Cold Gas Spraying of Ceramics Using the Example of Titanium Dioxide

Abstract

Functional titanium dioxide coatings have a high potential for photocatalytic applications. However, the high process temperatures of conventional thermal spray methods lead to undesirable phase transformations. Cold gas spraying seems to be beneficial, since for ceramic coatings no phase transformations have been observed so far. In this study, bonding of cold-sprayed ceramic particles on metal substrates is elucidated by investigating single impacts obtained from wipe tests. Different feedstock powders were used, consisting of agglomerated titanium dioxide nanoparticles. The single particle impacts were investigated by scanning electron microscopy and confocal microscopy. The results demonstrate that bonding of particles is influenced by the substrate material, substrate temperature, powder properties and spray conditions. In addition, powder characteristics seem to be of particular importance. The results allow for conclusions regarding favorable conditions for cold spraying of ceramics.

A Brief Review on TiO₂ Coating Deposited by Cold Spraying

“…The result seems to be in agreement with the chemical bonding mechanism. However, the result contradicted that of Gutzmann's, whose experiment showed that preheating the substrates was good for TiO 2 particles deposition [20]. Above all, the bonding mechanism of cold sprayed TiO 2 coatings is still unclear, and a lot of work is needed to clarify it.…”

“…It was supposed that the adhesion was caused by the substrates' shear instability, and the jet from substrates would adhere ceramic particles. Gutzmann [20] etc obtained the impact morphology of single TiO 2 and studied the deposition of different particles on substrates with different temperature. It showed that there were concentric rings on the impacted substrates, like the shear instability zone.…”

Composite Peening - A Novel Processing Technology for Graded Reinforced Aluminium Matrix Composites

“…gravity or centrifugal forces, for the separation of particles in homogeneous powders, solids or melts. These methods include the centrifugal casting [16][17][18], slip casting with sedimentation [19], centrifugal powder molding and many others [10]. The disadvantage of almost all methods is the fact that the targeted grading of the reinforcing particles in a component can only be achieved with a high process complexity.…”