A method for preparing a plasma source using oxide cathode emitting plasma

Abstract

The present invention discloses a method for preparing a plasma source with an oxide cathode emission paste. It includes that after ternary alkaline earth metal carbonates are proportioned, they are mixed with an organic solvent and a binder to form an oxide cathode emission paste, which is automatically sprayed on a cathode base metal. In the ternary carbonate, barium carbonate BaCO3 and strontium carbonate SrCO3 are proportioned at a molar ratio of 1:1, and calcium carbonate CaCO3 with a total mass of 5%-10% is added. The emission paste solvent is an organic solvent such as acetone and isoamyl acetate, and the binder is an organic macromolecule polymer such as cellulose acetate butyrate. The chemical purity of all materials and solvents is 99.99%. The present invention has the advantages that the viscosity of the emission paste is moderate and easy for automatic spraying, the cathode coating is uniform, and no harmful gases are generated during thermal decomposition.

Description

Technical Field

[0001] The invention relates to a method for preparing a plasma source by emitting plasma from an oxide cathode, and belongs to the technical field of hot cathode plasma. Background Art

[0002] The emission materials of oxide cathodes are alkaline earth metal oxides, but they cannot exist stably in the atmosphere and must be produced by decomposing alkaline earth metal carbonates or hydroxides at high temperatures. In the vacuum environment of actual applications, the carbon dioxide CO2 produced by the decomposition of carbonates is easier to be pumped away than the water vapor H2O produced by the decomposition of hydroxides, and will not affect the oxide cathode.

[0003] Among alkaline earth metal oxides, barium oxide BaO has the lowest work function and is a good emission material, but it evaporates in large quantities at high temperatures and is easily sintered to form (BaO·BaCO3). Adding SrO to the emission material can inhibit the sintering of the oxide cathode coating, reduce the work function, and improve the emission capability. When using an oxide cathode source, ion bombardment of the cathode will cause the coating to sputter and become thinner, resulting in a decrease in emission capability and uneven emission. Adding CaCO3 to the emission material can improve the bombardment resistance of the oxide cathode. Commonly used emission materials are composed of ternary carbonates (barium carbonate, calcium carbonate, and strontium carbonate). Depending on the ratio, the work function and emission capability are different. Compared with traditional hot cathodes, the emission capability has been greatly improved.

[0004] In order to ensure a good combination of oxide cathode emission materials and base metals, in addition to industrial methods such as plasma coating and surge coating, it is a better choice to configure the oxide cathode emission materials into viscous emission slurry spraying. The adhesives used in traditional emission slurry configuration include polymethacrylate resin and nitrocellulose solution, which are highly toxic. The commonly used nitrocellulose solution (collodion solution) is also a flammable and explosive item, and the state has ordered a ban on its circulation and use. At the same time, the molecular weight of nitrocellulose is too large, which is easy to clog the spray gun, and the coating surface is rough and the uniformity is poor. The decomposition formula is as follows, which will produce byproducts such as nitric oxide NO that destroy the oxide cathode.

[0005] C 12 H 17 (ONO2)3O7~C 12 H 14 (ONO2)6O7→NO+CO+CO2+H2O+N2+C

[0006] Acetate butyrate fiber itself is used as a leveling agent and film-forming material for various coatings, and its molecular formula is C4H8O2XC2H4O2X, containing acetyl and butyryl groups. In the present invention, acetate butyrate fiber is used as an adhesive, and the oxide cathode emission slurry, in addition to alkaline earth metals, only includes three elements, C, H, and O, which can be fully decomposed by heating, and the product has no adverse effect on the oxide cathode; at the same time, the emission slurry has moderate viscosity, is easy to dissolve, and has a smooth coating with good uniformity, which is suitable for large-area automatic spraying. Summary of the invention

[0007] The invention provides a method for preparing a plasma source by using oxide cathode emission slurry. The method adopts a novel adhesive and a preparation method, thereby improving the uniformity of oxide cathode emission and the working environment of the oxide cathode.

[0008] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0009] A method for preparing a plasma source from oxide cathode emission slurry comprises: mixing ternary alkaline earth metal carbonate, organic solvent and adhesive to form oxide cathode emission slurry, and coating the mixture on cathode base metal.

