0C005Specially prepared compounds or powders for the manufacture of gaseous diffusion barriers, resistant to corrosion by UF6 (e.g. nickel or alloys containing 60 % by weight or more nickel, aluminium oxide and fully fluorinated hydrocarbon polymers), having a purity of 99,9 % by weight or more and a particle size less than 10 μm measured by ASTM B330 standard and a high degree of particle size uniformity.