A silver-coated glass microsphere material, its preparation method and application

Abstract

The present invention provides a silver-coated glass microsphere material, a preparation method thereof and an application thereof. The preparation method comprises the following steps: performing degreasing treatment on glass microspheres; performing roughening treatment on the glass microspheres with a hot alkali solution, then washing and drying; the hot alkali solution is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution, and the temperature is 40-70 °C; adding the processed glass microspheres into a mixed solution of an alcohol solvent and an organic amine, then adding Ag2O powder, and carrying out stirring reaction at a temperature of 20-130 °C for 0.5-4 hours; wherein, the mass ratio of the glass microspheres, the alcohol solvent and the organic amine is 1:2-5:1-3; filtering, washing with absolute ethanol until clean, and then performing vacuum drying to obtain the silver-coated glass microsphere material. The technical solution of the present invention has a short process flow, energy conservation and consumption reduction, obvious benefits, low cost, and the silver layer is uniformly and completely coated, the surface coating rate of the glass microspheres is high, and it has better electrical conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, relates to a conductive filler for electromagnetic shielding materials, and particularly relates to a silver-coated glass microsphere material, a preparation method thereof and an application thereof. Background Art

[0002] Using electromagnetic shielding materials is an effective means to purify the electromagnetic environment. Among them, conductive polymer materials prepared by adding conductive fillers to a polymer matrix have been widely used due to their low density and easy processing characteristics. Commonly used silver and silver-coated copper powders have excellent electrical conductivity and oxidation resistance, and are ideal conductive fillers for electromagnetic shielding materials. However, due to their high density and high cost, they are prone to sedimentation and stratification when added to the resin matrix, which limits their use and popularization.

[0003] Silver-coated glass microspheres not only have the advantages of good chemical stability and high electrical conductivity of metallic silver powder, but also combine the advantages of low density and low price of glass spheres. The silver-coated glass microspheres prepared by compounding the two can significantly reduce the cost and the density of the conductive filler, and are ideal lightweight composite fillers to replace silver and silver-coated copper conductive fillers, which can well solve the sedimentation problem of metal powders in conductive polymer composites and reduce the material cost.

[0004] Silver-coated glass microspheres are usually prepared by electroless plating. The traditional electroless plating process flow includes: degreasing → roughening → sensitizing → activating → electroless silver plating → washing → drying processes. HF solution is required for roughening, SnCl2 solution is required for sensitizing, and PdCl2 solution is required for activating. The entire silver plating process flow is long, the steps are cumbersome, the cost is high, and toxic reagents are required, generating a large amount of toxic and harmful wastewater, which does not meet the requirements of low-carbon development and green production. Summary of the Invention

[0005] In view of the above technical problems, the present invention discloses a silver-coated glass microsphere material, a preparation method thereof and an application thereof, which solve the problems of long process flow, cumbersome steps, high cost and generation of a large amount of toxic and harmful wastewater in the traditional electroless silver plating process. The preparation process of the silver-coated glass microspheres of the present invention only has three processes: degreasing, roughening and silver plating, and the process is simple; fluorine-containing roughening solution and strong acid solution are not used, reducing toxic and harmful wastewater; sensitizing and activating treatment steps are not required, reducing the cost; and under the condition of the same silver content, compared with the traditional electroless silver plating process, the silver-coated glass microspheres prepared by the present invention have better electrical conductivity.

[0006] For this reason, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a silver-coated glass microsphere material, comprising the following steps:

[0008] Step S1, perform degreasing treatment on the glass microspheres;

[0009] Step S2, roughening the glass microspheres with hot alkali solution, and then washing and drying them; the hot alkali solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, and the temperature is 40-70° C.;

[0010] Step S3, adding the glass microspheres obtained in step S2 to a mixed solution of an alcohol solvent and an organic amine, and then adding Ag2O powder, stirring and reacting at a temperature of 20 to 130° C. for 0.5 to 4 hours to obtain a solution containing silver-plated glass microspheres; wherein the mass ratio of the glass microspheres, the alcohol solvent and the organic amine is 1:2 to 5:1 to 3;

[0011] Step S4, filtering the solution containing the silver-coated glass microspheres, washing with anhydrous ethanol, and vacuum drying to obtain a silver-coated glass microsphere material.

