Search Results (1,608)

In this study, bioceramic composites based on zirconia (ZrO₂) were synthesized and characterized in terms of mechanical properties. Two types of different-sized grains of zirconia powders were used to prepare the composites. A commercial zirconia micropowder (Tosoh) was used as a base for the composites modified with bioactive glass (BG), copper-doped bioactive glass (BGCu), and hexagonal boron nitride (hBN) with a sintering temperature of 1450 °C. The composites with the addition of hydroxyapatite, for which their sintering temperature was 1150 °C, were independently fabricated using a zirconia nanopowder prepared via co-precipitation and hydrothermal methods to achieve high densification and avoid hydroxyapatite decomposition. Mechanical performance of these composites was assessed with regard to biaxial flexural strength, Vickers hardness (HV), and fracture toughness (K_Ic). The reference 3Y-TZP material exhibited Vickers hardness (11.8 GPa) and fracture toughness (6.1 MPa∙m^1/2 values typical for dense tetragonal zirconia ceramics. The addition of all bioactive phases resulted in significant alterations in mechanical properties. Specifically, incorporating 20 wt.% HAp led to a threefold decrease in hardness and a 40% reduction in fracture toughness, while increasing the HAp content to 40 wt.% further reduced these properties. Nonetheless, the fracture toughness of these composites remained higher than that of pure hydroxyapatite materials. The incorporation of BG and BGCu reduced the hardness values by 45% and 30%, respectively, compared to 3Y-TZP. The most significant deterioration of the properties was observed for the 3Y-TZP-hBN composite. The 3Y-TZP–BGCu composite exhibited fracture toughness (5.9 MPa∙m^1/2) representing 95% of the toughness of pure zirconium dioxide, thereby showing the lowest weakness of all the other composites with bioactive additives. A slightly lower fracture toughness value (5.3 MPa∙m^1/2) was also observed in the composite with bioglass but lacking the copper additive. This factor, combined with a relatively small decrease in hardness in both cases, highlights high durability for implantology applications, thus marking the indicated materials the most promising among the composites studied. Full article

With the progressive decline of tailpipe emissions, non-exhaust sources such as brake wear are becoming an increasingly important contributor to traffic-related particulate matter in urban environments. In this context, improving real-world characterization of brake wear particles is essential for air-pollution assessment, source apportionment, and the development of cleaner and more sustainable road transport systems. Here, we investigated the emissions levels, particle size distribution and elemental composition of particles released during harsh real-world braking events by a single light-duty vehicle braking system equipped with an original manufacturer (OEM) non-asbestos organic (NAO) pad formulation. Using a direct on-vehicle sampling system combined with real-time particle sizing and high-resolution microscopy, we observed that particle emissions remained close to background levels at speeds up to 100 km/h, but rose sharply at 120 km/h, reaching 3.7 × 10⁷ #/cm³ in the 8–10 nm size range. This increase suggests that higher speeds are associated with elevated particle emissions, likely due to the higher braking temperatures reached at increased vehicle speeds. The emitted particles were mainly spherical agglomerates rich in iron, titanium, barium, zirconium, and sulphur, consistent with NAO pad formulations. Our results show that the investigated NAO pad system can deteriorate under thermal stress, potentially leading to higher levels of nanoparticle emissions compared to low-metallic or semi-metallic pads investigated under similar conditions. These findings provide real-world evidence relevant to urban air quality research, support the refinement of non-exhaust emissions inventories, and highlight the importance of thermally resilient friction-material formulations for mitigating residual particulate emissions in increasingly cleaner transport systems. Full article

