Ultrafine copper powder, its preparation method and application

Abstract

The application provides a kind of superfine copper powder and its preparation method and application, the preparation method of the above-mentioned superfine copper powder uses two-step liquid phase reduction method to prepare superfine copper powder, and improves process conditions, using dropwise feeding mode. Among them, the first step uses alkaline ascorbic acid solution to reduce copper chloride to cuprous chloride with narrow particle size distribution; the second step uses ferrous sulfate and sodium citrate as mixed reducing agent, and sodium citrate can also be used as a complexing agent, which helps to reduce the cuprous chloride to spherical, well-dispersed, uniform particle size distribution of superfine copper powder. At the same time, the raw materials used by the application are easy to obtain, the reaction process is mild, and organic solvents and toxic and hazardous reagents such as sodium borohydride and hydrazine hydrate are not needed, the preparation process has cost effectiveness, is friendly to the environment, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precious metal powder materials, and particularly relates to a superfine copper powder and a preparation method and application thereof. BACKGROUND

[0002] Nowadays, conductive paste has been widely applied in the field of microelectronic industry such as conductive adhesive, ceramic capacitor, etc. The conductive phase in the conductive paste is extremely important, which is mainly a precious metal such as silver powder and gold powder with good conductivity, oxidation resistance and ductility. The price of these metals is increasingly high, and there is a silver ion migration phenomenon in the electronic silver paste, which makes the electronic device have the risk of short circuit failure. The copper powder can greatly reduce the industrial cost and has more market advantages due to its high conductivity, low price, low electrochemical migration and good adhesion and weldability. In addition, the superfine copper powder has potential application value in the fields of catalysis and medicine due to its surface interface effect, quantum tunneling effect and oxidative stress effect.

[0003] At present, the preparation methods of the superfine copper powder include physical method and chemical method. The physical method refers to crushing bulk copper elemental powder into fine copper powder under physical force, including high-energy ball milling method and magnetron sputtering method. The physical method has high requirements for equipment and technology, low production efficiency, and uncontrolled copper powder morphology and particle size. The chemical method is to generate copper molecules through oxidation-reduction reaction or decomposition reaction, and then obtain superfine copper powder through nucleation growth, including thermal decomposition method, electrochemical method, liquid phase reduction method, polyol method and microemulsion method. Among them, the liquid phase reduction method has more industrial application prospects due to its short process flow, low manufacturing cost, high yield and controllable powder morphology and particle size. The liquid phase reduction method is to gradually generate micron or nanoscale metal powder by controlling the reaction conditions and reducing the metal cation solution under the action of reducing agent. However, in the preparation process of the superfine copper powder, the commonly used reducing agents include formaldehyde, sodium hypophosphite, sodium borohydride and hydrazine hydrate, which are often not environmentally friendly.

[0004] Therefore, it is urgent to develop a cost-effective and environmentally friendly process to prepare superfine copper powder with regular particle size distribution and good dispersion to meet the application requirements of customers. SUMMARY

[0005] The present application aims to solve the technical problems that the sphericity is difficult to guarantee and the particle size is difficult to control in the preparation process of the existing silver powder.

[0006] To solve the above technical problems, the present application first provides a preparation method of superfine copper powder, which comprises the following steps:

[0007] S1, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing the dispersant and stirred, and water bath heating treatment is carried out at 30-80 DEG C, after the reaction is completed, the supernatant is removed, and a suspension containing cuprous chloride precipitate is obtained;

[0008] S2, the mixed solution containing ferrous sulfate and sodium citrate is added dropwise into the suspension, after the reaction is completed, solid-liquid separation is carried out to obtain a precipitate, and then the precipitate is washed and dried to obtain the ultrafine copper powder.

[0009] Preferably, the step S1 specifically comprises:

[0010] S11, copper chloride is added into deionized water and stirred to dissolve, and a copper chloride solution is obtained;

[0011] S12, ascorbic acid is dissolved in water, and sodium hydroxide is added to obtain an alkaline ascorbic acid solution;

[0012] S13, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing the dispersant, and water bath heating treatment is carried out at 30-80 DEG C.

