A method of air jet spinning of nanoparticle-reinforced magnesium oxide fibers

Abstract

This invention discloses an airflow spinning method for nanoparticle-reinforced magnesium oxide fibers. The method employs a synergistic process of "airflow drawing + in-situ electrostatic loading of nanoparticles": First, the nanoparticles undergo surface chemical modification and ultrasonic standing wave pre-dispersion; then, the modified particles are transported to a corona discharge chamber via a carrier gas, where a high-voltage power supply applies a charge to the nanoparticles while simultaneously applying an opposite charge to the spinning solution; using the carrier gas flow as the sole drawing force, the fiber jet captures the charged nanoparticles in a directional manner through Coulomb attraction during formation, achieving uniform and robust in-situ loading; finally, drying and segmented heat treatment yield nanoparticle-reinforced magnesium oxide fibers. The resulting fibers exhibit significantly improved toughness, strength, and thermal shock resistance. This invention features a continuous, low-cost, and environmentally friendly process, and the products are suitable for applications such as ultra-high temperature insulation, aerospace, high-temperature flue gas purification, and antibacterial protection.

Description

Technical Field

[0001] This invention relates to a method for spinning inorganic ceramic fibers, and more particularly to an airflow spinning method for nanoparticle-reinforced magnesium oxide fibers. Background Technology

[0002] Ceramic fibers, due to their lightweight, excellent thermal insulation properties, high porosity, good thermal stability, and chemical inertness, have become an indispensable core thermal insulation material in the fields of high-temperature industrial equipment and aerospace equipment, and are widely used in steel, non-ferrous metal smelting and other fields.

[0003] With the development of high-end manufacturing globally, more stringent requirements have been placed on the comprehensive performance of inorganic ceramic fiber materials. Currently, existing inorganic ceramic fiber materials are mainly divided into two categories: oxide-based (such as Al2O3, SiO2, and ZrO2-based) and non-oxide-based (such as SiC and BN-based). Among them, oxide-based ceramic fibers have become the most widely used category due to their relatively mature preparation processes and moderate cost. However, existing oxide-based ceramic fibers still face many technical bottlenecks: conventional Al2O3-SiO2-based ceramic fibers have limited heat resistance, making it difficult to meet the long-term service requirements of high-temperature oxygen environments above 1300℃; although pure ZrO2-based ceramic fibers have extremely high melting points, they suffer from problems such as unstable high-temperature phase transformation, easy cracking and pulverization, and poor flexibility; at the same time, the preparation of existing ceramic fibers mostly relies on processes such as electrospinning and melt spinning, which have defects such as low production efficiency, high cost, poor fiber dispersion, and difficulty in preparing high-porosity flexible structures. Furthermore, most products only have a single thermal insulation function, making it difficult to adapt to the integrated application requirements under various working conditions.

[0004] In summary, existing oxide ceramic fibers generally suffer from problems such as insufficient heat resistance, easy pulverization at high temperatures, and poor flexibility. Traditional preparation processes rely on electrospinning or melt spinning, which have drawbacks such as low production efficiency, high cost, easy fiber adhesion, and difficulty in large-scale preparation of high-porosity flexible structures.

[0005] In terms of nanoparticle reinforcement, conventional blending or physical spraying methods suffer from bottlenecks such as uneven particle distribution, weak bonding, and easy detachment, making it difficult to achieve uniform and robust surface loading. Therefore, developing a new technology for the continuous and low-cost preparation of magnesium oxide fibers that couples fiber formation with load, achieves uniform and robust load, and has significant engineering value. Summary of the Invention

[0006] The purpose of this invention is to provide an airflow spinning method for nanoparticle-reinforced magnesium oxide fibers. This method employs a synergistic preparation process of "airflow drawing into fibers + in-situ electrostatic loading of nanoparticles" to achieve efficient, uniform, and firm loading of nanoparticles on the fiber surface, significantly improving fiber toughness, strength, and surface roughness, inhibiting fiber adhesion, and making the products suitable for ultra-high temperature insulation, aerospace, high-temperature flue gas purification, and antibacterial protection.

