A method for preparing 1-3 mu m micron-grade spherical gold powder by microfluidic slow ripening growth

Abstract

The present application relates to precious metal powder preparation technical field, especially to a kind of microfluidic slow ripening growth preparation 1~3 μm micron spherical gold powder method.The present application is divided into three ways independent delivery chloroauric acid solution, dispersant solution, reducing agent solution, material sequentially flows through three-stage microflow plate, and complexation, reduction, slow ripening reaction is completed step by step;The first two stages respectively prepare gold fulminate precursor, and reduce to generate nascent crystal nucleus, and the third stage microflow ripening plate realizes crystal grain slow growth based on oswald ripening.The structure size of each stage microflow plate is fixed, and the residence time of material can be changed by adjusting flow rate, and the higher the flow rate, the larger the gold powder particle size.The present application relies on segmented reaction to combine flow rate selective regulation to control crystal grain size, and D50 is prepared in 1~3 μm, narrow distribution, high sphericity gold powder, solve the product particle size hybrid defect of traditional process, adapt aerospace military components, vehicle level chip, medical sensing element, high reliability high precision electronic components and other fields.

Description

Technical Field

[0001] This invention relates to the field of precious metal powder preparation technology, and in particular to a method for preparing 1~3μm micron-sized spherical gold powder by microfluidic slow ripening growth. Background Technology

[0002] Spherical gold powder is a key functional filler for electronic conductive pastes and electrodes of low-temperature co-fired ceramic components. Spherical gold powder with different particle size ranges is suitable for completely different application scenarios. Among them, micron-sized spherical gold powder with D50 concentrated in 1~3μm has unique advantages such as high sintering density, low conductivity loss and good printing coating uniformity, and is an indispensable raw material for high-end microelectronics manufacturing.

[0003] Existing processes for synthesizing spherical gold powder generally suffer from a lack of directional control over the grain growth process. Nucleation and grain growth occur simultaneously and cannot be controlled separately, resulting in a wide range of particle sizes in the final product, with a large number of ultrafine particles and oversized coarse grains mixed together, resulting in a wide particle size distribution. If the reaction time is extended to promote grain growth, it is easy to cause particle agglomeration and adhesion, as well as damage and distortion of the spherical morphology. It is difficult to obtain high-quality micron gold powder with a strictly stable particle size of 1~3μm, narrow particle size distribution, good sphericity, and smooth surface in batches.

[0004] It is evident that there is currently a lack of a continuous synthesis process that can segmentally separate the precursor preparation, reduction, and grain ripening growth process, and precisely and directionally control the grain size by regulating the instantaneous nucleation amount in the reduction stage, thereby stably preparing narrowly distributed 1~3μm spherical gold powder. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing 1-3 μm micron-sized spherical gold powder by slow microfluidic curing growth. The method of this invention can stably prepare high-quality gold powder with a D50 of 1-3 μm, narrow particle size distribution, regular spherical shape, and no aggregation.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing 1-3 μm micron-sized spherical gold powder by microfluidic slow ripening growth, comprising the following steps: The aqueous chloroauric acid solution and the dispersant solution are simultaneously and independently delivered to the first-stage microfluidic complexing plate to achieve mixing and generate a gold fulminate complex solution. The reducing agent solution is delivered to the second-stage microfluidic reaction plate, and the material discharged from the first-stage microfluidic complexing plate is simultaneously fed into the second-stage microfluidic reaction plate to carry out the reduction reaction and generate a gold powder suspension. The material from the second-stage microfluidic reaction plate enters the third-stage microfluidic ripening plate, where short-term Ostwald ripening is used to achieve grain growth, and finally a suspension containing 1~3μm micron-sized spherical gold powder is discharged. The concentration of gold ions in the chloroauric acid aqueous solution is 35~80 g / L; the dispersant solution is composed of a dispersant, ammonia and water; The flow rate ratio of the chloroauric acid aqueous solution, the dispersant solution, and the reducing agent solution is 1:1:2. The flow rate of the chloroauric acid aqueous solution is 30~80 mL / min; The microchannel lengths of the first-stage microfluidic complexing plate, the second-stage microfluidic reaction plate, and the third-stage microfluidic ripening plate are 8~18m, and the inner diameter of the microchannels is 1.6mm.

