDED-manufactured composite coatings under sulfide-containing marine environments. Full article

To evaluate whether atmospheric-pressure plasma jet (APPJ) treatment induced early, sintering-related, surface microstructural variations in 3 mol% yttria-stabilized zirconia (3Y-TZP), with a particular focus on how treatment time affected the grain size and SEM-derived surface dark-area fraction, this exploratory study examined time-dependent surface microstructural changes in commercial 3 mol% yttria-stabilized zirconia (3Y-TZP) subjected to air APPJ exposure for 4, 8, 15, 30, or 60 min under fixed device settings. A separate no-dwell furnace reference series was used to contextualize surface microstructural changes during heating; it was not used to assign an equivalent temperature to APPJ exposure. Field-emission scanning electron microscopy was used to determine surface grain dimensions and a threshold-derived surface dark-area fraction. No specimen-surface temperature was recorded during APPJ exposure. Surface grain dimensions remained similar through 15 min and increased at 30 and 60 min, whereas the surface dark-area fraction changed modestly. Under the tested conditions, prolonged APPJ exposure was associated with marked surface grain coarsening and limited change in the SEM-derived dark-area fraction. Full article

Titanium remains the gold standard in dental implantology; however, its clinical drawbacks, such as hypersensitivity reactions, metallic particle release, and aesthetically compromising discoloration, have driven interest in metal-free alternatives. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has emerged as a promising bioceramic candidate, offering favorable aesthetics, mechanical strength, and reduced bacterial plaque affinity. Its pristine surface is nonetheless bioinert, prompting extensive research into surface modification strategies, including sandblasting, acid-etching, femtosecond laser texturing, and bioactive coatings, to enhance osteoconductivity. This comprehensive narrative review synthesizes in vitro evidence on the behavior of key host cell populations—macrophages, mesenchymal stem cells, osteoblasts, fibroblasts, and epithelial cells in response to Y-TZP surface and its modifications, relevant to osseointegration and soft-tissue sealing. A literature search was conducted across PubMed, Scopus, Web of Science, and the Cochrane Library, supplemented by Google Scholar, concluding in March 2026. By integrating findings across multiple cell lineages, this review aims to clarify how engineered zirconia topographies modulate cell-specific pathways, thereby informing the development of next-generation implants optimized for biological integration. Full article

Background/Objectives: Fracture of ceramic femoral heads in total hip arthroplasty is a rare but catastrophic complication requiring urgent revision surgery. Most finite element studies are limited to static loading and do not capture dynamic behavior under impact conditions from stumbling or falling. The objective was to determine impact fracture thresholds of alumina (Al₂O₃) and yttria-stabilized zirconia (ZrO₂, Y-TZP) femoral heads using explicit dynamic finite element analysis. Methods: A parametric explicit dynamic analysis was performed using LS-DYNA (version 960) on an axisymmetric model of a 32 mm ceramic femoral head articulating with a ceramic liner within a Ti-6Al-4V acetabular shell. Ceramic behavior was described by the Johnson–Holmquist JH-2 damage model, validated against published impact and retrieval data. Bone stock viscoelasticity was a Winkler foundation (stiffness 50–500 N/mm, damping 0–1.0 N·ms/mm). Impact velocity ranged from 0.01 to 0.45 mm/ms, consistent with implant telemetry during stumbling. Fracture criteria were plastic strain, principal stress, and energy inflection. A sensitivity analysis of estimated ZrO₂ parameters was performed. Results: For Al₂O₃, the critical fracture velocity was 0.08 mm/ms under rigid fixation and 0.05 mm/ms with a viscoelastic foundation. The ZrO₂ head did not fracture at any velocity tested; at V ≥ 0.20 mm/ms, the neck deformed plastically while the head remained intact. Foundation stiffness and damping had no influence on outcome. Conclusions: These findings indicate inertia-dominated fracture mechanics for Al₂O₃ at realistic velocities, and suggest a material-dependent shift in critical failure location toward the taper junction for ZrO₂, a tendency warranting experimental confirmation. Full article

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were fabricated by atmospheric plasma spraying (APS). Three CMAS powders with different compositions (CMAS-1, CMAS-2, CMAS-3) were selected, and corrosion tests were carried out at 1200 °C, 1250 °C, and 1300 °C. The relationships among CMAS viscosity, melting point, and reaction tendency with YSZ coatings were investigated. The results show that CMAS-3 possesses the highest viscosity yet the lowest melting point, CMAS-1 has the lowest viscosity but the highest melting point, and CMAS-2 falls between the two. Quantitative penetration depth measurements reveal that higher viscosity leads to slower infiltration, while a lower melting point enables earlier infiltration onset. At elevated temperatures, all CMAS compositions achieve complete penetration, indicating that the differences in melting point and viscosity become less critical when the temperature is sufficiently high. Corrosion tests reveal that CMAS-3 exhibits the strongest reaction tendency with YSZ coatings, while CMAS-1 shows the weakest. This indicates that the infiltration behavior is governed by a dual control of melting point and viscosity—melting point determines the onset of infiltration, while viscosity controls the penetration rate. This study provides an experimental basis for the design of CMAS-resistant coatings and the evaluation of their environmental adaptability. The key finding is that the melting point plays a dominant role in initiating CMAS infiltration, while viscosity primarily regulates the penetration rate. Full article

