Solid spherical silicon micropowder and method for preparing the same

Abstract

The application discloses solid spherical silicon micro-powder and a preparation method thereof. The preparation method comprises the following steps: providing a silicon compound system, wherein the silicon compound system comprises a silica sol and a thickening agent, the thickening agent contains carboxyl and or amide groups, and does not contain alkali metal ions; performing spray drying on the silicon compound system to obtain a silicon micro-powder precursor; and performing heat treatment on the silicon micro-powder precursor to remove organic phase substances and solvents in the silicon micro-powder precursor, thereby obtaining solid spherical silicon micro-powder. The preparation method provided by the application adds the thickening agent into the silica sol to form the silicon compound system, and then performs spray drying. After the solvents and the organic phase are removed through heat treatment, the solid spherical silicon micro-powder with high compactness and high sphericity is obtained. The preparation process is simple and easy to implement, the energy consumption is low, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of micro-nano material preparation technology, and in particular to a solid spherical silicon micropowder and its preparation method. Background Technology

[0002] Spherical silica micropowder (hereinafter referred to as spherical silica micropowder) has superior properties such as high light transmittance, high dielectric constant, high moisture resistance, high filling capacity, low expansion, low stress and low coefficient of friction, and is widely used in many fields such as epoxy molding compounds, catalysts, copper clad laminates, adhesives and aerospace.

[0003] With the rapid development of microelectronics technology, the requirements for packaging fillers needed for integrated circuits are becoming increasingly stringent. Not only are high purity and ultrafine properties required, but the morphology of the filler is also important. Better sphericity means better flowability after mixing with resin, more uniform film formation, and less resin addition. Higher filler content results in lower thermal expansion, lower thermal conductivity, and ultimately, higher performance for electronic components. Compared to angular powder, solid spherical powder exhibits lower stress and higher packaging yield, and is less prone to mechanical damage during various stages.

[0004] For example, the packaging materials required for LED packaging are different from other packaging materials. They require high transparency, good heat resistance, low viscosity, and are not prone to bubble formation. High-end packaging materials will mix in a certain amount of high-purity solid spherical silicon powder, which is required to have high whiteness, good transparency, low viscosity, and few impurities, so as to make its performance more superior.

[0005] In addition, silica, as a commonly used solid catalyst, has a high specific surface area that can provide more active sites, which can maximize the reaction rate. It also has good thermal stability and the ability to selectively control the pore structure of silica catalyst supports through different synthesis methods, thus enabling selective control of catalytic reactions. Therefore, it has a wide range of applications in petrochemical, environmental protection, pharmaceutical, and new energy fields.

[0006] Currently, the main methods for preparing high-purity solid spherical silicon micropowder include flame sphericalization and high-temperature melt spraying. The flame sphericalization method involves crushing, screening, purifying, and finely grinding quartz ore, then melting it in a high-temperature field generated by combustion gas. Surface tension causes the ore to form spherical particles, which are then cooled to obtain spherical silicon micropowder. The disadvantages of this method are its complexity, difficulty in completely removing quartz impurities resulting in low purity, and high energy consumption in the final high-temperature sphericalization stage. The high-temperature melt spraying method involves melting silicon oxide at over 2000 degrees Celsius, then cooling it through spray to form spherical silicon micropowder. This method is mainly used in the United States and Japan, but it requires demanding equipment.

[0007] For example, Chinese invention patent CN101037206A mentions obtaining spherical silica gel by centrifugal spray drying of silica sol with high solid content (30%–40%), followed by heat treatment at 1200℃–2200℃ to obtain spherical silica micropowder. However, the heat treatment process is extremely energy-intensive, and in essence, it still utilizes high-temperature melting to form spherical micropowder. Chinese invention patent CN113880098A mentions obtaining silica micropowder by secondary growth of silica seeds, addition of some active silicic acid, followed by spray drying and heat treatment. Chinese invention patent CN101037206A also mentions using high solid content (30%~40%) silica sol by centrifugal spray drying. This method is relatively difficult to obtain high solid content silica sol and consumes a lot of energy. In addition, the spherical silica powder obtained by this method is ring-shaped. This silica powder has a small specific surface area, so the filling amount is small when mixing epoxy resin. Furthermore, it is easy to have flash during the encapsulation process, that is, the edges are not smooth after epoxy curing and it is easy to overflow.

