Method for enhancing interface bonding strength of binder and powder in binder jet printing blank

Abstract

The invention discloses a method for enhancing the interface bonding strength of a binder and powder in a binder jet printing blank. The method comprises the following steps: introducing different types of polymer electrolytes into an ink-jet binder system for material systems with different isoelectric points so as to actively regulate and control chemical bonding or physical adsorption between the binder and particle surfaces, so that the interface performance is effectively enhanced. The method is suitable for various types of printing powder systems such as metal, ceramic and composite materials, and has the outstanding advantages of being easy to operate, high in universality and the like. The printing blank prepared by the method shows more excellent structural stability and densification effect in subsequent degreasing and sintering processes, effectively improves the mechanical properties and dimensional accuracy of a final product, and has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of binders, and specifically relates to a method for enhancing the interfacial bonding strength between binder and powder in a binder jet printing preform. Background Technology

[0002] Binder jetting (BJ), an important additive manufacturing technology, selectively bonds powder materials by jetting liquid binder layer by layer, followed by post-processing (such as debinding and sintering) to obtain dense three-dimensional parts. This technology boasts advantages such as high printing efficiency, relatively low cost, and a wide range of formable materials, demonstrating enormous application potential in fields such as casting, aerospace, and medical devices.

[0003] However, the industrial application of this technology still faces a key challenge: poor bonding between the binder and powder interface, resulting in generally low strength of the printed preforms and limiting the density and performance of the final parts. Preform strength, or green strength, directly determines the structural integrity and dimensional accuracy of the printed parts during subsequent handling, debinding, and even sintering processes. Insufficient preform strength can easily lead to edge damage, missing details, or even overall collapse, severely affecting the mechanical properties, dimensional accuracy, and yield of the final product.

[0004] Currently, binder jetting technology mostly employs general-purpose binder systems with relatively fixed compositions (such as polymer solutions with polyvinylpyrrolidone as the main component, Yanez-Sanchez, Sergio I., et al. "Model approach for binder selection in binder jetting." Industrial & Engineering Chemistry Research 60.42(2021):15162-15173.). While these general-purpose binders have a certain degree of universality, their core drawback lies in the lack of targeted design for the physicochemical properties of different powder materials. Powder materials, such as metals, ceramics, and their composite powders, exhibit significant differences in surface energy, wettability, and especially isoelectric point (pI) and other interfacial properties. General-purpose binders cannot actively adapt to these differences, resulting in the interfacial bonding force between the binder and powder particles mainly relying on weak physical adsorption and limited mechanical interlocking, with weak chemical bonding.

[0005] This weak interfacial bonding makes it difficult for the billet strength to meet the manufacturing requirements of complex structures or high-performance parts. In addition, during subsequent heat treatment, due to uneven interfacial bonding, the billet is prone to cracking during the debinding stage and densification kinetics are hindered during the sintering stage, ultimately affecting the density and overall performance of the parts.

[0006] Therefore, there is an urgent need and great significance to develop a binder modification method that can actively adapt to the interfacial characteristics of different powders, especially to strengthen the interfacial bonding based on the intrinsic properties of materials (such as the isoelectric point), in order to break through the bottleneck of binder jet printing technology and improve the performance and reliability of the final parts. Summary of the Invention

[0007] The object of the present invention is to provide a method for enhancing the interfacial bonding strength between a binder and a powder aiming at the problems of weak interfacial bonding force between a general binder and a powder material and insufficient green body strength in the existing binder jet printing technology. By introducing a selective matching mechanism based on the isoelectric point characteristics of the powder material and chemically modifying the particle surface, the interfacial bonding strength is significantly improved, thereby improving the properties of the green body and the density and mechanical properties of the final product.

[0008] The present invention aims to introduce different types of polyelectrolytes into the inkjet binder system for material systems with different isoelectric points to actively regulate the chemical bonding or physical adsorption between the binder and the powder material surface, thereby effectively strengthening the interfacial properties.

