Optically transparent, dense α-Al2O3 thick films deposited on glass at room temperature

Alumina films up to 5 μm thick have been deposited on fused silica and stainless steel substrates by a novel aerosol-jet deposition process at room temperature. The films are dense, uniform and adherent. Moreover, Al2O3 film deposited on fused silica substrate is transparent for visible light. Transmittance of 1.5 μm thick alumina film is 83% measured at 800 nm, and that of 5.5 μm thick film is 68%. Scanning electron microscopy images and XRD analysis have revealed that the films have α-Al2O3 crystallite structure however crystallite size is order of magnitude smaller than that raw material powder. Vickers microhardness of the films deposited on stainless steel has been measured. Aerosol-jet deposition becomes promising method for surface coating.