Aim: This study aimed to compare two-piece zirconia and two-piece titanium implants inserted into the anterior mandible for removable overdentures in a 3-year randomized split-mouth clinical trial. Methods: Twenty fully edentulous mandibular patients received two zirconia and two titanium implants allocated by computer-generated randomization. The primary endpoint was bleeding-on-probing (BOP) at 12 months. Secondary outcomes included implant survival and success (Albrektsson criteria), marginal bone level changes, peri-implant cytokines (IL-1β, IL-6, and TNFα), prosthetic complications, and patient-reported outcomes (PROMs). Results: After 3 years, overall survival was 98.61% and overall success was 84.72%. Titanium implants showed higher success compared with zirconia implants (91.70% vs. 77.78%), while survival was 100% and 97.22%, respectively. Marginal bone loss was significantly greater around zirconia implants at 36 months (p < 0.01). No significant differences were observed in IL-1β, IL-6, or TNFα levels up to 12 months. PROMs revealed a trade-off, with zirconia favored for esthetics and cleaning perception, while titanium was rated superior for stability. Conclusions: Within the limitations of this split-mouth RCT, zirconia implants demonstrated reduced success and inferior marginal bone stability compared with titanium implants in overdenture therapy. Careful case selection and close follow-up appear essential when zirconia implants are used in this indication. Full article

Hydraulic fracturing in ultra-deep reservoirs faces significant challenges, including high wellbore friction and inadequate thermal stability of conventional fracturing fluids. To address these issues, we developed a potassium formate-weighted fracturing fluid with delayed crosslinking, excellent friction reduction, and superior temperature resistance, using a hydrophobic associating polymer thickener and a multi-ligand organic zirconium crosslinker. The weighted fracturing fluid has a density of 1.4 g/cm³ and completes crosslinking within 300 s at 90 °C. It achieves a maximum friction reduction rate of 63.2%. Below 60 °C, the system relies on a supramolecular thickener network for low viscosity and friction reduction; above 60 °C, chemical crosslinking between the thickener and zirconium ions creates a dual-network structure that significantly enhances temperature and shear resistance. After 120 min of shearing at 200 °C and 170 s⁻¹, the retained viscosity reaches 75.3 mPa·s. Complete gel breaking is achieved by sodium bromate via an oxidation reaction. This dual-network delayed crosslinking system successfully reconciles the conflict between low wellbore friction and high-temperature proppant-carrying capacity. This work presents a superior weighted fracturing fluid for ultra-deep reservoirs, as well as an innovative technique for their development. Full article

This study investigates the geochemical behavior and transport mechanisms of Rare Earth Elements (REEs), Yttrium (Y), Zirconium (Zr), and Hafnium (Hf) in three natural water systems under reducing conditions: the Santa Barbara and Occhio dell’Abisso mud volcanoes and a sulphureous spring at Villafranca Sicula. A comprehensive fractionation approach was applied to isolate the truly dissolved fraction (TDF < 10 kDa), the colloidal fraction (10 kDa < CF < 450 nm), the suspended particulate matter (SPM > 450 nm), and the associated bottom sediments. Analytical results reveal that REE distribution is significantly influenced by redox conditions and solid–liquid interface processes. The absence of negative Cerium (Ce) anomalies and the presence of pronounced positive Europium (Eu) anomalies in the Santa Barbara and Occhio dell’Abisso waters suggest strongly reducing environments where Eu²⁺ stability is enhanced. Shale-normalized patterns indicate that, while SPM and sediment fractions often exhibit Middle REE (MREE) enrichment, linked to Mn-bearing and Fe-oxyhydroxide phases, the dissolved phase reflects dissolution processes governed by a non-CHARAC (CHarge-and-RAdius-Controlled) behavior. Furthermore, the study highlights a significant decoupling in the Zr/Hf and Y/Ho pairs. While these pairs remain coherent during magmatic processes, they undergo mutual fractionation in aqueous systems due to differential reactivity toward colloidal surfaces and organic ligands. Specifically, Zr/Hf ratios in the colloidal and dissolved fractions deviate from chondritic values, driven by the preferential scavenging of Hf onto mineral surfaces. These findings underscore the utility of REE and Zr-Hf systematics as high-resolution tracers for reconstructing water–rock interaction processes and elemental cycling in complex hydrological environments. Full article

