A binder for producing a molybdenum end cap, a preparation method and application thereof

Abstract

The application discloses a kind of molybdenum end cap production binders and preparation method and application, it is related to molybdenum end cap field.A kind of molybdenum end cap production binders, by including the following mass parts of raw materials is prepared: polyvinyl alcohol 5-10 parts;Polyvinylpyrrolidone 2-5 parts;Sodium carboxymethylcellulose 0.5-2 parts;Lubricant 1-3 parts;Dispersing agent 1-3 parts;Deionized water 90-120 parts.The application has the effect of improving the uniformity of particle size and particle strength of molybdenum powder after binder modification, improves the stability of molybdenum end cap product.

Description

Technical Field

[0001] This invention relates to the field of molybdenum end caps, and in particular to an adhesive for the production of molybdenum end caps, its preparation method, and its application. Background Technology

[0002] A magnetron is an electric vacuum device used to generate microwave energy. It is the core heating component in equipment such as microwave ovens and can also be used in radar generators. A magnetron mainly consists of five components: cathode, anode, energy coupling device, magnetic circuit, and tuning device. The cathode assembly, composed of a spiral thorium-tungsten cathode and a molybdenum support, is the electron source that maintains the generation of electrons in the magnetron and sustains the continuous oscillation of electrons. The molybdenum end cap is an important component of the cathode assembly.

[0003] The molybdenum end cap consists of an upper cap and a lower cap, with the two ends of the magnetron microwave transmitting coil welded to the upper and lower caps respectively. The molybdenum end cap is obtained by mixing molybdenum powder and a binder, spray granulation, pressing, and sintering. The binder increases powder flowability and maintains product shape. Currently, the binder used is a system composed of polyvinyl butyral (PVB), paraffin wax, and ethanol, which modifies the molybdenum powder, increasing the particle size and improving its flowability.

[0004] When a binder system consisting of polyvinyl butyral, paraffin, and ethanol is used, the modified molybdenum powder will have different particle sizes and strengths, resulting in significant differences in the performance of molybdenum powder produced in different batches and poor product stability of the produced molybdenum end caps. Summary of the Invention

[0005] In order to improve the uniformity of particle size and particle strength of molybdenum powder after binder modification and improve the stability of molybdenum end cap products, this application provides a binder for the production of molybdenum end caps, its preparation method and application.

[0006] This application provides an adhesive for the production of molybdenum end caps, its preparation method, and its application, employing the following technical solution:

[0007] An adhesive for producing molybdenum end caps is prepared from raw materials comprising the following parts by weight:

[0008] 5-10 parts of polyvinyl alcohol;

[0009] 2-5 parts of polyvinylpyrrolidone;

[0010] Sodium carboxymethyl cellulose 0.5-2 parts;

[0011] 1-3 parts lubricant;

[0012] 1-3 parts dispersant;

[0013] 90-120 parts of deionized water.

[0014] By adopting the above technical solution, polyvinyl alcohol, polyvinylpyrrolidone, and sodium carboxymethyl cellulose are selected for cross-linking to form a uniform film on the surface of molybdenum powder. At the same time, the dispersant promotes the uniform dispersion of the binder system, and the addition of lubricant plays a lubricating role during the pressing of molybdenum powder, reducing friction and enhancing the adhesion between molybdenum powder particles, thereby improving the particle strength and flowability of molybdenum powder. By compounding with sodium carboxymethyl cellulose, the loose density of molybdenum powder particles can be increased, which is conducive to the normal distribution of molybdenum powder particle size, thus making the performance of molybdenum powder particles more uniform and the stability of molybdenum end cap products higher.

[0015] Optionally, the sodium carboxymethyl cellulose is selected from sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid, which is prepared from the following raw materials in parts by weight: 12-15 parts of 2-acrylamido-2-methylpropanesulfonic acid.

[0016] Sodium carboxymethyl cellulose 1.5-2.5 parts;

[0017] Initiator 0.05-0.1 parts;

[0018] Crosslinking agent 0.08-0.15 parts.

[0019] By adopting the above technical solution, 2-acrylamido-2-methylpropanesulfonic acid is selected to graft and modify sodium carboxymethyl cellulose, which makes sodium carboxymethyl cellulose more compatible with polyvinyl alcohol and polyvinylpyrrolidone. Furthermore, longer polymer chains are introduced into the binder system, which further promotes the cross-linking and bridging effect of the binder, thereby enhancing the hydrogen bonding and adhesion of molybdenum powder particles, thus further improving particle strength and resulting in better strength and mechanical properties of molybdenum end cap products.

