Preparation of nanometric titanium hydrous oxide particles by vapour phase hydrolysis of titanium tetrabutoxide

Spherical titanium nanoparticles in the range of 60 to 500 nm have been obtained by a vapour-phase hydrolysis procedure using titanium tetrabutaxide as raw material. In this work, different parameters such as alkoxide temperature, water temperature, carrier gas flow rate, inlet pressure, vacuum and dilution of the raw material were tested. The most important parameters in order to obtain nanoparticles of low mean size were the flow rate, the alkoxide temperature and the inlet pressure. When the temperature decreases the mean size decreases obtaining nanoparticles below 100 nm when the temperature is set up to 125 degrees C. On the other hand, as the flaw rate that pass through the alkoxide increases the particle size decreases. Same behaviour is observed when the pressure inlet is increased. In all cases, these results are attributed to a minor concentration of the alkoxide (low amount of alkoxide molecules) in the gas stream. The other parameters, vacuum, water temperature and dilution of the alkoxide did not show any important influence in the particle size as the other ones. Polydispersity (broad or narrow particle size distribution) has the same trend. The alkoxide temperature and carrier flow rate generate narrow distributions while the other parameters produces broad distributions. FT-IR analysis of these nanoparticles showed that for sizes below 100 nm the alkoxide is fully hydrolysed and as the particle size increases the nanoparticle has more alkoxide or alcohol retained inside. The heat treatment of these nanoparticles produces a decreasing in the particle size and in all cases, the spherical shape is retained and no blackening in the nanoparticles of higher size is observed. (C) 1999 Kluwer Academic Publishers.