[0008] Chinese invention patent CN113880098A describes a method for obtaining silicon micropowder by secondary growth of silicon oxide seeds, addition of some active silicic acid, followed by spray drying and heat treatment. This method is complex, and the preparation of active silicic acid is cumbersome, requiring the removal of impurities such as sodium and potassium ions through both anion and cation exchange resins.

[0009] It is evident that existing technologies struggle to solve the technical problem of obtaining solid spherical silicon micropowder with high sphericity through a simple, easy, and low-cost method. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a solid spherical silicon micropowder and its preparation method.

[0011] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0012] In a first aspect, the present invention provides a method for preparing solid spherical silica powder, comprising:

[0013] A silicon complex system is provided, the silicon complex system comprising silica sol and a thickener, the thickener containing carboxyl and / or amide groups and not containing alkali metal ions;

[0014] The silicon composite system was spray-dried to obtain a silicon micropowder precursor;

[0015] The silicon micropowder precursor is subjected to heat treatment to remove organic phase substances and solvents to obtain solid spherical silicon micropowder.

[0016] Secondly, the present invention also provides a solid spherical silicon micropowder prepared by the above-described preparation method.

[0017] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0018] The preparation method provided by this invention involves adding a thickener to silica sol to form a silica complex system, followed by spray drying and heat treatment to remove the solvent and organic phase, resulting in solid silica micropowder with high density and high sphericity. The preparation process is simple, easy to implement, energy-efficient, and inexpensive.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0020] Figure 1 This is a micrograph of solid spherical silicon micropowder prepared in a typical embodiment of the present invention;

[0021] Figure 2 This is a micrograph of solid spherical silicon micropowder prepared in another typical embodiment of the present invention;

[0022] Figure 3 This is a micrograph of solid spherical silicon micropowder prepared in another typical embodiment of the present invention;

[0023] Figure 4 This is a micrograph of solid spherical silicon micropowder prepared in another typical embodiment of the present invention;

[0024] Figure 5 This is a micrograph of solid spherical silicon micropowder prepared in a typical comparative case of the present invention;

[0025] Figure 6 This is a micrograph of solid spherical silicon micropowder prepared in another typical comparative case of the present invention;

[0026] Figure 7 This is a micrograph of solid spherical silicon micropowder prepared in another typical comparative case of the present invention. Detailed Implementation

[0027] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0029] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component or method step from another that has the same name, and do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0030] This invention provides a method for preparing solid spherical silica powder, which includes the following steps:

[0031] A silicon complex system is provided, the silicon complex system comprising silica sol and a thickener, the thickener containing carboxyl and / or amide groups and not containing alkali metal ions;

[0032] The silicon composite system was spray-dried to obtain a silicon micropowder precursor;

[0033] The silicon micropowder precursor is subjected to heat treatment to remove organic phase substances and solvents to obtain solid spherical silicon micropowder.

[0034] The silica sol comprises a silica precursor and a solvent. The thickener is dissolved in the solvent and specifically binds or reacts with the active groups on the surface of the silica precursor. This not only changes the viscosity of the sol but also alters the binding tendency and rate of the precursor gel during spray drying. As a result, the precursor gel can rapidly coalesce into integral particles during spray drying, rather than being affected by solvent evaporation and causing various deformations or cracks. Consequently, silica micropowder with excellent sphericity and density can be obtained.

