CN115570133A - Preparation method of silver-coated aluminum powder for electromagnetic shielding material conductive rubber - Google Patents
Preparation method of silver-coated aluminum powder for electromagnetic shielding material conductive rubber Download PDFInfo
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- CN115570133A CN115570133A CN202211325092.1A CN202211325092A CN115570133A CN 115570133 A CN115570133 A CN 115570133A CN 202211325092 A CN202211325092 A CN 202211325092A CN 115570133 A CN115570133 A CN 115570133A
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- silver
- aluminum powder
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 82
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 71
- 239000004332 silver Substances 0.000 title claims abstract description 70
- 239000000463 material Substances 0.000 title claims abstract description 18
- 229920001971 elastomer Polymers 0.000 title claims abstract description 13
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000011701 zinc Substances 0.000 claims abstract description 21
- 238000007747 plating Methods 0.000 claims abstract description 19
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 17
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 17
- 239000002245 particle Substances 0.000 claims abstract description 14
- 230000004048 modification Effects 0.000 claims abstract description 7
- 238000012986 modification Methods 0.000 claims abstract description 7
- 238000005246 galvanizing Methods 0.000 claims abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 46
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 22
- 239000000243 solution Substances 0.000 claims description 22
- 238000004140 cleaning Methods 0.000 claims description 18
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 16
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 11
- 239000011780 sodium chloride Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000012670 alkaline solution Substances 0.000 claims description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 8
- 230000007935 neutral effect Effects 0.000 claims description 7
- 101710134784 Agnoprotein Proteins 0.000 claims description 6
- 239000008139 complexing agent Substances 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 238000007598 dipping method Methods 0.000 claims description 6
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 6
- 238000006073 displacement reaction Methods 0.000 claims description 5
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 claims description 5
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 claims description 5
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical compound [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 claims description 5
- 239000001509 sodium citrate Substances 0.000 claims description 5
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims description 5
- 235000011006 sodium potassium tartrate Nutrition 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 238000000967 suction filtration Methods 0.000 claims description 5
- 239000011787 zinc oxide Substances 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 3
- 241000080590 Niso Species 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 229940074439 potassium sodium tartrate Drugs 0.000 claims description 3
- 239000011734 sodium Substances 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 2
- 239000011362 coarse particle Substances 0.000 claims description 2
- 230000002349 favourable effect Effects 0.000 claims description 2
- 239000010419 fine particle Substances 0.000 claims description 2
- 239000001476 sodium potassium tartrate Substances 0.000 claims description 2
- 238000005238 degreasing Methods 0.000 claims 1
- 238000003746 solid phase reaction Methods 0.000 claims 1
- 229910052782 aluminium Inorganic materials 0.000 abstract description 8
- 238000001125 extrusion Methods 0.000 abstract description 2
- 238000010008 shearing Methods 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 7
- 229910052802 copper Inorganic materials 0.000 description 5
- 239000010949 copper Substances 0.000 description 5
- 229920001690 polydopamine Polymers 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 2
- 229910021607 Silver chloride Inorganic materials 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000009713 electroplating Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 239000008103 glucose Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 238000005844 autocatalytic reaction Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- YCIMNLLNPGFGHC-UHFFFAOYSA-N catechol Chemical group OC1=CC=CC=C1O YCIMNLLNPGFGHC-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010028 chemical finishing Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000011549 displacement method Methods 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- MOFOBJHOKRNACT-UHFFFAOYSA-N nickel silver Chemical compound [Ni].[Ag] MOFOBJHOKRNACT-UHFFFAOYSA-N 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/17—Metallic particles coated with metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/52—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating using reducing agents for coating with metallic material not provided for in a single one of groups C23C18/32 - C23C18/50
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemically Coating (AREA)
Abstract
The invention discloses a preparation method of silver-coated aluminum powder for electromagnetic shielding material conductive rubber, which is characterized in that aluminum powder with the particle size of 10-100 um is subjected to surface oil removal, surface finishing modification, galvanizing and silver plating, and then is washed, filtered and dried to obtain the silver-coated aluminum powder, wherein the silver content is 15-30%, and the aluminum content is 70-85%. The silver-coated aluminum powder prepared by the steps of the method has excellent binding force and conductivity between silver and aluminum interfaces due to the existence of the preplated thin zinc layer. The silver-coated aluminum powder prepared by the invention has excellent shearing resistance and extrusion performance and excellent conductivity when being mixed with rubber.
