Influence of Pre-Annealing on Densification, Microstructure, and Microhardness of Spark Plasma Sintered TiO<sub>2</sub>-MnO<sub>2 </sub>Composites

MnO 2 and TiO 2 composites have garnered substantial research interest for energy applications, including supercapacitor electrodes and photocatalysts. This study investigated the microstructures, densification behaviour, and microhardness of spark plasma sintered TiO 2 -MnO 2 composites. TiO 2 -MnO 2 composites with 10 wt.% MnO 2 and 30 wt.% MnO 2 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 were 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.%MnO 2 sample increased from 97.48 % to 97.71 %, whereas that of the 30wt.%MnO 2 composite increased from 96.11% to 96.46%. Similarly, the microhardness values in the pre-annealed 10wt.% MnO 2 and 30wt.%MnO 2 composites increased by 1.78% and 0.41%, respectively.