A programmable method for fabricating PAN / Fe3O4 nanofibers via electromagnetic lens-mediated thermo-magnetic-component multi-field coupling.

Abstract

This invention discloses a programmable preparation method for PAN / Fe3O4 nanofibers mediated by electromagnetic lenses and involving multi-field coupling of thermomagnetic components. This invention uses temperature as the core variable for active control, constructing a dynamic synergistic coupling system with the electromagnetic lens-mediated magnetic field and the Fe3O4 dopant component field. Through spinning solution preparation, assembly and debugging of the electromagnetic lens and electric field device, active thermal field control coupling, and multi-field synergistic electrospinning, the invention achieves precise programmable control over the structure of PAN / Fe3O4 nanofibers from the molecular to the macroscopic scale. This invention optimizes jet stretching, solidification kinetics, and deposition interface behavior through the synergistic effect of the three thermomagnetic components, effectively addressing the core challenges of imbalance between magnetic and mechanical properties and poor structural controllability, significantly improving fiber diameter uniformity, density, mechanical properties, and magnetic response performance.

Description

Technical Field

[0001] This invention belongs to the technical field of functional nanofiber manufacturing, and particularly relates to a programmable preparation method of PAN / Fe3O4 nanofibers mediated by electromagnetic lens-mediated thermal-magnetic-component multi-field coupling. Background Technology

[0002] PAN / Fe3O4 composite nanofibers, possessing both the excellent mechanical properties of polyacrylonitrile and the magnetic response characteristics of Fe3O4 nanoparticles, have irreplaceable application value in high-end fields such as energy conversion, flexible sensing, and intelligent filtration. Their preparation technology has always been a research hotspot in the field of functional nanomaterials. Electrospinning, as one of the most convenient and efficient processes for preparing nanofibers, has been widely used in the preparation of PAN / Fe3O4 composite nanofibers; however, existing spinning technologies still face significant technical bottlenecks.

[0003] Currently, a method for preparing Fe3O4 nanoparticles using current-controlled magnetic field-assisted electrospinning has been developed in the prior art (i.e., the applicant's authorized patent, patent number: ZL 2024 1 1883257.6). This authorized patent achieves precise control of the magnetic field by adjusting the parameters of the aforementioned electromagnetic lens, and in conjunction with the adjustment of the component ratio, it improves the dispersibility and orientation of Fe3O4 nanoparticles to a certain extent. However, this authorized patent is limited to the independent control of the magnetic field and the components, and does not incorporate temperature as an active control variable into the system. The spinning temperature of 25 ℃ set therein is only the conventional ambient temperature, which is a passive environmental parameter rather than an actively controlled energy field, ignoring the key influence of temperature on the rheological properties of the spinning solution, the molecular chain motion behavior, and the magnetic response efficiency of the particles. This single two-field control mode prevents the synergistic optimization of multi-scale characteristics such as molecular chain arrangement, crystallinity, and pore structure of PAN / Fe3O4 nanofibers. It generally suffers from problems such as imbalance between magnetic and mechanical properties, narrow controllable range of structure, and difficulty in programmable customization, which seriously restricts its large-scale application in advanced devices such as high-performance triboelectric nanogenerators and lithium-ion battery separators. The above-mentioned technical pain points cannot be solved by existing technologies with authorized patents. Therefore, developing a programmable preparation method that can achieve multi-field synergistic control has become an urgent technical problem to be solved.

[0004] Furthermore, while some existing studies have attempted to introduce temperature parameters to assist electrospinning, these studies mostly treat temperature as an independent auxiliary condition, merely used to adjust the solvent evaporation rate. They fail to form a synergistic coupling system with the magnetic field and component control methods described in existing patents, thus failing to achieve dynamic linkage control of temperature, magnetic field, and components. More importantly, these studies do not incorporate precise magnetic field control technology mediated by electromagnetic lenses, nor do they adapt and optimize for the core conditions such as component ratios and electromagnetic lens parameters specified in existing patents. This results in their technical solutions failing to address the core pain points of performance trade-offs and poor structural controllability found in existing patents, and they cannot achieve programmable control of nanofibers from the molecular to the macroscopic scale. This is fundamentally different from the "thermal-magnetic-component" multi-field synergistic control strategy proposed in this invention, further confirming the necessity and innovation of this invention. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and to design a programmable preparation method for PAN / Fe3O4 nanofibers with electromagnetic lens-mediated thermo-magnetic-component multi-field coupling. Addressing the limitations of existing patents that only allow for the control of two fields (magnetic field and component), with temperature being a passive environmental parameter, and the lack of multi-field synergistic coupling in current temperature-introduced research, this invention uses temperature as the core variable for active control. This temperature, along with the electromagnetic lens-mediated magnetic field and Fe3O4-doped component field, forms a dynamic synergistic coupling system, enabling precise programmable control of the PAN / Fe3O4 nanofiber structure from the molecular to the macroscopic scale. This solves the core pain points of existing technologies, such as the imbalance between the magnetic and mechanical properties of the fibers and poor structural controllability. It broadens the application scenarios of composite nanofibers and provides reliable preparation technology support for their large-scale application in advanced devices such as high-performance triboelectric nanogenerators and lithium-ion battery separators.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A programmable method for fabricating PAN / Fe3O4 nanofibers via electromagnetic lens-mediated thermo-magnetic-component multi-field coupling includes the following steps: Step (1): Prepare the spinning solution, specifically: weigh PAN powder, dissolve it in DMF solvent, and obtain a uniform PAN / DMF mother liquor by magnetic stirring and ultrasonic dispersion treatment; add Fe3O4 nanoparticles and dispersant TritonX-100 to the mother liquor, and ultrasonically disperse it again until there is no obvious agglomeration to obtain a magnetic electrospinning solution. Step (2): Assemble the electromagnetic lens and electric field device. Specifically, fix the syringe containing the magnetic electrospinning solution prepared in step (1) to the micro-injection pump, adjust the distance between the syringe needle and the collecting electrode, the distance between the electromagnetic lens and the collecting electrode, connect the positive and negative terminals of the DC high voltage power supply to the syringe needle and the collecting electrode respectively, set the micro-injection pump propulsion rate and the electromagnetic lens working current, and then start the high voltage power supply to complete the basic programmable control of the magnetic field. Step (3): Active control and coupling of the thermal field, specifically: attach the heating plate to the receiving plate of the electrospinning device, set the target temperature of the receiving plate, start the heating program and preheat, so that the temperature of the receiving plate is uniform and stable. Step (4): Prepare nanocomposite fibers, specifically: start the micro-injection pump, so that the magnetic electrospinning solution forms a stable charged jet under the synergistic effect of high voltage electrostatic force, electromagnetic lens controllable magnetic field force and the preset temperature field mentioned in step (3); after the jet moves to the constant temperature receiving plate, it is solidified by solvent evaporation and fiber solidification to obtain a magnetic PAN / Fe3O4 nanofiber film.

