Modification method for improving surface activity of spherical silica powder based on alkali treatment

Abstract

The invention discloses a modification method for improving the surface activity of spherical silica powder based on alkali treatment, relates to the technical field of surface modification, and comprises a modification method for alkali-treated spherical silica powder. The modification method for improving the surface activity of the spherical silica powder based on alkali treatment comprises the steps of raw material pretreatment, alkali solution preparation, alkali treatment, cleaning and drying, the alkali treatment comprises gradient heating treatment and ultrasonic synergistic treatment, and magnetic field assisted ultrasonic cleaning is matched with hydrogen peroxide solution surface activation, so that impurities can be removed, and the surface activity of the spherical silica powder can be improved. Meanwhile, active groups can be introduced in advance, in the alkali treatment process, gradient heating treatment enables the surface reaction of the micro powder to be more uniform, ultrasonic synergistic treatment enhances the mass transfer efficiency and generates active groups such as hydroxyl, and compared with a traditional method, the surface activity can be effectively improved, and a foundation is laid for improving the compatibility with an organic matrix; residual metal ions are effectively removed by using a chelating agent to assist cleaning and using an ethylenediamine tetraacetic acid solution, and washing is more thorough compared with conventional washing.

Description

Technical Field

[0001] The present invention relates to the technical field of surface modification, in particular to a modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment. Background Art

[0002] Spherical silica powder is an inorganic non-metallic material with high hardness, low dielectric constant and thermal expansion coefficient. Due to its excellent physical and chemical properties, it is widely used in electronic packaging, special ceramics, coatings and other fields. In the electronic packaging industry, spherical silica powder is added as a filler to the epoxy resin matrix to effectively reduce the thermal expansion coefficient of the material, improve heat dissipation performance and mechanical strength, and enhance product reliability.

[0003] As a simple, efficient, and low-cost surface modification method, alkali treatment has unique advantages in the field of material surface treatment. Alkaline solution can chemically react with the silicon-oxygen bonds on the surface of spherical silica powder, etching the surface structure and introducing a large number of active groups such as hydroxyl groups, thereby significantly improving its surface activity.

[0004] Spherical silicon micropowder is widely used in electronic packaging, special ceramics, coatings and other fields due to its excellent properties such as high hardness, low dielectric constant and thermal expansion coefficient. It is especially important for improving product reliability in the electronic packaging industry. However, its surface chemical inertness leads to poor compatibility with organic matrices, which limits its performance. Existing modification methods such as coupling agent modification and surfactant treatment have problems such as unstable modification effect, high cost and complex process. Although alkali treatment has the potential to improve the surface activity of materials, the research on alkali treatment modification of spherical silicon micropowder is still incomplete, lacking process parameter optimization and in-depth exploration of the mechanism of changes in surface structure and active groups. In order to solve the key problems in the application of spherical silicon micropowder and optimize the alkali treatment process, we propose a modification method based on alkali treatment to improve the surface activity of spherical silicon micropowder. Summary of the Invention

[0005] The purpose of the present invention is to provide a modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment, including a modification method for spherical silicon micropowder treated with alkali, wherein the modification operation for improving the surface activity of spherical silicon micropowder based on alkali treatment includes raw material pretreatment, alkali solution preparation, alkali treatment, cleaning and drying, wherein the alkali treatment includes gradient temperature treatment and ultrasonic synergistic treatment, and the specific operation steps of the modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment are as follows:

[0007] Step 1: Spherical silicon micropowder is placed in an ultrasonic container filled with deionized water, and an alternating magnetic field is applied to clean the spherical silicon micropowder. After cleaning, the spherical silicon micropowder is subjected to surface activation treatment to obtain pretreated spherical silicon micropowder;

[0008] Step 2: Potassium hydroxide is selected as the alkaline reagent to prepare an alkaline solution. During the preparation process, nitrogen is introduced into the solution. The alkaline solution is stirred evenly and then stored for later use.

