Method for preparing ceramic microspheres by combining photocured ceramic precursor and microfluidic technology

Abstract

The application discloses a preparation method of ceramic microspheres combining a photocured ceramic precursor and microfluidic technology and application thereof. The specific preparation method is as follows: a photocured polymer ceramic precursor solution is used as a main raw material, a polymer additive is supplemented, and microfluidic technology is combined to prepare liquid droplets with uniform sizes, and then the liquid droplets are cured and shaped by ultraviolet light curing to obtain polymer microspheres. The polymer microspheres are sequentially subjected to degumming, pyrolysis and sintering in a high temperature and inert atmosphere to obtain ceramic microspheres. The ceramic microspheres have the characteristics of uniform diameter, good sphericity and size controllability, are suitable for batch production, and have wide application prospects in the national defense and civil markets.

Description

Technical Field

[0001] This invention relates to the field of ceramic microsphere technology, and more specifically to a method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology. Background Technology

[0002] Ceramic microspheres are spherical particulate materials with excellent dispersibility, thermal insulation properties, chemical stability, and electromagnetic shielding performance. In recent years, ceramic microspheres have attracted widespread attention in engineering fields such as structural materials, nuclear fuels, thermal barrier coatings, thermal insulation materials, and electromagnetic shielding materials, and have broad application prospects in both defense and civilian markets. The performance of ceramic microspheres mainly depends on their size and composition; therefore, there is an urgent need to develop a method that can precisely control the size and composition of ceramic microspheres.

[0003] Polymer ceramic precursors are a novel type of ceramic raw material with good stability and processability. Combined with traditional processing and molding techniques, they can be used to prepare materials such as ceramic fibers, ceramic microspheres, and nano-coatings. Furthermore, by adjusting the types of small-molecule monomers that make up the precursor, hybridization of multiple elements at the molecular scale can be achieved, allowing for precise control of the microstructure of ceramic materials. Photocurable ceramic precursors are polymers with photoactive groups developed based on this technology; their preparation method can be found in patent CN117887083A. Photocurable ceramic precursors can transform from liquid to solid through a light-initiated curing reaction. The curing reaction can be completed quickly at room temperature, facilitating rapid sample setting.

[0004] Currently, the main methods for preparing ceramic microspheres include emulsion methods, spray drying methods, solvothermal synthesis methods, and plasma sintering methods. However, the microspheres obtained by these methods have uneven size distributions and poor adjustability. Microfluidic technology can be used to prepare droplets with uniform size, and the droplet size can be flexibly controlled by the channel size of the microfluidic chip, the internal and external phase flow rates, and additives. Combined with photocurable ceramic precursors as a key raw material, ceramic microspheres with uniform and adjustable diameters and size distributions in the range of 100-500 micrometers can be prepared. Summary of the Invention

[0005] One of the objectives of this invention is to address the shortcomings of existing technologies by providing a method for preparing ceramic microspheres based on photocurable ceramic precursors and microfluidic technology. This method can overcome the problem of uneven ceramic size in traditional methods and can obtain ceramic microspheres with uniform and controllable size.

[0006] A second objective of this invention is to provide a ceramic microsphere whose chemical composition can be precisely controlled at the nanoscale.

[0007] The third objective of this invention is to provide applications of the aforementioned ceramic microsphere materials in related fields such as protective coating fillers and electromagnetic shielding.

[0008] The technical solution adopted in this invention is:

[0009] A method for preparing ceramic microspheres based on photocurable ceramic precursors and microfluidic technology includes the following steps: First, a polymer ceramic precursor solution is prepared. Then, the precursor solution is mixed with a suitable type of polymer solution to obtain an internal phase solution. Subsequently, the internal phase solution and the external phase solution are loaded into different syringes, and spherical droplets are obtained by injection through a syringe pump and a microfluidic channel. During the collection process, the droplets are cured by ultraviolet light. After filtering to remove the collected liquid, the obtained microspheres are placed in a high-temperature oven for curing. The cured microspheres are then placed in a high-temperature furnace and subjected to debinding, pyrolysis, and sintering treatments in air or an inert atmosphere to obtain ceramic microspheres.