[0020] Optionally, the lubricant may be one or more of glycerin, sodium stearate, and emulsified wax.

[0021] By adopting the above technical solution, adding lubricant can play a lubricating role in the pressing process, reducing friction between molybdenum powder particles and between molybdenum powder and the mold wall, which is beneficial to improving the density and strength of the pressed blank.

[0022] Optionally, the dispersant is selected from one or more of polyethylene glycol, sodium tripolyphosphate, and sodium hexadecyl sulfate.

[0023] By adopting the above technical solution, the use of a dispersant can improve the dispersibility of molybdenum powder in the binder, which is beneficial for the binder to effectively and uniformly coat the surface of the molybdenum powder.

[0024] Optionally, the lubricant is sodium stearate, and the dispersant is a mixture of polyethylene glycol 2000 and polyethylene glycol 800, with a mass ratio of polyethylene glycol 2000 to polyethylene glycol 800 of (0.6-0.8):(1.2-1.4).

[0025] By adopting the above technical solution, and using a compound of sodium stearate, polyethylene glycol 2000 and polyethylene glycol 800, the fluidity and formability of molybdenum powder can be further improved. The pressed compact obtained during the pressing process has higher strength, higher particle uniformity, and higher loose density.

[0026] Optionally, the polyvinyl alcohol has an average degree of polymerization of 1000-1500 and a degree of alcoholysis of 85%-95%.

[0027] By adopting the above technical solution, polyvinyl alcohol with an average degree of polymerization of 1000-1500 and a degree of hydrolysis of 85-95% exhibits better adhesive performance.

[0028] Secondly, this application provides a method for preparing an adhesive for producing molybdenum end caps, comprising the following steps:

[0029] Mix deionized water, dispersant and lubricant evenly and stir thoroughly for 0.5-1h to obtain a mixture. Heat the mixture to 60-80℃, add polyvinyl alcohol and polyvinylpyrrolidone to the mixture, stir for 20-30min, and maintain constant temperature stirring. Slowly add sodium carboxymethyl cellulose to the mixture, and obtain the binder after cooling.

[0030] By adopting the above technical solution, the raw materials are evenly dispersed in deionized water through stirring and heating, followed by the addition of polyvinyl alcohol and polyvinylpyrrolidone, which shortens the stirring time of the adhesive and thus maintains the bonding strength of the adhesive.

[0031] Optionally, when sodium carboxymethyl cellulose is selected from sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid, it is prepared by the following steps:

[0032] Weigh 2-acrylamido-2-methylpropanesulfonic acid into a reactor, add distilled water to dissolve it, add sodium hydroxide aqueous solution to neutralize to pH 6.5-7, add sodium carboxymethyl cellulose, and after complete dissolution, add initiator and crosslinking agent, stir evenly, and place in a microwave reactor. React for 5-10 minutes, remove the reactant and place it in an oven to dry at 80-90℃ to constant weight, soak and wash with distilled water, filter and dry, and pulverize to obtain sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid.

[0033] By adopting the above technical solution, 2-acrylamido-2-methylpropanesulfonic acid is crosslinked with sodium carboxymethyl cellulose under the action of initiator and crosslinking agent, thereby achieving the modification of sodium carboxymethyl cellulose.

[0034] Thirdly, this application provides a method for preparing a molybdenum end cap, using any of the above-described adhesives for producing molybdenum end caps, the specific steps of which include:

[0035] The raw molybdenum powder and binder are mixed evenly and then wet-milled in a ball mill jar to prepare a molybdenum powder slurry.

[0036] The molybdenum powder slurry is spray-dried and granulated, and the granulated molybdenum powder is collected.

[0037] Granulated molybdenum powder is filled into the mold cavity and then pressed to form a molybdenum end cap compact.

[0038] The binder is removed by heating the molybdenum end cap compact, and then sintered at high temperature to obtain the molybdenum end cap sintered compact.

[0039] The molybdenum end cap sintered blank is polished and hydrogen-burned to obtain the molybdenum end cap product.

[0040] By adopting the above technical solution, a molybdenum end cap product with high strength and stable performance can be obtained through simple operation.