[0007] Compared with the prior art, the present invention has the following advantages: 1. Innovative construction of a multi-field coupling control system, breaking through the limitations of existing technology: This invention is the first to transform the temperature field into an actively controlled core energy field, which is deeply coupled with the magnetic field mediated by the electromagnetic lens and the Fe3O4 component field in the authorized patent, forming a dynamic synergistic coupling system of "thermal-magnetic-component". This completely breaks the technical barrier of existing technology, which can only achieve independent control of the "magnetic-component" two fields and temperature is only used as a passive environmental parameter. It fills the technical gap of multi-field synergistic control of the cross-scale structure of PAN / Fe3O4 nanofibers.

[0008] 2. Achieves precise cross-scale programmable control, significantly improving structural controllability. Leveraging multi-field coupling effects, this invention can simultaneously control the arrangement of PAN molecular chains and the orientation of Fe3O4 particles at the fiber molecular scale, as well as porosity, fiber density, and network structure at the macroscopic scale, enabling precise programmable design from molecular chains to the entire film. Compared to existing patents that can only optimize particle orientation and dispersion, this invention comprehensively expands the controllability dimensions, significantly improving the uniformity and controllability of the fiber's multi-scale structure, thus solving the pain points of existing technologies, such as narrow controllable range and inability to achieve cross-scale programming.

[0009] 3. Overcoming the performance trade-off and achieving comprehensive performance optimization. This invention precisely controls the viscosity of the spinning solution, solvent evaporation rate, and molecular chain crystallization kinetics through the synergistic effect of temperature, magnetic field, and component field, effectively coordinating the technical bottleneck of the difficulty in balancing the magnetic and mechanical properties of PAN / Fe3O4 nanofibers in existing technologies. Verification shows that the fibers prepared by this invention exhibit a more than 30% increase in magnetic response intensity, a 30%–50% improvement in mechanical properties, an 11.4% reduction in average nanofiber diameter, a 44%–50% increase in average thickness, a 4%–6% reduction in porosity, and a 10%–15% increase in fiber density, while maintaining excellent crystallinity. The overall performance far surpasses that of authorized patents and existing single temperature / magnetic field control technologies.

[0010] 4. Expanding application scenarios and demonstrating outstanding value in high-end applications. The PAN / Fe3O4 nanofibers prepared by this invention possess controllable cross-scale structures and synergistically optimized performance, which can be precisely adapted to the performance requirements of high-end devices such as high-performance triboelectric nanogenerators (improving energy conversion efficiency) and lithium-ion battery separators (optimizing ion transport and mechanical strength). This breaks through the limitations of existing fiber technologies in high-end applications and provides a new technical path for the large-scale application of functional composite nanofibers.

[0011] 5. The temperature field formed by the temperature of the receiving plate in this invention is the core control parameter. It does not exist independently, but forms a dynamic synergistic coupling system with the component field formed by the doping amount of Fe3O4 nanoparticles in step (1) and the magnetic field formed by the electromagnetic lens current in step (2). This breaks the limitation of the original two-field control. By adjusting the temperature field parameter, in combination with the magnetic force and component content, the unpredictable technical effect of the interaction of the three fields is achieved, providing core support for the programmable control of nanofiber cross-scale structures. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a programmable preparation method for PAN / Fe3O4 nanofibers mediated by an electromagnetic lens through thermo-magnetic-component multi-field coupling, used in this invention.

[0013] Figure 2 These are SEM images of magnetic nanofiber films prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent.

[0014] Figure 3 The graph shows the average diameter of magnetic nanofibers prepared under different temperature experimental conditions (room temperature, 30℃-60℃) in this invention patent.

[0015] Figure 4 The graph shows the average thickness of magnetic nanofiber films prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent.

[0016] Figure 5 The diagram shows the area values ​​of the nanofiber deposition circles prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent.

[0017] Figure 6 The graph shows the mechanical properties of nanofibers prepared under different temperature experimental conditions (room temperature, 30℃-60℃) in this invention patent.

[0018] Figure 7 XRD patterns of nanofibers prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent.

[0019] Figure 8 The graph shows the magnetic properties of nanofiber films prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent.

[0020] Figure 9 The porosity values ​​of nanofiber films prepared under different temperature experimental conditions (room temperature, 30 ℃-60 ℃) in this invention patent are shown in the figure.

