Investigation of electron emitting barium-calcium aluminate fabrication process for impregnated microwave tube cathodes

Higashi, Charissa; Lima, Nelson Batista de; Matos, J. R.; Giovedi, Claudia; Motta, C.C.

doi:10.1109/imoc.2005.1579982

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…It is based on the thermionic emission of electrons from the surface metal to vacuum when metal is to heat above 1100 °C4 . Despite the electron emission control of impregnated thermionic cathodes being based on quantum mechanics principles, the construction of the thermionic cathodes for a long lifetime and reliably operation of microwave tubes is related to, mainly, the material and metallurgical processing 5,6 .…”

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Metallurgical Processing for Impregnated Thermionic Cathodes Manufacturing

2022

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A metallurgical process using a very high temperature Mo-Ru brazing filler alloy to join a controlled porous tungsten cathode button and a single-crystalline molybdenum cathode body for microwave tubes manufacture was developed † . The Mo-Ru brazing alloy was obtained by mixing and milling powders in the eutectic composition with a binder, and a braze paste was applied on the surface cathode parts. Brazing was performed in two temperatures by using a resistive dry hydrogen cold wall furnace for 10 minutes: at 1890 °C and 1967 °C. It was observed a fillability by the Mo-Ru system only in the tests performed in temperatures above 1967°C. The brazed samples were analyzed by Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy. It was observed absence of microstructural defects in the interface between the tungsten porous and dense molybdenum joint. Stress-strain tests, followed by SEM analysis were performed to determine the mechanical behavior of the brazing joining. The results indicate the origin region of the cracking and show an intergranular propagation; some evidence as grain cleavage indicates a brittle failure behavior.

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Metallurgical Processing for Impregnated Thermionic Cathodes Manufacturing

2022

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“…Em seguida, na Seção 6.11, descreve-se o procedimento de caracterização físico-química dos aluminatos de bário e cálcio. Por fim, na Seção 6.12, apresenta-se as conclusões do Capítulo [50]. A síntese dos aluminatos emissores de elétrons utilizando a reação em estado sólido ocorre por meio de duas etapas principais: a moagem (homogeneização) e a pirólise.Para que haja a formação dos aluminatos, os reagentes (carbonatos de metais alcalinos terrosos e alumina) são mantidos em forno de hidrogênio por, aproximadamente, 5 horas, a uma temperatura de 1000ºC.…”

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