[0007] Preferably, the mass fraction of the ammonia water is 25-28%; the mass ratio of the ammonia water to the gold ions in the chloroauric acid aqueous solution is 0.7-1.2:1.

[0008] Preferably, the mass ratio of the dispersant in the dispersant solution to the mass ratio of gold ions in the chloroauric acid aqueous solution is 0.18~0.4:1.

[0009] Preferably, the dispersant is one or more selected from gelatin, sodium citrate, gum arabic, polyvinylpyrrolidone, and sodium polyacrylate.

[0010] Preferably, the reducing agent in the reducing agent solution is a mixture of ascorbic acid and sodium sulfite, wherein the mass ratio of ascorbic acid to sodium sulfite is 1:1.

[0011] Preferably, the mass ratio of the reducing agent in the reducing agent solution to the gold ions in the chloroauric acid aqueous solution is 2~7:1.

[0012] Preferably, the complexing temperature in the first-stage microfluidic complexing plate, the reaction temperature in the second-stage microfluidic reaction plate, and the curing temperature in the third-stage microfluidic curing plate are 20~60℃.

[0013] Preferably, after obtaining a suspension containing 1~3μm micron-sized spherical gold powder, the process further includes sequentially performing solid-liquid separation, water washing, alcohol washing, and drying on the suspension to obtain 1~3μm micron-sized spherical gold powder.

[0014] Preferably, the concentration of gold ions in the chloroauric acid aqueous solution is 40~60 g / L.

[0015] This invention innovatively employs a three-stage series microfluidic reaction plate segmented reaction system. The first two stages complete the uniform preparation of gold fulminate precursor and the controllable reduction of nascent gold nuclei, respectively. The third stage independently completes the slow ripening and growth of grains, effectively isolating the precursor complexation, nucleus generation, and grain growth processes, weakening the mutual interference between each stage, and solving the problem of disordered grain growth caused by the chaotic reaction timing coupling in traditional processes. This provides a process basis for accurately locking the target particle size range of 1~3μm. This invention features a separate third-stage microfluidic ripening plate, making the Oswald slow ripening process an independent core step in grain shaping. This avoids interference from the front-end nucleation stage on grain growth. By relying on the short-term continuous reaction of microfluidics, the growth rate of grain dynamics is precisely controlled, promoting uniform and full grain growth in a directional manner. This invention specifically addresses the technical shortcoming of existing microfluidic processes that cannot stably generate 1~3μm large-diameter spherical gold powder.

[0016] This invention fixes the length of the third-stage microfluidic ripening plate and adjusts the flow rate of the three fluid transport channels to simultaneously change the material mixing time in the second-stage reduction section and the residence time in the entire channel. The higher the flow rate, the shorter the material mixing time, the less the total amount of instantaneous nucleation, the more metal precursors available for each crystal grain, and the more complete the Oswald slow ripening growth. Based on this, the precise and controllable adjustment of the gold powder particle size in the range of 1~3μm can be effectively achieved. Compared with the prior art, the present invention has the following beneficial effects: Excellent powder properties and strong controllability: This invention uses a three-stage reaction time decoupling and flow rate regulation to control the nucleation amount, combined with the Oswald ripening mechanism of an independent third-stage microfluidic ripening plate, to stably prepare high-quality gold powder with a D50 of 1~3μm, narrow particle size distribution, regular spherical shape and no adhesion. The powder has good batch consistency and can be used to prepare high-end microelectronic pastes and precision conductive electrodes, meeting the stringent requirements of high-precision electronic components and other fields.

