Supergravity system device and method for preparing high-density nano silver coated copper powder

Abstract

The invention discloses a supergravity system device and method for preparing high-density nano silver coated copper powder, and the supergravity system device comprises a first raw material tank, a second raw material tank, a copper suspension storage tank, a delivery pump, an ultrasonic feeder, a supergravity reactor, a stirring reactor, a reaction kettle, a gas cylinder, a cooler, a filter, a cleaning machine, a drying machine and a product outlet; the preparation method comprises the following steps: 1) preparing the nano-copper core; and 2) preparing the nano silver coated copper powder. According to the preparation method, the silver-coated copper powder can be continuously synthesized through a one-pot method, oxidation caused in the copper powder synthesis process is restrained, the pretreatment procedure of removing an oxidation layer on the surface of the copper powder before silver plating is omitted, material mixing is efficiently enhanced through the supergravity technology, the particle size is reduced, the silver layer coating uniformity is improved, and the silver-coated copper material with the excellent conductivity is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to a supergravity system device and method for preparing high-density nano silver-coated copper powder. Background Art

[0002] Conductive materials are key basic materials in the fields of metal corrosion protection, energy storage, sensors, and optoelectronics, and their performance optimization has always been a research focus. Copper (Cu) and silver (Ag), as classic inorganic conductive materials, have excellent conductive properties, but their direct application has significant defects. Cu materials are easily oxidized in air to form a Cu2O / CuO insulating layer, resulting in a sharp drop in conductivity, especially for Cu nanoparticles. Ag materials are expensive and have obvious ion migration effects, which can easily cause reliability issues such as circuit short circuits, arc discharges, and dielectric breakdown. Silver-coated copper (Cu@Ag) core-shell materials, by constructing a continuous silver coating on the surface of a copper substrate, combine the high conductivity and oxidation resistance of silver with the low cost of copper, becoming an ideal solution to the above contradictions.

[0003] At present, the typical methods of Cu@Ag core-shell particles include chemical plating, melt atomization, co-reduction and mechanical ball milling, among which the first two technologies dominate industrial production. Chemical plating is considered to be a favorable method for forming core-shell structures. A certain amount of Ag is added to the core-shell structure through the reducing agent or the replacement ability of Cu itself. + Reduction to Ag 0 Plating. Commonly used reducing agents include formaldehyde solution, glucose, tartrate, and hydrazine hydrate. However, the addition of reducing agents accelerates the reaction, making product quality control very difficult. During the reaction, additional complexing agents or buffers are usually required to suppress the formation of free silver particles and uneven plating.

[0004] Although the above methods can achieve the preparation of Cu@Ag core-shell structures, the non-uniformity of the coating is still the core bottleneck restricting the performance of the material. The non-uniform coating of Cu@Ag core-shell particles will lead to poor thermal stability, which means that the Ag shell will fall off the surface of the Cu particles at high temperatures, resulting in performance failure. Current research has confirmed that by introducing stabilizers or complexing agents during the preparation process, the coating can be uniformized under low silver loading conditions. However, strategies to improve the coating uniformity and conductive properties of the prepared Cu@Ag core-shell particles from the perspective of process intensification are still missing. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a high-gravity system device for preparing high-density nano silver-coated copper powder.

[0006] The second technical problem addressed by the present invention is to provide a method for preparing highly dense nano-silver-coated copper powder using the aforementioned hypergravity system. This method enables one-pot continuous synthesis of silver-coated copper powder, suppresses oxidation during the copper powder synthesis process, eliminates the pretreatment step of removing the oxide layer on the copper powder surface before silver plating, and utilizes hypergravity technology to efficiently enhance material mixing, reduce particle size, and improve the uniformity of the silver coating, resulting in a silver-coated copper material with excellent electrical conductivity.

