Porous ZrO2 Research Articles

Exploring the influence of sintering temperature on the phase composition, mechanical strength, and dielectric constant of porous ca-stabilized zirconium dioxide ceramics

ZrO2 ceramics have wide applications as structural materials in industrial, scientific, and technological fields. Despite the large number of works devoted to the influence of synthesis parameters on the formation of different phases of ZrO2 and the properties of the obtained ceramics, the effect of sintering temperature on the characteristics of the porous ZrO2 ceramics has not been addressed sufficiently. This study focuses on examining how sintering temperature affects the phase composition, microstructure, dielectric properties, and mechanical properties of porous stabilized zirconium dioxide ceramics. Phase transformations during sintering at various temperatures were identified using powder X-ray diffraction and Raman spectroscopy. The results indicate that fully stabilized cubic ZrO2 with satisfactory mechanical properties (HV0.5 = 580) and a porosity of 21.5% was achieved at temperatures of 1400 and 1500 ℃. At lower sintering temperatures, the obtained samples exhibited multiphase composition and high porosity. The reasons for the formation of the CaZrO3 phase at sintering temperatures of 1000–1200 ℃ were established using scanning electron microscopy, energy dispersive analysis, and thermodynamic considerations of the solid-phase reactions. AC dielectric measurements showed that the synthesized samples have high-Q characteristics; and that the dielectric constant can be controlled by changing the sintering temperature.

Achieving high-strength, high-porosity and relatively low-shrinkage in extrusion-based 3D printed ZrO2 ceramics by adjusting CaCO3 addition and sintering temperature

High-strength, high-porosity and relatively low-shrinkage ZrO2 ceramics were successfully fabricated by material extrusion 3D printing technology via optimizing CaCO3 addition and sintering temperature. The effects of different CaCO3 additions on the performance, phase formation, and microstructure of porous ZrO2 ceramics sintered at different temperatures were systematically investigated and discussed. The results showed that flexural strength, porosity and shrinkage of the ZrO2 ceramics were significantly affected by CaCO3 addition and sintering temperature. The appropriate addition of CaCO3 could promote sintering and phase transformation of m-ZrO2, increase the number and size of pores in the matrix. The corresponding flexural strength and porosity of the sintered samples increased, while the shrinkage rate decreased. The raised sintering temperature appropriately facilitated the formation of CaZrO3. Microstructural analysis indicated that CaZrO3 exhibited a larger polyhedral bulk morphology, mainly distributed at the edges of pores, which could stabilize the pore structure and thicken the sintering necks, and thereby exhibiting well-balanced comprehensive performance. The ZrO2 ceramics with high flexural strength, high porosity and relatively low shrinkage rate were achieved by adding 15 wt% CaCO3 and sintering at 1450 ℃. The resulting flexural strength and porosity were 27.33 MPa and 67.62 %, respectively, presenting an improvement of 563.35 % and 13.69 % compared to ZrO2 ceramics without CaCO3. Moreover, the shrinkage rates in the X-direction (9.98 %), Y-direction (9.62 %), and Z-direction (9.94 %) significantly reduced, decreasing by 38.28 %, 38.10 %, and 41.46 %, respectively.

Effect of porous irregular ZrO2 nanoparticles on the performance of alkaline water electrolysis composite separator membranes under complex conditions

Developing composite separator membranes with low area resistance, high bubble point pressure, and long-term safety and stability is crucial for alkaline water electrolysis for hydrogen production as a key component of electrolyzer systems. In this study, PPS mesh fabric reinforced PSF@ZrO2 composite separator membranes were successfully prepared using the immersion-drawing phase inversion method, with PSF as the alkali-resistant polymer matrix and porous irregular ZrO2 nanoparticles as the hydrophilic additive. The experimental results showed that replacing commercial ZrO2 with porous irregular ZrO2 nanoparticles at an 85 wt% ZrO2 nanoparticle loading improved both bubble point pressure and current transmission efficiency, attributed to the change in the morphological structure of the ZrO2 nanoparticles. The P-Z85 composite separator membrane exhibited highly promising characteristics, with a high bubble point pressure of 3.76 bar and a low area resistance of 0.20 Ω cm2. Stability tests conducted in 30 wt% KOH electrolyte at 80 °C and a current density of 0.65 A cm−2 demonstrated excellent continuous electrolysis stability for the P-Z85 composite separator membrane. These results indicate that the PSF@ZrO2/PPS composite separator membrane prepared in this study exhibits excellent performance in 30 wt% KOH electrolyte, significantly extending its service life.

