It is diffecult to answer your question about thermal conductivity of your coatings because thermal conductivity depends on density of coatings, porocity and other parameters which you have considered. I do believe that it can be measured experimentally using standard probe with a coating, which was developed for testing of quenchants. There is a correlation between thickness of a coating and cooling time of probe and thermal conductivity of coating. If you know thickness of your coating and cooling time, you can eveluate what is thermal conductivity of any coating. More information about mentioned correlation one can find in publication:
Kobasko, N.I., Real and Effective Heat transfer Coefficients (HTCs) Used for Computer Simulation of Transient Nucleate Boiling Processes during Quenching, In a Book " Special Issue on Thermal Process Modeling, Simulation , and Optimization", Sahay and Sarmiento, Eds., ASTM International, W. Conshohocken, 2012, pp. 383- 402.
Dear Dr Shaban,
Thank you but the manuscript you had sent to me is one of my publication list !!.
I think you want to upload another one.
Dear Nikolai
Thank you and you are right regarding the thickness, density and porosity strongly affect the conductivity.
However, I want to discuss the conductivity of Al2O3 and the Al5O6N in the term of phase composition, oxide content and theoretical aspects,---
Dr Shaban
I published these papers and I did not discuss the conductivity.
I haven't looked at AlON before, but it is quite interesting.
I remember with the GaN-AlN system, that each crystalline material has a very high thermal conductivity, but once you start formulating AlGaN, the thermal conductivity plummets (pure GaN & AlGaN >> 100W/mK, AlGan ~20). The Liu paper linked discusses this. The conductivity of AlGaN then increases as you warm the material, which is characteristic of amorphous or highly disordered materials, where increasing temperature decreases scattering at boundaries, although exactly what those 'boundaries' are for crystals with substitution atoms is unclear to me.
Going back to the AlON system, ceramic AlN can achieve ~200W/mK, Al2O3 ~ 25-30W/mK. Just using the Wikipedia value for AlON, Kth ~ 12W/mK. I wonder if a similar situation is occuring in this case. I do know that in AlN ceramic fabrication, the key to achieving high thermal conductivity is driving out any oxygen in the material. Various Oxygen removal and gettering processes make the difference between moving material from 100W/mK to 160W/mK, and even up to 195+. So it is little surprise that AlON keeps such a low conductivity having a high Oxygen content.
I would wonder if it is possible to put a phase diagram together based on O or N content...
Article Temperature dependence of thermal conductivity of AI xGa 1-x...
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering