Modified inorganic powder, and preparation method and application thereof

Abstract

The application relates to the material field and provides a modified inorganic powder and a preparation method and application thereof.The method comprises the following steps: carrying out hydroxylation pretreatment on inorganic powder at a first temperature to obtain hydroxylated inorganic powder; stirring the hydroxylated inorganic powder in a graphene oxide dispersion liquid at a second temperature, and adding a crosslinking agent to obtain graphene oxide coated inorganic powder; and carrying out post-treatment on the graphene oxide coated inorganic powder at a third temperature to obtain modified inorganic powder; the first, second and third temperatures are all not higher than 80 DEG C. The application does not require harsh high-temperature and high-pressure conditions, the process conditions are mild and simple to operate, the coating rate of the prepared product reaches more than 95%, a covalent bond is formed between the coated inorganic powder and the graphene oxide coating layer, the coating firmness is good, and the product has the mechanical enhancement characteristics of inorganic powder and the corrosion resistance, antibacterial property and heat conduction function of graphene oxide.

Description

Technical Field

[0001] This application relates to the field of materials, and more particularly to a modified inorganic powder, its preparation method, and its application. Background Technology

[0002] Inorganic powders are widely used as fillers or functional additives in plastics, rubber, coatings, and new energy materials. However, their strong surface polarity, poor compatibility with organic matrices, and tendency to agglomerate limit the improvement of material performance. Surface modification can improve the dispersibility and interfacial bonding of inorganic powders.

[0003] Traditional processes for coating and modifying inorganic powders with graphene oxide mostly employ physical adsorption methods, using electrostatic attraction or hydrogen bonding to achieve the bonding between graphene oxide and inorganic powders. However, this coating and modification process generally suffers from problems such as easy peeling off of the coating layer and poor uniformity. Furthermore, some chemical coating methods require the use of strong oxidants or high-temperature conditions, which not only consumes a lot of energy but also damages the structural integrity of graphene oxide.

[0004] Therefore, researching and developing a technical solution for coating inorganic powders with graphene oxide that provides uniform coating, strong bonding, and mild processing conditions is of great significance for expanding the high-end applications of inorganic powders. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a modified inorganic powder, its preparation method and application, which aims to solve the problems of weak coating, poor uniformity and complicated process of traditional graphene oxide coating of inorganic powder.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a method for preparing modified inorganic powder, comprising: S1. Under the first temperature condition, the inorganic powder is subjected to hydroxylation pretreatment to obtain hydroxylated inorganic powder; S2. Under the second temperature condition, the hydroxylated inorganic powder is added to the graphene oxide dispersion and stirred. During the stirring process, a crosslinking agent is added to form a graphene oxide coating layer on the surface of the hydroxylated inorganic powder in situ, thus obtaining graphene oxide coated inorganic powder. S3. Under the third temperature condition, the graphene oxide-coated inorganic powder is post-treated to obtain modified inorganic powder. The first, second, and third temperatures shall not exceed 80 ℃.

[0007] In some implementations, the first temperature is 60-80 °C, the second temperature is 50-70 °C, and the third temperature is 60-80 °C.

[0008] In some implementations, step S1 includes: Inorganic powder is dispersed in a dispersion solvent to obtain an inorganic powder dispersion. Add silane coupling agent to inorganic powder dispersion, stir for 2-4 h, then centrifuge, wash and dry to obtain hydroxylated inorganic powder; The inorganic powder is selected from at least one of calcium carbonate, silicon dioxide, kaolin, aluminum hydroxide, boron nitride, and titanium dioxide, with a particle size of 0.1~50 µm; the dispersion concentration of the inorganic powder dispersion is 50~100 g / L; and the amount of silane coupling agent added is 1%~3% of the mass of the inorganic powder.

[0009] In some embodiments, the preparation steps of the graphene oxide dispersion are as follows: Graphene oxide was added to deionized water and stirred in an ice bath for 20-30 minutes to obtain the first dispersion. The first dispersion was subjected to intermittent ultrasonic treatment for 30-60 min to obtain the second dispersion; The second dispersion was subjected to gradient centrifugation to obtain a graphene oxide dispersion. The graphene oxide dispersion has a concentration of 0.1–1 mg / mL and a pH of 8–10; the intermittent ultrasonic treatment has an ultrasonic power of 300–500 W; the gradient centrifugation treatment includes low-speed centrifugation, medium-speed centrifugation, and high-speed centrifugation. The low-speed centrifugation speed is 2000–300 rpm for 15–25 min, the medium-speed centrifugation speed is 5000–7000 rpm for 20–30 min, and the high-speed centrifugation speed is 8000–12000 rpm for 20–30 min.

[0010] In some embodiments, in step S2, the mass ratio of hydroxylated inorganic powder to graphene oxide dispersion is 10~50:1; the stirring rate of the stirring treatment is 300~500 r / min, and the stirring time is 3~6 h.

[0011] In some embodiments, the crosslinking agent is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methyl iodide, and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide methyl p-toluenesulfonate; the amount of crosslinking agent added is 5% to 10% of the mass of graphene oxide.

[0012] In some embodiments, in step S3, the graphene oxide-coated inorganic powder is washed and vacuum dried to obtain modified inorganic powder; the vacuum degree of vacuum drying is -0.09 MPa to -0.1 MPa, and the vacuum drying time is 8 to 12 h.