Description
Technical Field
The invention belongs to the technical field of materials, relates to an electromagnetic shielding material technology, and particularly relates to a preparation technology of a conductive functional powder material for an electromagnetic shielding material.
Background
Electronic communication plays an important role in modern life, but electromagnetic radiation generated by electronic products also has obvious interference influence on human bodies and surrounding environments, so that certain harmfulness is caused, and the adoption of an electromagnetic shielding material for shielding electromagnetic waves is one of main prevention means. The conductive silicone rubber is a very important electromagnetic shielding material, which can fill gaps of electronic equipment and instruments and can be connected with devices such as an EMI shielding window and a ventilation waveguide. The main raw materials for producing the conductive rubber are conductive silver-coated copper powder, silver-coated aluminum powder, silver-coated nickel powder, silver-coated graphite powder, pure silver powder and other high-conductivity fillers. The aluminum powder has the advantages of difficult oxidation, small density, low price and the like, and is widely applied to the fields of electronics, aviation and the like. However, since metallic aluminum is an amphoteric metal, it cannot be used in a complicated environment; in addition, the application of the aluminum powder in the high-conductivity field is limited due to the poor conductivity of the aluminum powder. The silver-coated aluminum powder not only overcomes the defects of amphoteric metal of the aluminum powder, but also can greatly improve the conductivity of the aluminum powder due to the existence of the silver-coated surface layer, so that the silver-coated surface layer can be used as a high-conductivity filler to prepare a material with good shielding efficiency.
Patent CN 111531168A (application No. 2020.08.14) provides a method for preparing silver-coated aluminum material for electromagnetic shielding, which is proposed by suzui, firstly, pretreating aluminum powder, then placing the pretreated aluminum powder into a constant-temperature magnetic stirrer, dropwise adding a proper amount of copper nitrate solution, simultaneously adding fluoride, stirring uniformly, and obtaining copper-coated aluminum powder after complete reaction; and then placing the copper-coated aluminum powder in a constant-temperature magnetic stirrer, dropwise adding a proper amount of silver nitrate solution, simultaneously adding a complexing agent, uniformly stirring, and reacting completely to obtain the silver-coated aluminum powder.
A journal article of Suxiaepii et al, namely the influence of different reducing agents on the microstructure and performance of silver-plated aluminum powder ([ J ]. Proc. Western An university of engineering, 2022, 36 (3): 106-114), proposes that nickel is plated on the surface of aluminum powder, silver is plated by a tartaric acid + glucose double reduction system, and the silver deposition process comprises four processes of silver-nickel replacement → silver particle deposition → silver layer expansion → silver autocatalysis growth.
Zhang Zhenhua et al (silver coated aluminum powder process research [ J ]. Electroplating and coating, 2007, 26 (1): 23-25) remove surface oxide film by alkali cleaning, then plate copper on the aluminum powder surface, and then plate silver on the copper surface by displacement method.
Zhang love woman et al (research on chemical silver plating process of aluminum ball [ J)]Electroplating and environmental protection, 2016, 36 (1): 24-26) carrying out surface pretreatment on the aluminum ball by utilizing polydopamine, uniformly coating a layer of polydopamine on the surface layer of the aluminum powder matrix, wherein the amino group and the catechol group of the polydopamine have weak reducibilityCan form high active points on the surface of the aluminum ball, and then Ag is reacted under the action of reducing agent such as glucose and the like + Reducing the silver into a silver coating, and finally obtaining the silver coating with uniform and compact coating.
Aiming at various methods for coating the aluminum powder with silver, fluoride has great influence on the environment and brings great pressure to environmental protection; when nickel is replaced and plated on the surface of the aluminum powder, the nickel layer is loose, and the finally formed surface silver layer is not compact; when the intermediate layer is subjected to replacement copper plating, the silver-coated aluminum powder cannot resist high temperature due to the existence of copper atoms or copper ions; the surface of the aluminum powder is modified by using polydopamine, and the process is only suitable for low-concentration silver nitrate solution.
