Abstract
Al2O3 films were prepared by the aerosol deposition method at room temperature using different carrier gas compositions. The layers were deposited on alumina substrates and the film stress of the layer was calculated by measuring the deformation of the substrate. It was shown that the film stress can be halved by using oxygen instead of nitrogen or helium as the carrier gas. The substrates were annealed at different temperature steps to gain information about the temperature dependence of the reduction of the implemented stress. Total relaxation of the stress can already be achieved at 300 °C. The XRD pattern shows crystallite growth and reduction of microstrain while annealing.
Highlights
In order to obtain dense and hard ceramic coatings or films, ceramic materials have typically to be sintered above 800 °C, alumina even sometimes above 1800 °C [1]
The vacuum pump builds a rough vacuum inside the chamber and inside the aerosol generator where the raw ceramic powder is placed
By passing a carrier gas through the powder, an aerosol is formed and particles are transported driven by the pressure drop from the aerosol generator into the chamber
Summary
In order to obtain dense and hard ceramic coatings or films, ceramic materials have typically to be sintered above 800 °C, alumina even sometimes above 1800 °C [1]. There, the particles impact on a substrate and build a dense layer by fracture and plastic deformation of the particles on the surface of Materials 2014, 7 the substrate [2] This mechanism is called room temperature impact consolidation (RTIC). By a slit-nozzle, the aerosol jet is accelerated up to several hundred m/s and ejected on the target, forming a ceramic layer at a deposition rate of several μm/min [2,5] It is the main feature of the AD method that it does not require any sintering process for building dense ceramic layers with a closely packed structure, high strength, and strong adhesion [6]. The Al2O3 films were deposited on 150 μm thick alumina substrates at room temperature in order to evaluate the bending of the substrates due to the mechanical stress within the coating and for SEM cross-sections.
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