[0013] Secondly, embodiments of this application provide a modified inorganic powder, which is prepared by the method for preparing modified inorganic powder according to the first aspect; The modified inorganic powder includes hydroxylated inorganic powder and a graphene oxide coating layer on the surface of the hydroxylated inorganic powder. The hydroxylated inorganic powder and the graphene oxide coating layer are bonded by covalent bonds, and the coating rate is ≥95%.

[0014] In some embodiments, the oxygen content of the graphene oxide coating is 20-40 at%, the sheet size is 100-500 nm, and the thickness of the graphene oxide coating is 5-50 nm.

[0015] Thirdly, the embodiments of this application also provide the application of the modified inorganic powder of the first aspect in the preparation of plastics, coatings, rubber, and new energy materials.

[0016] Compared with the prior art, the beneficial effects of the technical solution provided in this application embodiment include at least the following: the preparation method of modified inorganic powder provided in this application embodiment is carried out at a temperature below 80 °C, without the need for harsh high temperature and high pressure conditions. The process conditions are mild and the operation is simple, and all reagents can be recycled, making it green and environmentally friendly. Furthermore, by adopting hydroxylation pretreatment and in-situ reaction process, the coating rate of the modified inorganic powder obtained reaches more than 95%, the thickness deviation of the graphene oxide coating layer is ≤5 nm, there are no exposed inorganic powder particles, and the coating uniformity is good. Moreover, a stable and firm chemical bond is formed between the coated inorganic powder and the graphene oxide coating layer. After ultrasonic cleaning with ethanol at a power of 300 W for 100 times (30 min each time), the coating rate still remains above 90%, which is much higher than the traditional physical adsorption coating process (under the same detection conditions, the coating rate is usually below 60%). Meanwhile, the modified inorganic powder obtained by the above process combines the mechanical strengthening properties of inorganic powder with the anti-corrosion, antibacterial, and thermal conductivity functions of graphene oxide. The functional priority can be adjusted according to downstream demand, which expands the applicability of the modified inorganic powder in high-end products / industries. Detailed Implementation

[0017] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are only for explaining this application, but the implementation of this application is not limited thereto.

[0018] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this application pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; the amounts of experimental reagents used are, unless otherwise specified, the amounts used in conventional experimental operations; and the experimental methods used are, unless otherwise specified, conventional methods.

[0019] In a first aspect, embodiments of this application provide a method for preparing modified inorganic powder, comprising: S1. Under the first temperature condition, the inorganic powder is subjected to hydroxylation pretreatment to obtain hydroxylated inorganic powder; S2. Under the second temperature condition, the hydroxylated inorganic powder is added to the graphene oxide dispersion and stirred. During the stirring process, a crosslinking agent is added to form a graphene oxide coating layer on the surface of the hydroxylated inorganic powder in situ, thus obtaining graphene oxide coated inorganic powder. S3. Under the third temperature condition, the graphene oxide-coated inorganic powder is post-treated to obtain modified inorganic powder. The first, second, and third temperatures shall not exceed 80 ℃.

[0020] The modified inorganic powder preparation method provided in this application is characterized by mild process conditions, simple operation, and the recyclability of all reagents, making it environmentally friendly. The resulting modified inorganic powder achieves a coating rate of over 95% with excellent coating uniformity. Furthermore, a stable and robust chemical bond is formed between the coated inorganic powder and the graphene oxide coating layer. After 100 ultrasonic cleanings with 300 W ethanol (30 min each time), the coating rate remains above 90%, significantly higher than traditional physical adsorption coating processes (where the coating rate is typically below 60% under the same testing conditions). Simultaneously, this modified inorganic powder combines the mechanical reinforcing properties of inorganic powder with the anti-corrosion, antibacterial, and thermal conductivity functions of graphene oxide, which is of great significance for expanding the high-end applications of inorganic powders.

[0021] In some embodiments, the first temperature is 60~80°C (e.g., it can be 60°C, 70°C or 80°C, etc.), the second temperature is 50~70°C (e.g., it can be 50°C, 60°C or 70°C, etc.), and the third temperature is 60~80°C (e.g., it can be 60°C, 70°C or 80°C, etc.).

[0022] The preparation method provided in this application embodiment involves a reaction carried out at a temperature below 80 °C, without the need for harsh high-temperature and high-pressure conditions, and the process conditions are mild.

[0023] In some implementations, step S1 specifically includes: Inorganic powder is dispersed in a dispersion solvent to obtain an inorganic powder dispersion. Add silane coupling agent to inorganic powder dispersion, stir for 2-4 h, then centrifuge, wash and dry to obtain hydroxylated inorganic powder; The inorganic powder is selected from at least one of calcium carbonate, silicon dioxide, kaolin, aluminum hydroxide, boron nitride, and titanium dioxide, with a particle size of 0.1~50 µm; the dispersion concentration of the inorganic powder dispersion is 50~100 g / L; and the amount of silane coupling agent added is 1%~3% of the total mass of the inorganic powder.

[0024] Preferably, the dispersing solvent is an ethanol-water mixed solution obtained by mixing ethanol and water at a volume ratio of 1 to 3:1. This ensures the hydrolysis efficiency of the silane coupling agent while avoiding excessive agglomeration of inorganic powders.

