Properties of ZrO2–Al2O3 composite as a function of isothermal holding time (original) (raw)
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THE INFLUENCE OF SINTERING TECHNIQUE ON MICROSTRUCTURE AND PROPERTIES OF ZrO2/Al2O3 COMPOSITE
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The following paper presents the results of investigations on the microstructure and mechanical properties of sintered composites in the zirconia-alumina system, fabricated by various sintering techniques. The investigations were performed for a particulate composite consisting of two continuous ceramic phases – zirconia (TZP) and alumina (α-Al2O3), 50 vol.% each. Two different methods were used to produce the samples: pressureless sintering and the U-FAST technique. The microstructure of the obtained sintered composite samples was evaluated using a scanning electron microscope. In addition, the density of the sintered bodies, their hardness and fracture toughness were investigated to evaluate the mechanical properties. Based on the obtained results of the investigations, the influence of the sintering technique on the microstructure and mechanical properties of the sintered composites was determined.
High purity nanocrystalline α-alumina powder was mixed with 20 wt% ZrO 2 by slurry method sintered at temperature (T s) 1450°C, 1500°C, 1550°C and 1600°C for 2 hour. The density, porosity, structural properties and mechanical properties of Al 2 O 3 -ZrO 2 composites with respect to sintering temperature have been explored in the present work. The XRD spectra indicate that α-Al 2 O 3 , t and m-ZrO 2 are the crystalline phases present in 20 wt% ZTA composites for all sintering temperature. It is observed that with higher sintering temperature the intensity of m-ZrO 2 phases increases and the t-ZrO 2 phases decreases. However, t-ZrO 2 retention becomes much easier to trigger the transformation to monoclinic. Higher density of 20 wt% ZTA has been achieved at 1600ºC, whereas the highest porosity was obtained for sintering temperature 1450°C.The microstructures of the samples was studied by using SEM which represents highly homogeneous and finer structure at 1600ºC. The effect of sinterin...
DEVELOPMENT OF ZrO2-Al2O3 BIOCERAMIC COMPOSITES
2007
Metallic abutments, used in dental implant prostheses, have shown good mechanical properties, but the metal core affects the aesthetics. To minimize this problem, ceramic abutments can be used. Dental ceramics prosthesis has been introduced with the objective of improving aesthetic restorations, biocompatibility and chemical resistance. In this work, the effects of alumina additions on the properties and citotoxicity of the ZrO2-Al2O3 composites were investigated. Samples of ZrO2 with varied Al2O3 additions were prepared. Powder mixtures were sintered at 1500 and 1600C in air, for 120 min. Sintered samples were characterized by XRD and SEM. Hardness and KIC were obtained by Vickers indentation method, and in vitro cytotoxicity test was performed as preliminary biological evaluation. In all sintering conditions, samples presented densification higher that 99%TD. Al2O3 addition produces an increase of the hardness, reaching values between 1350 and 1600 HV for the addition of 0 and 30%...
INTERNATIONAL CONFERENCE ON BIOLOGY AND APPLIED SCIENCE (ICOBAS), 2019
The developmental of composites as dental coating materials is growing rapidly. To increase mechanical, physical and aesthetical properties of dental coating materials, has been developed composited dental based on ceramic matrix composites. Only a few ceramic biomaterials that are suitable for this dentistry i.e. zirconia (ZrO2) and alumina (Al2O3). Zirconia and alumina-based ceramic present interesting properties for their application such as a dental coating material. Zirconia was used as the matrix, extracted from natural zircon sands Kereng Pangi, Central Kalimantan and alumina powder were used as the filler. In this work, influence of ZrO2composition on ZrO2/Al2O3 ceramic composites that using 100, 70, 60weight% zirconia was characterized. Powder of ZrO2 and Al2O3 were mixture by planetary ball milling for 3h at 150rpm. Homogeneous of composites can be affected from speed and duration of stirring. The homogeneous of filler and matrix can be improved mechanical properties of composites. Powder mixtures were pressed under 80MPa pressure. Characterization FTIR and XRD were used to confirm the absence of any new phase and the composites were formed. The FTIR analysis showed that no new compounds are formed between ZrO2 and Al2O3. This result can be correlated with the XRD pattern of ZrO2/Al2O3.
