t-ZrO2 Nanoparticles Research Articles

Stabilization of zirconia nanoparticles by collagen protein and calcium carbonate extracted from eggshell and its biodegradation, radical scavenging and mineralization activity

In this current study,collagen protein extracted from eggshell membrane and calcium carbonate (a main component of eggshell) are used as additive to enhance the stability and hardness of the zirconia crystals. Five different samples are prepared by adding membrane containing eggshell content as, 1 g, 2 g, 3 g, 4 g and 5 g in aqueous zirconium oxychloride sol. Phase purity is confirmed by XRD and FTIR. Phase pure and dense particles divulges the high hardness (∼1389 HV) and fracture toughness (12.89 MPa m1/2).FESEManalysis illustrates the formation of dense, well separated, non-agglomerated and spherical nanoparticles at 5 g of eggshell content. Eggshell works as a surfactant and stabilizer for formation of phase pure tetragonal spherical nanoparticles. Biodegradation study of optimized tetragonal zirconia (t-ZrO2)in phosphate buffered saline (PBS) presents that minor change in weight and hardness after 72 h of immersion. Antioxidant study shows the 96% of radical scavenging activity (RSA). In vitro bio-mineralization study shows the formation of new bone after 5 weeks. After 5 weeks all pores were filled and minerals were deposited on the surface of the scaffolds. SEM images confirms that eggshell-zirconia composite form new bone. So eggshell addition results in formation of phase pure t-ZrO2 nanoparticles with well-defined boundaries which exhibit higher hardness, fracture toughness, stability and enhanced antioxidant properties.

Modified carbon paste ion selective electrode for determining Cr(iii) ions in aqueous solutions and some real samples using tetragonal zirconia nanoparticles.

Tetragonal zirconia (t-ZrO2) nanoparticles (ionophore) are used in newly designed and improved ion selective electrodes for chromium ion detection as an alternative, low-cost, high-precision, and selectivity method. Tetragonal zirconia nanoparticles were synthesized using a modified co-precipitation technique and calcined at 1000 °C for an hour. The phase composition, surface area, microstructure, pore size and particle size of synthesized t-ZrO2 nanoparticles were examined using the X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscope (TEM) and scanning electron microscopy (SEM) attached with an EDAX unit, respectively. Results from XRD showed that the t-zirconia was synthesized and have nanocrystallites size about 20.2 nm. The nano size of t-ZrO2 was confirmed by the SEM and TEM (the particle size between 26.48 and 40.4 nm), the mesoporous character (average pore size about 4.868 nm) and large surface area (76.2802 m2 g-1) was confirmed by BET analysis. The paste composition with 67.3 : 30.5 : 2.7 (wt%) graphite, t-ZrO2, and TCP, respectively, exhibited the best results. With a detection limit of 1.0 × 10-8 mol L-1, the electrode displayed a good Nernstian slope of 19.50 ± 0.10 mV decade-1 over the concentration range from 1.0 × 10-2 to 1.0 × 10-8 mol L-1 of Cr(iii) ions. The built-in sensor displayed a quick response time (7 s), was highly thermally stable in the range of 10 to 60 °C without departing from Nernstian behaviour and could be used for about 60 days in the pH range of 2.0 to 6.0. The electrode demonstrated excellent selectivity for the Cr(iii) ion towards a variety of metal ions. For chromium ion determination, numerous spiked real samples, including honey, water, tea, coffee, milk, cheese, and cosmetics, were used. Validation methods were used, and the results showed that there is no significant difference between the two methods (ICP and ISE) at a 95% confidence level. In several real water samples, the estimated limits of detection, limits of quantification, percent recovery, standard deviation, and relative standard deviation showed the effectiveness of the proposed electrode in the potentiometric detection of Cr(iii) ions.

Microstructural evolution of ceramic nanocomposites coated on 7075 Al alloy by plasma electrolytic oxidation