[0010] Furthermore, the ternary carbonate is barium carbonate, strontium carbonate and calcium carbonate, wherein the molar ratio of barium carbonate to strontium carbonate is 1:0.98-1:1.02.

[0011] Furthermore, based on the total mass of barium carbonate, strontium carbonate and calcium carbonate, the mass percentage of calcium carbonate CaCO3 is 5%-10%.

[0012] For example, based on the total mass of barium carbonate, strontium carbonate and calcium carbonate, the mass percentage of calcium carbonate CaCO3 is 5%, 6%, 7%, 8%, 9% or 10%.

[0013] Furthermore, the molar ratio of barium carbonate to strontium carbonate is 1:1.

[0014] Furthermore, the organic solvent is selected from one or more of acetone, ethyl acetate, amyl acetate and isoamyl acetate.

[0015] Furthermore, the adhesive comprises an organic macromolecular polymer; preferably, the adhesive comprises cellulose acetate butyrate.

[0016] Furthermore, the method comprises the following steps:

[0017] a. Mixing barium carbonate, strontium carbonate and calcium carbonate to prepare a ternary carbonate;

[0018] b. The adhesive is prepared by dissolving 1 g of cellulose acetate butyrate solid particles in 5-15 mL of acetone;

[0019] c. Grind the organic solvent and ternary carbonate in a grinding device for 10-15 hours to obtain a particle size of 1-3 μm, then add the configured adhesive and continue grinding and stirring to obtain a launch slurry in the form of a suspension;

[0020] d. Polish and clean the surface of the base metal, level the base metal, and then grind the surface of the base metal to make it rough;

[0021] e. Start the two-dimensional mobile automatic spraying equipment, scan line by line and spray the emission slurry evenly on the base metal plate;

[0022] f. Start the baking lamp under the material rack to dry the coating;

[0023] g. Repeat steps e and f to obtain a slurry coating with a thickness of 60-150 μm.

[0024] Furthermore, in step c, 2-3 mL of a mixed solution of an adhesive and an organic solvent is used for every 1 g of ternary carbonate.

[0025] Furthermore, in step c, in the emission slurry prepared with ternary carbonate, organic solvent and adhesive, the final content of cellulose acetate butyrate as an adhesive component is 0.02g-0.15g per 1mL, preferably, 0.04g-0.08g per 1mL.

[0026] Specifically, a method for preparing a plasma source from an oxide cathode emission slurry comprises preparing a ternary alkaline earth metal carbonate in proportion, mixing it with an organic solvent and an adhesive to prepare an oxide cathode emission slurry, and automatically spraying it on a cathode base metal. In the ternary carbonate, barium carbonate BaCO3 and strontium carbonate SrCO3 are prepared in a molar ratio of 1:1, and calcium carbonate CaCO3 is added at a total mass of 5%-10%.

[0027] The method for preparing an oxide cathode plasma source comprises the following steps:

[0028] a. According to the above ternary alkaline earth metal carbonate ratio configuration barium carbonate BaCO3, strontium carbonate SrCO3, calcium carbonate CaCO3 powder;

[0029] b. Prepare an adhesive in a beaker at a ratio of 1 g of cellulose acetate butyrate solid particles dissolved in 5-15 mL of acetone, add a magnetic rod, seal the beaker, and stir with a magnetic stirrer for 10-15 minutes until fully dissolved and no particles are visible;

[0030] c. Put ethyl acetate, amyl acetate, isoamyl acetate or acetone and other organic solvents into a planetary ball mill and grind for 10-15 hours, the particle size is 1-3 μm, then add the prepared adhesive and continue grinding and stirring for 1 hour to obtain a slurry in the form of a suspension. 1g of ternary carbonate corresponds to 2-3mL of a mixed solution of adhesive and organic solvent, and 1mL of the mixed solution contains 0.02g-0.15g of cellulose acetate butyrate, preferably, 0.04g-0.08g per 1mL.

