Manufacturing technology of CoFe2O4-coated SiO2 yolk-coated shell spherical tank

Abstract

The invention relates to a manufacturing technology of a CoFe2O4-coated SiO2 yolk-coated shell spherical tank, and belongs to the technical field of new material preparation. The method comprises the following three steps: (1) preparing an electronic injection solution; (2) preparing [Co (acac) 2 + Fe (acac) 3 + TEOS] / PVP original composite microspheres by adopting a uniaxial electronic injection ionization technology; (3) preparing a CoFe2O4-coated SiO2 yolk-coated shell spherical tank, adopting ammonium bifluoride as a fluorination reagent and activated carbon granules as an auxiliary reducing agent, and performing heating fluorination-oxidation treatment on the original composite microspheres in air to obtain the CoFe2O4-coated SiO2 yolk-coated shell spherical tank with the average diameter of 1.42 + / -0.01 mu m and the average diameter of the yolk balls CoFe2O4 of 1.05 + / -0.02 mu m. The preparation method is simple and easy to implement, batch production can be achieved, and the novel material of the special structure has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the research field of new material preparation, and in particular to a manufacturing technology of a CoFe2O4@SiO2 yolk@shell spherical tank. Background Art

[0002] The preparation, structure, properties, and applications of yolk@shell spherical jars have garnered significant attention and have become a frontier and hot topic in research across disciplines such as materials science, condensed matter physics, and chemistry. These artificially synthesized yolk@shell spherical jars consist of a yolk sphere nestled within a shell, with a gap between the yolk and the shell, and openings in the shell. Typically, the yolk and shell are composed of different materials. These yolk@shell spherical jars, with their unique morphology and structure, differ from conventional hollow spheres and micro / nanospheres, possessing unique optical, electrical, magnetic, and catalytic properties and a wide range of applications, attracting considerable attention.

[0003] Cobalt ferrite (CoFe2O4) is a typical complex metal oxide with an inverse spinel structure and is widely used in magnetism, electricity, energy, and the environment. Silicon dioxide, also known as silicon oxide (SiO2), is also widely used in the manufacture of glass, water glass, pottery, enamel, refractory materials, aerogel felt, ferrosilicon, molding sand, elemental silicon, and cement. If CoFe2O4 microspheres are used as yolk balls and coated with a silica shell, with a certain gap between the yolk and the shell and an opening in the SiO2 shell, a SiO2-coated CoFe2O4 yolk@shell spherical jar is formed, labeled CoFe2O4@SiO2 yolk@shell spherical jar. The substance before the @ is the core layer CoFe2O4, and the substance after the @ is the shell SiO2, indicating that the latter substance SiO2 encapsulates the former substance CoFe2O4. Due to its special zero-dimensional structure, this new material will have broad application prospects. There are currently no reports on CoFe2O4@SiO2 yolk@shell spherical tanks.

[0004] Electrospray ionization technology is an effective method for preparing micro-nanospheres or particles. This method involves spraying a charged polymer electrospray solution in an electrostatic field, where it is pulled by electrostatic forces and sprayed out as a mist onto a receiving screen. The solvent then evaporates at room temperature, yielding micro-nanospheres or particles. If the polymer electrospray solution contains metal nitrates, acetates, or acetylacetonates, the inorganic-organic composite micro-nanospheres obtained after electrospraying can be heat-treated to remove the polymer template and decompose the metal nitrates, acetates, or acetylacetonates to yield inorganic oxide micro-nanospheres. Therefore, this single-axis electrospray ionization technique can be used to prepare a variety of polymer and inorganic oxide micro-nanospheres. By improving the nozzle structure and electrospray apparatus, using a two-layer coaxial nozzle and two polymer electrospray solutions, and by regulating the electrospray parameters, this two-layer coaxial electrospray ionization technique can be used to prepare core-shell micro-nanospheres. Furthermore, using a three-layer coaxial spray nozzle and three polymer electrospray solutions, and by adjusting the electrospray parameters, this three-layer coaxial electrospray ionization technique can produce three layers of concentric micro-nanospheres. The middle layer can then be removed through solution etching, solvent extraction, or high-temperature calcination to obtain egg-yolk@shell spherical jars. However, this method is complex to prepare, requires multiple parameters to be controlled, and the product morphology is difficult to control. The present invention combines simple single-axis electrospray ionization technology with fluorination technology and high-temperature calcination technology to successfully and conveniently directly prepare the novel CoFe2O4@SiO2 egg-yolk@shell spherical jars, avoiding the complex three-layer coaxial electrospray ionization process. This has not been reported previously.

