阅读说明：本技术 一种铜基包覆粉末及其制备方法 (Copper-based coating powder and preparation method thereof ) 是由 祝伟 江志 张煦 周嘉诚 张敬国 张彬 穆艳如 刘祥庆 汪礼敏 于 2020-12-30 设计创作，主要内容包括：本发明提供一种铜基包覆粉末及其制备方法,属于导电材料技术领域,该铜基包覆粉末由芯部C和壳层S；所述的芯部C主成分为铜,铜含量的质量分数大于99.0％,其余为杂质；所述的壳层S主成分为银,银含量的质量分数大于99.5％,其余为杂质；所述的芯部C粒径为4μm-10μm；所述的壳层S厚度为150nm-250nm；所述的壳层S对芯部C的包覆率大于90％,且壳层S和芯部C的质量比S/C为0.08-0.16；本发明主要通过优化所得包覆粉末的结构组成,在相同银含量的情况下,来显著提升银包覆粉末的抗氧化性和降低电阻率。(The invention provides copper-based coating powder and a preparation method thereof, belonging to the technical field of conductive materials, wherein the copper-based coating powder comprises a core C and a shell S; the core C mainly contains copper, the mass fraction of the copper content is more than 99.0%, and the balance is impurities; the shell S mainly contains silver, the mass fraction of the silver content is more than 99.5%, and the balance is impurities; the particle size of the core C is 4-10 μm; the thickness of the shell layer S is 150nm-250 nm; the coating rate of the shell layer S to the core C is more than 90%, and the mass ratio S/C of the shell layer S to the core C is 0.08-0.16; the invention obviously improves the oxidation resistance and reduces the resistivity of the silver coating powder under the condition of the same silver content mainly by optimizing the structural composition of the obtained coating powder.)

1. A copper-based clad powder characterized in that: the copper-based coating powder consists of a core C and a shell S;

the core C mainly contains copper, the mass fraction of the copper content is more than 99.0%, and the balance is impurities;

the shell S mainly contains silver, the mass fraction of the silver content is more than 99.5%, and the balance is impurities.

2. Copper-based cladding powder according to claim 1,

the particle size of the core C is 4-10 μm;

the thickness of the shell layer S is 150nm-250 nm;

the coating rate of the shell layer S to the core C is more than 90%, and the mass ratio S/C of the shell layer S to the core C is 0.08-0.16.

3. A method for producing the copper-based clad powder according to claim 1, characterized in that the method for producing the copper-based clad powder comprises the steps of:

s101: selecting copper powder;

s102: copper powder pretreatment;

s103: uniformly dispersing copper powder in the solution;

s104: coating copper powder with silver in the solution;

s105: and (5) washing and drying the coated powder.

4. The method of preparing a coated powder according to claim 3, wherein:

in the step S101, the copper powder particles are dendritic, spherical or flaky;

5. the method of preparing a coated powder according to claim 3, wherein:

in step S102, the copper powder pretreatment process comprises the steps of removing oxides, hydroxides and organic protective layers on the surfaces of copper powder by using alkali water and an oil removal agent;

6. the method of preparing a coated powder according to claim 3, wherein:

in step S103, the copper powder uniform dispersion process includes using a dispersant.

Technical Field

The invention belongs to the technical field of conductive materials, and particularly relates to copper-based coating powder and a preparation method thereof.

Background

Silver powder is excellent in conductivity and oxidation resistance, is an extremely important industrial raw material, is made into conductive paste and is widely applied to industries such as electronic information and the like, but silver is expensive and easy to migrate, so that the development of a powder material which is low in cost, has conductivity close to that of silver and does not migrate is of great significance.

The silver-coated copper powder is generally prepared by chemically plating a layer of silver on the surface of copper powder to form a composite material with the surface being silver and the core being copper, it is a good high-conductivity filler, maintains the excellent conductivity of the copper powder and the silver powder, and overcomes the defects that the silver powder is easy to migrate and the copper powder is easy to oxidize in the using process, so the silver powder can be used for replacing the silver powder in some fields, however, the traditional preparation method of the silver-coated copper powder generally has the defects that the prepared silver coating effect is not good, a compact and uniform coating layer is difficult to form, the silver-coated copper powder has poor conductive effect and oxidation resistance, and the silver powder is replaced by the silver-coated copper powder in low amount when the silver-coated copper powder is applied and needs to be improved, in the existing silver-coated copper powder patents and documents, such as the patent publication No. CN 106148926A, "silver-coated copper powder and its preparation method", the preparation method of the silver-coated copper powder is studied more, and the plating layer structure and the oxidation resistance are not reported.

Therefore, it is necessary to invent a copper-based clad powder and a preparation method thereof.

Disclosure of Invention

In order to solve the technical problems, the invention provides copper-based coating powder and a preparation method thereof, and aims to solve the problems that the prepared silver coating effect is poor, a compact and uniform coating layer is difficult to form, the electric conduction effect and the oxidation resistance of the silver-coated copper powder are poor, and the amount of silver powder substituted by the silver powder is low in application and needs to be improved in the conventional preparation method of the silver-coated copper powder. A copper-based clad powder is composed of a core C and a shell S;

the core C mainly contains copper, the mass fraction of the copper content is more than 99.0%, and the balance is impurities;

the shell S mainly contains silver, the mass fraction of the silver content is more than 99.5%, and the balance is impurities.