[0009] Step 3: adding the pretreated spherical silicon powder to the alkaline solution, pre-stirring, heating and stirring until fully dispersed, and turning on an ultrasonic device to perform ultrasonic treatment during the stirring process to obtain a mixed solution;

[0010] Step 4: Transfer the mixed solution into a centrifuge for centrifugal separation to obtain micropowder, wash it with deionized water after separation, and then soak the micropowder in ethylenediaminetetraacetic acid solution for washing, and then repeatedly wash it with deionized water for use;

[0011] Step 5: Soak the cleaned micropowder in an ethanol solution containing a silane coupling agent, and then transfer it to a vacuum drying oven for vacuum drying to obtain modified spherical silicon micropowder.

[0012] As a further solution of the present invention: in the step 1, spherical silicon micropowder with an average particle size of 5um-15um and a purity of ≥99% is selected, placed in a container containing deionized water, and an alternating magnetic field with a frequency of 20kHz-40kHz and an intensity of 0.1T-0.3T is applied to the outside of the container, and ultrasonic cleaning is performed for 15min-30min to remove impurities on the surface of the spherical silicon micropowder and store it for future use.

[0013] As a further embodiment of the present invention, in step 1, the spherical silicon micropowder after impurity removal is transferred to a hydrogen peroxide solution with a mass fraction of 0.5% to 2% and soaked for 10 to 20 minutes. After soaking, the spherical silicon micropowder is filtered twice, and the filtered micropowder is dried at a temperature of 80° C. to 100° C. for 4 to 6 hours to obtain pretreated spherical silicon micropowder.

[0014] As a further solution of the present invention: in the step 2, potassium hydroxide is selected as the alkaline reagent, and deionized water with a total volume of 80% is added to the beaker containing the alkaline reagent, and stirred with a magnetic stirrer, and the stirring speed is set to 300r / min-400r / min, and the stirring temperature is 40°C-50°C. The alkaline solution with a concentration of 0.5mol / L-3mol / L is stirred, and after the preparation is completed, it is transferred to a reaction vessel with a sealing plug and a gas inlet and outlet, and nitrogen is introduced into the inlet. The nitrogen flow rate is controlled at 50mL / min-70mL / min, and the ventilation time lasts for 10min-15min to discharge oxygen in the alkaline solution. After the ventilation is completed, the container is sealed and stored for standby use.

[0015] As a further scheme of the present invention: in the step three, the pretreated spherical silicon powder is added to the alkaline solution at a solid-liquid ratio of 1:10-15, pre-stirred for 10min-15min at a temperature of 20℃-30℃, stirred until the powder is fully dispersed in the solution, and then the temperature is raised to 55℃-70℃ at a heating rate of 2℃ / min-5℃ / min. At this temperature, the reaction is stirred at a stirring speed of 250r / min-300r / min for 1.5h-3h, and the reactor is subjected to ultrasonic co-treatment during the stirring process.

[0016] As a further solution of the present invention: in step three, the reactor containing the reaction system is placed in an ultrasonic cleaning machine, the ultrasonic device is turned on, the ultrasonic frequency is set to 45kHz-60kHz, and the power is 100W-300W, and a mixed liquid is obtained after the treatment is completed.

[0017] As a further embodiment of the present invention: in the step 4, the mixed solution is transferred to a centrifuge tube, and centrifuged using a refrigerated centrifuge, the speed of the refrigerated centrifuge is set to 6000 r / min-7500 r / min, the centrifugation time is 5 min-10 min, and the centrifugation temperature is controlled at 4°C-10°C. After the centrifugation is completed, the supernatant is poured out, and the precipitated micropowder at the bottom is retained. Deionized water is added to the centrifuge tube containing the micropowder precipitate to 80% of the volume of the centrifuge tube, and the micropowder is initially washed with water using a vortex oscillator for 1 min-2 min, and the micropowder is dispersed in deionized water. The centrifuge tube is placed in a refrigerated centrifuge and centrifuged according to the above-mentioned centrifugation conditions, the supernatant is poured out, and this operation is repeated 2-3 times to obtain the washed micropowder.

