I want to dry a mudrock without disturbing the mineralogical composition due to mineralogical changes. The clay fraction in the mudrock is composed of illite, chlorite and kaolinite.
It is well understood that on heating at a temperature 550oC for about an hour only dehydrates certain clay minerals and hence there would be no change at temperatures 75-105oC
Dear Mr. Günther,
If you prepare samples for XRD or XRF investigations you should dry them at around 105 to 110°C to get rid of the moisture which fresh samples taken from the field have absorbed onto their surface with non intragranular/ intracrystalline effect (German: bergfeucht / field-related moisture). Below that T values you will not see any lattice changes. The best way to demonstrate this is using DTA (differential thermal analysis), where you can see the stepwise changes in the structure of phyllosilicates and expulsion of the different types of water bound to the mineral. The first answer in that Q&A by Dr. Towe was the right one.
Best regards
H.G. Dill
Thank you all for your answers.
@ Mr. Dill:
I don't want to perform XRD-measurements. My goal is to dry the samples for geotechnical investigations. I just wanted to know if there are any potential phase transistions in clay minerals which could be misinterpreted as loss of water.
But I want to conduct a DTA-TG-analysis.
Dear Mr. Günther,
you can rest assured that also for your geotechnical purposes below 110°C no mineralogical effects will be discovered in your samples. DTA and TG might be an option in this case as the clay mineralogical data seem to be of minor importance.
Viel Glück !
H.G.Dill
In TG, you will see a loss of weight, just because of physical water evaporation of your samples. There is no phase change, but you will end up with less weight.
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