[0009] The technical solution adopted by the present invention:

[0010] A method for enhancing the interfacial bonding strength between a binder and a powder in a binder jet printed green body, the core of which is to construct a functionalized binder system that can adaptively adjust according to the isoelectric point (pI) of the powder material to achieve optimal interfacial bonding. The binder system includes a water-soluble polyelectrolyte, a metallocene, a complexing agent, a dispersant, a co-solvent and deionized water.

[0011] Furthermore, the mass fractions of each component of the binder are: 40 - 60 parts of deionized water, 20 - 40 parts of co-solvent, 5 - 10 parts of water-soluble polyelectrolyte, 2 - 3 parts of metallocene, 1 - 2 parts of complexing agent, 0.1 - 0.5 parts of dispersant.

[0012] The water-soluble polyelectrolyte is one or more of anionic polymer, cationic polymer, zwitterionic or non-ionic polyelectrolyte, and its selection is based on the isoelectric point (pI value) of the target printed powder material:

[0013] 1) For powder materials with an isoelectric point pI < 5, a cationic polyelectrolyte is selected;

[0014] 2) For powder materials with an isoelectric point 5 < pI < 8, a zwitterionic or non-ionic polyelectrolyte is selected;

[0015] 3) For powder materials with an isoelectric point pI > 8, an anionic polyelectrolyte is selected.

[0016] In the technical solution provided by the present invention, the water-soluble polymer electrolyte comprises one or more of the following: anionic polymers (xanthan gum, hyaluronic acid, polyvinylpyrrolidone, copovidone PVP / VA, polyacrylic acid); cationic polymers (chitosan, polyethyleneimine, polyquaternary ammonium salts, gelatin); zwitterionic polymers (zwitterionic cellulose derivatives, such as carboxymethyl-dimethylaminocellulose, etc.); or nonionic polymers (polyvinyl alcohol).

[0017] The type of dispersant must match the ionic properties of the selected polymer electrolyte to ensure the stability of the system.

[0018] In the above scheme, the dispersant is one or more of the following: anionic dispersant (sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyacrylate, lignin sulfonate), cationic dispersant (dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide), zwitterionic dispersant (cocamidopropyl betaine, N-dodecyl-N,N-dimethyl betaine, N-dodecyl-N,N-dimethyl sulfobetaine, N-hexadecyl-N,N-dimethyl-3-sulfopropyl betaine), or nonionic dispersant (polyethylene glycol).

[0019] In the above scheme, the co-solvent is one or more of ethylene glycol butyl ether, diethylene glycol butyl ether, triethylene glycol ethyl ether, triethylene glycol butyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and ethylene glycol dibutyl ether.

[0020] In the above scheme, the metallocene includes one or more of ferrocene and its derivatives, nickel dicene and its derivatives, titanium dicene and its derivatives, aluminum dicene and its derivatives, and metallocene-silane coupling agents.

[0021] In the above scheme, the complexing agent is one or more of citric acid, tannic acid, and ethylenediaminetetraacetic acid (EDTA).

[0022] A method for preparing a binder to enhance the interfacial bonding strength with powder materials includes: raw material pretreatment, stepwise dissolution and mixing, homogenization, filtration and quality inspection, ultimately obtaining a uniform and stable special binder. The specific steps are as follows:

[0023] S1. Raw material preparation and pretreatment: Accurately weigh each component according to the mass fraction, including 40-60 parts deionized water, 20-40 parts co-solvent, 5-10 parts water-soluble polymer electrolyte, 2-3 parts metallocene, 1-2 parts complexing agent and 0.1-0.5 parts dispersant; heat the deionized water to 30-40℃ for later use.