[0007] In order to solve the above-mentioned first technical problem, the technical solution adopted by the present invention is as follows:

[0008] A high-gravity system device for preparing high-density nano silver-coated copper powder, comprising: a first raw material tank, a second raw material tank, a copper suspension storage tank, a delivery pump, an ultrasonic feeder, a high-gravity reactor, a stirring reactor, a reactor, a gas cylinder, a cooler, a filter, a cleaning machine, a dryer, and a product outlet;

[0009] The delivery pumps include a first delivery pump, a second delivery pump, a third delivery pump, a fourth delivery pump, a fifth delivery pump, and a sixth delivery pump;

[0010] The first raw material tank is connected to the high-gravity reactor through a pipeline and a first delivery pump;

[0011] The second raw material tank is connected to the high-gravity reactor through a pipeline and a second delivery pump;

[0012] The high-gravity reactor, stirring reactor and ultrasonic feeder are arranged on the same reactor; the reactor is connected to an external gas cylinder through a pipeline;

[0013] The bottom outlet of the reactor is connected to the high-gravity reactor through a pipeline and a third delivery pump to form an external circulation;

[0014] The copper suspension storage tank is connected to the high-gravity reactor through a pipeline and a fourth delivery pump. A branch pipeline is provided between the pipeline connecting the third delivery pump and the high-gravity reactor, and the branch pipeline leads to a cooler, a filter, a fifth delivery pump, a cleaning machine, a sixth delivery pump and a dryer in sequence;

[0015] The bottom outlet of the filter is circulated back to the copper suspension storage tank through a pipeline.

[0016] In order to solve the above second technical problem, the technical solution adopted by the present invention is as follows:

[0017] A method for preparing high-density nano silver-coated copper powder using the above-mentioned high-gravity system device comprises the following steps:

[0018] 1) Preparation of nano-copper cores

[0019] The raw materials are divided into two streams, namely, copper solution A and reducing solution B; gas is introduced into the reactor, and the copper solution A and reducing solution B are respectively input into the high-gravity reactor through a first delivery pump and a second delivery pump. The two solutions contact and react, and the materials after passing through the high-gravity reactor are dispersed and thrown to the wall of the reactor. Under the action of gravity, the materials gather at the bottom of the reactor and flow out through the bottom outlet. Then, they are again transported to the high-gravity reactor through a third delivery pump for dispersion and mixing, forming an external loop; after reciprocating at a certain temperature, a portion of the reaction liquid is transported into a cooler and a filter through the third delivery pump, and the liquid at the bottom outlet of the filter after removing part of the solvent is connected to the copper suspension storage tank through a pipeline; the cycle is repeated until a nano copper suspension that meets the requirements is obtained;

[0020] 2) Preparation of nano silver-coated copper powder

[0021] The third raw material is silver solution C; gas is introduced into the reactor, and the silver solution C and the copper suspension are respectively fed into the high-gravity reactor 8 via a second delivery pump and a fourth delivery pump; as in step 1), the reaction materials are repeatedly passed through the high-gravity reactor 8 for dispersion and mixing, forming an external loop; after reciprocating circulation at a certain temperature, the obtained silver-coated copper suspension is passed through a third delivery pump into a cooler, cooled to room temperature, and then passed into a filter for solid-liquid separation. The solid product is sequentially delivered to a washer and a dryer via a delivery pump, and washed and dried to obtain nano silver-coated copper powder.

[0022] Preferably, in step 1), the copper solution A is formed by uniformly mixing a copper source and a solvent, the copper source is one of copper sulfate, copper chloride, copper nitrate, copper acetate, copper chelate, and copper acetylacetonate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0023] Preferably, in step 1), the reducing solution B is a mixture formed by uniformly mixing a reducing agent, a protective agent, a pH regulator and a solvent; the reducing agent is one of borohydride, sodium hypophosphite, sodium potassium tartrate, potassium tartrate, formaldehyde, hydrazine hydrate, ascorbic acid, glucose, and phenylhydrazine; the protective agent is one of polyvinyl pyrrolidone, oleic acid, polyethylene glycol, hexadecyltrimethylammonium bromide, gelatin, and tetradecylphosphonic acid; the pH regulator is one of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, tartaric acid, citric acid, gluconic acid, oxalic acid, formic acid, phosphoric acid, and trifluoroacetic acid; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0024] Preferably, in step 1), the pH of the reducing solution B is 1-7.

