Silver powder and preparation method thereof

Abstract

The present application discloses a silver powder and a preparation method thereof. The preparation method of the silver powder comprises: S1: dissolving ascorbic acid and a dispersant in deionized water to obtain a reducing solution; S2: dissolving silver nitrate in deionized water to obtain an oxidizing solution; S3: dissolving a dispersant in deionized water to obtain a neutralizing solution; S4: dissolving a surfactant in anhydrous ethanol to obtain a modified solution; S5: using the neutralizing solution as a base liquid, and adding the oxidizing solution and the reducing solution to the base liquid at the same time, and after the oxidizing solution and the reducing solution are added, adding the modified solution to obtain a primary product; S6: washing, drying and grinding the primary product to obtain the target silver powder. The silver powder obtained in the embodiment of the present application has both good sintering activity and high dispersibility, and has broad application prospects.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic silver powder, and in particular to a silver powder and a preparation method thereof. Background Art

[0002] Photovoltaic silver powder is the most basic and most important material in the photovoltaic industry. In the process of pursuing efficiency and energy utilization, the requirements for silver powder are gradually updated. Common silver powder generally pursues better activity to achieve higher efficiency, and increases its sintering activity by reducing its crystallinity or surface roughness or porous structure; the other type pursues better printing performance, and controls the silver powder to have better spherical shape, smoother surface, higher crystallinity, and better dispersion to make it have better printability.

[0003] However, how to make silver powder have both the above-mentioned good sintering activity and high dispersion performance so that the silver powder can be used in both the photovoltaic industry and the printing industry to improve the application prospects of silver powder is a problem that needs to be solved. Summary of the invention

[0004] The embodiment of the present application provides a silver powder and a preparation method thereof. The prepared silver powder has good sintering activity and high dispersibility, and the preparation method is simple.

[0005] In a first aspect, the present application provides a method for preparing silver powder, comprising the following steps:

[0006] S1: dissolving ascorbic acid and a dispersant in deionized water to obtain a reducing solution having an ascorbic acid concentration of (96.5-112) g / L and a dispersant concentration of (3.6-5.7) g / L;

[0007] S2: dissolving silver nitrate in deionized water to obtain an oxidation solution with a silver nitrate concentration of (182-208) g / L;

[0008] S3: dissolving the dispersant in deionized water to obtain a neutralized solution having a dispersant concentration of (68-112.5) g / L;

[0009] S4: dissolving the surfactant in anhydrous ethanol to obtain a modified solution with a surfactant concentration of (1.25-3.5) g / L;

[0010] S5: using the neutralization solution as the base solution, adding the oxidizing solution and the reducing solution to the base solution at the same time, and after the addition of the oxidizing solution and the reducing solution is completed, adding the modifying solution to obtain a primary product;

[0011] S6: washing, drying and grinding the primary product to obtain target silver powder.

[0012] In some embodiments of the present application, the step S1 comprises: dissolving the ascorbic acid and the dispersant in deionized water at a mass ratio of (19.5-24.5):1 to obtain a reducing solution containing an ascorbic acid concentration of (96.5-112) g / L and a dispersant concentration of (3.6-5.7) g / L.

[0013] In some embodiments of the present application, step S2 includes:

[0014] Silver nitrate is dissolved in deionized water, and nitric acid is added to adjust the pH of the silver nitrate solution to 1.6-3.2, to obtain an oxidizing solution with a silver nitrate concentration of (182-208) g / L; wherein the mass ratio of silver nitrate to ascorbic acid in step S1 is (1.76-1.98):1.

[0015] In some embodiments of the present application, the mass ratio of the silver nitrate in step S2 to the dispersant in step S3 is (9.8-14):1.

[0016] Optionally, the mass ratio of the silver nitrate in step S2 to the dispersant in step S3 is 13.1:1.

[0017] In some embodiments of the present application, in step S3, the dispersant is selected from one or more of polyvinyl pyrrolidone, polyacrylic acid, polyethylene glycol polyvinyl alcohol, and methyl acrylate.

[0018] In some embodiments of the present application, the mass ratio of the silver nitrate in step S2 to the surfactant in step S4 is (1200-2600):1.

[0019] In some embodiments of the present application, in step S4, the surfactant is selected from one or more of oleic acid, caprylic acid, lauric acid, and stearic acid. In the steps S1 to S3, the reaction temperature is controlled to be 25-30°C.