In this study, niobium/zirconium dioxide/hydroxyapatite (Nb/ZrO₂/HA) composite coating was deposited on ZK60 magnesium alloy by the plasma spraying technique. The effects of spraying power and the powder feeding rate on the surface morphology, corrosion resistance, surface hardness, and surface roughness were investigated in this study. Tests were conducted through the optimal parameter combination obtained during the optimization process. The Nb/ZrO₂/HA coating consisted of α/β-TCP, TTCP, Nb₂O₅, HA, Nb, and t-ZrO₂ phases. The results suggest that the Ca/P ratio of the coating approached the ideal calcium-to-phosphorus ratio characteristic of bone implant material surfaces. Under the parameters of 33 kw and 18 g/min, the coating exhibited a dense, flattened morphology with significantly reduced roughness of Ra = 2.128 μm. Compared to the pure HA coating, the surface hardness and corrosion resistance of the Nb/ZrO₂/HA-coated sample increased by 28% and 56%, respectively. Furthermore, the mass loss rate in simulated body fluid (SBF) was considerably decreased by 33% compared to the HA coating. In vitro cytotoxicity assay reveals that the cell proliferation activity of the Nb/ZrO₂/HA composite coating was higher than that of the HA/ZrO₂ composite coating and the HA coating. Hence, the composite coating possessed favorable degradation controllability and biocompatibility. Full article

The Zircaloy-4 alloy is a key structural material for nuclear reactor cores. However, its behavior under warm deformation conditions and during phase transformations requires in-depth investigation to improve technologies for producing ultrafine-grained (UFG) structures using severe plastic deformation methods. This work presents a comprehensive study of the rheological properties, phase stability, and microstructural evolution of the alloy in the temperature range from 20 to 950 °C at strain rates of 0.5 and 15 s⁻¹. The experimental part included plastometric testing, dilatometric analysis, and microstructural characterization. It was established that the optimal window for plastic deformation corresponds to warm deformation at 650 °C. Dilatometric analysis confirmed that heating to 650 °C ensures the preservation of a stable initial α-phase structure, since the formation of secondary phases and the α→β transformation are initiated at higher temperatures, namely 694 °C (onset) and 847 °C (completion). At 650 °C, the deformation resistance decreases by approximately 70% compared to cold processing, while the strain-rate sensitivity of the flow stress is minimized. EBSD analysis showed that deformation under these conditions leads to intensive grain fragmentation via mechanisms of dynamic recovery and the initial stages of continuous dynamic recrystallization. The decisive role of the kinetic factor was demonstrated: reducing the strain rate to 0.5 s⁻¹ promotes the formation of a finer and more homogeneous grain structure. In contrast, high strain-rate deformation (15 s⁻¹) results in coarser grains and increased non-relaxed intragranular residual stresses. The obtained results provide a physical basis for optimizing thermomechanical processing regimes and can be used to produce UFG structures in zirconium alloys without the risk of phase degradation. Full article

Titanium dental implants are widely regarded as the gold standard for the rehabilitation of missing teeth due to their high survival rates and favorable mechanical properties. However, in the oral environment, implant materials are continuously exposed to complex chemical, mechanical, and biological factors that may lead to surface degradation, including corrosion, tribocorrosion, and mechanical wear. These processes can alter implant surface characteristics and influence biological responses in peri-implant tissues. Zirconia implants have been introduced as alternative material due to their favorable aesthetics and biocompatibility. Nevertheless, zirconia ceramics are also susceptible to degradation phenomena, including hydrothermal aging, phase transformation, and surface wear under specific conditions, although their clinical relevance remains unclear. In addition, emerging hybrid titanium–zirconia implant systems introduce new considerations regarding surface stability. This scoping review, conducted in accordance with PRISMA-ScR guidelines, summarizes the current evidence on degradation mechanisms affecting titanium, zirconia, and hybrid dental implants, with particular focus on processes occurring in the oral environment and their biological and clinical implications. The available evidence differs substantially between the two materials. While titanium degradation is well documented and supported by both experimental and clinical studies, the evidence for a hybrid implant remains limited and is largely based on in vitro and mechanistic data. Full article

