High-temperature deformation of amorphous AlPO4-based nano-composites

High-temperature compressive deformation of an amorphous aluminum phosphate nano-composite was investigated at 1200–1300 °C. Microstructural and X-ray diffraction investigations of sol–gel-derived material revealed an amorphous structure with relatively high fraction of closed porosity of ≈15 vol.%. Transmission electron microscopy revealed nanocrystallites, predominantly of carbon, dispersed in the amorphous matrix. Steady-state flow stresses were 10–50 MPa and 50–70 MPa for test temperatures of 1200 and 1300 °C, respectively, as the strain rates were varied from 5 × 10−6 to 2 × 10−5 s−1. Flow stresses increased with strain rates at a fixed temperature: stress exponents were 2.2–2.8 for various test temperatures, indicative of non-Newtonian flow. The non-Newtonian flow was attributed to the presence of the nanocrystalline phases. The creep resistance was found to be on a par with those of conventional oxide ceramics.