Influence of ZrO2 on the thermo-mechanical response of nano-ZTA (original) (raw)
Related papers
Low-Temperature Processing and Mechanical Properties of Zirconia and Zirconia-Alumina Nanoceramics
Journal of the American Ceramic Society, 2003
The 1.5-to 3-mol%-Y 2 O 3 -stabilized tetragonal ZrO 2 (Y-TZP) and Al 2 O 3 /Y-TZP nanocomposite ceramics with 1 to 5 wt% of alumina were produced by a colloidal technique and lowtemperature sintering. The influence of the ceramic processing conditions, resulting density, microstructure, and the alumina content on the hardness and toughness were determined. The densification of the zirconia (Y-TZP) ceramic at low temperatures was possible only when a highly uniform packing of the nanoaggregates was achieved in the green compacts. The bulk nanostructured 3-mol%-yttria-stabilized zirconia ceramic with an average grain size of 112 nm was shown to reach a hardness of 12.2 GPa and a fracture toughness of 9.3 MPa⅐m 1/2 . The addition of alumina allowed the sintering process to be intensified. A nanograined bulk alumina/zirconia composite ceramic with an average grain size of 94 nm was obtained, and the hardness increased to 16.2 GPa. Nanograined tetragonal zirconia ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughnesses between 12.6 -14.8 MPa⅐m 1/2 (2Y-TZP) and 11.9 -13.9 MPa⅐m 1/2 (1.5Y-TZP).
Thermomechanical properties and microstructure of aluinina-zirconia
Bulletin of Materials Science, 1992
AI,Os~ZrO= composites were prepared in two compositional ranges, 15 ~t/o' o/ ZrO2 and 29 wt,~ ZrO~ with or without yttria or magnesia stabilizers. While 1.5 wt% Y2Oa. produced tetragonal ZrO 2 and fine grain mierostrueture, the 4.5 wt~ Y20 s developed cubic and tetragonaI Zr02 with similar minrostrueture. AI=O~ with 29.5 wt~ ZrO_,-1.5 wt~ Y2Os composition had the highest strength (3,300 kg./cm 2 I. The beading sf:rength remained more nr less ~he same after tllc 6rs~ thermal shock, and then it decreased gradually, but retained some strength after 20 cycles of quench. The toad vs displacement curve became nonlinear alter thermal shock possibly because of formation of microcracks which could be seen by microstructural Sttld[es. Ke).words~ Alumina-zlreonia composites; thermal shock resistance; microcracks; inelasticity.
Materials, 2013
Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young's modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5-20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO 2 grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO 2 content. The material containing 10 vol % ZrO 2 presented a relevant hardness and exhibited the maximum value of K I0 , mainly imputable to the t → m transformation at the crack tip.
2017
In the current study, the effect of adding nano Al2O3 to 3 mol%Y2O3 stabilized tetragonal zirconia (3Y-TZP) prepared by precipitation method on the grain size and the mechanical properties was investigated. Different amount of nano Al2O3 (1.5 wt. % , 2.5 wt.% , 3.5 wt.% and 4.5 wt.%) have been added to (3Y-TZP). X-Ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize both the prepared powder and the full dense ceramic composite. It has been found that ,the addition of nano Al2O3 have an influence on the densification process and lead to increase in both the apparent and bulk relative densities and recorded a 96.45% and 94.46 % respectively at 4.5 wt.%. The results also shows a decrease in grain size from 0.7 μm to 0.62 μm as the amount of nano Al2O3 vary from 0 wt.% to 4.5 wt.% due to the restricted of the grain boundary mobility via the effect of particle pinning. Also, the addition of nano Al2O3 have great effect on mechanical properties .The Vicker...