[0031] d. Use corundum sandpaper to polish and clean the surface of the base metal, use a pressure plate to level the base metal, and then use coarse corundum sandpaper to roughen the surface of the base metal;

[0032] e. Load the emission slurry into the material tank of the paint spraying system, fix the base metal plate on the material rack, start the two-dimensional mobile automatic spraying equipment, scan line by line to spray the emission slurry evenly on the base metal plate;

[0033] f. Start the baking lamp under the material rack to dry the coating;

[0034] g. Repeat steps e and f, and use a film thickness gauge to measure the thickness of the emission slurry coating to reach 60-150 μm.

[0035] The beneficial effects of the present invention are as follows: the present invention uses a cellulose acetate butyrate solution of an appropriate proportion as a binder for the oxide cathode, has the advantages of moderate viscosity of the emission slurry, is suitable for large-area automatic spraying, has a uniform and smooth cathode coating, is firmly bonded, and is not prone to ignition and separation. In addition to alkaline earth metal elements, the entire emission slurry preparation material contains only three elements: carbon C, hydrogen H, and oxygen O, and does not generate gas components that affect the performance of the oxide cathode during the activation process of the oxide cathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of automatically spraying emission slurry to prepare an oxide cathode;

[0037] In the figure, 1-paint spraying system, 2-material rack, 3-two-dimensional moving platform, 4-cathode base metal.

[0038] Figure 2 It is the result of the residual gas analyzer measuring the gas composition during the activation process of the oxide cathode. DETAILED DESCRIPTION

[0039] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. However, the following embodiments are limited to explaining the present invention, and the protection scope of the present invention should include the entire contents of the claims, and through the description of the following embodiments, those skilled in the art can fully realize the entire contents of the claims of the present invention.

[0040] A method for preparing a plasma source from an oxide cathode emission slurry comprises preparing a ternary alkaline earth metal carbonate in proportion, mixing it with an organic solvent and an adhesive to prepare an oxide cathode emission slurry, and automatically spraying it on a cathode base metal. In the ternary carbonate, barium carbonate BaCO3 and strontium carbonate SrCO3 are prepared in a molar ratio of 1:1, and calcium carbonate CaCO3 is added in an amount of 5%-10% of the total mass of the ternary carbonate.

[0041] Figure 1 This is a schematic diagram of automatically spraying emission slurry to prepare oxide cathode, such as Figure 1 As shown, the cathode base metal 4 is placed horizontally at the center of the material rack 2; the two-dimensional mobile platform 3 is composed of three groups of stepper motor screw slides, two of which are bolted parallel to the material rack 2, and the two ends of the remaining group are bolted on the slides of the first two groups, forming an "H"-shaped structure as a whole. The stepper motor rotates the screw to drive the slide to move, and the left and right groups control the forward and backward movement, and the middle group of slides controls the left and right movement; the paint spraying system 1 includes a spray gun, a material tank and a high-pressure gas cylinder. The spray gun and the material tank are fixed on the central slide of the two-dimensional mobile platform 3 with a clamp, and the spray gun muzzle points directly downward. The high-pressure gas cylinder uses an air pipe to supply gas to the spray gun, and the spray gun is controlled by an electromagnetic valve. The stepper motor of the two-dimensional mobile platform 3 and the electromagnetic valve of the paint spraying system 1 are controlled by a program. After the prepared oxide cathode emission slurry is loaded into the material tank, automatic spraying on the cathode base metal 4 line by line can be achieved.

[0042] In the following examples, the chemical purity of all materials and solvents was 99.99%.

[0043] Example 1

[0044] According to a preferred embodiment, the method for preparing an oxide cathode plasma source comprises the following steps:

[0045] a. 212g of barium carbonate BaCO3, 156g of strontium carbonate SrCO3 and 32g of calcium carbonate CaCO3 powder were mixed to obtain 400g of ternary carbonate powder;

[0046] b. 100 g of cellulose acetate butyrate (brand name: Aladdin, butyryl 30-35%, Mn ~ 12,000) solid particles were added to a beaker, and then 1 L of acetone was added to the beaker, a magnetic son was placed, the beaker was sealed, and stirred with a magnetic stirrer for 10-15 minutes until the cellulose acetate butyrate solid particles were fully dissolved and no particles were visible, thereby obtaining an adhesive;

[0047] c. 600 mL of isoamyl acetate as an organic solvent and 400 g of the ternary carbonate powder obtained in step a were placed in a 3L grinding jar and ground with a planetary ball mill for 14 hours. The average size of the resulting particles was about 2 μm. Then 600 mL of the adhesive prepared in step b was added and continued grinding and stirring for 1 hour to obtain a launch slurry in the form of a suspension.

