A method for preparing highly dispersed submicron spherical palladium powder

Abstract

The present invention discloses a method for preparing highly dispersible submicron spherical palladium powder. The method comprises the following steps: first, weighing solid palladium nitrate and dissolving it in dilute nitric acid to prepare a dilute palladium nitrate solution; then dissolving a reducing agent in deionized water to obtain a reducing solution; then weighing a dispersant and an additive and dissolving them in deionized water to obtain a mixed base solution; and then mixing the three to obtain a reaction slurry containing palladium powder. The mixture is then filtered, washed, and dried to obtain submicron spherical palladium powder particles. The present invention adopts a liquid phase reduction method to reduce the palladium nitrate solution with ascorbic acid or hydrazine hydrate as a reducing agent to prepare the submicron spherical palladium powder. An organic polymer dispersant and a small molecule alcohol additive are simultaneously added to the base solution in a symmetrical manner. While ensuring the yield of palladium powder, the particle growth process and dispersibility are well controlled. The prepared palladium powder particles are spherical and highly dispersed, with a particle size of 100 to 600 nm.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal powder material preparation, and particularly relates to a method for preparing highly dispersed submicron spherical palladium powder. Background Art

[0002] With the booming electronic information industry, microelectronic components are increasingly characterized by integration, low cost, and high efficiency. Thick-film conductive pastes are gradually demonstrating their unique advantages. Palladium powder is not only an excellent catalytic material and hydrogen storage material, but also an essential component of thick-film conductive pastes. As an additive in thick-film conductive pastes, palladium powder can inhibit the migration of silver ions in the conductive film under high-temperature and high-humidity electric fields and also improve the paste's corrosion resistance. The properties of palladium powder directly affect the performance of the paste, leading to increasingly stringent quality requirements for palladium powder in industrial production.

[0003] The few reports on palladium powder preparation techniques have shown that the resulting powders are prone to agglomeration (see: CN202210979544.1, "A Method for Preparing Highly Crystalline and Spherical Palladium Powders with Strong Oxidation Resistance"; CN201710450372.8, "High Specific Surface Area Ultrafine Palladium Powder and Preparation Method Thereof"). Furthermore, ensuring high yields of palladium powder while improving its dispersibility and achieving controllable particle size is a pressing issue. Summary of the Invention

[0004] In view of this, the patent of this invention provides a method for preparing highly dispersed submicron spherical palladium powder to ensure the correctness and efficiency of marine electrical connectors during the wiring process.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing highly dispersed submicron spherical palladium powder, comprising the following steps:

[0006] (1) Weighing solid palladium nitrate and dissolving it in dilute nitric acid, and mixing thoroughly to prepare a dilute palladium nitrate solution;

[0007] (2) dissolving a reducing agent in deionized water and mixing thoroughly to prepare a reducing solution, wherein the reducing agent is ascorbic acid or hydrazine hydrate;

[0008] (3) Weigh 0.05-0.5 g of dispersant and 0.05-0.5 g of additive respectively, dissolve them in a small amount of deionized water to obtain a dispersant solution and an additive solution, wherein the dispersant is a mixture of one or more of polyvinyl pyrrolidone, polyethylene glycol, and Tween 80, and the additive is a mixture of one or more of methanol, ethanol, and n-propanol; then mix the dispersant solution and the additive solution, stir evenly, and obtain 30-300 g of a mixed base solution;

[0009] (4) pumping the mixed bottom liquid in step (3) into the reactor, and simultaneously and rapidly adding the dilute palladium nitrate solution and the reducing solution to the mixed bottom liquid under stirring conditions, and then continuing the reaction for 20 to 30 minutes. After the reaction is completed, a reaction slurry containing palladium powder is obtained;

[0010] (5) The reaction slurry was allowed to stand for 30 minutes and then filtered, washed with deionized water several times until the conductivity was less than 10 μS / cm, and the obtained solid was placed in a vacuum drying oven and dried at 70°C for 12 hours to obtain spherical palladium powder particles with a particle size of 100 to 600 nm. The palladium powder yield was 99.3% to 99.8%. The obtained palladium powder had a high yield, and the particles were spherical and highly dispersed.

[0011] In the method for preparing highly dispersible submicron spherical palladium powder, the mass concentration of the dilute palladium nitrate solution in step (1) is 1 to 10% calculated as elemental palladium.

[0012] Furthermore, the dilute palladium nitrate solution in step (1) is obtained by adding 40 to 460 g of dilute nitric acid with a concentration of 1% by weight to 10 g of palladium nitrate and mixing thoroughly.

[0013] In the method for preparing highly dispersible submicron spherical palladium powder, the molar ratio of the reducing agent to palladium nitrate in step (2) is 2.5:1 to 5:1.

[0014] Furthermore, the reducing solution in step (2) is obtained by dissolving 10.8-30 g of ascorbic acid or hydrazine hydrate in 40-400 g of deionized water.

