Nanorod, micro-nano particle and flaky mixed gold powder as well as preparation method and application of nanorod, micro-nano particle and flaky mixed gold powder

Abstract

The invention discloses a preparation method of nanorods, micro-nano particles and flaky mixed gold powder. The preparation method comprises the following steps: (1) taking ethylene glycol, high-purity water or a mixed solution of ethylene glycol and high-purity water as a solution a; (2) dissolving chloroauric acid in the solution a to obtain a solution b; (3) dissolving disodium ethylene diamine tetraacetate in the solution b to obtain a solution c; (4) dissolving polyvinylpyrrolidone in the solution c to obtain a solution d; (5) dissolving a reducing agent in the solution d to obtain a solution e; (6) adding sodium hydroxide into the solution e to obtain a solution f; (7) transferring the solution f into a polytetrafluoroethylene liner, and then performing hydrothermal reaction to prepare gold powder; and (8) washing, separating and drying the gold powder to prepare the gold powder with different shapes and sizes. The preparation method is simple, high-cost equipment is not needed, the batch morphology of the product is stable, and large-scale low-cost preparation of the gold powder is facilitated.

Description

Technical Field

[0001] The invention relates to a method for preparing micro-nano gold powder, and in particular to a nanorod, micro-nano particles and flaky mixed gold powder, a preparation method thereof and an application thereof in electronic paste. Technical Background

[0002] Gold electronic paste is mainly an electronic functional material used in electronic technology, which is mainly composed of gold powder, binder and organic solvent phase. We screen print the paste-like gold electronic paste on the substrate and then sinter it at high temperature to form a continuous film with a thickness of micrometers that acts as a conductor. We know that gold has high ductility, high chemical corrosion resistance and high temperature oxidation resistance. At the same time, gold electronic paste has the advantages of strong adhesion to the substrate or dielectric and low film porosity, which can maintain the stability of electronic components under harsh working conditions. Gold electronic paste is mainly used in the manufacture of integrated circuits, resistors, capacitors, filters, impedance converters, couplers, sensitive components and other electronic components in the aerospace and military industries. At present, most of the gold powder used in gold electronic paste relies on imports, which seriously restricts my country's independent control in key technology fields and national defense security.

[0003] It must be pointed out that the morphology and size of gold powder are key factors in manufacturing high-performance electronic components. For spherical particles with a diameter greater than 2 microns, the contact mode is point contact, which affects the density and conductivity of the film after sintering. Therefore, in order to improve the performance of the film after sintering, gold particles with a diameter of about 1 micron will help improve the density of the film after sintering and improve its conductivity at the same time. In addition, the presence of gold nanorods and micro-nanosheets also helps to connect adjacent gold particles, thereby improving the conductivity of the sintered film.

[0004] However, the gold powder used in electronic pastes currently prepared both domestically and internationally is composed of gold particles of a single morphology, or of larger-sized gold micron particles and micron flakes (1 to 5 microns), such as:

[0005] (1) CN115592125B discloses a method for preparing a gold powder in which micro-nano flakes and submicron particles coexist. The prepared flake gold powder is hexagonal and triangular in shape, with a diameter ranging from 1 to 5 microns and a thickness of 100 to 800 nanometers. The particle size of the spherical gold powder is 0.3 to 1.0 microns.

[0006] (2) CN109622985A discloses a method for preparing highly dispersed submicron gold powder, wherein the particle size of the prepared gold powder is 0.3 to 1.2 microns.

[0007] (3) CN106825606A discloses a method for preparing multi-sized monodisperse gold nanoparticles and their application, wherein the maximum particle size of the prepared gold nanoparticles is 90 to 120 nanometers.

[0008] However, the gold powder prepared by the preparation method disclosed in the existing patents often has poor dispersibility, a wide particle size distribution or a small particle size, and cannot meet the performance requirements of the electronic paste. Summary of the invention

[0009] The purpose of the present invention is to develop a method for synthesizing mixed micro-nano spherical and flaky and nanorod gold powders, so that the calcined film has higher density and conductivity, and solve the key technical problems faced by high-performance gold electronic pastes in my country.

