Metal particle, and its preparation method and use

Abstract

To provide a metal particle having pores distributed at its center, high sphericity, a low shrinkage rate, and small crystal grains inside the particle, and its use.SOLUTION: A metal particle is provided in which pores are distributed at the internal center. The distribution pattern of these pores at the center of the metal particle is one of the following: (a) a plurality of pores uniformly distributed at the center of the metal particle; (b) a plurality of pores concentrated at the center of the metal particle; (c) a plurality of pores dispersed and distributed at the center of the metal particle; and (d) annular pores surrounding the center of the metal particle. The sphericity of the metal particle ranges from 0.6 to 1. It is preferred that the metal is at least one kind of gold, silver, copper, and nickel.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to the technical field of metallic materials, in particular to metallic particles, their preparation method and use. [Background technology]

[0002] Compositions containing fine metal particles or dispersions thereof are useful in fields such as wiring formation in flat panel displays (FPDs), solar cells, and radio frequency identification technology (RFID), embedded wiring in fine channels and vias, colorants for car and ship painting, biochemical adsorption carriers in the fields of medicine, diagnosis, and biotechnology, catalysts, flexible printed circuits, and capacitors. With the current and future development of the optoelectronics industry, electronic elements are becoming smaller and more powerful, which places higher demands on performance indicators such as sphericity, dispersibility, and particle size of fine metal nanoparticles.

[0003] In the prior art, methods for preparing metal particles include physical methods and chemical methods, of which physical methods include atomization, vapor phase evaporation, grinding, etc., while chemical methods mainly include sol-gel methods, liquid phase reduction methods, physical vapor deposition (PVD), hydrothermal methods, chemical vapor deposition (CVD), precipitation, plasma methods, etc. Because physical methods have problems such as high cost and low yield, chemical liquid phase reduction methods, i.e., methods in which a salt solution or oxide containing a metal is reduced to the metal through a chemical reaction, are currently widely used, such as the method for preparing metal particles in Patent Document 1: Chinese Patent CN104128616A.

[0004] However, while the metal particles currently required for production are generally spherical, the proportion of particles of the desired shape in the total number of particles in the sample is very small. Metal particles also contain many particles of other shapes, such as sheet, hexagonal, triangular, and cubic shapes, which present many problems. In addition, there are samples with large particle sizes and a wide size distribution, limiting their application in the microelectronics field.

[0005] Prior art patent document 2: Chinese patent CN105436517B discloses a preparation method for inducing the production of metal powder using nano-seed crystals, but even when metal seed crystals are added, the metal powder has a large surface roughness and irregularity, resulting in a polygonal shape with sharp corners. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] China patent CN104128616A [Patent Document 2] China patent CN105436517B Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to overcome the drawbacks of the prior art and provide metal particles, a method for producing the same and applications thereof. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention employs the following technical means.

[0009] In a first aspect, the present invention provides a method for producing a composition comprising: Metal particles, Pores are distributed at the center of the interior of the metal particle, and the distribution pattern of the pores at the center of the interior of the metal particle is as follows: Form a: a plurality of pores uniformly distributed in the center of the metal particle; Form b: a plurality of pores distributed in a concentrated manner at the center of the metal particle; Form c, in which a plurality of pores are dispersedly distributed in the center of the metal particle; and Provided are metal particles that are one of form d, which are annular pores surrounding the center of the metal particle.

[0010] In a preferred embodiment of the method for preparing metal particles of the present invention, the pores have at least one of the following pore sizes: Type a: The pores uniformly distributed in the center of the metal particles have a diameter of 0.1 nm to 50 nm, preferably 5 nm to 50 nm, and more preferably 9 nm to 30 nm; Type b: The pores concentrated at the center of the metal particles have a diameter of 0.1 nm to 80 nm, preferably 2 nm to 80 nm, and more preferably 2.5 nm to 60 nm; Type c: The pores dispersed in the center of the metal particles have a diameter of 1 nm to 60 nm, preferably 10 nm to 60 nm, and more preferably 14 nm to 45 nm; Type d: The diameter of the annular pore is half or less of the diameter of the metal particle, preferably the pore diameter is 0.1 μm to 1 μm, and more preferably the pore diameter is 0.2 μm to 0.5 μm.

[0011] In a preferred embodiment of the metal particles of the present invention, the metal is at least one of gold, silver, copper, and nickel. In a preferred embodiment of the metal particles of the present invention, the crystal grain size of the metal particles is 10 nm to 80 nm, and the sphericity of the metal particles is 0.6 to 1, preferably 0.8 to 0.95.

[0012] In a second aspect, the present invention provides a method for producing a pharmaceutical composition comprising: Step (1) of dispersing spherical or nearly spherical nanometal seed crystals in a polyol mixture to prepare a polyol-seed crystal system; Step (2) adding the polyol-seed crystal system to a dispersion, then adding an oxidizing solution and a reducing solution containing a metal oxide or metal salt containing a metal source in the seed crystals, and stirring to react; and (3) adding a flocculant, precipitating and separating to obtain metal particles.

