Monodisperse silver-palladium alloy powder and preparation method thereof

Abstract

The invention provides monodisperse silver-palladium alloy powder and a preparation method thereof, and relates to the technical field of precious metal powder material preparation. Monodisperse silver-palladium alloy powder is prepared by adopting a liquid phase chemical reduction method, a specific type of metal salt solution and a reducing agent solution are added into a specific type of dispersing agent solution at the same time for an oxidation-reduction reaction, then through ball milling, the silver powder and the palladium powder can be fully mixed, and the silver-palladium alloy powder is prepared. The prepared monodisperse silver-palladium alloy powder is high in alloying degree, good in dispersity and nearly spherical. Experimental results show that the monodisperse silver-palladium alloy powder prepared by the preparation method provided by the invention is high in alloying degree and good in dispersity, and has nearly spherical morphology.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal powder material preparation, and specifically relates to a monodisperse silver-palladium alloy powder and a preparation method thereof. Background Art

[0002] Silver-palladium paste is a paste composed of silver-palladium alloy powder, inorganic additives (such as glass powder), and organic carriers (such as polymer matrix or organic solvent), and is mainly used for the preparation of conductive circuits and electrodes of electronic components. Silver-palladium alloy powder is one of the main raw materials of silver-palladium paste. The characteristics of silver-palladium alloy powder (such as alloying degree, particle morphology, particle size distribution, etc.) directly affect the performance of silver-palladium paste.

[0003] The application of silver-palladium alloy powder in electronic paste has high requirements on dispersibility and spherical properties. Good dispersibility and spherical properties help to improve the conductivity, sintering performance and stability of the paste. At present, the dispersibility of silver-palladium alloy powder has been well improved, but it still needs to be further optimized to meet the needs of high-end applications. Silver-palladium alloy powder that is close to spherical can be prepared through processes such as liquid phase reduction and chemical reduction. Due to the different reduction potentials of silver and palladium, the reduction potential of silver is more negative than that of palladium, which means that silver is more easily reduced during the chemical reduction process. This potential difference may cause silver to be reduced before palladium, forming an uneven alloy structure. Therefore, it is still difficult to obtain a monodisperse silver-palladium alloy powder with a high degree of alloying and a near-spherical shape. Summary of the invention

[0004] The object of the present invention is to provide a monodisperse silver-palladium alloy powder and a preparation method thereof. The preparation method provided by the present invention can prepare a monodisperse silver-palladium alloy powder with a high alloying degree and a nearly spherical shape.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing monodisperse silver-palladium alloy powder, comprising the following steps:

[0007] Adding a metal salt solution and a reducing agent solution to a dispersant solution at the same time to carry out an oxidation-reduction reaction to obtain a silver-palladium alloy powder; the metal salt in the metal salt solution is silver nitrate and palladium nitrate; the reducing agent in the reducing agent solution is ascorbic acid or ferrous sulfate; the dispersant in the dispersant solution is one or more of polyvinyl pyrrolidone, glycerol and polyethylene glycol 400;

[0008] The silver-palladium alloy powder is ball-milled to obtain monodisperse silver-palladium alloy powder.

[0009] Preferably, the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is (7-15):(0.5-3).

[0010] Preferably, the total concentration of metal salts in the metal salt solution is 10 to 17 g / L.

[0011] Preferably, the molar ratio of the reducing agent in the reducing agent solution to the metal salt in the metal salt solution is (2-5):1.

[0012] Preferably, the concentration of the reducing agent solution is 25-70 g / L.

[0013] Preferably, the mass ratio of the dispersant in the dispersant solution to the metal salt in the metal salt solution is (0.05-0.2):1.

[0014] Preferably, the concentration of the dispersant solution is 0.6-1.6 g / L.

[0015] Preferably, the redox reaction is carried out under stirring conditions, and the stirring speed is 500-1000 rpm.

[0016] Preferably, the ball-to-material ratio of the ball milling is (4-7):1, the ball milling time is 6-8 hours, and the ball milling speed is 75-125 r / min.