[0021] Figure 10 This is a graph showing the density values ​​of nanofibers prepared under different temperature experimental conditions (room temperature, 30℃-60℃) in this invention patent. Detailed Implementation

[0022] The present invention will be further described below with reference to embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0023] like Figure 1 As shown, a programmable method for preparing PAN / Fe3O4 nanofibers via electromagnetic lens-mediated thermo-magnetic-component multi-field coupling comprises a synergistic control system consisting of an electromagnetic lens magnetic field module, a temperature-controlled receiving plate module, and a planar electrospinning module. The electromagnetic lens generates a controllable gradient magnetic field through a magnetic yoke, excitation coil, and DC power supply, applying Lorentz force to the charged jet to achieve jet stabilization and particle orientation control. A silicone rubber heating plate provides precise temperature control of 303–333 K for the receiving plate, actively regulating solvent evaporation and fiber solidification kinetics. Under the triple synergistic effect of a high-voltage electrostatic field, a controllable magnetic field, and a preset temperature field, the magnetic spinning solution (PAN / DMF / Fe3O4) forms a stable charged jet and deposits on the isothermal receiving plate, ultimately controllably preparing a PAN / Fe3O4 composite nanofiber film with a multi-scale ordered structure, achieving programmable and precise control from molecular orientation to macroscopic pore structure.

[0024] A programmable method for fabricating PAN / Fe3O4 nanofibers via electromagnetic lens-mediated thermo-magnetic-component multi-field coupling includes the following steps: Step (1) Preparation of spinning solution: Accurately weigh PAN powder and dissolve it in N,N-dimethylformamide (DMF) solvent, wherein the mass ratio of DMF solvent to polyacrylonitrile powder is 0.2:1; after magnetic stirring and ultrasonic dispersion treatment, a uniform PAN / DMF mother liquor is obtained; Fe3O4 nanoparticles and an equal amount of dispersant Triton X-100 are added to the mother liquor, and ultrasonic dispersion is performed again until there is no obvious agglomeration, thus obtaining a magnetic electrospinning solution; Step (2) Assembly and debugging of electromagnetic lens and electric field device: Fix the syringe containing the magnetic electrospinning solution prepared in step (1) to the micro-injection pump, precisely adjust the distance between the syringe needle and the collecting electrode, and between the electromagnetic lens and the collecting electrode, connect the positive and negative terminals of the DC high voltage power supply to the syringe needle and the collecting electrode respectively, set the micro-injection pump propulsion rate and the electromagnetic lens working current, and then start the high voltage power supply to put the device in the spinning state and complete the basic programmable control of the magnetic field.

[0025] Step (3) Active control and coupling of thermal field: As the core innovative step of this invention, the silicone rubber heating plate is tightly attached to the center of the receiving plate of the electrospinning device to ensure uniform heat transfer; after setting the target temperature of the receiving plate, the heating program is started and preheated for 30 minutes to ensure that the temperature of the receiving plate is uniform and stable; the key is that the temperature field, as the core control parameter, does not exist independently, but forms a dynamic synergistic coupling system with the component field (Fe3O4 doping amount) in step (1) and the magnetic field (electromagnetic lens current) in step (2), breaking the limitations of the original two-field control. By adjusting the temperature field parameters, in combination with the magnetic force and component content, the unpredictable technical effect of the interaction of the three fields is achieved, providing core support for the programmable control of nanofiber cross-scale structure.

[0026] Step (4) Preparation of nanocomposite fibers: Start the micro-injection pump so that the magnetic electrospinning solution overcomes the surface tension and forms a stable charged jet under the triple synergistic effect of the high voltage electrostatic force, the controllable magnetic field force of the electromagnetic lens, and the preset temperature field mentioned in step (3); after the jet moves to the constant temperature receiving plate, the solvent evaporates quickly and the fiber solidifies and forms a film, and a magnetic PAN / Fe3O4 nanofiber film with a cross-scale controllable structure can be obtained; among them, the temperature field in step (3) is the key to realizing the programmable design of nanofiber structure from the molecular scale to the macro scale. Its coupling effect with the magnetic and component fields effectively solves the technical pain point of performance trade-off in the original two-field control, and achieves the cross-scale precise control effect that the existing technology cannot achieve.

[0027] In step (1) of this invention, the mass ratio of DMF solvent to PAN powder is 0.2:1, the mass ratio of Fe3O4 nanoparticles to PAN powder is 0.2:1, and the amount of Triton X-100 dispersant added is equal to the amount of Fe3O4 nanoparticles; in step (2), the distance between the syringe needle and the collecting electrode is 16 cm, the distance between the electromagnetic lens and the collecting electrode is 8 cm, the propulsion rate of the micro-injection pump is 0.8 mL / h, the working current of the electromagnetic lens is 1 A, the inner diameter of the electromagnetic lens is 188 mm, the number of turns of the excitation coil is 1360, and the electrostatic high voltage is 15 kV.

[0028] The target temperature of the receiving plate in step (3) of this invention is 30℃~60℃. This temperature range can both accelerate the evaporation of DMF solvent to induce the orientation and crystallization of PAN molecular chains, and ensure the sufficient fluidity and dynamic orientation of Fe3O4 nanoparticles under the action of the electromagnetic lens magnetic field.

[0029] The temperature field described in step (3) of this invention, together with the component field formed by the doping amount of Fe3O4 nanoparticles in step (1) and the magnetic field formed by the electromagnetic lens current in step (2), form a dynamic synergistic coupling system. By adjusting the temperature field parameters, and in conjunction with the magnetic force and component content, the unpredictable technical effect of the interaction of the three fields can be achieved, providing core support for the programmable control of nanofiber cross-scale structures.