[0007] The objective of this invention is achieved through the following technical solution: An air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers, the method comprising the following steps: (1) A spinning solution is prepared by mixing magnesium source, ligand acid, solvent and spinning aid, and then delivered to the spinning nozzle by injection pump. The viscosity of the spinning solution at 25 °C is 4~50 Pa·s. (2) Surface modification of nanoparticles to improve their dispersion stability and charge carrying capacity, and then the modified nanoparticles are dispersed in an ultrasonic standing wave dispersion cavity. (3) The highly dispersed modified nanoparticles obtained in step (2) are transported to the corona discharge chamber by a carrier gas flow. A high voltage power supply is used to apply a charge to the nanoparticles in the corona discharge chamber, while the opposite charge is applied to the spinning solution in the spinning nozzle. (4) The carrier gas flow carrying charged nanoparticles obtained in step (3) enters the spinning nozzle through the corona discharge chamber, and the spinning liquid is stretched to form a continuous fiber jet. At the same time, the charged nanoparticles in the gas flow migrate in a direction under the action of Coulomb attraction and are adsorbed in situ onto the surface of the uncured fiber, and the precursor fiber is collected. (5) After drying and segmented heat treatment, the precursor fiber is obtained as nanoparticle-reinforced magnesium oxide fiber.

[0008] The method for air-jet spinning of magnesium oxide fiber reinforced with nanoparticles, wherein the nanoparticles in step (2) are selected from at least one of nano magnesium oxide, nano zirconium oxide, nano aluminum oxide, nano silicon oxide, nano titanium oxide, and nano yttrium oxide, and have an average particle size of 10~200 nm.

[0009] The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers, wherein the surface modification method in step (2) includes, but is not limited to, silane coupling agent modification, surfactant modification, and polymer grafting modification.

[0010] The method for air-jet spinning of nanoparticle-reinforced magnesium oxide fibers, wherein the ultrasonic standing wave dispersion cavity in step (2) includes a cavity body and ultrasonic transducers and reflective ends disposed on opposite sides of the cavity body; the ultrasonic transducers operate at a frequency of 200 kHz to 2 MHz, have an ultrasonic power of 100 to 300 W, and a dispersion time of 5 to 20 min.

[0011] The method for air-jet spinning of nanoparticle-reinforced magnesium oxide fibers, wherein in step (3), the carrier gas is selected from at least one of air, nitrogen, argon, and carbon dioxide, the carrier gas flow rate is 0.5~10 L / min, and the nanoparticle concentration in the carrier gas is 0.1~50 g / m³. 3 .

[0012] In the above-described method for air-jet spinning of nanoparticle-reinforced magnesium oxide fibers, the discharge voltage of the corona discharge cavity in step (3) is 5~50 kV and the discharge distance is 5~30 mm; the high-voltage power supply provides at least one of a constant electric field and a pulsed electric field.

[0013] The described air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers, wherein in step (5), the diameter of the nanoparticle-reinforced magnesium oxide fibers is 0.2~20 μm and the bulk density is 20~200 mg / cm³. 3 The fiber diameter is controlled by the viscosity of the spinning solution and the flow rate of the carrier gas.

[0014] The airflow spinning method for nanoparticle-reinforced magnesium oxide fiber, in step (5), the arithmetic mean roughness Ra of the nanoparticle-reinforced magnesium oxide fiber surface is 10%~100% of the fiber diameter, which is controlled by the concentration of nanoparticles in the carrier gas flow, the discharge voltage of the corona discharge cavity, and the discharge distance.

[0015] The advantages and effects of this invention are: The magnesium oxide fibers prepared by this invention have a three-dimensional porous network structure; the fiber diameter is 0.2~20 μm, and the bulk density is 20~200 mg / cm³. 3 The nanoparticles are uniformly and firmly loaded on the fiber surface, significantly improving the surface roughness and resulting in excellent fiber toughness, strength, thermal shock resistance, and resilience.

[0016] It has the following significant characteristics: 1. This invention employs an innovative preparation process that combines airflow-driven fiber forming with in-situ electrostatic loading of nanoparticles, resulting in significantly improved loading uniformity and bonding strength.

[0017] 2. The present invention allows for flexible control of fiber diameter, density, porosity and surface roughness.

[0018] 3. This invention can effectively inhibit fiber adhesion and significantly improve toughness, strength and thermal shock resistance.

[0019] 4. The present invention has high airflow spinning efficiency, simple equipment, low cost, and is environmentally friendly and safe.