[0017] The present invention also provides monodisperse silver-palladium alloy powder prepared by the preparation method described in the above technical solution.

[0018] The present invention provides a method for preparing a monodisperse silver-palladium alloy powder, comprising the following steps: adding a metal salt solution and a reducing agent solution to a dispersant solution at the same time, performing an oxidation-reduction reaction to obtain a silver-palladium alloy powder; the metal salt in the metal salt solution is silver nitrate and palladium nitrate; the reducing agent in the reducing agent solution is ascorbic acid or ferrous sulfate; the dispersant in the dispersant solution is one or more of polyvinyl pyrrolidone, glycerol and polyethylene glycol 400; and ball milling the silver-palladium alloy powder to obtain a monodisperse silver-palladium alloy powder. The present invention adopts a liquid phase chemical reduction method, and by selecting specific types of metal salts, reducing agents and dispersants, the pH conditions of silver-palladium alloying are controlled, the hydrolysis reaction of metal ions is suppressed in an acidic environment, and Ag is ensured. + With Pd 2+ The reduction potential of the two ions is close to each other, which promotes the simultaneous reduction of the two ions and avoids the preferential precipitation of a single metal to form a mixed powder. At the same time, by controlling the liquid addition method, the Ag + With Pd 2+The simultaneous reduction of the silver and palladium powders can avoid the component segregation caused by the difference in reduction rate, and effectively control the reaction rate, promote the orderly arrangement of atoms, and form nearly spherical particles with a high degree of alloying; then the silver and palladium metal powders can be fully mixed by ball milling to promote alloying, and the spherical morphology and particle size distribution of the silver-palladium powder can be effectively controlled to prepare a monodisperse silver-palladium alloy powder with good dispersibility and nearly spherical shape. The experimental results show that the silver-palladium alloy powder prepared by the preparation method provided by the present invention has a high degree of alloying, no agglomeration, good dispersibility, a nearly spherical morphology, and a particle size in the range of 100 to 600 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the XRD pattern of the monodisperse silver-palladium alloy powder prepared in Example 1 of the present invention;

[0020] Figure 2 The XRD diagram of the silver-palladium alloy powder prepared in Comparative Example 2 of the present invention;

[0021] Figure 3 This is the XRD pattern of the silver-palladium alloy powder prepared in Comparative Example 5 of the present invention;

[0022] Figure 4 This is a scanning electron microscope image of the monodisperse silver-palladium alloy powder prepared in Example 1 of the present invention;

[0023] Figure 5 This is a scanning electron microscope image of the monodisperse silver-palladium alloy powder prepared in Example 2 of the present invention;

[0024] Figure 6 This is a scanning electron microscope image of the monodisperse silver-palladium alloy powder prepared in Example 3 of the present invention;

[0025] Figure 7 This is a scanning electron microscope image of the silver-palladium alloy powder prepared in Comparative Example 1 of the present invention;

[0026] Figure 8 This is a scanning electron microscope image of the silver-palladium alloy powder prepared in Comparative Example 2 of the present invention;

[0027] Fig. 9 This is a scanning electron microscope image of the silver-palladium alloy powder prepared in Comparative Example 3 of the present invention;

[0028] Fig.10 This is a scanning electron microscope image of the silver-palladium alloy powder prepared in Comparative Example 4 of the present invention;

[0029] Fig.11 This is a scanning electron microscope image of the silver-palladium alloy powder prepared in Comparative Example 5 of the present invention;

[0030] Fig.12 This is the EDS image of the monodisperse silver-palladium alloy powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing monodisperse silver-palladium alloy powder, comprising the following steps:

[0032] Adding a metal salt solution and a reducing agent solution into a dispersant solution at the same time to carry out an oxidation-reduction reaction to obtain a silver-palladium alloy powder; the metal salt solution is an aqueous solution of silver nitrate and palladium nitrate;

[0033] The silver-palladium alloy powder is ball-milled to obtain monodisperse silver-palladium alloy powder.

