Particle production and anatase formation in amorphous particles at in-droplet hydrolysis of titanium alkoxide

Anatase crystallization in amorphous particles was investigated during droplet-to-particle synthesis of titania. Ethanolic solution of carboxylic acid-modified titanium tetrabutoxide precursor, including water, was dispersed and conveyed to a tube flow reactor at 350-600°C. The formed submicron-sized particles were characterized by aerosol measurements, X-ray diffraction, and electron microscopy. An aerosol number mode was observed at particle diameter of 250 nm representing the particles formed of droplet drying. Additional ultrafine particles were formed in air atmosphere at 450°C and in nitrogen at 600°C from decomposition and outgassing of precursor species and a subsequent particle formation. An anatase crystalline phase was observed in the particles produced at 500°C in nitrogen. The location of anatase formation was investigated by TEM from thinned sections of the particles. The crystals were observed near the surfaces and indicating columnar growth.