Effect of sintering curves on the microstructure of alumina–zirconia nanocomposites
Ceramics International, 2014
Zirconia-toughened alumina (ZTA) ceramics of various compositions have high relevance in the field of mechanical engineering for cutting tools and wear parts as well as in biomedical applications for hip and knee implants. In this study a matrix of submicron size a-alumina is reinforced with 10 vol% unstabilized zirconia nanoparticles. The ZTA ceramics were consolidated by means of hot pressing at 1400-1550°C at 60 MPa axial pressure for 1 h in order to test the influence of the sintering conditions on the mechanical properties, microstructure and phase composition. Despite the conventional mixing and milling method used, ZTA nanocomposites of high homogeneity were obtained. Low sintering temperatures result in ultra-fine-grained materials with high hardness. High strength of 900-1050 MPa was observed over the whole sintering temperature range, while toughness rises with sintering temperature. A clear correlation between transformability of the tetragonal phase and toughness cannot be identified. Highest strength was found for ZTA with a low initial monoclinic content and high transformability. Increasing sintering temperatures led to only slight microstructural coarsening but to a migration of zirconia particles and rising monoclinic content. Associated with these effects, a gradual shift from transformation toughening to microcrack toughening was observed.
IJERT-Structural and Mechanical Properties of Zirconia Toughened Alumina (ZTA) Composites
International Journal of Engineering Research and Technology (IJERT), 2014
https://www.ijert.org/structural-and-mechanical-properties-of-zirconia-toughened-alumina-zta-composites https://www.ijert.org/research/structural-and-mechanical-properties-of-zirconia-toughened-alumina-zta-composites-IJERTV3IS20451.pdf The Zirconia toughened Alumina (ZTA) composites with 0-16 wt % of ZrO 2 were prepared by slurry method and sintered at temperature (T s) 1500°C and 1600°C for 2 hours. The density, porosity, structural properties and mechanical properties of Al 2 O 3-ZrO 2 composites with respect to ZrO 2 content as well as sintering temperature have been explored in the present work. About 2% higher density of 16 wt % ZTA has been achieved and the microstructures are highly homogeneous and finer with less porosity when compared to pure Al 2 O 3. The surface morphology of the samples was studied by using SEM. The effect of zirconia content on hardness and elastic modulus were investigated. At 1500°C, maximum hardness shows 15.79 GPa and at 1600°C, it is 19.76 GPa, which is observed for pure Alumina. However, at same temperatures, minimum hardness shows 11.24 GPa and 12.96 GPa, respectively, that is observed for 16 wt% ZrO 2. Elastic modulus also shows same behaviour as shown for hardness. Flexural strength increases with the increase of both zirconia content and sintering temperature. The approach adopted in the present study may provide an alternative to design Al 2 O 3-ZrO 2 composites with improved mechanical properties.
Materials, 2019
Zirconia nanoceramics are interesting materials for numerous high-temperature applications. Because their beneficial properties are mainly governed by the crystal and microstructure, it is essential to understand and control these features. The use of co-stabilizing agents in the sol-gel synthesis of zirconia submicro-particles should provide an effective tool for adjusting the particles’ size and shape. Furthermore, alumina-doping is expected to enhance the particles’ size and shape persistence at high temperatures, similar to what is observed in corresponding bulk ceramics. Dispersed alumina should inhibit grain growth by forming diffusion barriers, additionally impeding the martensitic phase transformation in zirconia grains. Here, alumina-doped zirconia particles with sphere-like shape and average diameters of ∼ 300 n m were synthesized using a modified sol-gel route employing icosanoic acid and hydroxypropyl cellulose as stabilizing agents. The particles were annealed at temper...
Obtaining and characterization of the alumina-zirconia nanocomposite
MRS Proceedings, 2012
ABSTRACTCeramics of alumina of high density and purity can have a broad application area due to the combination of the excellent properties such as resistance to corrosion, good biocompatibility, and high resistance to wear and moderate mechanical resistance. But its low fracture toughness limits its range of applications. One possibility of improvement in the properties of these materials might be in the use of nanometric inclusions of ZrO2 into the matrix of Al2O3. The aim of this paper was to obtain and characterize the nanocomposites of alumina containing 0, 5, 10, 15 and 30 vol% of nanometric zirconium, seeking improvements in the mechanical properties and its comparison with values found for the matrix without the inclusion. For that, nanometric particles of ZrO2 were added into the matrix of alumina in the different proportions, using mixture of suspensions. The samples of alumina and nanocomposites of alumina-zirconium were physically, microstructurally and mechanically char...