ZrO2 Component Research Articles

Enhanced density and microstructural integrity of binder jetting manufactured ceramics through cold isostatic pressing

Binder jetting (BJ) is a type of additive manufacturing (AM) process that enables fabrication of complex zirconia (ZrO2) ceramic components. However, there are significant challenges in fabricating ceramic parts with high relative density and superior performance. In this study, cold isostatic pressing (CIP) process was integrated into BJ, successfully producing high-performance ZrO2 ceramics. Comprehensive study was conducted on ZrO2 granules, binder, and their interactions. In addition, effects of CIP process on relative density and mechanical properties of sintered samples were investigated. Results indicate that CIP process significantly enhances green body density and reduces spacing between particles, thereby facilitating subsequent densification during ceramic sintering. Moreover, debinding followed by CIP treatment yields superior mechanical properties compared to the methods where CIP was performed prior to debinding, as it prevents defect formation during debinding. Subsequently, differences in performance between ZrO2 ceramics treated with and without CIP were compared at various sintering temperatures. After sintering at 1400 °C, relative density and flexural strength of ZrO2 ceramics reached 98.75 ± 0.19 % and 1047.80 ± 88.45 MPa, representing significant improvements of 53.24 % and 100-fold increase compared to those without CIP treatment, respectively. These findings indicate that proposed method is highly promising for fabrication of high-density and high-performance ZrO2 components.

Study of Structural, Strength, and Thermophysical Properties of Li2+4xZr4−xO3 Ceramics

The work is devoted to the study of technology that can be used to obtain lithium-containing ceramics of the Li2+4xZr4−xO3 type using the method of solid-phase synthesis combined with thermal annealing at a temperature of 1500 °C. A distinctive feature of this work is the preparation of pure Li2ZrO3 ceramics with a high structural ordering degree (more than 88%) and density (95–97% of the theoretical density). During the study, it was found that a change in the content of initial components for synthesis does not lead to the formation of new phase inclusions; however, an increase in the LiClO4·3H2O and ZrO2 components leads to changes in the size of crystallites and dislocation density, which lead to the strengthening of ceramics to external mechanical influences. The results of the measurements of thermophysical characteristics made it possible to establish that the compaction of ceramics and a decrease in porosity lead to an increase in the thermal conductivity coefficient of 3–7%.

High-surface-area mesoporous silica-yttria-zirconia ceramic materials prepared by coprecipitation method ― the role of silicon

A high surface area is one of desired properties for yttria-zirconia (Y2O3–ZrO2) ceramic materials given their catalytic applications. The objective of this study is to develop high-surface-area Y2O3–ZrO2 materials by silicon (Si) modification and investigate the role of Si. Si-modified yttrium-zirconium hydroxides were prepared via a one-step precipitation process and calcined at 800 or 950 °C to form Si-modified Y2O3–ZrO2 (denoted as SiO2–Y2O3–ZrO2) materials containing 0-20 wt% Si as SiO2. These hydroxides or materials were characterized by 29Si NMR, XPS, TG-DSC, XRD, UV Raman, TEM, and N2 physisorption measurements. Si species uniformly distributed in the hydroxides tended to be enriched on the material surface at high temperatures. These Si species dominated by the silicates blocked the migration of Y and Zr atoms, which resisted the crystallite growth of Y2O3–ZrO2 components and reduced their crystallite size. Therefore, the SiO2–Y2O3–ZrO2 possessed a surface area of 59-112 m2/g after calcination at 950 °C for 9 h, which was significantly higher than that of the Y2O3–ZrO2 (23 m2/g). This study may stimulate ideas for developing high-surface-area crystalline ceramic materials calcined at high temperatures.

Influence of electron-beam heating modes on the structure of composite ZrO2-Al2O3 ceramics

The article presents the results of electron beam sintering of composite ceramics based on Al2O3 and ZrO2 powders. Samples were made with different contents of Al2O3 and ZrO2 components and different pressing pressures. Sintering was carried out in vacuum at a helium pressure of 30 Pa. An electron beam generated by a forevacuum plasma electron source was used for sintering. It is shown that the sintering result depends on the pressing pressure and the percentage of components. The influence of the geometry of the samples and their composition on the temperature drop over their volume during sintering has been determined.

