Controlling the Size and Morphology of TiO2 Powder by Molten and Solid Salt Synthesis

Nano and submicrometer scale titanium oxide (TiO₂) powders were synthesized by solid and molten salt synthesis (SSS and MSS) from amorphous titanium hydroxide precipitate. Sodium chloride (NaCl) and dibasic sodium phosphate (Na₂HPO₄·2H₂O, DSP) separately or as mixture with different weight ratios were used as the salts. At the eutectic salt composition (20% DSP/80% NaCl), the microstructure and phase composition of the TiO₂ was changed from equiaxed nanoparticles of anatase with size ∼40–50 nm, to mixed microstructure of bundle and acicular particles of rutile with 0.05–0.2 μm diameter, 6–10 μm length, and aspect ratio 20–60 depending on treatment time and temperature. At high temperature (825°C) and long time (30 h), microstructural differences were significant for the powders treated with different salts. Particle morphologies ranged from equiaxed, to acicular, to bundles, to nanofibers with very high aspect ratio. At lower treatment temperature (725°C) for shorter time (3 h), the morphology of the products did not change with different salt compositions, but the crystallite sizes changed appreciably. Different starting titanium precursors influenced particle size at lower temperature and time. Titanium hydroxide heat treated without salt resulted in significant grain growth and fused secondary particles, as compared with more finely separated and lightly agglomerated powders resulting from SSS and MSS treatments.     

A Revision of OPTEMP-LS Model for Selecting Optimal EMP Combination for Minimizing Sediment and Water Yield from Hilly Urban Watersheds

Water Resources Management - Hilly watersheds are inherently susceptible to more sediment and water yield. Urban developments in hills cause conversion of the natural sloppy surface to bare steep...