After much delay i managed to get a powder coating gun and tried injecting some powder into a vacuum chamber.

turns out any air stored in the powder expells the powder into a cloud as soon as it enters the chamber.

So i would either need a very high velocity stream to reduce the divergence before impact or i would need to remove all air from the powder in an earlier chamber. i might be better off trying to use the cloud in the chamber to deposit powder. eitherway this project has fallen behind with other things on my mind. I'll hopefully get back on it later this year.