[0020] 5. The product of this invention is suitable for applications with special requirements such as ultra-high temperature insulation, aerospace, high-temperature flue gas purification, and antibacterial protection. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a process flow diagram of Embodiment 1 of the present invention; Figure 3This is a SEM image of nanoparticle-reinforced air-spun magnesium oxide fiber from Example 1 of the present invention. Figure 4 This is a process flow diagram of Embodiment 2 of the present invention; Figure 5 This is a SEM image of nanoparticle-reinforced air-spun magnesium oxide fiber from Example 2 of the present invention. Figure 6 This is a process flow diagram of Embodiment 3 of the present invention. Figure 7 This is a SEM image of nanoparticle-reinforced air-spun magnesium oxide fiber from Example 3 of the present invention. Figure 8 This is a process flow diagram of Embodiment 4 of the present invention; Figure 9 This is a SEM image of nanoparticle-reinforced air-spun magnesium oxide fiber from Example 4 of the present invention. Figure 10 This is a process flow diagram of Embodiment 5 of the present invention; Figure 11 This is a SEM image of nanoparticle-reinforced air-spun magnesium oxide fiber from Example 5 of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings.

[0023] The preparation steps of the air-jet spinning method for preparing nanoparticle-reinforced magnesium oxide fibers according to the present invention are as follows: (1) Preparation of magnesium-based sol spinning solution The magnesium source and ligand acid were reacted in a solvent until the solution was clear. A spinning aid was added and the viscosity was adjusted to 4-50 Pa·s at 25 °C. The solution was then aged to obtain a magnesium-based sol spinning solution.

[0024] The magnesium source is magnesium oxide, magnesium nitrate hexahydrate, magnesium acetate, magnesium hydroxide, or magnesium carbonate; The ligand acids are acetic acid, propionic acid, citric acid monohydrate, nitric acid, and acrylic acid; The solvents are distilled water, anhydrous methanol, anhydrous ethanol, and ethylene glycol; The spinning aids are polyvinylpyrrolidone (PVP-K90 / K88), polyvinyl alcohol (PVA), and polyethylene glycol (PEG-4000). (2) Surface modification of nanoparticles Surface chemical modification of nanoparticles can improve their dispersion stability in sol, inhibit agglomeration, enhance charge carrying capacity, and strengthen their interfacial bonding strength with magnesium oxide fiber matrix.

[0025] The modified nanoparticles are then dispersed by ultrasonic standing waves, so that the nanoparticles form a periodic and orderly distribution before entering the spinning region, thus providing a more regular spatial distribution basis for subsequent electrostatic field-induced directional migration and Coulomb adsorption.

[0026] The nanoparticles are at least one of nano-magnesium oxide, nano-zirconia, nano-alumina, nano-silicon oxide, nano-titanium oxide, or nano-yttrium oxide, with an average particle size of 10-200 nm.

[0027] Modification methods include, but are not limited to, the following, and one or more combinations can be selected according to actual needs: coupling agent modification, surfactant modification, polymer grafting modification, inorganic coating modification, high-energy surface modification, etc.

[0028] The ultrasonic standing wave dispersion cavity includes a cavity body and ultrasonic transducers and reflecting ends disposed on opposite sides of the cavity body; the ultrasonic transducers operate at a frequency of 200 kHz to 2 MHz, have an ultrasonic power of 100 to 300 W, and a dispersion time of 5 to 20 min.

[0029] (3) Applying charge and in-situ adsorption on the fiber surface Highly dispersed modified nanoparticles are conveyed to the corona discharge chamber. A high-voltage power supply is used to apply a charge to the nanoparticles in the corona discharge chamber, so that the modified nanoparticles entering the spinning area acquire a first polar charge through corona discharge. At the same time, the opposite charge is applied to the spinning solution in the spinning nozzle.

[0030] A multi-nozzle airflow spinning device is used, in which the carrier gas flow is used as the single stretching force to stretch the spinning solution into a continuous fiber jet. The carrier gas flow carrying charged nanoparticles enters the spinning nozzle through the corona discharge chamber, stretching the spinning solution into a continuous fiber jet. At the same time, the charged nanoparticles in the airflow migrate directionally under the action of Coulomb attraction and adsorb in situ onto the surface of the uncured fiber, and the precursor fiber is collected.

[0031] The carrier gas stream is selected from at least one of air, nitrogen, argon, and carbon dioxide, with a flow rate of 0.5–10 L / min and a nanoparticle concentration of 0.1–50 g / m³. 3 .

