Hey guys,
as another contribution to the #SciencePic series, I want to show you today a five years old picture - please excuse if the quality is not up-to-date.
At these days, during my Ph.D. research, I worked with intermetallic compounds which were mostly alkaline earth silicides and gallides. One option to synthesize these compounds is to melt them in a metal ampoule, e.g. made of niobium or tantalum. Probably, I will show you another option in another post.
This time, I used niobium ampoules and wanted to heat them at about 1000 °C. Because metals oxidize when they are in contact with air at higher temperatures, I protected the ampoules in a fused silica ampoule in vacuo. Maybe, the glass was a little bit too thin this time or the metal lay in a bad way and expanded too much upon heating. Anyways, as you can see on the right side, the silica ampoule broke.
I find it quite funny, that two of the metal ampoules oxidized and kept their shape without falling to pieces. So if you want a special shape of niobium oxide, maybe you can try to shape the metal first and then put in in the oven at higher temperature?
See you next time!
Wow ! Niobium and tantalum! I dont have a chance to work on it. You use it for metal complex synthesis eventually? I have completely no idea their chemistry haha.
Btw, I had once tried to activate molecular sieve in oven, held by a round bottom flask at 800 degC, and i got the flask completely deformed, which look pretty weird yet funny. Unfortunately I dont have a photo on hand.
We also have no idea how we can prevent this happen, except heat at a slightly lower temp.
Hey!
No, we use it because it is quite inert and a good container material for synthesis. Some groups use gold instead which is more expensive and very soft and therefore maybe not so easy to handle.
Why do you activate it at such high temperature? Was it a special type of molecular sieve or just to dry it? We normally dry it at 200 °C, maybe in vacuo.
Typical lab glass (like e.g. Duran) begins to get soft and melt at about 400 - 450 °C. If you need higher temperature, you should use special glass or fused silica, which can be used to about 1200 - 1250 °C max. I don't know, if you can buy flasks that are made of silica. I presume, it would be expensive because it is not that easy to make.
Wow!!! I do heard that people use gold as container, but I really surprise that niobium or tantalum can do the job!!!!! Really nice!!!
We had been having experience that heating with ~ 200 deg C under vacuum for 5 minutes but doesn't work very well (I used to vacuum the flask and use heat gun to dry MS in the past). Heated to > 600 deg C always give very good result so I stick with it, now I may have to re-consider to lower down the temperature a bit haha. I didn't expect the glass can only hold up to 400 degC. Anyway, i can still use the deformed flask for the MS activation in the future ~