Production of lightweight foam ceramics by adjusting sintering time and heating rate

Abstract

The heat treatment system was a key factor in the performance of lightweight foam ceramics. Phosphorus tailings and coal gangue were recovered for preparing lightweight foam ceramics by adjusting the sintering time and heating rate. The goal was to set a reasonable heat treatment regime for maximum optimized performance. The influences of sintering time and heating rate on the phase evolution, pore structure, physical properties and heavy metal solidification of lightweight foam ceramics were investigated by the results of XRD, SEM and ICP-MS examinations and theoretical calculations. As a result, extended sintering time promoted to formation glassy phase, which facilitated the average pore size growth from 34.88 µm to 124.23 µm. The larger heating rate (10 °C/min) prevented the vitrification of lightweight foam ceramics with an increase in water absorption (2.31 % − 23.14 %) and a decrease in compressive strength (9.80 MPa − 3.56 MPa). The lightweight foam ceramics exhibited relatively uniform pore structure, high porosity (61.79 %), low density (0.99 g/cm3), satisfactory compressive strength (10.08 MPa), and low water absorption (2.87 %) when they were treated at 1150 °C for 60 min with the heating rate of 5 °C/min. In particular, the extremely low leaching values of heavy metals and potential ecological risk index were detected for the lightweight foam ceramics. The fabricated lightweight foam ceramics satisfy the strength requirements of Chinese national standards for non-bearing building partitions and non-bearing bricks. This technology not only provided practical guidance for adjusting the sintering process to manufacture high-performance lightweight foam ceramics, but also the simultaneous high value-added utilization of phosphorus tailings and coal gangue could be achieved.