Search Results (202)

Vital pulp therapy with calcium hydroxide or mineral trioxide aggregate (MTA) rapidly induces dystrophic calcification and promotes the accumulation of two members of small integrin-binding ligand N-linked glycoproteins: osteopontin (OPN) and dentin matrix protein-1 (DMP1). However, the precise relationship between these initial events and their roles in reparative dentinogenesis remain unclear. This study aimed to clarify the relationship between dystrophic calcification, OPN and DMP1 accumulation, and reparative dentin formation. Pulpotomy was performed on rat molars using MTA or zirconium oxide (ZrO₂). ZrO₂ was used as a control to assess pulp healing in the absence of dystrophic calcification. Pulpal responses were evaluated from 3 h to 7 days postoperatively via elemental mapping, micro-Raman spectroscopy, and histological staining. In the MTA-treated group, a calcium-rich dystrophic calcification zone containing calcite and hydroxyapatite was observed at 3 h after treatment; OPN and DMP1 accumulated under the dystrophic calcification zone by day 3; reparative dentin formed below the region of OPN and DMP1 accumulation by day 7. In contrast, these reactions did not occur in the ZrO₂-treated group. These results suggest that dystrophic calcification serves as a key trigger for OPN and DMP1 accumulation and plays a pivotal role in reparative dentinogenesis. Full article

Complex oxides with the general formula Gd₂(Ti_1−xZr_x)₂O₇ are promising candidates for radioactive waste immobilization due to their capacity to withstand radiation by dissipating part of the free energy driving defect creation and phase transitions. In this study, samples with varying zirconium content (xZr = 0.00, 0.15, 0.25, 0.375, 0.56, 0.75, 0.85, 1.00) were synthesized via the sol–gel method and thermally treated at 500 °C to obtain nanosized powders mimicking the defective structure of irradiated materials. Synchrotron-based techniques were employed to investigate their structural properties: High-Resolution X-ray Powder Diffraction (HR-XRPD) was used to assess long-range structure, while Pair Distribution Function (PDF) analysis and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy provided insights into the local structure. HR-XRPD data revealed that samples with low Zr content (xZr ≤ 0.25) are amorphous. Increasing Zr concentration led to the emergence of a crystalline phase identified as defective fluorite (xZr = 0.375, 0.56). Samples with the highest Zr content (xZr ≥ 0.75) were fully crystalline and exhibited only the fluorite phase. The experimental G(r) functions of the fully crystalline samples in the low r range are suitably fitted by the Weberite structure, mapping the relaxations induced by structural disorder in defective fluorite. These structural insights informed the subsequent EXAFS analysis at the Zr-K and Gd-L₃ edges, confirming the splitting of the cation–cation distances associated with different metal species. Moreover, EXAFS provided a local structural description of the amorphous phases, identifying a consistent Gd-O distance across all compositions. Full article

The aim of this work was the preparation of ceramic monolithic catalysts for the catalytic oxidation of gaseous mixture of benzene, toluene, ethylbenzene and o-xylene BTEX. The possibility of using zirconium dioxide (ZrO₂) as a filament for the fabrication of 3D-printed ceramic monolithic carriers was investigated using fused filament fabrication. A mixed manganese and iron oxide, MnFeO_x, was used as the catalytically active layer, which was applied to the monolithic substrate by wet impregnation. The approximate geometric surface area of the obtained carrier was determined to be 53.4 cm², while the mass of the applied catalytically active layer was 50.3 mg. The activity of the prepared monolithic catalysts for the oxidation of BTEX was tested at different temperatures and space times. The results obtained were compared with those obtained with commercial monolithic catalysts made of ceramic cordierite with different channel dimensions, and with monolithic catalysts prepared by stereolithography. In the last part of the work, a kinetic analysis and the modeling of the monolithic reactor were carried out, comparing the experimental results with the theoretical results obtained with the 1D pseudo-homogeneous and 1D heterogeneous models. Although both models could describe the investigated experimental system very well, the 1D heterogeneous model is preferable, as it takes into account the heterogeneity of the reaction system and therefore provides a more realistic description. Full article

