Dolomite-zirconia reaction sintered bonded coarse magnesia ceramics: effect of the bonding proportion (original) (raw)
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Reaction Sintering of Mexican Dolomite – Zircon Mixtures
Boletín de la Sociedad Española de Cerámica y Vidrio, 2005
The present work has been conducted aiming to develop additional phase [Ca 3 SiO 5 , Ca 2 SiO 4 and/or Ca 3 Mg(SiO 4) 2 ]-bonded magnesia refractory materials via reaction sintering of dolomite-zircon mixtures, employing a Mexican dolomite containing an excess of 3 wt% of CaCO 3. The study was based on phase equilibrium data extracted from the quaternary system CaO-MgO-SiO 2-ZrO 2 , to put it more precisely, base on the projection from the MgO-apex of the liquidus surface of the primary crystallization volume of MgO onto the opposite face of the above mentioned quaternary system. The refractory materials designed within this system were obtained by attrition milling, followed by cold isostatic pressing and high temperature reaction sintering. All initial and produced materials were characterized by ICP-AES, XRF, XRD, SEM-EDX, DTA and TG analyses. The results obtained indicated that reaction sintering of dolomite-zircon mixtures is an interesting route to produce MgO-CaZrO 3-additional phase refractory materials.
Effect of Nanospinel Additions on the Sintering of Magnesia–Zirconia Ceramic Composites
ACS Applied Materials & Interfaces, 2014
Nanocrystalline magnesium aluminate (MA) spinel powder produced through a coprecipitation method and calcined at 900°C for 1 h was added to magnesia−zirconia composite in the range of 0−25 mass % and sintered at 1600°C for 2 h. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used for studying the microstructure and the phase composition of the sintered composites. Bulk density, apparent porosity, volume shrinkage, and Young's modulus of the sintered composites were also investigated. The results revealed that the nanospinel addition up to 20 mass % increases the sintering ability and Young's modulus of the composite bodies. Microstructure showed that the presence of nanospinel and zirconia in the triple point between magnesia grains closed the gaps in the ceramic matrix and enhanced the compactness of the composites.
Fabrication and Characterization of Mullite Reinforced MgO Added ZrO2 Ceramics
European Journal of Science and Technology, 2021
In this study, mullite (3Al2O3.2SiO2) and 10 mol % magnesia added zirconia (10 mol % MgO-90 mol % ZrO2) ceramic powders were synthesized by conventional ceramic production processing route. The mixtures were prepared by mechanical alloying method in acetone environment with zirconia ball mill. The powders were dried in oven at 110 ºC for 24 hours before mixing. Mullite (3Al2O3.2SiO2) and 10 mol% magnesia added zirconia (MgO-ZrO2) ceramic powders were synthesized by reaction sintering from the powders made up of stoichiometric proportions of Al2O3, SiO2, MgO and ZrO2 powders after being homogenized in acetone environment in ball mills. Mullite (3Al2O3.2SiO2) and 10 mol% magnesia added zirconia (MgO-ZrO2) ceramic powders were synthesized in air at 1600 o C for 3 h and 1300 o C for 2 h, respectively. Then, the ceramic phases formed were made ready to form ceramic-ceramic composites by crushing, grinding and sieving processes. Then 0 and 10% by weight mullite (M) added magnesia doped zirconia (MgZ) mixtures were prepared by powder metallurgy method. The prepared mixtures were wet milled with zirconia ball mill for 24 h and sieved. After drying, the powders were compacted to preforms of 56x12x10 mm by uniaxial pressing at 200 MPa. The green compacts were sintered at 1500-1600 o C for 1-5 h in air conditions using a heating rate of 5 o C min-1 in a high temperature furnace. Then, microstructure (SEM), phase analysis (XRD), mechanical (hardness, 3-point bending and wear) and physical properties (% shrinkage, water absorption, porosity and density) tests were performed on the mullite added magnesia doped zirconia ceramic composites. In this study, whether there is a phase change in the ZrO2-MgO mixture at high sintering temperatures and the effect of mullite additive on the properties of this mixture was investigated. The data obtained were presented in graphs and tables and their comments were made.
Multicomponent toughened ceramic materials obtained by reaction sintering
Journal of Materials Science, 1985
Fully dense zirconia toughened ceramics with a mullite matrix from the basis of information on the quaternary system ZrO2-AI203-SiO2-CaO, in a temperature range as low as 1425 to 1450 ~ C, have been obtained by reaction sintering of zircon/ alumina/calcium carbonate mixtures. The shrinkage, advance of reaction, microstructure and mechanical properties of different compositions are reported. The results are explained in terms of a transitory liquid phase that appears at temperatures lower than 1400 ~ C.
