High-Temperature Characterization of Reaction-Sintered Mullite-Zirconia Composites (original) (raw)
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Microstructure and mechanical properties of mullite-zirconia reaction-sintered composites
Acta Metallurgica et Materialia, 1993
The flexural strength, fracture toughness (Klc), creep behaviour and thermal shock of mullite~irconia and mullite-zirconia-alumina composites obtained by reaction-sintering of zircon + alumina mixtures have been studied in the temperature interval ranging from room temperature to 1400°C. The results are discussed in terms of the microstructural features of the reaction-sintered composites.
Ceramics, 2019
Mullite-Zirconia refractories are well known for their good resistance to corrosion and thermal shock. In this study, several mullite-zirconia composites were developed from andalusite, alumina and zircon sintered at 1600 °C for 10 hours. The samples were subjected to thermal shock carried out after heating at 1200 °C, in order to study the mechanical and thermomechanical behaviour as a function of the amount of zirconia dispersed in the mullite matrix. It appears that that the amorphous phase (SiO2), determined by X-ray diffraction, produced by the decomposition of andalusite, increases considerably with the amount of final zirconia in the composite and has a very important influence on the porosity. This amorphous phase seems also to have an important influence on the mechanical properties of the material. The characterisation of the thermomechanical behaviour (elastic properties and damage monitoring) was carried out thanks to ultrasonic techniques (US echography and Acoustic Emi...
Mechanical behavior of mullite-zirconia composites
EPJ Web of Conferences, 2010
In this work, mechanical properties of mullite-zirconia composites synthesised through reaction sintering of Algerian kaolin, Į-Al 2 O 3 , and ZrO 2 were characterized. Phases present and their transformations were characterized using x-ray diffraction. Hardness H and fracture toughness K IC were measured by Vickers indentation using a Zwick microhardness tester. The flexural strength was measured through three point bending test using an Instron Universal Testing Machine. It was found that the increase of ZrO 2 content (from 0 to 32wt.%) decreased the microhardness of the composites from 14 to 10.8 GPa. However, the increase of ZrO 2 content (from 0 to 24wt.%) increased the flexural strength of the composites from 142 to 390 MPa then decreased it with further increase of ZrO 2 content. Also, the fracture toughness increased from 1.8 to 2.9 MPa.m 1/2 with the increase of ZrO 2 content from 0 to 32 wt.%; and the rate of the increase decreased at higher fractions of ZrO 2 content. The average linear coefficient of thermal expansion (within the range 50 to 1450°C) for samples containing 0 and 16 wt.% ZrO 2 sintered at 1600°C for 2 hours was 4.7 x10-6 K-1 and 5.2 x 10-6 K-1 respectively.
Journal of the European Ceramic Society, 1998
Mullite-zirconia composites containing 0 to 7 mol% yttria were prepared by reaction sintering process from Indian coastal zircon flour and calcined alumina. The main raw materials were attrition milled. Samples were isostatically pressed and sintered at temperatures of 1400 to 1650°C with 2 h soaking time. The resulting composites were characterised in terms of phase compositions, martensitic start (MS) temperature, mechanical properties and microstructural features. The presence of yttria results in a dense composite material at a comparatively low temperature. Addition of yttria increases the tetragonal zirconia fraction and reduces the Ms temperature. Yttria goes into solid solution which was detected by EDX analyses. The eflect of yttria on thermal expansion coeficient, room temperature Jlexural strength, hardness, fracture toughness is discussed. 0 1998 Elsevier Science Limited. All rights reserved
Characterization of in-situ zirconia/mullite composites prepared by sol-gel technique
Journal of Asian Ceramic Societies, 2021
The main objective of this study was to investigate the role of zirconia addition to mullite through an in-situ reaction aimed at improving both the mechanical properties and the sinterability behavior. In this work, mullite-zirconia composites were produced using a solgel technique. Different amounts of zirconia (0, 10, 15, and 20 wt.%) were added to the mullite, and the calcined gels were sintered at 1550-1700°C for 1 h. The apparent porosity and bulk density of the blank and zirconia/mullite composites were estimated in accordance with ASTM C-20. The phase composition and sample morphology were evaluated via X-ray diffraction (XRD) and scanning electron microscopy analysis (SEM), respectively. Furthermore, the mechanical properties and thermal expansion coefficient (TEC) were also evaluated. The results revealed that the apparent porosity decreased and the density of the zirconia/mullite composites increased when the sintering temperature was increased from 1550 to 1700°C. However, the mechanical properties improved with increasing zirconia content and MZ20 sintered at 1700°C exhibited the maximum bending strength. The TEC results reflected the influence of the composition on the sample TEC. Samples with higher ZrO 2 content yielded higher TEC figures than those with lower content.