This work provides a comprehensive investigation into the synergistic effects of zirconium and oxygen on the microstructural evolution, high-temperature oxidation resistance, and mechanical properties of γ-phase Ti52AlxZr alloys (x = 0, 0.5, 1, and 2 at.%) under systematically controlled oxygen concentrations. Unlike prior studies that have examined these alloying elements in isolation, this study uniquely decouples the contributions of interstitial (oxygen) and substitutional (zirconium) solutes by employing low (LOx) and high (HOx) oxygen levels. Alloys were synthesized via vacuum arc melting and subsequently subjected to homogenization annealing at 1250 °C for 100 h to ensure phase and microstructural stability. Characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) were employed to elucidate phase constitution and grain morphology. Zirconium addition was found to stabilize the γ-TiAl matrix, suppress α₂-phase formation, and promote grain coarsening in LOx specimens. Conversely, elevated oxygen concentrations led to α₂-phase precipitation along grain boundaries. Mechanical testing, comprising Vickers hardness and uniaxial compression at ambient and elevated temperatures (800 °C), revealed that both zirconium and oxygen significantly enhanced strength and hardness, with Ti52Al2Zr delivering optimal mechanical performance. Moreover, zirconium substantially improved oxidation resistance by promoting the formation of a thinner, adherent Al₂O₃ scale while simultaneously inhibiting TiO₂ growth. Collectively, the findings demonstrate the critical role of zirconium in engineering advanced γ-TiAl-based intermetallics with superior high-temperature structural integrity and oxidation resistance. Full article

Hydroxyapatite (HAP) is the most widely accepted biomaterial for repairing bone tissue defects, demonstrating excellent biocompatibility and bioactivity that promote new bone formation. Zirconia (ZrO₂), known for its strength and fracture toughness, is commonly used to reinforce ceramics. In this study, magnesium oxide (MgO) served as a stabilizer for zirconia, resulting in magnesia partially stabilized zirconia (Mg-PSZ). Both Mg-PSZ and HAP were synthesized via coprecipitation and mixed in specific ratios to create composites through a ceramic method involving mixing, compaction, and sintering at 1100 °C. The samples were characterized using techniques such as X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Structural analyses confirmed the presence of both monoclinic and tetragonal zirconia phases. Besides, the increased wt.% HAP in the composites produced distinct peaks for hexagonal HAP. Crystallite sizes ranged from 27.45 nm to 31.5 nm, and surface morphology was homogeneous with small pores. Elements such as calcium, phosphorus, magnesium, zirconium, and oxygen were detected in all samples. This research also examined microhardness changes in the materials. The findings revealed enhancement in microhardness for the biocomposite with higher zirconia content, 90Mg-PSZ/10HAP sample, with the smallest average pore size, highlighting its potential for biomedical applications. Full article

Zirconium, a critical rare metal with exceptional corrosion resistance and nuclear applications, is conventionally produced via the energy-intensive Kroll process. The electrolysis of ZrC_xO_y soluble anodes has been extensively investigated due to its advantages in having a short process flow and resulting in high-quality products. In particular, during the electrolysis of zirconium oxycarbide with a C:O molar ratio of 1:1, gaseous CO can be released, and no residual anodes are generated, which is extremely appealing. In this regard, this paper explores the feasibility of preparing zirconium metal through high-temperature vacuum reduction to produce zirconium oxycarbide using ZrO₂ as the raw material, followed by direct molten-salt electrolysis. Firstly, the reduction products were characterized using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The results showed that under a vacuum of <10 Pa at 1750 °C, the reduction products mainly consisted of ZrC_xO_y and a small amount of ZrO₂, and they exhibited good electrical conductivity (0.0169 Ω·cm). Subsequently, the cyclic voltammetry test results of the reduction products revealed the reversible redox behavior of ZrC_xO_y. There were characteristic oxidation peaks at −0.53 V and −0.01 V (vs. Pt), corresponding to the formation of Zr²⁺ and Zr⁴⁺, respectively, and a reduction peak at −1.51 V, indicating the conversion from Zr²⁺ to Zr. Finally, β-zirconium metal with a purity of 99.2 ± 0.3 wt.% was obtained through potentiostatic electrolysis, and its quality met the R60704 grade specified in ASTM B551-12 (2021). This study offers a novel approach for the short-flow preparation of zirconium metal, which is conducive to expanding its applications. Full article

