I am using High Temperature Platinum Pans suitable for temperatures up to 1000°C. I never had problems with these pans at any conditions (gas, heating rate, final temperature). However, I noticed that a specific sample I am using caused the melt of the platinum pan and loss of pan mass starting just above 800 °. At the end of the experiment the bottom of the pan had holes! I did a temperature calibration of the instrument and tested another platinum pan with calcium oxalate and it was fine. Then, tested my material at the same conditions and the pan melted again!
Has anyone faced this problem before?
Info: TA Q5000IR, HT-Pt pans, 50ml/s N2 gas flow, heating rate 15°C/min, end temperature 1000 °C. Sample contains C,O,H,P,N and maybe traces of Cl
Dear George Pappas,
I think that Platinum works as a catalyst during performing your experiment in the instruments (TGA). By collecting CO and CO2 in the furnace chamber, at high temperature some chemical reaction might be happen between your sample and Platinum which plays the role of catalyst.
George Pappas Alloying or combination of the Pt with another material will cause the destruction.
Dear George,
Interesting observation! Platinum is stable towards most organic materials, but not in contact to Phosphorus. It forms several eutectic alloys, e.g. Pt5P2 (space group C2/c), which melts below 800 °C. Please have a look here:
https://link.springer.com/content/pdf/10.1007/BF02898271.pdf
All the best for your research!
Thomas
Dear Georges,
Normally the Pt pans are frequently used up to 1000°C in TGA experiments. If the problem arrives only for a specific sample, there is probably a reaction between the sample and Pt pans. It is possible that a chemical reaction occurs since Pt can behave as catalyst (especially at high temperatures around 800°C). Since you told about the holes at the bottom of the pan, another possibility is the corrosion (pitting corrosion!) of Pt pans by some products (sulphuric acid or hydrochloric acid,...) formed by the decomposition of your sample. Another possibility would be the decrease of the Pt melting temperature by alloying with other elements (may be some eutectic composition of Pt with someting else).
Hoping that your TA instrument always works.
Best regards
Thank you all very much for your responses! It seems that you are right. There must be a combination of factors such as alloying, pit corrosion etc that all take place at the same time and cause the damage of Pt. Maybe also the pure quality of nitrogen (presence of oxygen) contributes to these events. Nevertheless, since my material gets carbonised from around 600 °C I am expecting that most of the heteroatoms will be already released and their concentration should be more than 4 wt% above 700 °C. I am planning to do some experiments with Mass Spec connected to the TGA and identify the released gasses at each stage.
Atilla Atli Thank you very much for your responses. Unfortunately, the TGA is not working properly now. After a couple of experiments at 1000 °C the instrument now is stack and showing 1314 ºC. I did a full reset both of the instrument and computer, undated the firmware and instrument parameters, disconnected the thermocouple, removed and replaced the fuse but still it shows 1314 °C. Any idea?
Dear George,
I understand that the situation is not very confortable since an apparatus does not work anymore in a lab.
Do you know the type of the thermocouple (TC) uses the TA Q5000IR? I am not sure the problem comes from the computer/software. I would first check the TC if it is broken. If the TC is type Pt-X, it is also subjected to the similar reactions as Pt pans.
Best regards
Atilla Atli Yes I checked and it looks like the ceramic coating of the TC is broken at the lower end. The TC was already heavily used and the replacement time was close anyway. Probably the corrosive reactions accelerated the corrosion of the TC as well. We will replace it and I will write again in this post some recommendations for the users. Lesson learned!
Dear George,
Your are talking about the ceramic coating of TC. Is it a coating or ceramic tubes? Ceramic is essentially used for electrical insulation. Even the ceramic is broken, if the TC does not touch somewhere else, it can measure the correct temperature. I would check the welding of TC. If two wires of welding of TC is broken, it is difficult to weld the TC mounted on the apparatus. It is better to replace TC. But if welding of TC is ok, it is possible that TC touches somewhere (may be grounded) since ceramic insulation is dead. You may just need to carefully and slightly push the TC for detaching the touching points.
Atilla Atli it is more like a ceramic tube which covers 3 metal wires. Apparently the tube was somehow pulled up and the inner wires lost connection. I pushed it back down and now the TC is showing the correct temperature so it's working again. Thank you for the hint! Nonetheless, I need to see if it's going to last in long term because Waters send us a quote for the Lower Furnace Assembly (not the furnace just the mounting of the TC) and the TC for...... €7,318 !! Only the TC is €2520 ....
Phosphoric acid and aluminum are usual suspects! both alloy with platinum and leave holes in the pan.
- Badges
- Science topic
- Similar topics
- Geoscience
- Cartography
- Mapping