Crystallization of discrete ZrO2 polymorph in the amorphous bioglass matrix comprising essential elements

The exceptional biocompatibility of bioglass in amorphous form is well-known; nevertheless, their crystallization to yield auxillary products during elevated heat treatments were considered as a major obstacle to retain specialized features. The excellent mechanical features of crystalline ZrO2 is deliberated as a primary choice in orthopaedic applications. The study aims to hold the well crystallized ZrO2 grains in amorphous bioglass matrix at elevated temperatures devoid of the crystallization of auxiliary products. The choice of elemental composition in bioglass to retain amorphous state in crystallized ZrO2 were explored. Preliminary investigation on the elements choice to design bioglass has been optimized followed by the specific formulation to integrate in ZrO2 component. Subsequently five different bioglass formulations with increment in the element concentrations has been designed and integrated in ZrO2 matrix. The characterization results ensured the impregnation of cubic ZrO2 (c-ZrO2) component in amorphous SiO2 matrix devoid of structural degradation until 1400 °C. The indentation tests accomplished better mechanical features of the resultant compositions that displayed good concurrence with the commercialized ZrO2 products.

Carboxylation of Toluene with CO2‐derived Dimethyl Carbonate over Amorphous Ti−Zr Mixed‐metal Oxide Catalysts

AbstractCarboxylation of arenes utilizing CO2 into value‐added chemicals has received much attention but remains a challenge. Herein, we report a Ti−Zr oxide catalyst which shows high activity in the carboxylation of toluene with CO2‐derived dimethyl carbonate (DMC) into methyl methylbenzoates, while the individual TiO2 and ZrO2 component show poor catalytic performance. It was found that the excellent performance is related to the amorphous state of the Ti−Zr mixed‐metal oxide which possesses high acidity and moderate basicity together with high specific surface area.

Dual Occupancy of Yttrium and Its Impact on the Allotropic and Polymorphic Phase Transitions in the β-Ca3(PO4)2–ZrO2 System

This study aims to attain structurally stable β-Ca3(PO4)2/ZrO2 composites at high temperature. The concentration of Y3+ holds the key to retain stable structures of either β-Ca3(PO4)2/t-ZrO2 or β-Ca3(PO4)2/c-ZrO2 composites. Among the β-Ca3(PO4)2 and ZrO2 structures, Y3+ prefers accommodation at the Ca2+(1), Ca2+(2), and Ca2+(3) sites of β-Ca3(PO4)2 rather than the ZrO2 lattice. Nevertheless, due to the limited occupancy at β-Ca3(PO4)2, the excess Y3+ enters the ZrO2 lattice and stabilizes either t-ZrO2 or c-ZrO2 structures. The concentration of Y3+ in the composite system decides either to induce t- → m-ZrO2 transition or retain t-ZrO2 and c-ZrO2 structures. The atomic level mixing of β-Ca3(PO4)2 and ZrO2 components in the composite is affirmed from transmission electron microscopy analysis. Indentation results ensure the influence of Y3+ content in the mechanical behavior of resultant β-Ca3(PO4)2/ZrO2 composites.

Removal of phosphate from aqueous solution by a novel Mg(OH)2/ZrO2 composite: Adsorption behavior and mechanism

