METHOD FOR PRODUCING POROUS-METAL CATHODES FROM TUNGSTEN POWDER

摘要

FIELD: electronic engineering.;SUBSTANCE: proposed method includes step-by-step annealing of source powder at temperature ranging between 1650 and 1750°C including temperature rise by 25-50°C, cake milling, powder quality control upon every annealing step by producing sample pellet compressed at constant pressure P_sp, and evaluation of pressure P of air flowing through sample pellet upon second annealing step until pressure P is attained after at least two annealing steps corresponding to mean powder particle diameter over 4.5 μm, for instance, for P_sp = 2.8 t/cm² at P ≤ 0.45 kg/cm² which are values of its open steam channel in terms of air pressure; this is followed by compression of pellets from powder obtained, their sintering in acid-free medium, and impregnation of sintered pellets in emission-active material; powder particle mean diameter D_p is calculated and should be minimum 4.5 μm but not over 7.0 μm; density range of sintered pellets ρ_{sn min -} ρ_{sn max} is calculated basing on pressure of air flowing through sample pellet using equations ρ_{sn min} = 12.35 - 0.03 D_p + 0.05 D_p ², ρ_{sn max} = ρ_{sn min}+ 20, where ρ_{sn min} (g/cm³) meets condition of minimal open steam channel from its optimal range for given production and ρ_{sn min}, condition of maximal open steam channel, and compressing pressure is chosen from values of ρ_{sn min} and ρ_{sn max} using standard dependence of sintered pellet density as function of specific compressing pressure ρ_sn = f(P_sp).;EFFECT: enhanced life of cathodes, reduced evaporation from them.;1 cl, 3 dwg, 3 tbl