[0020] In some embodiments of the present application, step S5 includes:

[0021] The neutralized liquid is used as the base liquid, and the base liquid is stirred at a stirring speed of 800 to 1500 rpm. The oxidizing liquid and the reducing liquid are added to the base liquid simultaneously under stirring. After the oxidizing liquid and the reducing liquid are added, the modified solution is added and stirred continuously to obtain a primary product.

[0022] In some embodiments of the present application, step S6 includes:

[0023] Add deionized water to the primary product by sedimentation method according to the amount and stir to wash, the stirring speed is controlled at 800-1500 rpm, the stirring time is 5-10 minutes, and the sedimentation standing time is 5-15 minutes; wash with anhydrous ethanol 1-2 times to obtain a solid;

[0024] Drying the solid at a temperature of 75 to 85° C. for 2 to 2.5 hours;

[0025] The solid matter is sieved using a sieve with a mesh size of 30 or larger, and the sieved solid matter is secondary dried at a temperature of 75 to 85° C. for 3 to 4 hours; the secondary dried solid matter is ground to obtain the target silver powder.

[0026] On the other hand, the present application provides a silver powder prepared by any one of the preparation methods in the first aspect above.

[0027] The preparation method of silver powder provided in the embodiment of the present application obtains red blood cell-like silver powder through a large number of trial experiments, and the preparation steps are convenient for mass production; the silver powder prepared by the preparation method has the advantages of higher tap density, lower burn-in loss, controllable particle size, better dispersion of silver powder in organic carrier, better and higher printability, etc.; the particle size and burn-in loss can be controlled by temperature, dispersant mass ratio and related process steps to meet different organic phase requirements, so that the obtained silver powder can be suitable for both photovoltaic industry and printing industry, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is a schematic flow chart of the method for preparing silver powder provided in the embodiment of the present application;

[0030] Figure 2 This is a photo of silver particles under SEM in Example 1 of the present application;

[0031] Figure 3 This is a photograph of silver particles under SEM in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0032] The present application is further described in detail below in conjunction with examples. The following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the following examples, if specific conditions are not specified, they are carried out according to normal conditions or conditions recommended by the manufacturer. The methods used are conventional methods known in the art unless otherwise specified, and the consumables and reagents used are commercially available unless otherwise specified. Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the recorded content may also be applied to the present application.

[0033] like Figure 1 As shown, the present application provides a method for preparing silver powder, comprising the following steps:

[0034] S1: dissolving ascorbic acid and a dispersant in deionized water to obtain a reducing solution having an ascorbic acid concentration of (96.5-112) g / L and a dispersant concentration of (3.6-5.7) g / L;

[0035] S2: dissolving silver nitrate in deionized water to obtain an oxidation solution with a silver nitrate concentration of (182-208) g / L;

[0036] S3: dissolving the dispersant in deionized water to obtain a neutralized solution having a dispersant concentration of (68-112.5) g / L;

[0037] S4: dissolving the surfactant in anhydrous ethanol to obtain a modified solution with a surfactant concentration of (1.25-3.5) g / L;

[0038] S5: using the neutralization solution as the base solution, adding the oxidizing solution and the reducing solution to the base solution at the same time, and after the addition of the oxidizing solution and the reducing solution is completed, adding the modifying solution to obtain a primary product;

[0039] S6: washing, drying and grinding the primary product to obtain target silver powder.

[0040] The following is an illustration of each of the embodiments.

[0041] Example

[0042] Example 1

[0043] Example 1 provides a method for preparing silver powder and the silver powder prepared by the method. The method for preparing silver powder in Example 1 comprises the following steps S1-S6:

[0044] S1: Preparation of reducing solution;

[0045] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0046] S2: prepare oxidation solution;

[0047] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 26° C. to obtain solution B;

[0048] S3: prepare neutralizing solution;

[0049] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0050] S4: preparing modified solution;

[0051] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0052] S5: reaction synthesis;

[0053] Solution C is used as the base liquid, and the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain a primary product;

[0054] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0055] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0056] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0057] Example 2

[0058] Example 2 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0059] The difference between Example 2 and Example 1 is that when preparing the reducing solution in Example 2, the dispersant is replaced by polyacrylic acid; in steps S1 to S3, the reaction temperature is controlled to be 30° C.; when preparing the modified solution, the surfactant is selected to be octanoic acid;