[0041] Optionally, the raw material molybdenum powder has a mass fraction of 94-98 parts, the raw material molybdenum powder has a Fisher particle size of 3-3.5 μm, and the binder has a mass fraction of 2-6 parts.

[0042] By adopting the above technical solution, the strength of the green body is guaranteed by controlling the amount of raw material molybdenum powder and binder, and there are no molybdenum powder shell agglomerates.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. Polyvinyl alcohol, polyvinylpyrrolidone, and sodium carboxymethyl cellulose are selected for cross-linking to form a uniform film on the surface of molybdenum powder. At the same time, the dispersant promotes the uniform dispersion of the binder system, and the addition of lubricant plays a lubricating role during the pressing of molybdenum powder, reducing friction and enhancing the adhesion between molybdenum powder particles, thereby improving the particle strength and flowability of molybdenum powder. By compounding with sodium carboxymethyl cellulose, the loose density of molybdenum powder particles can be increased, which is conducive to the normal distribution of molybdenum powder particle size, thus making the performance of molybdenum powder particles more uniform and the stability of molybdenum end cap products higher.

[0045] 2. 2-Acrylamido-2-methylpropanesulfonic acid was selected to graft and modify sodium carboxymethyl cellulose, which improved the compatibility of sodium carboxymethyl cellulose with polyvinyl alcohol and polyvinylpyrrolidone, and introduced longer polymer chains into the binder system, further promoting the cross-linking and bridging effect of the binder. This enhanced the hydrogen bonding and adhesion of molybdenum powder particles, thereby further improving the particle strength and resulting in better strength and mechanical properties of the molybdenum end cap product. Detailed Implementation

[0046] The present application will be further described in detail below with reference to Examples 1-8 and Comparative Examples 1-2.

[0047] Preparation Example

[0048] Preparation Example 1

[0049] Preparation of sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid

[0050] Weigh 12g of 2-acrylamido-2-methylpropanesulfonic acid into a reactor, add 30g of distilled water and stir until completely dissolved. Under cold water cooling, add a 25% sodium hydroxide aqueous solution to the reactor to neutralize to pH 6.5. Add 1.5g of sodium carboxymethyl cellulose to the reactor and dissolve completely. Then add 0.05g of potassium persulfate and 0.08g of N,N-methylenebisacrylamide. Stir well and place in a microwave reactor. After reacting for 5 minutes, a transparent colloid is produced. Place the colloid in an oven and dry at 80℃ to constant weight. Soak and wash with distilled water, filter, dry and pulverize to obtain sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid.

[0051] Preparation Example 2

[0052] Preparation of sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid

[0053] Weigh 15g of 2-acrylamido-2-methylpropanesulfonic acid into a reactor, add 50g of distilled water and stir until completely dissolved. Under cold water cooling, add a 25% sodium hydroxide aqueous solution to the reactor to neutralize to pH=7. Add 2.5g of sodium carboxymethyl cellulose to the reactor and dissolve completely. Then add 0.1g of potassium persulfate and 0.15g of N,N-methylenebisacrylamide. Stir well and place in a microwave reactor. After reacting for 10 minutes, a transparent colloid is produced. Place the colloid in an oven and dry at 90℃ to constant weight. Soak and wash with distilled water, filter, dry and pulverize to obtain sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid.

[0054] Example

[0055] Example 1

[0056] Preparation of an adhesive for the production of molybdenum end caps

[0057] Mix 90g of deionized water, 1g of polyethylene glycol 2000 and 1g of glycerin evenly and stir thoroughly for 0.5h to obtain a mixture. Heat the mixture to 60℃, add 5g of polyvinyl alcohol and 2g of polyvinylpyrrolidone to the mixture, stir for 20min, and maintain a constant temperature while stirring. Slowly add 0.5g of sodium carboxymethyl cellulose to the mixture, stir evenly, and cool to obtain the binder.

[0058] The average degree of polymerization of polyvinyl alcohol is 1000, and the degree of alcoholysis is 85%.

[0059] The molecular weight of polyvinylpyrrolidone is 20,000 g / mol.