[0012] Among them, in step S2, under heating conditions, the sodium hydroxide aqueous solution or potassium hydroxide aqueous solution can react with SiO2 in the glass microspheres to generate water-soluble silicates, which corrode the surface of the glass microspheres to achieve the effect of roughening the surface. In step S3, Ag2O can be reduced by alcohol solvents under the catalytic action of organic amines to generate metallic Ag, which is deposited on the roughened surface of the glass microspheres to achieve chemical silver plating.

[0013] Conventional chemical silver plating mostly uses silver ammonia solution as the supplier of metallic silver, and it is necessary to add reducing agents such as ascorbic acid and glucose, and use the reducing agent to reduce silver ions to obtain silver element to achieve silver plating. There is environmental pollution caused by ammonia volatilization and health hazards to operators, as well as a large amount of ammonia-containing wastewater. In addition, the silver ammonia solution with excessive ammonia mixed with organic reducing substances (or because the temperature is too high) will react to produce explosive silver fulminate. Similarly, the long-standing silver ammonia solution will precipitate extremely unstable and explosive silver azide (AgN3), silver nitride (Ag3N), and silver imide (Ag2NH) precipitation, resulting in a slight careless operation during the silver plating process, which is easy to cause an explosion and has a large safety hazard.

[0014] By adopting the technical scheme of the present invention, there is no need for sensitization, activation and other steps, the process flow is short, the steps are simple, and in particular, the explosion safety hazard of using silver ammonia complexes is avoided; there is no need to use strong acids and toxic and harmful reagents containing fluorine, and a large amount of toxic and harmful wastewater will not be generated, the operation is safe and more environmentally friendly; there is no need to use expensive SnCl2 and PdCl2 solutions, and the cost is lower; and the surface of the obtained silver-coated glass microspheres is evenly and completely coated, the conductivity is high, and the powder resistance is low.

[0015] As a further improvement of the present invention, the median particle size of the glass microspheres is 20-80 microns.

[0016] As a further improvement of the present invention, the alcohol solvent is one or a mixture of at least two of ethylene glycol, glycerol, n-butanol, octanol, isobutanol, and terpineol; the organic amine is one or a mixture of at least two of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-hexylamine, cyclohexylamine, hexamethylenediamine, propionamide, etc.

[0017] As a further improvement of the present invention, in step S1, commercially available dishwashing liquid is used to degrease the glass microspheres, and then they are washed.

[0018] As a further improvement of the present invention, in step S1, the glass microspheres are added to a container, and pure water and dishwashing liquid are added, and stirring treatment is carried out for 15 - 40 min in an ultrasonic environment; then they are filtered and washed with pure water.

[0019] As a further improvement of the present invention, the addition amount of the pure water is 10 - 50 times the mass of the glass microspheres, and the addition amount of the dishwashing liquid is 0.01 - 0.1 times the mass of the glass microspheres.

[0020] As a further improvement of the present invention, the stirring speed is 200 - 600 rpm.

[0021] As a further improvement of the present invention, the frequency of the ultrasonic bath is 30 - 60 KHz, and the power is 800 - 1000 W. Further, the frequency of the ultrasonic bath is 40 KHz, and the power is 900 W.

[0022] As a further improvement of the present invention, in step S2, the hot alkaline solution is an aqueous NaOH solution, and the mass percentage concentration of the aqueous NaOH solution is 10 - 30%.

[0023] As a further improvement of the present invention, in step S2, the glass microspheres obtained in step S1 are added to the aqueous NaOH solution, heated to 40 - 70 °C, and subjected to ultrasonic stirring treatment for 20 - 60 minutes, then filtered, washed with pure water until the pH value is neutral, and then dried.