[0013] Preferably, in the step S11, the concentration of copper chloride in the copper chloride solution is 0.1-4.0 mol / L.

[0014] Preferably, in the step S12, the concentration of ascorbic acid in the alkaline ascorbic acid solution is 0.1-1.8 mol / L, and the pH value of the alkaline ascorbic acid solution is 7.5-11.5.

[0015] Preferably, in the step S1, the molar ratio of the copper chloride solution to the alkaline ascorbic acid solution is 1: (1-1.2).

[0016] Preferably, in the step S1, the dispersant is at least one of glycerol, polyethylene glycol, gelatin, gum arabic, polyvinylpyrrolidone and Tween-80; the mass content of the dispersant is greater than 0 and less than or equal to 5.0% based on 100% of the theoretical mass of the ultrafine copper powder.

[0017] Preferably, in the step S2, the molar ratio of ferrous sulfate in the mixed solution to copper chloride in the copper chloride solution is 1: (1.5-3), and the molar ratio of sodium citrate in the mixed solution to copper chloride in the copper chloride solution is 1: (1.5-3).

[0018] Preferably, the dropping time in the S1 step is 1 min to 30 min, and the stirring speed is 100 rad / min to 600 rad / min; the dropping time in the S2 step is 1 min to 30 min, the stirring speed is 100 rad / min to 600 rad / min, and the reaction temperature is 30 ℃ to 80 ℃.

[0019] Correspondingly, the application further provides a superfine copper powder prepared by the preparation method of the superfine copper powder according to any one of the above.

[0020] Correspondingly, the application further provides an application of the superfine copper powder according to the above in preparation of conductive paste.

[0021] The application has the following beneficial effects: Different from the prior art, the application provides a superfine copper powder, a preparation method and an application thereof. The preparation method of the superfine copper powder uses a two-step liquid-phase reduction method to prepare the superfine copper powder, and improves the process conditions by using a dropping feeding mode. In the first step, the copper chloride is reduced to cuprous chloride with a narrow particle size distribution by using an alkaline ascorbic acid solution; in the second step, ferrous sulfate and sodium citrate are used as a mixed reducing agent, and the sodium citrate can also be used as a complexing agent, which helps to reduce the cuprous chloride to superfine copper powder with a spherical shape, good dispersity and uniform particle size distribution. Meanwhile, the raw materials used in the application are easy to obtain, the reaction process is mild, and no organic solvent or toxic and hazardous reagents such as sodium borohydride and hydrazine hydrate are needed. The preparation process has cost-effectiveness, is friendly to the environment, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The preparation method of the superfine copper powder provided in the embodiments of the application is shown in the flowchart.

[0023] Figure 2 The SEM image of the superfine copper powder prepared in Embodiment 1 of the application is shown in the figure.

[0024] Figure 3 The SEM image of the superfine copper powder prepared in Embodiment 2 of the application is shown in the figure.

[0025] Figure 4 The SEM image of the superfine copper powder prepared in Embodiment 3 of the application is shown in the figure. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0027] In view of the technical problem that the reducing agent used in the process of preparing ultrafine copper powder by the liquid phase reduction method is not environmentally friendly, the present application aims to provide an ultrafine copper powder, a preparation method and application thereof, which are mainly based on a two-step liquid phase reduction method, and the ultrafine copper powder with spherical shape, good dispersibility and uniform particle size distribution is prepared by improving the process conditions. The method is safe and environmentally friendly, has mild reaction conditions, and is suitable for industrial production.

[0028] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0029] In a first aspect, the present application provides a preparation method of ultrafine copper powder.

