[greeniq]

I analyze samples of lithium borohydrides with X ray diffractometer, where I suppose to isolate the powder totally from air, any idea how can I do that?

many thanks in advance!!

[cth]

To do powder X-ray diffraction of air sensitive samples, there exists a special system. It is a cylinder in aluminium (the one I saw was roughly 10cm of diameter and 8cm high) that can be closed tightly with screws to avoid air getting in. You can load your sample in it using a glove box. The cylinder has a large widow on one side made of an amorphous polymer, so the X-rays can get into the chamber and out without any diffraction and a minimum of diffusion.

Alternatively, if you really can't get a sample holder like the one I described above, you can simply use a standard one where you cover your powder with a polymer film, making sure it is tightly fixed to avoid air. The problem is that your product is in contact with the polymer and start to react with it or get contaminated. As well, it is difficult to have good isolation from air, so your sample will decompose a bit and will probably need to be trashed after use.

Probably you could simply use some tape to cover your sample (can't make it cheaper  ). However, tape is not completely amorphous and has a preferential orientation (this appears when you stretch it). Place the tape in a way that the preferential orientation will be perpendicular to the X-rays beam. (Remark, I never tried that myself. The best way is definitely to have a special chamber to contain the sample.)