[0025] Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550).

[0026] Preferably, the particle size of the inorganic powder is 1~20 µm.

[0027] A large number of hydroxyl groups (-OH) can be introduced onto the surface of inorganic powders through the hydrolysis reaction of silane coupling agents (such as KH550), providing reaction sites for subsequent covalent bonding with graphene oxide.

[0028] By controlling the dispersion concentration of the inorganic powder dispersion and the amount of silane coupling agent added, it is possible to ensure that the density of hydroxyl groups (-OH) introduced on the surface of the inorganic powder is moderate.

[0029] In some embodiments, the preparation steps of the graphene oxide dispersion are as follows: Graphene oxide was added to deionized water and stirred in an ice bath for 20-30 min to obtain a first dispersion. The first dispersion was then subjected to intermittent ultrasonic treatment for 30-60 min to obtain a second dispersion. The second dispersion was then subjected to gradient centrifugation to obtain a graphene oxide dispersion. The graphene oxide dispersion had a concentration of 0.1-1 mg / mL and a pH of 8-10. The intermittent ultrasonic treatment had an ultrasonic power of 300-500 W. The gradient centrifugation included low-speed centrifugation, medium-speed centrifugation, and high-speed centrifugation. The low-speed centrifugation was performed at 2000-300 rpm for 15-25 min, the medium-speed centrifugation was performed at 5000-7000 rpm for 20-30 min, and the high-speed centrifugation was performed at 8000-12000 rpm for 20-30 min.

[0030] First, stirring the graphene oxide in an ice bath environment allows deionized water molecules to fully insert between the graphene oxide sheets. The hydrophilicity of the oxygen-containing functional groups expands the interlayer spacing, weakening interlayer van der Waals forces and laying the foundation for subsequent ultrasonic exfoliation. Simultaneously, the low-temperature environment prevents localized overheating and agglomeration of the graphene oxide during dispersion, ensuring the initial dispersion state is stable. Then, intermittent ultrasonic treatment of the first dispersion utilizes the microjets and impact forces generated by ultrasonic cavitation to effectively exfoliate the stacked graphene oxide into single-layer or few-layer sheets. This avoids the continuous localized high temperatures caused by continuous ultrasonication, reducing sheet damage, fragmentation, and structural defects. While ensuring high exfoliation efficiency, this process maximizes the preservation of the lateral dimensions and structural integrity of the graphene oxide. Finally, by performing gradient centrifugation on the second dispersion, incompletely peeled thick sheets, large particle agglomerates and impurities can be effectively removed, resulting in a high-quality graphene oxide dispersion with uniform layer number and narrow particle size distribution. At the same time, small-sized fragments can be separated, improving the stability and uniformity of the dispersion, so that the obtained graphene oxide exhibits better film-forming properties, compatibility and performance repeatability in subsequent applications.

[0031] The synergistic process of ice bath stirring pretreatment, intermittent ultrasonic exfoliation, and gradient centrifugation fractionation described above can efficiently prepare a uniformly dispersed graphene oxide dispersion with a consistent number of layers and a complete structure. This graphene oxide dispersion retains its surface functional groups intact, exhibits strong electrostatic repulsion, and can remain stable in aqueous solution for extended periods without easily settling or secondary agglomeration, making it convenient for storage and subsequent use.

[0032] In practical applications, ammonia can be used to adjust the pH of the graphene oxide dispersion to 8-10. By adjusting the graphene oxide dispersion to alkalinity (pH 8-10), the ionization of carboxyl groups (-COOH) on the surface of graphene oxide can be promoted, thereby enhancing its reactivity.

[0033] In some embodiments, in step S2, the mass ratio of hydroxylated inorganic powder to graphene oxide dispersion is 10~50:1; the stirring rate of the stirring treatment is 300~500 r / min, and the stirring time is 3~6 h.

[0034] By controlling the reaction temperature and stirring rate, it can be ensured that the graphene oxide sheets are uniformly coated on the powder surface, avoiding local aggregation.

[0035] Graphene oxide (GO) has a two-dimensional sheet structure, abundant oxygen-containing functional groups, and excellent physicochemical properties. Coating it onto the surface of inorganic powders can simultaneously improve the dispersibility and upgrade the functionality of the powders.

[0036] In some embodiments, the crosslinking agent is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methyl iodide, and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide methyl p-toluenesulfonate; the amount of crosslinking agent added is 5% to 10% of the mass of graphene oxide.

[0037] The aforementioned crosslinking agent can activate the carboxyl groups on the surface of graphene oxide, causing them to undergo esterification with the hydroxyl groups on the surface of inorganic powders to form stable covalent bonds.

[0038] In some embodiments, in step S3, the graphene oxide-coated inorganic powder is washed and vacuum dried to obtain modified inorganic powder; the vacuum degree of vacuum drying is -0.09 MPa to -0.1 MPa, and the vacuum drying time is 8 to 12 h.

[0039] As an example, graphene oxide-coated inorganic powder can be washed 3 to 5 times with deionized water to remove unreacted impurities and excess crosslinking agents.