[0060] Example 2

[0061] Preparation of an adhesive for the production of molybdenum end caps

[0062] Mix 120g of deionized water, 3g of sodium tripolyphosphate and 3g of emulsified wax evenly and stir thoroughly for 0.5h to obtain a mixture. Heat the mixture to 60℃, add 10g of polyvinyl alcohol and 5g of polyvinylpyrrolidone to the mixture, stir for 20min, and maintain a constant temperature while stirring. Slowly add 2g of sodium carboxymethyl cellulose to the mixture, stir evenly, and cool to obtain the binder.

[0063] The average degree of polymerization of polyvinyl alcohol is 1500, and the degree of alcoholysis is 95%.

[0064] The molecular weight of polyvinylpyrrolidone is 50,000 g / mol.

[0065] Example 3

[0066] Preparation of an adhesive for the production of molybdenum end caps

[0067] Mix 100g of deionized water, 2g of sodium hexadecyl sulfate and 2g of sodium stearate evenly and stir thoroughly for 0.5h to obtain a mixture. Heat the mixture to 60℃, add 8g of polyvinyl alcohol and 3g of polyvinylpyrrolidone to the mixture, stir for 20min, and maintain a constant temperature while stirring. Slowly add 1g of sodium carboxymethyl cellulose to the mixture, stir evenly, and cool to obtain the binder.

[0068] The average degree of polymerization of polyvinyl alcohol is 1200, and the degree of alcoholysis is 90%.

[0069] The molecular weight of polyvinylpyrrolidone is 35000 g / mol.

[0070] Example 4

[0071] The difference between this embodiment and Embodiment 1 is that the dispersant and lubricant in the binder raw materials are different.

[0072] In this embodiment, the dispersant is a mixture of polyethylene glycol 2000 and polyethylene glycol 800, wherein 0.3g of polyethylene glycol 2000 and 0.7g of polyethylene glycol 800 are used, and sodium stearate is used as the lubricant.

[0073] The preparation method of the adhesive is the same as in Example 1.

[0074] Example 5

[0075] The difference between this embodiment and Embodiment 1 is that the dispersant and lubricant in the binder raw materials are different.

[0076] In this embodiment, the dispersant is a mixture of polyethylene glycol 2000 and polyethylene glycol 800, wherein 0.4g of polyethylene glycol 2000 and 0.6g of polyethylene glycol 800 are used, and sodium stearate is used as the lubricant.

[0077] The preparation method of the adhesive is the same as in Example 1.

[0078] Example 6

[0079] The difference between this embodiment and Embodiment 1 is that the sodium carboxymethyl cellulose in the binder raw material is different.

[0080] In this embodiment, the sodium carboxymethyl cellulose used is the 2-acrylamido-2-methylpropanesulfonic acid-grafted sodium carboxymethyl cellulose obtained in Preparation Example 1.

[0081] The preparation method of the adhesive is the same as in Example 1.

[0082] Example 7

[0083] The difference between this embodiment and Embodiment 1 is that the sodium carboxymethyl cellulose in the binder raw material is different.

[0084] In this embodiment, the sodium carboxymethyl cellulose used is the 2-acrylamido-2-methylpropanesulfonic acid-grafted sodium carboxymethyl cellulose obtained in Preparation Example 2.

[0085] The preparation method of the adhesive is the same as in Example 1.

[0086] Example 8

[0087] The difference between this embodiment and Embodiment 1 is that the dispersant, lubricant, and sodium carboxymethyl cellulose in the binder raw materials are different.

[0088] In this embodiment, the sodium carboxymethyl cellulose is the 2-acrylamido-2-methylpropanesulfonic acid-grafted sodium carboxymethyl cellulose obtained in Preparation Example 1, the dispersant is a mixture of polyethylene glycol 2000 and polyethylene glycol 800, wherein 0.4g of polyethylene glycol 2000 and 0.6g of polyethylene glycol 800 are used, and the lubricant is sodium stearate.

[0089] The preparation method of the adhesive is the same as in Example 1.

[0090] Comparative Example

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that sodium carboxymethyl cellulose was not added to the binder raw materials.

[0093] The preparation method of the adhesive is the same as in Example 1.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that polyvinylpyrrolidone was not added to the adhesive raw materials.

[0096] The preparation method of the adhesive is the same as in Example 1.

[0097] Application examples

[0098] Application Example 1

[0099] Preparation of a molybdenum end cap

[0100] Weigh 940g of raw molybdenum powder with a Fisher particle size of 3μm and mix it evenly with 20g of the binder prepared in Example 1. Add the mixture to a spherical ink tank, add grinding balls and wet grind for 8 hours to prepare a molybdenum powder slurry.