[0018] As a further embodiment of the present invention: in the step 4, a 0.1% mass fraction of ethylenediaminetetraacetic acid solution is prepared, and the ethylenediaminetetraacetic acid solution is added to the centrifuge tube containing the micropowder using a pipette to immerse the micropowder in the ethylenediaminetetraacetic acid solution, and the centrifuge tube is placed in a constant temperature shaker, and the shaker speed is set to 150r / min-200r / min and the temperature is 25°C-30°C. Under these conditions, washing is performed for 5min-10min. After washing, the centrifuge tube is placed in a refrigerated centrifuge for centrifugal separation. The centrifugation conditions are the same as those for the preliminary water washing centrifugation. After the centrifugation is completed, the ethylenediaminetetraacetic acid solution is dumped, and deionized water is added to the centrifuge tube. The preliminary water washing operation is repeated 3-5 times until the pH value of the washing solution is 6.5-7.5, and the washing operation is terminated to obtain the cleaned micropowder.

[0019] As a further embodiment of the present invention: In step 5, ethanol is measured using a pipette to prepare an ethanol solution with a volume fraction of 50%-70%, γ-aminopropyltriethoxysilane with a concentration of 1% is added to the ethanol solution, and a magnetic stirrer is used to stir at a stirring speed of 300r / min-400r / min for 10min-15min until the γ-aminopropyltriethoxysilane is completely dissolved to prepare a surface modification solution, and the cleaned micropowder is added to a beaker containing the surface modification solution. , use plastic wrap to seal the beaker mouth, soak at a temperature of 25℃ for 45min-60min, shake the beaker gently every 10min, after soaking, pass the solution through a filtration device for solid-liquid separation, collect the powder, and transfer it to a vacuum drying oven, set the vacuum degree to -0.08MPa--0.1MPa, the drying temperature to 60℃-80℃, and the drying time to 6h-10h. After drying, cool the powder to 25℃ to obtain the modified spherical silicon powder, take it out and seal it for storage.

[0020] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The present invention uses magnetic field-assisted ultrasonic cleaning combined with hydrogen peroxide solution surface activation to not only remove impurities but also pre-introduce active groups. During the alkali treatment process, the gradient temperature treatment makes the surface reaction of the micropowder more uniform, and the ultrasonic synergistic treatment enhances the mass transfer efficiency, generating active groups such as hydroxyl groups. Compared with traditional methods, it can effectively improve the surface activity and lay the foundation for improving the compatibility with the organic matrix. By using a chelating agent to assist in cleaning, the ethylenediaminetetraacetic acid solution is used to effectively remove residual metal ions, which is more thorough than conventional water washing and improves the surface purity of the micropowder. An active molecular film is formed by surface modification and drying using a silane coupling agent. Combined with the large number of active groups introduced in the early treatment, the surface activity is further improved and the compatibility with the organic matrix is significantly improved. Compared with a single modification method, the interfacial bonding strength of the composite material is greatly enhanced.

[0022] 2. The present invention uses alkali treatment and supporting processes, with low raw material costs. The reagents used, such as sodium hydroxide, potassium hydroxide, and hydrogen peroxide, are all common chemicals. The process operation is simple, and no complex equipment and special conditions are required, which greatly reduces the modification cost and process complexity. It is more suitable for large-scale industrial applications. When the modified spherical silicon micropowder is used in fields such as electronic packaging, it can effectively solve the performance limitation problem of composite materials caused by insufficient surface activity. In the electronic packaging industry, adding it to the epoxy resin matrix can more significantly reduce the thermal expansion coefficient of the material, improve heat dissipation performance and mechanical strength, enhance product reliability, and provide reliable technical support for the preparation of high-performance materials in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart of the method for modifying the surface activity of spherical silicon powder in an embodiment of the present invention;

[0024] Figure 2 This is a comparison chart of performance test data of the modified spherical silicon powder in the examples of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0026] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Please see the attached Figure 1 -Attached Figure 2 The present invention provides a modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment, including a modification method for spherical silicon micropowder treated with alkali. The modification operation for improving the surface activity of spherical silicon micropowder based on alkali treatment includes raw material pretreatment, alkali solution preparation, alkali treatment, cleaning and drying. The alkali treatment includes gradient temperature treatment and ultrasonic synergistic treatment. The specific operation steps of the modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment are as follows:

[0028] Step 1: Spherical silicon micropowder is placed in an ultrasonic container filled with deionized water, and an alternating magnetic field is applied to clean the spherical silicon micropowder. After cleaning, the spherical silicon micropowder is subjected to surface activation treatment to obtain pretreated spherical silicon micropowder;

[0029] Step 2: Potassium hydroxide is selected as the alkaline reagent to prepare an alkaline solution. During the preparation process, nitrogen is introduced into the solution. The alkaline solution is stirred evenly and then stored for later use.

