Effect of substrate hardness and surface roughness on the film formation of aerosol-deposited ceramic films

Abstract

The aerosol deposition (AD) method is a novel ceramic coating technique that allows manufacturing of dense ceramic films at room temperature directly from ceramic powders without any high temperature sintering steps and without expensive (ultra) high vacuum processes. The deposition mechanism can be separated into two stages: the creation of an anchor layering and the subsequent film formation. Step one involves an initial plastic deformation of the substrate surface by the first impacting particles. Especially in the first stage, substrate properties affect the deposition and determine the dominant bonding mechanism. Ductile substrates can be expected to give strong film anchoring, whereas high hardness substrates might require higher particle velocities to form adhering layers. In this study, the influence of the substrate hardness in combination with the surface roughness on the deposition was investigated. Four ceramic substrates (two types of Al2O3, sapphire, and LTCC) with different hardness and surface roughness were coated with Al2O3 in order to study the formation of an anchoring layer and their effect on the deposition rate. As a result, no anchoring layer was found on the hard ceramic substrates.

Revealing the effects of aerosol deposition on the substrate‐film interface using NaCl coating

“…Pre‐AD substrates in Figure A‐C show homogeneous smooth surfaces, signifying a flat, polished surface, which is typically a requirement for the deposition of AD films. It was reported that substrate surface roughness influences the AD film quality and a substrate surface roughness in the range of 0.04‐0.12 µm is suitable for ceramic substrates . Figure D‐F shows the post‐AD substrate microstructure with an apparent change in the surface microstructure, in particular for SUS 304 and glass.…”

“…Therefore, it can be stated that in addition to the elastic modulus, mechanical deformability of the substrate should also be considered for the formation of the anchoring layer. Previous studies indicated that ceramic film deposition on the metallic substrate is easier than that on a ceramic substrate . This is possibly related to the ductility of the metal substrate, ie, the ductile substrate can plastically deform more easily during particle impact.…”

“…It was reported that substrate surface roughness influences the AD film quality and a substrate surface roughness in the range of 0.04-0.12 µm is suitable for ceramic substrates. 39 Figure 2D-F shows the post-AD substrate microstructure with an apparent change in the surface microstructure, in particular for SUS 304 and glass. It is worth mentioning that the deposition parameters, eg, carrier gas, carrier gas flow rate, nozzle to substrate distance, were kept constant for all the substrates.…”

“…Previous studies indicated that ceramic film deposition on the metallic substrate is easier than that on a ceramic substrate. 39 This is possibly related to the ductility of the metal substrate, ie, the ductile substrate can plastically deform more easily during particle impact. The aim of this work is to investigate the effect of AD processing parameter on the substrate interface.…”

Thermal Treatment of Aerosol Deposited NiMn2O4 NTC Thermistors for Improved Aging Stability

“…This leads to film formation. The process begins with the formation of an anchor layer and continues with the formation and densification of the film by a hammering effect of the subsequently impinging particles [36]. This process is often referred to as “Room Temperature Impact Consolidation” (RTIC) [22].…”