Alumina-zirconia nanocomposite coatings were prepared on 7075 Al alloy by plasma electrolytic oxidation (PEO) at current densities 0.1–0.3 A/cm2 in a Zr-containing electrolyte under DC galvanostatic mode. Coatings were investigated by X-ray photoelectron spectroscopy (XPS), X-ray and electron diffraction, and high-resolution transmission electron microscopy (HRTEM). The coatings developed at current density higher than 0.2 A/cm2 consist of γ-, t- and α-alumina and tetragonal zirconia and were composed of four sub-layers: (i) interface nanocomposite layer close to the substrate with a dense structure of heterogeneously distributed α-Al2O3 and t-Al2O3 nanocrystals (2–5 nm in size) embedded in an amorphous matrix, followed by (ii) a pure amorphous Al2O3 sublayer, (iii) a dense zirconia encapsulated alumina sublayer and (iv) a top amorphous sublayer with dispersed globular alumina and zirconia nanoparticles. The zirconia encapsulated alumina sublayer is composed of large t-Al2O3 and γ-Al2O3 grains bordered by fine t-ZrO2 nanoparticles. The t-ZrO2 phase was nucleated in an atomically coherent manner at Al2O3 grain boundaries. The microstructure evolution in the coating revealed alumina formation at the early stages of the process while the oxidation, crystallization and incorporation of zirconia occurred at the last stages of the PEO process. The phenomenology of the PEO Al2O3/ZrO2 nanocomposite coating formation is presented to account for the present experimental observations.

Composite ceramic coating with enhanced thermal shock resistance formed by the in-situ synthesis of nano-ZrO2

In this research, nano-ZrO2/TiO2 composite coatings were designed for titanium alloys by the in-situ incorporation of ZrO2 nanoparticles into a TiO2 ceramic coating. Precise control over the content and structure of nano-ZrO2 in this nanocomposite coating was achieved by manipulating the pH of the electrolyte during plasma electrolytic oxidation (PEO). The synthesis process and mechanism of tetragonal zirconia (t-ZrO2) were revealed by analyzing the phase composition and microstructure of the coating. The influence of pH on the formation of t-ZrO2 was also revealed. By detecting changes in the electrolyte solute composition before and after PEO, the Zr(OH)4 precursor was determined to be the source of the t-ZrO2 nanoparticles in the composite coating. The yield of t-ZrO2 in the composite coating increased upon increasing the pH of the electrolyte. Moreover, the thermal shock tests showed that increasing the t-ZrO2 content remarkably improved the thermal resistance of the coatings. This strategy and the research outcomes are expected to have great significance for developing advanced nanocomposite coatings on titanium alloys with enhanced thermal shock resistance.

CeO2-stabilised ZrO2 nanoparticles with excellent sintering performances synthesized by sol-gel-flux method

ZrO2 nanoparticles (NPs) stabilised by 12 mol% CeO2 (12Ce-ZrO2) with high sintering ability were prepared using a novel sol-gel-flux method (SGFM) for the first time, where NaCl flux was introduced into a citric acid-based sol-gel system. The microstructure and sintering performances of the as-prepared NPs were compared with those of the product synthesised using the traditional citric acid-based sol-gel method (SGM). The effect of the calcination temperature on the phase compositions and micromorphologies of the as-prepared 12Ce-ZrO2 products was investigated. The results showed that the optimum calcination temperature for the SGFM was 800 °C, and the corresponding 12Ce-ZrO2 product (SGFM-800) was composed of well-dispersed 20–40 nm t-ZrO2 NPs with homogenous micromorphology, while the 12Ce-ZrO2 NPs synthesised using the SGM (SGM-800) were severely agglomerated. The SGM-800 NPs could not be fully densified up to the sintering temperature of 1450 °C owing to severe agglomeration. However, the SGFM-800 NPs exhibited good sintering ability, and a relative density of 99.67 % could be achieved at 1150 °C for 4 h. The fully dense 12Ce-TZP ceramics prepared with SGFM-800 had an average grain size of 0.46 μm. To the best of our knowledge, such a fine grain size has not been reported to date for 12Ce-TZP ceramics obtained by single-step pressless sintering.

Microwave assisted sol-gel synthesis of bioactive zirconia nanoparticles – Correlation of strength and structure

It is well known that long term stability in zirconia has been a problem because of the structural alteration from stabilized tetragonal zirconia to monoclinic that leads to fracture in implants. Microwave (MW) assisted sol-gel synthesis is employed in the present work to prepare stabilize zirconia nanoparticles. ZrOCl2.8H2O is used as a precursor whereas de-ionized water is used as a solvent. Power of microwave radiations is varied in the range of 100–1000W. Zirconia nanoparticles have been characterized under as-synthesized, 6- and 12-months’ room temperature (RT) aged conditions. Metastable phase (MP) of zirconia, appearing under as-synthesized conditions, transforms to phase pure tetragonal zirconia (t-ZrO2) after RT aging that was prepared with MW powers of 100, 200 and 700–1000W. Whereas, MP transforms to mixed tetragonal-monoclinic phases at microwave powers of 300–600W after RT aging. XPS results show presence of oxygen-deficient state of ZrO2 lattice along with surface defects contributing towards the tetragonal zirconia phase under all conditions. Value of dielectric constant (i.e. ~11–12 at log f = 4.0), hardness (~13 GPa) and fracture toughness observed under all conditions are well in agreement to be used for biological implants. Disks of aged t-ZrO2 nanoparticles are checked for their biodegradation test by dipping in simulated body fluid for several weeks. ZrO2, with 26 weeks of immersion, shows small loss in hardness and weight. Stabilized tetragonal zirconia shows strong anti-oxidant activity. Stabilized ZrO2 nanoparticles presented strong antibacterial activity against both gram positive (S. aureus, Bacillus) and gram negative (E. coli) bacteria. Thus, structural and mechanical stability of zirconia (checked after 6 and 12 months) make this material highly beneficial for long term use in biomedical applications.