Micro-arc driven porous ZrO2 coating for tailoring surface properties of titanium for dental implants application

Titanium (Ti) is an ideal material for dental implants due to its excellent properties. However, corrosion and mechanical wear lead to Ti ions and particles release, triggering inflammatory responses and bone resorption. To overcome these challenges, surface modification techniques are used, including micro-arc oxidation (MAO). MAO creates adherent, porous coatings on Ti implants with diverse chemical compositions. In this context, zirconia element stands out in its wear and corrosion properties associated with low friction and chemical stability. Therefore, we investigated the impact of adding zirconium oxide (ZrO2) to Ti surfaces through MAO, aiming for improved electrochemical and mechanical properties. Additionally, the antimicrobial and modulatory potentials, cytocompatibility, and proteomic profile of surfaces were investigated. Ti discs were divided into four groups: machined – control (cpTi), treated by MAO with 0.04 M KOH – control (KOH), and two experimental groups incorporating ZrO2 at concentrations of 0.04 M and 0.08 M, composing the KOH@Zr4 and KOH@Zr8 groups. KOH@Zr8 showed higher surface porosity and roughness, even distribution of zirconia, formation of crystalline phases like ZrTiO4, and hydrophilicity. ZrO2 groups showed better mechanical performance including higher hardness values, lower wear area and mass loss, and higher friction coefficient under tribological conditions. The formation of a more compact oxide layer was observed, which favors the electrochemical stability of ZrO2 surfaces. Besides not inducing greater biofilm formation, ZrO2 surfaces reduced the load of pathogenic bacteria evidenced by the DNA-DNA checkerboard analysis. ZrO2 surfaces were cytocompatible with pre-osteoblastic cells. The saliva proteomic profile, evaluated by liquid chromatography coupled with tandem mass spectrometry, was slightly changed by zirconia, with more proteins adsorbed. KOH@Zr8 group notably absorbed proteins crucial for implant biological responses, like albumin and fibronectin. Incorporating ZrO2 improved the mechanical and electrochemical behavior of Ti surfaces, as well as modulated biofilm composition and provided suitable biological responses.

Preparation of CS coated graded ordered porous ZrO2 implantable drug carrier

ZrO2 is bioceramic known for its excellent chemical stability and biocompatibility. Porous ZrO2, with its large surface area, has attracted considerable attention in the field of orthopedic implant drug delivery. However, the shortcomings of poor bioactivity and insufficient drug loading capacity in traditionally prepared porous ZrO2 limit its application. In this paper, graded ordered porous ZrO2 with interconnected open pores was prepared by colloid crystal templating, which exhibited large specific surface area and excellent slow-release properties. Then, it was surface-coated with chitosan (CS) possessing bioactivity and strong adsorption capacity. Factors affecting microscopic morphology, drug loading and slow-release properties of this composite were systematically investigated using ibuprofen (IBU) as a drug model. Results showed that graded ordered porous ZrO2 significantly enhanced drug loading capacity compared to normal ordered porous ZrO2, reaching 125.66 mg/g. Additionally, surface coating modification of the composite by CS significantly affected IBU loading capacity. By regulating process parameters such as CS concentration and coating time, high-efficiency loading of IBU was realized and drug loading capacity reached up to 194.17 mg/g. In vitro drug simulation experiments showed that CS coating effectively controlled the initial burst release of IBU and prolonged the effective release time; maximum cumulative release rate reached 93.7 %. This study provides a new idea for implantable drug sustained-release systems, which may better meet medical needs.

Effect of Pore Size on the Mechanical Properties and Deformation Behavior of Porous ZrO2 (Y2O3) Ceramics Under Axial Compression

Effect of Pore Size on the Mechanical Properties and Deformation Behavior of Porous ZrO2 (Y2O3) Ceramics Under Axial Compression

High temperature oxidation behavior of Mo-Zr alloys in pure oxygen condition

In the current study, alloys of Mo-95Zr, Mo-80Zr, Mo-50Zr, Mo-35Zr, Mo-20Zr and Mo-3Zr (at. %) were prepared to investigate the microstructure and oxidation behaviors of the whole composition range of Mo-Zr as-cast alloys. Laves, (Zr) and/or (Mo) intermetallic phases were presented in the primary dendrite, eutectic or peritectic structures in the prepared alloys. The isothermal oxidation process was accompanied by the formation of multi-layer, consisting of the porous and loose ZrO2 and MoO3, which was individually changed from the (Zr), Laves and (Mo). The specimens were examined using a combination of gravimetry and several surface-analytical techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and electron microprobe. Phases composition on the microstructure and oxidation behavior, and the sources of internal stress and defects formation in oxide layer on these alloys during oxidation have been discussed.