[0010] In order to achieve the synthesis of highly dispersed nanorods, micro-nano particles and flaky mixed gold powder, the technical scheme adopted is as follows, and the specific steps include:

[0011] (1) Take a certain amount of ethylene glycol, high-purity water, or a mixed solution of ethylene glycol and high-purity water as solution a.

[0012] (2) Dissolve a certain amount of chloroauric acid in the above solution a, wherein the mass concentration of chloroauric acid is 2.5 to 25 g / L, to obtain solution b.

[0013] (3) A certain amount of disodium ethylenediaminetetraacetate is dissolved in the above solution b under stirring, wherein the mass concentration of disodium ethylenediaminetetraacetate is 2.5 to 25 g / L, to obtain solution c.

[0014] (4) Dissolving a certain amount of polyvinyl pyrrolidone in the above solution c under stirring, wherein the mass concentration of polyvinyl pyrrolidone is 2.5 to 25 g / L, to obtain solution d.

[0015] (5) dissolving one or more reducing agents selected from citric acid, sodium citrate, vitamin C, and sodium borohydride in the above solution d under stirring, wherein the total mass concentration of the reducing agent is 2.5 to 25 g / L, to obtain solution e.

[0016] (6) 1 M sodium hydroxide is added to the above solution e under stirring, wherein the volume of the added sodium hydroxide solution is 0.3 to 2.1 ml, to obtain solution f.

[0017] (7) Solution f was transferred into a polytetrafluoroethylene liner, the reactor was tightened, and then a hydrothermal reaction was carried out at 140-250 °C for 12-148 h to prepare gold powders of different morphologies and sizes in one step.

[0018] (8) Washing, separating and drying the gold powder obtained in step (7) to obtain gold powders of different shapes and sizes.

[0019] Preferred:

[0020] The solution a in step (1) is a mixed solvent of high-purity water and ethylene glycol in a volume ratio of 1:1;

[0021] The mass concentration of chloroauric acid in the solution b in step (2) is 12.5 g / L;

[0022] The mass concentration of disodium ethylenediaminetetraacetate in solution c in step (3) is 7.5 g / L;

[0023] The mass concentration of polyvinyl pyrrolidone in the solution d in step (4) is 7.5 g / L;

[0024] The total mass concentration of the reducing agent in the solution e in step (5) is 2.5 g / L;

[0025] The volume of 1M sodium hydroxide in the solution f in step (6) is 1.5 ml;

[0026] The temperature of the hydrothermal reaction in step (7) is 140° C. and the reaction time is 24 h;

[0027] In the steps (3), (4), (5) and (6), the stirring speed is 300 rpm and the stirring time is 20 min respectively.

[0028] The drying in step (8) is freeze drying, and the drying time is 12 hours.

[0029] Compared with the prior art, the present invention has the following technical advantages:

[0030] (1) About 95% of the gold powder prepared under the optimized conditions of the present invention is spherical particles with a diameter ranging from 500 nanometers to 1 micrometer; about 5% is in the form of nanorods and micro-nanosheets, wherein the nanorods have a diameter of about 300 nanometers and a length of about 2 to 10 micrometers; the nanosheets have a diameter of about 500 nanometers to 3 micrometers and a thickness of 300 nanometers to 1 micrometer.

[0031] (2) The method of the present invention can achieve simple and effective control of the morphology and size of gold powder by regulating the type and addition amount of reactants and reaction conditions.

[0032] (3) In the present invention, disodium ethylenediaminetetraacetic acid is used as a complexing agent, polyvinyl pyrrolidone (average molecular weight of 10,000 to 58,000) is used as a surfactant, high-purity water and ethylene glycol are used as reaction solvents, one or more substances selected from citric acid, sodium citrate, vitamin C, and sodium borohydride are used as reducing agents, and sodium hydroxide is used as a pH regulator. Gold powders of different morphologies and sizes are prepared in one step by a hydrothermal reaction at 140 to 220° C. for 12 to 148 hours. The prepared gold powder can be used in the fields of semiconductor packaging, integrated circuits, and high-reliability military electronic pastes.

