The kinetics of desilication of synthetic spent Bayer liquor and sodalite crystal growth

The kinetics of desilication of synthetic, sodium aluminosilicate solution (spent Bayer liquor) and growth of sodalite crystals have been studied under isothermal, batch crystallization conditions close to those prevailing in Bayer process heat exchangers. The desilication rate of the liquor via the formation and growth of sodalite scale on steel substrates was found to be independent of agitation rate. With sodalite seeding, the desilication rate was observed to increase dramatically due to seed crystal growth with the suppression of scale formation. An activation energy of 30 kJ mol−1 and a second order dependence of the desilication rate on relative supersaturation of SiO2 were obtained for sodalite crystal growth

Effect of niobium on the structure of titanium dioxide thin films

This paper reports the effect of niobium on the structure of titanium dioxide (TiO2) thin films deposited on glass. The results obtained indicated that the direct current (DC) co-sputtering of Ti and Nb onto glass substrates in the presence of oxygen results in the formation of Nb-doped anatase thin films with strong preferential orientation. In the concentration range between 0 and 40 at.% Nb, niobium is incorporated into the TiO2 lattice according to a substitution mechanism, entering Ti sites in the cation sub-lattice. No evidence exists for a solubility limit < 40 at.% of Nb under the applied deposition conditions, however, it is not believed that an equilibrium situation prevails. Lattice charge compensation was concluded to occur by the formation of cation vacancies for samples with up to 10 at.% Nb, and by Ti3+ or Nb4+ ions for the samples with ≥ 15 at.% Nb, the latter in conjunction with cation vacancy compensation