[0017] The process is simple, stable, and suitable for mass production: This invention adopts a microfluidic continuous reaction mode, avoiding the defects of chaotic reaction coupling in traditional processes. Particle size can be precisely controlled simply by adjusting the flow rate (under the condition that the raw material ratio, the structure and size of each microfluidic plate are fixed, and all conditions are the same except for the flow rate, the higher the flow rate, the larger the gold powder particle size). The operation is simple and the control is flexible. The entire process has no material dead zones or accumulation problems, operates stably, and can meet the needs of large-scale continuous production. Attached Figure Description

[0018] Figure 1 SEM image of the gold powder prepared in Example 1; Figure 2 The particle size distribution diagram is shown for the gold powder prepared in Example 1. Figure 3 SEM image of the gold powder prepared in Example 2; Figure 4 This is a particle size distribution diagram of the gold powder prepared in Example 2; Figure 5 SEM image of the gold powder prepared in Example 3; Figure 6 SEM image of the gold powder prepared in Comparative Example 1; Figure 7 SEM image of the gold powder prepared in Comparative Example 2; Figure 8 SEM image of the gold powder prepared in Comparative Example 3; Figure 9 SEM image of the gold powder prepared in Comparative Example 4; Figure 10 The particle size distribution of the gold powder prepared in Comparative Example 4 is shown. Figure 11 Here is a SEM image of the gold powder prepared in Comparative Example 5; Figure 12 The particle size distribution of the gold powder prepared in Comparative Example 5 is shown. Figure 13 The graph shows the particle size distribution curves corresponding to the five flow velocities in Examples 1-3 and Comparative Examples 4-5. Detailed Implementation

[0019] This invention provides a method for preparing 1-3 μm micron-sized spherical gold powder by microfluidic slow ripening growth, comprising the following steps: The aqueous chloroauric acid solution and the dispersant solution are simultaneously and independently delivered to the first-stage microfluidic complexing plate to achieve mixing and generate a gold fulminate complex solution. The reducing agent solution is delivered to the second-stage microfluidic reaction plate, and the material discharged from the first-stage microfluidic complexing plate is simultaneously fed into the second-stage microfluidic reaction plate to carry out the reduction reaction and generate a gold powder suspension. The material exiting the second-stage microfluidic reaction plate enters the third-stage microfluidic ripening plate, where short-term Ostwald ripening is used to achieve grain growth, and finally, a suspension containing 1~3μm micron-sized spherical gold powder is obtained.

[0020] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available products well known in the art.

[0021] This invention simultaneously and independently delivers chloroauric acid aqueous solution and dispersant solution to the first-stage microfluidic complexing plate to achieve mixing and generate fulminate complex solution.

[0022] In this invention, the concentration of gold ions in the chloroauric acid aqueous solution is preferably 35~80 g / L, and in specific embodiments it can be 40, 50, 60, 70 or 80 g / L.

[0023] In this invention, the dispersant solution is composed of a dispersant, ammonia, and water; the dispersant is preferably one or more of gelatin, sodium citrate, gum arabic, polyvinylpyrrolidone, and sodium polyacrylate; the mass ratio of gold ions in the dispersant and the chloroauric acid aqueous solution is preferably 0.18~0.4:1, and in specific embodiments it can be 0.2:1, 0.25:1, 0.3:1, 0.35:1, or 0.4:1. In this invention, the mass fraction of the ammonia is 25~28% (density approximately 0.9 g / cm³). 3The mass ratio of gold ions in the ammonia water and the chloroauric acid aqueous solution is preferably 0.7~1.2:1, and in specific embodiments it can be 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1.

[0024] In this invention, the preferred delivery flow rate of the chloroauric acid aqueous solution is 30-80 mL / min, and in specific embodiments it can be 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80 mL / min. The delivery flow rate ratio of the chloroauric acid aqueous solution to the dispersant solution is 1:1.

