Heat of Immersion of Titanium Dioxide in Water. I. The Effect of the Hydration Treatment of Titanium Dioxide

On anatase and rutile, three samples which differ in the extent of hydration treatment have been prepared, and the surface area, the water content, and the heat of immersion have been measured. The hydration treatment of the sample increases the water content of the sample and lowers the sintering temperature. These facts suggest that the condensation dehydration of surface hydroxyl groups from the facing surfaces of contacting particles is effective for sintering. The plot of the heat of immersion vs. the pretreatment temperature shows a maximum at about 400°C, and the heat of immersion is larger in the sample subjected to heavy hydration treatment. The heat of surface hydration, calculated from the plot of the heat of immersion vs. the water content, does not vary with the hydration treatment; it averages 25.2 and 19.0 kcal/mol H2O for anatase and rutile respectively.