[0024] S2. Dissolve the polymer electrolyte: Slowly add the water-soluble polymer electrolyte to a part of preheated deionized water under stirring conditions, control the stirring speed at 300 - 500 rpm, and continuously stir until it is completely dissolved to form a uniform solution A;

[0025] S3. Complexation and dispersion treatment: Add the complexing agent and the dispersant to solution A, stir until completely dissolved, and obtain solution B for standby;

[0026] S4. Premix the co-solvent and metallocene: Add the metallocene to the co-solvent, stir at 200 - 400 rpm for 15 - 45 minutes at 40 - 65 °C to make it fully dissolved or dispersed, and obtain solution C;

[0027] S5. Stepwise mixing: Slowly add solution B to solution A, maintain stirring at 300 - 500 rpm, after mixing evenly, then slowly add solution C to avoid local high concentration;

[0028] S6. Homogenization and stabilization: Transfer the obtained mixed solution to a homogenizer, perform high-speed shearing treatment at 4000 - 6000 rpm for 5 - 10 minutes, and stand for defoaming for at least 2 hours to obtain a uniform and stable binder system;

[0029] S7. Filtering and quality inspection: Filter the binder using a filter screen (<1 μm) to remove possible agglomerated particles or impurities, and detect its viscosity, surface tension and pH value to ensure that it meets the working requirements of the printing nozzle.

[0030] A method for enhancing the interfacial bonding strength between the binder and the powder in a binder jetting printed body, screening the type of binder according to the isoelectric point of the powder material, specifically including the following steps:

[0031] S1. According to the isoelectric point (pI value) of the target printing powder material, select the corresponding type of water-soluble polymer electrolyte:

[0032] a) For powder materials with an isoelectric point pI < 5, select cationic polymer electrolytes;

[0033] b) For powder materials with an isoelectric point 5 < pI < 8, select zwitterionic or non-ionic polymer electrolytes;

[0034] c) For powder materials with an isoelectric point pI > 8, select anionic polymer electrolytes;

[0035] S2. Based on the ionic characteristics of the selected polymer electrolyte, match the corresponding type of dispersant:

[0036] a) When selecting cationic polymer electrolytes, use cationic or non-ionic dispersants in combination;

[0037] b) When using anionic polymer electrolytes, use anionic or nonionic dispersants in conjunction;

[0038] c) When using zwitterionic or nonionic polymer electrolytes, select the appropriate zwitterionic or nonionic dispersant based on the powder surface charge and the Hasen solubility parameter principle.

[0039] S3. Prepare the special adhesive according to the above method;

[0040] S4. Use the special adhesive to perform adhesive jet printing, and enhance the interfacial bonding strength through the electrostatic interaction between the polymer electrolyte and the powder surface.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. Targeted Enhancement of Interface Bonding: By accurately selecting polymer electrolytes with opposite charges based on the intrinsic property of powder materials—isoelectric point—the bonding force between the binder and the particle surface is actively enhanced by strong electrostatic interaction, fundamentally solving the problem of poor interface bonding of general binders.

[0043] 2. Significantly improves the performance of the green body: The green body prepared by the method of the present invention has higher green strength, and exhibits better structural stability and dimensional integrity in subsequent debinding and sintering processes, effectively reducing the generation of defects such as cracks and deformation.

[0044] 3. High versatility and simple operation: This method is applicable to various powder systems such as metals, ceramics and composite materials. It only requires adjusting the polymer and dispersant types in the binder formulation according to the easily measurable parameter of the isoelectric point of the powder material. No complicated process modification is required, making it easy to promote and apply. Attached Figure Description

[0045] Figure 1 Photographs of blanks prepared for the special-purpose adhesive and the general-purpose adhesive of the present invention.

[0046] Figure 2 Photographs of blanks prepared for the special-purpose adhesive and the general-purpose adhesive of the present invention. Detailed Implementation

[0047] Example 1: Preparation and printing of binder for high pI value alumina (Al2O3) ceramic powder

[0048] (1) Powder property analysis and binder component selection:

[0049] The target powder is alumina (Al2O3) ceramic powder with an isoelectric point (pI) of approximately 9.0, classifying it as a high pI value (pI>8). Therefore, polyacrylic acid (PAA) was selected as the water-soluble polymer electrolyte, sodium dodecylbenzenesulfonate (SDBS) was chosen as the dispersant, aluminocene was selected as the metallocene, citric acid was selected as the complexing agent, and diethylene glycol butyl ether was selected as the cosolvent.