[0035] It is evident that selecting a specific thickener is a crucial technical aspect of this invention. The role of the thickener is multifaceted, and not merely limited to adjusting viscosity.

[0036] Furthermore, in some embodiments, the thickener does not contain potassium and / or sodium ions to prevent the introduction of new alkali metal ion impurities into the silica gel system.

[0037] Regarding the specific selection of thickeners, in some embodiments, the thickeners include any one or a combination of two or more of polyacrylamide, carboxymethyl cellulose, carboxyethyl cellulose, polyacrylic acid, polymethacrylic acid, and carbomer, but are not limited thereto. Other types of thickeners that meet the significant characteristics summarized in this invention may also be used.

[0038] Regarding the specific proportions, in some embodiments, the solid content of the silica sol is 15-50%;

[0039] In some embodiments, the thickener content in the silicon complex system is 0.001-5%, in some embodiments it is preferably 0.05-2%, and in some embodiments it is even more preferably 0.1-1%.

[0040] Regarding how to obtain silica sol with a high solid content, in some embodiments, the silica sol is obtained by heating, evaporating and concentrating a silica sol precursor with a lower solid content;

[0041] Specifically, in some embodiments, the solid content of the silica sol precursor is 1-5%.

[0042] More specifically, in some embodiments, the preparation method includes, for example, the following processes:

[0043] The silica sol precursor is obtained by subjecting a solution-gel reaction of an organosilicon source solution under alkaline conditions.

[0044] The silica sol precursor is heated and concentrated to obtain the silica sol.

[0045] Regarding the implementation methods of spray drying, in some implementation schemes, the spray drying method includes any one of airflow type and centrifugal type, but is not limited to these;

[0046] Based on spray drying, in some implementations, the drying conditions of spray drying, such as pressure, rotation speed, flow rate, etc., can be controlled to adjust the particle size of the silicon micropowder precursor to 1-50 μm. Specific control methods and principles can be found in existing technical guidelines and will not be elaborated here.

[0047] After drying, in some embodiments, the silicon micropowder precursor still contains a certain amount of water or other aqueous solvents, such as water content of 5-10%.

[0048] In order to fully remove moisture (or other solvents) and organic components such as thickeners, in some embodiments, the heat treatment is carried out at a temperature of 80-1000°C for a time of 5-24 hours;

[0049] Furthermore, the inventors of this invention have discovered that in order to achieve the optimal solid spherical effect, a multi-stage heating method can be adopted. For example, in some embodiments, preferably, the heat treatment includes a first stage and a second stage. The first stage is a dehydration stage with a temperature of 80-200°C and a time of 2-12 hours; the second stage is a calcination stage with a temperature of 200-1000°C and a time of 3-12 hours.

[0050] The first stage is a low-temperature treatment process, the main purpose of which is to maintain a specific temperature to fully remove moisture or other solvents. The second stage is a high-temperature treatment process, which mainly removes organic components, causing them to decompose or further volatilize, thereby obtaining solid silica powder with a better morphology.

[0051] As a typical application example of the above technical solution, the preparation process of a solid spherical silica powder includes the following specific steps:

[0052] (1) Synthesis of silica sol

[0053] Silica sol with low solid content (1-5%) was synthesized by solution-gel method using tetraethyl orthosilicate as the organosilicon source under alkaline conditions with heating and stirring.

[0054] (2) Concentration of silica sol

[0055] The above-mentioned low-solids-content silica sol was heated and concentrated to obtain high-solids-content silica sol (15%-50%).

[0056] (3) Material mixing and compounding

[0057] High-solids-content silica sol is mixed with a thickener under heating and stirring conditions to form a silica sol solution containing 0.001%-5% thickener. The thickener selected in this case is a specific thickener containing carboxyl or amide groups, such as polyacrylamide, carboxymethyl cellulose, carboxyethyl cellulose, polyacrylic acid, polymethacrylic acid, carbomer, etc., which readily adsorbs or reacts with the silanol groups on the silica surface, thereby facilitating the aggregation of nano-silica particles. The thickener does not contain sodium or potassium ions to avoid cation interference. The preferred thickener content is 0.05%-2%, and the most preferred is 0.1%-1%.