[0025] In this invention, the microchannel length of the first-stage microfluidic complexing plate is 8-18 m, and in specific embodiments it can be 9, 10, 11, 12, 14, 16, or 18 m, with an inner diameter of 1.6 mm. In this invention, the complexation temperature within the first-stage microfluidic complexing plate is preferably 20-60°C, and in specific embodiments it can be 20, 30, 40, 50, or 60°C. This invention achieves thorough mixing of chloroauric acid aqueous solution and dispersant solution within the first-stage microfluidic complexing plate, generating a gold fulminate complex solution.

[0026] In this invention, a reducing agent solution is delivered to a second-stage microfluidic reaction plate, and the material discharged from the first-stage microfluidic complexing plate simultaneously enters the second-stage microfluidic reaction plate to carry out a reduction reaction and generate a gold powder suspension.

[0027] In this invention, the reducing agent in the reducing agent solution is preferably a mixture of ascorbic acid and sodium sulfite; the mass ratio of ascorbic acid to sodium sulfite is preferably 1:1. In this invention, the mass ratio of the reducing agent in the reducing agent solution to the gold ions in the chloroauric acid aqueous solution is preferably 2~7:1, and in specific embodiments it can be 2:1, 3:1, 4:1, 5:1, 6:1 or 7:1.

[0028] In this invention, the flow rate of the reducing agent solution is 1:1 to the flow rate of the material discharged from the first-stage microfluidic complexing plate, that is, the flow rate of the reducing agent solution is 2:1:1 to the flow rate of the aforementioned chloroauric acid aqueous solution and dispersant solution. Preferably, the chloroauric acid aqueous solution, dispersant solution, and reducing agent solution are transported separately by independent pumps.

[0029] In this invention, the microchannel length and inner diameter of the second-stage microfluidic reaction plate are the same as those of the first-stage microfluidic complexing plate, and the reaction temperature within the second-stage microfluidic reaction plate is consistent with the complexation temperature within the first-stage microfluidic complexing plate; these details will not be elaborated further here. In this invention, a reduction reaction is carried out within the second-stage microfluidic reaction plate to generate gold crystal nuclei.

[0030] Next, the material from the second-stage microfluidic reaction plate is fed into the third-stage microfluidic ripening plate. The growth of grains is achieved by short-term Ostwald ripening within the plate, and finally, a suspension containing 1~3μm micron-sized spherical gold powder is obtained.

[0031] In this invention, the microchannel length and inner diameter of the third-stage microfluidic ripening plate are the same as those of the first-stage microfluidic complexing plate. The ripening temperature within the third-stage microfluidic ripening plate is consistent with the complexing temperature within the first-stage microfluidic complexing plate, which will not be elaborated further here. This invention achieves Ostwald slow ripening within the third-stage microfluidic ripening plate, resulting in uniform and sufficient grain growth. In this invention, "slow ripening" refers to the kinetic behavior of grains following the Ostwald ripening mechanism, undergoing slow dissolution, recrystallization, and growth. It does not require materials to remain in the material for an extended period. The process relies on the microfluidic channels to achieve continuous short-time reactions, precisely controlling the final particle size through the slow growth behavior of the grains themselves.

[0032] After obtaining a suspension containing 1-3 μm micron-sized spherical gold powder, the present invention preferably further includes performing solid-liquid separation, water washing, alcohol washing and drying on the suspension in sequence to obtain 1-3 μm micron-sized spherical gold powder.

[0033] This invention does not have any special requirements for the solid-liquid separation method; any solid-liquid separation method well-known in the art can be used, such as filtration. In this invention, the drying temperature is preferably 60°C.

[0034] This invention employs a three-stage series microfluidic plate to segmentally isolate the complexation, reduction, and ripening reaction stages, and uses three independent delivery pumps to precisely control the material flow rate at each reaction stage. Relying on the third-stage microfluidic ripening plate, it achieves slow and uniform grain growth, and produces micron-sized spherical gold powder with a particle size strictly controlled in the range of 1~3μm, a narrow particle size distribution, no fine irregular particles or ultra-large particles, and excellent sphericity.