[0024] As a further improvement of the present invention, in step S3, the mass of Ag2O is 0.1 - 0.6 times the mass of the glass microspheres, and the temperature condition is 20 - 130 °C. Further, the mass of Ag2O is 0.2 - 0.6 times the mass of the glass microspheres.

[0025] The present invention discloses a silver-coated glass microsphere material, which is prepared by using the preparation method of the silver-coated glass microsphere material as described above. Compared with the traditional silver plating process, at the same silver content, the surface coating of the obtained silver-coated glass microsphere material is complete and uniform, and has better electrical conductivity.

[0026] The present invention discloses the application of the silver-coated glass microsphere material as described above, and the silver-coated glass microsphere material is used as a conductive filler for a shielding material.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] First, compared with the traditional electroless silver plating process, the technical solution of the present invention only has three processes: degreasing, roughening, and silver plating. The process flow is short, energy is saved and consumption is reduced, and the benefits are obvious. Moreover, commercially available dishwashing liquid is used for degreasing, and hot alkaline solution is used for roughening. No solution containing HF is used, no toxic and harmful wastewater is generated, and no high-price SnCl2 and PdCl2 reagents are used, so the cost reduction advantage is obvious.

[0029] Second, by adopting the technical solution of the present invention, the silver layer is uniformly and completely coated, and the surface coating rate of the glass microspheres is high. The surface silver plating layer of the obtained silver-coated glass microsphere material is completely and uniformly coated. Compared with the traditional silver plating process, under the condition of the same silver content, the technical solution of the present invention has better conductivity. Description of the Drawings

[0030] Figure 1 is a scanning electron microscope photograph of the silver-coated glass microsphere powder obtained in Example 1 of the present invention.

[0031] Figure 2 is an XRD pattern of the silver-coated glass microsphere powder obtained in Examples 1 to 4 of the present invention.

[0032] Figure 3 is a scanning electron microscope photograph of the silver-coated glass microsphere powder obtained in Example 5 of the present invention.

[0033] Figure 4 is a scanning electron microscope photograph of the silver-coated glass microsphere powder obtained in Example 6 of the present invention, and the upper left corner is a partial enlarged view.

[0034] Figure 5 is a scanning electron microscope photograph of the silver-coated glass microsphere powder obtained in Comparative Example 1 of the present invention, and the upper left corner is a partial enlarged view. Detailed Embodiments

[0035] The following further elaborates on the preferred embodiments of the present invention.

[0036] A preparation method of a silver-coated glass microsphere material, the process flow thereof includes: degreasing → roughening → electroless silver plating → washing and drying processes, and the specific steps are as follows:

[0037] Step S1: Add glass microspheres into a three-necked flask placed in an ultrasonic bath. Add pure water and an appropriate amount of commercially available dishwashing liquid. Start stirring and ultrasonic treatment for 15 - 40 minutes, then filter and wash with pure water 3 - 5 times. The addition amount of pure water is 10 - 50 times the mass of the glass microspheres. The commercially available dishwashing liquid is mainly composed of sodium alkyl sulfonate and fatty alcohol polyoxyethylene sulfate, and the addition amount is 0.01 - 0.1 times the mass of the glass microspheres. The stirring speed is 200 - 600 rpm; the frequency of the ultrasonic bath is 40 KHz and the power is 900 W. Among them, the median particle size of the glass microspheres is 20 - 80 microns.

[0038] Step S2: Add the glass microspheres obtained in Step S1 into an aqueous NaOH solution and heat to 40 - 70 °C. Perform ultrasonic stirring treatment for 20 - 60 minutes, then filter and wash with pure water until the pH value is neutral, and then place it in an 80 °C oven for drying for standby. The mass percentage concentration of the aqueous NaOH solution is 10 - 30%.