[0050] (2) Adhesive preparation (by parts by weight):

[0051] A water-based adhesive comprises the following components in parts by weight: 55 parts deionized water as solvent, 32.9 parts diethylene glycol butyl ether as co-solvent, 8 parts polyacrylic acid as water-soluble polymer electrolyte, 2.5 parts aluminocene, 1.5 parts citric acid, and 0.1 parts sodium dodecylbenzenesulfonate.

[0052] (3) Preparation process:

[0053] S1. Raw material preparation: Accurately weigh each of the above components. Heat 55 parts of deionized water to 35°C for later use.

[0054] S2. Dissolving the polymer: Take 35 parts of preheated deionized water and slowly add 8 parts of polyacrylic acid while stirring at 400 rpm. Continue stirring until completely dissolved to obtain a clear and transparent solution A.

[0055] S3. Adding additives: Add 1.5 parts of citric acid and 0.1 parts of sodium dodecylbenzenesulfonate to solution A, and keep stirring until completely dissolved to obtain solution B.

[0056] S4, Premixed metallocene: Add 2.5 parts of aluminocene to 32.9 parts of diethylene glycol butyl ether and stir at 40℃ and 300 rpm for 15 minutes to obtain a homogeneous solution C.

[0057] S5. Stepwise mixing: While stirring at 400 rpm, slowly add solution B to the remaining 20 parts of deionized water, mix well, and then slowly add solution C dropwise.

[0058] S6. Homogenization and Stabilization: Transfer the mixture to a homogenizer and shear it at 5000 rpm for 8 minutes, then let it stand to degas for 2.5 hours.

[0059] S7. Filtration quality inspection: The adhesive obtained by filtration using a 0.8μm filter membrane was tested and found to have a viscosity of 12.5mPa·s, a surface tension of 32.5mN / m, and a pH value of 5.0, which meet the requirements for piezoelectric printhead printing.

[0060] (4) Printing and effect verification:

[0061] Alumina powder was jet-printed using a specially formulated binder. The resulting green body achieved a strength of 8 MPa, representing a strength increase of over 600% compared to a green body prepared using a general-purpose PVP binder (strength approximately 1.2 MPa). During subsequent debinding and sintering, the green body maintained its structural integrity without cracking or deformation. The final sintered part achieved a relative density of 99.2% and a flexural strength of 380 MPa.

[0062] Example 2: Preparation and printing of binder for low pI value silicon carbide (SiC) ceramic powder

[0063] (1) Powder property analysis and binder component selection:

[0064] The target powder is silicon carbide (SiC) ceramic powder with an isoelectric point (pI) of approximately 4.2, belonging to the low pI value (pI<5) material category. Therefore, chitosan was selected as the water-soluble polymer electrolyte, cetyltrimethylammonium bromide (CTAB), a compatible cationic dispersant, a metallocene-silane coupling agent, tannic acid as the complexing agent, and ethylene glycol butyl ether as the cosolvent.

[0065] (2) Adhesive preparation (by parts by weight):

[0066] A water-based adhesive comprises the following components in parts by weight: 55 parts deionized water as solvent, 35 parts ethylene glycol butyl ether as co-solvent, 5.6 parts chitosan as water-soluble polymer electrolyte, 3 parts metallocene-silane coupling agent, 1.2 parts tannic acid, and 0.2 parts hexadecyltrimethylammonium bromide.

[0067] (3) Preparation process:

[0068] S1. Raw material preparation: Accurately weigh each of the above components. Heat 55 parts of deionized water to 35°C for later use.

[0069] S2. Dissolving the polymer: Take 35 parts of preheated deionized water and slowly add 5.6 parts of chitosan while stirring at 400 rpm. Continue stirring until completely dissolved to obtain a clear and transparent solution A.

[0070] S3. Adding additives: Add 1.2 parts of tannic acid and 0.2 parts of hexadecyltrimethylammonium bromide to solution A, and keep stirring until completely dissolved to obtain solution B.

[0071] S4. Premixed metallocene: Add 2.5 parts of metallocene-silane coupling agent to 35 parts of ethylene glycol butyl ether and stir at 45°C and 300 rpm for 20 minutes to obtain a homogeneous mixture C.

