Encapsulated Titanium Oxide with Al2O3 and its Ultraviolet Shielding Properties
In this work, we encapsulated the titanium oxide particles with a layer of Al2O3 by a sol-gel process and investigated the UV-shielding properties of the obtained Al2O3-TiO2 composites. In this method, Al(NO3)3 aqueous solution mixed with raw titanium oxide powder was hydrolyzed by adding NH3·H2O. The hydrated materials were calcined at 500°C and then the composite of Al2O3-TiO2 was prepared. Different techniques including ICP-AES, XRD, SEM-EDS, and TEM were used to characterize the raw TiO2 and encapsulated TiO2 particles. Chemical analysis showed that TiO2 mass content in the raw titanium oxide particles is 98.25%, and Al2O3 is just 0.75%. After modification, the percentage Al2O3 was increased to 4.48% due to the encapsulation of Al2O3. Trace elements analysis displayed that the concentration of the trace elements were much lower than their original content in the raw titanium oxide, which prove that proved that there was no impurities incorporated into in the sol-gel process. XRD analysis indicated that the modified titanium oxide powders are mainly in phase of rutile, ca. 99.1%, and the profiles exhibit no peaks of crystalline Al2O3 suggesting the layer of Al2O3 exists in amorphous phase. SEM image suggests that the size is in 80~600nm of the raw TiO2 granula and became rougher on the surface, the packing of the agglomerations got looser after modification with Al2O3. HRTEM image shows that the TiO2 particles was evenly coated with a packed layer ~8 nm in thickness. The UV-Vis absorbency experiments showed that the range of wavelength shielded was narrowed from 208-316 nm in the raw titanium oxide to 225-285 nm in the case of the Al2O3-TiO2. The average absorbency of UV was improved from 1.07 to 1.98 at the same content 1.0 μg/mL in the suspended solution. The results reflected that Al2O3 modification process improve the titanium oxide particles UV-shielding properties in selectivity and performance.
M.K. Lei, X.P. Zhu, K.W. Xu and B.S. Xu
J. H. Li et al., "Encapsulated Titanium Oxide with Al2O3 and its Ultraviolet Shielding Properties", Key Engineering Materials, Vols. 373-374, pp. 706-709, 2008