Preparation and characterization of whisker-reinforced ceramics from coal fly ash

A new type of ceramic is developed based on tobermorite whiskers, in which aluminum replaces some of the original silicon atoms. These Al-tobermorite whiskers are synthesized from coal fly ash through a dynamic hydrothermal method. Their fine fiber morphology and Al-substitution produce bulk ceramics with excellent mechanical properties. When sintered at 900 °C, a temperature lower than the one used for conventional ceramics, these whisker-reinforced ceramics have a flexural strength of 52.27 MPa, an open porosity of 9.51%, and a bulk density of 2.15 g/cm3. These properties are attributed to the Al/Si ratio in the fly ash within an ideal range to improve the crystal form of the tobermorite as well as the wollastonite produced by sintering, without leaving residual Al that may affect the mechanical properties of the ceramics.