[0058] (4) Spray drying

[0059] After the silica sol is properly compounded, it is spray-dried (either by airflow or centrifugation) to obtain spherical silica powder. However, at this time, the moisture content is still relatively high at 5%-10%. Specific thickeners are removed by high-temperature calcination.

[0060] (5) Heat treatment

[0061] The product obtained after spray drying is sent to a muffle furnace for high-temperature heat treatment to burn off excess thickener. After the heat treatment is completed, the product is cooled to room temperature and then removed to obtain the target high-purity spherical silicon micropowder.

[0062] The above process can yield spherical silica powder with a silica purity of 99.999%.

[0063] Correspondingly, the embodiments of the present invention also provide solid spherical silicon micropowder prepared by the preparation method provided in any of the above embodiments.

[0064] In some embodiments, the silica purity of the solid spherical silica powder is above 99.999%.

[0065] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0066] Example 1

[0067] This embodiment illustrates the preparation process of solid spherical silica powder, as shown below:

[0068] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0069] Step 2: Take 500g of silica sol with a solid content of 20% and add 0.005g of nonionic polyacrylamide (Adamas, nonionic, molecular weight: 18 million). Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.001% nonionic polyacrylamide.

[0070] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain the silica micropowder precursor.

[0071] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 5 hours, then set the temperature to 800℃ for 10 hours to remove the thickener in the system.

[0072] Results: The spherical silica powder obtained from the silica sol prepared with 0.001% nonionic polyacrylamide through a series of processes exhibited... Figure 1 The sample is in the state shown. There are a few solid spheres, but most of them contain ring structures and cracks. A small number of microspheres with better morphology can be extracted through screening and then applied.

[0073] Example 2

[0074] This embodiment illustrates the preparation process of solid spherical silica powder, as shown below:

[0075] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0076] Step 2: Take 500g of silica sol with a solid content of 20% and add 0.05g of polyacrylamide (Adamas, non-ionic, molecular weight: 18 million). Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.01% polyacrylamide.

[0077] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain the silica micropowder precursor.

[0078] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 5 hours, then set the temperature to 800℃ for 10 hours to remove the thickener in the system.

[0079] Results: The spherical silica powder obtained from the silica sol prepared with 0.01% nonionic polyacrylamide through a series of processes exhibited the following characteristics: Figure 2 The state shown is as follows: The ring structure in the powder disappears, and a small number of cracks exist in the spheres, especially for larger microspheres, where the probability of cracks appearing is significantly higher.

[0080] Example 3

[0081] This embodiment illustrates the preparation process of solid spherical silica powder, as shown below:

[0082] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0083] Step 2: Take 500g of silica sol with a solid content of 20% and add 2.0g of polyacrylamide (Adamas, non-ionic, molecular weight: 18 million). Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.4% polyacrylamide.

[0084] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain the silica micropowder precursor.

[0085] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 5 hours, then set the temperature to 800℃ for 10 hours to remove the thickener in the system.

[0086] Results: The silica sol obtained by a series of processes from the silica sol formulated with 0.4% polyacrylamide exhibited the following characteristics: Figure 3 The shape shown is a solid sphere, with no hollows or cracks.

[0087] The obtained high-purity solid spherical silica powder was analyzed by ICP-OES, and the results are as follows:

[0088] Table 1 Impurity content of spherical silica powder

[0089] element Na K Mg Al Fe Zn Cl Cu Ag content <1ppm <1ppm <1ppm <1ppm <1ppm <1ppm <1ppm <1ppm <1ppm

[0090] Example 4

[0091] This embodiment illustrates the preparation process of solid spherical silica powder, as shown below:

[0092] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0093] Step 2: Take 500g of silica sol with a solid content of 20% and add 20.0g of polyacrylamide (Adamas, non-ionic, molecular weight: 18 million). Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 4% non-ionic polyacrylamide.