[0101] The molybdenum powder slurry was spray-dried and granulated using a centrifugal spray granulator with the following settings: the feed disc speed was 11000 r / min, the inlet air temperature was 220℃, and the outlet air temperature was 130℃.

[0102] After spray granulation, the powder particles are screened through a double-layer sieve, first through a 120-mesh sieve and then through a 300-mesh sieve to obtain granulated molybdenum powder; the granulated molybdenum powder is then filled into the mold cavity and pressed into a molybdenum end cap compact.

[0103] The molybdenum end cap blank was placed in a vacuum degreasing furnace for pre-firing, and the binder was removed at 600℃. Then it was placed in a high-temperature sintering furnace for sintering for 6 hours at a sintering temperature of 1600℃ to obtain the molybdenum end cap sintered blank.

[0104] The sintered molybdenum end cap blank was polished in a polishing machine and then subjected to hydrogen burning treatment at 1150℃ for 50 minutes in a hydrogen atmosphere to obtain the molybdenum end cap product.

[0105] Application Example 2

[0106] Preparation of a molybdenum end cap

[0107] Weigh 980g of raw molybdenum powder with a Fisher particle size of 3.5μm and mix it evenly with 60g of the binder prepared in Example 2. Add the mixture to a spherical ink tank, add grinding balls and wet grind for 10 hours to prepare a molybdenum powder slurry.

[0108] The molybdenum powder slurry was spray-dried and granulated using a centrifugal spray granulator with the following settings: the feed disc speed was 12000 r / min, the inlet air temperature was 230℃, and the outlet air temperature was 135℃.

[0109] After spray granulation, the powder particles are screened through a double-layer sieve, first through a 120-mesh sieve and then through a 300-mesh sieve to obtain granulated molybdenum powder; the granulated molybdenum powder is then filled into the mold cavity and pressed into a molybdenum end cap compact.

[0110] The molybdenum end cap blank was placed in a vacuum degreasing furnace for pre-firing, and the binder was removed at 800℃. Then it was placed in a high-temperature sintering furnace for sintering for 8 hours at a sintering temperature of 1700℃ to obtain the molybdenum end cap sintered blank.

[0111] The sintered molybdenum end cap blank was polished in a polishing machine and then subjected to hydrogen burning treatment at 1250℃ for 70 minutes in a hydrogen atmosphere to obtain the molybdenum end cap product.

[0112] Application Example 3

[0113] Preparation of a molybdenum end cap

[0114] Weigh 960g of raw molybdenum powder with a Fisher particle size of 3.2μm and mix it evenly with 40g of the binder prepared in Example 3. Add the mixture to a spherical ink tank, add grinding balls and wet grind for 9 hours to prepare a molybdenum powder slurry.

[0115] The molybdenum powder slurry was spray-dried and granulated using a centrifugal spray granulator with the following settings: the feed disc speed was 11,500 r / min, the inlet air temperature was 225℃, and the outlet air temperature was 130℃.

[0116] After spray granulation, the powder particles are screened through a double-layer sieve, first through a 120-mesh sieve and then through a 300-mesh sieve to obtain granulated molybdenum powder; the granulated molybdenum powder is then filled into the mold cavity and pressed into a molybdenum end cap compact.

[0117] The molybdenum end cap blank was pre-fired in a vacuum degreasing furnace, the binder was removed at 700℃, and then it was sintered in a high-temperature sintering furnace for 7 hours at a sintering temperature of 1650℃ to obtain the molybdenum end cap sintered blank.

[0118] The sintered molybdenum end cap blank was polished in a polishing machine and then subjected to hydrogen burning treatment at 1200℃ for 60 minutes in a hydrogen atmosphere to obtain the molybdenum end cap product.

[0119] Application Example 4

[0120] The difference between this application example and application example 1 is that the adhesive prepared in example 4 is used.

[0121] Application Example 5

[0122] The difference between this application example and application example 1 is that the adhesive prepared in example 5 is used.

[0123] Application Example 6

[0124] The difference between this application example and application example 1 is that the adhesive prepared in example 6 is used.

[0125] Application Example 7

[0126] The difference between this application example and application example 1 is that the adhesive prepared in example 7 is used.

