JPH03250527A - Manufacturing method of impregnated cathode structure - Google Patents

Abstract

PURPOSE:To remove surplus electron emitting substance remaining on the surface of each pellet, which is obtained by impregnating a porous substance with molten electron emitting substance, simply and uncostly without requiring any special post-treatment by leaving the pellet to the atmospheric condition. CONSTITUTION:An electron emitting substance, for ex. BaO.CaO.Al2O3 chiefly containing oxide remaining on the surface of each pellet is changed into hydroxide for ex. Ba(OH)2, Ca(OH), Al(OH)3 by leaving in the atmosphere. At this time, the specific gravity drops and the volume increases, and expansion at this time initiates crack, and surplus electron emitting substance exfoliates naturally from the surface of the pellet. For exfoliation, it may become necessary to apply light vibration to the pellet or give ultrasonic vibration in alcohol, but any way exfoliation is attained simply and uncostly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing an impregnated cathode structure for an electron tube, and in particular, a method for manufacturing an impregnated cathode structure for an electron tube, in particular, a method for melting and impregnating a porous material with an electron-emitting substance, followed by dissolving and cleaning or other special treatment. The present invention relates to a method for manufacturing an impregnated cathode structure, which allows an inexpensive and highly reliable cathode to be obtained without applying any oxidation.

[Prior Art] In the production of an impregnated cathode structure, there have been no special methods for removing excess electron emitting material remaining on the pellet surface after melting and impregnating a high melting point metal porous body with an electron emitting material. Kai No. 63-62127, Special Publication No. 63-4933
As described in No. 2, etc., a method of cleaning and removing the electron-emitting substance with a liquid that dissolves it, and a method of removing it by ultrasonic cleaning have been used.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned conventional technology, as seen in the above-mentioned publication, it is necessary to further perform a hydrogen treatment after the cleaning treatment, and furthermore, these treatments remove the thickness from the surface. Since the electron-emitting material disappears over a period of 20 to 60 degrees, it was necessary to remove the layer by polishing.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to easily produce an inexpensive and highly reliable cathode without requiring a special post-treatment process after melting and impregnating an electron-emitting substance. An object of the present invention is to provide a method for manufacturing an impregnated underground structure that can be obtained.

[Means for solving the problem] The above purpose is to melt and impregnate a high melting point metal porous sintered body with an electron-emitting substance and then leave the pellet in atmospheric conditions to allow the change from oxide to hydroxide to take place. This can be achieved by removing excess electron emitting material remaining on the pellet surface due to the accompanying volume expansion.

[Operation] By holding the pellet under the above conditions after the melt impregnation operation, the electron-emitting substance mainly composed of oxides (BaO-CaO.Al, O,) remaining on the pellet surface becomes hydroxide (Ba(OH) ), Ca (OH), Al (O)!
A state is reached in which excess electron-emitting material naturally peels off from the pellet surface.

As a result, the electron-emitting substance can be almost completely removed from the pellet surface by applying light vibration to the pellet or, if necessary, by immersing the pellet in alcohol and applying ultrasonic vibration.

[Example 7] The method for manufacturing an impregnated cathode structure of the present invention will be specifically explained below using examples.

FIG. 1 is a diagram showing a schematic structure of an impregnated cathode structure manufactured by the method of the present invention, in which a pellet-shaped cathode substrate is formed by impregnating a porous sintered body of a high-melting point metal such as tungsten with a substance that absorbs electrons. , a cup 2 made of a high melting point metal such as molybdenum that houses the cathode substrate 1, a sleeve 3 made of a high melting point metal such as molybdenum with the cup 2 attached to the top and having one end open, a heater 4 pushed into the sleeve 3, and these. It is shown that it is constituted by a high melting point metal thin wire, such as a rhenium tungsten wire 5, which is suspended and supported.

Next, a procedure for manufacturing pellets impregnated with an electron-emitting substance will be explained. First, a porous sintered body made by press-molding and sintering tungsten powder is placed in a cylinder made of high-melting point metal, and barium carbonate (BaCO,), calcium carbonate (CaCO,), aluminum oxide ( AI, 0.
) were mixed at a molar ratio of 4:1:1 and a molded body press-molded to the same diameter as the porous sintered body was inserted, and then heated to about 1200°C in a vacuum or in a reducing atmosphere. . As a result, the carbonate decomposes to produce oxides (Ba
d, Cab).

Next, the temperature is further raised to approximately 1800°C and held for 2 to 3 minutes, thereby melting the oxide and converting Ba-Ca.
The aluminate (4BaO-CaO-Al, O,) was impregnated into the porous sintered body, and a portion remained on the porous sintered body. The cross-sectional shape of the pellet taken out from the metal cylinder in this state is as shown in Figure 2 (a), with almost no Ba-Ca aluminate remaining on the side surfaces around the pellet, and a slight periphery on both the top and bottom surfaces of the pellet. It remained in a raised shape.

Subsequently, the pellets obtained above were heated at a temperature of 20 to 30°C.
When left in an atmosphere with a relative humidity of 50-60% for 2-5 hours, the aluminate layers on both the upper and lower surfaces of the pellets showed significant expansion, accompanied by cracks, and were removed by slight vibration. It could be completely removed from the pellet surface.

In some cases, a small amount remained on the surface of the pellet, but in this case as well, it was possible to completely remove it by immersing it in alcohol and applying ultrasonic vibration for several minutes.

In addition, a cathode structure was assembled using the pellets obtained above according to a normal process, and the cathode assembly could be manufactured without any problems, and excellent electron emission characteristics could be obtained.

Furthermore, Figures 2(b) and (C) are diagrams showing the state when a pellet is placed on a flat plate and an electron-emitting substance is placed on the pellet and heated and melted using the conventional technique, and the amount of the electron-emitting substance loaded is When there is a large amount of electron-emitting material, as shown in (b) and (C), the electron-emitting material melts and flows down to the side surfaces around the pellet, or the electron-emitting material remains on the pellet surface, and the amount of electron-emitting material loaded decreases. If it is too small, the amount of impregnation will be insufficient.

C. Effects of the Invention] As described above, by using the method of manufacturing an impregnated cathode structure as the method of the present invention, the problems of the prior art can be solved and the melt impregnation operation of an electron-emitting substance can be improved. It was possible to easily obtain an inexpensive and highly reliable impregnated cathode without requiring any special post-treatment process.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic structure of an impregnated cathode structure manufactured by the method of the present invention, and FIG. 2 is a diagram showing the state of the electron-emitting substance remaining on the pellet after the melt impregnation operation. (b) and (c) are diagrams showing the state when using the method of the prior art. DESCRIPTION OF SYMBOLS 1...Cathode base, 2...Cup, 3...Sleeve, 4...Heater, 5...Rhenium-tungsten wire, 6...Excess electron-absorbing material 1. Figure 2. Figure 149 −

Claims (1)

[Claims] 1. Attach the bottom of a cup made of a high melting point metal to the top of the cathode sleeve that includes a heater and is fixed to the cathode support, and melt and impregnate the porous sintered body of the high melting point metal with an electron-emitting substance in the cup. In manufacturing an impregnated cathode assembly for electron tubes, which is made by attaching and fixing pellets, after melting and impregnating a porous material with an electron-emitting substance, the pellets are left in atmospheric conditions to prevent the change from oxide to hydroxide. A method for manufacturing an impregnated cathode structure, characterized in that excess electron-emitting material remaining on the pellet surface is removed by the accompanying volumetric expansion.