Unveiling the structural transitions during activation of a CO2 methanation catalyst Ru0/ZrO2 synthesised from a MOF precursor

Carbon Capture, Utilisation and Storage (CCUS) technologies are utilised to minimise net CO2 emissions and hence mitigate the impact of anthropogenic emissions on the global climate. One example of CO2 utilisation is the production of carbon-neutral methane fuel via catalytic CO2 reduction with H2 (methanation). Thermal activation of a metal impregnated metal-organic framework (MOF), 1 wt%Ru/UiO-66 in the presence of H2 and CO2 provides in situ synthesis of a highly active methanation catalyst: H2 promotes the formation of Ru0 nanoparticles, and CO2 behaves as a mild oxidant to remove framework carbon and promote ZrO2 crystallisation. The nature of the active MOF-derived Ru0/ZrO2 catalyst was studied by PXRD, TEM, and XAS, and the evolution of the parent 1 wt%Ru/UiO-66 during thermal activation monitored in operando by synchrotron PXRD. The Ru impregnated Zr-based MOF collapses on heating in H2 and CO2 to form an amorphous C and Zr containing phase that subsequently crystallises as tetragonal (t-) ZrO2 nanoparticles. These t-ZrO2 nanoparticles undergo a subsequent phase transition to the more stable monoclinic (m-) ZrO2 polymorph. In situ activation of Ru/UiO-66 generates a highly active catalyst for CO2 methanation by transforming the MOF precursor into a (carbon-free) crystalline t-ZrO2 support that stabilises highly dispersed metallic Ru nanoparticles. This insight may guide the rational design of future MOF-derived catalysts.

Evaluation of Flexural Strength of Heat Cure PMMA Denture Base Material Reinforced with Various Concentrations of Zirconium Oxide Nanoparticle: An In-vitro Study

Objective: The aim of this study was to investigate the effect of zirconium oxide (ZrO2) nanoparticle dispersion on the flexural property of heat-cure polymethylmethacrylate denture base material. 
 Methods: Eighty specimens were divided into 10 groups of eight specimens; Group 1 unreinforced acrylic, group 2: treated with ethanol alcohol, Groups 3,4,5 and 6 reinforced acrylic specimens with 1, 3, 5, and 7 wt% of untreated zirconium oxide nanoparticle (u- ZrO2) and Groups 7,8,9 and 10 reinforced acrylic specimens with treated and sonicated zirconium oxide nanoparticle in ethanol alcohol (t-ZrO2). X-ray diffraction test (XRD) was used to study the dispersion quality of the tested specimens, and universal testing machine was used to evaluate flexural strength and flexural modulus. SPSS software program used to compare groups results statistically.
 Results: The results revealed significant decrease in flexural strength with u-ZrO2 nanoparticle addition in different concentration groups (p<0.05), while with t-ZrO2 nanoparticle addition, above 3 wt% statistically significant decrease was noted as compared to the conventional group. However, the flexural modulus increased with increasing the both of u-ZrO2 and t-ZrO2 nanoparticles addition. XRD results showed better dispersion quality of the t-ZrO2 than u-ZrO2 throughout the acrylic resin denture base material.
 Conclusions: Flexural strength decreased inversely with increasing u-ZrO2 concentration, while it decreases significantly above 3 wt% of t-ZrO2 nanoparticle concentration. The flexural modulus increased with increasing both of u-ZrO2 and t-ZrO2 nanoparticles. Reduced nanoparticle’s cluster size of t-ZrO2 allows more nanofiller to be incorporated to denture base materials with less adverse effect on the mechanical properties.