[0025] Preferably, in step 2), the silver solution C is a mixture formed by uniformly mixing a silver source and a solvent, the silver source is one of silver nitrate, silver acetate, silver sulfate, silver ammonia complex, silver thiosulfate complex, and silver trifluoroacetate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0026] Preferably, in step 1) and step 2), the amount of the copper source is calculated as CuO, the amount of the silver source is calculated as Ag2O, and the molar ratio of each component is in the range of CuO: reducing agent: protective agent: Ag2O: solvent = 1: (0.5-10): (0-5): (0.02-0.5): (50-1000).

[0027] Preferably, in step 1) and step 2), the gas introduced into the reactor is nitrogen, helium, neon, argon, krypton, xenon, radon, One of hydrogen and carbon monoxide.

[0028] Preferably, in step 1) and step 2), the rotor speed in the high gravity reactor is 300-3000 r / min, preferably 2000-2850 r / min.

[0029] Preferably, in step 1) and step 2), the rotation speed of the stirring reactor on the reactor is 30-2000 r / min, preferably 200-2000 r / min.

[0030] Preferably, in step 1) and step 2), the ultrasonic frequency of the ultrasonic feeder on the reactor is 1-200 kHz, preferably 120-200 kHz.

[0031] Preferably, in step 1) and step 2), the temperature of the reciprocating cycle at a certain temperature is 30-300° C., and the number of reciprocating cycles is 15-1000, preferably 30-600.

[0032] Preferably, in step 2), the drying is carried out under vacuum or ambient atmosphere, with a drying temperature of 50-120° C. and a drying time of 6-12 h.

[0033] Any range described in the present invention includes the end value and any numerical value between the end values and any sub-range formed by the end value or any numerical value between the end values.

[0034] Unless otherwise specified, all raw materials in the present invention can be purchased commercially, and the equipment used in the present invention can adopt conventional equipment in the relevant field or refer to the existing technology in the relevant field.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) The hypergravity system device of the present invention utilizes the molecular mixing characteristics of hypergravity at a hundred times the force to introduce atmosphere to form an oxygen-isolating environment, and adopts an ultrasonic device to reduce particle adhesion on the device and achieve further nanoparticle dispersion, which is beneficial to reducing the average particle size of nano silver-coated copper powder particles by ≥30-1000nm, increasing the silver ion utilization rate by 5-25%, making the silver layer coating uniform, and thus significantly improving the conductive properties of the material. Its conductive properties can be improved by 1-2 orders of magnitude, thereby improving the quality and efficiency of industrial production of silver-coated copper powder.

[0037] 2) The present invention can continuously carry out the two-step production process of nano-copper cores and nano-silver-coated copper in the same reactor, which has the characteristics of simple operation process and small equipment footprint. The obtained nano-silver-coated copper powder can be widely used as a highly conductive filler to make various photovoltaic / conductive slurries, electromagnetic shielding coatings, conductive adhesives for electronic packaging, and other products. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0039] Figure 1 A schematic diagram of the structure of a high-gravity system device for preparing high-density nano silver-coated copper powder according to the present invention is shown;

[0040] Figure 2 The XRD pattern of the sample prepared in Example 1 of the present invention is shown;

[0041] Figure 3 The SEM-EDS image of the sample prepared in Example 1 of the present invention is shown;

[0042] Figure 4 Shown is the XRD of the sample prepared in Comparative Example 1 of the present invention;

[0043] Figure 5 The SEM-EDS image of the sample prepared in Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0044] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0045] See also Figure 1 As shown, as one aspect of the present invention, a high-gravity system device for preparing high-density nano silver-coated copper powder includes a first raw material tank 1, a second raw material tank 2, a copper suspension storage tank 5, a delivery pump, an ultrasonic feeder 7, a high-gravity reactor 8, a stirring reactor 9, a reactor 10, a gas cylinder 11, a cooler 13, a filter 14, a cleaning machine 16, a dryer 18, and a product outlet 19;