[0010] This invention provides a method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology, the preparation method comprising the following steps:

[0011] (1) First, a photocurable ceramic precursor solution is synthesized and a polymer solution of a certain concentration is prepared. The two are then mixed in a certain proportion to obtain a homogeneous solution A.

[0012] (2) Add crosslinking agent and photoinitiator to solution A in sequence, and stir until homogeneous to obtain a dispersed phase solution;

[0013] (3) Select a suitable solvent as the continuous phase solution;

[0014] (4) The dispersed phase and the continuous phase are mixed in a cross-shaped microfluidic device by injecting the sample through an injection pump. The dispersed phase is sheared into polymer droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0015] (5) The collected polymer microspheres are transferred into an oven to remove the organic solvent from the polymer microspheres. Then, the microspheres are subjected to high-temperature curing, debinding, pyrolysis and sintering to obtain the ceramic microspheres.

[0016] This invention utilizes microfluidic technology to stably prepare ceramic microspheres with uniform size. In the preparation method, when two immiscible liquid phases are mixed in a microfluidic device, the slower-flowing dispersed phase forms droplets under the shearing action at the interface. Therefore, the channel structure of the microfluidic device, the flow velocities of the two phases, the fluid viscosity, and the surfactant used all affect the formation and properties of the droplets. This invention selects a cross-shaped microchannel, which ensures uniform and stable microsphere size. Furthermore, by adjusting the flow velocities of the two phases, the fluid viscosity, and the interfacial tension, the microfluidic technology allows for precise control of the microsphere preparation process, enabling the regulation of the microsphere product properties.

[0017] Preferably, the photocurable ceramic precursor mentioned in step (1) refers to an oligomer containing zirconium, silicon, and acryloyloxy groups. It can be used for room temperature photocuring rapid prototyping, forming a photocurable coating through ultraviolet light crosslinking reaction, and can be converted into a ceramic coating after high-temperature pyrolysis. This photocurable ceramic precursor has the characteristics of rapid curing at room temperature and low energy consumption, and can be used to prepare ceramic coatings, ceramic matrix composites, and 3D printed ceramic materials. The specific synthesis method of this photocurable ceramic precursor can be found in patent CN117887083A.

[0018] Preferably, the polymer solution in step (1) is one or more of the following: polyvinylpyrrolidone solution, polyvinyl alcohol solution, polyethylene glycol solution, polymethyl methacrylate solution, phenolic resin solution, polystyrene solution, polyether solution, and polyvinyl butyral solution.

[0019] More preferably, the polymer solution in step (1) is one or more of polyvinylpyrrolidone solution, polymethyl methacrylate solution, and phenolic resin solution. The polymer solution can both assist in microsphere formation and supplement the carbon source.

[0020] Preferably, the polymer solution in step (1) has a mass fraction of 5-10%, and the ratio of polymer to photocurable ceramic precursor is 1:2-1:4.

[0021] Preferably, the crosslinking agent in step (2) is one or more of pentaerythritol tetraacrylate, tripropylene glycol diacrylate, divinylbenzene, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and 1,6-hexanediol diacrylate.

[0022] More preferably, the crosslinking agent in step (2) is one or more of pentaerythritol tetraacrylate, tripropylene glycol diacrylate, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, and 1,6-hexanediol diacrylate.

[0023] Preferably, the mass ratio of the crosslinking agent to the photocurable ceramic precursor in step (2) is 1:2 to 2:1. Under ultraviolet light irradiation, the photoinitiator initiates a crosslinking reaction to form a polymer network.

[0024] Preferably, the photoinitiator in step (2) is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione, 2,2'-dihydroxy-4-methoxybenzophenone, and 1-hydroxycyclohexylphenyl ketone.

