Using a new version of the ALICE equipment, research development are conducted to produce nanocomposites coatings with a perspective in photocatalysis.
As an example, the TiO2/SiO2-np nanocomposite multilayer films were synthesized in a single step by reactive magnetron sputtering combined with a nanoparticle aerosol jet. The SiO2 nanoparticles (SiO2-np) were introduced into a growing TiO2 thin film with different time sequences during deposition for a fixed duration. The SiO2-np acting as impurities are introduced into the TiO2 to willingly disturb its growth and to cause growth defects in order to increase the specific surface area of the photocatalytic film. In reason of the non-photoactive properties of the SiO2 nanoparticles, their introduction allows us to study only the effects induced on the film morphology, microstructure, and photocatalytic properties by their incorporation.
The introduction of nanoparticles in the matrix film changes considerably this morphology regardless of the moment of the nanoparticle incorporation. For all nanocomposite films, more or less large protrusions on their surface are distinguishable.
Top surface micrographs:
Brittle‐fracture cross‐section micrographs:
Film thickness and related porosity
Photocatalytic properties:
This study shows that the incorporation of SiO2-np at any stage of the film growth results in the creation of growth defects that lead to the development of the surface, with larger defects observed (≈500 nm) when SiO2-np is introduced earlier in the process. Additionally, the incorporation of SiO2-np into the TiO2 films also slightly restricts the crystal growth of the matrix films. The TiO2 crystal quality was decreased (dislocation density, micro-strain, and disorder levels increased). Considering the measurement error, the incorporation of SiO2-np did not significantly change the optical bandgap values of the films. In the specific case of TiO2/SiO2-np, it is demonstrated that the introduction of the nanoparticles only at the beginning of the film growth is more efficient than a continuous introduction, resulting in almost 30% improvement of the photocatalytic activity without further optimization. The continuous introduction of the nanoparticles disturbs the development of large growth defects and consequently limits the surface area. Furthermore, the presence on the surface of non-photoactive particles also reduced the surface area of the photoactive phase. The study also highlights several factors influencing photocatalytic activity, emphasizing the significance of the surface area of the photoactive phase. It is then a preliminary step for the synthesis of more complex nanocomposite films with active nanoparticles.