Hafnium oxide coating to improve the oxidation behavior of Zirconium Diboride

Hafnium dioxide (HfO2) coatings were successfully deposited on zirconium diboride (ZrB2) using reactive magnetron sputtering. After the oxidation at 1500°C or 1600°C, the mutual dissolution of HfO2 and thermally grown ZrO2 was observed which has resulted in the formation of a mixed oxide zone. As the enrichment of the mixed oxide zone by ZrO2 progresses, monoclinic/tetragonal phase transition temperature of ∼1790°C for nominally pure HfO2 moves towards ∼1500 °C. Finally, the inevitable phase transition from monoclinic to tetragonal structure results in the development of cracks, pores, and gaps within the mixed oxide zone. Thickness measurements of the porous ZrO2 scale and the mixed oxide zone of coated specimens revealed an improvent in the oxidation behavior at 1500°C and 1600°C compared to uncoated ZrB2, proving its protective character for short duration oxidation.

Production of Porous ZrO2–TiO2 Ceramic Coatings on the Biomedical Ti-6Al-4V Alloy via AC PEO Treatment and Their Effects on the Corrosion Behavior in 0.9% NaCl

Production of Porous ZrO2–TiO2 Ceramic Coatings on the Biomedical Ti-6Al-4V Alloy via AC PEO Treatment and Their Effects on the Corrosion Behavior in 0.9% NaCl

Laser ablation behavior and mechanisms of 3D carbon fiber reinforced ZrB2-SiC composite

The high-performance 3D Cf-PyC/ZrB2-SiC composite was fabricated by vibration-assisted slurry impregnation and low-temperature hot pressing. The composite exhibited superior laser ablation resistance, leading to a low linear loss rate of 1.56×10−2 mm/s at laser power density of 4878 W/cm2 (Power 300 W, Laser beam diameter 2.8 mm) for 90 s. The coupling effect of a dense SiO2 layer in fringe region followed by dense ZrO2 layer in transitional region and next porous ZrO2 layer in center region achieved superior laser ablation resistance.

Effect of Pore Size on the Mechanical Properties and Deformation Behavior of Porous ZrO2(Y2O3) Ceramics Under Axial Compression

Effect of Pore Size on the Mechanical Properties and Deformation Behavior of Porous ZrO2(Y2O3) Ceramics Under Axial Compression

Porous ZrO2–ZrO2 ceramics with excellent mechanical strength and permeability for transpiration cooling

AbstractThe great development of transpiration cooling technology challenges the coolant medium seriously. In this paper, porous ZrO2–ZrO2 ceramics have been satisfactorily prepared to meet the requirements of the coolant medium in transpiration cooling. The results illustrate that porous ZrO2–ZrO2 ceramics have excellent compressive strengths; meanwhile, percentages of compressive strength difference (parallel and perpendicular to the mold‐pressing direction) have an upward trend due to the increasing fiber contents. Besides, the failure mode has a huge distinction between parallelity (45° oblique section) and perpendicularity (wedge shape). These ceramics have unimodal pore size distribution (2–10 µm), and their wettability has a substantial improvement reflected by contact angle from 118° to 0°. Permeability behavior across these ceramics has been accurately described using the Darcy–Forchheimer equation, while obtaining viscous and inertial resistance coefficients, respectively. This work can provide an essential reference for coolant medium in transpiration cooling.

Enhanced Oxidation Resistance of ZrB2–SiC–WC Composite below 1800 °C

The effect of 3.6 vol% WC addition to ZrB2–20 vol% SiC (ZSW) on oxidation resistance is studied over a broad range of oxidation temperatures, 1000–1800 °C. Non‐WC‐containing samples (ZS) show significant surface damage and degradation during oxidation, losing protective B2O3 and SiO2‐based surface layers and exposing a porous ZrO2 layer and base material for further oxidation. ZSW samples preserve their surface protective layers during oxidation up to 1800 °C while the underlying ZrO2 scale remains dense. The appearance of convection cells on the surface of ZSW samples during oxidation above 1600 °C is reported. This confirms the presence of boron‐rich phases, suppressing oxygen permeation into the material and enhancing oxidation resistance of ZSW samples. During exposure of the samples to 1800 °C for 15 min, ZS and ZSW samples gain 11.1 ± 1.5 and 7.8 ± 0.3 mg cm−2, respectively, due to oxidation. Exposure of the composites for 5 h at 1600 °C results in weight gains of 10.5 and 7.0 mg cm−2 for ZS and ZSW samples, respectively. Cross sections of oxidized samples at 1800 °C show a tight zirconia layer below a glassy surface in ZSW and complete loss of surface glass in ZS, demonstrating the effectiveness of WC addition.

