Curie point calibration of thermogravimetric analyzer (TGA)

Sample TGA scans of Curie points

Welcome to my Curie point calibration website

When I worked at Dupont Pioneering Research Analytical in 1964 I developed the Curie point method for calibrating the Dupont 950 thermogravimetric analyzer (TGA)

TGA is a method for analyzing the thermal decomposition of materials especially organic polymers. A small sample of material is placed in a platinum "boat" which is suspended from a tiny quartz rod. The quartz rod is one arm of a balance. A thermocouple temperature measuring device is aligned next to the sample. A quartz tube is slid over the sample with a furnace around it. The sample is heated to decomposition and the weight loss and temperature are recorded. There is an inherent problem in accurately determining the transition temperatures because the thermocouple cannot touch the sample.

I solved the problem by putting a metal or other material of known Curie point (the temperature at which a material changes from ferromagnetic to paramagnetic) in the sample "boat". The furnace was placed in a magnetic field. The effect of the magnetic field made the material appear lighter. When the Curie point was reached the sample appeared to gain weight, thus providing a calibration for the TGA. This technique has become the world wide laboratory standard. The calibrations are normally done with Ni and Fe as well as alloys. I also tested CrO2 because Dupont was developing the material for recording tape in 1964.

CrO2 has a curie point of 122deg C. A subsequent Curie point method which is the subject of a patent filed in 1967 doesn't mention this material. 



I wish to be recognized as the inventor of the Curie point method for calibrating TGAs


Click for pictures of Dupont 951 TGA

Mark A. Forte, Richmond, Va

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I invented the Curie point calibration of TGA in Oct 1964