High temperature mechanical behavior of porous cordierite-based ceramic materials evaluated using 3-point bending

摘要

Cordierite-based ceramics are an important segment of the present ceramic industry. In the last years, cordierite-based porous ceramics have received great attention as light structural materials, thermal insulting and catalyst supports, among others. For these applications, a combination of high porosity and low weight of the component are required, together with mechanical stability even at high temperatures which might prevail in use. The combination of these requirements is a challenge due to the compromise existing among them. In this work, materials prepared from two precursor mixes of cordierite based on kaolin, talc and alumina by thermal consolidation (80 °C, 4 h) of stable aqueous suspensions mix-starch were evaluated. Two different native starches, potato and corn, were employed. The starch gel, which acted as binder in the green body, generated the pores when it was eliminated during a further thermal treatment (650 °C, 2 h). The transformation of the raw materials in cordierite was carried out by reaction-sintering at 1330 °C, 4 h. Cylindrical bars of 35-50 mm in length and 3.5-4.0 mm in diameter were prepared using this method, and then, they were mechanically tested from room temperature to 1100 °C using 3-point bending. A servohydraulic testing machine INSTRON 8501 and a SiC fixture (span: 30 mm) were used for the mechanical testing. The tests were performed in displacement control with a constant rate of 0.1 mm/min. The difference observed in the behavior and the mechanical parameters (Young modulus and mechanical strength) of final materials were related with the characteristics of raw materials and their composition, texture and microstructure, especially porosity and the presence of glassy phase.