Phosphate ceramics − carbon nanotubes composites:liquid aluminum phosphate vs solid magnesium phosphate binder

Physical properties (thermal stability, compressive strength, electrical conductivity, and electromagnetic interference shielding ability) of phosphate composites based on liquid aluminum phosphate and solid magnesium phosphate binders with up to 2 wt% addition of multi-walled carbon nanotubes (MWCNTs) are compared. Phosphate matrix proves to have a significant inhibiting effect on the oxidation of MWCNTs embedded into the ceramics, which starts at temperatures 100–150 °C higher than in free air. Moreover, thermal treatment of the composites at temperatures up to 800 °C enhances the mechanical properties of the ceramics. Addition of small amount of MWCNTs results in a further mechanical reinforcement of both types of host matrices. The compressive strength of ceramic composites based on solid binders is found to be 40–60 MPa higher than that of their liquid-binder-based counterparts, while their electrical percolation threshold is substantially lower than that of the aluminum-phosphate-based composites.