[0030] The cross-scale programmable control mentioned in step (4) of this invention includes: using a temperature field to reduce the viscosity of the spinning solution, improving the response efficiency of Fe3O4 nanoparticles under a magnetic field, and realizing molecular-scale control of PAN chain segment arrangement and particle orientation; at the same time, using a temperature field to control the fiber deposition thickness, realizing the customization of macroscopic porosity, fiber density and film mechanical properties.

[0031] The magnetic PAN / Fe3O4 nanofiber film described in step (4) of this invention has an average fiber diameter of 266.44~300.84 nm, a film thickness of 0.642~0.950 mm, and a deposition circle area of ​​73.09~93.46 cm².

[0032] The tensile stress of the magnetic PAN / Fe3O4 nanofiber film described in step (4) of this invention is 787.451~1624.035 kPa, the saturation magnetization is 2.93~9.0 emu / g, and the coercivity is 36.86~108.7 Oe.

[0033] The magnetic PAN / Fe3O4 nanofiber film described in step (4) of this invention has a porosity of 22.2%~42.8% and a fiber density of 57.2%~77.8%.

[0034] The electromagnetic lens-mediated thermo-magnetic-component multi-field coupling system of the present invention consists of an electromagnetic lens magnetic field module, a temperature-controlled receiving plate module, and a flat electrospinning module; the electromagnetic lens generates a controllable gradient magnetic field through a magnetic yoke, an excitation coil, and a DC power supply; the temperature-controlled receiving plate module includes a silicone rubber heating plate to provide precise temperature control of 303~333 K for the receiving plate; the magnetic PAN / Fe3O4 nanofiber film prepared by the method is used for high-performance triboelectric nanogenerators or lithium-ion battery separators.

[0035] The technical solution of the present invention will be further described below with reference to the embodiments: Example 1: In this embodiment, the receiving plate temperature was set to room temperature, and the electromagnetic lens excitation current was set to 0 A. Fe3O4-doped PAN / DMF spinning solution was prepared, and electrospinning was carried out for 2 hours under the process parameters of 15 kV electrospinning voltage, 16 cm spinning spacing, and 0.8 mL / h feed rate to obtain a composite nanofiber film.

[0036] Example 2: In this embodiment, the receiving plate temperature was set to room temperature, the electromagnetic lens excitation current was set to 1 A, and Fe3O4-doped PAN / DMF spinning solution was prepared. Under the process parameters of electrospinning voltage of 15 kV, spinning spacing of 16 cm, and feed rate of 0.8 mL / h, electrospinning was carried out for 2 h to prepare a composite nanofiber film.

[0037] Example 3: In this embodiment, the receiving plate temperature was selected as 30 ℃, the electromagnetic lens excitation current was 1 A, and Fe3O4-doped PAN / DMF spinning solution was prepared. Under the process parameters of electrospinning voltage of 15 kV, spinning spacing of 16 cm, and feed rate of 0.8 mL / h, electrospinning was carried out for 2 h to prepare composite nanofiber film.

[0038] Example 4: In this embodiment, the receiving plate temperature was selected as 40 ℃, the electromagnetic lens excitation current was 1 A, and Fe3O4-doped PAN / DMF spinning solution was prepared. Under the process parameters of electrospinning voltage of 15 kV, spinning spacing of 16 cm, and feed rate of 0.8 mL / h, electrospinning was carried out for 2 h to prepare composite nanofiber film.

[0039] Example 5: In this embodiment, the receiving plate temperature was selected as 50 ℃, the electromagnetic lens excitation current was 1 A, and Fe3O4-doped PAN / DMF spinning solution was prepared. Under the process parameters of electrospinning voltage of 15 kV, spinning spacing of 16 cm, and feed rate of 0.8 mL / h, electrospinning was carried out for 2 h to prepare composite nanofiber film.

[0040] Example 6: In this embodiment, the receiving plate temperature was selected as 60 ℃, the electromagnetic lens excitation current was 1 A, and Fe3O4-doped PAN / DMF spinning solution was prepared. Under the process parameters of electrospinning voltage of 15 kV, spinning spacing of 16 cm, and feed rate of 0.8 mL / h, electrospinning was carried out for 2 h to prepare composite nanofiber film.

[0041] The nanofiber samples prepared in Examples 1 to 6 were characterized by morphology (SEM), fiber diameter statistics, film thickness and deposition circle area, and systematic tests such as XRD phase analysis, mechanical properties, magnetic properties, porosity and fiber density were carried out.

