TiO₂ sol was produced by the sol-gel method through the hydrolysis and the aging of tetrabutyl titanate and the TiO₂ film was obtained by dipping and uniform lifting of the acid-treated and ultrasound-treated clean glass slides into the TiO₂ sol followed by aging, drying, and calcination. The effect of the hydrolysis control agents to the formed sol was researched and the crystalline state, the morphology, and the photocatalytic properties of the products after calcination were characterized. The structural morphology, the contact angles before and after illumination, and the self-cleaning properties of the TiO₂ film were characterized as well. The results showed that by using acetylacetone as the hydrolysis control agent, the formed TiO₂ sol had relatively high stability. The product after the calcination of the TiO₂ sol was of single anatase type with crystalline size of 18–20 nm and it could degrade nearly 100% of methylene blue after 90 min illumination. The formed TiO₂ film is compact, continuous, smooth, and had the properties of super-hydrophilicity (after 30 min illumination due to its contact angle decreasing from 21° to nearly 0°) and anti-fogging capability, which indicated its excellent self-cleaning property.

In order to improve the dispersion of nano-TiO₂ particles and enhance its self-cleaning properties, including photocatalytic degradation of pollutants and surface hydrophilicity, we prepared nano-TiO₂-coated SiO₂ microsphere composite self-cleaning materials (SiO₂–TiO₂) by co-grinding SiO₂ microspheres and TiO₂ soliquid and calcining the ground product. The structure, morphology, and self-cleaning properties of the SiO₂–TiO₂ were characterized. The characterization results showed that the degradation efficiency of methyl orange by SiO₂–TiO₂ was 97%, which was significantly higher than that obtained by pure nano-TiO₂. The minimum water contact angle of SiO₂–TiO₂ was 8°, indicating strong hydrophilicity and the good self-cleaning effect. The as-prepared SiO₂–TiO₂ was characterized by the nano-TiO₂ particles uniformly coated on the SiO₂ microspheres and distributed in the gap among the microspheres. The nano-TiO₂ particles were in an anatase phase with the particle size of 15–20 nm. The nano-TiO₂ particles were combined with SiO₂ microspheres via the dehydroxylation of hydroxyl groups on their surfaces.

TiO₂-coated wollastonite composite pigments were prepared by the mechano-chemical grinding of wollastonite and TiO₂ powder together in a wet ultrafine stirred mill. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and infrared spectra were used to investigate the microstructures and morphologies of the composite and the reaction mechanism. The results indicate that the TiO₂-coated wollastonite composite pigments have similar properties to titanium dioxide pigment, showing much better properties than dry and wet mixing of wollastonite and TiO₂. The hiding power of TiO₂-coated wollastonite composite pigments (45% TiO₂) is 17.97 g/m², reaching 81.08% of titanium dioxide. A firm combination between wollastonite and TiO₂ is obtained through a surface dehydroxylation reaction during the mechano-chemical method.

CaCO₃-TiO₂ composite particles were prepared with calcium carbonate (CaCO₃) and TiO₂ in stirred mill according the wet grinding method. The pigment properties, morphology, and structure of CaCO₃-TiO₂ composite particles and the interaction behaviors between CaCO₃ and TiO₂ particles were explored. In the CaCO₃-TiO₂ composite particles, TiO₂ is uniformly coated on the surface of CaCO₃ and the firm combination between CaCO₃ and TiO₂ particles is induced by the dehydration reaction of surface hydroxyl groups. CaCO₃-TiO₂ composite particles have similar pigment properties to pure TiO₂. The hiding power, oil absorption, whiteness and ultraviolet light absorption of composite particles are close to those of pure TiO₂. The application performance of CaCO₃-TiO₂ composite particles in the paint is consonant with their pigment properties. The contrast ratio of the exterior paint containing CaCO₃-TiO₂ composite particles is equivalent to that of the paint containing the same proportion of pure TiO₂.

In order to improve the photocatalytic degradation efficiency of nano-TiO₂, reduce its usage and realize recycling and reuse, CaCO₃–TiO₂ composite photocatalyst was prepared with calcium carbonate (CaCO₃) and TiO₂ in a grinding machine through the integration of grinding depolymerization, dispersion and particle composition. The photocatalytic degradation performance, recycling performance, structure and morphology of CaCO₃–TiO₂ were studied. The interaction mechanism between CaCO₃ and TiO₂ and the improvement mechanism for the photocatalytic performance of TiO₂ were also discussed. The results show that under the UV light irradiation for 20 and 40 min, the degradation efficiency of methyl orange by the composite photocatalyst with 40% TiO₂ (mass fraction) was 90% and 100%, respectively. This was similar to that of pure TiO₂, and the performance of the composite photocatalyst was almost unchanged after five cycles. CaCO₃–TiO₂ is formed by the uniform loading of nano-TiO₂ particles on the CaCO₃ surface, and the nano-TiO₂ particles are well dispersed. Due to the facts that the dispersion of nano-TiO₂ is improved in the presence of CaCO₃ and the charge transport capability is improved through the interfacial chemical bonds between CaCO₃ and TiO₂, the formation of this complex is an intrinsic mechanism to improve the photocatalytic efficiency of nano-TiO₂ and reduce its usage in application processes.