[0030] Please refer to Figure 1 , Figure 1 The preparation method of ultrafine copper powder provided by the embodiments of the present application is shown in the flow chart; and the preparation method specifically includes:

[0031] S1, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing the dispersant for stirring, and water bath heating treatment is carried out at 30-80 DEG C. After the reaction is completed, the supernatant is removed, and a suspension containing cuprous chloride precipitate is obtained.

[0032] Specifically, the step S1 further includes:

[0033] S11, adding copper chloride into the deionized water and stirring to dissolve, to obtain a copper chloride solution;

[0034] S12, dissolving ascorbic acid in water and adding sodium hydroxide to obtain an alkaline ascorbic acid solution;

[0035] S13, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing the dispersant, and water bath heating treatment is carried out at 30-80 DEG C.

[0036] In the step S11, the concentration of copper chloride in the copper chloride solution is 0.1-4.0 mol / L.

[0037] In the S12 step: the ascorbic acid concentration of the basic ascorbic acid solution is 0.1 mol / L to 1.8 mol / L, and the pH value of the basic ascorbic acid solution is 7.5 to 11.5; wherein, the basic ascorbic acid solution can be used to reduce copper chloride to cuprous chloride with a narrow particle size distribution.

[0038] Specifically, the molar ratio of the copper chloride solution to the basic ascorbic acid solution is 1: (1-1.2); wherein, ascorbic acid as a reducing agent, appropriate excess can ensure that copper chloride is fully reduced to cuprous chloride, and improve the conversion rate of the reaction. If the amount of ascorbic acid is insufficient, it may lead to incomplete reaction of copper chloride. Slightly excessive ascorbic acid helps to reduce the occurrence of side reactions and avoid the generation of other unnecessary impurities, thereby improving the purity of the cuprous chloride product. Although the excess of ascorbic acid is beneficial to the reaction, too much excess will increase the cost, and the ratio is controlled at 1: (1-1.2), which can ensure the reaction effect, and also can better control the cost and improve the efficiency.

[0039] In the S1 step: the dispersant is at least one of glycerol, polyethylene glycol, gelatin, gum arabic, polyvinylpyrrolidone and Tween-80; wherein, the main role of the dispersant is to prevent silver powder particle agglomeration, improve particle dispersibility, control particle morphology and stabilize the solution system. By selecting a suitable dispersant, the quality, uniformity and processing performance of copper powder can be significantly improved, thereby optimizing its application effect in the fields of photovoltaic, electronic and the like.

[0040] Specifically, the mass content of the dispersant is greater than 0 and less than or equal to 5.0wt% based on 100wt% of the theoretical mass of the ultra-fine copper powder; wherein, too low mass content of the dispersant may not be able to fully play the role of the dispersant, leading to poor dispersion effect of the copper powder particles; at the same time, too much dispersant may have adverse effects on other aspects of the reaction system, such as affecting the purity of the product, changing the physical and chemical properties of the solution, or causing additional difficulties in the subsequent processing process.

[0041] Preferably, the dropping time in the S1 step is 1min to 30min, and the stirring speed is 100rad / min to 600rad / min.

[0042] Specifically, a longer dropping time (such as 30min) can make the reactants mix more uniformly, which is helpful for the smooth progress of the reaction and reduces uneven reaction caused by too high or too low local concentration. A shorter dropping time (such as 1min) may be suitable for situations where the reaction speed is required to be high or the concentration of the reactants is low, so as to complete the reaction as soon as possible. By adjusting the dropping time, the reaction rate can be controlled to a certain extent, avoiding too violent or too slow reaction, thereby being conducive to the generation and control of the product properties.

[0043] Specifically, a lower stirring speed (e.g., 100 rad / min) can be sufficient to achieve uniform mixing when the reactant concentration is low or the reaction is relatively mild. A higher stirring speed (e.g., 600 rad / min) can ensure that the components in the solution are rapidly and sufficiently contacted to facilitate the reaction, especially when the reactant concentration is high or more intense mixing is required. A suitable stirring speed can facilitate the transport of reactants and products in the solution, avoid the formation of concentration gradients, and thus improve the efficiency and consistency of the reaction.