[0013] The present invention employs a polyol-seed crystal system in which spherical or nearly spherical nanometal particles are used as seed crystals and the spherical or nearly spherical nanometal seed crystals are dispersed in a polyol, i.e., the seed crystals are coated with a polyol and then dispersed. After the polyol-seed crystal system is added to the dispersion, alcohol-water substitution occurs, forming a uniform nanobubble coating layer consisting of spherical and / or elliptical nanobubbles on the surface of the seed crystals. When an oxidizing solution and a reducing solution are added and reacted, the seed crystals induce reduction and precipitation of crystal grains on the surface, compressing the nanobubbles and causing them to burst, generating extremely strong shock waves that cause lattice rupture and form cavities during the growth of the metal crystals. Since the seed crystals vary in size, the coated nanobubbles also vary in size and number, and therefore cavities of different sizes and shapes are formed in the central region of the metal crystals during growth. The proportion of metal particles with different types of cavities is related to the particle size distribution of the spherical nanometal seed crystals.

[0014] Furthermore, in the present invention, by using spherical or nearly spherical nano-metal particles as seed crystals for crystallization, fine crystal grains are formed surrounding the seed crystals. During the process of inducing crystal grain growth, the two-dimensional effect of the resulting crystal interface becomes more uniform, resulting in the formation of smaller crystal grains and metal particles with higher sphericality. The spherical or nearly spherical seed crystals have uniform grain boundary bonding strength, which rapidly accelerates the reaction, promoting the cavitation effect formed during the reaction and forming holes in the central regions of the metal particles during the reaction, resulting in a more uniform and increased shrinkage rate of the metal particle crystal grains. Furthermore, the polyol-seed crystal system of the present invention promotes the generation of bubbles during the reaction, and the affinity between the polyol and the dispersion liquid as homogeneous solvents further promotes the dispersion of the seed crystals. The dispersion liquid disperses the generated metal particles and prevents their aggregation during the reaction.

[0015] In a preferred embodiment of the method for preparing metal particles of the present invention, the metal is at least one of gold, silver, copper, and nickel.

[0016] In a preferred embodiment of the metal particle preparation method of the present invention, in step (1), the particle diameter of the seed crystal is 1 nm to 100 nm. Preferably, the particle diameter of the seed crystal is 1 nm to 70 nm. More preferably, the particle diameter of the seed crystal is 5 nm to 40 nm.

[0017] When seed crystals of such particle size are used, many air valves are present in the reaction solution, causing a cavitation effect during the crystallization process of the metal particles in the reaction, resulting in the formation of pores inside the metal particles.Furthermore, as the particle size of the seed crystals increases within a limited range due to the cavitation effect during the reaction process, larger air valves are formed inside the metal particles due to the air valves in the reaction solution, resulting in the formation of pores.

[0018] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (1), the polyol accounts for 15 to 95% by volume of the polyol mixture. Preferably, the polyol accounts for 50 to 85% by volume, with the remainder being at least one dispersant and / or surfactant selected from esters, ethers, ketones, ether esters, hydrocarbons, amines, and pyrrolidones, preferably at least one selected from polyvinylpyrrolidone, octylamine, and Twain.

[0019] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (1), the polyol is at least one of pentaerythritol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, and glycerin.

[0020] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the stirring speed is 5 rpm to 1000 rpm, preferably 50 rpm to 500 rpm.

[0021] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the content of the metal seed crystals is 0.0001% by mass to 0.01% by mass of the metal in the oxidizing solution, and preferably, the content of the metal seed crystals is 0.0002% by mass to 0.001% by mass of the metal in the oxidizing solution.

[0022] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the reaction temperature is 10 to 90°C. Preferably, the reaction temperature is 20 to 40°C.

[0023] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the pH value of the oxidizing solution is 2.5 to 8.5, preferably 5 to 7.5.

[0024] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the reducing solution contains at least one reducing agent selected from the group consisting of hydrazines, amines, organic acids, alcohols, aldehydes, hydrides, transition metal salts, pyrrolidones, and hydroxylamines.

[0025] Preferably, the hydrazines are at least one of hydrazine, hydrazine hydrate, phenylhydrazine, and hydrazine sulfate; the amines are at least one of dimethylaminoethanol, triethylamine, octylamine, and dimethylaminoborane; the organic acids are at least one of citrate, ascorbic acid and its salts, tartrate, gallic acid and its salts, malate, malonic acid and its salts, and formic acid; the alcohols are at least one of methanol, ethanol, isopropanol, ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; and the hydrides are , sodium borohydride, lithium borohydride, lithium triethylborohydride, lithium aluminum hydride, diisobutylaluminum hydride, tributyltin hydride, lithium tri-sec-butylborohydride, potassium tri-sec-butylborohydride, zinc borohydride, and sodium acetoxyborohydride; the transition metal salts are iron sulfate and / or tin sulfate; the pyrrolidones are at least one of polyvinylpyrrolidone, 1-vinylpyrrolidone, N-vinylpyrrolidone, and methylpyrrolidone; and the hydroxylamine is hydroxylamine sulfate and / or hydroxylamine nitrate.