[0033] (4) The advantages of the present invention are that the prepared gold powder is composed of nanorods, spherical particles and flakes. The diameter of the spherical particles is about 500 nanometers to 1 micron, and the contact between the particles is more dense. At the same time, the mixed nanorods and micro-nano flakes can increase the effective contact between the particles, which will help improve the conductivity of the film after calcination.

[0034] (5) The preparation method of the present invention is simple, does not require high-cost equipment, and the product batch morphology is stable, which is conducive to the large-scale and low-cost preparation of gold powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is an electron microscope scanning image of the nanorods, spherical particles and flaky gold powder in Example 1;

[0036] Figure 2 This is an electron microscope scanning image of the agglomerated nanoparticle gold of Comparative Example 2;

[0037] Figure 3 This is an electron microscope scanning image of the agglomerated nanoparticles and micron-sized flake gold of Comparative Example 3;

[0038] Figure 4 This is an electron microscope scanning image of the agglomerated micro-nano particle gold of Comparative Example 4;

[0039] Figure 5 This is an electron microscope scanning image of dispersed nanoparticle gold in Comparative Example 5;

[0040] Figure 6 This is an electron microscope scanning image of dispersed nanoparticles and nanorod-shaped gold in Comparative Example 6;

[0041] Figure 7 This is an electron microscope scanning image of bulk micron gold of comparative example 7;

[0042] Figure 8 This is an electron microscope scanning image of the dispersed micro-nano particle gold in Comparative Example 8. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. On the contrary, the present invention encompasses any substitutions, modifications, equivalent methods and schemes made on the essence and scope of the present invention as defined by the claims. Further, in order to enable the public to have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. For those skilled in the art, the present invention can be fully understood without the description of these details.

[0044] The present invention provides a method for preparing gold powder in which nanorods, micro-nano spherical particles and flakes coexist, comprising the following steps:

[0045] (1) Take a certain amount of ethylene glycol, high-purity water, or a mixed solution of ethylene glycol and high-purity water (volume ratio of 1:1) as solution a.

[0046] (2) Dissolve a certain amount of chloroauric acid in the above solution a, wherein the mass concentration of chloroauric acid is 2.5 to 25 g / L, to obtain solution b.

[0047] (3) A certain amount of disodium ethylenediaminetetraacetate is dissolved in the above solution b under stirring, wherein the mass concentration of disodium ethylenediaminetetraacetate is 2.5 to 25 g / L, to obtain solution c.

[0048] (4) Dissolving a certain amount of polyvinyl pyrrolidone in the above solution c under stirring, wherein the mass concentration of polyvinyl pyrrolidone is 2.5 to 25 g / L, to obtain solution d.

[0049] (5) dissolving one or more reducing agents selected from citric acid, sodium citrate, vitamin C, and sodium borohydride in the above solution d under stirring, wherein the total mass concentration of the reducing agent is 2.5 to 25 g / L, to obtain solution e.

[0050] (6) 1 M sodium hydroxide is added to the above solution e under stirring, wherein the volume of the added sodium hydroxide solution is 0.3 to 2.1 ml, to obtain solution f.

[0051] (7) Solution f was transferred into a polytetrafluoroethylene liner, the reactor was tightened, and then a hydrothermal reaction was carried out at 140-250 °C for 12-148 h to prepare gold powders of different morphologies and sizes in one step.

[0052] (8) Washing, separating and drying the gold powder obtained in step (7) to obtain gold powders of different shapes and sizes.

[0053] The technical solutions and beneficial effects of the present invention are further described below in conjunction with specific embodiments.

[0054] Example 1, the preparation steps are as follows:

[0055] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0056] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring to obtain solution b for later use;

[0057] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0058] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0059] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0060] (6) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0061] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the above Teflon reaction liner with a steel jacket, and then put the entire set of reactors into a forced air drying oven and heat at 140° C. for 24 h to obtain a gold powder stock solution;

[0062] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain the gold powder containing the coexistence of nanorods, micro-nano spherical particles and flakes.