[0094] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer. However, during the spray drying process, the nozzles become clogged due to the high viscosity of the material, making it impossible to proceed with subsequent process steps. In contrast, using centrifugal spray drying can successfully prepare solid silica microspheres.

[0095] Results: The silica sol prepared by blending 4% nonionic polyacrylamide experienced nozzle clogging during spray drying and could not function properly. Therefore, it is recommended to use centrifugal spray drying when the content of thickener is above 4% or the corresponding viscosity is above 2000 cp.

[0096] Example 5

[0097] This embodiment illustrates the preparation process of solid spherical silica powder, as shown below:

[0098] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0099] Step 2: Take 500g of silica sol with a solid content of 20% and add 2.0g of carboxymethyl cellulose (FCC (Wokai)). Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.4% carboxymethyl cellulose.

[0100] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain the silica micropowder precursor.

[0101] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 6 hours, then set the temperature to 800℃ for 6 hours to remove the thickener in the system.

[0102] Results: The silica sol obtained from the compound of 0.4% carboxymethyl cellulose, after a series of processes, yielded silica micropowder exhibiting the following characteristics: Figure 4 The shape shown is basically a solid sphere, with no hollows or cracks.

[0103] The viscosity tests of the obtained silica sol composite system in the above embodiments are shown in Table 2 below:

[0104] Table 2. Viscosities of 20% silica sol with different amounts of thickener added.

[0105]

[0106] Comparative Example 1

[0107] The preparation process of the silicon micropowder in this comparative example is as follows:

[0108] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0109] Step 2: Taking airflow spray drying as an example, silica sol with a solid content of 20% is spray dried through an airflow spray dryer to obtain silica micropowder precursor.

[0110] Step 3: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove moisture for 5 hours, then set the temperature to 800℃ for 10 hours.

[0111] Result: Without the addition of specific thickeners containing carboxyl or amide groups, the silica sol-derived silica micropowder through a series of processes exhibits the following characteristics: Figure 5 The states shown are all cyclic, hollow silica powders.

[0112] Comparative Example 2

[0113] The preparation process of the silicon micropowder in this comparative example is as follows:

[0114] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0115] Step 2: Take 500g of silica sol with a solid content of 20% and add 2.0g of methylcellulose (Adamas, 40000mPa.s), which does not contain carboxyl or amide groups. Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.4% methylcellulose. The thickening ability of the thickener used is similar to that in Example 3. Therefore, the viscosity of the formed silica sol composite system is similar to that in Example 3.

[0116] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain silica micropowder precursor.

[0117] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 5 hours, then set the temperature to 800℃ for 10 hours of high-temperature firing.

[0118] Results: The silica sol obtained from the 0.4% methylcellulose compound, after a series of processes, yielded silica micropowder exhibiting the following characteristics: Figure 6 The state shown is basically a hollow sphere.

[0119] Comparative Example 3

[0120] The preparation process of the silicon micropowder in this comparative example is as follows:

[0121] Step 1: Obtain the low solid content silica sol synthesized by solution-gel method, concentrate it to 20% solid content under heating at 150℃, stop heating after reaching the target, cool to room temperature, and then release the material under normal pressure.

[0122] Step 2: Take 500g of silica sol with a solid content of 20% and add 2.0g of polyethylene glycol (Adamas, Mv~5,000,000), which does not contain carboxyl or amide groups. Heat and stir or homogenize at 50 degrees Celsius for 30 minutes to obtain silica sol with a solid content of 20% containing 0.4% polyethylene glycol. The thickening ability of the thickener used is similar to that in Example 3. Therefore, the viscosity of the formed silica sol composite system is similar to that in Example 3.