[0060] The method for preparing silver powder in Example 2 comprises the following steps S1-S6:

[0061] S1: preparation of reducing solution;

[0062] Dissolve 270 g L-ascorbic acid and 12 g polyvinyl pyrrolidone in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 30° C. to obtain solution A;

[0063] S2: prepare oxidation solution;

[0064] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 30° C. to obtain solution B;

[0065] S3: prepare neutralizing solution;

[0066] Dissolve 36 g of polyvinyl pyrrolidone in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature to 30°C to obtain solution C;

[0067] S4: preparing modified solution;

[0068] Dissolve 0.3 g of octanoic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0069] S5: reaction synthesis;

[0070] Solution C is used as the base liquid, and the above-mentioned solution A and solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain the initial product.

[0071] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0072] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0073] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0074] Example 3

[0075] Example 3 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0076] The difference between Example 3 and Example 1 is that when the neutralization solution in Example 3 is prepared, the amount of dispersant added is changed, and the mass ratio of silver nitrate in step S2 to the dispersant in step S3 is changed to (6.2-7.2):1;

[0077] The method for preparing silver powder in Example 3 comprises the following steps S1-S6:

[0078] S1: Preparation of reducing solution;

[0079] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0080] S2: prepare oxidation solution;

[0081] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 26° C. to obtain solution B;

[0082] S3: prepare neutralizing solution;

[0083] Dissolve 54 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0084] S4: preparing modified solution;

[0085] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0086] S5: reaction synthesis;

[0087] Solution C is used as the base liquid, and the above-mentioned solution A and solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain the initial product.

[0088] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0089] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0090] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0091] Example 4

[0092] Example 4 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0093] The difference between Example 4 and Example 1 is that in the reaction synthesis process of step S5 in Example 4, the order of adding solution A and solution B is different.

[0094] The method for preparing silver powder in Example 4 comprises the following steps S1-S6:

[0095] S1: preparation of reducing solution;

[0096] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0097] S2: prepare oxidation solution;

[0098] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 26° C. to obtain solution B;

[0099] S3: prepare neutralizing solution;

[0100] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0101] S4: preparing modified solution;

[0102] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0103] S5: reaction synthesis;

[0104] Take solution C as the base liquid, mix solution A and solution B evenly for 3 minutes to obtain a mixed liquid, and then add the mixed liquid to the base liquid. The adding time is within 3min30s. After solution A and solution B are added, add modified solution D and continue the reaction for no less than 8min to obtain the initial product.

[0105] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0106] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0107] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0108] Example 5

[0109] Example 5 provides a method for preparing silver powder and the silver powder prepared using the preparation method.

[0110] The difference between Example 5 and Example 1 is that the steps of the reaction synthesis process of step S5 in Example 5 are different, and also include stirring the base solution and the modified solution D at a stirring speed of 800 to 1500 rpm.

[0111] The method for preparing silver powder in Example 5 comprises the following steps S1-S6:

[0112] S1: Preparation of reducing solution;

[0113] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0114] S2: prepare oxidation solution;

[0115] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 26° C. to obtain solution B;

[0116] S3: prepare neutralizing solution;

[0117] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0118] S4: preparing modified solution;

[0119] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0120] S5: reaction synthesis;

[0121] Solution C is used as the base liquid, and the base liquid is stirred at a stirring speed of 800 rmp. Under the above stirring state, the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3 min 30 s. After the addition of solution A and solution B is completed, the modified solution D is added and continuously stirred at a speed of 1000 rmp. The reaction continues for no less than 8 min to obtain the initial product.

[0122] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0123] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0124] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0125] Example 6

[0126] Example 6 provides a method for preparing silver powder and the silver powder prepared using the preparation method.

[0127] The difference between Example 6 and Example 1 is that step S6 in Example 6 also includes screening and secondary drying.

[0128] The method for preparing silver powder in Example 6 comprises the following steps S1-S6:

[0129] S1: preparation of reducing solution;

[0130] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0131] S2: prepare oxidation solution;

[0132] 500 g of silver nitrate and 30 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 26° C. to obtain solution B;

[0133] S3: prepare neutralizing solution;

[0134] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0135] S4: preparing modified solution;

[0136] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0137] S5: reaction synthesis;

[0138] Solution C is used as the base liquid, and the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain a primary product;

[0139] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0140] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0141] Dry the solids at 75-85°C for 2-2.5 hours;

[0142] The solid matter is sieved using a sieve with a mesh size of 30 or larger, and the sieved solid matter is secondary dried at a temperature of 75 to 85° C. for 3 to 4 hours;

[0143] The solid matter after secondary drying is ground to obtain the target silver powder.