[0034] The invention adds a metal salt solution and a reducing agent solution into a dispersant solution at the same time to carry out an oxidation-reduction reaction, thereby obtaining silver-palladium alloy powder.

[0035] In the present invention, the metal salt in the metal salt solution is silver nitrate and palladium nitrate. In the present invention, the concentration of the metal salt solution is preferably 10-17 g / L, more preferably 13-16 g / L; in an embodiment of the present invention, the concentration of the metal salt solution is 13.6 g / L, 15 g / L or 15.4 g / L. In the present invention, controlling the concentration of silver nitrate and palladium nitrate within the above range can ensure the deposition rate of silver and palladium during the reduction process, and can make the particles grow uniformly during the reaction process to form uniform and dispersed particles.

[0036] In the present invention, the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is preferably (7-15):(0.5-3), and more preferably (14-15):(0.5-3). In an embodiment of the present invention, the mass ratio of silver nitrate to palladium nitrate in the metal salt solution may be 14.2:1, 11:3, or 15:0.5. In the present invention, the composition of the silver-palladium alloy powder may be adjusted by controlling the mass ratio of zinc nitrate to palladium nitrate.

[0037] In the present invention, the solvent in the metal salt solution is preferably deionized water. The present invention has no special limitation on the preparation of the metal salt solution, and a solution of the desired concentration can be obtained by a method well known to those skilled in the art.

[0038] In the present invention, the reducing agent in the reducing agent solution is ascorbic acid or ferrous sulfate, preferably ascorbic acid. In the present invention, the reducing agent reduces the silver ions and palladium ions in silver nitrate and palladium nitrate to metallic silver and metallic palladium, thereby forming a silver-palladium alloy. The present invention selects the above-mentioned reducing agent, and its mild reducing ability helps to uniformly reduce silver and palladium ions, thereby forming a uniform silver-palladium alloy structure with a high degree of alloying.

[0039] In the present invention, the solvent of the reducing agent solution is preferably deionized water; the concentration of the reducing agent solution is preferably 25-70 g / L, more preferably 45-69 g / L. In the present invention, the molar ratio of the reducing agent in the reducing agent solution to the metal salt in the metal salt solution is preferably (2-5):1, more preferably (3-4):1. In the present invention, controlling the reducing agent solution to the above concentration and addition amount can control the speed of the reduction reaction, so that the particles grow uniformly during the reaction to form uniform and dispersed particles; avoid excessively high ascorbic acid concentrations that cause the reduction reaction to be too fast and the particles to agglomerate; avoid incomplete reduction caused by too low concentrations and addition amounts.

[0040] In the present invention, the dispersant in the dispersant solution is one or more of polyvinyl pyrrolidone, glycerol and polyethylene glycol 400. In the present invention, the dispersant can significantly improve the dispersibility of the particles, control the spherical morphology of the particles and the uniformity of the particle size; by limiting the type of the dispersant, it can be adsorbed on the surface of the metal ions to adjust the reduction rate of the metal ions, so that silver and palladium can be more uniformly co-deposited, thereby improving the degree of alloying.

[0041] In the present invention, the concentration of the dispersant solution is preferably 0.6-1.6 g / L, more preferably 0.7-1.5 g / L; the mass ratio of the dispersant in the dispersant solution to the metal salt in the metal salt solution is preferably (0.05-0.2):1, more preferably (0.1-0.2):1. In the present invention, by controlling the amount and concentration of the dispersant added, a monodisperse silver-palladium alloy powder with uniform particle size, good dispersibility and nearly spherical morphology can be prepared.

[0042] In the present invention, the metal salt solution and the reducing agent solution are preferably added to the dispersant solution simultaneously in a symmetrical manner, and the adding speed of the metal salt solution is preferably 1 to 3 drops / second, more preferably 2 drops / second, and the adding speed of the reducing agent solution is preferably 1 to 3 drops / second, more preferably 2 drops / second. The present invention obtains silver-palladium alloy powder by simultaneously adding the metal salt solution and the reducing agent solution to the dispersant solution for oxidation-reduction reaction, which can prevent particle agglomeration and help improve dispersibility; by controlling the adding rate of the metal salt solution and the reducing agent solution, the reaction can be further controlled to make Ag + With Pd 2+ Be reduced synchronously to improve the degree of alloying.