[0063] The gold powder prepared in this embodiment is composed of nanorods, spherical particles and flake gold. The diameter of the nanorods is about 300 nanometers and the length is 2 to 10 micrometers; the diameter of the spherical nanoparticles is about 500 nanometers to 1 micrometer; the diameter of the micro-nano flakes is about 500 nanometers to 3 micrometers and the thickness is 300 nanometers to 1 micrometer (e.g. Figure 1 As shown), it can better meet the use requirements of gold electronic paste.

[0064] Comparative Example 2, the preparation steps are as follows:

[0065] (1) Record 20 ml of ethylene glycol as solvent a and set aside;

[0066] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0067] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0068] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0069] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0070] (6) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0071] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the above Teflon reaction liner with a steel jacket, and then put the entire set of reactors into a forced air drying oven and heat at 140° C. for 24 h to obtain a gold powder stock solution;

[0072] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder composed of agglomerated nanoparticles, wherein the diameter of the nanoparticles is about 100 nanometers, such as Figure 2 shown.

[0073] Comparative Example 3, the preparation steps are as follows:

[0074] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0075] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0076] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0077] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0078] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0079] (6) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0080] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the Teflon reaction liner with a steel jacket, and then place the entire reactor in a forced air drying oven and heat it at 200° C. for 24 h to obtain a gold powder stock solution;

[0081] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder composed of agglomerated particles with a diameter of about 50 nanometers and a small amount of flaky structures with a size of 1 to 10 micrometers, such as Figure 3 shown.

[0082] Comparative Example 4, the preparation steps are as follows:

[0083] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0084] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0085] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0086] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0087] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0088] (6) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0089] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the above Teflon reaction liner with a steel jacket, and then put the entire set of reactors into a forced air drying oven and heat at 250° C. for 24 h to obtain a gold powder stock solution;

[0090] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder composed of partially agglomerated spherical particles with a diameter of about 500 nanometers to 5 micrometers, such as Figure 4 shown.

[0091] Comparative Example 5, the preparation steps are as follows:

[0092] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0093] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0094] (3) adding 0.15 g of disodium ethylenediaminetetraacetate to the above solution b under stirring at 300 rpm to obtain solution c, which is set aside;

[0095] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0096] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0097] (6) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0098] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the above Teflon reaction liner with a steel jacket, and then put the entire reactor into a forced air drying oven and heat it at 160° C. for 24 h to obtain a gold powder stock solution;

[0099] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder composed of relatively dispersed spherical particles with a diameter of about 30 to 120 nanometers, such as Figure 5 shown.

[0100] Comparative Example 6, the preparation steps are as follows:

[0101] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0102] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0103] (3) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution b under stirring at 300 rpm and stirring for 20 min to obtain solution c for later use;

[0104] (4) adding 0.25 g of sodium citrate to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0105] (5) 1.5 ml of 1 M sodium hydroxide was added dropwise to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e;

[0106] (6) Transfer the above solution e into a Teflon reaction liner with a volume of 25 ml, tighten the Teflon reaction liner with a steel jacket, and then place the entire reactor into a forced air drying oven and heat it at 140° C. for 24 h to obtain a gold powder stock solution;

[0107] (7) The gold powder stock solution obtained in step (6) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder mainly composed of relatively dispersed spherical particles with a diameter of about 50 to 250 nanometers and a small number of nanorods with a diameter of about 50 nanometers and a length of about 3 micrometers, such as Figure 6 shown.

[0108] Comparative Example 7, the preparation steps are as follows:

[0109] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0110] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0111] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0112] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0113] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0114] (6) Transfer the above solution e into a Teflon reaction liner with a volume of 25 ml, tighten the Teflon reaction liner with a steel jacket, and then place the entire reactor into a forced air drying oven and heat it at 140° C. for 24 h to obtain a gold powder stock solution;

[0115] (7) The gold powder stock solution obtained in step (6) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder consisting of block particles with a diameter of about 50 to 200 microns, such as Figure 7 shown.