[0026] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the amount of the reducing agent added is 0.1 to 7 equivalents, preferably 1 to 5 equivalents, based on the metal mass in the oxidizing solution.

[0027] If the amount of the reducing agent added is less than 0.1, there is a risk that unreduced metal will remain, and if it exceeds 7, the reaction will be too fast, increasing the number of agglomerated particles and resulting in non-uniform particle sizes.

[0028] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the amount of the dispersant added is 0.1 to 5 times the mass of the metal oxide or metal salt in the oxidizing liquid.

[0029] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (2), the dispersion liquid contains at least one dispersant and / or surfactant selected from the group consisting of organic acids, esters, ethers, ketones, ether esters, alcohols, hydrocarbons, amines, and pyrrolidones.

[0030] Preferably, the dispersant is at least one of fatty acid salts, α-sulfofatty acid ester salts, alkylbenzenesulfonates, linear alkylbenzenesulfonates, alkyl sulfates, alkyl ether sulfate ester salts, alkyl triethanol sulfates, fatty acid ethanolamides, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, sorbitol, sorbitan, alkyltrimethylammonium salts, dialkyldimethylammonium chloride, alkylpyridine chloride, alkylcarboxybetaine, sulfobetaine, lecithin, formaldehyde condensates of naphthalenesulfonates, polystyrene sulfonates, polyacrylates, copolymer salts of vinyl compounds and carboxylic acid monomers, carboxymethylcellulose, polyvinyl alcohol, polyacrylic acid partial alkyl esters and / or polyalkylenepolyamines, polyethyleneimine and / or aminoalkylmethacrylate copolymers, polyvinylpyrrolidone, 1-vinylpyrrolidone, N-vinylpyrrolidone, and methylpyrrolidone.

[0031] The dispersing agent is at least one of polyvinylpyrrolidone, octylamine, ethanol, polyethylene glycol, Twain, glycerol, and maleic acid.

[0032] In a preferred embodiment of the method for preparing the metal particles of the present invention, in step (2), the oxidizing liquid and / or reducing liquid may be added to the dispersion liquid by pressure transfer using a pump, pressure transfer using compressed air, or injection, and the addition flow rate of the oxidizing liquid and / or reducing liquid is 1 mL / min to 1500 L / min, and the stirring speed is 50 rpm to 500 rpm.

[0033] Compared to conventional technology, the range of flow rates is significantly wider, the stirring reaction speed is faster, the reaction conditions are wider, production volume is increased, and mass production is possible.

[0034] In a preferred embodiment of the method for preparing metal particles of the present invention, in step (3), the aggregating agent is a fatty acid and / or a carboxylic acid compound.

[0035] Preferably, the fatty acids are at least one saturated fatty acid selected from the group consisting of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid, or At least one unsaturated fatty acid selected from oleic acid, linoleic acid, linolenic acid, and arachidonic acid, and salts thereof; The carboxylic acid compound is at least one of a compound having a carbon-carbon double bond (such as sorbic acid), a dihydroxy compound (such as adipic acid), and a dicarboxy compound.

[0036] After the reaction, a flocculant is added to agglomerate the nanoparticles, changing the charge potential (ζ-potential) of the particles and their bonding surfaces. The particles are then precipitated and separated to obtain metal nanoparticles.

[0037] In a third aspect, the present invention is the use of metal particles as described above in a conductive adhesive for solar cells and / or semiconductors. [Effects of the Invention]

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The metal particles of the present invention have high sphericity, pores distributed in the center of the particles, a high shrinkage ratio, and small crystal grains (10 nm to 80 nm) inside the particles, making them suitable for use in HJT (heterojunction battery) silver pastes and in fields such as perc SP and stepwise printing. For example, when metal particles with a high shrinkage ratio are used in screen printing of solar cell panels, the line width narrows when the electrodes on the surface of the solar cell panel are sintered at high temperatures, improving conversion efficiency by 0.05% to 0.1%.