[0044] S2, the mixed solution containing ferrous sulfate and sodium citrate is added dropwise into the suspension, and after the reaction is completed, solid-liquid separation is performed to obtain a precipitate, which is then washed and dried to obtain the ultrafine copper powder.

[0045] Specifically, the S2 step further comprises:

[0046] The mixed solution containing ferrous sulfate and sodium citrate is added dropwise into the suspension, and the reaction temperature is 30-80°C. After the reaction is completed, solid-liquid separation is performed to obtain a precipitate, which is then washed and dried to obtain the ultrafine copper powder.

[0047] Specifically, in the S2 step: the molar ratio of ferrous sulfate in the mixed solution to copper chloride in the copper chloride solution is 1:(1.5-3); the molar ratio of sodium citrate in the mixed solution to copper chloride in the copper chloride solution is 1:(1.5-3); wherein ferrous sulfate and sodium citrate are used as mixed reducing agents, and sodium citrate can also act as a complexing agent, which helps to reduce copper(I) chloride to ultrafine copper powder with a spherical shape, good dispersibility, and uniform particle size distribution.

[0048] Further, if the amount of ferrous sulfate is too much, it can increase the cost and may trigger some unnecessary side reactions; and if the amount of ferrous sulfate is too small, it cannot complete the reduction.

[0049] Further, sodium citrate can form complexes with certain ions in the solution, which can stabilize the solution system, control the reaction rate, and improve the performance of the product. A larger amount can better play this complexing and stabilizing role. An appropriate excess of sodium citrate can help inhibit the generation of impurities and improve the purity of the product.

[0050] Further, a reaction temperature of 30-80°C can help control the crystallization and growth of copper powder, thereby affecting its particle size, morphology, and performance.

[0051] Preferably, the dropwise addition time in the S2 step is 1-30 min, and the stirring speed is 100-600 rad / min.

[0052] Correspondingly, the application further provides a superfine copper powder prepared by the preparation method of the superfine copper powder according to any one of the above; wherein the particle size of the superfine copper powder is 1-2 μm, and the tap density is 3.7-3.9 g / ml.

[0053] Correspondingly, the application further provides an application of the superfine copper powder in preparing a conductive paste.

[0054] The technical solutions of the application will be further described in combination with specific embodiments.

[0055] Embodiment 1:

[0056] The embodiment 1 provides a preparation method of a superfine copper powder, and the specific preparation steps are as follows:

[0057] Step 1: 19 g of copper chloride is weighed and added into 250 mL of deionized water for stirring and dissolving;

[0058] Step 2: 30 g of ascorbic acid is dissolved in 250 mL of water, 7.1 g of sodium hydroxide is added to adjust the solution, and a first reduction solution is obtained;

[0059] Step 3: 0.1 g of glycerol is added into 100 mL of deionized water in a 50℃ constant temperature water bath, and the copper chloride solution in step 1 and the first reduction solution in step 2 are simultaneously added into the water containing glycerol through a peristaltic pump, the dropping time is 30 min, the stirring rate is 550 rad / min, after the reaction is completed, the solution is left to stand for 5 min, the supernatant is removed, and a cuprous chloride suspension containing white cuprous chloride precipitate is obtained;

[0060] Step 4: 27 g of ferrous sulfate and 73 g of sodium citrate are dissolved in 300 mL of deionized water to prepare a second reduction solution; the second reduction solution is added into the cuprous chloride suspension, the dropping time is controlled to be 30 min, and the reaction temperature is 50℃; after the reaction is completed, solid-liquid separation is carried out, the superfine copper powder is obtained after being washed for multiple times and dried.