Disclosure of Invention
Aiming at the problems brought forward by the background technology, the invention provides a preparation method of silver-coated aluminum powder with good binding force between silver coating and aluminum powder interface and complete and compact coating.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
a preparation method of silver-coated aluminum powder for conductive rubber of an electromagnetic shielding material comprises the steps of carrying out chemical finishing modification on the surface of aluminum powder, carrying out chemical galvanizing and then carrying out silver plating, so that the binding force and compactness between a silver plating layer and a matrix are improved, and composite powder with a complete and compact coating structure is formed;
the preparation process comprises the following steps:
(1) Selecting 10-100 um aluminum powder, performing surface oil removal and oxide film treatment for 3-10 min by adopting alkaline solution at room temperature, and performing cleaning and suction filtration for later use;
(2) In order to improve the specific surface area of the aluminum powder and improve the thickness and the conductivity of the silver coating, the aluminum powder after deoiling and oxidation film is immersed into strong alkaline solution for surface finishing modification at normal temperature for 20-60 min, and then is cleaned and filtered for standby;
(3) Putting the aluminum powder with the polished and finished surface into a zinc plating solution at 15-25 ℃, stirring for 30-60 s, cleaning, and carrying out suction filtration for later use;
(4) And stirring the galvanized aluminum powder at 30-50 ℃ under the acidic condition that the pH is = 2-3 to generate displacement chemical silvering until silver floccules in the solution completely disappear, and cleaning, filtering, and drying to obtain a finished product.
The aluminum powder in the step 1 is spherical-like, and the particle size is 10-100 um, wherein 10-20 um is fine particle size, 20-60 um is medium particle size, and 60-100 um is coarse particle size.
In the step 1, the alkali used in the alkaline solution for removing oil on the surface is NaOH or KOH, preferably NaOH, the prepared concentrated solution is 1% -5%, the optimal selection is 2%, the used temperature is room temperature, the optimal time is 5min, and the used cleaning solution is deionized water and is cleaned to be neutral.
The surface finishing modification in the step 2 is to reduce the specific surface area of the aluminum powder by etching the protrusions on the surfaces of the aluminum powder particles and the attached tiny aluminum particles, so as to improve the thickness of the silver plating layer and improve the conductivity of the silver-coated aluminum powder, wherein the used strong alkaline solution is a mixture of NaOH, sodium potassium tartrate and water, and the mass percentage of the mixture is NaOH: potassium sodium tartrate: water =6, the temperature used is 25 ℃, the optimal time used is 25min, and the cleaning solution used is deionized water, and the cleaning is performed to neutrality.
The aluminum powder galvanizing in the step 3 is to prepare 5-12 g/L of zinc oxide, 50-100 g/L of sodium hydroxide, 10-30 g/L of nickel sulfate, 9-14 g/L of sodium citrate and 20-120 g/L of complexing agent into mixed solution. Wherein zinc oxide (Zn) 2 O) is preferably 8g/L, sodium hydroxide (NaOH) is preferably 65g/L, nickel sulfate (NiSO) 4 ) Preferably 22g/L, adding Ni 2+ Can be co-deposited with zinc to inhibit the growth of zinc, so that the crystal nucleus generation speed is higher than the grain growth speed, the size of zinc grains in the zinc dipping layer is reduced, the zinc dipping layer is thinner and more delicate, and the sodium citrate (C) is favorable for improving the binding force between the zinc dipping layer and the base 6 H 5 Na 3 O 7 ) Preferably 12g/L and the complexing agent (EDTA) preferably 86g/L. The temperature is 21 ℃, the time is 35s, and the cleaning solution is deionized water and is cleaned to be neutral.