[0039] The method for preparing metal particles of the present invention involves introducing spherical or nearly spherical metal seed crystals to prepare a polyol-seed crystal system, thereby enabling control of the particle size and sphericity of the metal particles during the reduction process, and quickly and stably reducing metal particles in a metal oxide or metal salt solution containing a metal source in the seed crystals, ensuring that the morphology of the formed metal particles is spherical or nearly spherical, and the particle size of the metal particles is adjusted by the number and size of the spherical nanometal seed crystals introduced. [Brief explanation of the drawings]

[0040] [Figure 1] 1 is an electron microscope image (200K×) of spherical silver seed crystals used in the examples. [Figure 2] 1 is an electron microscope image (40K×) of spherical silver seed crystals used in the examples. [Figure 3] 1 is an electron microscope image (20K×) of silver particles prepared in Example 1. [Figure 4] 1 is an electron microscope image (30K×) of silver particles prepared in Example 1. [Figure 5] 1 is an XRD detection chart of the silver particles prepared in Example 1. [Figure 6] 1 is an electron microscope image (10K×) of silver particles prepared in Example 2. [Figure 7] 1 is an electron microscope image of cross-cut silver particles prepared in Example 2. [Figure 8] 1 is an electron microscope image (10K×) of silver particles prepared in Example 3. [Figure 9] 1 is an electron microscope image of cross-cut silver particles prepared in Example 3. [Figure 10] 1 is an electron microscope image (10K×) of silver particles prepared in Example 4. [Figure 11] 1 is an electron microscope image of cross-cut silver particles prepared in Example 4. [Figure 12] 1 is an electron microscope image (20K×) of silver particles prepared in Example 5. [Figure 13]1 is an electron microscope image of cross-cut silver particles prepared in Example 5. [Figure 14] 1 shows TMA detection charts of silver particles prepared in Examples 1 to 5, where a is the detection curve for silver particles prepared in Example 1, b is the detection curve for silver particles prepared in Example 3, c is the detection curve for silver particles prepared in Example 4, d is the detection curve for silver particles prepared in Example 2, and e is the detection curve for silver particles prepared in Example 5. [Figure 15] 1 is an electron microscope image (150K×) of the copper seed crystal used in Example 6. [Figure 16] 1 is an electron microscope image (100K×) of the gold seed crystal used in Example 8. [Figure 17] 1 is an electron microscope image of silver seed crystals used in Comparative Examples 1 and 2. [Figure 18] 1 is an electron microscope image (10K×) of silver particles prepared in Comparative Example 1. [Figure 19] 1 is a TMA detection chart of silver particles prepared in Comparative Example 1. [Figure 20] 1 is an electron microscope image (10K×) of silver particles prepared in Comparative Example 2. [Figure 21] 1 is an XRD detection chart of silver particles prepared in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0041] In order to better explain the objectives, technical means and advantages of the present invention, the present invention will be further described below with reference to specific examples. Those skilled in the art should understand that the specific examples described herein are only used to illustrate the present invention, and do not limit the present invention. Unless otherwise specified, all test methods used in the examples are conventional methods. Materials, reagents, etc. used are commercially available unless otherwise specified. The metal particles are also simply called "particles," are generally handled in powder form, and are also called "metal particle powder" or simply "powder." The D50 is the particle size when the cumulative particle size distribution rate of one sample reaches 50%. Example 1 (1) Preparation of oxidizing solution 100 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 250 mL of deionized water, the pH was adjusted to 5, and the solution was kept at 20°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 50 g of vitamin C to 250 mL of deionized water, and the solution was kept at 20°C. (3) Preparation of dispersion 20 g of PVP was added to 300 mL of deionized water and dissolved to prepare a dispersion, which was then thoroughly stirred and kept at 20°C. (4) Preparation of polyol-seed crystal system Spherical nanosilver seed crystals were dispersed in 80% by volume of glycerin (the remainder being PVP). The particle size of the spherical nanosilver seed crystals was 5 to 40 nm, and the mass of the spherical nanosilver seed crystals was 0.001% of the mass of silver in the silver nitrate-containing solution. The solution was kept at 20°C, and the seed crystals were magnified with an electron microscope as shown in Figure 1 (200Kx) and Figure 2 (40Kx). (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was then added to the reactor. The oxidizing solution and reducing solution were then sent to the reactor simultaneously (flow rate: 38 mL / min). The reduction reaction was carried out at a stirring speed of 50 rpm. After the reaction was completed, 0.031 g of stearic acid was added as a flocculant, which precipitated and separated the mixture to obtain silver particle powder. As shown in Figure 3, when the silver particles were observed under an electron microscope at 20Kx magnification, the resulting silver particles had a high sphericity. As shown in Figure 4, when the silver particles were observed under an electron microscope at 30Kx magnification, the silver particles had a D50 of approximately 400 nm and a high sphericity. Calculations based on the principles of the GB / T37406-2019 method revealed that the average sphericity was 0.89. The obtained silver particle sample was detected by XRD (X-ray diffraction analyzer model: Shimadzu XRD-6100, Japan). As shown in Figure 5, the measured value was 20561, and the peak value was high. This indicated that the obtained silver particles had a consistent crystal shape and a sharp peak, indicating that the particle size of the obtained silver particles was uniform and the distribution was concentrated. Example 2

