Thermionic Tungsten/Scandate Cathodes and Methods of Making the Same

摘要

A thermionic dispenser cathode having a refractory metal matrix with scandium and barium compounds in contact with the metal matrix and methods for forming the same. The invention utilizes atomic layer deposition (ALD) to form a nanoscale, uniform, conformal distribution of a scandium compound on tungsten surfaces and further utilizes in situ high pressure consolidation/impregnation to enhance impregnation of a BaO-CaO-Al2O3 based emissive mixture into the scandate-coated tungsten matrix or to sinter a tungsten/scandate/barium composite structure. The result is a tungsten-scandate thermionic cathode having improved emission.

主权项

1. A process for making a thermionic dispenser cathode, the process including:
providing a powder of refractory metal and/or metal alloy; placing the powder inside a furnace having a controlled atmosphere and heating the powder in the flow of hydrogen or hydrogen/inert gas mixture to reduce surface oxides to produce a cleaned powder; placing the cleaned powder inside a particle atomic layer deposition (ALD) reactor and depositing a conformal nanometer-scale film of a scandium compound on all particles of the powder to produce a scandium compound-coated powder; making a porous preformed compact of the scandium compound-coated powder ; and without exposing the porous preformed compact to air, placing the porous preformed compact in contact with an emissive mixture comprising a barium compound; and without exposing the porous preformed compact with contacted emissive mixture to air, subjecting the porous preformed compact with contacted emissive mixture to a predetermined pressure P and temperature T to form the cathode; wherein T is greater than a melting point of the emissive mixture; and wherein an application of the pressure P and temperature T causes the emissive mixture to infiltrate into the porous preformed compact.