[0005] When using electrospray ionization technology to prepare new materials, the nozzle structure, the type of raw materials, the molecular weight of the polymer template, the composition of the electrospray solution, the electrospray process parameters, the heat treatment process and the ambient atmosphere during heat treatment all have an important influence on the morphology, structure, size and composition of the final product. The present invention first adopts a single-axis electrospray ionization technology to add cobalt acetylacetonate Co(acac)2 and iron acetylacetonate Fe(acac)3 into a solvent N,N-dimethylformamide (DMF) to obtain a solution, then dissolves a polymer template agent polyvinylpyrrolidone (PVP) in dichloromethane (CH2Cl2) to obtain another solution, mixes the two solutions, and then adds tetraethyl orthosilicate (TEOS) to obtain an electrospray solution. It is crucial to control the viscosity of the electrospray solution. Electrospraying is performed under optimal experimental conditions to prepare [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres, and then a heating fluorination-oxidation treatment is performed in air using ammonium bifluoride (NH4HF2) as a fluorination reagent and activated carbon particles as an auxiliary reducing agent to directly obtain a CoFe2O4@SiO2 egg yolk@shell spherical tank with a novel structure. Summary of the Invention

[0006] In the background art, single-axis electrospray ionization technology was used to prepare micro-nanospheres, two-layer coaxial electrospray ionization technology was used to prepare core-shell micro-nanospheres, and three-layer coaxial electrospray ionization technology was used in combination with solution etching, solvent extraction, or high-temperature roasting to prepare egg yolk@shell spherical tanks. The methods, raw materials, templates, and solvents used are different from those of the method of the present invention. In order to provide a simple and convenient manufacturing technology for egg yolk@shell spherical tanks in the field of zero-dimensional new materials, we combined single-axis electrospray ionization technology, fluorination technology, and high-temperature oxidation roasting technology to invent a new method for directly manufacturing CoFe2O4@SiO2 egg yolk@shell spherical tanks.

[0007] The present invention is achieved by first preparing an electrospray solution with a certain viscosity, applying uniaxial electrospray ionization technology to electrospray, and preparing [Co(acac)2+Fe(acac)3+TEOS] / PVP primary composite microspheres under optimal experimental conditions. Using ammonium bifluoride (NH4HF2) as a fluorination agent and activated carbon particles as an auxiliary reducing agent, the solution is subjected to a high-temperature heating fluorination-oxidation treatment in air to directly obtain a novel CoFe2O4@SiO2 egg yolk@shell spherical tank. The steps are as follows:

[0008] (1) Preparation of electrospray solution

[0009] The cobalt source used was cobalt acetylacetonate Co(acac)2, the iron source used was iron acetylacetonate Fe(acac)3, the silicon source used was tetraethyl orthosilicate TEOS, the polymer template used was polyvinylpyrrolidone PVP with a molecular weight of 35,000, and N,N-dimethylformamide DMF and dichloromethane CH2Cl2 were used as solvents. 0.1296 g of Co(acac)2 and 0.3532 g of Fe(acac)3 were weighed and added to 4.0 g of DMF, and the mixture was stirred for 30 minutes to dissolve to obtain solution I. 0.8 g of PVP was added to 3.5 g of CH2Cl2, and the mixture was stirred for 30 minutes to dissolve to obtain solution II. After mixing solution I and solution II, 0.5 g of TEOS was added, and the mixture was magnetically stirred for 18 hours to obtain an electrospray solution.