Contribution of micropores in porous zirconia spheres to high optical transparency of dental resin composites.

Transparency to UV-Vis light and radiopacity of dental resin composites containing zirconia (ZrO2) fillers were investigated. The transparency of the resin composite containing porous ZrO2 spheres was much higher than that containing irregularly shaped ZrO2 particles. Calcination of the porous ZrO2 spheres at high temperatures led to dramatically reduced specific surface areas and pore volumes. The transparency of the resin composite containing the calcined porous ZrO2 spheres drastically decreased as the calcination temperature increased. Then, the enhanced UV-Vis transmittance of the resin composite containing porous ZrO2 spheres is attributed to the concentration and physical characteristics of the pores. The radiopacity of the resin composites containing porous ZrO2 spheres increased slightly with increasing calcination temperature. This study revealed that the internal structure of the ZrO2 fillers mainly influenced in the UV-Vis light transmittance of the resin composites.

Preparation and resistive switching properties of ZrO2 films with large room-temperature ferromagnetism

In this study, ordered porous ZrO2 films were prepared on porous Al2O3 films by magnetron sputtering. The films showed large room-temperature ferromagnetism, and it was also observed that the porous ZrO2 films have magnetic anisotropy. The magnetism in the direction perpendicular to the film surface was much greater than in the direction parallel to the film surface. A saturation magnetization value which was up to 3.19 × 10−4 emu was obtained for the ZrO2 film with pores of 42.55 nm in diameter when the external field was perpendicular to the film surface. The saturation magnetization strength per unit volume is 509.26 emu/cm3. After a photoluminescence (PL) spectrum and X-ray photoelectron spectroscopy (XPS) test on the film, it was found that oxygen vacancy content has a direct effect on the film’s magnetism. In addition, some Ag/ZrO2/PAA/Al devices were prepared, and the resistive switching properties of the ZrO2 films were tested. The research in this paper provides ideas for the development of spintronic devices.

Design of porous ZrO2 with well-tuned band structures and strong visible-light harvesting via Zn doping for enhanced visible-light photocatalysis

As one of huge-gap semiconductors, zirconium dioxide (ZrO2) has been emerging as one of popular photocatalysts for treating wastewater, and the band gap engineering of ZrO2 for efficient visible-light harvesting and high-performance photocatalysis is probably the most important challenge. In this work, porous Zn doped Zr3+-ZrO2 nanostructures with strong visible-light harvesting capacity were fabricated via a calcination process for tetracycline degradation. The obtained (Zn, Zr3+)-ZrO2 samples showed greatly narrowed band gaps and enhanced visible-light harvesting capacity. In addition, the photocatalytic performance of the (Zn, Zr3+)-ZrO2 nanostructures was studied with tetracycline degradation as a model reaction. Among these prepared samples, the optimal (Zn, Zr3+)-ZrO2-5% sample exhibited remarkably improved tetracycline degradation visible-light irradiation, and the apparent rate constant reached 0.04958 min−1, which was 7.05 times of pristine Zr3+-ZrO2. The boosted photocatalytic performance of the (Zn, Zr3+)-ZrO2 nanostructures were mainly ascribed to Zn doping effects as along as the high surface areas. Finally, possible photocatalytic mechanism, degradation pathways, and toxicity assessment were also studied. Current results indicate the significant roles of Zn doping in regulation of band gaps and morphology control of ZrO2 for high-performance photocatalytic applications.

Strong metal-support interaction between AuPd nanoparticles and oxygen-rich defect ZrO2 for enhanced catalytic 5-hydroxymethylfurfural oxidation

The unique properties of metal oxide surfaces, crystal surfaces and defects play vital roles in biomass upgrading reactions. In this work, hierarchical porous bowl-shaped ZrO2 (HB-ZrO2) with mixed crystal phase was designed and employed as the support for loading AuPd bimetal with different proportions to synthesize AuPd/HB-ZrO2 catalysts. The effects of surface chemistry, oxygen defects, bimetal interaction and metal-support interaction of AuPd/HB-ZrO2 on catalytic performance for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) were systematically investigated. The Au2Pd1/HB-ZrO2 catalyst afforded a satisfactory FDCA yield of 99.9% from HMF oxidation using O2 as the oxidant in water, accompanied with an excellent FDCA productivity at 97.6 mmol g−1 h−1. This work offers fresh insights into rationally designing efficient catalysts with oxygen-rich defects for the catalytic upgrading of biomass platform chemicals.