This study presents a capacitive sensor with a zirconium oxide (ZrO₂) coating for real-time measurement of component concentration in liquid media. The ZrO₂ layer was formed on stainless steel electrodes by magnetron sputtering, and its structural, morphological, and chemical properties were characterized using SEM, EDS, FTIR, and XRD. It was found that increasing coating thickness results in more continuous and highly crystalline layers, while reducing the influence of the substrate on surface properties. The performance of the capacitive sensor was evaluated by analysing the dependence of capacitance on frequency and NaCl concentration. The results show that the thickness of the ZrO₂ layer has a significant influence on sensor sensitivity and measurement stability. A thinner layer (~2 µm) provides higher sensitivity but is more affected by parasitic effects, while thicker layers improve measurement stability at the expense of reduced sensitivity. An optimal trade-off between sensitivity and stability is achieved at a ZrO₂ layer thickness of approximately 4 µm, ensuring sufficient sensitivity and good measurement repeatability. The results indicate that ZrO₂-modified capacitive sensors are a promising technology for monitoring liquid quality, particularly in environmental protection and industrial process control. Full article

Quantitative detection of alkaline phosphatase (ALP) activity is crucial in clinical diagnosis and bioanalysis. Herein, we have developed a highly sensitive electrochemiluminescence (ECL) biosensor that employs a biomimetic zirconia interface as its core sensing platform. The interface was constructed by immobilizing o-phosphorylethanolamine (PEA) onto zirconium oxide nanofilms (ZrO₂NFs), forming a surface rich in Zr-O-P bonds. This design mimics phosphate recognition and enzyme-triggered dephosphorylation processes, where ALP catalyzes the hydrolysis of these bonds, triggering a direct switch in the ECL signal from Ru(bpy)₃²⁺-loaded gold nanocage (Ru-AuNCs) emitters. This sensor achieves a wide linear range of 0.100–100 U/L and a low detection limit down to 0.0899 U/L. Its practical utility was validated through the accurate detection of ALP in fetal bovine serum samples, confirming high recovery and reliability. This strategy highlights the potential of biomimetic zirconia interfaces in developing robust biosensors for early disease diagnosis. Full article

This study presents the results of chemical and morphological analyses of conductive layers, indium tin oxide (ITO) and silver, deposited on lead zirconium titanate (PZT) substrates, in the form of ITO/PZT, Ag/PZT, and PZT buffer samples. The buffer layer was also examined to assess any potential impacts on the interface and was obtained by etching silver-coated PZT discs in an acid sonification bath. The ITO/PZT discs were obtained by DC sputtering. Chemical and morphological analyses were conducted using Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). XRD analysis revealed distinct diffraction peaks corresponding to the composition and crystalline structure of the various discs. This established the presence of the expected face-centered cubic (FCC) structure of silver, the perovskite phase of PZT, and the cubic bixbyite structure of the conductive ITO layer. SEM/EDS illustrated the particle distribution and elemental composition of the samples. Raman spectroscopy further corroborated the presence and identity of the surface layers of the samples. The results demonstrate that ITO/PZT structures have the expected compositions and identified impurities. SEM results give insight into possible effects on piezoelectric effects and integration into opto-electronic devices. Full article

This study investigated the radiopacity, elemental composition, cytotoxicity, and cytokine responses of contemporary calcium silicate-based cements containing different radiopacifiers. Four cement materials (NeoMTA2, NeoPUTTY, TheraCal PT, and One-Fil PT) were evaluated. Radiopacity was measured using digital radiography with a 10-step aluminum wedge and expressed in mm Al in accordance with ISO 6876; among three calibration models compared, the quadratic provided the best fit. Elemental composition was analyzed by SEM/EDX. Cytotoxicity was assessed on human dental pulp cells using the MTT assay, and IL-6 and IL-10 levels were quantified by ELISA. One-Fil PT (6.61 mm Al) and NeoPUTTY (6.09 mm Al) showed the highest radiopacity, whereas TheraCal PT (1.61 mm Al) did not meet ISO standards. SEM/EDX revealed tantalum in NeoMTA2 and NeoPUTTY, and zirconium in One-Fil PT and TheraCal PT. NeoPUTTY and NeoMTA2 demonstrated superior cell viability, while One-Fil PT showed the lowest. TheraCal PT and One-Fil PT increased IL-6 expression, whereas NeoPUTTY and NeoMTA2 promoted higher IL-10 levels. Within the limitations of this 24-h in vitro assessment, NeoMTA2 and NeoPUTTY exhibited more favorable short-term cytocompatibility and inflammatory profiles together with adequate radiopacity. These findings require confirmation through long-term in vivo and clinical studies. Full article