[0046] The delivery pumps include a first delivery pump 4, a second delivery pump 3, a third delivery pump 12, a fourth delivery pump 6, a fifth delivery pump 15, and a sixth delivery pump 17;

[0047] The first raw material tank 1 is connected to the high gravity reactor 8 through a pipeline and a first delivery pump 4;

[0048] The second raw material tank 2 is connected to the high gravity reactor 8 through a pipeline and a second delivery pump 3;

[0049] The high-gravity reactor 8, the stirring reactor 9 and the ultrasonic feeder 7 are arranged on the same reactor 10; the reactor 10 is connected to the gas cylinder 11 through a pipeline;

[0050] The bottom outlet of the reactor 10 is connected to the high-gravity reactor 8 through a pipeline and a third delivery pump 12 to form an external circulation;

[0051] The copper suspension storage tank 5 is connected to the high-gravity reactor 8 through a pipeline and a fourth delivery pump 6. A branch pipeline is provided between the pipeline connecting the third delivery pump 12 and the high-gravity reactor 8. The branch pipeline leads to a cooler 13, a filter 14, a fifth delivery pump 15, a cleaning machine 16, a sixth delivery pump 17 and a dryer 18 in sequence. The outlet of the dryer 18 leads to a product outlet 19;

[0052] The bottom outlet of the filter 14 is circulated back to the copper suspension storage tank 5 through a pipeline.

[0053] As another aspect of the present invention, a method for preparing high-density nano silver-coated copper powder using the above-mentioned high-gravity system device comprises the following steps:

[0054] 1) Preparation of nano-copper cores

[0055] The raw materials are divided into two streams, namely, copper solution A and reducing solution B; gas is introduced into the reactor, and the copper solution A and reducing solution B are respectively input into the high-gravity reactor through a first delivery pump and a second delivery pump. The two solutions contact and react, and the materials after passing through the high-gravity reactor are dispersed and thrown to the wall of the reactor. Under the action of gravity, the materials gather at the bottom of the reactor and flow out through the bottom outlet. Then, they are again transported to the high-gravity reactor through a third delivery pump for dispersion and mixing, forming an external loop; after reciprocating at a certain temperature, a portion of the reaction liquid is transported into a cooler and a filter through the third delivery pump, and the liquid at the bottom outlet of the filter after removing part of the solvent is connected to the copper suspension storage tank through a pipeline; the cycle is repeated until a nano copper suspension that meets the requirements is obtained;

[0056] 2) Preparation of nano silver-coated copper powder

[0057] The third raw material is silver solution C; gas is introduced into the reactor, and the silver solution C and the copper suspension are respectively fed into the high-gravity reactor 8 via a second delivery pump and a fourth delivery pump; as in step 1), the reaction materials are repeatedly passed through the high-gravity reactor 8 for dispersion and mixing, forming an external loop; after reciprocating circulation at a certain temperature, the obtained silver-coated copper suspension is passed through a third delivery pump into a cooler, cooled to room temperature, and then passed into a filter for solid-liquid separation. The solid product is sequentially delivered to a washer and a dryer via a delivery pump, and washed and dried to obtain nano silver-coated copper powder.

[0058] According to certain embodiments of the present invention, in step 1), the copper solution A is formed by uniformly mixing a copper source and a solvent, wherein the copper source is one of copper sulfate, copper chloride, copper nitrate, copper acetate, copper chelate, and copper acetylacetonate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0059] According to certain embodiments of the present invention, in step 1), the reducing solution B is a mixture formed by uniformly mixing a reducing agent, a protective agent, a pH regulator, and a solvent; the reducing agent is one of borohydride, sodium hypophosphite, sodium potassium tartrate, potassium tartrate, formaldehyde, hydrazine hydrate, ascorbic acid, glucose, and phenylhydrazine; the protective agent is one of polyvinyl pyrrolidone, oleic acid, polyethylene glycol, hexadecyltrimethylammonium bromide, gelatin, and tetradecylphosphonic acid; the pH regulator is one of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, tartaric acid, citric acid, gluconic acid, oxalic acid, formic acid, phosphoric acid, and trifluoroacetic acid; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0060] According to certain embodiments of the present invention, in step 1), the pH of the reducing solution B is 1-7.