A Combined Gas and Water Permeances Method for Revealing the Deposition Morphology of GO Grafting on Ceramic Membranes.

The adhesion enhancement of a graphene oxide (GO) layer on porous ceramic substrates is a crucial step towards developing a high-performance membrane for many applications. In this work, we have achieved the chemical anchoring of GO layers on custom-made macroporous disks, fabricated in the lab by pressing α-Al2O3 powder. To this end, three different linkers, polydopamine (PDA), 3-Glycidoxypropyltrimethoxysilane (GPTMS) and (3-Aminopropyl) triethoxysilane (APTMS), were elaborated for their capacity to tightly bind the GO laminate on the ceramic membrane surface. The same procedure was replicated on cylindrical porous commercial ZrO2 substrates because of their potentiality for applications on a large scale. The gas permeance properties of the membranes were studied using helium at 25 °C as a probe molecule and further scrutinized in conjunction with water permeance results. Measurements with helium at 25 °C were chosen to avoid gas adsorption and surface diffusion mechanisms. This approach allowed us to draw conclusions on the deposition morphology of the GO sheets on the ceramic support, the mode of chemical bonding with the linker and the stability of the deposited GO laminate. Specifically, considering that He permeance is mostly affected by the pore structural characteristics, an estimation was initially made of the relative change in the pore size of the developed membranes compared to the bare substrate. This was achieved by interpreting the results via the Knudsen equation, which describes the gas permeance as being analogous to the third power of the pore radius. Subsequently, the calculated relative change in the pore size was inserted into the Hagen-Poiseuille equation to predict the respective water permeance ratio of the GO membranes to the bare substrate. The reason that the experimental water permeance values may deviate from the predicted ones is related to the different surface chemistry, i.e., the hydrophilicity or hydrophobicity that the composite membranes acquire after the chemical modification. Various characterization techniques were applied to study the morphological and physicochemical properties of the materials, like FESEM, XRD, DLS and Contact Angle.

The synergetic enhancement of the porous ZrO2@TiO2 heterostructure and the plasmonic silver nanoparticles for efficient surface‐enhanced Raman scattering

Rapid identification and analysis of pesticide residue on real‐world sample by a portable platform is of growing interest for monitoring food safety and safeguarding human health. Herein, we developed a robust surface‐enhanced Raman spectroscopy (SERS) sensor based on ZrO2@TiO2/Ag substrate for the analysis of pesticide residues. The synergetic effects of the metal organic framework (MOF)‐derived porous ZrO2@TiO2 heterostructure induced charge transfer enhancement and the electromagnetic enhancement from the plasmonic silver nanoparticles (AgNPs) hotspot generate significant SERS enhancement signal. The SERS substrate exhibits superior long‐term stability and signal homogeneity for SERS quantitative analysis. The platform has the capability to detect not only model molecule of 4‐ATP but also pesticides of triazophos and fonofos at the extremely low concentration of 10−8 M. Moreover, we simulate the quantitative detection of pesticide residue on real objects by spraying pesticides on dendrobium and chrysanthemum leaves, followed by transferring to the SERS platform to perform analysis. The nearly linear fitting curve with a wide concentration range suggests the superior qualitative detection capability. Remarkably, two components and three components of the pesticides are readily identified in a rapid way. The approach provides the rapid analysis, low‐cost device, and portable and quantitative pesticide identification and offers a clear path to multicomponent analysis at a trace level.

Bioactive porous ZrO2-based ceramics with a hierarchical porosity for artificial bone scaffolds

Given the pressing clinical need, the market for artificial bone scaffolds in orthopedics is growing at a rapid rate. In the past, ZrO2-based biomaterials intended for implantation were dense and ‘bio-inert’. Material scientists have now shifted toward the design of deliberately porous and ‘bioactive’ ZrO2-based biomaterials that integrate with human cells and tissues. In this study, we designed and prepared porous and bioactive ZrO2–SiO2 nanocrystalline ceramics. The phase composition, microstructure, pore formation mechanism, and ion release behaviors of the ceramics were explored. The ceramics showed a hierarchical porosity, consisting of connected macropores (∼100 μm or larger) and micropores (∼1 μm). The spherical macropores were formed by a pore-forming agent method, and the irregular micropores were formed because of incomplete densification. The bioactive dopants (Ca and Sr) acted as a destabilizer of tetragonal ZrO2. Ca, Si, and Sr ions continuously released from the surface of the samples, providing good bioactivity for the ceramics. The porous and bioactive ceramics show great potential to be used as artificial bone scaffolds.