[0040] Secondly, embodiments of this application provide a modified inorganic powder, which is prepared by the method for preparing modified inorganic powder according to the first aspect; The modified inorganic powder includes hydroxylated inorganic powder and a graphene oxide coating layer on the surface of the hydroxylated inorganic powder. The hydroxylated inorganic powder and the graphene oxide coating layer are bonded by covalent bonds, and the coating rate is ≥95%.

[0041] In some embodiments, the oxygen content of the graphene oxide coating is 20-40 at%, the sheet size is 100-500 nm, and the thickness of the graphene oxide coating is 5-50 nm.

[0042] By controlling the oxygen content of the graphene oxide coating layer to be 20~40 at%, and the sheet size to be 100~500 nm, it can be ensured that the graphene oxide coating layer has sufficient functional groups for bonding reaction with inorganic powders, while avoiding uneven coating caused by excessively large sheets.

[0043] Thirdly, the embodiments of this application also provide the application of the modified inorganic powder of the first aspect in the preparation of plastics, coatings, rubber, and new energy materials.

[0044] The modified inorganic powder provided in this application can be used as a filler and functional modifier. It can reduce production costs and improve processing performance, and can also endow plastics with special functions such as high strength, flame retardancy, thermal conductivity and weather resistance. It is compatible with almost all types of thermoplastic plastics (such as polycarbonate (PC), polypropylene (PP), polyethylene terephthalate (PET) and thermosetting plastics (such as phenolic resin (PF), epoxy resin (EP), unsaturated polyester resin (UPR)).

[0045] The modified inorganic powder provided in this application can be used as a reinforcing filler, filling filler, and functional filler, and is suitable for preparing almost all rubber varieties such as natural rubber (NR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), and ethylene propylene rubber (EPDM).

[0046] The modified inorganic powder provided in this application can be used as pigments, fillers, functional modified powders, and additive powders, and is suitable for almost all types of coatings (such as architectural coatings, industrial coatings, special coatings, antibacterial coatings, etc.).

[0047] The modified inorganic powder provided in this application can be used to prepare new energy materials such as energy storage battery materials, photovoltaic materials, wind power materials, hydrogen energy materials, supercapacitor materials, geothermal power generation materials, and lithium battery separators.

[0048] This application has undergone multiple experiments, and some of the test results are presented here for reference to further describe the invention in detail. The following is a detailed description in conjunction with specific embodiments.

[0049] Example 1 The preparation steps of the modified calcium carbonate powder provided in this embodiment are as follows: S1. Hydroxylation pretreatment: 100 g of calcium carbonate powder (particle size 5 µm) was dispersed in 1 L of ethanol-water mixed solution (volume ratio of ethanol to water 2:1) to obtain calcium carbonate powder dispersion. Then, 2 g of silane coupling agent (KH550) was added to the calcium carbonate powder dispersion and stirred at 70 ℃ for 3 h. After centrifugation, the powder was washed twice with deionized water and dried at 80 ℃ for 4 h to obtain hydroxylated calcium carbonate powder.

[0050] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 20 min under ice bath conditions at a temperature below 25℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 400 W for 45 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (2000 rpm, 20 min), medium-speed centrifugation (5000 rpm, 20 min), and high-speed centrifugation (8000 rpm, 20 min) in sequence, and then the pH value was adjusted to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0051] In-situ coating reaction: The hydroxylated calcium carbonate powder obtained in step S1 was added to the graphene oxide dispersion obtained above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 60 ℃ and a stirring rate of 400 r / min. During the stirring process, 0.025 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was added to form a graphene oxide coating layer on the surface of the hydroxylated calcium carbonate powder in situ, thus obtaining graphene oxide coated calcium carbonate powder.

[0052] S3. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0053] Example 2 The preparation steps of the modified silica powder provided in this embodiment are as follows: S1. Hydroxylation pretreatment: 80 g of silica powder (particle size 10 µm) was dispersed in 1 L of ethanol-water mixed solution (ethanol to water volume ratio 3:1) to obtain silica powder dispersion. Then, 1.6 g of silane coupling agent (KH550) was added to the silica powder dispersion and stirred at 60 ℃ for 4 h. After centrifugation, the mixture was washed twice with deionized water and dried at 80 ℃ for 4 h to obtain hydroxylated silica powder.

[0054] S2. Preparation of graphene oxide dispersion: 0.4 g of graphene oxide was added to 500 mL of deionized water and stirred for 30 min in an ice bath at a temperature below 25 ℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 500 W for 30 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (3000 rpm, 15 min), medium-speed centrifugation (6000 rpm, 20 min), and high-speed centrifugation (9000 rpm, 20 min) in sequence, and then the pH value was adjusted to 8 with ammonia water to obtain a graphene oxide dispersion with a concentration of 0.8 mg / mL.

[0055] In-situ coating reaction: The hydroxylated silica powder obtained in step S1 was added to the graphene oxide dispersion prepared above (mass ratio 40:1), and the mixture was stirred for 5 h at a temperature of 50 ℃ and a stirring rate of 500 r / min. During the stirring process, 0.032 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methyl iodide was added to form a graphene oxide coating layer on the surface of the hydroxylated silica powder in situ, thus obtaining graphene oxide coated silica powder.

[0056] S3. After centrifuging the graphene oxide-coated silica powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 12 h at a temperature of 60 ℃ and a vacuum degree of -0.09 MPa to obtain modified silica powder.