In this work, Mg(OH)2 was incorporated into ZrO2 to obtain a novel Mg(OH)2/ZrO2 composite (MZ) by a simple co-precipitation method for phosphate adsorption. For comparison purpose, pure ZrO2 and Mg(OH)2 were also fabricated. The as-prepared MZ, ZrO2 and Mg(OH)2 were characterized by SEM, EDS, N2 adsorption/desorption and pHPZC, and their phosphate adsorption properties were comparatively investigated in batch mode. The MZ samples before and after phosphate adsorption were characterized by XPS, and the phosphate-adsorbed MZ was characterized by 31P NMR. The results showed that MZ was mainly composed of ZrO2 and Mg(OH)2. In addition, MZ had a larger specific surface area than single-component ZrO2 and Mg(OH)2. MZ exhibited a much higher affinity towards phosphate in aqueous solution than pure ZrO2 and Mg(OH)2. The Langmuir maximum phosphate adsorption capacity of MZ was 87.2 mg PO4/g at initial pH 7, which was 84% and 4.3 times higher than those of single-component ZrO2 and Mg(OH)2, respectively. Phosphate was adsorbed onto the MZ surface mainly via a ligand exchange between the ZrO2 phase and phosphate forming inner-sphere phosphate complexes as well as the reaction between the Mg(OH)2 phase and phosphate forming Mg-P compounds such as MgHPO4 and Mg3(PO4)2. The enhanced phosphate adsorption by the incorporation of Mg(OH)2 into ZrO2 could be attributed to: (i) the increase in the specific surface area of the adsorbent material; and (ii) the enhanced adsorption of phosphate on the ZrO2 component by the presence of Mg2+ that was dissolved from the Mg(OH)2 component. Results of this work indicate that MZ is a more promising adsorbent for the removal of phosphate from wastewater than Mg(OH)2 and ZrO2.

Hydrogen production from methanol steam reforming over Al2O3- and ZrO2-modified CuOZnOGa2O3 catalysts

New CuOZnOxGa2O3–Al2O3 and CuOZnOxGa2O3–ZrO2 (CuZnxGaAl, CuZnxGaZr) catalysts with different Ga contents were prepared and tested in the methanol steam reforming reaction (MSR) under stoichiometric methanol/water = 1 mol ratio (S/C = 1) at 523 K and 548 K. Addition of Al2O3 or ZrO2 components increases the surface area and modifies the reducibility of CuOZnOGa2O3 catalysts; the CuZnxGaZr systems showed the highest reducibility. The performance of CuOZnOGa2O3-based catalysts for MSR is improved by the presence of ZrO2 promoter. CuZn3GaZr catalyst showed a high performance for MSR at 523 K and 548 K under stoichiometric conditions (S/C = 1). The catalyst resulted highly stable and selective for H2 production, with formation of less than 0.3% mol of CO at 523 K. CO is produced as a secondary by-product through the reverse water gas shift reaction. The new catalysts show high resistance to carbon formation at the temperatures analyzed under stoichiometric conditions (S/C = 1).

Unfolding the complexities of mechanical activation assisted alkali leaching of zircon (ZrSiO4)

Sodium hydroxide leaching of non-activated and mechanically activated zircon (ZrSiO4) from Indian beach sands has been investigated. Mechanical activation is carried out up to 480min using a planetary mill. The activated samples were characterised in terms of morphology, particle size distribution and degree of amorphisation. Milling resulted in a significant reduction in median size from 195 to 0.99μm and the degree of amorphisation reached a value of ~90% after about 100min of milling. Leaching was carried out with 2.5–7.5M of NaOH in the temperature range of 35–85°C and a solid to liquid ratio of 1:20 (w/v). Mechanical activation resulted in a 2–4 fold increase in the solubility of ZrO2 and SiO2 components of zircon after 480min milling. Dissolution occurs non-congruently and the nature of dissolution was found to depend on the progress of leaching, temperature and mechanical activation time. The rate of dissolution of ZrO2 component exceeds SiO2 component under all the conditions of leaching. The kinetics of dissolution of both the components can be described in terms of a ‘shrinking core model with film diffusion’, and, depending upon mechanical activation time with the apparent activation energies of 17–41kJ/mol for ZrO2 component and 8–23kJ/mol for SiO2 component. The apparent activation energy for ZrO2 component shows an anomalous increase with an increase in mechanical activation time. The anomaly is explained in terms of opposing dual role of mechanical activation, namely enhanced dissolution due to increased reactivity with a simultaneous greater formation of the inhibiting Si-rich surface film/layer due to non-congruent nature of the dissolution.