[0144] Comparative Example

[0145] Comparative Example 1

[0146] Comparative Example 1 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0147] The difference between Comparative Example 1 and Example 1 is that when the oxidizing solution in Comparative Example 1 is prepared, the amount of nitric acid added is changed.

[0148] The preparation method of silver powder in Comparative Example 1 comprises the following steps S1-S6:

[0149] S1: Preparation of reducing solution;

[0150] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 26° C. to obtain solution A;

[0151] S2: prepare oxidation solution;

[0152] 500 g of silver nitrate and 15 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 5, and the temperature was controlled to 26° C. to obtain solution B;

[0153] S3: prepare neutralizing solution;

[0154] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 26°C to obtain solution C;

[0155] S4: preparing modified solution;

[0156] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0157] S5: reaction synthesis;

[0158] Solution C is used as the base liquid, and the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain a primary product;

[0159] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0160] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0161] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0162] Comparative Example 2

[0163] Comparative Example 2 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0164] The difference between Comparative Example 2 and Example 1 is that in step S1 to step S3 of Comparative Example 2, the reaction temperature is controlled to be 15°C.

[0165] The preparation method of silver powder in Comparative Example 2 comprises the following steps S1-S6:

[0166] S1: Preparation of reducing solution;

[0167] Dissolve 270 g L-ascorbic acid and 12 g polypropylene alcohol in deionized water until the solution is diluted to 2.6 L and the temperature is controlled at 15°C to obtain solution A;

[0168] S2: prepare oxidation solution;

[0169] 500 g of silver nitrate and 15 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 15° C. to obtain solution B;

[0170] S3: prepare neutralizing solution;

[0171] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 15°C to obtain solution C;

[0172] S4: preparing modified solution;

[0173] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0174] S5: reaction synthesis;

[0175] Solution C is used as the base liquid, and the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain a primary product;

[0176] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0177] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0178] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0179] Comparative Example 3

[0180] Comparative Example 3 provides a method for preparing silver powder and the silver powder prepared by the preparation method.

[0181] The difference between Comparative Example 3 and Example 1 is that no dispersant is added when preparing the reducing solution in step S1 of Comparative Example 3.

[0182] The preparation method of silver powder in Comparative Example 3 comprises the following steps S1-S6:

[0183] S1: Preparation of reducing solution;

[0184] Dissolve 270 g L-ascorbic acid in deionized water until the solution is 2.6 L and control the temperature to 15°C to obtain solution A;

[0185] S2: prepare oxidation solution;

[0186] 500 g of silver nitrate and 15 g of nitric acid were dissolved in deionized water, the volume of the solution was fixed to 2.6 L, the pH of the silver nitrate solution was adjusted to 2.2, and the temperature was controlled to 15° C. to obtain solution B;

[0187] S3: prepare neutralizing solution;

[0188] Dissolve 36 g of polypropylene alcohol in deionized water, adjust the volume of the solution to 0.5 L, and control the temperature at 15°C to obtain solution C;

[0189] S4: preparing modified solution;

[0190] Dissolve 0.3 g of oleic acid in anhydrous ethanol, make the solution volume 100 ml, and evenly divide it into two modified solutions D;

[0191] S5: reaction synthesis;

[0192] Solution C is used as the base liquid, and the above solution A and the above solution B are added to the base liquid at the same time, and the addition time is within 3min30s. After the addition of solution A and solution B is completed, the modified solution D is added and the reaction is continued for not less than 8min to obtain a primary product;

[0193] S6: washing, drying, sieving and grinding the primary product to obtain target silver powder;

[0194] Add 12L of deionized water each time to wash and stir the product, the stirring speed is 1000rpm, the stirring and washing time is 5min, after the stirring stops, let it settle for about 5min, pour out the upper clear night, repeat the above steps 3 times, after the washing is completed, add 3L of anhydrous ethanol and stir, stir for 20min, the stirring speed is 1000rpm, after the stirring stops, let it settle for 15min, then pour out the clear liquid to obtain a solid;

[0195] The solid matter is dried at a temperature of 75 to 85° C. for 2 to 2.5 hours, and the dried solid matter is ground to obtain the target silver powder.