[0032] The discharge voltage of the corona discharge chamber is 5~50 kV, and the discharge distance is 5~30 mm; the high-voltage power supply can provide at least one of a constant electric field and a pulsed electric field.

[0033] The spinning process parameters are as follows: spinning temperature 30~55 ℃, airflow pressure 0.02~0.1 MPa, receiving distance 40~60cm, spinning solution feed rate 0.04~0.08 mL / min, relative humidity 10~30%, main nozzle inner diameter 18~22G, and auxiliary nozzle specifications are selected according to the arrangement.

[0034] The arrangement of multiple nozzles includes: coaxial single nozzle, parallel double nozzle, main and auxiliary multi-nozzle, etc.; the main nozzle delivers spinning solution, and the auxiliary nozzle delivers nanoparticles.

[0035] (4) Drying and segmented heat treatment The precursor fibers were dried and subjected to segmented heat treatment. The drying temperature was 60~120 ℃ and the time was 2~12 h. The segmented heat treatment included: holding at room temperature to 600 ℃ for 0.5~2 h to remove organic matter, and holding at 800~1200 ℃ for 1~4 h for oxidation, with a heating rate of 1~10 ℃ / min. Finally, nanoparticle-reinforced magnesium oxide fibers were obtained.

[0036] The following experiments were conducted in the laboratory following the preparation steps to test nanoparticle-reinforced air-spun magnesium oxide fibers: Example 1

[0037] (1) Preparation of magnesium-based sol spinning solution 8 g of magnesium nitrate hexahydrate was dissolved in a mixed solvent of 40 mL anhydrous ethanol and 10 mL ethylene glycol. 2.5 g of glacial acetic acid was added, and the mixture was stirred at 35 °C for 0.8 h until the solution was completely clear. The temperature was then raised to 50 °C, and 2.5 g of polyvinylpyrrolidone (PVP-K90) was added. Stirring was continued for 1.5 h, maintaining the solution viscosity at 4.5 Pa·s. After standing and aging for 12 h, a clear and transparent Mg sol spinning solution was obtained.

[0038] (2) Surface modification of nanoparticles 5 g of 20 nm nano-MgO powder was dispersed in 100 mL of anhydrous ethanol and ultrasonically dispersed for 30 min. 0.6 g of γ-aminopropyltriethoxysilane (KH550) was added, and the pH was adjusted to 4–5 with glacial acetic acid. The mixture was then refluxed and stirred in an 80 °C water bath for 6 h. After the reaction was complete, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 60 °C for 12 h to obtain aminated modified nano-MgO.

[0039] The modified nano-MgO was placed in an ultrasonic standing wave dispersion cavity (with ultrasonic transducers and reflectors on both sides of the cavity), with a working frequency of 500 kHz, ultrasonic power of 200 W, and dispersion time of 10 min, to obtain highly dispersed modified nanoparticles.

[0040] (3) Applying charge and in-situ adsorption on the fiber surface A parallel dual-nozzle airflow spinning device was used (the axes of the two nozzles were angled at 30°). The modified nano-MgO obtained in step (2) was conveyed to the corona discharge chamber by a carrier gas (air, flow rate 2 L / min), and a constant positive DC voltage of 18 kV was applied to charge the nanoparticles positively; at the same time, a constant negative DC voltage of 18 kV was applied to the spinning solution in the spinning nozzle (connected to the main nozzle via a high-voltage power supply). The spinning solution obtained in step (1) was injected into the main nozzle (20G) at a feed rate of 0.06 mL / min; the carrier gas carrying the charged nanoparticles was introduced into the auxiliary nozzle (22G) at a feed rate of 0.02 mL / min. Other spinning parameters: spinning temperature 40 ℃, airflow pressure 0.06 MPa, receiving distance 50 cm, relative humidity 20%.

[0041] Under the single stretching force of the carrier gas flow, the spinning solution is sheared to form a continuous fiber jet; simultaneously, positively charged nanoparticles migrate directionally to the negatively charged fiber surface and are adsorbed in situ under the influence of Coulomb attraction. White, fluffy precursor fibers are collected.

