Controlling the particle size of nanocrystalline titania via a thermal dissociation of substrates with ammonium chloride

Abstract The anatase titania (TiO 2 ) nanocrystals with an average particle size of 7 nm were prepared by a new method of sol–gel process using titanium n -butoxide (Ti(OC 4 H 9 ) 4 ) as raw materials, acetic acid (HAc) as a modifier, and ammonium chloride (NH 4 Cl) as solid substrates. The hydrous TiO 2 particles were deposited onto the surface of NH 4 Cl nanoparticles during hydrolysis of Ti(OC 4 H 9 ) 4 . When the dry gel was calcined at lower temperature (250 °C), the hydrous TiO 2 particles dehydrated and crystallized on the surface of NH 4 Cl nanoparticles, and finally, thermal dissociation of NH 4 Cl in this process leads to the formation of the pure titania product. The samples were characterized by XRD, TEM, and TGA. The results indicate that the thermal dissociation of NH 4 Cl can control the particle size and inhibit the agglomeration of anatase TiO 2 in the calcining process and simultaneously enhance phase transformation from amorphous TiO 2 to anatase phase.