Facile corrosion synthesis and sintering of disperse pure tetragonal zirconia nanoparticles

Disperse pure tetragonal zirconia (t-ZrO2) nanoparticles smaller than 10nm are essential for preparation of structural and functional zirconia materials, but syntheses of t-ZrO2 nanoparticles using inorganic zirconium salts usually result in severe agglomeration. In this paper, we report a hydrothermal corrosion approach for improving the dispersity of t-ZrO2 nanoparticles synthesized by precipitation using zirconium oxychloride without any surfactants. Disperse pure t-ZrO2 nanoparticles with average sizes of 4.5 and 6nm and size distributions of 2–11 and 3–12nm were obtained by calcining precipitates at 400°C for 2h and 500°C for 0.5h followed by HCl corrosion at 120°C for 75h, respectively. Disperse t-ZrO2 nanoparticles with an average size of 6nm and a size distribution of 3–12nm were pressed into green compacts at 500MPa and sintered by two-step sintering (heating to 1150°C without hold and decreasing to 1000°C with a 10h hold). The sintered bodies are dense pure monoclinic ZrO2 nanocrystalline ceramic with a relative density of 99.9% and an average grain size of 110nm.

High-speed deposition of tetragonal-ZrO2-dispersed SiO2 nanocomposite films by laser chemical vapor deposition

Tetragonal-ZrO2 (t-ZrO2)-dispersed amorphous SiO2 composite films were prepared by laser chemical vapor deposition at high deposition rates of 40–300μmh−1. Without SiO2 the films prepared at deposition temperatures of 869–1246K contained monoclinic ZrO2. ZrO2 was stabilized in its tetragonal phase in an amorphous SiO2 matrix at deposition temperatures of 867–1170K. The t-ZrO2 particle size decreased from 21 to 11nm with increasing deposition temperature. In the amorphous SiO2 matrix, t-ZrO2 nanoparticles formed a network structure at lower deposition temperatures, whereas the t-ZrO2 nanoparticles were homogeneously dispersed at higher deposition temperatures.

DADD-Assisted Hydrothermal Synthesis of t-ZrO2 Nanoparticles

Tetragonal ZrO2 (t-ZrO2) nanoparticles (diameter: ca. 10 nm; BET-specific surface area: 100 m2/g) are hydrothermally prepared via crystallization of 1,12-diaminododecane (DADD)-hydrous zirconia gels at 230°C for 3 days. The volume content of monoclinic phase is ca. 0.1. The surface-adsorbed hydrocarbon layer (ca. 3 wt%) is observed by FTIR and TGA. They account for the formation of our t-ZrO2 nanoparticles with high-phase purity.

Highly dispersed suspension of YSZ and zirconia nanoparticles by solvothermal processing

Yttria stablised zirconia (YSZ) and tetragonal ZrO2(t-ZrO2) nanoparticles were synthesised by a solvothermal method using ethanol and isopropanol as solvents. Monodispersed YSZ and t-ZrO2 nanoparticles were produced in ethanol. Uniform spherical aggregates of YSZ nanoparticles were obtained in the isopropanol solution. It was found that the average crystallite size was independent of starting material, solvent and product morphology. The solvent had a major effect on the morphology of the aggregates/agglomerates formed from the initial nanocrystallites. The solvothermal YSZ nanopowder was compared with YSZ nanopowder produced by conventional precipitation–calcination using simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The particle size distribution of the agglomerates/aggregates was investigated by light diffraction.

Monolithic t‐ZrO2 Nanopowder through a ZrO(OH)2·xH2O Polymer Precursor

Monolithic t‐ZrO2 (tetragonal structure) nanopowder is synthesized with an amorphous ZrO(OH)2·xH2O polymer precursor. The H2O molecules impart the structure and promote reconstructive thermal decomposition of the structure to t‐ZrO2 nanoparticles on heating at temperatures as low as 200°C. A prevalent endothermic heat output in the dissociation process controls the local temperature in exothermic nucleation and growth of various groups of the reaction species so that it is self‐controlled in high‐energy nanoparticles. Crystallites are, on average, d= 8 nm diameter, and they have a high value of Gibbs free energy or lattice volume Vo= 0.06770 nm3. The excess volume decreases to Vo= 0.06705 nm3 if the reaction temperature is increased to >200°C, i.e., approximately the bulk value of 0.06681 nm3; there is a minor increase to d= 12 nm at 600°C. Many oxygen vacancies in the thin surface space‐charge layers seem to support the stability of small particles in this particular polymorph. A pure m‐ZrO2 (monoclinic structure) appears with d= 22 nm at temperature as low as 800°C. The results are analyzed using X‐ray diffractometry, microstructure, infrared spectroscopy, and thermal studies of the polymer precursor and derivative t‐ZrO2 nanoparticles.