[0127] Application Example 8

[0128] The difference between this application example and application example 1 is that the adhesive prepared in example 8 is used.

[0129] Comparative application examples

[0130] Comparative Application Example 1

[0131] The difference between this application example and application example 1 is that the adhesive prepared in comparative example 1 is used.

[0132] Comparative Application Example 2

[0133] The difference between this application example and application example 1 is that the adhesive prepared in comparative example 2 is used.

[0134] Performance testing

[0135] 1. Fisher particle size of granulated molybdenum powder

[0136] Granulated molybdenum powder was obtained according to the methods of Application Examples 1-8 and Comparative Application Examples 1-2. The obtained granulated molybdenum powder was measured using a Fisher particle size analyzer according to GB / T 3249-2022 "Method for Determination of Fisher Particle Size of Metals and Their Compounds Powders", and the results were recorded in Table 1.

[0137] 2. Hall flow rate of granulated molybdenum powder

[0138] Granulated molybdenum powder was obtained according to the methods of Application Examples 1-8 and Comparative Application Examples 1-2. The obtained granulated molybdenum powder was tested using a Hall flow meter according to GB / T 1482-2022 "Standard Funnel Method (Hall Flow Meter) for Determination of Flowability of Metal Powders", and the results were recorded in Table 1.

[0139] Hall velocity is an indicator of particle flowability; the lower the Hall velocity, the better the flowability.

[0140] 3. Bulk density of granulated molybdenum powder

[0141] Granulated molybdenum powder was obtained according to the methods of Application Examples 1-8 and Comparative Application Examples 1-2. The granulated molybdenum powder was then measured using a Scott volumetric meter according to GB / T1479.2-2011 "Determination of the apparent density of metal powders - Part 2: Scott volumetric method", and the results are recorded in Table 1.

[0142] Loose packing density is a macroscopic indicator of the degree of mixing and uniformity of particles. The higher the loose packing density, the better the uniformity of the particles.

[0143] 1. Appearance of molybdenum end cap

[0144] The molybdenum end caps were obtained according to the methods of Application Examples 1-8 and Comparative Application Examples 1-2. The surface of the molybdenum end caps was observed to see if they were flat and if there were any defects. The results were recorded in Table 1.

[0145] 2. Density of molybdenum end caps

[0146] The molybdenum end caps were obtained according to the methods of Application Examples 1-8 and Comparative Application Examples 1-2. The density of the molybdenum end caps was measured using the Archimedes displacement method, and the results are recorded in Table 1.

[0147] Table 1

[0148]

[0149] Results analysis:

[0150] As shown in Table 1, Comparative Application Example 1 did not add sodium carboxymethyl cellulose to the binder raw materials, Comparative Application Example 2 did not add polyvinylpyrrolidone to the binder raw materials, and Application Examples 1-3 used a binder made of polyvinyl alcohol, polyvinylpyrrolidone, and sodium carboxymethyl cellulose. Compared with Comparative Application Examples 1-2, the Hall flow rate of the granulated molybdenum powder prepared in Application Examples 1-3 decreased and the bulk density increased, indicating that the granulated molybdenum powder had better flowability, filling properties, and uniformity.

[0151] This is because the use of polyvinyl alcohol, polyvinylpyrrolidone, and sodium carboxymethyl cellulose can form a uniform film on the surface of the raw molybdenum powder. By bridging, the raw molybdenum powder is agglomerated into strong particles, and the size and particle size distribution of the molybdenum powder particles can be controlled, resulting in uniform performance of the molybdenum powder particles. This leads to better pressing performance, and the produced molybdenum end cap products have high density, good strength, a smooth and defect-free appearance, and better stability.

[0152] Application Examples 4-5 specify the types of dispersants and lubricants used. The dispersants selected were polyethylene glycol 2000 and polyethylene glycol 800 in a mass ratio of (0.6-0.8):(1.2-1.4), and sodium stearate was selected as the lubricant. This increased the bulk density of the granulated molybdenum powder, reduced the Hall flow rate, and further improved the flowability and uniformity of the granulated molybdenum powder. The molybdenum powder had a good morphology and less agglomeration, resulting in better molding, higher compact strength, and better density and performance of the molybdenum end cap product.