This study aimed to evaluate the stress and strain at the interface between zirconia crowns and prepared tooth abutments, with or without a shoulder finish line. The main objective was to determine which of the two types of preparations provides a more favorable long-term prognosis, particularly in the case of single-unit crowns. The Finite Element Analysis (FEA) method was employed to assess the mechanical response of both zirconia and dentin under occlusal forces of 200 N, simulating physiological occlusion. Values from the literature for Young’s modulus, Poisson’s ratio, and Bulk modulus were introduced into the simulations for zirconia and tooth abutments. The simulations demonstrated that zirconia crowns, regardless of the preparation type, experienced higher stress than the tooth abutments. However, preparations with a shoulder finish line demonstrated superior biomechanical behavior. This study provides a detailed biomechanical analysis of zirconia crowns cemented onto tooth abutments prepared with or without a shoulder finish line, highlighting the importance of FEA in optimizing prosthetic design and material selection. Full article

Background/Objectives: Cortisol has become established as a relevant biomarker due to its association with various pathologies, including its potential utility in mental health research. However, regarding the techniques employed for its analysis, the available literature shows a certain degree of heterogeneity both in the methods used to obtain cortisol and in the analytical techniques employed for its measurement. This makes it difficult to compare results across specific populations, particularly in pregnant women, who experience metabolic and physiological changes characteristic of gestation. Therefore, the aim of this study was to describe the procedure for the extraction and analysis of cortisol in hair samples from pregnant women throughout gestation. Methods: Hair samples, three centimeters in length, were obtained from women during the first, second, and third trimesters of pregnancy. These samples underwent a standardized isopropanol washing step, followed by milling in a laboratory mill using zirconium balls of varying diameters. The resulting hair powder was then weighed and subjected to four incubation cycles using HPLC-grade methanol. Cortisol levels were detected using chemiluminescence immunoassay. Results: Mean hair cortisol levels were 4.1 μg/L (ng/mL) in the first trimester, 11.5 μg/L (ng/mL) in the second trimester, and 6.6 μg/L (ng/mL) in the third trimester. Conclusions: Standardizing the methodology for cortisol extraction improves the reproducibility of results and, in the long term, may support its incorporation into clinical practice as a useful tool for assessing cortisol levels in both pregnant women and the general population, since hair cortisol enables retrospective evaluation of its cumulative exposure over time, approximately on a monthly basis. Full article

The performance, safety, and long-term durability of electric vehicle (EV) battery systems are strongly governed by the chemical stability and thermophysical properties of their constituent materials. In response to the limitations of conventional lithium-based batteries—particularly with respect to thermal stability, material sustainability, and degradation under high operational loads—this study presents a thermodynamic and electrochemical modeling framework for evaluating alternative battery materials relevant to electric vehicle energy storage systems. Xenon difluoride (XeF₂) and zirconium carbide (ZrC) are proposed as functional battery components and comparatively analyzed based on chemical stability, bond enthalpy, mass–capacity relationships, and energy density characteristics. Analytical modeling is employed to investigate voltage–capacity–mass interactions over a wide operating range (3–48 V and 100–1000 mAh), representing diverse EV operating scenarios, including high-load and elevated-temperature conditions. In addition, temperature-dependent degradation behavior and cycle life performance are assessed using logarithmic degradation models and Arrhenius-based life cycle formulations. The results indicate that ZrC, with a high total bond enthalpy of 561 kJ mol⁻¹, demonstrates superior energy density, reduced material mass requirements, and enhanced resistance to thermal degradation, making it particularly suitable for high-temperature and long-life EV battery applications. In contrast, XeF₂ exhibits stable electrochemical performance under moderate temperature and capacity conditions but shows increased sensitivity to thermal effects at higher operating ranges, suggesting potential applicability in balanced-performance EV battery configurations. Overall, the proposed modeling framework provides a systematic approach for assessing alternative battery materials under electric vehicle-relevant operating conditions and offers guidance for future experimental validation, material selection, and battery design aimed at improving safety, durability, and sustainability in next-generation electric vehicle energy storage systems. Full article