[0039] Step S3: Add the glass microspheres obtained in Step S2 into a mixed solution of alcohol and organic amine, and then add 0.1 - 0.6 times the mass of the glass microspheres of Ag2O powder. After heating to 20 - 130 °C, stir and react for 0.5 - 4 hours. The alcohol is a mixture of one or more of ethylene glycol, glycerol, n-butanol, octanol, isobutanol, terpineol, etc.; the organic amine is a mixture of one or more of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-hexylamine, cyclohexylamine, hexamethylenediamine, propionamide, etc.; the mass ratio of glass microspheres, alcohol and organic amine is 1:2 - 5:1 - 3.

[0040] Step S4: Filter the silver-coated glass microspheres prepared by the reaction in Step S3, wash them clean with absolute ethanol, and then place them in a 65 °C vacuum oven for drying to obtain silver-coated glass microsphere powder.

[0041] The following is illustrated with specific examples.

[0042] Example 1

[0043] Step S1: Pour 50 g of glass microspheres into a three-necked flask placed in an ultrasonic bath, add 1500 g of pure water and 3 g of commercially available dishwashing liquid. Start stirring at a speed of 450 rpm and ultrasonic treatment for 30 minutes, then filter and wash with pure water 3 - 5 times.

[0044] Step S2: Add the glass microspheres obtained in Step S1 into an aqueous NaOH solution with a mass percentage concentration of 15%, heat to 55 °C, perform ultrasonic stirring treatment for 50 minutes, then filter and wash with pure water until the pH value is neutral, and then place it in an 80 °C oven for drying for standby.

[0045] Step S3: Add the glass microspheres obtained in Step S2 into a mixed solution of 150 g of n-butanol and 75 g of isopropanolamine, then add 25 g of Ag2O powder, heat up to 30 °C, and stir for reaction for 2 hours.

[0046] Step S4: Filter the silver-coated glass microspheres prepared in Step S3, wash them clean with absolute ethanol, and then place them in a vacuum oven at 75 °C for drying to obtain silver-coated glass microsphere powder.

[0047] The scanning electron microscope photograph of the silver-coated glass microspheres prepared in this example is as Figure 1 shown. It can be seen that the silver layer is uniformly and completely coated, and the surface coating rate of the glass microspheres is relatively high.

[0048] Example 2

[0049] Based on Example 1, the difference in this example is that the reaction temperature in Step S3 is 20 °C and the stirring time is 2 hours.

[0050] Example 3

[0051] Based on Example 1, the difference in this example is that the reaction temperature in Step S3 is 25 °C and the stirring time is 2 hours.

[0052] Example 4

[0053] Based on Example 1, the difference in this example is that the reaction temperature in Step S3 is 35 °C and the stirring time is 2 hours.

[0054] The XRD patterns of the silver-coated glass microspheres prepared at different reaction temperatures in Examples 1 to 4 are as Figure 2 shown. It can be seen that there are only diffraction peaks of metallic silver, indicating that the coated silver layer is uniform and has a certain thickness. In addition, from the intensity of the diffraction peaks, it can be seen that the temperature has a greater impact on the silver plating effect. The higher the reaction temperature, the greater the corresponding intensity of the diffraction peaks. Among them, 30 °C is the best.

[0055] For the silver-coated glass microspheres prepared at different reaction temperatures in Examples 1 to 4, the powder resistance was measured at different pressures using an ST2722-SD type semiconductor powder resistivity tester. The results are shown in Table 1. It can be seen that the reaction temperature has a greater impact on the powder resistance. As the reaction temperature increases, the powder resistance decreases.

[0056] Table 1 Powder resistance of silver-coated glass microspheres prepared at different reaction temperatures

[0057]

[0058] Example 5

[0059] Step S1: Pour 50 g of glass microspheres into a three-necked flask placed in an ultrasonic bath, add 1000 g of pure water and 2 g of commercially available dishwashing liquid, turn on the stirring speed to 350 rpm and perform ultrasonic treatment for 25 minutes, then filter and wash with pure water 3 - 5 times.