[0061] According to certain embodiments of the present invention, in step 2), the silver solution C is a mixture formed by uniformly mixing a silver source and a solvent, wherein the silver source is one of silver nitrate, silver acetate, silver sulfate, silver ammonia complex, silver thiosulfate complex, and silver trifluoroacetate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

[0062] According to certain embodiments of the present invention, in step 1) and step 2), the amount of the copper source is calculated as CuO, the amount of the silver source is calculated as Ag2O, and the molar ratio of each component ranges from CuO: reducing agent: protective agent: Ag2O: solvent = 1: (0.5-10): (0-5): (0.02-0.5): (50-1000).

[0063] According to certain embodiments of the present invention, in step 1) and step 2), the gas introduced into the reactor is nitrogen, helium, neon, argon, krypton, xenon, radon, One of hydrogen and carbon monoxide.

[0064] According to certain embodiments of the present invention, in step 1) and step 2), the rotor speed in the high gravity reactor is 300-3000 r / min, preferably 2000-2850 r / min.

[0065] According to certain embodiments of the present invention, in step 1) and step 2), the rotation speed of the stirring reactor on the reactor is 30-2000 r / min, preferably 200-2000 r / min.

[0066] According to certain embodiments of the present invention, in step 1) and step 2), the ultrasonic frequency of the ultrasonic feeder on the reactor is 1-200 kHz, preferably 120-200 kHz.

[0067] According to certain embodiments of the present invention, in step 1) and step 2), the temperature of the reciprocating cycle at a certain temperature is 30-300° C., and the number of reciprocating cycles is 15-1000, preferably 30-600.

[0068] According to certain embodiments of the present invention, in step 2), the drying is performed under vacuum or ambient atmosphere, with a drying temperature of 50-120° C. and a drying time of 6-12 h.

[0069] Example 1

[0070] A method for preparing high-density nano silver-coated copper powder using the above-mentioned high-gravity system device comprises the following steps:

[0071] 1) Preparation of Nanocopper Cores: Dissolve 1g of copper sulfate pentahydrate in 40mL of ethylene glycol as a copper solution; dissolve 2.31g of sodium hypophosphite and 5.79g of polyvinylpyrrolidone in 60mL of ethylene glycol, and adjust the pH to 4 with sulfuric acid as a reducing solution. Two peristaltic pumps were used to feed the reaction, and the reaction was carried out at a high-gravity speed of 2850rpm and a stirred reactor speed of 300rpm. The reactor temperature was controlled at 85°C. After 40 minutes of reaction, the resulting copper suspension was filtered to remove 40mL of solvent, and then transferred to a copper suspension storage tank for later use.

[0072] 2) Preparation of Nano-Silver-Coated Copper Powder: 0.17 g of silver nitrate was dissolved in 20 mL of ethylene glycol as a silver solution. The silver solution and the copper suspension were simultaneously introduced into a high-gravity reactor. The reaction was carried out at a high-gravity speed of 2850 rpm and a stirring reactor speed of 300 rpm. The reactor temperature was controlled at 85°C. After 40 minutes of reaction, the reaction solution was cooled and filtered. The solid obtained was washed and dried to obtain nano-silver-coated copper powder. The particle size was 125 ± 75 nm, the silver layer was uniformly coated, the mass fraction of the Ag element was 35%, and the powder resistivity was 1.56 × 10 at 20 MPa. -5 Ω·cm.