[0025] More preferably, the photoinitiator in step (2) is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenyl ketone.

[0026] Preferably, the amount of initiator used is 2-5 wt% of the total mass of the crosslinking agent and the solid content of the photocurable ceramic precursor. After ultraviolet irradiation, free radicals are released, thereby initiating the crosslinking reaction.

[0027] Preferably, the continuous phase solution in step (3) is one or more of a nonpolar or low-polar solvent such as liquid paraffin, dimethyl silicone oil, dodecane, perfluoronaphthalene and soybean oil.

[0028] More preferably, the continuous phase solution in step (3) is one or more of liquid paraffin, dimethyl silicone oil, and soybean oil. The continuous phase and the dispersion are immiscible, which is beneficial to the formation of droplets in the cross-shaped microchannel.

[0029] Preferably, the specific method for mixing the dispersed phase and the continuous phase in the cross-shaped microfluidic device in step (4) is as follows: First, the dispersed phase is introduced into the device from one end of the cross-shaped microchannel. After it fills the entire channel, the continuous phase is introduced from the two ports in the vertical direction, so that the two phases are mixed in the cross-shaped microfluidic device. The dispersed phase is sheared into polymer droplets in the cross-shaped microchannel and finally collected at the other end port. The optimized ceramic microsphere preparation flow chart is shown below. Figure 1 As shown.

[0030] Preferably, when the dispersed phase and the continuous phase are mixed in the cross-shaped microfluidic device in step (4), the flow rate ratio of the two phases is 1:5-1:20. Under this flow rate ratio, monodisperse, uniformly shaped spherical polymer microspheres can be stably prepared, and the microsphere particle size can be 80-800 μm.

[0031] More preferably, in step (4), the flow rate of the dispersed phase is 1-3 mL / h, and the flow rate of the continuous phase is 10-20 mL / h; when the flow rate ratio of the two phases is 3:15, 1:10, 1:15 and 1:20, monodisperse, uniformly shaped spherical ceramic microspheres with particle sizes of approximately 188 μm, 129 μm, 113 μm and 90 μm can be stably prepared.

[0032] More preferably, the curing temperature in the high-temperature oven is in the range of 200-250 degrees Celsius, and the curing time is 1-4 hours.

[0033] Preferably, the debinding and pyrolysis temperatures are in the range of 300-600 degrees Celsius, and the debinding and pyrolysis times are 2-8 hours.

[0034] More preferably, the sintering temperature is in the range of 1100-1400 degrees Celsius, and the sintering time is about 1-4 hours.

[0035] The present invention also provides a ceramic microsphere, which is prepared by the above-described method of combining photocurable ceramic precursor and microfluidic technology.

[0036] The present invention also provides an application of the above-mentioned ceramic microspheres in the preparation of coating fillers or electromagnetic shielding.

[0037] The beneficial effects of this invention are: it provides a simple and efficient method for preparing monodisperse ceramic microspheres. The ceramic microspheres prepared in this way exhibit uniform size and adjustable size and composition. Therefore, the hollow ceramic microspheres prepared by this invention have broad application prospects in the fields of protective coating fillers and electromagnetic shielding materials. Attached Figure Description

[0038] Figure 1 A process flow diagram for the preparation of ceramic microspheres using microfluidics.

[0039] Figure 2 This is a SEM image of the ceramic microspheres prepared in Example 1.

[0040] Figure 3 This is a SEM image of the ceramic microspheres prepared in Example 2.

[0041] Figure 4 This is a SEM image of the ceramic microspheres prepared in Example 3.

[0042] Figure 5 This is a SEM image of the ceramic microspheres prepared in Example 4.

[0043] Figure 6 This is a SEM image of the ceramic microspheres prepared in Example 5.

[0044] Figure 7 The image shows the X-ray diffraction pattern of the ceramic microspheres prepared in Example 5.