[0043] The present invention has no particular limitation on the temperature of the redox reaction, which can be at room temperature. In the present invention, the redox reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 500-1000 rpm; the stirring is stopped when the upper liquid is clear. The above stirring conditions improve the degree of alloying by promoting the mixing of reactants and preventing particle agglomeration.

[0044] After the redox reaction is completed, the present invention preferably performs natural sedimentation, washing and drying of the obtained product in sequence to obtain silver-palladium alloy powder. In the present invention, the natural sedimentation time is preferably 1 to 5 hours, more preferably 2 to 3 hours. The natural sedimentation time can achieve material separation and optimize particle size distribution.

[0045] In the present invention, the washing preferably uses 50° C. hot water to wash the reaction solution; the number of washings is preferably controlled until the conductivity of the solution approaches that of deionized water.

[0046] In the present invention, the drying is preferably carried out in a vacuum drying oven; the drying temperature is preferably 60 to 80° C., more preferably 65° C.; the drying time is preferably 8 to 12 hours, more preferably 12 hours.

[0047] After obtaining the silver-palladium alloy powder, the present invention ball-mills the silver-palladium alloy powder to obtain monodisperse silver-palladium alloy powder.

[0048] The present invention does not specifically limit the apparatus used for ball milling. In the embodiment of the present invention, an intelligent horizontal ball mill is used to ball mill the silver-palladium alloy powder. In the present invention, ball milling can fully mix the two metal powders of silver and palladium, promote the alloying reaction, and make the alloy composition more uniform; it can also make the shape of the alloy powder particles more regular and closer to a sphere; it can also crush larger particles into smaller particles, thereby achieving a more uniform particle size distribution.

[0049] In the present invention, the ball-to-material ratio of the ball milling is preferably 4-7:1, more preferably 5:1, the ball milling time is preferably 6-8 hours, and the ball milling speed is preferably 75-125 r / min. The above ball milling conditions can further optimize the uniformity and morphology of the particles and promote atomic diffusion and alloying.

[0050] After the ball milling is completed, the present invention preferably uses a mesh to filter the ball milling balls in the ball milling jar to obtain a product, and the obtained product is centrifuged, washed and dried to obtain a monodisperse silver-palladium alloy powder. The ball milling is preferably wet ball milling, and the liquid medium of the wet ball milling is preferably water. The drying temperature is preferably 50 to 100°C, more preferably 65°C; the drying time is preferably 1 to 10 hours. The above drying conditions in the present invention can ensure the effective evaporation of water.

[0051] The present invention also provides a monodisperse silver-palladium alloy powder prepared by the preparation method described in the above technical solution. In the present invention, the prepared silver-palladium alloy powder has a high degree of alloying, no agglomeration, good dispersibility, and a nearly spherical morphology.

[0052] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example 1

[0054] The preparation method of monodisperse silver-palladium alloy powder is as follows:

[0055] Mix 30mL (0.1g / mL) of palladium nitrate and 11g of silver nitrate, dissolve in 1L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 13.6g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 11:3). Dissolve 0.39mol of ascorbic acid in 1L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 69g / L, and the molar ratio of ascorbic acid to metal salt in the reducing agent solution is 5:1). Dissolve 1.4g of polyvinylpyrrolidone PVP in 2L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.7g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0056] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 500rmp, and the supernatant is stirred to a clear state. It is naturally settled for 2 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the silver-palladium alloy powder, which is placed in a vacuum drying oven for drying at a temperature of 65°C for 12 hours.

[0057] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 8 h, a ball-milling rate of 75 r / min, a drying temperature of 65° C., and a drying time of 12 h to obtain a monodisperse silver-palladium alloy powder.

