Influence of Inorganic Bases on the Structure of Titanium Dioxide-Based Microsheets

Abstract

Laboratory synthesis of microsheets of titanium dioxide from titanyl sulfate involves the use of ammonia solution, whereas another inorganic base is most likely to be employed at the industrial level, as ammonia is a toxic agent and therefore should be avoided according to European Union (EU) regulations. Selected nontoxic bases such as sodium, potassium, and lithium hydroxides have been tested as an alternative to ammonia solution to obtain amorphous and crystalline TiO 2 -based microsheets. The final products obtained at each step of the procedure (samples lyophilized and annealed at 230 and 800 °C) were analyzed with electron and atomic force microscopy, X-ray powder diffraction, thermal analysis, and Fourier transform infrared (FTIR) and Raman spectroscopies to determine their morphology and phase composition. The differences in the morphology of the obtained products were described in detail as well as phase and structural composition throughout the process. It was found that, in the last step of the synthesis, microsheets annealed at 800 °C were built of small rods and oval or platy crystalline particles depending on the base used. The temperature of formation of anatase, rutile, and alkali-metal titanates in correlation with the ionic radius of the alkali metal present in the sample was discussed.

Study of Interactions between Titanium Dioxide Coating and Wood Cell Wall Ultrastructure

“…For the experiment, amorphous, non-photoactive (so by definition safe for organic matter) planar particles have been synthetized from titanium (IV) oxysulfate dihydrate (TiOSO 4 ·2H 2 O) with an optimized method reported earlier [ 27 , 39 ]. In the final step, the solid product was annealed at 230 °C.…”

“…Because of their morphology ( Figure 2 ), these TiO 2 planar particles could theoretically organize in a snakeskin-like hydrophobic layer. Previous research [ 27 ] showed that the morphology of the samples was not fully homogeneous and that minute quantities of crystalline phase anatase in the form of small 2–10 nm individual crystals were also present.…”

“…The latter is only rarely reported [ 18 , 23 ]. Although this is not clearly stated, based on previous experiments [ 27 ], we can assume that amorphous TiO 2 NPs were studied by Rassam et al [ 19 ] as the annealing temperature was too low (120–150 °C) to obtain crystalline structures. For coating stability, photocatalytic properties need to be suppressed so as to avoid interactions between TiO 2 and the binder [ 17 ], or TiO 2 and the wood matter [ 21 ].…”