[0042] 1. SEM Characterization: The morphology of nanofibers prepared under six different experimental conditions in Examples 1-6 was observed using an S-4800 SEM at 5.0 kV and magnified 5000 times. The diameter of 40 nanofibers prepared under each of the four conditions was measured using ImageJ. Figure 2 The image shows SEM images of nanofibers prepared under six different experimental conditions. Figure 2 In Figure 'a', the nanofibers are SEM images prepared under conditions of room temperature and an electromagnetic lens excitation current of 0 A. Figure 2 Image b in the image is a SEM image of the nanofibers prepared at room temperature with an electromagnetic lens excitation current of 1A. Figure 2 In the image, c represents the SEM image of the nanofibers prepared at a temperature of 30 ℃ and an electromagnetic lens excitation current of 1 A. Figure 2 In the image, d represents the SEM image of the nanofibers prepared at a temperature of 40 ℃ and an electromagnetic lens excitation current of 1 A. Figure 2 In the image, 'e' represents the SEM image of the nanofibers prepared at a temperature of 50 °C and an electromagnetic lens excitation current of 1 A. Figure 2 Image f is a SEM image of nanofibers prepared at a temperature of 60 ℃ and an electromagnetic lens excitation current of 1 A. From Figure 2As can be seen, compared with the sample under no magnetic field conditions (Figure 2a), the nanofibers after the introduction of a magnetic field (Figure 2bf) have a finer diameter and a more uniform distribution, indicating that the directional stretching effect of the magnetic field effectively suppresses jet whipping and improves the uniformity of fiber morphology. As the temperature gradually increases from room temperature to 50 ℃ (Figure 2be), the fiber diameter continues to decrease and the distribution further narrows, reaching the optimal state at 50 ℃ (Figure 2e), demonstrating the synergistic control effect of the thermal field and the magnetic field: the temperature accelerates solvent evaporation, solidifies the jet in advance, and effectively "freezes" the magnetic field-induced directional stretching conformation, avoiding viscoelastic shrinkage. When the temperature is further increased to 60 ℃ (Figure 2f), the fiber diameter shows a slight rebound, and the distribution also widens slightly, indicating that excessively high temperatures will cause the jet to solidify prematurely, resulting in the magnetic field energy not being able to fully couple into the jet body, weakening the synergistic control effect of multiple fields. Overall, the matching degree of temperature and magnetic field directly determines the morphology and diameter distribution of nanofibers, and the optimal structural control effect can be achieved under the conditions of 50 ℃ and 1A magnetic field. The average diameter of nanofibers is as follows Figure 3 As shown, applying only a 1A room-temperature magnetic field significantly reduced the average fiber diameter by 15.5% from 355.90 nm in the control group to 300.84 nm, while simultaneously improving diameter uniformity by 23.9% (standard deviation decreased from 50.73 nm to 38.61 nm). This change is mainly attributed to the Lorentz force exerted on the charged jet by the gradient magnetic field, which, in conjunction with the electrostatic tensile force, enhances the effective tensile stress. Simultaneously, the magnetic field can stabilize the jet morphology by controlling the ion flow behavior in the jet and suppressing non-axisymmetric disturbances. More importantly, the magnetic field and thermal field exhibit a clear synergistic regulatory effect: under a constant 1A magnetic field, when the temperature of the receiving plate is increased to 50 °C, the fiber diameter further decreases by 11.4% to 266.44 nm compared to the room-temperature magnetic field group (an overall decrease of 25.1% compared to the non-magnetic control group), and the diameter distribution uniformity is significantly improved by 40.1% (standard deviation decreased to 30.40 nm). This synergistic effect stems from the complementarity of the two in terms of timing and target: the magnetic field mainly acts on the jet flight stage, enhancing axial directional stretching; while the increased temperature of the receiving plate accelerates solvent evaporation and jet solidification at the deposition interface, effectively inhibiting the spreading and fusion of fibers after deposition, thereby efficiently "freezing" the fine stretching conformation induced by the magnetic field.

[0043] 2. Thickness Testing: The thickness of the nanofiber films prepared under six different experimental conditions in Examples 1-6 was tested using a thickness gauge. Ten tests were performed on each sample under each experimental condition, and the average value was taken. Figure 4As shown. A comparison revealed that, under the same temperature conditions, the influence of the magnetic field in Example 2 (thickness 0.642 mm) and Example 3 (thickness 0.950 mm) went beyond the scope of simple fiber deposition efficiency. The core physical mechanism lies in the fact that when a charged jet passes through an axisymmetric gradient magnetic field, the radial component of the Lorentz force provides a centripetal force pointing towards the axis, effectively suppressing the jet whipping instability dominated by charge repulsion. The jet trajectory thus becomes more collimated, and the deposition area becomes more concentrated. In Examples 4 (thickness 0.907 mm), 5 (thickness 0.930 mm), and 6 (thickness 0.876 mm), the film thickness decreased from 0.950 mm to 0.907 mm (a decrease of approximately 4.5%) when the temperature increased from 30 °C to 40 °C. This was due to the dual regulation of the thermal field: the increased temperature reduced the solution viscosity, enhancing the jet stretching under electric-magnetic field coupling; simultaneously, it accelerated solvent evaporation, causing the jet to solidify prematurely, inhibiting lateral spreading and fusion, and together forming a thinner, denser deposition layer. When the temperature rose to 50 °C, the thickness slightly increased back to 0.930 mm, indicating that the multi-field competition had reached a new equilibrium: the increased conductivity enhanced the electric field stretching force, the chain segment mobility promoted stress relaxation, and the decreased surface tension stabilized the jet morphology. These factors partially offset the over-solidification effect, allowing the deposited fibers to retain a certain degree of flexibility, resulting in a slight increase in the deposition thickness. When the temperature reaches 60 ℃, the thickness is 0.876 mm, showing a new dynamic equilibrium: solvent evaporation is nearing completion, and the solution rheology tends to stabilize; the high temperature of the receiving plate promotes thermal fusion between fibers, enhancing the integrity of the fiber network, while the Joule heating of the electromagnetic lens and the temperature of the receiving plate form a gradient thermal environment, subtly extending the stretchable window of the jet, and ultimately controlling the film thickness.