[0073] Example 2

[0074] A method for preparing high-density nano silver-coated copper powder using the above-mentioned high-gravity system device comprises the following steps:

[0075] 3 g of copper nitrate trihydrate was dissolved in 60 mL of propylene glycol as a copper solution; 8.33 g of sodium hypophosphite was dissolved in 120 mL of propylene glycol and its pH was adjusted to 3 using nitric acid as a reducing solution; 0.42 g of silver nitrate was dissolved in 60 mL of propylene glycol as a silver solution; nitrogen was introduced into the reactor to isolate oxygen, and two peristaltic pumps were used to simultaneously transport the copper solution and the reducing solution to a high-gravity reactor. The reaction was carried out at a high-gravity speed of 2850 rpm, a stirring reactor speed of 300 rpm, and an ultrasonic frequency of 150 kHz. The temperature of the reactor was controlled at 90°C. After reacting for 20 minutes, the silver solution was simultaneously pumped into the high-gravity reactor for silver plating. After reacting for 1 hour, the reaction solution was cooled and filtered, and the obtained solid was washed and dried to obtain nano-silver-coated copper powder. XRD characterization of the product showed that it only contained Ag phase, the silver layer was uniformly coated, the particle size was 265±85 nm, and the powder resistivity was 1.08×10 -5 Ω·cm.

[0076] Example 3

[0077] A method for preparing high-density nano silver-coated copper powder using the above-mentioned high-gravity system device comprises the following steps:

[0078] 3 g of copper acetate monohydrate was dissolved in 30 mL of ethanol as a copper solution; 6.84 g of ascorbic acid and 3.5 g of polyethylene glycol were dissolved in 70 mL of ethanol, and acetic acid was used to adjust the pH to 3 as a reducing solution; 0.47 g of silver acetate was dissolved in 60 mL of ethanol as a silver solution; two peristaltic pumps were used to simultaneously transport the copper solution and the reducing solution to a high-gravity reactor, and the reaction was carried out at a high-gravity speed of 2500 rpm, a stirring reactor speed of 300 rpm, and an ultrasonic frequency of 150 kHz, and the reactor temperature was controlled at 80°C; after the reaction for 40 minutes, the silver solution was simultaneously pumped into the high-gravity reactor for silver plating; after the reaction for 1 hour, the reaction solution was cooled and filtered, the obtained solid was washed, and the nano-silver-coated copper powder was obtained after drying. The product XRD characterization showed that it only contained Ag phase, the silver layer was uniformly coated, the particle size was 215±80 nm, and the powder resistivity was 1.68×10 -5 Ω·cm.

[0079] Comparative Example 1

[0080] The same method as in Example 1 was used, except that the reaction was not conducted in a high-gravity reactor. The copper cores and silver-coated copper powder were synthesized under stirring only, with all other conditions remaining the same. The resulting product contained two phases, Ag and Cu2O, with a particle size of 170 ± 65 nm and an Ag mass fraction of 15%.

[0081] It can be seen that the poor mixing effect of the substances during the reaction will lead to a decrease in the utilization efficiency of silver ions during the reaction, uneven silver coating of the obtained silver-coated copper powder, larger particle size, wider particle size distribution, easy oxidation of the product, and poor conductivity. The powder resistivity at 20 MPa is 1.90×10 -2 Ω·cm.

[0082] Comparative Example 2

[0083] The same method as in Example 1 was used, except that the reaction time for preparing the nano-copper cores was changed to 5 min, and all other conditions remained the same. The obtained product contained three phases: Ag, Cu, and Cu2O.

[0084] It can be seen from this that the number of material reciprocating cycles / reaction time during the preparation of nano-copper cores is insufficient, which will result in the inability of Cu to fully nucleate and crystallize, thereby affecting the preparation process of silver-coated copper powder, and it is impossible to obtain silver-coated copper powder with uniform silver plating, and the prepared product is easily oxidized.

[0085] Comparative Example 3

[0086] The same method as in Example 1 was used, except that the reaction time for preparing nano-silver-coated copper powder was changed to 5 min, while other conditions remained the same. The obtained product contained three phases: Ag, Cu, and Cu2O.