The displacement electroless silver plating in the above step 4 is a solid-solid phase reactionIs prepared from silver nitrate (AgNO) 30-85 g/L 3 ) Firstly, 10-30 g/L sodium chloride (NaCl) is added into the solution to form silver chloride (AgCl) floccule, 10% dilute sulphuric acid is used for adjusting the PH of the floccule to be = 2-3, the stirring speed is 300-500 rpm, the replacement reaction temperature is 30-50 ℃, and silver nitrate (AgNO) is added into the floccule 3 ) Preferably 52g/L, and gradually and slowly adding, preferably 18g/L sodium chloride (NaCl), preferably 2 pH value, preferably 450rpm stirring speed, and preferably 40 deg.C reaction temperature;
the chemical reaction process of silver chloride (AgCl) floccule configuration is as follows:
AgNO 3 +NaCl＝AgCl↓+NaNO 3
because the metal activity of Zn is far higher than that of Ag, and the activity of hydrogen (H) is higher than that of Ag, zn can substitute Ag in AgCl suspension to precipitate Ag without releasing hydrogen (H) 2 ) The chemical reaction process comprises the following steps:
2AgCl↓+Zn＝2Ag+ZnCl 2 。
the invention has the beneficial effects that: the silver-coated aluminum powder prepared by the invention has excellent binding force and conductivity between silver and aluminum interfaces due to the existence of the pre-plated thin zinc layer; the silver-coated aluminum powder prepared by the invention has excellent shearing resistance and extrusion performance and excellent conductivity when being mixed with rubber.
Drawings
The invention is further illustrated by the non-limiting examples given in the accompanying drawings;
FIG. 1 is a flow chart of the process for preparing silver-coated aluminum powder according to the present invention;
FIG. 2 is an image of 20wt% of silver-coated aluminum powder with a medium particle size (40 um) prepared by the present invention at a magnification of 100;
FIG. 3 is an image of 20wt% of silver-coated aluminum powder with a medium particle size (40 um) prepared by the present invention at a magnification of 1000.
Detailed Description
In order that those skilled in the art can better understand the present invention, the following technical solutions are further described with reference to the accompanying drawings and examples.
The first embodiment is as follows:
the preparation method of the spheroidal aluminum powder with the median particle size of 40um and the silver-coated aluminum powder with the zinc plating content of 5wt% and the silver plating content of 20wt% is as follows:
(1) Soaking 50g of aluminum powder in 100ml of NaOH solution with the concentration of 2% for 5min at room temperature, and cleaning the aluminum powder to be neutral by using deionized water;
(2) The aluminum powder is immersed into 100ml of alkaline solution mixture prepared according to the mass percent, and the proportioning method comprises the following steps: naOH: potassium sodium tartrate: water =6, the soaking temperature is 25 ℃, the soaking time is 25min, and the cleaning is neutral after finishing the light finishing and etching;
(3) Adding the powder into 300ml of zinc plating solution, slowly stirring at 21 ℃ for 35s at the speed of 100rpm, quickly filtering, and cleaning to be neutral for later use, wherein the zinc plating solution comprises 8g/L of zinc oxide (ZnO), 65g/L of sodium hydroxide (NaOH), and nickel sulfate (NiSO) 4 ) 22g/L, sodium citrate (C) 6 H 5 Na 3 O 7 ) 12g/L and 86g/L of complexing agent (EDTA);
(4) The powder was added to 250ml of silver chloride (AgCl) suspension with 18g/L sodium chloride (NaCl) and silver nitrate (AgNO) to carry out a solid phase displacement reaction 3 ) 52g/L, PH = 2-3, stirring speed 450rpm, reaction temperature 40 ℃, and after the floccule completely disappears, cleaning, filtering and drying are carried out, thus obtaining the prepared silver-coated aluminum powder with 20% silver content, and the appearance is shown in figures 2 and 3.
Example two:
the preparation method of the silver-coated aluminum powder with the medium particle size of 40um and the zinc plating content of 4wt% and the silver plating content of 20wt% in the embodiment comprises the following steps:
the procedure of examples one (1), (2) and (4) was followed, and the ZnO concentration in (3) was changed to 6.4g/L, and the rest was unchanged.
Example three:
the preparation method of the sphere-like aluminum powder with the median particle size of 40um and the silver-coated aluminum powder with the silver coating content of 5wt% and 15wt% comprises the following steps:
the procedure of examples one (1), (2) and (3) was followed, and the silver nitrate concentration in (4) was changed to 40g/L, and the rest was unchanged.