[0061] Embodiment 2:

[0062] The embodiment 2 provides a preparation method of a superfine copper powder, and the specific preparation steps are as follows:

[0063] Step 1: 15 g of copper chloride is weighed and added into 200 mL of deionized water for stirring and dissolving;

[0064] Step 2: 24 g of ascorbic acid is dissolved in 200 mL of water, 5.7 g of sodium hydroxide is added to adjust the solution, and a first reduction solution is obtained;

[0065] Step 3: At room temperature, the copper chloride solution from Step 1 and the first reducing solution from Step 2 are simultaneously added dropwise to 100 mL of deionized water using a peristaltic pump. The addition time is 30 min, the stirring rate is 550 rad / min, and after the reaction is completed, the mixture is allowed to stand for 5 min. The supernatant is then removed to obtain a cuprous chloride suspension containing a white cuprous chloride precipitate.

[0066] Step 4: Dissolve 25.2g of ferrous sulfate and 42.6g of sodium citrate in 200mL of deionized water to prepare a second reducing solution; add the second reducing solution dropwise to a cuprous chloride suspension, controlling the dropwise addition time to 1min, and the reaction temperature to 25℃; after the reaction is complete, perform solid-liquid separation, wash several times, and dry to obtain ultrafine copper powder.

[0067] Example 3:

[0068] This embodiment 3 provides a method for preparing ultrafine copper powder, the specific preparation steps of which are as follows:

[0069] Step 1: Weigh 19g of copper chloride and add it to 250mL of deionized water and stir to dissolve.

[0070] Step 2: Dissolve 30g of ascorbic acid in 250mL of water, add 7.1g of sodium hydroxide to adjust the solution, and obtain the first reducing solution;

[0071] Step 3: In a 50℃ constant temperature water bath, the copper chloride solution from Step 1 and the first reducing solution from Step 2 are simultaneously added dropwise to 100mL of deionized water using a peristaltic pump. The addition time is 30min, the stirring rate is 550rad / min, and after the reaction is completed, the mixture is allowed to stand for 5min. The supernatant is then removed to obtain a cuprous chloride suspension containing a white cuprous chloride precipitate.

[0072] Step 4: Dissolve 27g of ferrous sulfate and 73g of sodium citrate in 300mL of deionized water to prepare a second reducing solution; add the second reducing solution dropwise to a cuprous chloride suspension, controlling the dropwise addition time to 30min, and the reaction temperature to 50℃; after the reaction is complete, perform solid-liquid separation, wash several times, and dry to obtain ultrafine copper powder.

[0073] Please see Figure 2 , Figure 2 This is a SEM (scanning electron microscope) image of the ultrafine copper powder prepared in Example 1 of the present invention; wherein, from Figure 2 As can be seen, the ultrafine copper powder prepared in Example 1 of this invention is spherical, with a smooth surface, high crystallinity, and relatively uniform particle size distribution. The average particle size is about 1.5 μm, and it has good dispersibility, no agglomeration, and a tap density of up to 3.9 g / ml.

[0074] Please see Figure 3 , Figure 3SEM image of the ultra-fine copper powder prepared in Example 2 of the present application; it can be seen from Figure 3 that the average particle size of the ultra-fine copper powder prepared in Example 2 of the present application is about 1 μm, the particle size distribution is relatively narrow, the crystal is compact, and the tap density reaches 3.7 g / ml.

[0075] Please refer to Figure 4 , Figure 4 SEM image of the ultra-fine copper powder prepared in Example 3 of the present application; it can be seen from Figure 4 that in the case of no dispersant and slow feeding, the particle size uniformity of the ultra-fine copper powder prepared in Example 3 of the present application is poor, two particle size distributions (2 μm and 1 μm) appear, and the small particle crystals have agglomeration phenomenon.

