Hierarchical Flower-Like Hollow SiO₂@TiO₂ Spheres with Enhanced Thermal Insulation and Ultraviolet Resistance Performances for Building Coating

In this paper, a novel 3D hierarchical flower-like hollow SiO₂@TiO₂ sphere (FHST) with a large number of irregular nanosheets was successfully prepared by a solvothermal method and subsequent calcination process, in which multiple different functional components were perfectly integrated into a single nanostructure. The morphology and structure of FHSTs were characterized by SEM, TEM, XRD, XPS, and BET. The growth mechanism of the 3D flower-like structure was obtained through a series of single-factor experiments, of which hexamethylenetetramine acted in a vital role. Moreover, it was also used as a filler for polyacrylate substrate to improve the thermal insulation and ultraviolet resistance properties of architectural coatings. The results showed that the composite film with FHSTs had lower thermal conductivity and higher light reflection performance compared to those with hollow SiO₂ spheres, hollow TiO₂ spheres, and hollow SiO₂@TiO₂ spheres. More significantly, its transmittance at the full wavelength of ultraviolet light was almost zero, exhibiting a prominent inhibitory effect on UVA. In addition, compared with commercially available hollow glass microspheres, FHSTs had more excellent thermal insulation performance in practical applications.