Glass ionomer cements (GICs) have been clinically attractive dental restorative materials for many years and are widely used as luting, lining, and restorative materials. However, these materials still have limitations in terms of weak physio-mechanical properties. The aim of the study was to evaluate the effect of zirconium oxide nanoparticles (nano-ZrO₂ particles) on the physical and mechanical properties of two commercially available GICs. Four groups were prepared for each material: the control group (without nanoparticles) and three groups modified by the incorporation of nanoparticles at 2, 5, and 7 weight% (wt%). Firstly, the morphology and size of the nanoparticles were evaluated via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Secondly, flexural strength, flexural modulus, Vickers hardness, water sorption, and solubility were evaluated. The main effect plots revealed that the addition of nano-ZrO₂ particles enhances flexural strength, flexural modulus, and water sorption of GICs at a 7 wt% concentration and Vickers hardness at a 2 wt% concentration. The SEM analysis clearly shows that the cracks became narrower with the addition of nano-ZrO₂ particles, whereas these cracks were completely closed at 7% nano-ZrO₂ particles. The findings of the study appear promising, and it is anticipated that the optimization of nano-ZrO₂ particles may aid the development of improved materials for load-bearing restorations. Full article

The synthesis and characterization of MgO-ZrO₂ heterostructures are examined in this work. To promote the creation of nanowires, the Si substrate is first covered with a catalyst layer of various Au thicknesses. Sputtering is used to achieve this deposition. After that, chemical vapor deposition (CVD) with a Au catalyst layer is used to create MgO nanowire arrays on the silicon substrate. Second, MgO/ZrO₂ Core–shell Nanowire Arrays are created by applying ZrO₂ layers to the surface of MgO nanowires of different diameters using chemical vapor deposition (CVD) procedures. The presence of both magnesium oxide (MgO) and zirconium dioxide (ZrO₂) in their oxidized forms was shown by the detailed characterization of the MgO-ZrO₂ core–shell nanowire samples utilizing a variety of methods. Phase formation, mechanical homogeneity, optical characteristics, and topographical structure and roughness were all thoroughly examined at various stresses. MgO hardness values ranged from 1.4 to 3.2 GPa, whereas MgO-ZrO₂ ranged from 0.38 to 1.2 GPa. The I–V parameter study was a further step in the examination of the heterostructure’s electrical properties. The structural, morphological, optical, mechanical, and electrical properties of the MgO-ZrO₂ heterostructure were all thoroughly described using these techniques. Full article

Organophosphorus pesticides (OPs), while pivotal for agricultural productivity, pose severe environmental and health risks due to their persistence and bioaccumulation. Existing detection methods, such as chromatography and spectroscopy, face limitations in field adaptability, cost, and operational complexity. To address these challenges, this study introduces a novel dual-mode photoelectrochemical–electrochemical (PEC-EC) sensor based on a Co,N-TiO₂@ZrO₂/3DGH nanocomposite. The sensor synergistically integrates zirconium oxide (ZrO₂) for selective OP capture via phosphate-Zr coordination, cobalt-nitrogen co-doped titanium dioxide (Co,N-TiO₂) for visible-light responsiveness, and a three-dimensional graphene hydrogel (3DGH) for enhanced conductivity. In the PEC mode under light irradiation, OP adsorption induces charge recombination, yielding a logarithmic photocurrent attenuation with a detection limit of 0.058 ng mL⁻¹. Subsequently, the EC mode via square wave voltammetry (SWV) self-validates the results, achieving a detection limit of 0.716 ng mL⁻¹. The dual-mode system demonstrates exceptional reproducibility, long-term stability, and selectivity against common interferents. Parallel measurements revealed <5% inter-mode discrepancy, validating the intrinsic self-checking capability. This portable platform bridges the gap between laboratory-grade accuracy and field-deployable simplicity, offering transformative potential for environmental monitoring and food safety management. Full article