[0153] Application Examples 6-7 use sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid as a raw material in the adhesive. Introducing 2-acrylamido-2-methylpropanesulfonic acid segments into the sodium carboxymethyl cellulose molecule improves its compatibility with polyvinyl alcohol and polyvinylpyrrolidone crosslinking, and promotes hydrogen bonding and bridging effects, thereby further improving particle strength, green body density and strength, and ultimately increasing the density of the molybdenum end cap product.

[0154] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. An adhesive for producing molybdenum end caps, characterized in that, It is prepared from raw materials comprising the following parts by weight: 5-10 parts of polyvinyl alcohol; 2-5 parts of polyvinylpyrrolidone; Sodium carboxymethyl cellulose 0.5-2 parts; 1-3 parts lubricant; 1-3 parts dispersant; 90-120 parts deionized water; The sodium carboxymethyl cellulose selected is 2-acrylamido-2-methylpropanesulfonic acid-grafted sodium carboxymethyl cellulose, which is prepared from the following raw materials in parts by weight: 12-15 parts of 2-acrylamido-2-methylpropanesulfonic acid; Sodium carboxymethyl cellulose 1.5-2.5 parts; Initiator 0.05-0.1 parts; Crosslinking agent 0.08-0.15 parts.

2. The adhesive for producing molybdenum end caps according to claim 1, characterized in that: The lubricant is selected from one or more of glycerin, sodium stearate, and emulsified wax.

3. The adhesive for producing molybdenum end caps according to claim 1, characterized in that: The dispersant is selected from one or more of polyethylene glycol, sodium tripolyphosphate, and sodium hexadecyl sulfate.

4. The adhesive for producing molybdenum end caps according to claim 1, characterized in that: The lubricant is sodium stearate, and the dispersant is a mixture of polyethylene glycol 2000 and polyethylene glycol 800, with a mass ratio of polyethylene glycol 2000 to polyethylene glycol 800 of (0.6-0.8):(1.2-1.4).

5. The adhesive for producing molybdenum end caps according to claim 1, characterized in that: The polyvinyl alcohol has an average degree of polymerization of 1000-1500 and a degree of alcoholysis of 85%-95%.

6. A method for preparing an adhesive for producing molybdenum end caps according to any one of claims 1-5, characterized in that, Includes the following steps: Mix deionized water, dispersant and lubricant evenly and stir thoroughly for 0.5-1h to obtain a mixture. Heat the mixture to 60-80℃, add polyvinyl alcohol and polyvinylpyrrolidone to the mixture, stir for 20-30min, and maintain constant temperature stirring. Slowly add sodium carboxymethyl cellulose to the mixture, and obtain the binder after cooling.

7. The method for preparing an adhesive for producing molybdenum end caps according to claim 6, characterized in that, When sodium carboxymethyl cellulose is selected from sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid, it is prepared by the following steps: Weigh 2-acrylamido-2-methylpropanesulfonic acid into a reactor, add distilled water to dissolve it, add sodium hydroxide aqueous solution to neutralize to pH 6.5-7, add sodium carboxymethyl cellulose, and after complete dissolution, add initiator and crosslinking agent, stir evenly, and place in a microwave reactor. React for 5-10 minutes, remove the reactant and place it in an oven to dry at 80-90℃ to constant weight, soak and wash with distilled water, filter, dry, and pulverize to obtain sodium carboxymethyl cellulose grafted with 2-acrylamido-2-methylpropanesulfonic acid.

8. A method for preparing a molybdenum end cap, characterized in that, The specific steps of using the adhesive for producing molybdenum end caps according to any one of claims 1-5 include: The raw molybdenum powder and binder are mixed evenly and then wet-milled in a ball mill jar to prepare a molybdenum powder slurry. The molybdenum powder slurry is spray-dried and granulated, and the granulated molybdenum powder is collected. Granulated molybdenum powder is filled into the mold cavity and then pressed to form a molybdenum end cap compact. The binder is removed by heating the molybdenum end cap compact, and then sintered at high temperature to obtain the molybdenum end cap sintered compact. The molybdenum end cap sintered blank is polished and hydrogen-burned to obtain the molybdenum end cap product.

9. The method for preparing a molybdenum end cap according to claim 8, characterized in that: The raw material molybdenum powder has a mass fraction of 94-98 parts, a Fisher particle size of 3-3.5 μm, and a binder mass fraction of 2-6 parts.

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