[0035] This invention avoids the defects of chaotic reaction coupling in traditional processes. The length of each microfluidic plate is fixed, and the particle size can be precisely controlled by adjusting the flow rate. It is simple to operate and flexible to control.

[0036] The following detailed description, in conjunction with embodiments, illustrates the method for preparing 1-3 μm micron-sized spherical gold powder by microfluidic slow ripening growth provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0037] In the following examples and comparative examples, the reaction temperature of each microfluidic plate was 30°C, the microchannel length of each microfluidic plate was 11m, and the inner diameter of the microchannel was 1.6mm.

[0038] Example 1 S1. Preparation of raw material solution 1: Weigh 104.17g of chloroauric acid with a gold content of 48% and dissolve it in 1L of deionized water to prepare an aqueous solution of chloroauric acid with a gold ion concentration of 50 g / L. S2. Preparation of raw material solution 2: Weigh 10g of polyvinylpyrrolidone dispersant and dissolve it in 1L of deionized water, then add 50mL of ammonia water with a mass fraction of 25~28% to obtain a composite ammonia water dispersant solution; S3. Preparation of raw material solution 3: Weigh 100g ascorbic acid and 100g sodium sulfite and dissolve them in 2L of deionized water to obtain a compound reducing agent solution; S4. First-stage complexation: Set the flow rate of pump 1 and pump 2 to 45 mL / min. After conveying raw material liquid 1 and raw material liquid 2 to the inlet of the first-stage microfluidic complexing plate, close the switch to stop material conveying. Then, simultaneously open the switches of pump 1 and pump 2 to convey raw material liquid 1 and raw material liquid 2 to the first-stage microfluidic complexing plate for complexation. S5. Secondary reduction: Set the flow rate of pump 3 to 90 mL / min to deliver the raw material liquid 3 to the second-stage microfluidic reaction plate. After the material from the first-stage microfluidic complexing plate is discharged, it flows into the second-stage microfluidic reaction plate to carry out the reduction reaction. S6. Three-stage slow curing: The liquid output from the second-stage microfluidic reaction plate is completely fed into the third-stage microfluidic curing plate of the fixed module. After a short curing period, the liquid is discharged to obtain a suspension containing gold powder. The resulting gold powder suspension was then filtered, and the filter cake was washed thoroughly with deionized water and ethanol in sequence. The solid powder was then collected and dried in a 60°C oven.

[0039] The gold powder prepared in Example 1 was observed by SEM, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the powder has excellent sphericity, good particle dispersion without agglomeration, and narrow particle size distribution. Further particle size analysis was conducted, and the results are shown in [the table below]. Figure 2 The gold powder D50 is approximately 1.56 μm. Example 2 The feed liquid ratio, microfluidic structure at each stage, operating steps, and post-treatment conditions were completely consistent with those in Example 1; only the flow rates of pumps 1 and 2 were adjusted to 35 mL / min, and the flow rate of pump 3 was adjusted to 70 mL / min.

[0040] Test results: The material mixing and contact time was longer, the number of instantaneous nuclei was greater, and the finished product D50≈1.05 μm (see...) Figure 4 Good sphericity (see) Figure 3 ), which is within the target range of 1~3 μm.

[0041] Example 3 The feed liquid ratio, microfluidic structure at each stage, operating steps, and post-treatment conditions were completely consistent with those in Example 1; only the flow rates of pumps 1 and 2 were adjusted to 60 mL / min, and the flow rate of pump 3 was adjusted to 120 mL / min.

[0042] Test results: Short material mixing and contact time, low initial nucleation volume, sufficient grain maturation and growth, finished product D50≈2.66 μm, uniform particle size (see...). Figure 5 ), without coarse grains.

[0043] Comparative Example 1 Same as Example 1, but without the third-stage microfluidic curing plate; The gold powder prepared in Comparative Example 1 was observed by SEM, and the results are as follows: Figure 6 As shown. By Figure 6 It is evident that without an independent grain ripening process, a large number of nascent crystal nuclei cannot grow sufficiently, resulting in products primarily consisting of submicron particles. Testing showed that the gold powder's D50 was approximately 0.87 μm, demonstrating that, to a certain extent, a three-stage independent ripening unit is a necessary structure for obtaining powders of the target particle size.