[0076] In summary, different from the prior art, the present application provides an ultra-fine copper powder, a preparation method and application thereof. The preparation method of the ultra-fine copper powder uses a two-step liquid phase reduction method to prepare the ultra-fine copper powder, and the process conditions are improved, and a dropwise feeding mode is adopted. In the first step, the copper chloride is reduced to cuprous chloride with a relatively narrow particle size distribution by using an alkaline ascorbic acid solution; in the second step, ferrous sulfate and sodium citrate are used as a mixed reducing agent, and the sodium citrate can also be used as a complexing agent, which helps to reduce the cuprous chloride to a spherical ultra-fine copper powder with good dispersibility and uniform particle size distribution. At the same time, the raw materials used in the present application are easy to obtain, the reaction process is mild, and no organic solvents and toxic and hazardous reagents such as sodium borohydride and hydrazine hydrate are needed, the preparation process has cost-effectiveness, is environmentally friendly, is suitable for industrial production, and can further promote the commercial development.

[0077] The raw materials listed in the present application, the upper and lower limits, interval values of the raw materials of the present application, and the upper and lower limits, interval values of the process parameters (such as temperature, time, etc.) can all achieve the present application, and examples are not listed one by one.

[0078] It should be noted that each of the above examples belongs to the same inventive concept, and the description of each example has its own emphasis, and the description in individual examples is not exhaustive. Reference can be made to the description in other examples.

[0079] The above examples only express the implementation of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A method for preparing ultrafine copper powder, characterized by, It comprises the following steps: S1, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing a dispersant for stirring, and water bath heating treatment is carried out at 30-80℃, after the reaction is completed, the supernatant is removed, and a suspension containing cuprous chloride precipitate is obtained; S2, a mixed solution containing ferrous sulfate and sodium citrate is added dropwise into the suspension, after the reaction is completed, solid-liquid separation is carried out to obtain a precipitate, and then the precipitate is washed and dried to obtain ultrafine copper powder; The S1 step specifically comprises: S11, copper chloride is added into deionized water and stirred and dissolved to obtain the copper chloride solution; S12, ascorbic acid is dissolved in water, and sodium hydroxide is added to obtain the alkaline ascorbic acid solution; the ascorbic acid concentration of the alkaline ascorbic acid solution is 0.1-1.8 mol / L, and the pH value of the alkaline ascorbic acid solution is 7.5-11.5; S13, the copper chloride solution and the alkaline ascorbic acid solution are simultaneously added dropwise into the deionized water containing a dispersant, and water bath heating treatment is carried out at 30-80℃.

2. The method of claim 1, wherein the copper powder has a particle size of 0.1 to 1 μm. In the S11 step, the copper chloride concentration of the copper chloride solution is 0.1-4.0 mol / L.

3. The method of claim 1, wherein the copper powder has a particle size of 0.1 to 1 μm. In the S1 step, the molar ratio of the copper chloride solution to the alkaline ascorbic acid solution is 1: (1-1.2).

4. The method of claim 1, wherein the copper powder has a particle size of 0.1 to 1 μm. In the S1 step, the dispersant is at least one of glycerol, polyethylene glycol, gelatin, gum arabic, polyvinylpyrrolidone and Tween-80; the mass content of the dispersant is greater than 0 and less than or equal to 5.0% based on 100% of the theoretical mass of the ultrafine copper powder.

5. The method of claim 1, wherein the copper powder has a particle size of 0.1 to 1 μm. In the S2 step, the molar ratio of ferrous sulfate in the mixed solution to copper chloride in the copper chloride solution is 1: (1.5-3), and the molar ratio of sodium citrate in the mixed solution to copper chloride in the copper chloride solution is 1: (1.5-3).

6. The method of claim 1, wherein the copper powder has a particle size of 0.1 to 1 μm. The dropwise adding time in the S1 step is 1-30 min, and the stirring speed is 100-600 rad / min; the dropwise adding time in the S2 step is 1-30 min, the stirring speed is 100-600 rad / min, and the reaction temperature is 30-80℃.

7. An ultrafine copper powder, characterized by, The ultrafine copper powder is prepared by the preparation method of the ultrafine copper powder according to any one of claims 1-6; wherein the particle size of the ultrafine copper powder is 1-2 μm, and the tap density is 3.7-3.9 g / ml.

8. Use of the ultrafine copper powder according to claim 7 in the preparation of conductive paste.

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