[0030] Step 3: adding the pretreated spherical silicon powder to the alkaline solution, pre-stirring, heating and stirring until fully dispersed, and turning on an ultrasonic device to perform ultrasonic treatment during the stirring process to obtain a mixed solution;

[0031] Step 4: Transfer the mixed solution into a centrifuge for centrifugal separation to obtain micropowder, wash it with deionized water after separation, and then soak the micropowder in ethylenediaminetetraacetic acid solution for washing, and then repeatedly wash it with deionized water for use;

[0032] Step 5: Soak the cleaned micropowder in an ethanol solution containing a silane coupling agent, and then transfer it to a vacuum drying oven for vacuum drying to obtain modified spherical silicon micropowder.

[0033] In one embodiment of the present invention: in step 1, spherical silicon micropowder with an average particle size of 5um-15um and a purity of ≥99% is selected, placed in a container containing deionized water, and an alternating magnetic field with a frequency of 20kHz-40kHz and an intensity of 0.1T-0.3T is applied to the outside of the container, and ultrasonic cleaning is performed for 15min-30min to remove impurities on the surface of the spherical silicon micropowder and store it for future use.

[0034] In one embodiment of the present invention, in step 1, the spherical silicon micropowder after impurity removal is transferred to a hydrogen peroxide solution with a mass fraction of 0.5% to 2% and soaked for 10 to 20 minutes. After soaking, it is filtered twice, and the filtered micropowder is dried at a temperature of 80° C. to 100° C. for 4 to 6 hours to obtain pretreated spherical silicon micropowder.

[0035] In one embodiment of the present invention: in step 2, potassium hydroxide is selected as the alkaline reagent, and deionized water with a total volume of 80% is added to the beaker containing the alkaline reagent, and stirred using a magnetic stirrer, and the stirring speed is set to 300r / min-400r / min, and the stirring temperature is 40°C-50°C. The alkaline solution with a concentration of 0.5mol / L-3mol / L is stirred and prepared. After the preparation is completed, it is transferred to a reaction vessel with a sealing plug and a gas inlet and outlet, and nitrogen is introduced into the inlet. The nitrogen flow rate is controlled at 50mL / min-70mL / min, and the ventilation time lasts for 10min-15min to discharge oxygen in the alkaline solution. After the ventilation is completed, the container is sealed and stored for standby use.

[0036] In one embodiment of the present invention: in step three, the pretreated spherical silicon powder is added to the alkaline solution at a solid-liquid ratio of 1:10-15, and pre-stirred for 10min-15min at a temperature of 20°C-30°C, and stirred until the powder is fully dispersed in the solution, and then the temperature is raised to 55°C-70°C at a heating rate of 2°C / min-5°C / min, and the reaction is stirred at this temperature at a stirring speed of 250r / min-300r / min for 1.5h-3h, and the reactor is subjected to ultrasonic co-treatment during the stirring process.

[0037] In one embodiment of the present invention: in step three, the reactor containing the reaction system is placed in an ultrasonic cleaning machine, the ultrasonic device is turned on, the ultrasonic frequency is set to 45kHz-60kHz, the power is 100W-300W, and a mixed liquid is obtained after the treatment is completed.

[0038] In one embodiment of the present invention: in step 4, the mixed solution is transferred to a centrifuge tube and centrifuged using a refrigerated centrifuge, the speed of the refrigerated centrifuge is set to 6000r / min-7500r / min, the centrifugation time is 5min-10min, and the centrifugation temperature is controlled at 4°C-10°C. After the centrifugation is completed, the supernatant is poured out, and the precipitated micropowder at the bottom is retained. Deionized water is added to the centrifuge tube containing the micropowder precipitate to 80% of the volume of the centrifuge tube, and a vortex oscillator is used to oscillate for 1min-2min for preliminary water washing, and the micropowder is dispersed in deionized water. The centrifuge tube is placed in a refrigerated centrifuge and centrifuged according to the above-mentioned centrifugation conditions, and the supernatant is poured out. This operation is repeated 2-3 times to obtain washed micropowder.