[0042] (1) Preparation of oxidizing solution 100 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 250 mL of deionized water, the pH was adjusted to 6.5, and the solution was kept at 30°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 20 g of hydrazine hydrate to 250 mL of deionized water, and the solution was kept at 30°C. (3) Preparation of dispersion 20 g of octylamine was added to 300 mL of deionized water and dissolved to prepare a dispersion, which was then thoroughly stirred and kept at 30°C. (4) Preparation of polyol-seed crystal system Spherical nanosilver seed crystals were dispersed in 65% by volume of glycerin (the remainder was PVP). The particle size of the spherical nanosilver seed crystals was 5 to 40 nm, and the mass of the spherical nanosilver seed crystals was 0.0005% of the mass of silver in the silver nitrate-containing solution. The solution was kept at 30°C, and the seed crystals were magnified with an electron microscope as shown in Figure 1 (200Kx) and Figure 2 (40Kx). (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was then added to the reactor. The oxidizing solution and reducing solution were then sent to the reactor simultaneously (flow rate: 38 mL / min). The reduction reaction was carried out at a stirring speed of 50 rpm. After the reaction was completed, 0.05 g of oleic acid was added as a flocculant, which precipitated and separated the mixture to obtain silver particle powder. Observation of the silver particle sample under an electron microscope at 10Kx magnification revealed that the resulting silver particles had high sphericity and rounded edges, as shown in Figure 6. The sphericity was calculated according to the principles of GB / T37406-2019, yielding a value of 0.92. The size of the internal crystal grains was 10 to 80 nanometers. Compared to Example 1, the amount of added seed crystals was reduced, and the particle size of the resulting silver particles also increased, with a D50 of approximately 600 nm. We used a method to cut silver particles with gallium ions. We then observed the cross-sections of the resulting silver particles using an electron microscope. Three randomly selected silver particles were then examined. The samples were dispersed on a carbon paste and measured under ultra-high vacuum. As shown in Figure 7, the silver particles contained numerous pores, which were uniformly distributed in the center of the particles and ranged in size from 9 to 29 nm. The spherical or nearly spherical seed crystals possessed uniform grain boundary bonding strength, rapidly accelerating the catalytic reaction. This resulted in a cavitation effect during the reaction, leading to the formation of pores in the metal particles. Silver particles with numerous pores uniformly distributed in the center of the silver particles exhibited a high TMA metal contraction ratio, making them useful in many technical applications, such as HIT silver paste, perc SP, and stepwise printing. Example 3

[0043] (1) Preparation of oxidizing solution 100 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 250 mL of deionized water, the pH was adjusted to 6.8, and the solution was kept at 40°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 12 g of sodium borohydride to 200 mL of deionized water having a pH value of greater than 10, and the solution was kept at 40°C. (3) Preparation of dispersion A dispersion was prepared by adding 20 g of Twain to 300 mL of deionized water and dissolving it, followed by thorough stirring and keeping the solution at 30°C. (4) Preparation of polyol-seed crystal system Spherical silver nanocrystals were dispersed in 65% ethylene glycol (remainder: PVP) by volume. The particle size of the spherical silver nanocrystals was 10-40 nm, and the mass of the spherical silver nanocrystals was 0.00025% of the mass of silver in the silver nitrate solution. The solution was kept at 40°C, and the seed crystals were ACS1044 spherical silver nanocrystals. (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was then added to the reactor. The oxidizing solution and reducing solution were then sent to the reactor (flow rate: 38 mL / min). The reduction reaction was carried out at a stirring speed of 350 rpm. After the reaction was completed, 0.03 g of adipic acid was added as a flocculant, which precipitated and separated the mixture to obtain silver particle powder. The silver particle sample was observed under an electron microscope at 10Kx magnification, and as shown in Figure 8, the obtained silver particles had a high sphericity, which was calculated according to the principle of GB / T37406-2019 method to be 0.88. Compared with Example 2, the number of seed crystals added was reduced by half, and the particle size of the resulting silver particles increased, with D50 being approximately 1.2 μm. A method of cutting silver particles with gallium ions was used, and the cross sections of the resulting silver particles were observed under an electron microscope. Three silver particles were randomly selected and their cross sections were observed. The samples were dispersed on a carbon paste and measured under ultra-high vacuum. As shown in Figure 9, a small number of pores were present inside the silver particles, and the pores were concentrated and distributed at the center of the silver particles, with pore sizes ranging from 2.5 to 60 nm. The TMA metal contraction ratio of these silver particles was slightly higher than that of Example 2, but lower than that of silver particles with pores uniformly distributed at the center of the particles. Example 4