[0057] Example 3 The preparation steps of the modified kaolin powder provided in this embodiment are as follows: S1. Hydroxylation pretreatment: 80 g of kaolin powder (particle size 20 µm) was dispersed in 1 L of ethanol-water mixed solution (ethanol to water volume ratio 1:1) to obtain kaolin powder dispersion. Then, 1.6 g of silane coupling agent (KH550) was added to the kaolin powder dispersion and stirred at 80 ℃ for 2 h. After centrifugation, the powder was washed 3 times with deionized water and dried at 80 ℃ for 4 h to obtain hydroxylated kaolin powder.

[0058] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 25 min in an ice bath at a temperature below 25 ℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 300 W for 60 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (2500 rpm, 20 min), medium-speed centrifugation (7000 rpm, 20 min), and high-speed centrifugation (12000 rpm, 20 min) in sequence, and then the pH value was adjusted to 10 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1.0 mg / mL.

[0059] In-situ coating reaction: The hydroxylated kaolin powder obtained in step S1 was added to the graphene oxide dispersion prepared above (mass ratio of 30:1), and the mixture was stirred for 6 h at a temperature of 60 ℃ and a stirring rate of 500 r / min. During the stirring process, 0.032 g of crosslinking agent (EDC) was added to form a graphene oxide coating layer on the surface of the hydroxylated kaolin powder in situ, thus obtaining graphene oxide coated kaolin powder.

[0060] S3. After centrifuging the graphene oxide-coated kaolin powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 12 h at a temperature of 80 ℃ and a vacuum degree of -0.08 MPa to obtain modified kaolin powder.

[0061] Example 4 The preparation steps of the modified boron nitride powder provided in this embodiment are as follows: S1. Hydroxylation pretreatment: 80 g of boron nitride (particle size 40 µm) was dispersed in 1 L of ethanol-water mixed solution (ethanol to water volume ratio 3:1) to obtain boron nitride powder dispersion. Then, 1.6 g of silane coupling agent (KH550) was added to the boron nitride powder dispersion and stirred at 70 ℃ for 2 h. After centrifugation, the powder was washed 3 times with deionized water and dried at 80 ℃ for 4 h to obtain hydroxylated boron nitride powder.

[0062] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 30 min in an ice bath at a temperature below 25 ℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 400 W for 50 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (3000 rpm, 25 min), medium-speed centrifugation (5500 rpm, 30 min), and high-speed centrifugation (8000 rpm, 30 min) in sequence, and then the pH value was adjusted to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1.0 mg / mL.

[0063] In-situ coating reaction: The hydroxylated boron nitride powder obtained in step S1 was added to the graphene oxide dispersion prepared above (mass ratio of 20:1), and the mixture was stirred for 6 h at a temperature of 60 ℃ and a stirring rate of 500 r / min. During the stirring process, 0.032 g of 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide methyl p-toluenesulfonate was added to form a graphene oxide coating layer on the surface of the hydroxylated boron nitride powder in situ, thus obtaining graphene oxide coated boron nitride powder.

[0064] S3. After centrifuging the graphene oxide-coated boron nitride powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 8 h at a temperature of 80 ℃ and a vacuum degree of -0.1 MPa to obtain modified boron nitride powder.

[0065] Comparative Example 1 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: S1. Preparation of graphene oxide dispersion: Take 0.5 g of graphene oxide and add it to 500 mL of deionized water. Sonicate at 400 W for 45 min. Adjust the pH value to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0066] In-situ coating reaction: 100 g of calcium carbonate powder (particle size of 5 µm) was added to the graphene oxide dispersion prepared above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 60 ℃ and a stirring rate of 400 r / min. During the stirring process, 0.025 g of crosslinking agent (EDC) was added to obtain graphene oxide coated calcium carbonate powder.

[0067] S2. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S1, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0068] Comparative Example 2 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: 100 g of calcium carbonate powder (particle size 5 µm) was dispersed in 1 L of ethanol-water mixed solution (ethanol to water volume ratio 2:1) to obtain calcium carbonate powder dispersion. Then, 2 g of silane coupling agent (KH550) was added to the calcium carbonate powder dispersion, and the mixture was stirred at 70 ℃ for 3 h. After centrifugation, the mixture was washed twice with deionized water and dried at 80 ℃ for 4 h to obtain modified calcium carbonate powder.

[0069] Comparative Example 3 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: S1, Hydroxylation pretreatment: Same as step S1 in Example 1.

[0070] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 20 min in an ice bath at a temperature below 25 ℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 400 W for 45 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (2000 rpm, 20 min), medium-speed centrifugation (5000 rpm, 20 min), and high-speed centrifugation (8000 rpm, 20 min) in sequence, and then the pH value was adjusted to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0071] In-situ coating reaction: The hydroxylated calcium carbonate powder obtained in step S1 was added to the graphene oxide dispersion obtained above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 90 ℃ and a stirring rate of 400 r / min. During the stirring process, 0.025 g of crosslinking agent (EDC) was added to form a graphene oxide coating layer on the surface of the hydroxylated calcium carbonate powder in situ, thus obtaining graphene oxide coated calcium carbonate powder.

[0072] S3. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0073] Comparative Example 4 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: S1, Hydroxylation pretreatment: Same as step S1 in Example 1.

