Multicomponent toughened ceramic materials obtained by reaction sintering (original) (raw)
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Processing and properties of zirconia-toughened alumina ceramics
Bulletin of Materials Science, 1994
AlaO3:ZrO2 ceramics have been prepared from physically mixed puro oxide powders. The results indicate that careful processing of the starting powders and a two-stage sintering process can avoid expensive processing methods like hot pressing/hot isostatic pressing used for achieving high densification. The mechanical properties were measured and the resultant microstructure studied to explain the toughening behaviour of this material.
Dense mullite–zirconia-zirconium titanate ceramic composites by reaction sintering
Ceramics International, 2015
Materials from the Al 2 O 3-SiO 2-ZrO 2 and the Al 2 O 3-SiO 2-ZrO 2-TiO 2 systems have several high temperature applications because they present the good refractoriness, chemical inertness, adequate mechanical and thermo-mechanical behaviors with a relatively good cost: performance ratio. In this work stoichiometric (3:2:1) molar incompatible mixtures of alumina (Al 2 O 3), zircon (ZrSiO 4) and titania (TiO 2) were slip casted and sintered in a 1300-1500 1C temperature range in order to obtain mullite (3Al 2 O 3 Á 2SiO 2), zirconia (ZrO 2) and zirconium titanate (ZrTiO 4) dense triple ceramic composite. Both sintering and reaction occurred after the thermal treatments. Reaction progress and densification evolutions were established. Dense Triplex composite materials were achieved after 1500 1C treatments. The reaction-sintering was followed by XRD, TG-DTA, and dilatometry. Densification started at 1100 1C and the chemical reactions only started above 1300 1C. Aluminum titanate (Al 2 TiO 5) was found to be an intermediate of the reaction after 1400 1C treatments. Materials treated below 1300 1C presented a partial densification of the unreacted starting powders. Resulting ceramic materials were characterized. The crystalline phases were evaluated, as well as the texture properties. The achieved microstructure consisted in interlocked multiphase ceramic with zirconia (monoclinic) grains. The achieved Hv and K IC reached 9 GPa and 4.3 MPa m 1/2 respectively. The dense and interlocked ceramic microstructure and relative high mechanical properties of the developed material encourages several high temperature applications. Finally it can be pointed out that after 1500 1C treatments some detrimental grain growth was observed.
Effect of sintering additives on the properties of alumina toughened zirconia (ATZ)
MRS Communications
The effect of small amounts of copper oxide, manganese oxide, and stainless steel as sintering additives on the sintering behavior and mechanical properties of Alumina Toughened Zirconia (ATZ, 3Y-TZP with 20 wt% Al2O3) ceramic composites were evaluated and contrasted with that of undoped ATZ by using microwave sintering (MW) method. Green bodies were sintered at 1250°C, 1350°C, and 1500°C using a holding time of 5 min., with a heating rate of 30°C /min. In general, all ATZ samples exhibited a similar trend, as the results showed that the relative density and mechanical properties increased with increasing sintering temperature regardless of the addition of dopants. It was found that the addition of 0.2 wt% CuO, 0.5 wt% MnO2, and 0.2 wt% SS were beneficial in enhancing the densification and improving the mechanical properties of ATZ without inducing grain coarsening. The ATZ composite samples' relative density, tetragonal phase stability, microstructural evolution, Vickers hardne...
Alumina Toughened Zirconia Made by Room Temperature Extrusion of Ceramic Pastes
Ceramics, 2000
A novel preparation route for ATZ (alumina toughened zirconia) ceramics is presented, using a commercial ATZ powder (a mixture of 20 wt.% alumina and 80 wt.% zirconia containing 3 mol.% yttria) as a solid filler and an ATZ sol or gel (of the same composition) as a liquid binder for paste extrusion at room temperature. The pastes have a total oxide content of approx. 70 wt.% and during heat treatment the binder composition accommodates to the composition of the filler powder. Extruded samples are characterized before and after heat treatment by determining their shrinkage, bulk density, apparent density and apparent porosity. The optimal firing temperature is determined to be about 1550 °C. Quantitative X-ray phase analysis is used to establish the phase composition (ratio of monoclinic to tetragonal zirconia) and to calculate a (spatially averaged) mean value for the true density of the prepared nanocomposite after firing, which is 5.45 g cm -3 . For optimally sintered specimens the bulk density is approx. 5.06 g cm -3 , i.e. 92.8 % of the theoretical value. The total porosity after sintering is approx. 6.8 % (open 4.7 %, closed 2.1 %).