[0060] Step S2: Add the glass microspheres obtained in Step S1 to a 10% mass concentration NaOH aqueous solution, heat to 50 °C, perform ultrasonic stirring treatment for 40 minutes, then filter and wash with pure water until the pH value is neutral, and then place in an 80 °C oven for drying for later use.

[0061] Step S3: Add the glass microspheres obtained in Step S2 to a mixed solution of 200 g of terpineol and 100 g of n-hexylamine, add 10 g of Ag2O powder, heat to 130 °C, and then stir and react for 3 hours.

[0062] Step S4: Filter the silver-coated glass microspheres prepared in Step S3, wash them clean with absolute ethanol, and then place them in an 80 °C vacuum oven for drying to obtain silver-coated glass microsphere powder.

[0063] The scanning electron microscope images of the obtained silver-coated glass microsphere powder are as Figure 3 shown, it can be seen that the silver layer is uniformly and completely coated, and the surface coating rate of the glass microspheres is relatively high.

[0064] Example 6

[0065] Step S1: Pour 50 g of glass microspheres into a three-necked flask placed in an ultrasonic bath, add 2000 g of pure water and 4 g of commercially available dishwashing liquid, turn on the stirring speed to 550 rpm and perform ultrasonic treatment for 40 minutes, then filter and wash with pure water 3 - 5 times.

[0066] Step S2: Add the glass microspheres obtained in Step S1 to a 12% mass concentration NaOH aqueous solution, heat to 60 °C, perform ultrasonic stirring treatment for 35 minutes, then filter and wash with pure water until the pH value is neutral, and then place in an 80 °C oven for drying for later use.

[0067] Step S3: Add the glass microspheres obtained in Step S2 to a mixed solution of 220 g of isobutanol and 110 g of diethanolamine, add 30 g of Ag2O powder, heat to 45 °C, and then stir and react for 2.5 hours.

[0068] Step S4: Filter the silver-coated glass microspheres prepared in Step S3, wash them clean with absolute ethanol, and then place them in an 80 °C vacuum oven for drying to obtain silver-coated glass microsphere powder.

[0069] The scanning electron microscope images of the obtained silver-coated glass microsphere powder are as Figure 4As shown, it can be seen that the silver layer is uniformly and completely coated, and the coating rate on the surface of the glass microspheres is relatively high.

[0070] Comparative Example 1

[0071] As a comparison, according to the same silver content as in Example 1, a traditional electroless plating process flow is adopted, including degreasing → coarsening → sensitization → activation → electroless silver plating → washing → drying processes. The specific operations are as follows:

[0072] Take an appropriate amount of hollow glass microspheres and place them in a three-necked flask. Add hot alkaline solution and ultrasonically stir for 20 minutes at 50 °C for degreasing; after suction filtration and washing, put the degreased glass microspheres into a mixed solution of ammonium fluoride and hydrochloric acid and ultrasonically stir for 20 minutes at 40 °C for coarsening; then pour the glass microspheres that have been suction filtered and washed clean into a mixed hydrochloric acid solution of stannous chloride and sodium chloride for sensitization treatment. After ultrasonically stirring for 20 minutes, suction filter and wash clean; then add the sensitized glass microspheres into palladium chloride solution and ultrasonically activate for 15 minutes, then suction filter and dry; finally, place the activated glass microspheres in a three-necked flask containing glucose solution, start to slowly drip the freshly prepared silver ammonia solution, keep the temperature stable at 70 °C, and stir and react for one hour after dripping. After suction filtration, washing, and drying, silver-coated glass microspheres are obtained.

[0073] The scanning electron microscope photos of the prepared silver-coated glass microspheres are as Figure 5 shown. It can be seen that the surface of the glass microspheres is not completely coated, the silver plating layer is uneven, and there are many small silver particles mixed in it. While the silver layer of the silver-coated glass microspheres prepared in Example 1 is uniformly and densely coated and completely coated.