[0042] (4) Heat treatment The precursor fibers were placed in a forced-air drying oven and dried at 60 °C for 8 h. Then, they were transferred to a muffle furnace and subjected to segmented heat treatment in an air atmosphere: the temperature was increased from room temperature to 180 °C at a rate of 0.8 °C / min and held for 1.5 h; then the temperature was increased to 900 °C at a rate of 1.5 °C / min and held for 3 h; finally, the temperature was allowed to cool naturally to room temperature to obtain nano-MgO reinforced air-spun magnesium oxide fibers.

[0043] The resulting fibers are white and have a density of 48 mg / cm³. 3 The fiber diameter is 4.2 μm. SEM observation shows that the nano-MgO particles are uniformly distributed on the fiber surface, forming a distinct rough and uneven structure, with Ra being 70% of the fiber diameter. Example 2

[0044] (1) Preparation of magnesium-based sol spinning solution 10 g of magnesium acetate tetrahydrate was dissolved in 50 mL of anhydrous methanol, and 3 g of propionic acid and 1 g of citric acid monohydrate were added. The mixture was stirred at 30 °C for 1 h until clear. The temperature was raised to 55 °C, and 3 g of polyethylene glycol (PEG-4000) was added. The mixture was stirred for another 2 h, and the viscosity of the solution was controlled at 6.0 Pa·s. After standing for 12 h, the Mg sol spinning solution was obtained.

[0045] (2) Surface modification of nanoparticles Aminated nano-MgO was prepared according to the method in Example 1. 3 g of the above product was dispersed in 60 mL of toluene, and 0.15 g of azobisisobutyronitrile (AIBN) and 3 g of methyl methacrylate (MMA) were added. The mixture was stirred and polymerized at 75 °C for 8 h under nitrogen protection. After the reaction, the nano-MgO was washed three times alternately by centrifugation with toluene and ethanol, and then dried under vacuum at 60 °C to obtain PMMA-grafted modified nano-MgO (TGA grafting rate ≈ 12%). This modified MgO was stably dispersed in anhydrous ethanol for more than 72 h.

[0046] The modified nano-MgO was subjected to ultrasonic standing wave dispersion: frequency 800 kHz, power 150 W, time 8 min.

[0047] (3) Applying charge and in-situ adsorption on the fiber surface A coaxial single nozzle (inner tube 18G, outer tube 14G) was used. The modified nano-MgO obtained in step (2) was carried into the corona discharge chamber by a carrier gas (nitrogen, flow rate 1.5 L / min), and a pulsed positive high voltage (peak value 12 kV, frequency 200 Hz, duty cycle 40%) was applied to make the nanoparticles positively charged; at the same time, a pulsed negative high voltage (same parameters) was applied to the spinning solution. The spinning solution from step (1) was introduced into the inner tube (feed 0.05 mL / min), and the carrier gas carrying the charged nanoparticles was introduced into the outer tube (feed 0.015 mL / min). Other parameters: spinning temperature 45 ℃, airflow pressure 0.04 MPa, receiving distance 55 cm, relative humidity 15%.

[0048] Under the influence of a pulsed electric field, positively charged nanoparticles undergo periodic directional migration toward the surface of a negatively charged fiber jet, forming a rhythmic patterned adsorption. The precursor fibers are then collected.

[0049] (4) Heat treatment The drying process is the same as in Example 1. Segmented heat treatment: the temperature is increased to 200℃ at 0.6℃ / min and held for 1 h, then increased to 850℃ at 1.2℃ / min and held for 4 h, followed by natural cooling.

[0050] The resulting fiber density was 85 mg / cm³. 3 The fiber diameter is 4.7 μm. After heat treatment at 800 ℃, the fiber still maintains its complete morphology without cracking or powdering, exhibiting excellent thermal shock resistance. Example 3

[0051] (1) Preparation of magnesium-based sol spinning solution Dissolve 10 g of magnesium nitrate hexahydrate in 50 mL of anhydrous ethanol, add 3 g of acetic acid, and stir at room temperature for 0.5 h until clear. Heat to 50 ℃, add 3 g of PVP-K90, adjust the viscosity to 20.2 Pa·s, stir for 2 h, and let stand for 12 h.

[0052] (2) Surface modification of nanoparticles 5 g of 20 nm nano ZrO2 powder was dispersed in 100 mL of anhydrous ethanol, 0.5 g of KH550 silane coupling agent was added, the mixture was refluxed and stirred at 80 °C for 6 h, centrifuged and washed 3 times, and dried under vacuum at 60 °C to obtain amino-modified ZrO2.