Zirconia transformation in multi-phases ceramic composites
Low cost composite ceramics based on zircon-mullite-zirconia-alumina phases were prepared by reaction sintering of boehmite (AlOOH) and zircon (ZrSiO 4 ) powders. Boehmite to zircon weight ratios of the starting powders were varied (10 to 90 wt. %). The green compacts were made by uniaxial pressing at 7 MPa followed by cold isostatic pressing at 250 MPa. A reactive sintering in air of these compacts was made at different temperatures between 1400 and 1600°C during 2 hours. A quantitative evaluation of the present phases was based on XRD. Dilatometric tests on the reaction-sintered composites were carried out in order to study the zirconia phase's transformations and their thermal expansion coefficient (). In addition, the effects of both boehmite/zircon ratios and sintering conditions on the mechanical properties (Hardness Hv, Elastic modulus E and fracture toughness K IC ) of the obtained composites were characterized by Vickers indentation.
Influence of starting materials on the reaction sintering of mullite–ZrO2 composites
Materials Science and Engineering: A, 2000
Mullite-zirconia composite materials were prepared by reaction sintering of a-alumina, aluminium hydroxide and aluminium nitrate as alumina sources, and zircon powder. The compaction of different calcined powders, and the reaction development, densification behaviour and microstructural investigations of different samples were examined at temperatures ranging from 1350 to 1600°C for 2 h holding time. X-ray diffraction peaks suggested fully developed mullite and zirconia phases by reaction sintering of zircon and aluminium nitrate, and showed more retained tetragonal ZrO 2 at 1600°C. Relatively dense sintered samples were obtained by the mixture of zircon and a-alumina powders. The morphology of intergranular ZrO 2 particles was found dependent on the growing conditions because of the using of different starting materials.
MECHANICAL PROPERTIES OF ZIRCONIA TOUGHENED ALUMINA PREPARED BY DIFFERENT METHODS
Le Journal de Physique Colloques, 1986
Resume -Des ceramiques alumineuses renforcees par de l a zircone ont Gte -preparees par deux procedes d i f f e r e n t~ a p a r t i r des memes matieres premieres (poudres). Le premier u t i l i s e l e broyage par a t t r i t i o n e t l a compression I chaud ; l e second, une dispersion 6lectrochimique, l e coulage en barbotine e t l e f r i ttage sans charge. L'influence des parametres d'elaboration sur les proprietes mecaniques des pieces denses e s t examinee. L'influence des teneurs en ZrOz e t Y203 e s t discutee.
Ceramics International, 2014
PURPOSE. The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIALS AND METHODS. Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo Everest � ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS. Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION. Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block. [J Adv Prosthodont 2010;2:81-7] KEY WORDS. Zirconia block, Mechanical properties, Sintering behavior, Linear sintering shrinkage ⓒ 2010 The Korean Academy of Prosthodontics This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. J Adv Prosthodont 2010;2:81-7
ZrO 2-CaO CERAMICS-A COMPARATIVE STUDY
2016
The aim of this paper is the obtaining of final dense ceramics starting from zirconia powders. In the first step, zirconia powders were prepared through sol-gel method, using different amounts of CaO: 6, 7 and 8 mol%. After synthesis, the powders were dried at 100°C and then heat treated at 700°C for 3 hours. In the second step, zirconia ceramics were obtained. The powders were uniaxially pressed, followed by HIP-hot isostatic pressing at temperatures of 1200°C and 1300°C, for 1 hour , under 150 MPa, in an argon atmosphere. After HIP, the samples were morphologically and structurally characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In this step were also studied ceramic properties like density, compressive strength and Young's modulus.