Electrocatalytic Enhancement Effects at Platinized Nanoporous Substrates: Oxidation of Ethanol at PtRu Nanoparticles Dispersed over Rh-Containing ZrO2 Support

The presence of a large population of hydroxyl groups (originating from zirconia) in the vicinity of PtRu, in addition to possible specific interactions between zirconia and the ruthenium component, most likely induced oxidative removal (from Pt) of otherwise passivating CO adsorbates. Although Rh itself did not show directly any activity toward the ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH molecule. Codeposition and introduction of metallic rhodium particles to ZrO2 also improved the overall conductivity of the matrix and charge distribution at the electrocatalytic interface. Application of the nanoporous platinum electrode substrate together with Rh and ZrO2 components as well as PtRu electrocatalytic sites led to enhancement of the electrocatalytic currents larger than one would expect from simple addition of activities of single components.

Reaction mechanism of MgO–ZrO2 refractory with CaO–SiO2–Al2O3–FetO slag

In order to understand the reaction mechanism of MgO–ZrO2 refractory with molten slag and to expand the application of MgO–ZrO2 refractory, the reaction process of MgO–ZrO2 refractory with CaO–SiO2–Al2O3–FetO slag was investigated and the mechanism of corrosion resistance was discussed. Results showed that the CaO–SiO2–Al2O3–FetO slag first penetrated into the MgO–ZrO2 refractory and reacted with MgO and ZrO2 components to form Mg(Al, Fe)2O4 and CaZrO3, respectively, decreasing the open porosity of the refractory and forming a dense layer, which could prevent the penetration of the molten slag into the MgO–ZrO2 refractory. Meanwhile, the viscosity of the molten slag in the refractory was increased, leading to the decrease in the penetration ability. Because of the reaction between the MgO–ZrO2 refractory and the CaO–SiO2–Al2O3–FetO slag, the slag corrosion resistance of the MgO–ZrO2 refractory was improved. Compared with the MgO–Cr2O3 refractory, the corrosion parameter and penetration parameter of the MgO–ZrO2 refractory after reaction with slag are only 4·9% and 17·0%, respectively.

Hydrothermal Synthesis, Luminescence, and Phase Stability of Solid Solution Nanocrystals Based on Y3NbO7 and ZrO2

Cubic solid solution nanocrystals in the zirconia (ZrO2)–yttrium niobate (Y3NbO7) system were directly formed at 180°C–240°C from the precursor solution mixtures of NbCl5, ZrOCl2, and YCl3 under mild hydrothermal conditions in the presence of aqueous ammonia. The lattice parameter corresponding to cubic phase linearly changed according to the Vegard's law in the wide composition range of ZrO2 (mol%) = 10–90 in the ZrO2–1/4Y3NbO7 system. The progress of the formation of nanocrystalline solid solutions based on the Y3NbO7 was assisted via the presence of ZrO2 component as a promoter with the same fluorite‐type structure. The optical band gap of the solid solutions was in the range 3.4–3.7 eV. Broadband emissions centered at 360–380 and 390 nm were observed for the nanocrystalline cubic solid solutions and pure cubic Y3NbO7, respectively, under excitation at 240 nm Xe lamp. The nanosized cubic crystallites of the solid solutions were maintained after heat treatment up to 800°C for 1 h air. The cubic phase of the solid solutions in the ZrO2–1/4Y3NbO7 system was maintained after heat treatment at 1400°C in air.

The relationship between the structure and catalytic performance Cu/ZnO/ZrO2 catalysts for hydrogenation of dimethyl 1,4-cyclohexane dicarboxylate

The gas-phase hydrogenation of dimethyl 1,4-cyclohexane dicarboxylate to 1,4-cyclohexane dimethanol (CHDM) was conducted on well-dispersed supported Cu/ZnO/ZrO2 catalysts. The results indicated that the structure and catalytic performance of resulting copper-based catalysts were profoundly affected by the addition of zirconium. Moreover, the as-synthesized catalyst with 35.0 wt.% ZrO2 component was found to exhibit superior catalytic performance with a high CHDM yield of 96.8% to other catalysts, which should be mainly attributed to the significant dispersion effect of ZrO2 on the copper-containing species resulting in a higher metallic copper surface area as well as a larger number of Cu+ species.