[0053] The modified nano-ZrO2 was dispersed by ultrasonic standing wave at a frequency of 600 kHz, a power of 180 W, and a time of 12 min.

[0054] (3) Applying charge and in-situ adsorption on the fiber surface A parallel dual-nozzle device was used. Step (2) was carried into the corona discharge chamber via carrier gas (air, flow rate 2.5 L / min), and a constant positive DC voltage of 15 kV was applied to positively charge the nanoparticles; a constant negative DC voltage of 15 kV was applied to the spinning solution. The main nozzle (20G) injected the spinning solution from step (1) (feed 0.06 mL / min), and the auxiliary nozzle (22G) introduced the carrier gas carrying the charged nanoparticles (feed 0.02 mL / min). Spinning parameters: temperature 40 ℃, air pressure 0.05 MPa, receiving distance 50 cm, humidity 20%.

[0055] High-speed airflow stretches the nanoparticles into fibers, and positively charged nanoparticles migrate directionally to and are firmly adsorbed onto the surface of negatively charged fibers under Coulomb attraction. The precursor fibers are then collected.

[0056] (4) Heat treatment The prepared precursor fibers were dried at 60 °C for 8 h. Then, they were subjected to segmented heat treatment in air: the temperature was increased to 180 °C at 0.8 °C / min and held for 1 h, then increased to 1000 °C at 1.5 °C / min and held for 3 h, followed by natural cooling.

[0057] The resulting fiber density was 102 mg / cm³. 3 The fiber diameter is 8.5 μm, and nano ZrO2 particles are uniformly attached to the fiber surface. Ra is 65% of the fiber diameter. Example 4

[0058] (1) Preparation of magnesium-based sol spinning solution 7 g of magnesium nitrate hexahydrate was dissolved in 50 mL of ethylene glycol, and 3.5 g of citric acid monohydrate was added. The mixture was stirred at 45 °C for 1 h until clear. The temperature was raised to 55 °C, and 3 g of polyvinyl alcohol (PVA) was added. The mixture was stirred for another 2 h, and the viscosity of the solution was controlled at 15.5 Pa·s. The solution was allowed to stand for 12 h to obtain the magnesium sol spinning solution.

[0059] (2) Surface modification of nanoparticles 5 g of 25 nm nano-Al2O3 powder was dispersed in 100 mL of deionized water, and 0.4 g of sodium dodecyl sulfate (SDS) was added. After ultrasonic dispersion for 30 min, the mixture was stirred in a 60 ℃ water bath for 3 h. After centrifugation, the powder was washed twice with deionized water and once with anhydrous ethanol, and then dried under vacuum at 60 ℃ to obtain SDS-modified nano-Al2O3.

[0060] The modified nano-Al2O3 was dispersed by ultrasonic standing wave at a frequency of 400 kHz, a power of 120 W, and a time of 15 min.

[0061] (3) Applying charge and in-situ adsorption on the fiber surface A parallel dual-nozzle configuration (main nozzle 19G, auxiliary nozzle 21G) was used. Step (2) was carried into the corona discharge chamber via a carrier gas (argon, flow rate 1.8 L / min), and a constant negative DC voltage of 15 kV was applied to negatively charge the nanoparticles; a constant positive DC voltage of 15 kV was applied to the spinning solution. The feed rate of the main nozzle was 0.05 mL / min, and the feed rate of the auxiliary nozzle was 0.02 mL / min. Other parameters: spinning temperature 38 ℃, airflow pressure 0.05 MPa, receiving distance 50 cm, relative humidity 20%.

[0062] Negatively charged nanoparticles migrate directionally to and are firmly adsorbed onto the surface of positively charged fibers. Precursor fibers are then collected.

[0063] (4) Heat treatment Drying: Dry at 55 ℃ for 12 h. Segmented heat treatment: Heat to 180 ℃ at 0.7 ℃ / min and hold for 1.5 h, then heat to 950 ℃ at 1.3 ℃ / min and hold for 4 h, then cool naturally.

[0064] The resulting fiber density was 52.3 mg / cm³. 3 The fiber diameter is 4.6 μm. Surface roughening increases the friction between fibers, and after assembling the fibers into a sponge structure, the compression resilience of this fiber sponge is significantly improved compared to a smooth fiber sponge. Example 5

[0065] (1) The preparation of magnesium-based sol spinning solution is the same as in Example 1.