The effects of the addition of yttria stabilized zirconia and sintering temperatures on the phases developed and the mechanical properties of sintered ceramic produced from Ipetumodu clay was investigated. The clay of known mineralogical compositions was thoroughly blended with 2% (vol) yttria, 8% (vol) zirconia. From this and the raw clay standard samples were prepared, fired at 1200oC and 1300oC. The sintered samples were then characterized for the developed phases using x‐ray diffractometry analysis, microstructural morphology using ultra‐high resolution field emission scanning electron microscope (UHRFEGSEM) and various mechanical properties. It was observed that primary mullite and sillimanite were developed in the samples produced. The samples produced solely from the raw clay could not withstand 1300oC due to stress induced by the transformation from one silica phase to another. This phase transformation also adversely affected the mechanical properties of the sintered raw clay. The additive improved on the mechanical properties of the samples by the consumption of the silica phases to form zircon phase in addition with the other phases and the excess zirconia. It was concluded that the sample fired at 1300oC have the optimum mechanical properties.
Densification Studies of Tetragonal Zirconia with Manganese as Sintering Additive
The effects of small additions of MnO 2 on the sinterability of tetragonal zirconia (Y-TZP) over the temperature range from 1250ºC to 1500ºC was studied. The results indicated that the mechanical properties of Y-TZP were dependent on the dopant amount and sintering temperature. It was found that relative densities above 98% of theoretical could be obtained in bodies sintered at low temperatures of 1250ºC and 1300ºC with the additions of ≥ 0.3 wt% MnO 2 . In comparison to the undoped samples, the additions of up to 1 wt% MnO 2 and for sintering up to 1350ºC was found to be beneficial in enhancing the Vickers hardness of the ceramic. The fracture toughness of Y-TZP however, was found to increase only in the 1 wt% MnO 2 -doped samples when sintered above 1400ºC.
n Present work, the properties of Al2O3 powder was studied through incorporation of MgO Nano powder along with ZnO Nano powder and followed by sintering at various temperatures. Previously ZnO and MgO were introduced with Al2O3 separately to improve physical and mechanical properties like densification, micro hardness, fracture toughness etc. In current project, 0.25wt% and 0.50wt% MgO was added with ȕ- Al2O3 matrix along with constant 0.1wt% ZnO and sintered those samples at 14500 oC, 15000 oC, 15500 oC respectively. Properties like densification, micro hardness, and wear rate of all these sintered products were measured and discussed where the best composition found was 0.1% ZnO-0.25%MgO-99.65% Al2O3 sintered at 15000oC. Change in properties was observed due to faster densification rate and pinning effect provided by the doping particles.
Calcia stabilized zirconia (CSZ) ceramic material was synthesized with stoichiometric compositions 4, 8, 12 and 16wt.% by mixed oxide reaction using fine homogeneous salts of zirconia and calcia. Powder compacts were sintered at 1950°C for 6h in an inert argon atmosphere. The phase identification, purity, crystalline and lattice parameters of cubic CSZ were measured by X-ray diffraction (XRD). Combination of cubic zirconia (Ca0.15Zr0.85O1.85), calcium-zirconium oxide (CaZrO3) and zirconium oxide (ZrO) phases were observed in all compositions. The percent relative densities were measured in order to evaluate the material performance and found to decrease from 85 to 74% with increase of stoichiometeric compositions 4 to 16wt%. These results were in agreement with scanning electron microscopy (SEM) where it was observed that porosity increased with increase of calcia. The coefficient of thermal expansion was estimated by dilatometry. The results revealed that coefficient of thermal expansion (α) decreases with the increase of compositions from 4 to 16wt.% .
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.
Ceramics-Silikáty, 2012
In this investigation, the mullite–zirconia composites were prepared by reaction-sintering of alumina and zircon powder. Besides, the slip casting method was employed for fabrication of these composites and different times of milling process were used for reducing the particles size of raw materials. Then, the effect of raw materials particles size on the properties of these composites was investigated. The physical properties, fracture toughness, flexural strength, phase composition and microstructure of these composites after firing at 1600°C were studied. The results showed that the milling time and then, particles size of raw materials have a great effect on the phase composition and properties of mullite–zirconia composites. The formation of tetragonal-zirconia is favored by reducing of particle size which, leads to increasing of the fracture toughness and flexural strength of these composites.