[0072] S5. Stepwise mixing: Under stirring at 400 rpm, slowly add Solution B to the remaining 20 parts of deionized water. After mixing evenly, slowly add the mixed Solution C dropwise.

[0073] S6. Homogenization and stabilization: Transfer the mixed solution to a homogenizer and perform high-speed shearing treatment at 5000 rpm for 15 minutes, and then leave it standing for defoaming for 4 hours.

[0074] S7. Filtration and quality inspection: Filter the obtained binder using a 0.8 μm filter membrane. The measured viscosity is 13.2 mPa·s, the surface tension is 31.8 mN / m, and the pH value is 5.0, meeting the requirements for piezoelectric nozzle printing.

[0075] (4) Printing and effect verification:

[0076] Use the special binder prepared in this example for binder jet printing of silicon carbide powder. The test results show that the green strength of the obtained product reaches 3.2 MPa, which is 220% higher than that of the SiC green body (strength about 1.0 MPa) prepared using the general PVP binder. In the subsequent thermal debinding and sintering processes, due to the strong interfacial bonding, the green body exhibits excellent structural integrity, without defects such as cracking and warping, and the edges are clearer.

[0077] Example 3: Preparation and printing of a binder for SS316L stainless steel metal powder with medium pI value

[0078] (1) Analysis of powder characteristics and selection of binder components:

[0079] The target powder is SS316L stainless steel metal powder, whose surface oxide layer makes its isoelectric point (pI) about 6.0, belonging to a material with a medium pI value (5 < pI < 8). Therefore, carboxymethyl-dimethylamino cellulose is selected as the water-soluble polymer electrolyte, the dispersant is selected as the non-ionic dispersant polyethylene glycol 400 (PEG-400) to maintain the system compatibility, the metallocene is selected as ferrocene, the complexing agent is selected as ethylenediaminetetraacetic acid (EDTA), and the co-solvent is selected as triethylene glycol butyl ether.

[0080] (2) Preparation of the binder (by mass fraction):

[0081] An aqueous binder is composed of the following components by mass: 55 parts of deionized water as the solvent, 30 parts of triethylene glycol butyl ether as the co-solvent, 10.9 parts of carboxymethyl-dimethylamino cellulose as the water-soluble polymer electrolyte, 2.5 parts of ferrocene, 1.5 parts of EDTA, and 0.1 part of PEG-400.

[0082] (3) Preparation process:

[0083] S1. Raw material preparation: Accurately weigh each of the above components. Heat 55 parts of deionized water to 35°C for later use.

[0084] S2. Dissolving the polymer: Take 35 parts of preheated deionized water and slowly add 8 parts of carboxymethyl-dimethylaminocellulose while stirring at 400 rpm. Continue stirring until completely dissolved to obtain a clear and transparent solution A.

[0085] S3. Adding additives: Add 1.5 parts EDTA and 0.1 parts PEG-400 to solution A, and keep stirring until completely dissolved to obtain solution B.

[0086] S4. Premixed metallocene: Add 2.5 parts of ferrocene to 30 parts of triethylene glycol butyl ether and stir at 40°C and 300 rpm for 15 minutes to obtain a homogeneous mixture C.

[0087] S5. Stepwise mixing: While stirring at 400 rpm, slowly add solution B to the remaining 20 parts of deionized water, mix well, and then slowly add mixture C dropwise.

[0088] S6. Homogenization and Stabilization: Transfer the mixture to a homogenizer and shear it at 5000 rpm for 10 minutes, then let it stand to degas for 3 hours.

[0089] S7. Filtration quality inspection: The adhesive obtained by filtration using a 0.8μm filter membrane was tested and found to have a viscosity of 10.8mPa·s, a surface tension of 33.1mN / m, and a pH value of 6.5, which meet the requirements for piezoelectric printhead printing.

[0090] (4) Printing and effect verification:

[0091] After being used in SS316L stainless steel powder printing, the green strength reached 25MPa, far exceeding the 8MPa of general PVP binders. After debinding and sintering, the parts exhibited uniform and stable dimensional shrinkage, a density of 99.5%, and a tensile strength of 530MPa.