[0045] Figure 8 This is a SEM image of the ceramic microspheres prepared in Example 6.

[0046] Figure 9 This is a SEM image of the ceramic microspheres prepared in Example 7.

[0047] Figure 10 This is a SEM image of the ceramic microspheres prepared in Example 8.

[0048] Figure 11 X-ray diffraction patterns of ceramic microspheres prepared in Examples 2, 3, 4, 6 and 8. Detailed Implementation

[0049] The present invention will be further explained and described below with reference to specific embodiments.

[0050] Example 1:

[0051] A ceramic microsphere material, the preparation method of which includes the following steps:

[0052] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use. 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:4 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the total mass of crosslinking agent and photocurable ceramic precursor solids) were added sequentially. After stirring evenly, a dispersed phase solution was obtained.

[0053] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 10 mL / h and 2 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0054] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 200 degrees Celsius for 2 hours to cure.

[0055] 4) The cured microspheres are placed in a tube furnace under argon protection at 600 degrees Celsius for debinding and pyrolysis for 2 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1400 degrees Celsius for sintering for 4 hours to obtain ceramic microspheres with a diameter of approximately 635 micrometers. A photograph of the microspheres is shown below. Figure 2 As shown.

[0056] Example 2:

[0057] A ceramic microsphere material, the preparation method of which includes the following steps:

[0058] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use; 0.5 g of phenolic resin was added to 4.5 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:4 and mixed evenly. Then, 1 g of trimethylolpropane trimethacrylate and 5 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the total solid content of the crosslinking agent and the photocurable ceramic precursor) were added sequentially and stirred evenly to obtain a dispersed phase solution.

[0059] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 10 mL / h and 2 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0060] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 4 hours to cure.

[0061] 4) The cured microspheres are placed in a tube furnace under argon protection at 300 degrees Celsius for 2 hours to remove the binder and pyrolyze, thus removing the organic matter from the microspheres. Then, the furnace temperature is increased to 1100 degrees Celsius for sintering for 2 hours to obtain ceramic microspheres with a diameter of approximately 660 micrometers. A photograph of the microspheres is shown below. Figure 3 As shown.

[0062] Example 3:

[0063] A ceramic microsphere material, the preparation method of which includes the following steps:

[0064] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use; 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:4 and mixed evenly. Then, 1 g of polyethylene glycol dimethacrylate and 5 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide were added sequentially based on the total mass of crosslinking agent and photocurable ceramic precursor solid content. After stirring evenly, a dispersed phase solution was obtained.

[0065] 2) Liquid paraffin was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 10 mL / h and 2 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0066] 3) Select liquid paraffin as the collecting liquid. Transfer the collected polymer microspheres into an oven and heat to 250 degrees Celsius to cure for 2 hours.

[0067] 4) The cured microspheres were placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 8 hours to remove organic matter from the microspheres. Then, the furnace temperature was increased to 1400 degrees Celsius for sintering for 2 hours to obtain ceramic microspheres with a diameter of approximately 557 micrometers. A photograph of the microspheres is shown below. Figure 4 As shown.

[0068] Example 4:

[0069] A ceramic microsphere material, the preparation method of which includes the following steps:

[0070] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use. 0.25 g of polyvinylpyrrolidone was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a polyvinylpyrrolidone solution. The above polyvinylpyrrolidone solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:2 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the total mass of crosslinking agent and photocurable ceramic precursor solids) were added sequentially and stirred evenly to obtain a dispersed phase solution.

[0071] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 10 mL / h and 2 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0072] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 1 hour to cure.

[0073] 4) The cured microspheres are placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 2 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1400 degrees Celsius for sintering for 2 hours to obtain ceramic microspheres with a diameter of approximately 609 micrometers. A photograph of the microspheres is shown below. Figure 5 As shown.

