Open atmosphere laser assisted spray pyrolysis technique for deposition of Al_2O_3 and yttria stabilised zirconia nanostructured coatings

摘要

A novel laser assisted open atmosphere CVD/pyrolysis technique, for the synthesis of dense, hard nanostructured oxide coatings, has been successfully developed in-house. In this process 0.5 to 2.5 mum size droplets of an appropriate metal organic compound/metal nitrate dissolved in a suitable solvent were transported into a quartz tube, using a carrier gas. To this tube a CW Nd: YAG laser (1064 nm) was coaxially coupled. The laser, upon interaction with the precursor, caused its vaporisation/activation. The activated precursor aerosols and the laser were made to impinge the substrate which is placed at an optimum distance. The activated aerosol reacts with oxygen present in the atmosphere at the laser heated spot on the substrate surface to give an oxide coating. Nanostructured alumina coatings were synthesised on steel substrates using aluminium acetylacetonate in ethanol as well as aluminium nitrate solution as the precursors. YSZ coatings were produced using zirconyl and yttrium nitrate mixture (Zr: Y=4:1) precursor solution.