[0058] Example 2

[0059] The preparation method of monodisperse silver-palladium alloy powder is as follows:

[0060] Mix 10 mL (0.1 g / mL) of palladium nitrate and 14.2 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 14.2:1). Dissolve 0.26 mol of ascorbic acid in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 45.76 g / L, and the molar ratio of ascorbic acid to metal salt in the reducing agent solution is 3:1). Dissolve 3.04 g of glycerol in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 1.52 g / L, and the mass ratio of the dispersant to the metal salt is 0.2:1).

[0061] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 600rmp, and the supernatant is stirred to a clear state. Natural sedimentation is carried out for 3 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the silver-palladium alloy powder, which is placed in a vacuum drying oven for drying at a temperature of 70°C for 10 hours.

[0062] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 6 hours, a ball-milling rate of 75 r / min, a drying temperature of 70° C., and a drying time of 10 hours to obtain a monodisperse silver-palladium alloy powder.

[0063] Example 3

[0064] The preparation method of monodisperse silver-palladium alloy powder is as follows:

[0065] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of ferrous sulfate in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 27.36 g / L, and the molar ratio of ferrous sulfate to metal salt in the reducing agent solution is 2:1). Dissolve 2.325 g of polyethylene glycol 400 in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 1.16 g / L, and the mass ratio of the dispersant to the metal salt is 0.15:1).

[0066] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 1000rmp, and the supernatant is stirred to a clear state. Natural sedimentation is carried out for 3 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the powder, which is then placed in a vacuum drying oven for drying at a temperature of 75°C for 10 hours.

[0067] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 8 hours, a ball-milling rate of 100 r / min, a drying temperature of 75° C., and a drying time of 10 hours to obtain a monodisperse silver-palladium alloy powder.

[0068] Comparative Example 1

[0069] The preparation method of silver-palladium alloy powder is as follows:

[0070] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of ascorbic acid in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 31.68 g / L, and the molar ratio of ascorbic acid to metal salt in the reducing agent solution is 2:1). Dissolve 1.55 g of gelatin in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.775 g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0071] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 500rmp, and the supernatant is stirred to a clear state. Natural sedimentation is carried out for 3 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the powder, which is then dried in a vacuum drying oven at a temperature of 60°C for 12 hours.

[0072] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 8 hours, a ball-milling rate of 100 r / min, a drying temperature of 75° C., and a drying time of 8 hours to obtain silver-palladium alloy powder.

[0073] Comparative Example 2

[0074] The preparation method of silver-palladium alloy powder is as follows:

[0075] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of ferrous sulfate in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 27.36 g / L, and the molar ratio of ferrous sulfate to metal salt in the reducing agent solution is 2:1). Dissolve 1.55 g of gelatin in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.775 g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0076] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 500rmp, and the supernatant is stirred to a clear state. The mixture is naturally settled for 3 hours, and washed with 50°C water to obtain a silver-palladium alloy powder. The powder is placed in a vacuum drying oven and dried at a temperature of 65°C for 10 hours to obtain a silver-palladium alloy powder.

[0077] Comparative Example 3

[0078] The preparation method of silver-palladium alloy powder is as follows:

[0079] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of hydrazine hydrate in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 9 g / L, and the molar ratio of hydrazine hydrate to metal salt in the reducing agent solution is 2:1). Dissolve 1.55 g of polyvinylpyrrolidone PVP in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.775 g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0080] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 500rmp, and the supernatant is stirred to a clear state. Natural sedimentation is carried out for 3 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the powder, which is then dried in a vacuum drying oven at a temperature of 60°C for 12 hours.

[0081] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 8 h, a ball-milling rate of 100 r / min, a drying temperature of 65° C., and a drying time of 10 h to obtain silver-palladium alloy powder.

[0082] Comparative Example 4

[0083] The preparation method of silver-palladium alloy powder is as follows:

[0084] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of ascorbic acid in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 31.68 g / L, and the molar ratio of ascorbic acid to metal salt in the reducing agent solution is 2:1). Dissolve 1.55 g of polyvinylpyrrolidone PVP in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.775 g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0085] The metal salt solution and the reducing agent solution are added to the dispersant solution at the same time under stirring to carry out redox reaction. The metal salt solution is added at a rate of 2 drops / second, the reducing agent solution is added at a rate of 2 drops / second, the stirring speed is 1000rmp, and the supernatant is stirred to a clear state. Natural sedimentation is carried out for 3 hours, and the silver-palladium alloy powder is washed with 50°C water to obtain the silver-palladium alloy powder, which is placed in a vacuum drying oven for drying at a temperature of 75°C for 8 hours to obtain the silver-palladium alloy powder.

