Structural Evolution and Property of Hot-pressed Palygorskite Clay

Structural evolution of palygorskites, calcinated from 300 degrees to 1200 degrees C, was studied and ceramic materials were fabricated by hot pressing three types of palygorskite (PG1, PG2 and PG3) at 1000 degrees C. In the calcination process, palygorskite transformed into cordierite, cristobalite and enstatite at 1200 degrees C. After hot pressing, the bending strength and Young's modulus of PG1 ceramics reached 187MPa and 87GPa, respectively showing 125% and 30% increase compared to that of PG2 ceramics. The highest mechanical properties of PG1 ceramics can be attributed to its distinct fracture mode, namely intragranular fracture. Moreover, graphite carbon was detected in PG1 ceramics. Carbon-reinforced palygorskite-based ceramics was obtained by hot pressing synthesized acetamide modified pure palygorskite (PG3). Acetamide was carbonized during hot pressing. The bending strength of the carbon-reinforced PG3-based ceramics was 100MPa, which showed a 33% increase compared with that of the PG3 ceramics.