[0074] For this comparative example, a ST2722-SD type semiconductor powder resistivity tester is used to test the powder resistance at different pressures. The results are shown in Table 2. It can also be seen from the comparison of the powder resistance that under the same silver content, the conductivity of the silver-coated glass microspheres prepared in Comparative Example 1 is much lower than that of the silver-coated glass microspheres prepared in Example 1. This further illustrates the remarkable effect and outstanding conductivity advantage of the technical method proposed by the present invention.

[0075] Table 2 Powder resistance of silver-coated glass microspheres prepared in Example 1 and Comparative Example 1

[0076]

[0077] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a silver-coated glass microsphere material, characterized in that: It includes the following steps: Step S1, degreasing the glass microspheres; Step S2, roughening the glass microspheres with hot alkali solution, then washing and drying; the hot alkali solution is an aqueous solution of sodium hydroxide or potassium hydroxide, and the temperature is 40 - 70 °C; Step S3, adding the glass microspheres obtained in Step S2 into a mixed solution of an alcohol solvent and an organic amine, then adding Ag2O powder, and stirring and reacting at a temperature of 20 - 130 °C for 2 - 4 hours to obtain a solution containing silver-plated glass microspheres; wherein, the mass ratio of the glass microspheres, the alcohol solvent and the organic amine is 1:2 - 5:1 - 3; Step S4, filtering the solution containing silver-plated glass microspheres, washing it clean with absolute ethanol, and then performing vacuum drying to obtain silver-coated glass microsphere materials.

2. The preparation method of the silver-coated glass microsphere material according to claim 1, characterized in that: The alcohol solvent is one or a mixture of at least two of ethylene glycol, glycerol, n-butanol, octanol, isobutanol, and terpineol; the organic amine is one or a mixture of at least two of ethanolamine, diethanolamine, triethanolamine, isopropanolamine, n-hexylamine, cyclohexylamine, hexamethylenediamine, and propionamide.

3. The preparation method of the silver-coated glass microsphere material according to claim 2, characterized in that: In Step S1, the glass microspheres are degreased with commercially available dishwashing liquid and then washed.

4. The preparation method of the silver-coated glass microsphere material according to claim 3, characterized in that: In Step S1, the glass microspheres are added into a container, pure water and dishwashing liquid are added, and stirring treatment is carried out in an ultrasonic environment for 15 - 40 min; then filtered and washed with pure water.

5. The preparation method of the silver-coated glass microsphere material according to claim 4, characterized in that: The addition amount of the pure water is 10 - 50 times the mass of the glass microspheres, the addition amount of the dishwashing liquid is 0.01 - 0.1 times the mass of the glass microspheres; the rotation speed of the stirring is 200 - 600 rpm; the ultrasonic frequency of the ultrasonic environment is 30 - 60 KHz, and the power is 800 - 1000 W.

6. The preparation method of the silver-coated glass microsphere material according to claim 4, characterized in that: In Step S2, the hot alkali solution is an aqueous solution of NaOH, and the mass percentage concentration of the aqueous solution of NaOH is 10 - 30%.

7. The preparation method of the silver-coated glass microsphere material according to claim 6, characterized in that: In Step S2, the glass microspheres obtained in Step S1 are added into the aqueous solution of NaOH, heated to 40 - 70 °C, and subjected to ultrasonic stirring treatment for 20 - 60 minutes, then filtered, washed with pure water until the pH value is neutral, and then dried.

8. The preparation method of the silver-coated glass microsphere material according to claim 1, characterized in that: In Step S3, the mass of Ag2O is 0.2 - 0.6 times the mass of the glass microspheres, the temperature condition is 20 - 130 °C; the median particle size of the glass microspheres is 20 - 80 microns.

9. A silver-coated glass microsphere material, characterized in that: It is prepared by using the preparation method of the silver-coated glass microsphere material according to any one of claims 1 - 8.

10. The application of the silver-coated glass microsphere material according to claim 9, wherein: The silver-coated glass microsphere material is used as a conductive filler for a shielding material.

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