[0048] d. Use 120-mesh corundum sandpaper to polish and clean the surface of the base metal nickel N4, use a pressure plate to level the base metal, and then use 60-mesh corundum sandpaper to roughen the surface of the base metal;

[0049] e. Load the emission slurry into the paint spraying system 1 tank, fix the base metal plate on the rack 2, start the two-dimensional mobile automatic spraying equipment, scan line by line to spray the emission slurry evenly on the base metal plate;

[0050] f. Start the baking lamp under the material rack to dry the coating;

[0051] g. Repeat steps e and f, and use a thin film thickness gauge to measure the thickness of the emission slurry coating to about 100 μm.

[0052] like Figure 2 As described above, the residual gas analyzer measures that the gas components during the activation of the oxide cathode are mainly groups with relative molecular masses of 18, 31, and 46, which are water (H2O), methanol (CH2OH), and ethanol (C2H5OH), respectively. Therefore, during the activation process, only substances containing elements such as carbon C, hydrogen H, and oxygen O are produced, and no byproducts such as nitric oxide (NO) that are highly oxidizing and destroy the oxide cathode are produced.

[0053] The present invention does not elaborate on the parts that belong to the known technology of those skilled in the art. The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection claimed in the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a plasma source by using an oxide cathode emitting plasma, characterized in that: The method comprises: mixing ternary alkaline earth metal carbonate, organic solvent and adhesive to form oxide cathode emission slurry, and coating the mixture on cathode base metal; the ternary alkaline earth metal carbonate comprises barium carbonate, strontium carbonate and calcium carbonate, wherein the molar ratio of barium carbonate to strontium carbonate is 1:0.98-1:1.02; based on the total mass of barium carbonate, strontium carbonate and calcium carbonate, the mass percentage of calcium carbonate CaCO3 is 5%-10%; and the adhesive comprises acetate butyrate fiber.

2. The method according to claim 1, characterized in that The molar ratio of barium carbonate to strontium carbonate is 1:

1.

3. The method according to claim 1, characterized in that: The organic solvent is selected from one or more of acetone, ethyl acetate, amyl acetate and isoamyl acetate.

4. The method according to any one of claims 1 to 3, characterized in that: The steps include: a. mixing barium carbonate, strontium carbonate and calcium carbonate to obtain a ternary alkaline earth metal carbonate; b. The adhesive is prepared by dissolving 1 g of cellulose acetate butyrate solid particles in 5-15 mL of acetone; c. Grind the organic solvent and the ternary alkaline earth metal carbonate in a grinding device for 10-15 hours to obtain a particle size of 1-3 μm, then add the configured adhesive and continue grinding and stirring to obtain a launch slurry in the form of a suspension; d. Polish and clean the surface of the base metal, level the base metal, and then grind the surface of the base metal to make it rough; e. Start the two-dimensional mobile automatic spraying equipment, scan line by line and spray the emission slurry evenly on the base metal plate; f. Start the baking lamp under the material rack to dry the coating; g. Repeat steps e and f to obtain a slurry coating with a thickness of 60-150 μm.

5. The method according to claim 4, characterized in that In step c, 2-3 mL of a mixed solution of a binder and an organic solvent is used for every 1 g of the ternary alkaline earth metal carbonate.

6. The method according to claim 4, characterized in that In step c, in the emission slurry prepared by ternary alkaline earth metal carbonate, organic solvent and adhesive, the final content of cellulose acetate butyrate as an adhesive component is 0.02g-0.15g per 1mL.

7. The method according to claim 4, characterized in that In step c, in the emission slurry prepared by ternary alkaline earth metal carbonate, organic solvent and adhesive, the final content of cellulose acetate butyrate as an adhesive component is 0.04g-0.08g per 1mL.

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