Production and characterisation of novel plasma sprayed TiO2 + Cu/Ag powders for use as a marine antifouling coating alternative

Abstract

Within the marine industry fouling is a serious problem that can cost companies substantial money, and cause serious environmental harm. Therefore, antifouling solutions are required to prevent this. However recent studies have identified that current biocide based methods to control fouling are toxic to environment and marine life. Due to this research is required to formulate new methods to control fouling. One method within the biomedical industry to control bacterial growth, which is an underlying principle of fouling is antibacterial materials. Materials such as copper and silver which inherently kill and neutralise bacteria. Adaptation of this technology for antifouling purposes comes with a number of advantages. This thesis therefore investigates the production of TiO2 + Cu/Ag powders and coatings for this purpose. Specifically, on the investigation of composition and morphology of coatings produced using these materials. A wide range of compositions were examined from 5-83at% Cu in both metallic and oxide state, and 2.5-20at% silver. Powders were produced via spray drying, incipient wetness and electroless deposition. Of the methods trailed the most successful was spray drying and incipient wetness. Coatings were successfully applied utilising plasma spray and analysed using XRD and SEM. For thick coatings of >100μm to form the powder size was identified as an important value. Powder size needs to be free from high volume of undersize particles for good results. It was found that coatings generally retained the same composition and phases as the parent powder regardless of additive composition. However, at higher additive compositions, appearance of small unidentifiable peaks that do not match predicted equilibria phases were found. The plasma spray process was also found to contribute to broadening of peaks due to nature of coating analysis, and decomposition of TiO2 to amorphous and magneli phases. SEM of CuO coatings revealed complex microstructure of Cu rich and Ti rich phases despite being predominantly TiO2 + CuO phase. Overall, these findings aid in better understanding the Ti-Cu-O and Ti-Ag-O systems when plasma sprayed, and the resultant coatings formed. This directly helps to inform future works which aim to examine antibacterial/antifouling properties of coatings produced from similar materials.