Integrated DeNO x –DeSoot Catalytic Systems with Improved Low-Temperature Performance

Performance of the combined catalysts [CeO2–ZrO2 + FeBETA] and [Mn/CeO2–ZrO2 + FeBETA], prepared by mechanical mixing of the component powders, was studied in soot oxidation and NH3-SCR. [CeO2–ZrO2 + FeBETA] catalyst (with component volumetric ratio of 3/1) demonstrated efficient soot oxidation at 400–450 °C and DeNOx performance similar to that of FeBETA catalyst, despite the fact that the amount of zeolite was reduced by four times indicating a strong synergistic effect between the components. Low-temperature DeNOx performance of the [CeO2–ZrO2 + FeBETA] system can be additionally enhanced by doping the CeO2–ZrO2 with Mn. It was found that NOx conversion over [Mn/CeO2–ZrO2 + FeBETA] at 150–250 °C was steadily improved by increasing the Mn loading, and [5.4 % Mn/CeO2–ZrO2 + FeBETA] attained NOx conversion above 90 % at Treact ~190 °C. Comparative studies of soot oxidation and NH3-SCR over combined catalysts and individual components indicated that the soot oxidation activity is assigned to the soot oxidation over ceria–zirconia component, while enhanced low-temperature SCR performance is a result of a “bi-functional” SCR mechanism comprising NO oxidation to NO2 over CeO2–ZrO2 component followed by fast-SCR over FeBETA.

ZrNO–Ag co-sputtered surfaces leading to E. coli inactivation under actinic light: Evidence for the oligodynamic effect

This study reports visible light sensitive ZrNO and ZrNO–Ag polyester samples prepared by sputtering in an Ar/N2/O2 atmosphere leading to Escherichia coli bacterial inactivation. The bacterial inactivation by ZrNO avoids the increasing environmental concern involving the fate of Ag-leaching of many disinfectants. The simultaneous co-sputtering of ZrNO and Ag2O enhanced the E. coli bacterial inactivation kinetics compared to the sequential sputtering of ZrNO and Ag. A reaction mechanism is suggested triggered by photoinduced interfacial charge transfer (IFCT) suggesting electron injection form the Ag2Ocb to the ZrO2cb. The sizes of the ZrO2 and Ag nanoparticles in the co-sputtered ZrNO–Ag were 80–130nm and 8–15nm respectively as determined by high angular annular dark field (HAADF) microscopy. Evidence is presented by X-ray photoelectron spectroscopy (XPS) for the self-cleaning of the photocatalysts after bacterial inactivation. This enabled a stable catalyst reuse. The XPS experimental spectra of ZrNO and ZrNO–Ag were deconvoluted into their ZrN, ZrNO and ZrO2 components. The amounts of Ag-ions released during bacterial inactivation were<5ppb/cm2 and well below the Ag cytotoxic levels. Since no cytotoxicity was introduced during the bacterial inactivation process, the ZrNO–Ag disinfection proceeds through an oligodynamic effect.

Intramolecular selective hydrogenation of cinnamaldehyde over CeO2–ZrO2-supported Pt catalysts

Selective liquid phase hydrogenation of cinnamaldehyde is reported, for the first time, over CeO2, ZrO2, and CeO2–ZrO2-supported Pt catalysts. Cinnamyl alcohol is the selective product. These catalysts are highly active and selective even at 25°C and found to be superior to most of the hitherto known supported Pt catalysts. Alkali addition (NaOH) has enhanced the performance of these catalysts. At an optimized reaction condition, 95.8% conversion of cinnamaldehyde and 93.4% selectivity of cinnamyl alcohol have been obtained. Acidity of the support (due to the presence of ZrO2 component) and higher electron density at Pt (due to CeO2 component) are attributed to be responsible for the superior catalytic activity of Pt supported on CeO2–ZrO2 composite material.