[0039] In one embodiment of the present invention: in step 4, a 0.1% mass fraction of ethylenediaminetetraacetic acid solution is prepared, and the ethylenediaminetetraacetic acid solution is added to the centrifuge tube containing the micropowder using a pipette to immerse the micropowder in the ethylenediaminetetraacetic acid solution, and the centrifuge tube is placed in a constant temperature shaker, the shaker speed is set to 150r / min-200r / min, and the temperature is 25°C-30°C. Under these conditions, washing is performed for 5min-10min. After washing, the centrifuge tube is placed in a refrigerated centrifuge for centrifugal separation. The centrifugation conditions are the same as those for the preliminary water washing centrifugation. After the centrifugation is completed, the ethylenediaminetetraacetic acid solution is dumped, and deionized water is added to the centrifuge tube. The preliminary water washing operation is repeated 3-5 times until the pH value of the washing solution is 6.5-7.5, and the washing operation is terminated to obtain the cleaned micropowder.

[0040] In one embodiment of the present invention, in step 5, ethanol is measured using a pipette to prepare an ethanol solution with a volume fraction of 50%-70%, γ-aminopropyltriethoxysilane with a concentration of 1% is added to the ethanol solution, and a magnetic stirrer is used to stir at a stirring speed of 300r / min-400r / min for 10min-15min until the γ-aminopropyltriethoxysilane is completely dissolved to prepare a surface modification solution, and the cleaned micropowder is added to a beaker containing the surface modification solution. , use plastic wrap to seal the beaker mouth, soak at a temperature of 25℃ for 45min-60min, shake the beaker gently every 10min, after soaking, pass the solution through a filtration device for solid-liquid separation, collect the powder, and transfer it to a vacuum drying oven, set the vacuum degree to -0.08MPa--0.1MPa, the drying temperature to 60℃-80℃, and the drying time to 6h-10h. After drying, cool the powder to 25℃ to obtain the modified spherical silicon powder, take it out and seal it for storage.

[0041] Example

[0042] 20 g of spherical silicon micropowder with an average particle size of 8 μm and a purity of 99.2% was selected and placed in an ultrasonic container filled with 200 mL of deionized water. An alternating magnetic field with a frequency of 25 kHz and an intensity of 0.2 T was applied to the outside of the container for ultrasonic cleaning for 20 min. After cleaning, the powder was transferred to a hydrogen peroxide solution with a mass fraction of 1% and soaked for 15 min. After soaking, it was filtered twice and dried at 90 ° C for 5 h to obtain pretreated spherical silicon micropowder. Potassium hydroxide was selected as an alkaline reagent, 14 g of potassium hydroxide was weighed and placed in a beaker, 80% (about 160 mL) of the total volume of deionized water was added, and a magnetic stirrer was used to stir at a stirring speed of 350 r / min and a stirring temperature of 45 ° C to prepare a concentration of 1.75 mo 1 / L of alkaline solution, transfer the alkaline solution into a reaction vessel with a sealing plug and a gas inlet and outlet, introduce nitrogen into the inlet, and control the nitrogen flow rate at 60mL / min for 12min. After the oxygen in the alkaline solution is discharged, seal the container and store it for future use;

[0043] The pretreated spherical silicon powder was added to the alkaline solution at a solid-liquid ratio of 1:12, and pre-stirred for 12 minutes at 25°C until the powder was fully dispersed in the solution. The temperature was then raised to 60°C at a heating rate of 3°C / min, and stirred at this temperature at a stirring speed of 280 r / min for 2 hours. During the stirring process, the reactor containing the reaction system was placed in an ultrasonic cleaning machine, and the ultrasonic device was turned on with the ultrasonic frequency set to 50 kHz and the power set to 200 W. After the treatment was completed, a mixed solution was obtained;

