Preparation method of monodisperse spherical silicon oxide

Abstract

The invention discloses a preparation method of monodisperse spherical silicon oxide. The preparation method comprises the following steps: dissolving a carbon source in deionized water, reacting in a hydrothermal reaction kettle, centrifuging, washing and drying to obtain carbon quantum dots; the preparation method comprises the following steps: respectively dissolving carbon quantum dots, tetraethyl orthosilicate and ammonia water in a mixed solution of absolute ethyl alcohol and deionized water, uniformly mixing the two solutions to obtain a white solution, centrifuging, washing with water, and freeze-drying to prepare SiO2 / C nano composite particles; and calcining the spherical SiO2 in an air atmosphere to obtain the spherical SiO2. Based on a nano-toughening regulation and control mechanism, accurate regulation and control of the particle size in a range of 50-1000nm are realized by optimizing template size distribution and reaction kinetic parameters. The prepared SiO2 nanospheres are smooth in surface, high in specific surface area and excellent in flowability, and meet the reinforcement requirements of high-end composite materials. In addition, the preparation method is simple in process, low in cost and high in controllability, large-scale production is easy to achieve, and practicability is achieved.

Description

Technical Field

[0001] The invention relates to a preparation method of monodisperse spherical silicon oxide, belonging to the technical field of material synthesis. Background Art

[0002] Spherical silica is one of the most important new high-tech ultrafine inorganic materials. It boasts a large specific surface area and small particle size, while exhibiting excellent flowability, low internal stress, and good dimensional stability and dispersibility. These properties make it an irreplaceable player in numerous technological fields, with broad application prospects and enormous commercial value. For example, with the rapid development of 5G technology, the requirements for epoxy molding fillers in integrated circuit chips are becoming increasingly stringent, and the demand for nanoscale, high-purity spherical silica is particularly increasing. This trend places even stricter standards on spherical silica for size uniformity, high sphericity, high purity, and nanometer-level precision.

[0003] Currently, the preparation methods for spherical silica can be categorized into physical and chemical methods. While physical methods (such as flame spheronization and high-temperature melt spraying) can produce micron-sized powders, their products suffer from significant drawbacks such as high impurity content, wide particle size distribution, and difficulty in size sorting, making them unable to meet the purity and uniformity requirements of high-end semiconductor packaging materials. In contrast, chemical methods (including sol-gel, precipitation, hydrothermal, and microemulsion) offer greater application potential. The sol-gel method has attracted considerable attention due to its mature technology and high process controllability. This method uses a highly active silicate precursor as the raw material, which is hydrolyzed in aqueous solution to form a sol. The sol particles then condense to form a gel network, which is then converted into a high-purity oxide through drying and calcination. For example, the traditional Stober method uses ammonia to catalyze the hydrolysis of ethyl orthosilicate in an ethanol-water system to prepare silica of varying nanometer sizes (50 nm to 1 μm). Although the method achieves the purpose of controlling the size of the synthesized sample particle size by concocting precursor solutions of different proportions, it is impossible to accurately control its growth size, and the raw material consumption of required organic solvents is huge, which increases the cost of preparing spherical nano-silicon oxide by the method. If a certain seed nucleus is added as the growth center of the silicon oxide sphere in the sol-gel method, the spherical silicon oxide of micro-nano structure is prepared by auxiliary hydrolysis of ethyl orthosilicate, not only the size controllability and the monodispersity of the synthesized nano-silicon dioxide particles can be guaranteed, but also the consumption of a large amount of organic solvents is avoided, which has a very strong practical application value. However, although the seed-assisted growth mechanism has been widely used in the field of metal nanoparticle synthesis, in the silicon oxide system, related research is still in a blank stage, and there is no technical report on introducing seed nucleus to promote the preparation of spherical silicon oxide by the sol-gel method. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing sol-gel method for preparing spherical silicon oxide cannot accurately control its growth size, and the required raw materials such as organic solvents consume a huge amount of raw materials.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing monodisperse spherical silicon oxide comprises the following steps:

[0007] Step 1): Preparation of carbon quantum dots: dissolving a carbon source in deionized water, mixing well, and placing in a hydrothermal reactor for reaction, centrifuging, washing, and drying to obtain carbon quantum dots;

[0008] Step 2): Preparation of SiO2 / C nanocomposite particles: Dissolve carbon quantum dots, tetraethyl orthosilicate, and ammonia in a mixture of anhydrous ethanol and deionized water, respectively, mix the two, and stir at a constant temperature to obtain a white solution; centrifuge, wash with water, and freeze-dry;

[0009] Step 3): Calcination: The SiO2 / C composite particles are calcined in an air atmosphere to remove the template and obtain spherical SiO2.