[0074] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 20 min under ice bath conditions at a temperature below 25℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 400 W for 45 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion; the second dispersion was subjected to low-speed centrifugation (2000 rpm, 20 min), medium-speed centrifugation (5000 rpm, 20 min), and high-speed centrifugation (8000 rpm, 20 min) in sequence, and then the pH value was adjusted to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0075] In-situ coating reaction: The hydroxylated calcium carbonate powder obtained in step S1 was added to the graphene oxide dispersion obtained above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 60 ℃ and a stirring rate of 600 r / min. During the stirring process, 0.025 g of crosslinking agent (EDC) was added to form a graphene oxide coating layer on the surface of the hydroxylated calcium carbonate powder in situ, thus obtaining graphene oxide coated calcium carbonate powder.

[0076] S3. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0077] Comparative Example 5 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: S1, Hydroxylation pretreatment: Same as step S1 in Example 1.

[0078] S2. Preparation of graphene oxide dispersion: Take 0.5 g of graphene oxide and add it to 500 mL of deionized water. Sonicate continuously for 45 min at a power of 400 W. After sonication, adjust the pH value to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0079] In-situ coating reaction: The hydroxylated calcium carbonate powder obtained in step S1 was added to the graphene oxide dispersion obtained above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 60 ℃ and a stirring rate of 400 r / min. During the stirring process, 0.025 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was added to form a graphene oxide coating layer on the surface of the hydroxylated calcium carbonate powder in situ, thus obtaining graphene oxide coated calcium carbonate powder.

[0080] S3. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0081] Comparative Example 6 S1, Hydroxylation pretreatment: Same as step S1 in Example 1.

[0082] S2. Preparation of graphene oxide dispersion: 0.5 g of graphene oxide was added to 500 mL of deionized water and stirred for 20 min under ice bath conditions at a temperature below 25℃ to obtain the first dispersion; the first dispersion was subjected to intermittent ultrasonic treatment at a power of 400 W for 45 min (one cycle: 3 seconds on, 2 seconds off) to obtain the second dispersion. The pH value was adjusted to 9 with ammonia water to obtain a graphene oxide dispersion with a concentration of 1 mg / mL.

[0083] In-situ coating reaction: The hydroxylated calcium carbonate powder obtained in step S1 was added to the graphene oxide dispersion obtained above (mass ratio of 20:1), and the mixture was stirred for 4 h at a temperature of 60 ℃ and a stirring rate of 400 r / min. During the stirring process, 0.025 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was added to form a graphene oxide coating layer on the surface of the hydroxylated calcium carbonate powder in situ, thus obtaining graphene oxide coated calcium carbonate powder.

[0084] S3. After centrifuging the graphene oxide-coated calcium carbonate powder obtained in step S2, wash it four times with deionized water and vacuum dry it for 10 h at a temperature of 70 ℃ and a vacuum degree of -0.09 MPa to obtain modified calcium carbonate powder.

[0085] Comparative Example 7 The preparation steps of the modified calcium carbonate powder provided in this comparative example are as follows: First, 100 g of calcium carbonate powder (particle size 5 µm) was dispersed in 400 mL of deionized water and stirred at high speed for 30 min at room temperature to fully wet and disperse the calcium carbonate particles, resulting in a uniform calcium carbonate suspension. Then, 1.5 g of stearic acid was dissolved in 5 mL of anhydrous ethanol and heated in a water bath at 50 °C with stirring until completely dissolved. Subsequently, the solution was slowly added dropwise to the calcium carbonate suspension over a period of 5 min. After the addition was complete, the temperature was raised to 70 °C and stirred at 300 rpm for 60 min to allow the stearic acid to be fully adsorbed onto the surface of the calcium carbonate particles through physical action. After adsorption, the solution was filtered under reduced pressure while hot for about 10 min to obtain a modified calcium carbonate filter cake. The filter cake was transferred to a forced-air drying oven and dried at 105 °C for 3 h until the material reached constant weight. After drying, the material was mechanically pulverized to obtain modified calcium carbonate powder.

[0086] Experiment 1: The products provided in Examples 1 to 4 and Comparative Examples 1, 3 to 7 were subjected to the following performance tests. The test results are shown in Table 1.

[0087] The relevant performance indicators and testing methods are as follows: 1) Coating rate: A certain mass of uncoated inorganic powder and graphitic oxide-coated modified inorganic powder were weighed separately and calcined to constant weight in air at a suitable temperature (modified calcium carbonate powder was held at 550 ℃ for 60 min, and modified silica powder, modified kaolin powder, and modified boron nitride powder were held at 600 ℃ for 40 min). The mass change before and after calcination was recorded. Based on the mass loss before and after calcination, and after deducting the background weight loss of the matrix, the coating rate was calculated using the following formula: Where C represents the coverage ratio, This indicates the weight loss of graphene oxide-coated modified inorganic powder. This represents the weight loss of the uncoated inorganic powder, and m represents the theoretical amount of graphene oxide added.