[0015] In the method for preparing highly dispersible submicron spherical palladium powder, in step (3), the amount of dispersant used is 1 to 10% of the mass of palladium; and the amount of additive used is 1 to 10% of the mass of palladium.

[0016] The method for preparing highly dispersible submicron spherical palladium powder comprises the following steps: the reaction temperature in step (4) is 20-70°C, the addition time of the dilute palladium nitrate solution and the reducing solution is 30-60s, and the stirring speed during the reaction is 400-600r / min.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention disperses the palladium powder generated during the reaction by adding an organic polymer and a small molecule alcohol, so that the prepared palladium powder has high dispersibility.

[0019] 2. During the preparation process of the present invention, the reaction temperature, the concentration of the reducing agent and the reaction time are controlled to fully reduce the palladium nitrate to palladium powder, thereby ensuring that the yield of the palladium powder is not less than 99%, reducing losses and lowering costs.

[0020] 3. The present invention adopts a feeding method in which the oxidant and the reducing agent are added to the bottom liquid at the same time. On this basis, by controlling the reaction temperature, the concentration of the reactants, and the concentration of the dispersant and the additive, the intrinsic process of the nucleation and growth of the palladium powder is effectively regulated, so that the obtained palladium powder particles have high sphericity and a particle size of submicron level. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the submicron spherical palladium powder of Example 1 of the present invention;

[0022] Figure 2 This is a scanning electron microscope image of the submicron spherical palladium powder of Example 2 of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, but the protection scope of the present invention is not limited to these embodiments.

[0024] Example 1

[0025] The method for preparing highly dispersible submicron spherical palladium powder in this embodiment includes the following steps:

[0026] (1) Weigh 10 g of solid palladium nitrate and dissolve it in 460 g of 1% wt. dilute nitric acid. Mix thoroughly to prepare a dilute palladium nitrate solution for use. The mass concentration of palladium in the solution is 1%.

[0027] (2) According to the molar ratio of reducing agent to palladium nitrate of 2.5:1, 20g of ascorbic acid was weighed and dissolved in 400g of deionized water, and the mixture was thoroughly mixed to prepare a reducing solution for use.

[0028] (3) Weigh 0.25 g of polyvinyl pyrrolidone and dissolve it in a small amount of deionized water to obtain a dispersant solution. Weigh 0.25 g of methanol and dissolve it in a small amount of deionized water to obtain an additive solution. The dispersant solution and the additive solution are mixed and stirred evenly. Deionized water is then added to obtain 300 g of a mixed base solution. In this embodiment, the dispersant used is polyvinyl pyrrolidone, and the additive is methanol. The amount of the dispersant and the additive used is 5% of the mass of the palladium.

[0029] (4) The mixed bottom liquid was pumped into the reactor, heated, and stirred. At a speed of 500 r / min and a temperature of 70°C, the dilute palladium nitrate solution and the reducing solution were rapidly added to the mixed bottom liquid. After the addition was completed, the reaction was continued for 20 minutes. After the reaction was completed, a reaction slurry containing palladium powder was obtained. In this embodiment, the dilute palladium nitrate solution and the reducing solution were added for 60 seconds.

[0030] (5) The reaction slurry was allowed to stand for 30 minutes and then filtered, and washed repeatedly with deionized water until the conductivity reached 8 μS / cm. The obtained solid was placed in a vacuum drying oven and vacuum dried at 70°C for 12 hours to obtain palladium powder particles.

[0031] The yield of palladium powder prepared by the method of this embodiment is 99.5%. The obtained palladium powder has good dispersibility, spherical particles and a particle size of 200 to 400 nm. Figure 1 .

[0032] Example 2

[0033] The method for preparing highly dispersible submicron spherical palladium powder in this embodiment includes the following steps:

[0034] (1) Weigh 10 g of solid palladium nitrate and dissolve it in 160 g of 1% wt. dilute nitric acid. Mix thoroughly to prepare a dilute palladium nitrate solution for use. The mass concentration of palladium in the solution is 3%.

[0035] (2) According to the molar ratio of reducing agent to palladium nitrate of 4:1, 30g of ascorbic acid was weighed and dissolved in 140g of deionized water. After thorough mixing, the reducing solution was prepared for use.

[0036] (3) Weigh 0.5 g of Tween 80 and dissolve it in a small amount of deionized water to obtain a dispersant solution. Weigh 0.5 g of n-propanol and dissolve it in a small amount of deionized water to obtain an additive solution. The dispersant solution and the additive solution are mixed and stirred evenly. Deionized water is then added to obtain 200 g of a mixed base solution. In this example, the dispersant used is Tween 80, and the additive is n-propanol. The amount of the dispersant and the additive used is 10% of the mass of the palladium.

[0037] (4) The mixed bottom liquid was pumped into the reactor, heated, and stirred. At a speed of 600 r / min and a temperature of 50°C, the dilute palladium nitrate solution and the reducing solution were rapidly added to the mixed bottom liquid. After the addition was completed, the reaction was continued for 30 minutes. After the reaction was completed, a reaction slurry containing palladium powder was obtained. In this embodiment, the dilute palladium nitrate solution and the reducing solution were added for 30 seconds.