[0086] Comparative Example 5

[0087] The preparation method of silver-palladium alloy powder is as follows:

[0088] Mix 5 mL (0.1 g / mL) of palladium nitrate and 15 g of silver nitrate, dissolve in 1 L of deionized water to obtain a metal salt solution (the concentration of the metal salt solution is 15.4 g / L, and the mass ratio of silver nitrate to palladium nitrate in the metal salt solution is 15:0.5). Dissolve 0.18 mol of ascorbic acid in 1 L of deionized water to obtain a reducing agent solution (the concentration of the reducing agent solution is 31.68 g / L, and the molar ratio of ascorbic acid to metal salt in the reducing agent solution is 2:1). Dissolve 1.55 g of polyvinylpyrrolidone PVP in 2 L of deionized water to prepare a dispersant solution (the concentration of the dispersant solution is 0.775 g / L, and the mass ratio of the dispersant to the metal salt is 0.1:1).

[0089] The reducing agent solution is first mixed with the dispersant solution to obtain a reducing agent mixed solution, and the reducing agent mixed solution is added to the metal salt solution under stirring to carry out an oxidation-reduction reaction. The reducing agent mixed solution is added at a rate of 2 drops / second and a stirring speed of 1000 rpm. The mixture is stirred until the supernatant becomes clear, and the mixture is naturally precipitated for 3 hours. The silver-palladium alloy powder is washed with 50°C water to obtain the silver-palladium alloy powder, and the powder is dried in a vacuum drying oven at a temperature of 60°C for 12 hours.

[0090] The obtained silver-palladium alloy powder was ball-milled and dried with a ball-to-material ratio of 5:1, a ball-milling time of 8 hours, a ball-milling rate of 100 r / min, a drying temperature of 75° C., and a drying time of 8 hours to obtain silver-palladium alloy powder.

[0091] XRD analysis was performed on the monodisperse silver-palladium alloy powder obtained in Example 1 and the silver-palladium alloy powders prepared in Comparative Examples 2 and 5 using an X-ray diffractometer. The XRD patterns were as follows: Figures 1 to 3 shown.

[0092] from Figure 1 It can be seen that the X-ray diffraction peaks of the monodisperse silver-palladium alloy powder prepared in Example 1 are shifted compared with the standard card of silver (01-087-0720) and the standard card of palladium (01-087-0637), and the silver peak is shifted to the right relative to the main element peak. Therefore, it is inferred that the prepared silver-palladium alloy powder is a silver-palladium alloy powder with a high degree of alloying. Figure 2 It can be seen that the silver-palladium powder synthesized in Comparative Example 2 and Example 1 shows a Pd (200) diffraction peak, and in addition to the silver-palladium diffraction peak, other impurity peaks appear, indicating that the synthesized silver-palladium alloy powder has poor purity and low alloying degree. Therefore, it is inferred that the silver-palladium alloy powder prepared by omitting the ball milling step and using gelatin as a dispersant has a low alloying degree. Figure 3 It can be seen that in comparison between the silver-palladium powder synthesized in Comparative Example 5 and Example 1, the diffraction peaks of silver and palladium are not completely merged, proving that the degree of alloying of the synthesized silver-palladium alloy is incomplete. Therefore, it is inferred that the silver-palladium alloy powder prepared by the asymmetric liquid addition method has a lower degree of alloying.

[0093] The microstructures of the monodisperse silver-palladium alloy powders prepared in Examples 1 to 3 and the silver-palladium alloy powders prepared in Comparative Examples 1 to 5 were observed using a scanning electron microscope, and the SEM images obtained were as follows: Figures 4 to 11 shown.

