Compatibility between cordierite-mullite ceramics and PCMs

Cordierite-mullite composite ceramics were synthesised with calcined bauxite, talc and quartz as raw materials, and shaped to honeycomb configuration. A series of sealing agents (F series) were designed and tested for sealing AlSi₂₀ and Na₂SO₄ (phase change materials, PCM) within the ceramic honeycomb for heat storage applications. Thermal shock cycles between 200 and 900 ℃were performed for 30 times on the composite material (samples held at 900 ℃ for 12 h in each cycle). XRD, SEM, TG-DSC were used to study phase composition, microstructures and the thermal properties. The results show that Wa, Pa, D and σa of honeycomb ceramic after fired at 1440 ℃ are 2.38%, 6.32%, 2.65 g·cm^-3 and 25.77 MPa the phase compositions are cordierite, Mullite and a small amount of magnesium aluminum spinel. After 30 times thermal shock tests, the Wa and Pa increase slightly whereas D and σa decrease slightly. One of the sealing agents, F2, gives the highest shearing strength at about 2.53 MPa, which is also validated by SEM analyses. The SEM analyses also show that, after 30 times thermal shock tests, the PCMs have a good compatibility with the ceramic substrate with no leakage. TG-DSC studies also show that the phase change temperature of AlSi20/honeycomb energy storage composite material ranges from 571.7 ℃ to 583.5 ℃ with a peak temperature of 578.3 ℃.