[0088] 2) Uniformity of coating thickness: Transmission electron microscopy (TEM) was used. An appropriate amount of graphene-coated inorganic powder was dispersed in anhydrous ethanol and ultrasonically dispersed at low power for 10 min. The supernatant was dropped onto an ultrathin carbon film copper mesh, allowed to dry naturally, and observed at 200 kV. Fifty well-dispersed particles were randomly selected, and the thickness of their surface coating was measured. The average value, standard deviation, and relative deviation were calculated. The relative deviation was used to characterize the uniformity of the coating thickness.

[0089] 3) Coating firmness: Take samples of the same mass and ultrasonically clean them 100 times (30 min each time) with ethanol at a power of 300W. After centrifugation, test the coating rate of the samples.

[0090] Table 1 Performance Index Test Results As shown in Table 1, the modified inorganic powders prepared in each embodiment of this application all exhibit excellent comprehensive performance: the coating rate can reach more than 95%, the uniformity (relative deviation) of the coating layer thickness is less than or equal to 5%, and the coating rate can still be maintained at more than 90% after 100 ultrasonic cleanings with ethanol.

[0091] The coating rate, coating layer thickness uniformity, and coating firmness of the modified calcium carbonate powder prepared in Comparative Example 1 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that appropriate surface modification of inorganic powders can optimize their surface polarity and active sites, improve interfacial compatibility and interaction with graphene oxide, thereby increasing the coating rate, making the coating layer thickness more uniform and controllable, and significantly enhancing the coating firmness.

[0092] The coating efficiency, coating layer thickness uniformity, and coating firmness of the calcium carbonate powder prepared in Comparative Example 3 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that the in-situ coating temperature has a significant impact on the structure and properties of graphene oxide-coated inorganic powders. Excessively high temperatures can easily lead to graphene oxide agglomeration and partial reduction, resulting in decreased coating uniformity. In-situ coating at a suitable temperature (50~70℃) allows for more complete adsorption of graphene oxide on the inorganic powder surface, higher coating efficiency, controllable and uniform coating layer thickness, and stronger interfacial bonding, thereby obtaining composite powders with excellent overall performance.

[0093] The coating rate, coating layer thickness uniformity, and coating firmness of the calcium carbonate powder prepared in Comparative Example 4 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that an appropriate in-situ coating stirring rate can improve the dispersibility of inorganic powders, promote the uniform adsorption of graphene oxide, thereby increasing the coating rate, making the coating layer thickness more uniform and controllable, and enhancing the coating firmness. Excessive stirring rate can easily lead to the desorption and breakage of graphene oxide, thereby reducing the coating effect.

[0094] The coating efficiency, coating layer thickness uniformity, and coating strength of the calcium carbonate powder prepared in Comparative Example 5 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that moderate continuous ultrasound is beneficial for the full exfoliation and dispersion of graphene oxide, improving its coating efficiency on the surface of inorganic powders, resulting in a thinner and more uniform coating layer, and enhancing the coating strength. However, excessive continuous ultrasound can cause sheet breakage, functional group loss, and self-agglomeration, leading to a decrease in coating efficiency, uneven coating layer thickness, and reduced coating strength. Therefore, controlling reasonable ultrasound conditions is key to achieving efficient, uniform, and stable coating.

[0095] The coating efficiency, coating layer thickness uniformity, and coating firmness of the modified calcium carbonate powder prepared in Comparative Example 6 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that gradient centrifugation for fractional purification of graphene oxide can effectively remove stacked agglomerates and impurities, resulting in graphene oxide components with uniform size, controllable layer number, and excellent dispersibility. This component can form a thin, uniform, continuous, and dense coating layer on the surface of inorganic powder, significantly improving the coating efficiency and coating firmness.

[0096] The coating rate, coating layer thickness uniformity, and coating firmness of the modified calcium carbonate powder prepared by the traditional physical adsorption method in Comparative Example 7 were significantly lower than those of the modified calcium carbonate powder prepared in Example 1. This indicates that the present application achieves a tight bond between graphene oxide and inorganic powder through covalent bonding, which significantly improves the coating rate, coating layer thickness uniformity, and coating firmness of the modified calcium carbonate powder.

[0097] Experiment 2: Dispersion Test Equal amounts of the modified silica powder and unmodified silica powder provided in Example 2 were added to epoxy resin. After undergoing the same dispersion process, the agglomerate size of the coated particles in both groups of samples was tested. The test results showed that the agglomerate size of the coated particles of the modified silica powder provided in Example 2 was ≤50 µm, while the agglomerate size of the unmodified silica powder reached over 200 µm.

[0098] It is evident that the modified silica powder prepared by the method provided in this application has good compatibility with epoxy resin and is not prone to agglomeration, which is beneficial to improving material performance; while the unmodified silica powder has poor compatibility with epoxy resin and is prone to agglomeration, which limits the improvement of material performance.

[0099] Experiment 3: Antibacterial properties and tensile strength testing of materials Modified calcium carbonate powder from Example 1 and Comparative Example 2, as well as unmodified calcium carbonate powder, were added to equal amounts of polypropylene, with the addition amount being 30% of the mass of polypropylene, to obtain polypropylene products. The tensile strength improvement rate and antibacterial rate against Escherichia coli of the three groups of polypropylene products were tested, and the test results are shown in Table 2.