[0044] The mixed solution was transferred to a 50 mL centrifuge tube and centrifuged at 7000 r / min, 7 min and 6 ° C using a refrigerated centrifuge. The supernatant was poured out and the bottom precipitated powder was retained. Deionized water was added to the centrifuge tube containing the powder precipitate to 80% of the volume of the centrifuge tube. A vortex oscillator was used to oscillate for 1.5 min for preliminary water washing. The mixture was then centrifuged under the above centrifugal conditions. The supernatant was poured out and repeated twice. A 0.1% mass fraction of ethylenediaminetetraacetic acid solution was prepared and added to the centrifuge tube containing the powder so that the powder was immersed. The centrifuge tube was placed in a constant temperature shaker and washed at 180 r / min and 28 ° C for 8 min. After washing, the centrifuge was centrifuged under the above centrifugal conditions. The ethylenediaminetetraacetic acid solution was poured out and deionized water was added to the centrifuge tube. Repeat the initial water washing operation three times until the pH value of the washing solution is 7.0, use a pipette to measure ethanol, prepare a 60% volume fraction ethanol solution, add 1% γ-aminopropyltriethoxysilane to the ethanol solution, use a magnetic stirrer to stir at 350r / min for 12 minutes until it is completely dissolved to obtain a surface modification solution, add the cleaned micropowder to a beaker containing the surface modification solution, seal the beaker with plastic wrap, soak at 25°C for 50 minutes, shake the beaker gently every 10 minutes, and after soaking, pass the solution through a suction filtration device for solid-liquid separation, collect the micropowder, and transfer it to a vacuum drying oven, set the vacuum degree to -0.09MPa, the drying temperature to 70°C, and the drying time to 8h. After drying, cool the micropowder to 25°C to obtain modified spherical silicon micropowder.

[0045] The quality test of the modified spherical silicon micropowder was conducted, and the test samples were unmodified spherical silicon micropowder and the modified spherical silicon micropowder prepared in this example;

[0046] 1. Surface activity test,

[0047] Detection operation:

[0048] X-ray photoelectron spectroscopy (XPS) was used to examine the spherical silica powder before and after modification. After the sample was ground evenly, a small amount was placed on the sample stage and placed into the XPS chamber. Under vacuum conditions, a monochromatic AIKα X-ray source (energy 1486.6 eV) was used to excite the sample surface. The photoelectron spectrum was collected and analyzed, and the surface hydroxyl content was calculated by peak fitting.

[0049] Test data:

[0050] The surface hydroxyl content of unmodified spherical silica powder is 5.8%, while that of modified spherical silica powder is increased to 22.3%.

[0051] 2. Surface morphology detection,

[0052] Detection operation:

[0053] The surface morphology of the powder was observed using a scanning electron microscope (SEM). An appropriate amount of sample was placed on a conductive tape and sprayed with gold to enhance the conductivity of the sample. The treated sample was placed in the SEM sample chamber and the surface morphology of the powder was observed and photographed at an accelerating voltage of 15 kV and a magnification of 10,000 times.

[0054] Test data:

[0055] The surface of unmodified spherical silicon powder is relatively smooth, with a small amount of impurity particles attached. The surface of modified spherical silicon powder shows obvious etching marks, forming a large number of tiny pits and protrusions, which increases the specific surface area. The surface is clean and no obvious impurities remain.

[0056] 3. Particle size distribution detection,

[0057] Detection operation:

[0058] Use a laser particle size analyzer to measure the particle size distribution of the micropowder. Weigh 0.5g of sample, add 50mL of deionized water, and ultrasonically disperse for 10 minutes to evenly disperse the micropowder in the water. Pour the dispersed sample solution into the sample cell of the laser particle size analyzer, set the detection parameters, and perform the measurement. Repeat the measurement three times to obtain the average value.