[0074] Example 5:

[0075] A ceramic microsphere material, the preparation method of which includes the following steps:

[0076] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use. 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:2 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the total mass of crosslinking agent and photocurable ceramic precursor solids) were added sequentially. After stirring evenly, a dispersed phase solution was obtained.

[0077] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 15 mL / h and 3 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0078] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 1 hour to cure.

[0079] 4) The cured microspheres are placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 4 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1100 degrees Celsius for sintering for 4 hours to obtain ceramic microspheres with a diameter of approximately 188 micrometers. A photograph of the microspheres is shown below. Figure 6 As shown.

[0080] Example 6:

[0081] A ceramic microsphere material, the preparation method of which includes the following steps:

[0082] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use; 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:2 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wr% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the total mass of crosslinking agent and photocurable ceramic precursor solids) were added sequentially and stirred evenly to obtain a dispersed phase solution.

[0083] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 10 mL / h and 1 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0084] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 2 hours to cure.

[0085] 4) The cured microspheres are placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 4 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1400 degrees Celsius for sintering for 1 hour to obtain ceramic microspheres with a diameter of approximately 129 micrometers. A photograph of the microspheres is shown below. Figure 8 As shown.

[0086] Example 7:

[0087] A ceramic microsphere material, the preparation method of which includes the following steps:

[0088] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use. 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:2 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the mass of the reactant monomers) were added sequentially and stirred evenly to obtain a dispersed phase solution.

[0089] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 15 mL / h and 1 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0090] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 2 hours to cure.

[0091] 4) The cured microspheres are placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 4 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1400 degrees Celsius for sintering for 2 hours to obtain ceramic microspheres with a diameter of approximately 113 micrometers. A photograph of the microspheres is shown below. Figure 9 As shown.

[0092] Example 8:

[0093] A ceramic microsphere material, the preparation method of which includes the following steps:

[0094] 1) Preparation of the internal phase solution. First, referring to patent CN117887083A, a photocurable ceramic precursor solution was synthesized for later use. 0.25 g of phenolic resin was added to 4.75 g of ethylene glycol ethyl ether and dissolved thoroughly to obtain a phenolic solution. The above phenolic resin solution and the photocurable ceramic precursor solution were added at a solid content mass ratio of 1:2 and mixed evenly. Then, 0.5 g of trimethylolpropane trimethacrylate, 0.5 g of polyethylene glycol dimethacrylate, and 2 wt% of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (based on the mass of the reactant monomers) were added sequentially and stirred evenly to obtain a dispersed phase solution.

[0095] 2) Dimethyl silicone oil was selected as the continuous phase solution. The continuous phase and dispersed phase solutions were loaded into the syringe of the injection pump and injected through the injection pump. The flow rates of the continuous phase and dispersed phase were set to 20 mL / h and 1 mL / h, respectively. They were mixed in a cross-shaped microfluidic device. The dispersed phase solution was sheared into droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres.

[0096] 3) Dimethyl silicone oil was selected as the collecting liquid. The collected polymer microspheres were transferred into an oven and heated to 250 degrees Celsius for 2 hours to cure.

[0097] 4) The cured microspheres are placed in a tube furnace under argon protection at 500 degrees Celsius for debinding and pyrolysis for 6 hours to remove organic matter from the microspheres. Then, the furnace temperature is increased to 1400 degrees Celsius for sintering for 1 hour to obtain ceramic microspheres with a diameter of about 90 micrometers. A picture of the actual product is shown below. Figure 10 As shown.

[0098] Figure 7 The X-ray diffraction pattern of the ceramic microspheres prepared in Example 5 is shown below. Figure 11 X-ray diffraction patterns of ceramic microspheres prepared in Examples 2, 3, 4, 6 and 8.

[0099] In summary, the beneficial effects of this invention are: it provides a simple and efficient method for preparing monodisperse ceramic microspheres. The ceramic microspheres prepared in this way exhibit uniform size and adjustable size and composition. Therefore, the hollow ceramic microspheres prepared by this invention have broad application prospects in the fields of protective coating fillers and electromagnetic shielding materials.