[0196] Performance parameters

[0197] The target silver powders prepared in the above Examples 1 to 6 and Comparative Examples 1 to 3 were tested, and the results of the parameters of the silver powders were as follows:

[0198]

[0199]

[0200] Results Analysis

[0201] From the morphology, SEM Figure 2 and Figure 3 It can be seen that the silver powder obtained in Example 1 has a special shape and an appearance of a red blood cell-like silver powder. It has a certain degree of crystallinity and some holes, and the silver powder has good distribution uniformity. In the preparation process of the reducing solution in Comparative Example 3, when the dispersant polypropylene alcohol is not added, the silver powder obtained no longer has a red blood cell-like structure, which is quite different from the target silver powder and has worse dispersibility.

[0202] From the parameters of silver powder, the silver powder prepared in Examples 1-6 has a tap density of more than 6.3, a specific surface area of ​​less than 0.35, a burnout rate of 0.25% to 0.4%, and a particle size of 1.61 to 3.2 μm; it has the advantages of high tap density, low burnout, controllable particle size, better dispersion of silver powder in organic carriers, and better and higher printability. The crystallinity can be adjusted by temperature, and the particle size and burnout can be adjusted by the amount of dispersant to meet different organic phase requirements, so that it can be applied to both the photovoltaic industry and the printing industry.

[0203] It should be noted that when used in the photovoltaic industry, a layer of organic coating will be artificially applied to the surface of photovoltaic silver powder to facilitate the subsequent preparation of silver paste. Usually, the organic content of photovoltaic silver powder cannot be zero, but in addition to this part of the surface-coated organic matter, we may inevitably introduce some organic matter during the reaction process. This is caused by the reaction itself. The less this part of organic matter, the better. Therefore, a low burn-out rate indicates that the amount of organic residue in the silver powder is reduced. When the 538°C burn-out rate of the silver powder is controlled at 0.25% to 0.4%, it is more conducive to the subsequent preparation of photovoltaic silver paste.

[0204] Combined with Example 2, when the type of dispersant, the reaction temperature is 30°C, and the surfactant is changed, the properties of the silver powder are changed. Among them, the tap density of the silver powder prepared in Example 2 is significantly improved, the specific surface area is reduced, and the burning rate is reduced. 10 and D50 The particle size decreases, D 90 The particle size increases, and it can be seen that the difference in particle size between the multiple silver powders prepared in Example 2 increases, indicating that the crystallinity of the silver powder increases, while also controlling its burn-in rate to only 28%, that is, the amount of organic residue in the silver powder is reduced, which is more conducive to the subsequent preparation of photovoltaic silver paste.

[0205] In combination with Example 1 and Example 3, when the amount of dispersant in the base solution is increased or the mass ratio of silver nitrate and dispersant is changed, the particle size is smaller, the specific surface area is larger, and the sintering activity is increased; it can be seen that the amount of dispersant or the change in the mass ratio of silver nitrate and dispersant also affects the various properties of silver powder.

[0206] In combination with Example 1 and Example 4, compared with the method of adding solution A and solution B to the base solution at the same time, the silver powder obtained by first mixing solution A and solution B to obtain a mixed solution and then adding the mixed solution to solution B has a D 50 The particle size increases significantly and the specific surface area increases.

[0207] Combining Example 1 and Example 5, in the reaction synthesis process of step S5 in Example 5, the base solution and the modified solution are stirred to obtain the silver powder D 50 The particle size is reduced and the tap density of the silver powder is increased, so that the particle size of part of the silver powder can be reduced under the stirring speed of 800-1500rmp, the crystallinity of the silver powder can be adjusted, and the dispersion performance of the silver powder can be improved.

[0208] The preparation method in Example 6 further includes sieving and secondary drying. The silver powder D prepared in Example 6 10 , D 50 Particle size, D 90 The particle size is reduced and the specific surface area is also significantly reduced, so that after screening and secondary drying, the uniformity of the silver powder particle size distribution can be further improved, making it have better dispersion performance.