[0100] The tensile strength improvement rate is the percentage of the difference between the tensile strength of the polypropylene product with or without modified calcium carbonate powder and the tensile strength of the pure polypropylene product. The calculation formula is as follows: Tensile strength improvement rate = (Tensile strength of the polypropylene product with or without modified calcium carbonate powder - Tensile strength of the pure polypropylene product) ÷ Tensile strength of the pure polypropylene product.

[0101] Table 2 Test Results As shown in Table 2, the modified calcium carbonate powder obtained by adding only hydroxylated calcium carbonate powder of Comparative Example 2, omitting the subsequent in-situ coating modification step, or directly adding unmodified calcium carbonate powder, resulted in a worse improvement in the tensile strength and antibacterial properties of the polypropylene product than the polypropylene product obtained by adding the modified calcium carbonate powder of Example 1. This indicates that by adding the modified calcium carbonate powder obtained in the examples of this application to polypropylene, the tensile strength and antibacterial properties of the polypropylene product can be significantly improved.

[0102] In summary, the method for preparing modified inorganic powder provided in this application is simple and controllable, suitable for industrial production, and the resulting product can be widely used in the preparation of plastics, antibacterial coatings, lithium battery separators, etc., with significant economic and social benefits.

[0103] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing modified inorganic powder, characterized in that, include: S1. Under the first temperature condition, the inorganic powder is subjected to hydroxylation pretreatment to obtain hydroxylated inorganic powder; S2. Under the second temperature condition, the hydroxylated inorganic powder is added to the graphene oxide dispersion for stirring treatment, and a crosslinking agent is added during the stirring treatment to form a graphene oxide coating layer on the surface of the hydroxylated inorganic powder in situ, thereby obtaining graphene oxide coated inorganic powder. S3. Under a third temperature condition, the graphene oxide-coated inorganic powder is post-treated to obtain modified inorganic powder. The first temperature, the second temperature, and the third temperature all do not exceed 80 ℃.

2. The method for preparing modified inorganic powder according to claim 1, characterized in that, The first temperature is 60~80 ℃, the second temperature is 50~70 ℃, and the third temperature is 60~80 ℃.

3. The method for preparing modified inorganic powder according to claim 1, characterized in that, Step S1 includes: Inorganic powder is dispersed in a dispersion solvent to obtain an inorganic powder dispersion. Add a silane coupling agent to the inorganic powder dispersion, stir and react for 2-4 h, then centrifuge, wash and dry to obtain hydroxylated inorganic powder; The inorganic powder is selected from at least one of calcium carbonate, silicon dioxide, kaolin, aluminum hydroxide, boron nitride, and titanium dioxide, and has a particle size of 0.1~50 µm. The dispersion concentration of the inorganic powder dispersion is 50~100 g / L; The amount of the silane coupling agent added is 1% to 3% of the mass of the inorganic powder.

4. The method for preparing modified inorganic powder according to claim 1, characterized in that, The preparation steps of the graphene oxide dispersion are as follows: Graphene oxide was added to deionized water and stirred in an ice bath for 20-30 minutes to obtain the first dispersion. The first dispersion was subjected to intermittent ultrasonic treatment for 30-60 min to obtain the second dispersion; The second dispersion was subjected to gradient centrifugation to obtain a graphene oxide dispersion. The graphene oxide dispersion has a concentration of 0.1–1 mg / mL and a pH of 8–10; the intermittent ultrasonic treatment has an ultrasonic power of 300–500 W; the gradient centrifugation treatment includes low-speed centrifugation, medium-speed centrifugation, and high-speed centrifugation. The low-speed centrifugation speed is 2000–3000 rpm for 15–25 min, the medium-speed centrifugation speed is 5000–7000 rpm for 20–30 min, and the high-speed centrifugation speed is 8000–12000 rpm for 20–30 min.

5. The method for preparing modified inorganic powder according to claim 1, characterized in that, In step S2, the mass ratio of the hydroxylated inorganic powder to the graphene oxide dispersion is 10~50:1; The stirring rate for the stirring process is 300-500 r / min, and the stirring time is 3-6 h.

6. The method for preparing modified inorganic powder according to claim 1, characterized in that, The crosslinking agent is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methyl iodide, and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide methyl p-toluenesulfonate. The amount of crosslinking agent added is 5% to 10% of the mass of graphene oxide.

7. The method for preparing modified inorganic powder according to claim 1, characterized in that, In step S3, the graphene oxide-coated inorganic powder is washed and vacuum dried to obtain modified inorganic powder. The vacuum degree of the vacuum drying is -0.09 MPa to -0.1 MPa, and the vacuum drying time is 8 to 12 hours.

8. A modified inorganic powder, characterized in that, The modified inorganic powder is prepared by the method for preparing modified inorganic powder according to any one of claims 1 to 7; The modified inorganic powder includes hydroxylated inorganic powder and a graphene oxide coating layer covering the surface of the hydroxylated inorganic powder. The hydroxylated inorganic powder and the graphene oxide coating layer are bonded by covalent bonds, and the coating rate reaches more than 95%.

9. The modified inorganic powder according to claim 8, characterized in that, The oxygen content of the graphene oxide coating is 20-40 at%, and the sheet size is 100-500 nm. The thickness of the graphene oxide coating is 5~50 nm.

10. The application of the modified inorganic powder as described in any one of claims 8 to 9 in the preparation of plastics, coatings, rubber, and new energy materials.

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