Solution-processed metal oxide dielectrics often result in unstable thin-film transistor (TFT) performance, hindering the development of next-generation metal oxide electronics. In this study, we prepared fluorine (F)-doped zirconium oxide (ZrO₂) dielectric layers using a chemical solution method to construct TFTs. The characterization by X-ray photoelectron spectroscopy (XPS) revealed that appropriate fluoride doping significantly reduces oxygen vacancies and the concentration of hydroxyl groups, thereby suppressing polarization processes. Subsequently, the electrical properties of Al/F:ZrO₂/n⁺⁺Si capacitors were evaluated, demonstrating that the optimized 10% F:ZrO₂ dielectric exhibits a low leakage current density and stable capacitance across a wide frequency range. Indium zinc oxide (IZO) TFTs incorporating 10% F:ZrO₂ dielectric layers were then fabricated. These devices displayed reliable electrical characteristics, including high mobility over a broad frequency range, reduced dual-sweep hysteresis, and excellent stability under positive-bias stress (PBS) after three months of aging. These findings indicate that the use of the fluorine-doped ZrO₂ dielectric is a versatile strategy for achieving high-performance metal oxide thin-film electronics. Full article

This paper presents an advanced dielectric engineering approach utilizing a composition-dependent hafnium zirconium oxide (Hf_1-xZr_xO₂) superlattice (SL) structure for Si nanosheet gate-all-around field-effect transistors (Si NSGAAFETs). The dielectric (DE) properties of solid solution (SS) and SL Hf_1-xZr_xO₂ capacitors were systematically characterized through capacitance-voltage (C-V) and polarization-voltage (P-V) measurements under varying annealing conditions. A high dielectric constant (k-value) of 59 was achieved in SL-Hf_0.3Zr_0.7O₂, leading to a substantial reduction in equivalent oxide thickness (EOT). Furthermore, the SL-Hf_0.3Zr_0.7O₂ dielectric was integrated into Si NSGAAFETs, with the interfacial layer (IL) further optimized via NH₃ plasma treatment. The resulting devices exhibited superior electrical performance, including an enhanced ON-OFF current ratio (I_ON/I_OFF) reaching 10⁷, an increased drive current, and significantly reduced gate leakage. These results highlight the potential of SL-Hf_0.3Zr_0.7O₂ as a high-k dielectric solution for overcoming EOT scaling challenges in advanced CMOS technology and enabling further innovation in next-generation logic applications. Full article

Polyvinyl alcohol (PVA) is used in various fields; however, its highly flammable property greatly limits its application. In order to improve the flame-retardant properties of PVA, one method is by adding flame retardants directly, while another method is through grafting, cross-linking and hydrogen bonding. A flame retardant, 9, 10-dihydro-9, 10-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-vinyltrimethoxysilane (VTES), was synthesized through the addition reaction of a P–H bond on the DOPO and unsaturated carbon–carbon double bonds on the VTES. Then, the DOPO-VTES and zirconium phosphate (α-ZrP) were blended with PVA to cast a film, in which DOPO-VTES was grafted onto the PVA by cross-linking the hydroxyl group in the molecular structure of DOPO-VTES with the hydroxyl group in PVA; α-ZrP was used as a cooperative agent of DOPO-VTES. The cone calorimetry test (CCT) showed a significant reduction in both the heat release rate (HRR) and total heat release rate (THR) for the flame-retardant PVA films compared to pure PVA. Additionally, thermogravimetric analysis (TGA) revealed a higher residual char content in the flame-retardant PVA films than in pure PVA. These findings suggested that the combination of DOPO-VTES and α-ZrP could improve the flame retardancy of PVA. The cooperative flame-retardant mode of action at play was possibly that DOPO in the DOPO-VTES acted as a mainly gas-phase flame retardant, which yielded a PO radical; VTES in the DOPO-VTES produced silicon dioxide (SiO₂), which acted as a thermal insulator; and α-ZrP catalyzed the carbonization of the PVA. By combining DOPO-VTES with α-ZrP, a continuous dense carbon layer was formed, which effectively inhibited oxygen and heat exchange, resulting in a flame-retardant effect. It is expected that flame-retardant films for PVA have a broad development prospect and potential in the fields of packaging materials, electronic appliances, and lithium-ion battery separators. Full article