[0044] Comparative Example 2 Similar to Example 1, the three raw materials simultaneously enter the first-stage microfluidic complexing plate, then pass through the second-stage microfluidic reaction plate and the third-stage microfluidic ripening plate.

[0045] The gold powder prepared in Comparative Example 2 was observed by SEM, and the results are as follows: Figure 7 As shown. By Figure 7 It can be seen that when the gold source, the dispersion buffer system, and the reducing agent come into contact simultaneously, nucleation occurs instantaneously, and grain growth is disordered. The product contains a large number of fine and coarse grains, with a wide particle size distribution. The particles are severely deformed and adhered, and the morphology is irregular. It is impossible to stably control the particle size in the range of 1~3 μm. This verifies the key role of segmented temporal decoupling in the uniformity of powder.

[0046] Comparative Example 3 S1. Preparation of raw material solution 1: Weigh 52.08g of chloroauric acid with a gold content of 48% and dissolve it in 1L of deionized water to prepare an aqueous solution of chloroauric acid with a gold ion concentration of 25 g / L. S2. Preparation of raw material solution 2: Weigh 5.0g of polyvinylpyrrolidone dispersant and dissolve it in 1L of deionized water, then add 25mL of ammonia water with a mass fraction of 25%~28% to obtain a composite ammonia water dispersant solution; S3. Preparation of raw material solution 3: Weigh 50g ascorbic acid and 50g sodium sulfite and dissolve them in 2L of deionized water to obtain a compound reducing agent solution; S4. First-stage complexation: Set the flow rate of pump 1 and pump 2 to 45 mL / min. After conveying raw material liquid 1 and raw material liquid 2 to the inlet of the first-stage microfluidic complexing plate, close the switch to stop material conveying. Then, simultaneously open the switches of pump 1 and pump 2 to convey raw material liquid 1 and raw material liquid 2 to the first-stage microfluidic complexing plate for complexation. S5. Secondary reduction: Set the flow rate of pump 3 to 90 mL / min to deliver the raw material liquid 3 to the second-stage microfluidic reaction plate. After the material from the first-stage microfluidic complexing plate is discharged, it flows into the second-stage microfluidic reaction plate to carry out the reduction reaction. S6. Three-stage slow curing: The liquid output from the second-stage microfluidic reaction plate is completely fed into the third-stage microfluidic curing plate of the fixed module. After a short curing period, the liquid is discharged to obtain a suspension containing gold powder. The resulting gold powder suspension was then filtered, washed thoroughly with deionized water and ethanol in sequence, and the solid powder was collected and dried in a 60°C oven. The gold powder prepared in Comparative Example 3 was observed by SEM, and the results are as follows: Figure 8 As shown. By Figure 8 It can be seen that the concentration of the entire reaction system is too low, the stability of the grain growth environment in the reaction system is poor, the particle size of the powder fluctuates greatly, the uniformity is significantly reduced, the particle size is uneven, and it is difficult to obtain narrowly distributed 1~3 μm spherical gold powder in batches. This indicates that the medium and high concentration reaction system is more suitable for the segmented microfluidic ripening process of this invention.

[0047] Comparative Example 4 The feed liquid ratio, microfluidic structure at each stage, operating steps, and post-treatment conditions were completely consistent with those in Example 1; only the flow rates of pumps 1 and 2 were adjusted to 85 mL / min, and the flow rate of pump 3 was adjusted to 85 mL / min.

[0048] Test results: Grain growth was sufficient, and the powder D50 ≈ 3.63 μm (see...) Figure 10 Good dispersibility, but decreased surface smoothness (see...) Figure 9 ).

