Influence of Pre-Annealing on Densification, Microstructure, and Microhardness of Spark Plasma Sintered TiO2-MnO2 Composites

MnO2 and TiO2 composites have garnered substantial research interest for energy applications such as supercapacitors and photocatalysis. This study investigated the microstructures, densification behaviour, and microhardness of spark plasma sintered TiO2-MnO2 composites. TiO2-MnO2 composites with 10 wt. % MnO2 and 30 wt. % MnO2 were sintered at a temperature of 1000 °C and applied pressure of 25 MPa. To investigate the influence of annealing, the second batch of powders with similar compositions was pre-annealed at a temperature of 500°C for 5 minutes before consolidation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the powders and compacts. The results revealed that the pre-annealing stage influences the microstructural constituents, densification, and microhardness. The formation of pores and a new phase was observed in SEM images and XRD patterns. The relative densities of the 10wt.%MnO2 sample increased from 97.48 % to 97.71 %, whereas that of the 30wt.%MnO2 composite increased from 96.11% to 96.46%. Similarly, the microhardness values in the pre-annealed 10wt.% MnO2 and 30wt.%MnO2 composites increased by 1.78% and 0.41%, respectively.