[0087] It can be seen that the number of material reciprocating cycles / reaction time in the preparation process of nano silver-coated copper is not enough, which will lead to Ag + It cannot be fully reduced and coated on the surface of the copper core, and the exposed copper core is easily oxidized.

[0088] Comparative Example 4

[0089] The same as Example 2, except that ultrasound was not fed into the reaction process, and other conditions remained the same. After the reaction was completed, no or only a small amount of solid product was obtained, and most of the solid product adhered to the equipment.

[0090] It can be seen that if ultrasound is not fed into the reaction process, the solid product will easily adhere to the wall of the reactor, resulting in a decrease in yield.

[0091] Comparative Example 5

[0092] The same as Example 2, except that the stirring device was not turned on during the reaction, and other conditions were kept the same. The obtained product was detected to contain three phases: Ag, Cu and Cu2O.

[0093] It can be seen from this that when no stirring device is added during the reaction process, part of the prepared copper particles are deposited at the bottom and are not fully dispersed by the high-gravity reactor, which can easily lead to uneven silver plating, copper is exposed to the air, and the product is then oxidized.

[0094] Comparative Example 6

[0095] The same method as in Example 3 was used, except that the amount of ascorbic acid added was changed. 30.78 g of ascorbic acid and 3.5 g of polyethylene glycol were dissolved in 70 ml of water, and the pH was adjusted to 3 with acetic acid. All other conditions remained the same. The resulting product showed three phases: Ag, Cu, and Cu2O.

[0096] It can be seen that when excessive reducing agent is added during the reaction, the excessively fast reaction speed leads to the formation of free silver, and the copper core that is not fully coated is exposed to the air and is easily oxidized.

[0097] Comparative Example 7

[0098] The same method as in Example 3 was used, except that the type of silver source was changed. 0.40 g of silver chloride was dispersed in 60 mL of ethanol as the silver solution, and all other conditions remained the same. The resulting product was mainly Cu and Cu2O, with a small amount of Ag.

[0099] It can be seen from this that the silver source used releases silver ions in the solution too slowly, which will affect the silver plating speed. The copper core cannot be fully wrapped and is easily oxidized when exposed to the air.

[0100] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications based on the above description are possible. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A high gravity system device for preparing high-density nano silver-coated copper powder, characterized in that: It includes the first raw material tank, the second raw material tank, the copper suspension storage tank, the delivery pump, the ultrasonic feeder, the high-gravity reactor, the stirring reactor, the reactor, the gas cylinder, the cooler, the filter, the cleaning machine, the dryer, and the product outlet; The delivery pumps include a first delivery pump, a second delivery pump, a third delivery pump, a fourth delivery pump, a fifth delivery pump, and a sixth delivery pump; The first raw material tank is connected to the high-gravity reactor through a pipeline and a first delivery pump; The second raw material tank is connected to the high-gravity reactor through a pipeline and a second delivery pump; The high-gravity reactor, stirring reactor and ultrasonic feeder are arranged on the same reactor; the reactor is connected to an external gas cylinder through a pipeline; The bottom outlet of the reactor is connected to the high-gravity reactor through a pipeline and a third delivery pump to form an external circulation; The copper suspension storage tank is connected to the high-gravity reactor through a pipeline and a fourth delivery pump. A branch pipeline is provided between the pipeline connecting the third delivery pump and the high-gravity reactor, and the branch pipeline leads to a cooler, a filter, a fifth delivery pump, a cleaning machine, a sixth delivery pump and a dryer in sequence; The bottom outlet of the filter is circulated back to the copper suspension storage tank through a pipeline.