[0044] (1) Preparation of oxidizing solution 250 kg of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 650 L of deionized water, the pH was adjusted to 6.5, and the solution was kept at 20°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 150 kg of ascorbic acid to 250 L of deionized water, and the solution was kept at 20°C. (3) Preparation of dispersion 60 kg of polyethylene glycol was added to 700 L of deionized water and dissolved to prepare a dispersion, which was then thoroughly stirred and kept at 20°C. (4) Preparation of polyol-seed crystal system Spherical silver nanocrystals were dispersed in 50% by volume of 1,2-propylene glycol (the remainder being PVP). The particle size of the spherical silver nanocrystals was 10 to 40 nm, and the mass of the spherical silver nanocrystals was 0.0002% of the mass of silver in the silver nitrate solution. The solution was kept at 20°C, and the seed crystals were ACS1044 spherical silver nanocrystals. (5) Preparation of metal particles The dispersion liquid was sent to the reactor using a metering pump, and the polyol-seed crystal system was placed in the reactor. The oxidation liquid and reduction liquid were then sent to the reactor (flow rate: 40 L / min to 60 L / min). The reduction reaction was carried out at a stirring speed of 100 rpm to 200 rpm. After the reaction was completed, 0.08 kg of caprylic acid was added as a flocculant, which allowed precipitation and separation to obtain silver particle powder. The silver particle sample was observed under an electron microscope at 10K magnification, and the sphericity of the obtained silver particles was found to be high, as shown in Figure 10. The sphericity was calculated according to the principles of GB / T37406-2019 method to be 0.87. The D50 of the obtained silver particles was approximately 1.45 μm. We used a method to cut silver particles with gallium ions, and observed the cross sections of the obtained silver particles using an electron microscope. Three silver particles were randomly selected and their cross sections were observed. The samples were dispersed on a carbon paste and measured under ultra-high vacuum. As shown in Figure 11, a small number of large and fine pores were distributed inside the silver particles, and the pores were concentrated in the center of the silver particles, with the pore size ranging from 14 to 45 nm. Example 5

[0045] (1) Preparation of oxidizing solution 150 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 500 mL of deionized water, the pH was adjusted to 7.0, and the solution was kept at 40°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 85 g of gallic acid to 500 mL of deionized water, and the solution was kept at 40°C. (3) Preparation of dispersion A dispersion was prepared by adding 35 g of glycerol to 350 mL of deionized water and dissolving it, followed by thorough stirring and keeping the solution at 40°C. (4) Preparation of polyol-seed crystal system Spherical silver nanoseed crystals were dispersed in 65% by volume of ethylene glycol (the remainder being PVP). The particle size of the spherical silver nanoseed crystals was 5 to 50 nm, and the mass of the spherical silver nanoseed crystals was 0.0004% of the mass of silver in the silver nitrate-containing solution. The solution was kept at 40°C. (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was added to the reactor. The oxidizing solution and reducing solution were then added to the reactor, and the reduction reaction was carried out at a stirring speed of 150 rpm to 350 rpm. After the reaction was completed, 0.015 g of oleic acid was added as a flocculant, and the mixture was precipitated and separated to obtain silver particle powder. The silver particle sample was observed under an electron microscope at 20K magnification, and the sphericity of the resulting silver particles was found to be high, as shown in Figure 12. The sphericity was calculated according to the principles of GB / T37406-2019 method to be 0.86. The D50 of the resulting silver particles was approximately 800 nm. We used a method of cutting silver particles with gallium ions, and observed the cross sections of the resulting silver particles using an electron microscope. Three silver particles were randomly selected and their cross sections were observed. The samples were dispersed on a carbon paste and measured under ultra-high vacuum. As shown in Figure 13, a circular hole was found in the center of the silver particle, and the diameter of the hole was less than half the diameter of the metal particle. In this example, the diameter of the circular hole was 0.39 μm. Because there are many air valves in the reaction solution, a cavitation effect occurs during the crystallization process of the metal particles in the reaction process, forming pores inside the metal particles. Furthermore, as the particle size of the seed crystals increases due to the cavitation effect in the reaction process, larger air valves are formed inside the metal particles due to the air valves in the reaction solution. In this example, spherical nanosilver seed crystals with particle diameters of 5 nm to 50 nm were used, and during the reaction process, some of the small metal particles formed undergo a two-stage reaction on their surfaces, forming annular holes between the interface of the metal particles where the first-stage reaction has been completed and the crystal grains formed by the second-stage reaction. Test Example

[0046] The silver particle powders prepared in Examples 1 to 5 were pressed into silver sheets, and the sintering shrinkage was measured using a thermomechanical analyzer TMA (USA TA model: Q400). The results are shown in FIG. Figure 14 is a TMA detection chart of the silver particles prepared in Examples 1 to 5, where a is the detection curve for the silver particles prepared in Example 1, b is the detection curve for the silver particles prepared in Example 3, c is the detection curve for the silver particles prepared in Example 4, d is the detection curve for the silver particles prepared in Example 2, and e is the detection curve for the silver particles prepared in Example 5. From the above, it was found that the silver particles prepared in Examples 2 and 5 had a shrinkage rate of approximately 13.7%, and that in Example 5, a special structure such as a circular hole was formed in the central region of the particle, which improved the sintering activity of the powder and was advantageous for diversifying and improving the requirements for products with various formulations through fine line printing designs. The silver particles prepared in Example 1 have a shrinkage rate of approximately 9%, the silver particles prepared in Example 3 have a shrinkage rate of approximately 10%, and the silver particles prepared in Example 4 have a shrinkage rate of approximately 10.6%. Example 6