[0038] (5) The reaction slurry was allowed to stand for 30 minutes and then filtered, and washed repeatedly with deionized water until the conductivity reached 9 μS / cm. The obtained solid was placed in a vacuum drying oven and vacuum dried at 70°C for 12 hours to obtain palladium powder particles.

[0039] The yield of palladium powder prepared by the method of this embodiment is 99.3%. The obtained palladium powder has good dispersibility, spherical particles and a particle size of 300 to 600 nm. Figure 2 .

[0040] Example 3

[0041] The method for preparing highly dispersible submicron spherical palladium powder in this embodiment includes the following steps:

[0042] (1) Weigh 10 g of solid palladium nitrate and dissolve it in 40 g of 1% wt. dilute nitric acid. Mix thoroughly to prepare a dilute palladium nitrate solution for use. The mass concentration of palladium in the solution is 10%.

[0043] (2) According to the molar ratio of reducing agent to palladium nitrate of 5:1, 10.8g of hydrazine hydrate was weighed and dissolved in 40g of deionized water. After thorough mixing, the reducing solution was prepared for use.

[0044] (3) Weigh 0.05 g of polyethylene glycol and dissolve it in a small amount of deionized water to obtain a dispersant solution. Weigh 0.05 g of ethanol and dissolve it in a small amount of deionized water to obtain an additive solution. The dispersant solution and the additive solution are mixed and stirred evenly. Deionized water is then added to obtain 30 g of a mixed base solution. In this embodiment, the dispersant used is polyethylene glycol and the additive is ethanol. The amount of the dispersant and additive used is 1% of the mass of the palladium.

[0045] (4) The mixed bottom liquid is pumped into the reactor, heated, and stirred. At a speed of 400 r / min and a temperature of 20°C, the dilute palladium nitrate solution and the reducing solution are rapidly added to the mixed bottom liquid. After the addition is completed, the reaction is continued for 30 minutes. After the reaction is completed, a reaction slurry containing palladium powder is obtained. In this embodiment, the dilute palladium nitrate solution and the reducing solution are added for 30 seconds.

[0046] (5) The reaction slurry was allowed to stand for 30 minutes and then filtered, and washed repeatedly with deionized water until the conductivity reached 8 μS / cm. The obtained solid was placed in a vacuum drying oven and vacuum dried at 70°C for 12 hours to obtain palladium powder particles.

[0047] The yield of palladium powder prepared by the method of this embodiment is 99.8%. The obtained palladium powder has good dispersibility, spherical particles, and a particle size of 100 to 200 nm.

[0048] Those skilled in the art can intuitively understand other advantages and effects of the present invention from the contents described in this specification. The details of this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Claims

1. A method for preparing highly dispersible submicron spherical palladium powder, characterized by: Includes the following steps (1) Weighing solid palladium nitrate and dissolving it in dilute nitric acid, and mixing thoroughly to prepare a dilute palladium nitrate solution; (2) dissolving a reducing agent in deionized water and mixing thoroughly to prepare a reducing solution, wherein the reducing agent is ascorbic acid or hydrazine hydrate; (3) Weighing a dispersant and an additive separately, dissolving each in deionized water to obtain a dispersant solution and an additive solution, wherein the dispersant is Tween 80 and the additive is n-propanol; then mixing the dispersant solution and the additive solution, stirring evenly, to obtain a mixed base solution; (4) The mixed bottom liquid is pumped into the reactor, and the dilute palladium nitrate solution and the reducing solution are quickly added to the mixed bottom liquid simultaneously under stirring conditions, and then the reaction is continued for 20 to 30 minutes. After the reaction is completed, a reaction slurry containing palladium powder is obtained; (5) The reaction slurry was allowed to stand for 30 minutes and then filtered, washed with deionized water several times until the conductivity was less than 10 μS / cm, and the obtained solid was placed in a vacuum drying oven and dried at 70°C for 12 hours to obtain spherical palladium powder particles with a particle size of 100 to 600 nm; The mass concentration of the dilute palladium nitrate solution in step (1) is 1 to 10% calculated as elemental palladium; The dilute palladium nitrate solution in step (1) is obtained by adding 40 to 460 g of dilute nitric acid with a concentration of 1% by weight to 10 g of palladium nitrate and mixing thoroughly; In step (2), the molar ratio of the reducing agent to palladium nitrate is 2.5:1 to 5:1; The reducing solution in step (2) is obtained by dissolving 10.8-30 g of ascorbic acid or hydrazine hydrate in 40-400 g of deionized water; In the step (3), the amount of the dispersant is 1 to 10% of the mass of the palladium; the amount of the additive is 1 to 10% of the mass of the palladium; The reaction temperature in step (4) is 20-70° C., the addition time of the dilute palladium nitrate solution and the reducing solution is 30-60 s, and the stirring speed during the reaction is 400-600 r / min.

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