[0092] Comparative Example 1: Preparation and Printing of Alumina (Al2O3) Ceramics Using a General-Purpose Binder

[0093] (1) Preparation of polyvinylpyrrolidone (PVP) adhesive (by parts by weight):

[0094] A water-based adhesive comprises the following components in parts by weight: 64.9 parts deionized water as solvent, 20 parts isopropanol and 10 parts ethanol as co-solvent, 5 parts PVA as water-soluble polymer, and 0.1 parts alkyl glycoside as surfactant.

[0095] (2) Preparation process:

[0096] S1. Prepare mother liquor A (deionized aqueous phase): Add weighed deionized water to the solution, start stirring (300-500 rpm), and heat to 45℃.

[0097] S2. Dissolving the polymer: The polymer is completely dissolved in the aqueous phase to obtain a transparent solution.

[0098] S3. Add the corresponding amounts of isopropanol, ethanol and alkyl glycoside in sequence, and stir thoroughly for 45 minutes.

[0099] S4. Filtration quality inspection: The adhesive obtained by filtration through a 0.8μm filter membrane was tested and found to have a viscosity of 5.0mPa·s, a surface tension of 35.5mN / m, and a pH value of 7.0, which meet the requirements for piezoelectric printhead printing.

[0100] (4) Printing and effect verification:

[0101] Alumina powder was bonded and sprayed using a PVP-type universal binder. The resulting green compact strength was only about 1.2 MPa.

[0102] Comparative Example 2: Preparation and Printing of Silicon Carbide (SiC) Ceramics Using a General-Purpose Binder

[0103] The binder and its preparation process used in this comparative example are the same as those in Comparative Example 1.

[0104] Printing and effect verification:

[0105] Binder jet printing of SiC ceramic powder was performed using a PVP-type universal binder. The resulting green body strength was only about 1.0 MPa.

[0106] Comparative Example 3: Preparation and Printing of SS316L Ceramics Using a General-Purpose Adhesive

[0107] The binder and its preparation process used in this comparative example are the same as those in Comparative Example 1.

[0108] Printing and effect verification:

[0109] Binder jet printing of SS316L ceramic powder was performed using a PVP-type universal binder. The resulting green body strength was approximately 8.0 MPa.

[0110] Photographs of the SS316L preforms printed using the specialized adhesive of Example 3 and the general-purpose adhesive of Comparative Example 3 are shown below. Figure 1As can be seen, the blank prepared using the special binder has a clear edge contour and low surface roughness, while the blank prepared using the general binder has local edge defects and high surface roughness, showing a significant difference in forming quality. This indicates that the blank prepared by the method of the present invention can exhibit better structural stability and dimensional integrity during subsequent debinding and sintering processes, effectively reducing the generation of defects such as cracks and deformation. The flexural strength of the SS316L blanks printed based on the special binder of Example 3 and the general binder of Comparative Example 3 are shown in the figure. Figure 2 As can be seen, the flexural strength of the green body prepared with the special binder is significantly higher than that of the green body prepared with the general binder, with an increase of more than two times. This indicates that the method of the present invention can effectively enhance the bonding force between the binder and the powder interface, thereby significantly improving the mechanical properties of the green body.

Claims

1. A method for enhancing the interfacial bonding strength between binder and powder in a binder jet printing preform, characterized in that, Select the type of binder according to the isoelectric point of the powder material, which specifically includes the following steps: S1. Select the corresponding type of water-soluble polymer electrolyte according to the isoelectric point of the target printed powder material: a) For powder materials with an isoelectric point pI < 5, select cationic polymer electrolytes; b) For powder materials with an isoelectric point 5 < pI < 8, select zwitterionic or non-ionic polymer electrolytes; c) For powder materials with an isoelectric point pI > 8, select anionic polymer electrolytes; S2. Based on the ionic characteristics of the selected polymer electrolyte, match the corresponding type of dispersant: a) When a cationic polymer electrolyte is selected, use a cationic or non-ionic dispersant in combination; b) When an anionic polymer electrolyte is selected, use an anionic or non-ionic dispersant in combination; c) When a zwitterionic or non-ionic polymer electrolyte is selected, based on the surface charge condition of the powder, select a matching zwitterionic or non-ionic dispersant according to the principle of the Hansen solubility parameter; S3. Prepare a special binder; S4. Use the special binder for binder jet printing to enhance the interfacial bonding strength through the electrostatic interaction between the polymer electrolyte and the powder surface.

