Abstract
Cordierite ceramic was fabricated by reducing Al2O3 mole ratio from 2.0 to 1.4 with kaolin, silicon dioxide and magnesium oxide as the raw materials. The effect of reduced Al2O3 mole ratio on the sintering behaviors, phase transition, main properties, and microstructure were characterized in detail. The results show that cordierite phase becomes the main crystallization phase at 1300?C, and mullite phase can be consumed to produce cordierite phase by reducing Al2O3 mole ratio. But additional quartz phase still exists until 1400?C. Moreover, the open porosity, pore connectivity and pore size increase as Al2O3 mole ratio reduces from 2.0 to 1.4 while the linear shrinkage percent and bulk density decrease with the reduced Al2O3. It is considered that the sintering activity of the raw materials at low temperature decreases due to the increase of chemically pure magnesium oxide and silica with the decrease of Al2O3 mole ratio, while the crystallization process, pore growth and cordierite phase rather than the liquid phase control the densification process at high temperature.
Highlights
Cordierite (2MgO·2Al2O3·5SiO2) ceramic has been widely studied due to its outstanding properties, and it has many industrial applications, such as catalysts, microelectronics, refractory products, integrated circuit boards, heat exchanger for gas turbines, membranes, thermal shock-resistance tableware and porous ceramics [1,2,3]
For all the samples with different Al2O3 mole ratios from 2.0 to 1.4, it can be observed that cordierite became the main crystalline phase with a few of quartz and mullite phases
When the sintered temperature increased to 1350 oC, the peak intensity of quartz phase reduced to zero for the samples with 2.0 mole ratio of Al2O3
Summary
Cordierite (2MgO·2Al2O3·5SiO2) ceramic has been widely studied due to its outstanding properties, and it has many industrial applications, such as catalysts, microelectronics, refractory products, integrated circuit boards, heat exchanger for gas turbines, membranes, thermal shock-resistance tableware and porous ceramics [1,2,3]. The stoichiometric composition of cordierite, additives, preparation methods, and sintering process have received extensive concerns for fabricating cordierite ceramic [4, 5]. The difference between the two fabrication methods causes the distinction of the final cordierite productions, including crystallization process and shrinkage behavior. Basic magnesium carbonate as the raw materials [14] and the distinction of the results from the two different fabrication methods still exists. Using the solid-state sintering method, cordierite ceramic was fabricated by chemically pure kaolin, silicon dioxide and magnesium oxide with reduced Al2O3 in this work. Kaolin, silicon dioxide and magnesium oxide were used as the raw materials to synthesize cordierite ceramics. The heating rates were 2 oC/min to 450 oC with a holding time of 1 h and 5 oC/min up to the final temperatures
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