[0047] (1) Preparation of oxidizing solution 80 g of copper oxide was dissolved in 600 mL of ammonium chloride, the pH was adjusted to 7.2, and the solution was kept at 20°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 30 g of hydrazine hydrate to 600 mL of deionized water, and the solution was kept at 20°C. (3) Preparation of dispersion A dispersion was prepared by adding and dissolving 45 g of PVP in 500 mL of deionized water, and the solution was thoroughly stirred and kept at 20°C. (4) Preparation of polyol-seed crystal system Spherical nanocopper seed crystals were dispersed in 85% by volume of glycerin (the remainder being octylamine). The particle diameter of the spherical nanocopper seed crystals was 5 to 10 nm, and the mass of the spherical nanocopper seed crystals was 0.0005% of the mass of copper in the copper-containing solution. The solution was kept at 20°C, and the seed crystals were spherical nanocopper particles with a particle diameter of 5 nm, as shown in Figure 15. (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was then added to the reactor. The oxidizing solution and reducing solution were then sent to the reactor simultaneously (flow rate: 50 ml / min). The reduction reaction was carried out at a stirring speed of 200 rpm. After the reaction was completed, 0.03 g of caprylic acid was added as a flocculant, which precipitated and separated the mixture to obtain copper particle powder. Example 7

[0048] (1) Preparation of oxidizing solution 50 g of nickel sulfate was dissolved in 1600 mL of water, the pH was adjusted to 6.5, and the solution was kept at 35°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 60 g of hydroxylamine sulfate to 1300 mL of deionized water, and the solution was kept at 35°C. (3) Preparation of dispersion 50 g of sodium alkylbenzenesulfonate was added to and dissolved in 300 mL of deionized water to prepare a dispersion, which was then thoroughly stirred and kept at 35°C. (4) Preparation of polyol-seed crystal system Spherical nanonickel seed crystals are dispersed in 80% by volume of diethylene glycol (the remainder is octylamine), the particle diameter of the spherical nanonickel seed crystals is 5 nm to 20 nm, and the mass of the spherical nanonickel seed crystals is 0.0001% of the mass of nickel in the nickel-containing solution. The solution is kept at 35°C, and the seed crystals are spherical nanonickel particles. (5) Preparation of metal particles The dispersion was sent to the reactor using a metering pump, and the polyol-seed crystal system was placed in the reactor. The oxidation solution and reduction solution were then sent to the reactor (flow rate: 30 mL / min). The reduction reaction was carried out at a stirring speed of 500 rpm. After the reaction was completed, 0.095 g of linoleic acid was added as a flocculant, which precipitated and separated the mixture to obtain nickel particle powder. Example 8

[0049] (1) Preparation of oxidizing solution A 24 mmol / L HAuCl4 tetrachloroauric acid solution was prepared and kept at 110 to 130°C. (2) Preparation of reducing solution 15 ml of ethylene glycol was used as a reducing solution, and the solution was kept at 110 to 130°C. (3) Preparation of dispersion Polyvinylpyrrolidone and polyethylene glycol were used as a double dispersant system, and the mass ratio of PVP to PEG was 1:9 to 3:7. The solution was kept at 110 to 130°C. (4) Preparation of polyol-seed crystal system The spherical nanogold seed crystals were dispersed in 85% by volume of glycerin (the remainder was PVP). The particle diameter of the spherical nanogold seed crystals was 5 nm to 50 nm, and the mass of the spherical nanogold seed crystals was 0.0001% of the mass of gold in the tetrachloroauric acid-containing solution. The seed crystals are shown in Figure 16. (5) Preparation of metal particles The temperature of the oil bath was set to 110-130°C, the dispersion liquid was added to the reaction vessel, and then the polyol-seed crystal system was added while stirring. 15 ml of ethylene glycol was then added, and 10 ml of 24 mmol / L HAuCl4 oxidizing solution was added dropwise to the reaction vessel using a dropper. The reaction was allowed to proceed at a constant temperature, and the mixture was cooled to room temperature. 0.0003 g of a flocculant was added, and the mixture was precipitated and separated to obtain gold particle powder. Comparative Example 1