[0123] Step 3: Taking airflow spray drying as an example, the compounded silica sol is spray dried through an airflow spray dryer to obtain the silica micropowder precursor.

[0124] Step 4: Feed the silicon micro powder into a muffle furnace, first set the temperature to 120℃ to remove water for 5 hours, then set the temperature to 800℃ for 10 hours of high-temperature firing.

[0125] Results: The silica sol obtained from the 0.4% polyethylene glycol compound, after a series of processes, yielded silica micropowder exhibiting the following characteristics: Figure 7 The state shown is basically a hollow sphere.

[0126] This indicates that simply adjusting the viscosity of the silicon composite system is insufficient to obtain solid silicon microspheres with good morphology; it is also necessary to combine specific thickeners with the binding characteristics of silicon precursors to achieve this.

[0127] In addition, during the research and development process, the present invention also conducted multiple experiments and tests on other thickeners with similar characteristics and preparation conditions, all of which showed superior effects, which will not be elaborated here.

[0128] Based on the above embodiments and comparative examples, it is clear that adding a certain amount of thickener can yield high-purity, solid spherical silica powder from silica sol for application in the fields of catalysis and encapsulation. This invention allows for the more convenient acquisition of solid spherical silica powder suitable for catalysis and encapsulation without introducing impurities, with a relatively simple process flow and low energy consumption.

[0129] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing solid spherical silica powder, characterized in that, include: A silicon compound system is provided, the silicon compound system comprising silica sol and a thickener, wherein the content of the thickener in the silicon compound system is 0.001-5%, and the thickener contains carboxyl and / or amide groups and does not contain alkali metal ions; The silicon composite system was spray-dried to obtain a silicon micropowder precursor. The addition of the thickener changed the viscosity of the silica sol and also changed the bonding tendency and bonding rate of the silicon composite system during spray drying. The silicon micropowder precursor is subjected to heat treatment to remove organic phase substances and solvents to obtain solid spherical silicon micropowder. The heat treatment temperature is 80-1000℃ and the time is 5-24h.

2. The preparation method according to claim 1, characterized in that, The thickener does not contain potassium and / or sodium ions.

3. The preparation method according to claim 1 or 2, characterized in that, The thickener includes any one or a combination of two or more of polyacrylamide, carboxymethyl cellulose, carboxyethyl cellulose, polyacrylic acid, polymethacrylic acid, and carbomer.

4. The preparation method according to claim 1, characterized in that, The solid content of the silica sol is 15-50%; And / or, the thickener content in the silicon complex system is 0.05-2%.

5. The preparation method according to claim 4, characterized in that, The thickener content in the silicon composite system is 0.1-1%.

6. The preparation method according to claim 4, characterized in that, The silica sol is obtained by heating and evaporating a silica sol precursor with a lower solid content and concentrating it. The solid content of the silica sol precursor is 1-5%.

7. The preparation method according to claim 6, characterized in that, The preparation method specifically includes: The silica sol precursor is obtained by subjecting a solution-gel reaction of an organosilicon source solution under alkaline conditions. The silica sol precursor is heated and concentrated to obtain the silica sol.

8. The preparation method according to claim 1, characterized in that, The spray drying method includes either airflow or centrifugal drying, and the particle size of the silicon micropowder precursor is 1-50 μm.

9. The preparation method according to claim 1, characterized in that, The water content of the silicon micropowder precursor is 5-10%.

10. The preparation method according to claim 1, characterized in that, The heat treatment includes a first stage and a second stage. The first stage is a dehydration section with a temperature of 80~200℃ and a time of 2~12h. The second stage is a calcination section with a temperature of 200~1000℃ and a time of 3h~12h.

11. Solid spherical silica powder prepared by the preparation method according to any one of claims 1-10.

12. The solid spherical silica powder according to claim 11, characterized in that, The solid spherical silica powder has a silica purity of 99.999% or higher.

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