Cracking of titania nanocrystalline coatings

Abstract

Cracking of wet-chemically precipitated nanocrystalline TiO 2 films deposited on different platelet-like substrates is investigated. The thicknesses of the films are also in the nanometric range: 60, 140 or 300 nm. Scanning electron microscopy, X-ray diffraction and nitrogen adsorption are employed to determine layer thickness, grain size, and porosity. The synthesis of TiO 2 films through an aqueous route affords very good reproducibility of these properties (layer thickness ±5 nm). Mica, SiO 2 and Al 2 O 3 platelets are used as substrates, providing different properties with regard to surface charge, structure and roughness. The drying step is found to be responsible for the cracking of some of the TiO 2 layers and the evolution of the cracks during sintering is related to shrinkage of the substrate. Film thickness as well as the chemical nature of the substrate influences the cracking of nanocrystalline TiO 2 films during the drying step.

Effects of multiwall carbon nanotubes in reducing microcrack formation on electrophoretically deposited TiO2 film

“…Many reasons have been proposed for the crack formation of the inorganic films such as drying stresses of the liquid inside the pores of the drying film, different thermal expansion coefficients between the substrate and deposited particles [17][18][19][20] or the reduction of particle bonding strength as the film thickens. If microcracks occurring on the TiO 2 films are from the reduction of the nanoparticles' bonding strength, these may be minimized by adding some materials, which are long and able to bond to TiO 2 nanoparticle, into the TiO 2 solution.…”

Liquid‐Phase Sintering of Nanocrystalline Titania Doped with Boron Oxide: Bulk Versus Thin Film

“…If dense layers are needed, for example for optical applications such as interference pigments, 17,18 a stiff substrate will cause tensile stresses in the layer 18,19 . These stresses reduce the densification rate considerably and can enhance cracking of the film 20 …”

Effect of thickness and cracking phenomena on the photocatalytic performances of Ti/TiO2 photoanodes produced by dip coating

“…To the best of our knowledge, there is no study in literature that analyzes how the cracking phenomena in thin films of TiO 2 can affect the photocatalytic performances. In this respect, this work does not want to be a further improvement on the state of the art of TiO 2 catalyzed water splitting, but tries to put a focus on a common issue [25][26][27][28] of dip-coated TiO 2 thin films and its effect in their photo-catalytic performances. The study focuses on the importance of reducing dynamic viscosity of particles dispersion in order to get a thinner and more adhering coating which would present a low content of cracks.…”