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Engineering
Materials and Chemical Engineering
Total Emissivity as a Function of Temperature (Ceramics)
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[QUOTE="jdawg, post: 6454003, member: 499239"] This was helpful, thank you. It straightened out some inconsistencies in how I was thinking. No, I mean the emissivity. I'm trying to figure out how the emissive properties of a material change with temperature. Oh gosh, how embarrassing. I promise I knew blackbody emissivity is 1. Yes you're right, that should say emissive power here. Ok, that sounds familiar. I think this is the plot describing what you're talking about for blackbodies, would you expect to see a similar trend for a real material? [ATTACH type="full" width="251px"]277561[/ATTACH] I did a little mental exercise to see what would happen if I used approximate values from the diagram above to plot ε vs temperature... Using this relationship: ε = E/(σT[SUP]4[/SUP]) [ATTACH type="full" width="398px"]277563[/ATTACH] Anddd for a blackbody it looks like emissivity decreases as temperature increases (at least for one wavelength, probably reasonable to assume that the total emissivity would follow a similar trend)! So I think you helped me answer my own question! I got caught up in the emissivity component of the Stefan-Boltzmann equation and wasn't taking into consideration that the T[SUP]4[/SUP] value in the denominator is really going to dominate how the emissivity behaves. Do you think my reasoning makes sense? If so, how would you explain the emissivity of a real ceramic material [I]increasing [/I]with temperature? Perhaps after experiencing elevated temperatures the material undergoes some sort of change in its microstructure? Or the surface becomes rougher, therefore increasing the emissivity? How would you explain an increase in emissivity if one occurred? And now I'm curious about how the spectral absorptivity would change with temperature for a real material? [/QUOTE]
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Total Emissivity as a Function of Temperature (Ceramics)
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