[0010] Preferably, in step 1), the carbon source is one or more of glucose, chitosan, citric acid, ethylenediamine, amino acids, lignocellulose and petroleum coke; and the amount of the carbon source is 2-20% of the mass of the reaction system solution.

[0011] Preferably, in step 1), the reaction temperature is 120-200° C. and the reaction time is 20-480 min.

[0012] Preferably, in step 2), the carbon quantum dots are 0.01-2% of the mass of the reaction system solution, i.e., the white solution; the concentration of tetraethyl orthosilicate in the reaction system solution is 0.1-1 mol / L; the concentration of ammonia water is 0.1-1.1 mol / L; the volume fraction of ammonia water in the reaction system solution is 10-30%; and the volume ratio of anhydrous ethanol to deionized water is 10-120:1-60.

[0013] Preferably, in step 2), the particle size of the obtained SiO2 / C nanocomposite particles is between 50-1000 nm.

[0014] Preferably, in step 3), the calcination temperature is 400-600° C., the heating rate is 1-10° C. / min, and the calcination time is 1-5 h.

[0015] The present invention proposes a method for preparing monodisperse spherical silica based on a carbon quantum dot template strategy. A seed crystal nucleus-assisted sol-gel process is adopted to prepare spherical nanoparticles with carbon quantum dots as the core and silica as the shell by precisely controlling the reaction conditions. The carbon quantum dots are subsequently calcined to obtain spherical silica.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a method for preparing monodisperse spherical silica based on a carbon quantum dot template strategy. The method adopts a seed crystal nucleus-assisted sol-gel process to form nanocomposite particles with carbon quantum dots as the core and SiO2 as the shell through template-induced self-assembly. The template is removed through a subsequent high-temperature calcination process to finally obtain monodisperse spherical silica nanoparticles. Based on the nano-toughening control mechanism, by optimizing the template size distribution and reaction kinetic parameters, precise control of the particle size within the range of 50-1000nm is achieved. The prepared SiO2 nanospheres have a smooth surface, a high specific surface area and excellent fluidity, meeting the requirements for the reinforcement of high-end composite materials. In addition, the added carbon quantum dots can not only inhibit the hydrolysis rate of ethyl orthosilicate, facilitating the precise control of the size of the silica spheres, but also greatly reduce the amount of organic solvent used and the reaction time. Therefore, the preparation method of the present invention is simple in process, low in cost, highly controllable, easy to implement large-scale production, and has practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the preparation method provided by the present invention;

[0019] Figure 2 SEM images of spherical silicon oxide prepared in the present invention: a is a SiO2 ball with 0.5 wt% carbon quantum dots added; b is a SiO2 ball with 1 wt% carbon quantum dots added; c is a SiO2 ball with 1.5 wt% carbon quantum dots added; d is a SiO2 ball with 0.1 wt% carbon quantum dots added;

[0020] Figure 3 This is the SEM image of spherical silicon oxide without the addition of carbon quantum dots. DETAILED DESCRIPTION

[0021] To make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0022] In the present invention, the materials and reagents used, unless otherwise specified, can be obtained from commercial sources.

[0023] Example 1

[0024] (1) 3 g of glucose was dissolved in 50 mL of deionized water and mixed to obtain a transparent solution. The solution was then placed in a 50 mL polytetrafluoroethylene hydrothermal reactor and reacted at 150 °C for 430 min. The solid residue was then centrifuged at 11,000 rpm to obtain a solid residue. The solid residue was washed with ethanol three times and then vacuum dried to obtain carbon quantum dots.

[0025] (2) 0.5 wt% carbon quantum dots, 0.5 mol / L TEOS and 0.5 mol / L ammonia water were dissolved in an appropriate amount of anhydrous ethanol and deionized water (25:14) mixture, and then mixed. The mixture was then stirred at a constant temperature of 60 °C for 10 h. Finally, the mixture was centrifuged, washed with water 2 to 3 times and freeze-dried for 24 h to obtain monodisperse SiO2 / C nanocomposite particles with a particle size between 50 and 1000 nm.