Preferably, the particle size of the core C is 4-10 μm;

the thickness of the shell layer S is 150nm-250 nm;

the coating rate of the shell layer S to the core C is more than 90%, and the mass ratio S/C of the shell layer S to the core C is 0.08-0.16.

A method for preparing a copper-based clad powder, the method comprising the steps of:

s101: selecting copper powder;

s102: copper powder pretreatment;

s103: uniformly dispersing copper powder in the solution;

s104: coating copper powder with silver in the solution;

s105: and (5) washing and drying the coated powder.

Preferably, in step S101, the copper powder particles have a dendritic, spherical or flake shape;

preferably, in step S102, the copper powder pretreatment process includes removing oxides, hydroxides and organic protective layers on the surface of the copper powder by using alkali water and an oil remover;

preferably, in step S103, the process of uniformly dispersing the copper powder includes using a dispersant.

The silver-coated powder is prepared by adopting a two-step method, wherein silver nitrate is used as the necessary plating solution in the first step, silver ammonia solution is used as the necessary plating solution in the second step, and the temperature, the pH value, the concentration of a reducing agent and the concentration of the plating solution, particularly the adding rate of the plating solution, of a reaction system are controlled in a special interval, so that the coated powder with required special components and structures is prepared.

Compared with the prior art, the invention has the following beneficial effects:

the invention obviously improves the oxidation resistance and reduces the resistivity of the silver coating powder under the condition of the same silver content mainly by optimizing the structural composition of the obtained coating powder.

Drawings

Fig. 1 is a sectional scanning electron micrograph of the silver-coated powder.

FIG. 2 is a flow chart of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

example (b):

as shown in figures 1-2

The invention provides a copper-based coating powder, which consists of a core C and a shell S;

the core C mainly contains copper, the mass fraction of the copper content is more than 99.0%, and the balance is impurities;

the shell S mainly contains silver, the mass fraction of the silver content is more than 99.5%, and the balance is impurities.

In the embodiment, the particle size of the core C is 4-10 μm;

the thickness of the shell layer S is 150nm-250 nm;

the coating rate of the shell layer S to the core C is more than 90%, and the mass ratio S/C of the shell layer S to the core C is 0.08-0.16.

A method for preparing a copper-based clad powder, the method comprising the steps of:

s101: selecting copper powder;

s102: copper powder pretreatment;

s103: uniformly dispersing copper powder in the solution;

s104: coating copper powder with silver in the solution;

s105: and (5) washing and drying the coated powder.

In this embodiment, in step S101, the copper powder particles are dendritic, spherical or flaky;

in this embodiment, in step S102, the copper powder pretreatment process includes removing oxides, hydroxides, and organic protective layers on the surface of copper powder by using alkali water and an oil remover;

in this embodiment, in step S103, the process of uniformly dispersing the copper powder includes using a dispersant.

The preparation process comprises the following steps: selecting copper powder; copper powder pretreatment; uniformly dispersing copper powder in the solution; coating copper powder with silver in the solution; and (5) washing and drying the coated powder.

S101: copper powder selection:

the copper powder is prepared by adopting an electrochemical method, and the preparation process comprises an electrolysis process, a powder washing process, a drying process and a screening process.

The following explains the respective steps:

(1) an electrolysis process:

taking a pure copper plate as an anode for electrolysis, taking a cathode as a copper plate, a titanium plate or a lead plate and the like, dissolving an anode plate after electrifying, and separating out copper powder at the cathode;

(2) a powder washing procedure:

washing copper powder precipitated from the cathode by using pure water, and cleaning acidic substances attached to the surface of the copper powder;

(3) and (3) drying:

in this step, the dried electrolytic copper powder is obtained, and the drying method may be any method known to those skilled in the art, such as a reduction furnace, a drying furnace, etc.;

(4) screening process

The dried electrolytic copper powder is sieved by a method known to those skilled in the art, such as linear vibration sieving or rotary vibration sieving, to obtain electrolytic copper powder with a particle size of 4 μm to 10 μm, preferably 5 μm to 8 μm.

S102: copper powder pretreatment:

removing the oxide, hydroxide and organic protective layer on the surface of the copper powder by methods known to those skilled in the art, for example, by:

1. stirring and dispersing copper powder in deionized water;

2. adding a certain amount of ammonia water and a degreasing agent in sequence, stirring and washing;

s103: uniformly dispersing copper powder in the solution:

the pretreated copper powder is uniformly dispersed in deionized water using methods known to those skilled in the art, such as the following:

1. stirring the pretreated copper powder in deionized water for preliminary dispersion;

2. adding a dispersant known to those skilled in the art to the solution;

the preferable additives are gelatin, polyvinyl pyrrolidone and ethylene diamine tetraacetic acid disodium;

more preferred additives are disodium edetate;

further preferably, the specific gravity of the disodium ethylene diamine tetraacetate and the copper powder is 0.01-0.08;

s103: coating the copper powder with silver in the solution:

