I'm looking at the ALD process for a uni project and could do with some clarification on a couple of points. Does anyone have any idea what the effect of non-uniform substrate heating would be? Would it harm the chemical bonding and cause ablation? I cant seem to find out from anywhere what an acceptable temp. variation would be. Very confused!
Astronuc
Apr12-08, 07:03 PM
If the substrate and coating have very different coefficients of thermal expansion then one will be under tension and the other compression.
Is this metal-to-metal and are they similar crystal structure, or is this ceramic to metal, metal to ceramic, or ceramic to ceramic?
Also, one would have to look at the diffusion of the deposition species into the substrate, and whether that changes the microstructure at the interface.
There could also be grain growth issues if the temperature of the substrate gets sufficiently high.
However, if this is atomic layer - nanometers thick, some of these issues may not be of concern.
harry_harrin
Apr12-08, 07:48 PM
The case i'm looking at is metal to ceramic and it is the nanometer range of thickness
Astronuc
Apr12-08, 08:50 PM
The case i'm looking at is metal to ceramic and it is the nanometer range of thickness Ceramic substrate with metal layer?
Look at the CTE's. As the metal cools and shrinks, I would expect it would be under tension and the ceramic under compression - assuming the CTE of metal > CTE of ceramic.