Preparation of high surface area nanophase particles by low pressure spray pyrolysis

The influence of reactor pressure on the size and morphology of particles prepared by spray pyrolysis was investigated. Manganese, nickel and copper oxides particles were prepared from acetate and nitrate solutions at atmospheric pressure and 60 torr by ultrasonic spray pyrolysis. Particles with high surface area (17-58 m²/g) and good crystallinity were obtained even at high temperature (800 °C) at 60 torr. The original round shapes of agglomerates were fragmented into nanometer size crystalline particles (< 10 nm), and the intraparticle sintering did not occur. The particles prepared at atmospheric pressure, however, had hollow shapes, submicron size, low surface area (6.1-19 m²/g) and large crystallite sizes (> 40 nm) due to the intraparticle sintering. The pressure effect became much more pronounced as the reactor temperature increased.