[0050] (1) Preparation of oxidizing solution 100 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 250 mL of deionized water, the pH was adjusted to 7.5, and the solution was kept at 30°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 50 g of vitamin C to 250 mL of deionized water, and the solution was kept at 29°C. (3) Preparation of dispersion A dispersion was prepared by dissolving 20 g of PVP in 250 mL of deionized water and thoroughly stirring. Regularly shaped silver nanoparticle seed crystals (40 nm to 50 nm) were added. The mass of the added nanosilver seed crystals was 0.001% of the mass of silver in the silver nitrate solution. The solution was kept at 30°C. As shown in Figure 17, the seed crystals were G5 nanosilver particles. (4) Preparation of metal particles The dispersion liquid was sent to the reaction vessel using a metering pump, and then the oxidizing liquid and reducing liquid were sent to the reaction vessel (flow rate: 50 mL / min). The reduction reaction was carried out at a stirring speed of 300 rpm. After the reaction was completed, 0.30 g of oleic acid was added as a flocculant, and the mixture was precipitated and separated to obtain silver particle powder. When the silver particles were observed under an electron microscope at 10Kx magnification, as shown in FIG. 18, the D50 of the obtained silver particles was 1.2 μm to 1.5 μm. The prepared silver particle powder was pressed into a silver sheet, and the sintering shrinkage was detected using a thermomechanical analyzer TMA (USA TA Model: Q400). Since the particles have a solid structure in the center and have little heat loss, the shrinkage ratio was 4.694%, as shown in Figure 19. Comparative Example 2

[0051] (1) Preparation of oxidizing solution 100 g of silver nitrate solid or an equivalent amount of silver nitrate liquid was dissolved in 250 mL of deionized water, the pH was adjusted to 7.0, and the solution was kept at 30°C. (2) Preparation of reducing solution A reducing solution was prepared by adding 50 g of vitamin C to 250 mL of deionized water, and the solution was kept at 30°C. (3) Preparation of dispersion A dispersion was prepared by dissolving 20 g of PVP in 300 mL of deionized water and thoroughly stirring. Irregularly shaped silver nanoparticle seed crystals (40 nm to 50 nm) were added. The mass of the added nanosilver seed crystals was 0.0005% of the mass of silver in the silver nitrate solution. The solution was kept at 30°C. As shown in Figure 17, the seed crystals were nanosilver seed crystal particles with poor sphericity, sharp edges, and irregular shapes. (4) Preparation of metal particles The dispersion liquid was sent to the reaction vessel using a metering pump, and then the oxidizing liquid and reducing liquid were sent to the reaction vessel (flow rate: 50 mL / min). The reduction reaction was carried out at a stirring speed of 300 rpm. After the reaction was completed, 0.033 g of linoleic acid was added as a flocculant, and the mixture was precipitated and separated to obtain silver particle powder. When the silver particle sample was observed under an electron microscope at 10Kx magnification, the obtained silver particles had a D50 of 2.0 μm to 2.5 μm, poor sphericity, sharp edges, and irregular shapes, as shown in Figure 20. Comparative Example 3

[0052] Patent Document 2: Silver particles were prepared using the method described in Chinese Patent CN105436517B. The prepared silver particles were subjected to XRD (X-ray diffraction analyzer model: Shimadzu XRD-6100, Japan). As shown in FIG. 21, the measured value was 15046, with a low peak value, indicating that the obtained silver particles did not have a consistent crystal form. Furthermore, the peak top was not sharp, indicating that the particle size of the obtained silver particles was non-uniform.

[0053] It should be noted that the above-described embodiments are merely used to explain the technical means of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art can modify or equivalently replace the technical means of the present invention without departing from the essence and scope of the technical means of the present invention.

Claims

1. Metal particles, Pores are distributed at the center of the interior of the metal particle, and the distribution pattern of the pores at the center of the interior of the metal particle is as follows: Form a: a plurality of pores uniformly distributed in the center of the metal particle; Form b: a plurality of pores distributed in a concentrated manner at the center of the metal particle; Form c) wherein the metal particles have a plurality of pores dispersedly distributed in the center; and a circular hole surrounding the center of the metal particle; The sphericity of the metal particles is 0.6 to 1. Metal particles characterized by:

2. The pore diameter of the pores is Type a, in which the pores uniformly distributed in the center of the metal particles have a diameter of 0.1 nm to 50 nm; Type b, in which the pores concentrated and distributed at the center of the metal particles have a pore diameter of 0.1 nm to 80 nm; Type c, in which the pores dispersed in the center of the metal particles have a pore diameter of 1 nm to 60 nm; and At least one of the types d in which the diameter of the annular hole is half or less of the diameter of the metal particle The metal particles according to claim 1 .

3. The metal is at least one of gold, silver, copper, and nickel. The metal particles according to claim 1 .

4. The crystal grain size of the metal particles is 10 nm to 80 nm. The metal particles according to claim 1 .

5. 5. Use of metal particles according to any one of claims 1 to 4 in conductive adhesives for solar cells and / or semiconductors.

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