2. A method for preparing high-density nano silver-coated copper powder using the hypergravity system device according to claim 1, characterized in that: The steps include: 1) Preparation of nano-copper cores The raw materials are divided into two streams, namely, copper solution A and reducing solution B; gas is introduced into the reactor, and the copper solution A and reducing solution B are respectively input into the high-gravity reactor through a first delivery pump and a second delivery pump. The two solutions contact and react, and the materials after passing through the high-gravity reactor are dispersed and thrown to the wall of the reactor. Under the action of gravity, the materials gather at the bottom of the reactor and flow out through the bottom outlet. Then, they are again transported to the high-gravity reactor through a third delivery pump for dispersion and mixing, forming an external loop; after reciprocating at a certain temperature, a portion of the reaction liquid is transported into a cooler and a filter through the third delivery pump, and the liquid at the bottom outlet of the filter after removing part of the solvent is connected to the copper suspension storage tank through a pipeline; the cycle is repeated until a nano copper suspension that meets the requirements is obtained; 2) Preparation of nano silver-coated copper powder The third raw material is silver solution C; gas is introduced into the reactor, and the silver solution C and the copper suspension are respectively fed into the high-gravity reactor 8 via a second delivery pump and a fourth delivery pump; as in step 1), the reaction materials are repeatedly passed through the high-gravity reactor 8 for dispersion and mixing, forming an external loop; after reciprocating circulation at a certain temperature, the obtained silver-coated copper suspension is passed through a third delivery pump into a cooler, cooled to room temperature, and then passed into a filter for solid-liquid separation. The solid product is sequentially delivered to a washer and a dryer via a delivery pump, and washed and dried to obtain nano silver-coated copper powder.

3. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1), the copper solution A is formed by uniformly mixing a copper source and a solvent, wherein the copper source is one of copper sulfate, copper chloride, copper nitrate, copper acetate, copper chelate, and copper acetylacetonate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

4. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1), the reducing solution B is a mixture formed by uniformly mixing a reducing agent, a protective agent, a pH regulator, and a solvent; the reducing agent is one of borohydride, sodium hypophosphite, sodium potassium tartrate, potassium tartrate, formaldehyde, hydrazine hydrate, ascorbic acid, glucose, and phenylhydrazine; the protective agent is one of polyvinyl pyrrolidone, oleic acid, polyethylene glycol, hexadecyltrimethylammonium bromide, gelatin, and tetradecylphosphonic acid; the pH regulator is one of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, tartaric acid, citric acid, gluconic acid, oxalic acid, formic acid, phosphoric acid, and trifluoroacetic acid; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

5. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1), the pH of the reducing solution B is 1-7.

6. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 2), the silver solution C is a mixture formed by uniformly mixing a silver source and a solvent, wherein the silver source is one of silver nitrate, silver acetate, silver sulfate, silver ammonia complex, silver thiosulfate complex, and silver trifluoroacetate; and the solvent is one of water, ethylene glycol, propylene glycol, ethanol, methanol, acetone, oleylamine, diethylene glycol, and benzyl alcohol.

7. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1) and step 2), the amount of the copper source is calculated as CuO, the amount of the silver source is calculated as Ag2O, and the molar ratio of each component is in the range of CuO: reducing agent: protective agent: Ag2O: solvent = 1: (0.5-10): (0-5): (0.02-0.5): (50-1000).

8. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1) and step 2), the gas introduced into the reactor is nitrogen, helium, neon, argon, krypton, xenon, radon, One of hydrogen and carbon monoxide.

9. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1) and step 2), the rotor speed in the high gravity reactor is 300-3000 r / min, preferably 2000-2850 r / min.

10. The method for preparing high-density nano silver-coated copper powder according to claim 2, characterized in that: In step 1) and step 2), the rotation speed of the stirring reactor on the reactor is 30-2000 r / min, preferably 200-2000 r / min; Preferably, in step 1) and step 2), the ultrasonic frequency of the ultrasonic feeder on the reactor is 1-200 kHz, preferably 120-200 kHz; Preferably, in step 1) and step 2), the temperature of the reciprocating cycle at a certain temperature is 30-300° C., and the number of reciprocating cycles is 15-1000, preferably 30-600; Preferably, in step 2), the drying is carried out under vacuum or ambient atmosphere, with a drying temperature of 50-120° C. and a drying time of 6-12 h.

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