Al 2 O 3 /TiO 2 core/shell powder derived by novel sol–gel routes

Novel sol–gel process is introduced to fabricate Al 2 O 3 /TiO 2 powder. Inorganic salt other than expensive alkoxide is used as precursors. Core/shell structure is achieved by dropwise addition of TiO 2 sol into Al 2 O 3 sol, and ultrafine raw powders are not utilized as cores in the one-pot process. The phase evolution, microstructure, surface composition, and particle size changes in the core/shell structure powders are characterized. Upon calcination, the anatase-to-rutile transformation of TiO 2 phase occurs at low temperature due to the oxygen vacancies of adjacent Al 2 O 3 . TEM image shows the core/shell morphology of the powder, and (110) and (101) planes of Al 2 O 3 /TiO 2 are detected in the interface from HRTEM image. EDS and XPS spectra verify that the Al 2 O 3 core is fully covered by a thin TiO 2 layer. The average particle size decreases slightly due to the volume reduction caused by the anatase-to-rutile and γ -to- α Al 2 O 3 transformations, which increase slightly at 1050 °C due to solid phase sintering of the composite powder. Graphical Abstract