[0116] Comparative Example 8, the preparation steps are as follows:

[0117] (1) 10 ml of high-purity water and 10 ml of ethylene glycol were mixed to prepare solvent a for later use;

[0118] (2) adding 0.25 g of chloroauric acid to the above solvent a under stirring at 300 rpm and stirring for 20 min to obtain solution b for later use;

[0119] (3) 0.15 g of disodium ethylenediaminetetraacetate was added to the above solution b under stirring at 300 rpm and stirred for 20 min to obtain solution c, which was set aside;

[0120] (4) adding 0.15 g of polyvinyl pyrrolidone (average molecular weight 40,000) to the above solution c under stirring at 300 rpm and stirring for 20 min to obtain solution d for later use;

[0121] (5) 0.25 g of sodium citrate was added to the above solution d under stirring at 300 rpm and stirred for 20 min to obtain solution e, which was set aside;

[0122] (6) 2.1 ml of 1 M sodium hydroxide was added dropwise to the above solution e under stirring at 300 rpm and stirred for 20 min to obtain solution f;

[0123] (7) Transfer the above solution f into a Teflon reaction liner with a volume of 25 ml, tighten the above Teflon reaction liner with a steel jacket, and then put the entire set of reactors into a forced air drying oven and heat at 140° C. for 24 h to obtain a gold powder stock solution;

[0124] (8) The gold powder stock solution obtained in step (7) is washed and separated with deionized water, and the obtained gold powder precipitate is freeze-dried for 12 hours to obtain gold powder consisting of relatively dispersed spherical particles with a diameter of about 200 nanometers to 1 micron, such as Figure 8 shown.

Claims

1. A method for preparing nanorods, micro-nano particles and flaky mixed gold powder, comprising the following steps: (1) taking a certain amount of ethylene glycol, high-purity water, or a mixed solution of ethylene glycol and high-purity water as solution a; (2) dissolving a certain amount of chloroauric acid in the above solution a, wherein the mass concentration of chloroauric acid is 2.5 to 25 g / L, to obtain solution b; (3) dissolving a certain amount of disodium ethylenediaminetetraacetate in the above solution b under stirring, wherein the mass concentration of disodium ethylenediaminetetraacetate is 2.5 to 25 g / L, to obtain solution c; (4) dissolving a certain amount of polyvinyl pyrrolidone in the above solution c under stirring conditions, wherein the mass concentration of polyvinyl pyrrolidone is 2.5 to 25 g / L, to obtain solution d; (5) dissolving one or more reducing agents selected from citric acid, sodium citrate, vitamin C, and sodium borohydride in the above solution d under stirring, wherein the total mass concentration of the reducing agent is 2.5 to 25 g / L, to obtain solution e; (6) adding 1 M sodium hydroxide to the above solution e under stirring, wherein the volume of the added sodium hydroxide solution is 0.3 to 2.1 ml, to obtain solution f; (7) transferring solution f into a polytetrafluoroethylene liner, tightening the reactor, and then hydrothermally reacting at 140-250° C. for 12-148 h to prepare gold powders of different morphologies and sizes in one step; (8) Washing, separating and drying the gold powder obtained in step (7) to obtain gold powders of different shapes and sizes.

2. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The solution a in step (1) is a mixed solvent of high-purity water and ethylene glycol in a volume ratio of 1:

1.

3. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The mass concentration of chloroauric acid in the solution b in step (2) is 12.5 g / L.

4. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The mass concentration of disodium ethylenediaminetetraacetate in solution c in step (3) is 7.5 g / L.

5. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The mass concentration of polyvinyl pyrrolidone in the solution d in step (4) is 7.5 g / L.

6. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The total mass concentration of the reducing agent in the solution e in step (5) is 2.5 g / L.

7. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The volume of 1M sodium hydroxide in the solution f in step (6) is 1.5 ml.

8. The method for preparing nanorods, micro-nano particles and flaky mixed gold powder according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (7) is 140° C. and the reaction time is 24 h.

9. A nanorod, micro-nano particle and flaky mixed gold powder prepared according to the method according to any one of claims 1 to 8.

10. An application of the nanorods, micro-nano particles and flaky mixed gold powder according to claim 9, characterized in that: It is used in fields including semiconductor packaging, integrated circuits and high-reliability military electronic pastes.

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