[0010] (2) Preparation of [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres

[0011] Using uniaxial electrospray ionization technology, the electrospray solution is injected into a 10mL syringe with a No. 4.5 stainless steel syringe needle. A copper wire is inserted into the electrospray solution and connected to the positive terminal of a high-voltage direct current power supply. The angle between the stainless steel syringe needle and the horizontal plane is 30 degrees. Aluminum foil at an angle of 60 degrees to the horizontal plane is used as a receiving device and is grounded. The needle and the aluminum foil are kept perpendicular and 15 cm apart. Another copper wire is used to connect the aluminum foil to the zero-potential terminal of the high-voltage direct current power supply. The electrospray voltage is 16.5kV. The room temperature is 20-25°C and the relative humidity is 30%-50%. Electrospraying is carried out. As the solvent evaporates, [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres are obtained on the aluminum foil.

[0012] (3) Preparation of CoFe2O4@SiO2 yolk@shell spherical tank

[0013] Using NH4HF2 as the fluorine source and activated carbon particles as the auxiliary reducing agent, 0.3g of [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres were placed in a 10mL crucible, 3.0g of NH4HF2 was placed at the bottom of a 50mL crucible, and 10g of activated carbon particles were placed on it. Then the 10mL small crucible was placed in the middle of the 50mL large crucible, and the lid of the large crucible was closed. The two crucibles were placed in a muffle furnace, heated to 600℃ at a heating rate of 2℃ / min and kept warm for 4h, then cooled to 200℃ at a cooling rate of 2℃ / min, and then naturally cooled to room temperature with the furnace body to obtain CoFe2O4@SiO2 yolk@shell spherical jars with an average diameter of 1.42±0.01μm, and the average diameter of yolk balls CoFe2O4 was 1.05±0.02μm.

[0014] In the above process, the shell SiO2 of the CoFe2O4@SiO2 yolk@shell spherical jar is amorphous, the core yolk ball has good crystallinity and belongs to the cubic crystal system, the average diameter of the yolk@shell spherical jar is 1.42±0.01μm, and the average diameter of the yolk ball CoFe2O4 is 1.05±0.02μm, which achieves the purpose of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the SEM image of the original [Co(acac)2+Fe(acac)3+TEOS] / PVP composite microspheres;

[0016] Figure 2 is the diameter distribution histogram of [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres;

[0017] Figure 3This is the XRD spectrum of the CoFe2O4@SiO2 yolk@shell spherical tank;

[0018] Figure 4 This is a SEM photograph of a CoFe2O4@SiO2 yolk@shell spherical tank, which also serves as an illustration of the abstract;

[0019] Figure 5 is the diameter distribution histogram of the CoFe2O4@SiO2 yolk@shell spherical tank;

[0020] Figure 6 is the diameter distribution histogram of the yolk balls in the CoFe2O4@SiO2 yolk@shell spherical tank;

[0021] Figure 7 This is the TEM image of the CoFe2O4@SiO2 yolk@shell spherical tank;

[0022] Figure 8 This is the EDS element mapping of the CoFe2O4@SiO2 yolk@shell spherical tank. DETAILED DESCRIPTION

[0023] The cobalt acetylacetonate Co(acac)2, iron acetylacetonate Fe(acac)3, tetraethyl orthosilicate TEOS, polyvinylpyrrolidone PVP (molecular weight 35000), N,N-dimethylformamide DMF, dichloromethane CH2Cl2, activated carbon particles, and ammonium bifluoride NH4HF2 used in the present invention are all commercially available analytically pure products; the glassware, crucible, and equipment used are commonly used instruments and equipment in laboratories.