[0066] (2) The surface modification of nanoparticles is the same as in Example 1.

[0067] (3) Applying charge and in-situ adsorption on the fiber surface The parameters are the same as in Example 1, but no charge is applied to the nanoparticles or the spinning solution; that is, the fibers are formed entirely by the carrier gas flow, and the nanoparticles adhere to the fiber surface only through mechanical collision and solvent wetting. Precursor fibers are collected.

[0068] (4) Heat treatment is the same as in Example 1.

[0069] Characterization of the obtained fibers revealed extremely poor MgO loading on the fiber surface, with Ra being 10% of the fiber diameter. Furthermore, due to the lack of Coulombic "pinning" effect, some MgO significantly detached after heat treatment, resulting in a significantly lower bonding strength compared to Example 1.

[0070] This embodiment demonstrates from the opposite perspective that simple airflow physical powder spraying cannot achieve effective loading. The synergistic mechanism of airflow fiber formation and electrostatic anisotropic adsorption phase decoupling is the key technology for achieving efficient, uniform, and robust loading of nanoparticles.

Claims

1. A method for air-jet spinning of nanoparticle-reinforced magnesium oxide fibers, characterized in that, The method includes the following steps: (1) A spinning solution is prepared by mixing magnesium source, ligand acid, solvent and spinning aid, and then delivered to the spinning nozzle by injection pump. The viscosity of the spinning solution at 25 °C is 4~50 Pa·s. (2) Surface modification of nanoparticles to improve their dispersion stability and charge carrying capacity, and then the modified nanoparticles are dispersed in an ultrasonic standing wave dispersion cavity. (3) The highly dispersed modified nanoparticles obtained in step (2) are transported to the corona discharge chamber by a carrier gas flow. A high voltage power supply is used to apply a charge to the nanoparticles in the corona discharge chamber, while the opposite charge is applied to the spinning solution in the spinning nozzle. (4) The carrier gas flow carrying charged nanoparticles obtained in step (3) enters the spinning nozzle through the corona discharge chamber, and the spinning liquid is stretched to form a continuous fiber jet. At the same time, the charged nanoparticles in the gas flow migrate in a direction under the action of Coulomb attraction and are adsorbed in situ onto the surface of the uncured fiber, and the precursor fiber is collected. (5) After drying and segmented heat treatment, the precursor fiber is obtained as nanoparticle-reinforced magnesium oxide fiber.

2. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (2), the nanoparticles are selected from at least one of nano magnesium oxide, nano zirconium oxide, nano aluminum oxide, nano silicon oxide, nano titanium oxide, and nano yttrium oxide, with an average particle size of 10~200 nm.

3. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, The surface modification methods in step (2) include, but are not limited to, silane coupling agent modification, surfactant modification, and polymer grafting modification.

4. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (2), the ultrasonic standing wave dispersion cavity includes a cavity body and ultrasonic transducers and reflective ends disposed on opposite sides of the cavity body; the ultrasonic transducer operates at a frequency of 200 kHz to 2 MHz, has an ultrasonic power of 100 to 300 W, and a dispersion time of 5 to 20 min.

5. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (3), the carrier gas flow is selected from at least one of air, nitrogen, argon, and carbon dioxide, the carrier gas flow rate is 0.5~10 L / min, and the concentration of nanoparticles in the carrier gas flow is 0.1~50 g / m³. 3 .

6. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (3), the discharge voltage of the corona discharge cavity is 5~50 kV and the discharge distance is 5~30 mm; the high-voltage power supply provides at least one of a constant electric field and a pulsed electric field.

7. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (5), the diameter of the nanoparticle-reinforced magnesium oxide fiber is 0.2~20 μm and the bulk density is 20~200 mg / cm³. 3 The fiber diameter is controlled by the viscosity of the spinning solution and the flow rate of the carrier gas.

8. The air-jet spinning method for nanoparticle-reinforced magnesium oxide fibers according to claim 1, characterized in that, In step (5), the arithmetic mean roughness Ra of the nanoparticle-reinforced magnesium oxide fiber surface is 10% to 100% of the fiber diameter, and is controlled by the concentration of nanoparticles in the carrier gas flow, the discharge voltage of the corona discharge cavity, and the discharge distance.

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