Bioceramics Development and Applications, 2010
As years passed by, the use of biomaterials for implants in hard tissues became more commonly used. Since they are heterologous materials, it is extremely important that before using any implant material, it is minutely tested from different points of view. The implant has to display special characteristics so that it may be accepted by the body, even if it is perceived as a foreign object. At the same time, the implant has to allow the appropriate proliferation of the repairing tissues around it till it is totally incorporated in the hard tissue (bone). The incorporation has to be so well made so that the implant is stable/resistant to the mechanical demands (pressures, pulls etc.) that will act upon the region where it shall be inserted. The implant material needs to display specific characteristics so that the body accepts it as best as possible and incorporates it extremely well in the hard tissue. These properties refer especially to aspects of biocompatibility, implant construction and biomechanics (Osborn and Newesly, 1980).
International Journal of Minerals, Metallurgy, and Materials, 2019
The aim of this work was to investigate the microstructure and mechanical properties of 1vol%-Ni-added yttria-stabilized zirconia (YSZ) toughened alumina composites. First, Ni powders were heterogeneously precipitated in an alumina-zirconia powder mixture suspended in water; the prepared specimens were then pressureless sintered at 1550°C/2 h in a 90vol%Ar/10vol% H 2 atmosphere. The structure of phases and microstructure of the composites were characterized by X-ray diffraction and scanning electron microscopy, respectively. Mechanical characterization of the specimens was carried out through Vickers hardness, Vickers indentation toughness, and three-point flexural bending tests. The fine Ni particles were homogeneously dispersed throughout the alumina matrix because of the employed processing method. Furthermore, hardness and toughness values were found to increase by 8% and 50%, respectively, with Ni addition, whereas the relative densities and flexural strength values were found to remain unchanged.
Journal of The European Ceramic Society, 2003
Changes in crystalline phases resulting from low-temperature ageing of different yttria doped and non-doped zirconia-toughened alumina composites and nanocomposites were investigated under controlled humidity and temperature conditions in autoclave. A classical powder mixing processing route and a new modified colloidal processing route were used to process the composites. Different compositions ranging from 2.5 wt.% zirconia in a matrix of alumina to pure zirconia (3Y-TZP) were studied. It was observed that Al 2 O 3 +yttria stabilised ZrO 2 composites exhibited significant ageing. However, ageing was much slower than traditionally observed for Y-TZP ceramics, due to the presence of the alumina matrix. Ageing was clearly limited for zirconia content beyond 25 wt.%. On the other side of the spectrum, Al 2 O 3 +2.5 wt.% ZrO 2 initially presented a monoclinic fraction but did not show any ageing degradation. These composites seem to represent the best choice between slow crack growth and ageing resistance. #
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.
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.
Zirconia-Toughened Alumina (ZTA) is a glistening name for new generation of toughened ceramics for the past decade. In this experiment, microstructural and mechanical properties of ZTA ceramic were modified with TiO 2 as an additive which were constructed using a solid-sintering route. For various weight percents of TiO 2 (i.e. 0 wt%, 2 wt%, 3wt%, 4 wt%, 6 wt% and 8 wt%), corresponding constructed samples were dry mixed, uniaxially pressed and sintered at 1600°C for 1 hour in a pressureless condition. Properties like density, porosity, flexural strength, fracture toughness and Vickers hardness were measured for each sample. The grain growth was observed by using Scanning Electron Microscope (SEM). It was found that the flexural strength, fracture toughness and hardness have gradually increased with TiO 2 additions, reaching its maximum value at 4 wt.% and then decreased upon further addition of TiO 2 . Scanning Electron Microscopy showed that the grain growth of Al 2 O 3 was hindered significantly with the addition of 4 wt% TiO 2 , but increased in size with further addition of TiO 2 . Hardness and bulk density have also improved from 0wt% to 4wt% due to the fine microstructure, thus enhancing its properties.