The role of CeO2–ZrO2 distribution on the Ni/MgAl2O4 catalyst during the combined steam and CO2 reforming of methane

The effect of the distribution of CeO2–ZrO2 on Ni/MgAl2O4 catalyst on the catalytic performance during the combined steam and carbon dioxide reforming of CH4 (CSCR) was investigated on two different catalysts prepared using a sequential impregnation and co-precipitation of Ni and CeO2–ZrO2 components. The CeO2–ZrO2 plays an important role in the CO2 conversion by enhancing a facile activation of CO2 with an adjacent contact with nickel crystallites. The CSCR catalysts prepared by the co-precipitation of nickel and CeO2–ZrO2 on MgAl2O4 support shows a catalytic activity superior to the catalyst prepared by sequential impregnation of nickel on the MgAl2O4 support with CeO2–ZrO2 due to the homogeneous distribution of CeO2–ZrO2 with the formation of small nickel crystallites and a large amount of active sites for CO2 adsorption.

Phase transformation in the surface region of zirconia and doped zirconia detected by UV Raman spectroscopy

The phase evolution of yttrium oxide and lanthanum oxide doped zirconia (Y2O3–ZrO2 and La2O3–ZrO2, respectively) from their tetragonal to monoclinic phase has been studied using UV Raman spectroscopy, visible Raman spectroscopy and XRD. UV Raman spectroscopy is found to be more sensitive at the surface region while visible Raman spectroscopy and XRD mainly give the bulk information. For Y2O3–ZrO2 and La2O3–ZrO2, the transformation of the bulk phase from the tetragonal to the monoclinic is significantly retarded by the presence of yttrium oxide and lanthanum oxide. However, the tetragonal phase in the surface region is difficult to stabilize, particularly when the stabilizer’s content is low. The phase in the surface region can be more effectively stabilized by lanthanum oxide than yttrium oxide even though zirconia seemed to provide more enrichment in the surface region of the La2O3–ZrO2 sample than the Y2O3–ZrO2 sample, based on XPS analysis. The surface structural tension and the enrichment of the ZrO2 component in the surface region of ZrO2–Y2O3 and ZrO2–La2O3 might be the reasons for the striking difference between the phase change in the surface region and the bulk. Accordingly, the stabilized tetragonal surface region can significantly prevent the phase transition from developing into the bulk when the stabilizer’s content is high.

Comparison of deposition behavior of Pb(Zr,Ti)O3 films and its end-member-oxide films prepared by MOCVD

Pb(Zr,Ti)O3(PZT) and end-member single oxide, PbO, ZrO2 and TiO2, films were deposited by metalorganic chemical vapor deposition (MOCVD) from Pb(C11H19O2)2–Zr(O·t-C4H9)4–Ti(O·i-C3H7)4-O2 system, Pb(C11H19O2)2-O2 system, Zr(O·t-C4H9)4-O2 system and Ti(O·i-C3H7)4-O2 system, respectively. The deposition rates of PbO, TiO2 and ZrO2 components in PZT films were investigated as a function of the deposition temperature. The deposition rates of each components in PZT films were quite different from those of PbO, ZrO2 and TiO2 films. However, the deposition temperature dependencies of the deposition rates of TiO2 and ZrO2 components in PZT films were almost the same. This resulted in that the Zr/(Zr+Ti) in the film was almost independent of the deposition temperature. On the other hand, the deposition temperature dependency of the deposition rate of PbO component in PZT film was different from those of ZrO2 and TiO2 components. This resulted in that Pb/(Pb+Zr+Ti) in PZT film depended on the deposition temperature. The deposition temperature dependencies of PbO and TiO2 components in PbTiO3 film were not the same and Pb/(Pb+Ti) in PbTiO3 films also depended on the deposition temperature.