[0024] Example: Weigh 0.1296g Co(acac)2 and 0.3532g Fe(acac)3 and add them to 4.0g DMF, stir thoroughly for 30 minutes to dissolve to obtain solution I, add 0.8g PVP to 3.5g CH2Cl2, stir thoroughly for 30 minutes to dissolve to obtain solution II, mix solution I and solution II, add 0.5g TEOS, and stir magnetically for 18 hours to obtain an electrospray solution; Using uniaxial electrospray ionization technology, the electrospray solution is injected into a 10mL syringe with a No. 4.5 stainless steel syringe needle, a copper wire is inserted into the electrospray solution and connected to the positive terminal of a high-voltage DC power supply, the stainless steel syringe needle is at an angle of 30° to the horizontal plane, and an aluminum foil at an angle of 60° to the horizontal plane is used as a receiving device and is grounded, the needle is kept perpendicular to the aluminum foil and the distance is 15cm, and another copper wire is used to connect the aluminum foil to the zero potential terminal of the high-voltage DC power supply. The electrospraying voltage was 16.5 kV, the room temperature was 20-25 ° C, and the relative humidity was 30%-50%. As the solvent evaporated, [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres were obtained on the aluminum foil. NH4HF2 was used as the fluorine source and activated carbon particles were used as the auxiliary reducing agent. 0.3 g of [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres were placed in a 10 mL crucible. 3.0 g NH4HF2 was placed at the bottom of a 50mL crucible, and 10g of activated carbon particles were spread on it. Then, the 10mL small crucible was placed in the middle of the 50mL large crucible. After the lid of the large crucible was closed, the two crucibles were placed in a muffle furnace. The temperature was raised to 600℃ at a heating rate of 2℃ / min and kept at this temperature for 4h. Then, the temperature was lowered to 200℃ at a cooling rate of 2℃ / min. After that, the furnace was naturally cooled to room temperature to obtain CoFe2O4@SiO2 yolk@shell spherical jars. The [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres have good spherical morphology, as shown in Figure 2. Figure 1 As shown in Figure 2, the diameter distribution of the original [Co(acac)2+Fe(acac)3+TEOS] / PVP composite microspheres is uniform. The diameter is tested for normal distribution using the Shapiro-Wilk method. At a confidence level of 95%, the diameter distribution belongs to normal distribution, with an average diameter of 1.53±0.01μm. Figure 2 As shown in the figure, the CoFe2O4@SiO2 yolk@shell spherical jar has good crystallinity. The d value and relative intensity of its diffraction peak are consistent with the d value and relative intensity listed in the PDF standard card (22-1086) of CoFe2O4, indicating that the crystalline substance is CoFe2O4, which belongs to the cubic crystal system. There is a broad diffraction peak at about 22.5°, which is the diffraction peak of amorphous SiO2. Figure 3As shown in the figure; the CoFe2O4@SiO2 yolk@shell spherical tank has a distinct yolk-shell structure, with a clear gap between the yolk and the shell, and an opening on the shell. Figure 4 As shown in Figure 2, the diameter distribution of the CoFe2O4@SiO2 yolk@shell spherical tank is uniform. The diameter is tested for normal distribution using the Shapiro-Wilk method. At a confidence level of 95%, the diameter distribution belongs to normal distribution, with an average diameter of 1.42±0.01μm. Figure 5 As shown in the figure, the diameter of the yolk balls in the CoFe2O4CoFe2O4@SiO2 yolk@shell spherical jar is evenly distributed. The diameter is tested for normal distribution using the Shapiro-Wilk method. At a confidence level of 95%, the diameter distribution belongs to normal distribution, with an average diameter of 1.05±0.02μm. Figure 6 As shown; CoFe2O4@SiO2 yolk@shell spherical tank has obvious yolk-eggshell structure, see Figure 7 As shown in the figure, Co and Fe elements are evenly distributed in the core spherical area of ​​the yolk@shell spherical tank, indicating that the yolk ball is CoFe2O4. At the same time, Si and O elements are evenly distributed in the surface area of ​​the entire CoFe2O4@SiO2 yolk@shell spherical tank, indicating that the outer layer of the yolk@shell spherical tank is SiO2. Figure 8 shown.