[0094] from Figures 4 to 6 It can be seen that the monodisperse silver-palladium alloy powder prepared in Example 1 has a dispersed nearly spherical property, and the particle size is in the range of 100 to 600 nm. The silver-palladium alloy powders prepared in Examples 2 and 3 have a dispersed nearly spherical property.

[0095] from Figure 7It can be seen that the silver-palladium alloy powder prepared in Comparative Example 1 is in a state of small particle aggregation, with slight agglomeration. Therefore, it is inferred that the silver-palladium alloy powder prepared by replacing the dispersant with gelatin has poor dispersibility.

[0096] from Figure 8 It can be seen that the silver-palladium powder prepared in Comparative Example 2 is a spherical shape formed by stacking flakes, and has poor dispersibility. Therefore, it is inferred that the silver-palladium alloy powder prepared by omitting the ball milling step and changing the dispersant to gelatin has poor dispersibility.

[0097] from Fig. 9 It can be seen that the silver-palladium powder prepared in Comparative Example 3 is small particles aggregated into blocks, and agglomeration is serious. Therefore, it is inferred that the alloy powder prepared by replacing the reducing agent with hydrazine hydrate has poor dispersibility.

[0098] from Fig.10 It can be seen that the silver-palladium powder particles prepared in Comparative Example 4 are irregular in shape and agglomerated. Therefore, it is inferred that if the ball milling step is omitted, the alloy powder prepared will have an irregular shape and poor dispersibility.

[0099] from Fig.11 It can be seen that although the silver-palladium powder prepared in Comparative Example 5 has a smaller particle size, it is severely agglomerated. Therefore, it can be inferred that the asymmetric liquid addition method will result in poor dispersion performance of the prepared alloy powder.

[0100] The palladium-silver alloy powder prepared in Example 1 was tested by energy dispersive X-ray spectrometer, and the EDS graphs were as follows: Fig.12 shown.

[0101] from Fig.12 It can be seen that the alloy powder prepared in Example 1 of the present invention has no other impurities and is of high purity.

[0102] It can be seen from the above embodiments and comparative examples that the monodisperse silver-palladium alloy powder provided by the present invention has a high degree of alloying, no agglomeration, good dispersibility, and a nearly spherical morphology.

[0103] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a monodisperse silver-palladium alloy powder, comprising the following steps: Adding a metal salt solution and a reducing agent solution to a dispersant solution at the same time to carry out an oxidation-reduction reaction to obtain a silver-palladium alloy powder; the metal salt in the metal salt solution is silver nitrate and palladium nitrate; the reducing agent in the reducing agent solution is ascorbic acid or ferrous sulfate; the dispersant in the dispersant solution is one or more of polyvinyl pyrrolidone, glycerol and polyethylene glycol 400; The silver-palladium alloy powder is ball-milled to obtain monodisperse silver-palladium alloy powder.

2. The preparation method according to claim 1, characterized in that: The mass ratio of silver nitrate to palladium nitrate in the metal salt solution is (7-15):(0.5-3).

3. The preparation method according to claim 1 or 2, characterized in that: The total concentration of the metal salt in the metal salt solution is 10-17 g / L.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the reducing agent in the reducing agent solution to the metal salt in the metal salt solution is (2-5):

1.

5. The preparation method according to claim 1, characterized in that: The concentration of the reducing agent solution is 25-70 g / L.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the dispersant in the dispersant solution to the metal salt in the metal salt solution is (0.05-0.2):

1.

7. The preparation method according to claim 1, characterized in that: The concentration of the dispersant solution is 0.6-1.6 g / L.

8. The preparation method according to claim 1, characterized in that: The redox reaction is carried out under stirring conditions, and the stirring speed is 500-1000 rpm.

9. The preparation method according to claim 1, characterized in that: The ball-to-material ratio of the ball mill is (4-7):1, the ball milling time is 6-8 hours, and the ball milling speed is 75-125 r / min.

10. Monodisperse silver-palladium alloy powder prepared by the preparation method according to any one of claims 1 to 9.

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