High-translucency 4 mol% yttria-partially stabilized zirconia (4Y-PSZ) is widely used for esthetic restorations, but sintering conditions that balance translucency and microstructural control remain unclear. This study evaluated the independent effects of peak temperature, holding time, and heating rate on the microstructure and total luminous transmittance of monolithic 4Y-PSZ. Disks were sintered at peak temperatures of 1470–1560 °C, holding times of 30–180 min, and heating rates of 3–10 °C/min. Grain size and internal defect density (≥0.5 µm) were quantified by scanning electron microscopy, and total luminous transmittance at 0.5 mm thickness was measured using a spectrophotometer. Higher peak temperatures and longer holding times increased grain size (0.481 ± 0.020 to 0.785 ± 0.035 µm, and 0.503 ± 0.037 to 0.730 ± 0.041 µm, respectively) and reduced defect density, whereas heating rate had no significant effect on either. Transmittance remained within a narrow range (approximately 40–43% at 0.5 mm) across all schedules, with 1560 °C yielding the lowest value. These findings indicate that the microstructure of monolithic 4Y-PSZ is governed primarily by peak temperature and holding time, while transmittance is relatively insensitive to the sintering schedule. Practically, a peak temperature of 1500–1530 °C with a 1–2 h hold provides a robust processing window balancing densification, grain coarsening, and optical performance for clinical workflows. Full article

To address the issue of depositing thermal barrier coatings (TBCs) on rotating curved surfaces, atmospheric plasma spraying (APS) was employed to prepare yttria partially stabilized zirconia (YSZ) coatings on a rotating curved substrate. Three standoff distances of 80 mm, 100 mm and 120 mm were selected. The microstructure, microhardness, elastic modulus and fracture toughness of three YSZ coatings were tested. The results indicate that as the standoff distance increased from 80 mm to 120 mm, porosity increased from 11.27% to 13.29%, microhardness decreased from 760.8 HV_0.3 to 713.2 HV_0.3, elastic modulus decreased from 24.0 GPa to 22.6 GPa, and fracture toughness decreased from 1.14 MPa·m^1/2 to 1.04 MPa·m^1/2. The properties of the YSZ coating in the case, such as elastic modulus and fracture toughness, were significantly lower than those of the YSZ coating deposited on stationary planar substrates. Solidification of the molten particles impacted on rotating curved substrates was accelerated and splat spreading was constrained because of the coupled effect of centrifugal force and elevated cooling rate. Therefore, under identical spraying parameters, the process parameters optimized for planar substrates cannot be directly transferred to rotating curved components. Full article

Advanced thermal barrier coatings (TBCs) are essential for improving the efficiency and performance of gas turbine engines. Increasing engine operating temperatures and harsh service environments are pushing the current industry-standard 8 wt% yttria-stabilized zirconia (8YSZ) to its performance limits. High-rare-earth-oxide zirconates, such as Gd₂Zr₂O₇, have emerged as promising materials for next-generation engines due to their excellent high-temperature phase stability, lower thermal conductivity, and enhanced resistance to CMAS attack. In this work, dense vertically cracked (DVC) Gd₂Zr₂O₇/8YSZ bilayer coatings were developed using the air plasma spray (APS) process. Two approaches were employed for deposition of the NiCrAlYHfSi bond coat: (i) high-velocity oxygen fuel (HVOF), and (ii) APS flash-coated HVOF NiCrAlYHfSi bond coat. The durability of DVC TBC systems with the two bond coat types was evaluated by furnace cycling test (FCT) at 1125 °C. The TBC system with an APS flash-coated HVOF bond coat exhibited an FCT lifetime approximately twice that of the system with the HVOF bond coat alone. The improvement is primarily attributed to the higher surface roughness of the APS flash-coated bond coat, which enhances resistance to crack initiation, propagation, and linkage, thereby extending thermal cycling life. Full article

With the advancement of energy storage technology, there have been significantly increased demands for the storage performance and operating temperature of capacitor dielectric materials. As a high-temperature resistant polymer, polyimide (PI) shows great potential for application as a dielectric material. In this study, binary PI composite films with various contents of yttria-stabilized zirconia particles (YZPs) were prepared via in situ polymerization. The results demonstrated that the incorporation of YZPs enhanced the breakdown resistance compared to pure PI films. Specifically, at a YZP content of 8 wt%, the breakdown strength (BDS) of the composite films reached 566 kV·mm⁻¹. Although the mechanical strength exhibited a slight reduction, the dielectric properties remained stable, leading to an overall improvement in energy storage performance. Overall, 2 wt% YZPs/PI (with 5 mol% Y₂O₃, ZPb2) film is optimal in terms of its mechanical and dielectric properties. This research establishes a solid foundation for the engineering development and industrial implementation of high-performance PI-based polymer dielectric materials. Full article