2. The method according to claim 1, characterized in that, The method for preparing the special binder described in step S2 includes the following steps: S1. Raw material preparation and pretreatment: Accurately weigh each component by mass fraction, including 40 - 60 parts of deionized water, 20 - 40 parts of co-solvent, 5 - 10 parts of water-soluble polymer electrolyte, 2 - 3 parts of metallocene, 1 - 2 parts of complexing agent, and 0.1 - 0.5 parts of dispersant; Heat the deionized water to 30 - 40 °C for standby; S2. Dissolve the polymer electrolyte: Slowly add the water-soluble polymer electrolyte to a part of the preheated deionized water under stirring, control the stirring speed at 300 - 500 rpm, and continuously stir until completely dissolved to form a uniform solution A; S3. Complexing and dispersion treatment: Add the complexing agent and dispersant to solution A, stir until completely dissolved, and obtain solution B for standby; S4. Premix the co-solvent and metallocene: Add the metallocene to the co-solvent, stir at 200 - 400 rpm at 40 - 65 °C for 15 - 45 minutes to make it fully dissolved or dispersed, and obtain solution C; S5. Step-by-step mixing: Add solution B to solution A, maintain stirring at 300 - 500 rpm, mix evenly, and then slowly add solution C; S6. Homogenization and stabilization: Transfer the obtained mixed solution to a homogenizer, perform high-speed shearing treatment at 4000 - 6000 rpm for 5 - 10 minutes, and stand for defoaming for at least 2 hours to obtain a uniform and stable binder system.

3. The method according to claim 1, characterized in that, The water-soluble polymer electrolyte is one or more of anionic polymers, cationic polymers, zwitterionic or non-ionic polymer electrolytes.

4. The method according to claim 1, characterized in that, The anionic polymers include xanthan gum, hyaluronic acid, polyvinylpyrrolidone, copovidone PVP / VA, and polyacrylic acid; the cationic polymers include chitosan, polyethyleneimine, polyquaternium salts, and gelatin; the zwitterionic polymers include carboxymethyl-dimethylaminocellulose; and the nonionic polymers include polyvinyl alcohol.

5. The method according to claim 1, characterized in that, The anionic dispersants include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyacrylate, and lignin sulfonate; the cationic dispersants include dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; the zwitterionic dispersants include cocamidopropyl betaine, N-dodecyl-N,N-dimethyl betaine, N-dodecyl-N,N-dimethyl sulfobetaine, and N-hexadecyl-N,N-dimethyl-3-sulfopropyl betaine; and the nonionic dispersants include polyethylene glycol.

6. The method as described in claim 2, characterized in that, The co-solvent is one or more of ethylene glycol butyl ether, diethylene glycol butyl ether, triethylene glycol ethyl ether, triethylene glycol butyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and ethylene glycol dibutyl ether.

7. The method as described in claim 2, characterized in that, The metallocene comprises one or more of ferrocene and its derivatives, nickel dicene and its derivatives, titanium dicene and its derivatives, aluminum dicene and its derivatives, and metallocene-silane coupling agents.

8. The method as described in claim 2, characterized in that, The complexing agent is one or more of citric acid, tannic acid, and ethylenediaminetetraacetic acid.

9. The method as described in claim 2, characterized in that, The binder is filtered using a <1μm filter to remove any possible agglomerates or impurities. Its viscosity, surface tension, and pH value are tested to ensure that it meets the requirements for printhead operation.

10. The method as described in claim 1, characterized in that, Using this method for binder jet printing, the green strength between the polymer electrolyte and the powder material surface is high, and it exhibits excellent structural stability and dimensional integrity during subsequent debinding and sintering processes.

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