[0044] 3. Deposition spherical area measurement: The deposition spherical area of ​​the nanofiber films prepared under five different experimental conditions in Examples 2-6 was measured using measurement methods, such as... Figure 5 As shown. Example 2 (deposition circle area is 93.46 cm²) 2 Example 1) and Example 2) (deposition circle area is 73.09 cm²) 2 Under the same temperature conditions, the nanofiber film prepared with magnetic field assistance has a larger deposition circle area. Example 4 (deposition circle area is 81.52 cm²) 2 Example 5 (deposition circle area is 76.15 cm²) 2 Example 6 and Example 7 (deposition circle area is 85.06 cm²) 2After introducing a 1A magnetic field, the deposition area significantly decreased to 73.09 cm², directly reflecting the dual effects of the magnetic field's focusing and ordering: the axial magnetic field inhibited jet whipping through the Lorentz force, reducing the landing area; simultaneously, it induced the orientation of Fe3O4 particles and PAN molecular chains along the field, increasing the packing density, which macroscopically manifested as a shrinkage in the deposition area. Under a constant 1A magnetic field, the area rebounded to 81.52 cm² when the temperature rose to 40 ℃, stemming from the kinetic competition between thermal relaxation and magneto-ordering: while increasing the temperature promoted local rearrangement, it weakened the stability of the orientation structure, and accelerated solidification weakened the adhesion between fibers, resulting in a slightly looser packing and a slight increase in area. When the temperature rose to 50 ℃, the area decreased to 76.15 cm², achieving a new equilibrium of thermo-magnetic synergy: thermal energy neither induced significant relaxation nor hindered the tight stacking of molecular chains within the oriented framework, while the faster solidification rate "froze" the highly oriented structure, achieving more efficient filling. When the temperature rises to 60 ℃, excessively rapid curing kinetics dominate the molding process: solvent evaporation accelerates dramatically, shortening the fluid state window and preventing the magnetic field-induced orientation from being fully completed before curing. Simultaneously, microscopic defects are introduced, leading to a decrease in orderliness and density, macroscopically manifested as a rebound in the deposition area. In summary, a 1A magnetic field can significantly reduce the nanofiber deposition area. Under a constant magnetic field, the deposition area exhibits a trend of first increasing, then decreasing, and then increasing again with rising temperature. This change is essentially the result of a dynamic balance between the kinetic competition between thermally induced relaxation and magnetically induced ordering, as well as the thermo-magnetic synergistic effect.

[0045] 4. Mechanical property testing: The mechanical properties of the nanofiber films prepared under five different experimental conditions in Examples 2-6 were tested using a computer-controlled tensile stress testing machine. Samples under each experimental condition were tested five times, and the average value was taken. Figure 6The figure shows the stress-strain values ​​of nanofiber films prepared under five different experimental conditions. Comparison reveals that Example 2 (stress of 787.451 kPa) and Example 3 (stress of 1310.459 kPa), with the addition of a magnetic field in Example 3, resulted in a 66.4% increase in the mechanical properties of the nanofibers. This improvement stems from the dual regulatory mechanism of the magnetic field: on the one hand, it regulates the surface charge distribution of the jet through Lorentz force, enhancing the electrostatic interaction between PAN molecular chains; on the other hand, it induces Fe3O4 nanoparticles to align orderly along magnetic field lines, forming a "chain-particle" composite orientation structure with the PAN molecular chains, inhibiting chain slippage and strengthening stress transmission, thereby significantly improving the fiber tensile strength. Under a 1A magnetic field, the fiber tensile strength exhibits a phased change with temperature, dominated by the synergistic regulation of the magnetic field and temperature on the molecular chain and particle arrangement. When the temperature was increased from 30 °C to 50 °C, the strength gradually increased from Example 3 (stress of 1310.459 kPa) to Example 5 (stress of 1595.276 kPa). The moderate increase in temperature provided thermal kinetic energy for the molecular chains, allowing them to further optimize their arrangement and fill structural defects based on the magnetic field orientation. At the same time, it promoted a tighter bond between the Fe3O4 particles and the PAN chain interface, improving structural density and load-bearing capacity. When the temperature was increased from 50 °C to 60 °C, the strength only increased slightly to Example 6 (stress of 1624.035 kPa), with a growth rate of only 1.8%. The increase in temperature intensified the thermal motion of the molecular chains, causing a slight disturbance to the ordered arrangement induced by the magnetic field. However, the overall structure remained stable, and the thermally induced structural repair effect still dominated. Therefore, the strength only increased slowly. If the temperature continued to rise significantly, excessive thermal motion would significantly damage the orientation and crystal structure, leading to a decrease in tensile strength.

[0046] 5. XRD test: From the XRD pattern ( Figure 7The study clearly demonstrates the synergistic regulatory effect of temperature and magnetic field on the crystallization behavior of PAN / Fe3O4 composite nanofibers. In Example 2 (30 °C, 0A), the fiber diffraction peak intensity was the weakest and the crystallinity was the lowest, with the polymer molecular chains exhibiting random arrangement without external field constraint. After introducing a magnetic field in Example 3 (30 °C, 1A), the diffraction peak intensity significantly increased. The magnetic field, through coupling the Lorentz force and magnetization force, induced the directional arrangement of PAN molecular chains and Fe3O4 nanoparticles, forming heterogeneous nucleation sites and effectively improving crystallinity. Under a constant magnetic field, when the temperature of the receiving plate increased from 30 °C to 50 °C, the diffraction peak intensity continued to increase and tended to a high plateau, reflecting the ternary synergistic effect of heat-magnetism-particles: the increase in temperature enhances the mobility of molecular chains, making them more easily oriented along the magnetic field; at the same time, thermal activation strengthens the magneto-nucleation effect of Fe3O4 particles, and the coupling of the three significantly improves the crystallization promotion effect. When the temperature continued to rise to 60 °C, the diffraction peak intensity was still higher than that of the low-temperature sample, but the increase slowed down. Excessive thermal kinetic energy intensifies molecular chain motion, causing some oriented chain segments to loosen. The fixing effect of the magnetic field orientation tends to saturate, the system enters dynamic equilibrium, and the increase in crystallinity plateaus. These results indicate that there exists an optimal thermal-field matching range for multi-field coupling-controlled crystallization. Within this range, the internal and external field orientation driving forces match the molecular chain dynamics optimally, allowing for the optimal control of the crystal structure.