[0026] (3) The SiO2 / C nanocomposite particles prepared in step (2) were heated to 500°C at a rate of 5°C / min in an air atmosphere, calcined for 2 h, and then the template was removed to obtain spherical SiO2.

[0027] The microscopic morphology of the spherical SiO2 prepared in this embodiment is shown in FIG. Figure 2 It can be seen that the SiO2 spheres prepared by the present invention are relatively uniform, have a good spherical structure and a good size.

[0028] Example 2

[0029] The only difference between this embodiment and embodiment 1 is that the amount of carbon quantum dots added is 1 wt %. The rest of the contents are exactly the same as those described in embodiment 1.

[0030] The microscopic morphology of the spherical SiO2 prepared in this embodiment is shown in FIG. Figure 2 It can be seen that the size of the SiO2 spheres prepared by the present invention increases with the increase of carbon content.

[0031] Example 3

[0032] The only difference between this embodiment and embodiment 1 is that the amount of carbon quantum dots added is 1.5 wt %. The rest of the contents are exactly the same as those described in embodiment 1.

[0033] The microscopic morphology of the spherical SiO2 prepared in this embodiment is shown in FIG. Figure 2 Figure c shows that large-sized spherical SiO2 balls were successfully prepared.

[0034] Example 4

[0035] The only difference between this embodiment and embodiment 1 is that the amount of carbon quantum dots added is 0.1 wt %. The rest of the contents are exactly the same as those described in embodiment 1.

[0036] The microscopic morphology of the spherical SiO2 prepared in this embodiment is shown in FIG. Figure 2 It can be seen that due to the reduction of the introduction of carbon quantum dots, the size difference between the SiO2 spheres gradually becomes larger and the distribution is also uneven.

[0037] Comparative Example 1

[0038] The only difference between this comparative example and Example 1 is that no carbon quantum dots were added. The rest of the contents are exactly the same as those described in Example 1.

[0039] The microscopic morphology of the spherical SiO2 prepared in this comparative example is shown in FIG. Figure 3 It can be seen that due to the lack of carbon quanta, the prepared SiO2 beads could not maintain a dispersed state and agglomeration occurred.

Claims

1. A method for preparing monodisperse spherical silicon oxide, characterized in that: The following steps are involved: Step 1): Preparation of carbon quantum dots: dissolving a carbon source in deionized water, mixing well, and placing in a hydrothermal reactor for reaction, centrifuging, washing, and drying to obtain carbon quantum dots; Step 2): Preparation of SiO2 / C nanocomposite particles: Dissolve carbon quantum dots, tetraethyl orthosilicate, and ammonia in a mixture of anhydrous ethanol and deionized water, respectively, mix the two, and stir at a constant temperature to obtain a white solution; centrifuge, wash with water, and freeze-dry; Step 3): Calcination: The SiO2 / C composite particles are calcined in an air atmosphere to remove the template and obtain spherical SiO2.

2. The preparation method according to claim 1, wherein In the step 1), the carbon source is one or more of glucose, chitosan, citric acid, ethylenediamine, amino acids, lignocellulose and petroleum coke; the amount of the carbon source is 2-20% of the mass of the reaction system solution.

3. The preparation method according to claim 1, wherein In the step 1), the reaction temperature is 120-200° C. and the reaction time is 20-480 min.

4. The preparation method according to claim 1, wherein In the step 2), the carbon quantum dots account for 0.01-2% of the mass of the reaction system solution, i.e., the white solution; the concentration of tetraethyl orthosilicate in the reaction system solution is 0.1-1 mol / L; the concentration of ammonia water is 0.1-1.1 mol / L; the volume fraction of ammonia water in the reaction system solution is 10-30%; and the volume ratio of anhydrous ethanol to deionized water is 10-120:1-60.

5. The preparation method according to claim 1, wherein In the step 2), the particle size of the obtained SiO2 / C nanocomposite particles is between 50-1000 nm.

6. The preparation method according to claim 1, wherein In the step 3), the calcination temperature is 400-600° C., the heating rate is 1-10° C. / min, and the calcination time is 1-5 hours.

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