[0059] Test data:

[0060] The average particle size of the unmodified spherical silica powder is 8.1um, and the particle size distribution range is relatively wide, with D10 (particle size corresponding to when the cumulative volume fraction reaches 10%) being 4.2um, D50 (median particle size) being 7.8um, and D90 (particle size corresponding to when the cumulative volume fraction reaches 90%) being 12.5um. The average particle size of the modified spherical silica powder is 7.9um, and the particle size distribution is more concentrated, with D10 being 5.0um, D50 being 7.7um, and D90 being 10.3um.

[0061] 4. Composite material performance testing,

[0062] Detection operation:

[0063] The spherical silica powders before and after modification were added to the epoxy resin matrix at a mass fraction of 50%, and a curing agent was added (mass ratio of epoxy resin: curing agent = 10:1). The mixture was stirred evenly at 60°C and vacuum degassed for 15 minutes. The mixture was poured into a mold and cured (80°C for 2 hours and 120°C for 4 hours). Composite material samples were prepared. According to relevant standards, the tensile strength and impact strength were tested using a universal material testing machine, and the thermal expansion coefficient was determined using a thermomechanical analyzer. The specific data are shown in the attached figure. Figure 2 As shown;

[0064] The examples and test data show that the composite material prepared from the modified spherical silicon powder has significantly improved properties such as tensile strength, impact strength and thermal expansion coefficient.

[0065] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A modification method for improving the surface activity of spherical silicon micropowder based on alkali treatment, comprising a modification method for spherical silicon micropowder by alkali treatment, characterized in that: The modification operation of improving the surface activity of spherical silicon micropowder based on alkali treatment includes raw material pretreatment, alkali solution preparation, alkali treatment, cleaning and drying. The alkali treatment includes gradient temperature treatment and ultrasonic synergistic treatment. The specific operation steps of the modification method of improving the surface activity of spherical silicon micropowder based on alkali treatment are as follows: Step 1: Spherical silicon micropowder is placed in an ultrasonic container filled with deionized water, and an alternating magnetic field is applied to clean the spherical silicon micropowder. After cleaning, the spherical silicon micropowder is subjected to surface activation treatment to obtain pretreated spherical silicon micropowder; Step 2: Potassium hydroxide is selected as the alkaline reagent to prepare an alkaline solution. During the preparation process, nitrogen is introduced into the solution. The alkaline solution is stirred evenly and then stored for later use. Step 3: adding the pretreated spherical silicon powder to the alkaline solution, pre-stirring, heating and stirring until fully dispersed, and turning on an ultrasonic device to perform ultrasonic treatment during the stirring process to obtain a mixed solution; Step 4: Transfer the mixed solution into a centrifuge for centrifugal separation to obtain micropowder, wash it with deionized water after separation, and then soak the micropowder in ethylenediaminetetraacetic acid solution for washing, and then repeatedly wash it with deionized water for use; Step 5: Soak the cleaned micropowder in an ethanol solution containing a silane coupling agent, and then transfer it to a vacuum drying oven for vacuum drying to obtain modified spherical silicon micropowder.

2. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 1, characterized in that: In the step 1, spherical silicon micropowder with an average particle size of 5 μm-15 μm and a purity of ≥99% is selected and placed in a container containing deionized water. An alternating magnetic field with a frequency of 20 kHz-40 kHz and an intensity of 0.1 T-0.3 T is applied to the outside of the container, and ultrasonic cleaning is performed for 15 min-30 min to remove impurities on the surface of the spherical silicon micropowder and store it for future use.

3. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 2, characterized in that: In the step 1, the spherical silicon micropowder after impurity removal is transferred to a hydrogen peroxide solution with a mass fraction of 0.5% to 2% and soaked for 10 minutes to 20 minutes. After soaking, it is filtered twice, and the filtered micropowder is dried at a temperature of 80° C. to 100° C. for 4 hours to 6 hours to obtain pretreated spherical silicon micropowder.

4. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 3, characterized in that: In the step 2, potassium hydroxide is selected as the alkaline reagent, and deionized water with a total volume of 80% is added to the beaker containing the alkaline reagent, and a magnetic stirrer is used for stirring. The stirring speed is set to 300r / min-400r / min, and the stirring temperature is 40°C-50°C. The alkaline solution with a concentration of 0.5mol / L-3mol / L is stirred and prepared. After the configuration is completed, it is transferred to a reaction vessel with a sealing plug and a gas inlet and outlet, and nitrogen is introduced into the inlet. The nitrogen flow rate is controlled at 50mL / min-70mL / min, and the ventilation time lasts for 10min-15min to discharge oxygen in the alkaline solution. After the ventilation is completed, the container is sealed and stored for standby use.

5. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 4, characterized in that: In the step three, the pretreated spherical silicon powder is added to the alkaline solution at a solid-liquid ratio of 1:10-15, pre-stirred for 10 min-15 min at a temperature of 20°C-30°C, stirred until the powder is fully dispersed in the solution, and then the temperature is raised to 55°C-70°C at a heating rate of 2°C / min-5°C / min. The reaction is stirred at this temperature at a stirring speed of 250 r / min-300 r / min for 1.5 h-3 h, and the reactor is subjected to ultrasonic co-treatment during the stirring process.

6. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 5, characterized in that: In the step 3, the reactor containing the reaction system is placed in an ultrasonic cleaning machine, the ultrasonic device is turned on, the ultrasonic frequency is set to 45kHz-60kHz, and the power is 100W-300W, and a mixed solution is obtained after the treatment is completed.

7. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 6, characterized in that: In the step 4, the mixed solution is transferred to a centrifuge tube and centrifuged using a refrigerated centrifuge, the speed of the refrigerated centrifuge is set to 6000r / min-7500r / min, the centrifugation time is 5min-10min, and the centrifugation temperature is controlled at 4°C-10°C. After the centrifugation is completed, the supernatant is poured out, and the bottom precipitated micropowder is retained. Deionized water is added to the centrifuge tube containing the micropowder precipitate to 80% of the volume of the centrifuge tube, and a vortex oscillator is used to oscillate for 1min-2min for preliminary water washing, and the micropowder is dispersed in deionized water. The centrifuge tube is placed in a refrigerated centrifuge and centrifuged according to the above centrifugation conditions. The supernatant is poured out, and this operation is repeated 2-3 times to obtain the washed micropowder.

8. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 7, characterized in that: In the step 4, a 0.1% mass fraction of ethylenediaminetetraacetic acid solution is prepared, and the ethylenediaminetetraacetic acid solution is added to the centrifuge tube containing the micropowder using a pipette to immerse the micropowder in the ethylenediaminetetraacetic acid solution. The centrifuge tube is placed in a constant temperature shaker, and the shaker speed is set to 150 r / min-200 r / min and the temperature is set to 25°C-30°C. Under these conditions, washing is performed for 5 min-10 min. After washing, the centrifuge tube is placed in a refrigerated centrifuge for centrifugal separation. The centrifugation conditions are the same as those for the preliminary water washing centrifugation. After the centrifugation is completed, the ethylenediaminetetraacetic acid solution is dumped, and deionized water is added to the centrifuge tube. The preliminary water washing operation is repeated 3-5 times until the pH value of the washing solution is 6.5-7.

5. The washing operation is terminated to obtain the cleaned micropowder.

9. The method for improving the surface activity of spherical silicon powder by alkali treatment according to claim 8, characterized in that: In the step 5, ethanol is measured using a pipette to prepare an ethanol solution with a volume fraction of 50%-70%, γ-aminopropyltriethoxysilane with a concentration of 1% is added to the ethanol solution, and a magnetic stirrer is used to stir at a stirring speed of 300r / min-400r / min for 10min-15min, until the γ-aminopropyltriethoxysilane is completely dissolved to obtain a surface modification solution, and the cleaned micropowder is added to a beaker containing the surface modification solution, the beaker mouth is sealed with plastic wrap, and the powder is soaked at a temperature of 25°C for 45min-60min, and the beaker is gently shaken every 10min. After the soaking is completed, the solution is passed through a suction filtration device for solid-liquid separation, the micropowder is collected, and transferred to a vacuum drying oven, the vacuum degree is set to -0.08MPa--0.1MPa, the drying temperature is 60°C-80°C, and the drying time is 6h-10h. After the drying is completed, the micropowder is cooled to 25°C to obtain modified spherical silicon micropowder, which is taken out and sealed for storage.

Images