1. dropwise adding a silver nitrate solution into the water solution in which the copper powder is uniformly dispersed;

2. slowly pouring the reducing agent solution into the step S101;

3. adding the silver ammonia solution dropwise to step S102;

the temperature of the reaction system is preferably 26-33 ℃;

preferably, the reducing agent is glucose, ascorbic acid, potassium tartrate or formaldehyde, and more preferably potassium tartrate;

preferably, the pH value of the reaction system is 8 to 12, more preferably 9 to 11;

the concentration of the plating solution (silver nitrate solution and silver ammonia solution) is preferably 0.33mol/L-0.45 mol/L;

preferably, the adding speed of the plating solution (silver nitrate solution and silver ammonia solution) is 5mL/min-15 mL/min;

preferably, the concentration of the reducing agent is 25g/L-37 g/L;

s105: and (3) washing and drying the coated powder:

this step is to obtain a dry coating powder. The washing and drying methods may be any methods known to those skilled in the art, such as washing with alkali or pure water, and drying in a drying oven or an oven.

Example (b):

(1) selecting copper powder with a certain shape and a certain granularity, wherein the shape and the granularity data are shown in table 1 in detail;

(2) pretreating the surface of the copper powder to remove oxides, hydroxides and organic protective layers on the surface;

(3) the dispersant was chosen to disperse the copper powder evenly in the solution, the dispersant type is detailed in table 1.

(4) Copper powder is coated by sequentially utilizing silver nitrate solution, silver ammonia solution and reducing agent, and relevant process parameters are detailed in a table 1;

(5) washing and drying the coated powder;

the purity of the silver was calculated as follows: the obtained coated powder is sliced to prepare a sample, the cross-sectional morphology of the coated powder is observed by using a Field Emission Scanning Electron Microscope (FESEM) which is well known by a person skilled in the art, 3 observation areas with the length of 40 microns (length) by 20 microns (width) are randomly selected, 3 points of a silver coating layer in each observation area are taken by using an EDS (electronic data system) equipped in the FESEM for carrying out element mass analysis, and finally, the average value is taken;

the coating rate was calculated as follows: the obtained coated powder was sliced to prepare a sample, the cross-sectional morphology of the coated powder was observed by a Field Emission Scanning Electron Microscope (FESEM) known to those skilled in the art, 3 observation regions of 40 μm (long) × 20 μm (wide) were randomly selected, the total length of the coated and the total length of the uncoated copper powder particles in each of the three regions were determined, and the coating ratio was calculated as the ratio of the total length of the coated to the total length of the coated and the total length of the uncoated copper powder particles.

The thickness is calculated as follows: the obtained coated powder was sliced to prepare a sample, the cross-sectional morphology of the coated powder was observed by a Field Emission Scanning Electron Microscope (FESEM) known to those skilled in the art, 3 observation regions of 40 μm (length) × 20 μm (width) were randomly selected, the thickness of the silver coating layer of the coated particles in each region was counted by the length measurement function provided by the FESEM itself, and finally an average value was taken.

The specific gravity of silver and copper is calculated as follows: the coated powder was tested for copper and silver content, respectively, using electrolytic and silver chloride precipitation methods well known to those skilled in the art.

Oxygen content calculation mode: the oxygen content of the coated powder was tested using an oxygen analyzer known to those skilled in the art.

The resistivity calculation method comprises the following steps: the resistivity of the coated powder was tested using a resistivity tester known to those skilled in the art.

The composition and properties of the final coated powder are shown in table 2.

Comparative example 1

(1) Selecting copper powder with a certain shape and a certain granularity, wherein the shape and the granularity data are shown in table 1 in detail;

(2) pretreating the surface of the copper powder to remove oxides, hydroxides and organic protective layers on the surface;

(3) the dispersant was chosen to disperse the copper powder evenly in the solution, the dispersant type is detailed in table 1.

(4) Coating copper powder by using a silver nitrate solution, wherein relevant process parameters are detailed in a table 1;

(5) washing and drying the coated powder;

the test method is the same as that of the example section, and the data are shown in comparative examples 1-1 and 1-2.

Comparative example 2

(1) Selecting copper powder with a certain shape and a certain granularity, wherein the shape and the granularity data are shown in table 1 in detail;

(2) pretreating the surface of the copper powder to remove oxides, hydroxides and organic protective layers on the surface;

(3) the dispersant was chosen to disperse the copper powder evenly in the solution, the dispersant type is detailed in table 1.

(4) Coating the copper powder by using a silver ammonia solution and a reducing agent, wherein relevant process parameters are detailed in a table 1;

(5) the coated powder is washed and dried.

TABLE 1

Note: gelatin (A1), polyvinyl pyrrolidone (A2), disodium ethylene diamine tetraacetate (A3), glucose (B1), ascorbic acid (B2), potassium tartrate (B3), formaldehyde (B4)

TABLE 2

The technical solutions of the present invention or similar technical solutions designed by those skilled in the art based on the teachings of the technical solutions of the present invention are all within the scope of the present invention to achieve the above technical effects.