The performance indexes of the silver-coated aluminum powder under the three examples are as follows:
TABLE 1 performance index of silver-coated aluminum powder in examples
The foregoing embodiments are merely illustrative of the principles of the present invention and its efficacy, and are not to be construed as limiting the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (6)
1. A preparation method of silver-coated aluminum powder for electromagnetic shielding material conductive rubber is characterized by comprising the following steps: aluminum powder with the particle size of 10-100 um is subjected to surface oil removal, surface finishing modification, zinc plating and silver plating, and then is washed, filtered and dried to obtain silver-coated aluminum powder, wherein the preparation process comprises the following steps:
(1) Selecting 10-100 um aluminum powder, performing surface degreasing and oxide film treatment for 3-10 min by adopting alkaline solution at room temperature, and cleaning and performing suction filtration for later use;
(2) In order to reduce the specific surface area of the aluminum powder and improve the thickness and the conductivity of the silver coating, the aluminum powder after being degreased and oxidized is immersed into strong alkaline solution, surface finishing modification is carried out for 20-60 min at normal temperature, and cleaning and suction filtration are carried out for standby;
(3) Putting the aluminum powder with the polished and modified surface into a zinc plating solution at 15-25 ℃, stirring for 30-60 s, cleaning, and carrying out suction filtration for later use;
(4) And stirring the galvanized aluminum powder at 30-50 ℃ under the acidic condition that the pH is = 2-3 to generate displacement chemical silvering until silver floccules in the solution completely disappear, and cleaning, filtering, and drying to obtain a finished product.
2. The method for preparing the silver-coated aluminum powder for the conductive rubber of the electromagnetic shielding material according to claim 1, characterized in that: the aluminum powder is spherical-like and has a particle size of 10-100 um, wherein 10-20 um is a fine particle size, 20-60 um is a medium particle size, and 60-100 um is a coarse particle size.
3. The method for preparing the silver-coated aluminum powder for the conductive rubber of the electromagnetic shielding material according to claim 1, wherein the method comprises the following steps: when the surface is deoiled, the alkali adopted by the alkaline solution is NaOH or KOH, the prepared concentrated solution is 1% -5%, the optimal selection is 2%, the used temperature is room temperature, the optimal time is 5min, and the used cleaning solution is deionized water and is cleaned to be neutral.
4. The method for preparing the silver-coated aluminum powder for the conductive rubber of the electromagnetic shielding material according to claim 1, characterized in that: when the surface is polished and modified, the used strong alkaline solution is a mixture of NaOH, sodium potassium tartrate and water, and the mass percentage of the solution is as follows: potassium sodium tartrate: and (2) water = 6.
5. The method for preparing the silver-coated aluminum powder for the conductive rubber of the electromagnetic shielding material according to claim 1, wherein the method comprises the following steps: when the aluminum powder is galvanized, the galvanizing solution is prepared by 5-12 g/L of zinc oxide, 50-100 g/L of sodium hydroxide, 10-30 g/L of nickel sulfate, 9-14 g/L of sodium citrate and 20-120 g/L of complexing agent, wherein the zinc oxide (Zn) is 2 O) is preferably 8g/L, sodium hydroxide (NaOH) is preferably 65g/L, nickel sulfate (NiSO) 4 ) Preferably 22g/L, adding Ni 2+ Can be co-precipitated with zincInhibiting the growth of zinc, making the crystal nucleus growth speed greater than that of crystal grain growth speed, reducing the size of zinc crystal grain in the zinc-dipping layer, making the zinc-dipping layer thinner and finer, and being favorable to raising the binding force between the zinc-dipping layer and the basic binding force, sodium citrate (C) 6 H 5 Na 3 O 7 ) Preferably 12g/L, the complexing agent (EDTA) is preferably 86g/L, the temperature is 21 ℃, the time is preferably 35s, and the cleaning solution is deionized water and is cleaned to be neutral.
6. The method for preparing the silver-coated aluminum powder for the conductive rubber of the electromagnetic shielding material according to claim 1, characterized in that: silver plating refers to displacement chemical silver plating, and 30-85 g/L silver nitrate (AgNO) is added by adopting solid-solid phase reaction 3 ) Firstly, 10-30 g/L sodium chloride (NaCl) is added into the solution to form silver chloride (AgCl) floccule, 10% dilute sulfuric acid is used for adjusting the pH of the floccule to be 2-3, the stirring speed is 300-500 rpm, the replacement reaction temperature is 30-50 ℃, and the silver nitrate (AgNO) is 3 ) Preferably 52g/L, and gradually slowly adding, preferably 18g/L sodium chloride (NaCl), preferably 2 pH, stirring speed preferably 450rpm, reaction temperature preferably 40 ℃.
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