[0025] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. Manufacturing technology of CoFe2O4@SiO2 yolk@shell spherical tank, characterized in that: The single-axis electrospray ionization technology, fluorination technology and high-temperature oxidation roasting technology are combined, polyvinyl pyrrolidone (PVP) is used as a polymer template, N,N-dimethylformamide (DMF) and dichloromethane (CH2Cl2) are used as solvents, ammonium bifluoride (NH4HF2) is used as a fluorination agent, and activated carbon particles are used as an auxiliary reducing agent to prepare a product, namely, CoFe2O4@SiO2 egg yolk@shell spherical tank. The steps are as follows: (1) Preparation of electrospray solution The cobalt source used was cobalt acetylacetonate Co(acac)2, the iron source used was iron acetylacetonate Fe(acac)3, the silicon source used was tetraethyl orthosilicate TEOS, the polymer template used was polyvinylpyrrolidone PVP, and N,N-dimethylformamide DMF and dichloromethane CH2Cl2 were used as solvents. 0.1296 g of Co(acac)2 and 0.3532 g of Fe(acac)3 were weighed and added to 4.0 g of DMF, and the mixture was stirred for 30 minutes to dissolve to obtain solution I. 0.8 g of PVP was added to 3.5 g of CH2Cl2, and the mixture was stirred for 30 minutes to dissolve to obtain solution II. After mixing solution I and solution II, 0.5 g of TEOS was added, and the mixture was magnetically stirred for 18 hours to obtain an electrospray solution. (2) Preparation of [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres Using uniaxial electrospray ionization technology, the electrospray solution is injected into a 10mL syringe with a No. 4.5 stainless steel syringe needle. A copper wire is inserted into the electrospray solution and connected to the positive terminal of a high-voltage direct current power supply. The angle between the stainless steel syringe needle and the horizontal plane is 30 degrees. Aluminum foil at an angle of 60 degrees to the horizontal plane is used as a receiving device and is grounded. The needle and the aluminum foil are kept perpendicular and 15 cm apart. Another copper wire is used to connect the aluminum foil to the zero-potential terminal of the high-voltage direct current power supply. The electrospray voltage is 16.5kV. The room temperature is 20-25°C and the relative humidity is 30%-50%. Electrospraying is carried out. As the solvent evaporates, [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres are obtained on the aluminum foil. (3) Preparation of CoFe2O4@SiO2 yolk@shell spherical tank Using NH4HF2 as fluorine source and activated carbon particles as auxiliary reducing agent, 0.3g [Co(acac)2+Fe(acac)3+TEOS] / PVP original composite microspheres were placed in a 10mL crucible, and 3.0g NH4HF2 was placed at the bottom of a 50mL crucible and covered with 10g of activated carbon particles. Then the 10mL small crucible was placed in the middle of the 50mL large crucible. After covering the large crucible with a lid, the two crucibles were placed in a muffle furnace. The temperature was increased to 600℃ at a heating rate of 2℃ / min and kept warm for 4h. Then the temperature was cooled to 200℃ at a cooling rate of 2℃ / min. After that, the furnace body was naturally cooled to room temperature to obtain CoFe2O4@SiO2 yolk@shell spherical jars. The shell SiO2 was amorphous, and the core yolk balls had good crystallinity and belonged to the cubic crystal system. The average diameter of the CoFe2O4@SiO2 yolk@shell spherical jars was 1.42±0.01μm, and the average diameter of the yolk balls CoFe2O4 was 1.05±0.02μm.

2. The manufacturing technology of the CoFe2O4@SiO2 yolk@shell spherical tank according to claim 1 is characterized in that: The polymer template agent is polyvinyl pyrrolidone with a molecular weight Mr=35000.

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