[0047] 6. Magnetic property testing: The magnetic properties of the nanofiber films prepared under three different experimental conditions (Examples 2, 3, and 5) were tested using a comprehensive physical property measurement system. The magnetic property values ​​are shown in the figure below. Figure 8As shown, the saturation magnetization Ms of the three groups of samples were 2.93, 3.29, and 9.0, respectively, showing a significant increasing trend, especially under the synergistic effect of a magnetic field at +60 ℃, where Ms achieved an order-of-magnitude increase. From a magnetic perspective, Ms represents the maximum magnetization achievable by a material under an external field, determined by the total magnetic moment of the effective magnetic particles per unit volume, and is directly related to the Fe3O4 content, dispersion state, and magnetic coupling strength between particles. Without magnetic field assistance, Fe3O4 nanoparticles are randomly distributed in the fiber and prone to local aggregation, resulting in mutual cancellation of magnetic moments between particles and low utilization of effective magnetic moments, thus Ms is the lowest. After applying the magnetic field of the electromagnetic lens, the magnetic field induces preliminary orientation of the particles, suppressing aggregation and slightly increasing the number of effective magnetic moments, thus Ms slightly increases to 3.29. When the temperature was increased to 60 ℃, the viscosity of the polymer matrix decreased significantly, and the degrees of freedom of Fe3O4 particles increased dramatically. Under the action of a magnetic field, highly uniform oriented arrangement and tight chain assembly were achieved, forming strong magnetic coupling between particles, maximizing the superposition of effective magnetic moments, and ultimately resulting in a sharp increase in Ms to 9.0. This result fully demonstrates that thermomagnetic synergy can significantly improve the dispersion and orientation order of magnetic particles, thereby greatly increasing the saturation magnetization. The coercivity Hc of the three groups of samples were 99.72, 36.86, and 108.7, respectively, showing a special pattern of "first decreasing and then significantly increasing". Under the condition of 30 ℃ without a magnetic field, Fe3O4 particles were randomly distributed and locally agglomerated, with disordered magnetic domain structure and high resistance to domain wall movement, thus exhibiting high coercivity. After applying a magnetic field, the particles initially oriented at 30 ℃, the magnetic anisotropy of the material was enhanced, the magnetic domain structure tended to be more regular, and the domain flipping energy barrier was reduced, resulting in a decrease in coercivity and exhibiting typical soft magnetic behavior. When the temperature rises to 60 ℃, the particles achieve high orientation in the magnetic field, forming a distinct one-dimensional chain-like magnetic structure. The anisotropy of shape and the exchange coupling between particles are dramatically enhanced, and the reverse magnetic field required for domain flipping is significantly increased, ultimately leading to a substantial increase in coercivity to 108.7. This change indicates that coercivity is jointly determined by magnetic anisotropy and magnetic domain structure, and that a highly oriented chain-like structure can significantly improve coercivity.

[0048] 7. Porosity and Fiber Density Testing: In Example 1 (room temperature, no magnetic field), the jet is dominated by viscous force, surface tension, and inertial force, exhibiting significant bending and whipping instability. The fiber diameter is coarse, the deposition trajectory is disordered, and the fibers are only bound together by van der Waals forces and mechanical interlocking, with weak interfacial diffusion, forming a loose structure with high porosity (42.8%) and low density (57.2%). In Example 2 (introducing a 1A steady-state magnetic field), the magnetic field achieves a dual regulation of axial stretching and radial stabilization of the charged jet by the Lorentz force, refining the fiber diameter and suppressing lateral instability, and magnetization driving the Fe3O4 nanoparticles to align along the magnetic field: improving the axial stiffness and stability of the jet, significantly increasing the orderliness of deposition, reducing the porosity to 31.9%, and increasing the density to 68.1%. After coupling the temperature field, a clear synergistic and competitive effect was observed. In Examples 3 to 4 (30–40 °C), increasing the temperature reduced the solution viscosity, enhanced magnetostrictive stretching, and accelerated solvent evaporation. At 40 °C, the magnetic field stretching aging time and thermal curing time reached optimal matching, allowing the jet to be fully stretched and rapidly shaped. Simultaneously, moderate segment diffusion occurred at the fiber interface, achieving controllable fusion and obtaining a dense, ordered fiber network with a minimum porosity of 22.2% and a maximum density of 77.8%. When the temperature increased to Examples 5 to 6 (50–60 °C), the control mechanism changed. Excessive solvent evaporation caused premature jet curing, limiting the magnetic field stretching effect. The fiber diameter rebounded and defects appeared, and the trajectory disorder increased. Simultaneously, the substrate temperature approached the polymer's glass transition temperature, leading to excessive thermal fusion at fiber intersections. Although this partially filled micropores, it caused cross-sectional deformation, decreased topological uniformity, and microscopic defects, resulting in a porosity increase to 28.5% (50 °C) and 30.1% (60 °C), forming an adhesive, non-uniform network. See also Figure 9 , Figure 10 In summary, the lowest fiber porosity and highest density correspond to the magnetic properties... hot The optimal dynamic matching of curing timescales must simultaneously avoid premature curing and over-fusion. This mechanism provides a theoretical basis and process guidance for the controllable fabrication of fiber scaffolds with customized pore structures and mechanical properties.