[0049] Comparative Example 5 The feed liquid ratio, microfluidic structure at each stage, operating steps, and post-treatment conditions were completely consistent with those in Example 1; only the flow rates of pumps 1 and 2 were adjusted to 25 mL / min, and the flow rate of pump 3 was adjusted to 50 mL / min.

[0050] Test results: The initial nucleation amount of the material increased significantly, the particle size of the obtained gold powder was less than 1 μm, and the finished product D50 ≈ 0.89 μm (see...). Figure 12 ), well dispersed and evenly distributed (see) Figure 11 ).

[0051] Figure 13This is a superimposed curve of particle size distribution corresponding to five flow velocities in Examples 1-3 and Comparative Examples 4-5. Figure 13 It is known that when the raw material ratio is fixed, the structure and size of each microfluidic plate are fixed, and all conditions are the same except for the flow rate, the higher the flow rate, the larger the gold powder particle size. Within the flow rate range defined by this invention, by selectively controlling the flow rate, the precise preparation of spherical gold powder with a D50 of 1~3μm can be achieved. If the flow rate is not selected properly, the product particle size will deviate from the target.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing 1-3 μm micron-sized spherical gold powder by microfluidic slow ripening growth, characterized in that, Includes the following steps: The aqueous chloroauric acid solution and the dispersant solution are simultaneously and independently delivered to the first-stage microfluidic complexing plate to achieve mixing and generate a gold fulminate complex solution. The reducing agent solution is delivered to the second-stage microfluidic reaction plate, and the material discharged from the first-stage microfluidic complexing plate is simultaneously fed into the second-stage microfluidic reaction plate to carry out the reduction reaction and generate a gold powder suspension. The material from the second-stage microfluidic reaction plate enters the third-stage microfluidic ripening plate, where short-term Ostwald ripening is used to achieve grain growth, and finally a suspension containing 1~3μm micron-sized spherical gold powder is discharged. The concentration of gold ions in the chloroauric acid aqueous solution is 35~80 g / L; the dispersant solution is composed of a dispersant, ammonia and water; The flow rate ratio of the chloroauric acid aqueous solution, the dispersant solution, and the reducing agent solution is 1:1:

2. The flow rate of the chloroauric acid aqueous solution is 30~80 mL / min; The microchannel lengths of the first-stage microfluidic complexing plate, the second-stage microfluidic reaction plate, and the third-stage microfluidic ripening plate are 8~18m, and the inner diameter of the microchannels is 1.6mm.

2. The method according to claim 1, characterized in that, The mass fraction of the ammonia solution is 25-28%; the mass ratio of gold ions in the ammonia solution to those in the chloroauric acid aqueous solution is 0.7-1.2:

1.

3. The method according to claim 1, characterized in that, The mass ratio of the dispersant in the dispersant solution to the mass ratio of gold ions in the chloroauric acid aqueous solution is 0.18~0.4:

1.

4. The method according to claim 1 or 3, characterized in that, The dispersant is one or more of gelatin, sodium citrate, gum arabic, polyvinylpyrrolidone, and sodium polyacrylate.

5. The method according to claim 1, characterized in that, The reducing agent in the reducing agent solution is a mixture of ascorbic acid and sodium sulfite, and the mass ratio of ascorbic acid to sodium sulfite is 1:

1.

6. The method according to claim 1 or 5, characterized in that, The mass ratio of the reducing agent to the gold ions in the chloroauric acid aqueous solution is 2~7:

1.

7. The method according to claim 1, characterized in that, The complexation temperature in the first-stage microfluidic complexing plate, the reaction temperature in the second-stage microfluidic reaction plate, and the curing temperature in the third-stage microfluidic curing plate are 20~60℃.

8. The method according to claim 1, characterized in that, After obtaining a suspension containing 1-3 μm micron-sized spherical gold powder, the process further includes sequentially performing solid-liquid separation, water washing, alcohol washing, and drying on the suspension to obtain 1-3 μm micron-sized spherical gold powder.

9. The method according to claim 1, characterized in that, The concentration of gold ions in the chloroauric acid aqueous solution is 40~60 g / L.

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