Thermal Insulation Monolith of Aluminum Tobermorite Nanosheets Prepared from Fly Ash
2015
Bai, Jilin | Li, Yuanzhi | Ren, Lu | Mao, Mingyang | Zeng, Min | Zhao, Xiujian
A thermal insulation monolith of aluminum tobermorite nanosheets was prepared by a facile method of one-step hydrothermal reaction and molding of a high energy ball milled slurry of fly ash, sodium bentonite, calcium hydroxide, and sodium water glass, followed by drying at ambient pressure. The monolith was characterized by XRD, FTIR, TG-DSC, SEM, TEM, BET, mercury porosimeter, and AFM. The addition of both sodium bentonite and sodium water glass plays a crucial role in preventing shrinkage and improving the porosity of the monolith. The monolith has the microstructure of randomly oriented and multually interwoven aluminum tobermorite nanosheets among which there are numerous macropores. Interestingly, the aluminum tobermorite nanosheets can be exfoliated by ultrasonication treatment to provide single-layer ultrathin nanosheets of aluminum tobermorite with a thickness of 1.18 nm and an aspect ratio of ∼1000. The monolith of aluminum tobermorite nanosheets has low apparent density (0.077 g cm–³) and very low thermal conductivity (0.03793 W m–¹ K–¹). The low thermal conductivity of the monolith is attributed to its high porosity or pore volume due to the presence of numerous macropores among aluminum tobermorite nanosheets.
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