[0100] The above embodiments are preferred implementation methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the essence and principle of the present invention should be considered as equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology, characterized in that, The method includes the following steps: (1) Synthesize the photocurable ceramic precursor solution and prepare the polymer solution. Mix the two in proportion to obtain a homogeneous solution A. (2) Add crosslinking agent and photoinitiator to solution A in sequence, and stir until homogeneous to obtain a dispersed phase solution; (3) Select a suitable solvent as the continuous phase solution; (4) The dispersed phase and the continuous phase are mixed in a cross-shaped microfluidic device by injecting the sample through an injection pump. The dispersed phase is sheared into polymer droplets in the cross-shaped microchannel and then cured by ultraviolet light to obtain polymer microspheres. (5) The collected polymer microspheres are transferred into an oven to remove the organic solvent from the polymer microspheres. Then, the microspheres are subjected to high-temperature curing, debinding, pyrolysis and sintering to obtain the ceramic microspheres.

2. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The photocurable ceramic precursor in step (1) is an oligomer containing zirconium, silicon and acryloyloxy groups; the polymer solution is one or more of polyvinylpyrrolidone solution, polymethyl methacrylate solution and phenolic resin solution.

3. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The crosslinking agent in step (2) is one or more of pentaerythritol tetraacrylate, tripropylene glycol diacrylate, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, and 1,6-hexanediol diacrylate; the photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenyl ketone.

4. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The continuous phase in step (3) is one or more of liquid paraffin, dimethyl silicone oil and soybean oil.

5. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The polymer solution in step (1) has a mass fraction of 5-10%, wherein the ratio of polymer to solid content of photocurable ceramic precursor is 1:2-1:4; the crosslinking agent to solid content of photocurable ceramic precursor in step (2) has a mass ratio of 1:2-2:1; the photoinitiator used in step (2) is 2-5 wt% of the total mass of crosslinking agent and solid content of photocurable ceramic precursor.

6. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The specific method for mixing the dispersed phase and the continuous phase in the cross-shaped microfluidic device in step (4) is as follows: First, the dispersed phase is introduced into the device from one end of the cross-shaped microchannel. After it fills the entire channel, the continuous phase is introduced from the two ports in the vertical direction, so that the two phases are mixed in the cross-shaped microfluidic device. The dispersed phase is sheared into polymer droplets in the cross-shaped microchannel and finally collected at the other end port.

7. A method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 4, characterized in that, In step (4), when the dispersed phase and the continuous phase are mixed in the cross-shaped microfluidic device, the flow rate ratio of the two phases is 1:5-1:

20. Under this flow rate ratio, monodisperse, uniformly shaped spherical polymer microspheres can be stably prepared, with microsphere particle sizes ranging from 80 to 800 μm. The flow rate of the dispersed phase is 1-3 mL / h, and the flow rate of the continuous phase is 10-20 mL / h. When the flow rate ratio of the two phases is 3:15, 1:10, 1:15, and 1:20, monodisperse, uniformly shaped spherical ceramic microspheres can be stably prepared with particle sizes of 188 μm, 129 μm, 113 μm, and 90 μm, respectively.

8. The method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology according to claim 1, characterized in that, The high-temperature curing step (5) has a curing temperature of 200-250 degrees Celsius and a curing time of 1-4 hours; the debinding and pyrolysis temperature is in the range of 300-600 degrees Celsius and the debinding and pyrolysis time is 2-8 hours; the sintering temperature is in the range of 1100-1400 degrees Celsius and the sintering time is 1-4 hours.

9. Ceramic microspheres obtained by the method for preparing ceramic microspheres by combining photocurable ceramic precursors and microfluidic technology as described in any one of claims 2 to 8.

10. The application of the ceramic microspheres of claim 9 in the preparation of coating fillers or electromagnetic shielding.

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