JPS60200434A - Cathode filament - Google Patents

Abstract

PURPOSE:To improve consumption resistance of cathode filaments by forming discharge covering layer of an electron discharge material or ion plant layer containing rare earth metal and boron on the surface of an electrode base metal in a vacuum or inactive gas atmosphere. CONSTITUTION:A thin covering layer 31 of an electron discharge material is formed on the surface of a base material 4 of a heat resistant metal, the electron discharge material bonding thereon by diffusion. As the electron discharge material, those composed of Ba, Ca, and Sr containing rare earth elements such as La, Pr, and Ce; and boron B are used. For example, a covering material tip 3 is attached to an end chuck 2 and the tip 3 facing to the base material 4 repeats touching and detaching thereto by the vibration of a vibrator 1 and the inside of an airtight vessel 6 is supplied with inactive gas from a gas cylinder 8 while being evacuated by a vacuum pump 7. Discharging occurs when the covering material tip 3 comes down close to the base material 4 and the tip material 3 melted by the discharge heat is deposited to the base material 4 and in each vibration cycle, the tip material 3 is repeatedly coated inside the base material in a partly diffused state by the discharge current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in filaments or cathode materials made of heat-resistant metal wires.

Conventionally, the surface of tungsten, which is a heat-resistant metal, is coated with oxides mainly containing electron-emitting substances such as barium, strontium, and calcium.

In order to further improve electron emission efficiency, the present invention uses a substance containing rare earth metals and boron as an electron-emitting substance, and instead of simply coating it on the surface of the base material, it is placed between the coating material and the base material. It is characterized in that it is provided to increase wear resistance by forming a coating layer that partially diffuses on the surface of the base material by performing electric discharge, or by forming a diffusion layer by ion implantation of the coating material. .

An example will be explained below. FIG. 1 is a cross-sectional view of one embodiment of the present invention, in which a thin coating layer 31 of an electron-emitting substance is formed on the surface of a heat-resistant metal base material 4 to be diffuse-bonded. As the heat-resistant metal of the base material, an electron-emitting material having a high melting point and good conductivity, such as W, Ta, PT, and lr, is used. As the electron-emitting substance coated on the surface of this base material, 1aSprXC
Contains rare earth elements such as e and boron B, 3a, Ca, 3r
consisting of pr (Ba o, s Bo, 4)
e, pr (Cao, s % Sro, r, )s
) La (BaO-3, Bo, 7) e, Ce (
Ca0.2% Sro, 4% Bo, 4>6, etc. are used.

The discharge coating means shown in FIG. 2 is used to coat the base material 4 with these electron-emitting substances 31. Reference numeral 1 denotes a vibrator, which constitutes a vibrating head, has a coating material tip 3 attached to a tip tip 2, and sets its tip so as to repeatedly contact and separate by the vibration of the vibrator 1, facing the base material 4. Reference numeral 5 denotes a pulse power source for causing discharge between the chip 3 and the base material 4.

The coating processing atmosphere is an inert gas atmosphere, so the container is surrounded by an airtight container 6, the inside of which is evacuated by a vacuum pump 7, and an inert gas is supplied from a cylinder 8. In addition, airtight container 6
A bellows 6a is provided in a part of the holder, so that vertical vibration can be freely performed.

In coating processing by electrical discharge, when the coating material chip 3 descends and approaches the base material 4, an electrical discharge occurs, and the chips melted by the discharge heat contact and weld to the base material 4, and this is repeated every vibration cycle to coat the base material. The machining process is performed by coating the base material 4 in a state where it is partially diffused by a discharge electric field, and by changing the covered portion by moving the base material 4, a coating layer 31 is formed on a predetermined portion or the entire surface of the base material 4. be able to. In the experiment, the frequency of the coating material depth 3 was vibrated at a frequency of 100 to 4001-lz,
The pulse width of the discharge power source 5 was 1 to 50 μs, and the discharge current peak value Ip was 50 to 200 A. The thickness of the coating layer is usually 10 μm or less.

The coating process can be carried out by vibrating the coating layer 3 or by rotating the coating layer 3 about an axis, thereby improving the coating effect.

In addition, it is possible to carry out an ion plant for the coating material.Ion implantation is performed by setting the atmospheric pressure to about 10 (7 orr) and discharging the coating material to generate ions, which are implanted by controlling electric field acceleration. A wire is stretched between electrodes, and the wire is melted and scattered by impact discharge to cause collision welding to the base material, or by impact welding by spraying the powder of the coating material by discharge impact. It can be coated with

Next, to explain the emission effect of the cathode material coated with the electron-emitting substance of the present invention, the radiation efficiency when heating and holding the W line at 1000°C is set as 1, as shown in the following table. Met.

In addition, both were heated to 1000°C.

Material Covering Efficiency W None 1 pr (Ba o, s, Bo, 4) s 6 pr (C
a o, s, Sr O, 4) 6 5, 31 a (B
a O, 3, 80, 7) 67.6〃 Ce(Cao,
2. Sro, 4, Bo, 4)s 8.4 as above
Extremely efficient and stable emission effects can be obtained,
Since the heating temperature in practical use is about 360°C, it was confirmed that it can be used in a sufficiently stable manner.

Further, the coating layer is bonded to the material in a state where it is partially diffused, and is strong against the impact of electrons, ions, etc., and has the effect of providing a good cathode with a long life.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway view of the present invention, and FIG. 2 is a configuration diagram of one embodiment of the coating device. 4...Base material 31...Coating layer 5-;

Claims (1)

[Claims] A cathode filament characterized in that a discharge coating layer or an ion plant layer of an electron-emitting substance containing a rare earth metal and boron is formed on the surface of an electrode base material such as tungsten in a vacuum or an inert gas atmosphere.