The single crystalline lanthanum hexaboride cathodes and devices of technological purposes

Монокристалічні катоди з гексабориду лантану та електронно-променеві установки технологічного призначення
Keywords
New substances and materials Tech mining and mineral processing Mechanical engineering Rocket and space technology

Description
The National Technical University of Ukraine “Kyiv Polytechnical Institute” offer the new types of the ceramic cathode units with the monocrystalline lanthanum hexaboride emitters, the high-quality structurally perfect monocrystals of the borides of the rare-earth metals, and the directionally reinforced ceramic materials.
The monocrystalline LaB6 cathodes used in the devices of technological purpose allow to get rid of several effects of unstable operation of polycrystalline cathodes bound with a developed grid of borders of grains, geometrical and chemical heterogeneity of an issuing surface, and to increase power and spatially geometrical parameters of the electronic beams by means of use of an anisotropy of issuing properties of hexaboride lanthanum.
There are offered the original design and the original technology of manufacture of the directly heated cathode units for the Electron-probe Analysis with the emitters made of monocrystallic hexaboride lanthanum which contain metallic conductors, ceramic cores, ceramic conductors, high-temperature heaters and emitters nondetachably bound in the process of welding and soldering that provides for stability and recurrence of incandescing, emitting and spatially-geometrical characteristics from cathode to cathode both at the stage of manufacture and in the process of durable operation.
We can also produce cathodes and cathode-heating units with the hexaboride lanthanum emitters in the forms tubes, rings, rods and other articles more complicated in form using the methods of pressing (compacting) and subsequent sintering, plasma spraying and high temperature compacting of the pre-purified monocrystalline powder, and also by means of junction of the monocrystalline insertions into polycrystalline matrix.

Innovation:
Application of the monocrystalline disc cathodes with orientation of an emitting surface (100) in the installations of welding without change of design, incandescing and spatially geometrical parameters of an electronic cannon allows:
• to increase up to 2-2,5 times the period of service of the cathodes in comparison with the polycrystalline hot-pressed cathodes;
• to increase up to 20-30% the electronic beam’s reserve in current;
• to reduce diameter of the beam and ensure stability of its geometrical dimensions in all range of changes of the parameters of the focusing devices of the electronic cannon;
• to increase the depth of fusion at the expense of increase of the specific power of the electronic beam for 20-25%;
• to reduce a heat load upon the constructional elements of the cathode unit and the cannon at large;
• to increase stability of a current and transversal diameter of electronic beam;
• to reduce thermal tensions in the welded material;
• to increase stability of the geometrical sizes and forms of a juncture.

Problem solved:
Improving productivity of the equipment due to a more long period of continuous operation of electron-beam devices between cathode substitutions. Improving machining accuracy due to more stable emission and spatial geometric characteristics. Improving energy efficiency of equipment due to usind of single-crystal cathodes with (001) orientation, which has the lowest work function of electrons.

Development status:
Development complete with proven results

Potential customers:
Companies in the field of mechanical engineering and metal processing of Ukraine (Motor Sich, Yuzhmash, ZAZ-Daewoo, Zorya-Mashproekt; Research plant of welding equipment, welding consumables Research Plant, Research Plant of special electric metallurgy of Paton’s Electric Welding Institute of NAS of Ukraine, SELMI, SEO) and foreign companies producers and consumers of electron-beam equipment.

Alternative range of application:
Ecology;
Medicine:
• tomography,
• pharmacology,
• manufacturing of isotopes;