Zirconium alloys are essential materials for nuclear fuel cladding. During a loss-of-coolant accident (LOCA), zirconium alloy cladding can oxidize in high-temperature steam (>1000 °C), generating hydrogen and releasing significant heat. Without timely emergency actions, this can result in hydrogen explosions or nuclear leakage. In this study, titanium nitride (TiN), chromium (Cr), and TiN–Cr composite coatings were deposited on the surface of Zr-4 alloy using the magnetron sputtering method. The coatings’ surface and cross-sectional morphologies were examined using scanning electron microscopy (SEM), and their phase structures were analyzed with X-ray diffraction (XRD). The mechanical properties were evaluated using scratch tests, and their resistance to high-temperature steam oxidation was tested in a tube furnace connected to a steam generator. The results showed that the TiN, Cr, and TiN–Cr coatings exhibited strong adhesion to the Zr-4 substrates, with distinct interfaces and pure phase structures. After high-temperature steam oxidation, cracks appeared on the surfaces of the TiN, Cr, and TiN–Cr coatings, likely due to differences in the thermal expansion coefficients of TiO₂, Cr₂O₃, and residual Cr layers. These cracks created pathways for the oxidizing medium, potentially leading to the oxidation of the substrate or inner layers of the composite coatings. For the Cr and TiN–Cr coatings, despite cracking of the Cr layer and melting of the TiN layer at high temperatures, the residual Cr layer effectively restricted oxygen diffusion into the Zr-4 substrate. This study suggests that layers with low melting points, such as TiN, are unsuitable for composite coatings in high-temperature applications. However, adding a Cr layer on top of the TiN layer to form a TiN–Cr composite coating improves adhesion between the coating and the substrate. The TiN–Cr composite coating functions as an effective diffusion barrier at temperatures up to 1200 °C, comparable to a pure Cr coating. Full article

As a type of sustainable and renewable natural source, biomass-derived 5-hydroxymethyl furfural (HMF) can be converted into high-value chemicals. This study investigated the interactions between silver (Ag) and oxide supports with varied reducibility and their contributions to tuning catalytic performance in the selective oxidation of HMF. Three representatives of manganese dioxide (MnO₂), zirconium dioxide (ZrO₂), and silicon dioxide (SiO₂) were selected to support the Ag active sites. The catalysts were characterized by techniques such as STEM (TEM), Raman, XPS, H₂-TPR, and FT-IR spectroscopy to explore the morphology, Ag dispersion, surface properties, and electronic states. The catalytic results demonstrated that MnO₂ with the highest reducibility exhibited superior catalytic performance, achieving 75.4% of HMF conversion and 41.6% of selectivity for 2,5-furandicarboxylic acid (FDCA) at 120 °C. In contrast, ZrO₂ and SiO₂ exhibited limited oxidation capabilities, mainly producing intermediate products like FFCA and/or HMFCA. The oxidation ability of these catalysts was governed by support reducibility, because it determined the density of oxygen vacancies (Ov) and surface hydroxyl groups (O_OH), and eventually influenced the catalytic activity, as demonstrated by the reaction rate: Ag/MnO₂ (3214.5 mol_HMF·g_Ag⁻¹·h⁻¹), Ag/ZrO₂ (2062.3 mol_HMF·g_Ag⁻¹·h⁻¹), and Ag/SiO₂ (1394.4 mol_HMF·g_Ag⁻¹·h⁻¹). These findings provide valuable insights into the rational design of high-performance catalysts for biomass-derived chemical conversion. Full article

The aim of this work was to obtain a protective ZrO₂ coating on diamond particles, which was to protect diamond from oxidation and graphitization, enabling sintering of diamond at higher temperatures and lower pressures than its thermodynamic stability in atmospheric conditions. The coatings were obtained by mixing diamond with zirconium and oxidizing in air or oxygen. Mixtures of diamond and 80 wt% zirconium were sintered by SPS method at temperatures of 1250 °C and 1450 °C. To stabilize the tetragonal structure of ZrO₂, 3 mol% Y₂O₃ was added to zirconium before the milling process. The composition of powder phases, morphology, and microstructures of sintered materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Diffraction studies show the presence of zirconium monoclinic and tetragonal oxides in coatings, after oxidation in air, and in oxygen. Oxidation in oxygen flow is possible for lower temperatures (75 °C), which results in the presence of unreacted zirconium. In ZrO₂ doped with yttria after the oxidation process in oxygen, there is no monoclinic ZrO_2. It is possible to sinter the ZrO₂–diamond composite at 1250 °C using the spark plasma sintering method without graphitization of the diamond. The sintered material consists of monoclinic and tetragonal ZrO₂ structures. Full article