[0049] This invention discloses an electromagnetic lens-mediated heat dissipation method. magnetic A programmable method for preparing PAN / Fe3O4 nanofibers with multi-field coupling of components. Addressing the limitations of existing technologies that only allow for two-field control (magnetic field and component composition), with temperature as a passive environmental parameter and lacking multi-field synergistic coupling in temperature-related studies, this invention uses temperature as the active control core variable. It constructs a dynamic synergistic coupling system with the electromagnetic lens-mediated magnetic field and the Fe3O4 doping component field. Through spinning solution preparation, assembly and debugging of the electromagnetic lens and electric field device, active thermal field control coupling, and multi-field synergistic electrospinning, programmable and precise control of the PAN / Fe3O4 nanofiber structure from the molecular to the macroscopic scale is achieved. This invention overcomes the limitations of traditional two-field independent control techniques, achieving programmable control of the PAN / Fe3O4 nanofiber structure from the molecular to the macroscopic scale through thermal... magnetic The synergistic effect of the three fields optimizes the jet stretching, solidification kinetics, and deposition interface behavior, effectively addressing the core challenges of imbalance between magnetic and mechanical properties and poor structural controllability in fibers. This significantly improves fiber diameter uniformity, density, mechanical properties, and magnetic response. The resulting composite nanofibers can be used in advanced devices such as high-performance triboelectric nanogenerators and lithium-ion battery separators, providing reliable technical support for the controllable preparation and large-scale application of functional composite nanofibers.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A programmable preparation method of PAN / Fe304 nanofiber with electromagnetic lens mediated thermo-magnetic-component multi-field coupling, characterized in that, Includes the following steps: Step (1): Prepare the spinning solution, specifically: weigh PAN powder, dissolve it in DMF solvent, and obtain a uniform PAN / DMF mother liquor by magnetic stirring and ultrasonic dispersion treatment; add Fe3O4 nanoparticles and dispersant Triton X-100 to the mother liquor, and ultrasonically disperse it again until there is no obvious agglomeration to obtain a magnetic electrospinning solution. Step (2): Assemble the electromagnetic lens and electric field device. Specifically, fix the syringe containing the magnetic electrospinning solution prepared in step (1) to the micro-injection pump, adjust the distance between the syringe needle and the collecting electrode, the distance between the electromagnetic lens and the collecting electrode, connect the positive and negative terminals of the DC high voltage power supply to the syringe needle and the collecting electrode respectively, set the micro-injection pump propulsion rate and the electromagnetic lens working current, and then start the high voltage power supply to complete the basic programmable control of the magnetic field. Step (3): Active control and coupling of the thermal field, specifically: attach the heating plate to the receiving plate of the electrospinning device, set the target temperature of the receiving plate, start the heating program and preheat, so that the temperature of the receiving plate is uniform and stable. Step (4): Prepare nanocomposite fibers, specifically: start the micro-injection pump, so that the magnetic electrospinning solution forms a stable charged jet under the synergistic effect of high voltage electrostatic force, electromagnetic lens controllable magnetic field force and the preset temperature field mentioned in step (3); after the jet moves to the constant temperature receiving plate, it is solidified by solvent evaporation and fiber solidification to obtain a magnetic PAN / Fe3O4 nanofiber film.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of DMF solvent to PAN powder is 0.2:1, the mass ratio of Fe3O4 nanoparticles to PAN powder is 0.2:1, and the amount of Triton X-100 dispersant added is equal to the amount of Fe3O4 nanoparticles; in step (2), the distance between the syringe needle and the collecting electrode is 16 cm, the distance between the electromagnetic lens and the collecting electrode is 8 cm, the propulsion rate of the micro-injection pump is 0.8 mL / h, the working current of the electromagnetic lens is 1 A, the inner diameter of the electromagnetic lens is 188 mm, the number of turns of the excitation coil is 1360, and the electrostatic high voltage is 15 kV; in step (3), the heating plate is a silicone rubber heating plate, and the preheating time is 30 minutes.

3. The preparation method according to claim 1, characterized in that, The target temperature of the receiving plate in step (3) is 30℃~60℃.

4. The preparation method according to claim 1, characterized in that, The temperature field described in step (3) forms a dynamic synergistic coupling system with the component field formed by the Fe3O4 nanoparticle doping amount in step (1) and the magnetic field formed by the electromagnetic lens current in step (2). By adjusting the temperature field parameters in conjunction with the magnetic field force and component content, the cross-scale structure of nanofibers under the interaction of the three fields can be programmably controlled.

5. The preparation method according to claim 1, characterized in that, The cross-scale programmable control mentioned in step (4) includes: using a temperature field to reduce the viscosity of the spinning solution, improving the response efficiency of Fe3O4 nanoparticles under a magnetic field, and realizing molecular-scale control of PAN chain segment arrangement and particle orientation; at the same time, using a temperature field to control the fiber deposition thickness, realizing the customization of macro-scale porosity, fiber density and film mechanical properties.

6. The preparation method according to claim 1, characterized in that, The magnetic PAN / Fe3O4 nanofiber film described in step (4) has an average fiber diameter of 266.44~300.84 nm, a film thickness of 0.642~0.950 mm, and a deposition circle area of ​​73.09~93.46 cm².

7. The preparation method according to claim 1, characterized in that, The tensile stress of the magnetic PAN / Fe3O4 nanofiber film described in step (4) is 787.451~1624.035 kPa, the saturation magnetization is 2.93~9.0 emu / g, and the coercivity is 36.86~108.7 Oe.

8. The preparation method according to claim 1, characterized in that, The magnetic PAN / Fe3O4 nanofiber film described in step (4) has a porosity of 22.2%~42.8% and a fiber density of 57.2%~77.8%.

9. The preparation method according to claim 1, characterized in that, The electromagnetic lens-mediated thermo-magnetic-component multi-field coupling system consists of an electromagnetic lens magnetic field module, a temperature-controlled receiving plate module, and a flat electrospinning module. The electromagnetic lens generates a controllable gradient magnetic field through a magnetic yoke, an excitation coil, and a DC power supply. The temperature-controlled receiving plate module includes a silicone rubber heating plate, which provides precise temperature control of 303~333 K for the receiving plate. The magnetic PAN / Fe3O4 nanofiber film prepared by the method is used for high-performance triboelectric nanogenerators or lithium-ion battery separators.

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