[0209] Combining Example 1 with Comparative Examples 1-2, it can be seen that in Comparative Example 1, the pH of the oxidizing solution is increased by reducing the amount of nitric acid in the oxidizing solution. 10 The particle size is reduced, but the silver powder has a lower tap density, a higher specific surface area and a higher burn-in rate, indicating that its crystallinity is lower, but this will lead to a decrease in its printability; similarly, in comparative example 2, when the temperature is lowered to 15°C in steps S1-S3, the silver powder obtained has a larger specific surface area, an increased burn-in rate, and a lower tap density, which will affect its conductive properties applied in the photovoltaic field; therefore, the silver powder obtained in comparative examples 1-2 is difficult to meet the needs of both the photovoltaic industry and the printing industry.

[0210] In combination with Example 1 and Comparative Example 3, no dispersant was added when the reducing solution was prepared in Comparative Example 3, and the silver powder obtained had D90 The particle size is greater than 3.5 μm, the dispersion performance is poor, and the burn-in rate is low, so that the sintering activity is affected. At the same time, the silver powder tap density obtained in Comparative Example 3 is also low, which is difficult to meet the requirements of the photovoltaic industry or the printing industry.

[0211] The above is a detailed introduction to a silver powder and a preparation method thereof provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for technicians in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing silver powder, characterized in that: The following steps are involved: S1: dissolving ascorbic acid and a dispersant in deionized water to obtain a reducing solution having an ascorbic acid concentration of (96.5-112) g / L and a dispersant concentration of (3.6-5.7) g / L; S2: dissolving silver nitrate in deionized water to obtain an oxidation solution with a silver nitrate concentration of (182-208) g / L; S3: dissolving the dispersant in deionized water to obtain a neutralized solution with a dispersant concentration of (68~112.5) g / L; S4: dissolving the surfactant in anhydrous ethanol to obtain a modified solution with a surfactant concentration of (1.25-3.5) g / L; S5: using the neutralization solution as the base solution, adding the oxidizing solution and the reducing solution to the base solution at the same time, and after the addition of the oxidizing solution and the reducing solution is completed, adding the modifying solution to obtain a primary product; S6: washing, drying and grinding the primary product to obtain target silver powder; Wherein, the surfactant is selected from one or more of oleic acid, caprylic acid, lauric acid and stearic acid.

2. The method for preparing silver powder according to claim 1, characterized in that: The step S1 comprises: dissolving the ascorbic acid and the dispersant in deionized water at a mass ratio of (19.5-24.5):1 to obtain a reducing solution having an ascorbic acid concentration of (96.5-112) g / L and a dispersant concentration of (3.6-5.7) g / L.

3. The method for preparing silver powder according to claim 1, characterized in that: The step S2 comprises: Silver nitrate is dissolved in deionized water, and nitric acid is added to adjust the pH of the silver nitrate solution to 1.6-3.2, to obtain an oxidation solution with a silver nitrate concentration of (182-208) g / L; wherein the mass ratio of silver nitrate to ascorbic acid in step S1 is (1.76-1.98):

1.

4. The method for preparing silver powder according to claim 1, characterized in that: The mass ratio of the silver nitrate in step S2 to the dispersant in step S3 is (9.8-14):

1.

5. The method for preparing silver powder according to claim 1, characterized in that: In step S3, the dispersant is selected from one or more of polyvinyl pyrrolidone, polyacrylic acid, polyethylene glycol, polyvinyl alcohol, and methyl acrylate.

6. The method for preparing silver powder according to any one of claims 1 to 5, characterized in that: In the steps S1 to S3, the reaction temperature is controlled to be 25-30°C.

7. The method for preparing silver powder according to claim 1, characterized in that: The step S5 comprises: The neutralized liquid is used as the base liquid, and the base liquid is stirred at a stirring speed of 800-1500 rpm, and the oxidizing liquid and the reducing liquid are added to the base liquid simultaneously under stirring. After the oxidizing liquid and the reducing liquid are added, the modified solution is added and stirred continuously to obtain a primary product.

8. The method for preparing silver powder according to claim 1, characterized in that: The step S6 comprises: Add deionized water to the primary product by sedimentation method according to the amount and stir to wash, the stirring speed is controlled at 800-1500 rpm, the stirring time is 5-10 min, and the sedimentation standing time is 5-15 min; wash with anhydrous ethanol 1-2 times to obtain a solid; Drying the solid matter at a temperature of 75-85° C. for 2-2.5 hours; The solid matter is sieved using a sieve with a mesh size of 30 or larger, and the sieved solid matter is secondary dried at a temperature of 75-85° C. for 3-4 hours; the secondary dried solid matter is ground to obtain the target silver powder.

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