A magnetic carbon fiber oriented reinforced supercritical foamed thermally conductive and wear-resistant PEEK composite material and its preparation method

Abstract

This invention belongs to the field of high-performance polymer composite materials and provides a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material and its preparation method. This invention forms a continuous PEEK matrix, oriented magnetic carbon fiber and controllable micropore synergistic structure by surface oxidation of short-cut carbon fibers, in-situ anchoring of iron oxide, melt coating of PEEK with the same composition, magnetic field-induced orientation, supercritical carbon dioxide micropore foaming and annealing treatment. This achieves the maintenance of thermal conductivity, enhanced wear resistance, improved cell integrity and widening of processing window, and solves the problem of difficulty in balancing thermal conductivity network construction and melt flow, and micropore integrity and wear resistance. It is suitable for lightweight wear-resistant and thermally conductive engineering components.

Description

Technical Field

[0001] This invention relates to the field of high-performance polymer composite materials, specifically to a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material and its preparation method. Background Technology

[0002] Polyetheretherketone (PEEK), a specialty engineering plastic resistant to high temperatures, chemical media, and fatigue, is widely used in lightweight structural components, sliding friction parts, and thermal management components in aerospace, electronics, rail transportation, precision machinery, medical devices, and high-end equipment. In these applications, the material needs to maintain low density and a stable molding window while also possessing high thermal conductivity, dimensional stability, and wear-resistant load-bearing capacity to reduce localized heat buildup, frictional temperature rise, and long-term service damage. Supercritical carbon dioxide foaming can form a microporous structure without introducing chemical foaming residues, which is beneficial for weight reduction and regulating thermomechanical response; carbon fiber reinforcement is beneficial for constructing load-bearing and thermal conduction pathways. For PEEK-based composites, maintaining processing flow, thermal conduction pathways, cell integrity, and wear interface load-bearing capacity simultaneously under conditions of high melting temperature, high viscosity, and easy perturbation of cells by fillers has become a key technical direction that needs to be addressed when this type of material enters high-end lightweight, wear-resistant, and thermally conductive applications.

[0003] Existing polyetheretherketone (PEEK) foaming and composite material technologies have focused on improvements related to supercritical carbon dioxide, near-critical carbon dioxide, annealing crystallization, and composite fillers. For example, Chinese patent CN103435831A discloses a method for preparing PEEK foam materials using supercritical carbon dioxide, which obtains PEEK foam sheets through sheet saturation and high-temperature foaming. Another example is Chinese patent CN107177052B, which discloses lightweight PEEK or its composite materials with different degrees of crystallinity and their preparation methods, controlling the cell structure and crystallinity state through near-critical or supercritical carbon dioxide and annealing. However, these disclosed technologies primarily focus on PEEK cell formation, foaming ratio, or crystallinity control. They lack a systematic approach to addressing the structural maintenance of carbon fibers during high-temperature melting, magnetic field orientation, interface coating with the same composition, control of free magnetic particles, and the dual contradiction between thermal conductivity / wear resistance and microporous foaming. This still easily leads to problems such as decreased melt flow when fillers increase thermal conductivity and disturbance of cell integrity when enhancing wear resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material and its preparation method, which solves the problem that it is difficult to balance processing fluidity and thermal conductivity, as well as microporous structure integrity and wear resistance in current PEEK thermally conductive foamed composite materials.

[0005] This invention uses iron oxide to anchor short-cut carbon fibers, coat them with PEEK of the same composition, oriented them with a magnetic field, and controlled foaming with supercritical carbon dioxide. This allows the reinforcing phase to form an attractive heat-conducting and load-bearing path during melt processing and foaming, while reducing the disturbance of exposed particles and rigid fibers to the matrix flow and cell growth. This achieves a synergistic balance between processing and shaping, thermal conductivity, micropore integrity, and wear resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material, based on the final solid form composition of the composite material, comprises the following components in parts by weight: The matrix is ​​made of PEEK resin, 70.0–88.0 parts by weight; PEEK-coated magnetic carbon fiber intermediate, 8.0–25.0 parts by weight; Wherein, PEEK is polyetheretherketone, and the matrix is ​​formed by PEEK resin in the composite material to form a continuous matrix phase; The PEEK-coated magnetic carbon fiber intermediate includes chopped carbon fibers, iron oxide particles anchored to the surface of the chopped carbon fibers, and a PEEK coating layer covering the surface of the chopped carbon fibers and at least a portion of the surface of the iron oxide particles. The chopped carbon fibers anchored to the iron oxide particles constitute magnetic carbon fibers.

[0007] Furthermore, the composite material has a microporous structure formed by supercritical carbon dioxide foaming, wherein the pore D50 of the microporous structure is 5–80 μm; The PEEK-coated magnetic carbon fiber intermediate has a magnetic field-induced orientation structure in the continuous matrix phase, with an orientation factor of 0.60–0.95. The thickness of the PEEK coating layer is 20–300 nm, and the PEEK coating layer has the same chemical composition as the PEEK resin used in the matrix.

[0008] Furthermore, the PEEK-coated magnetic carbon fiber intermediate is prepared through the following steps: A1. Provides precursors for iron oxide-anchored surface-oxidized carbon fiber; A2. Mix 100 parts by weight of the iron oxide anchored surface oxidized carbon fiber precursor with 3–18 parts by weight of PEEK micro powder. A3. Under a nitrogen atmosphere, heat the material obtained in step A2 to 350–390°C and melt-coat it for 2–20 min under shear conditions of 20–120 r / min, so that PEEK forms a PEEK coating layer on the surface of the carbon fiber precursor anchored on the iron oxide surface. A4. After cooling to 120–180°C under a nitrogen atmosphere, the material is crushed and sieved through an 80–100 mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. A5. The quality control parameters of the PEEK-coated magnetic carbon fiber intermediate are: the PEEK coating coverage rate is 70-98%, and the proportion of free iron oxide particles in the intermediate to the total mass of iron oxide particles in the intermediate is not higher than 5.0 wt%.

[0009] Furthermore, the iron oxide anchored surface-oxidized carbon fiber precursor in step A1 is prepared through the following steps: B1. Provides surface-oxidized carbon fiber precursors; B2. Disperse 100 parts by weight of the surface-oxidized carbon fiber precursor in 500–1500 parts by weight of deionized water and purge with nitrogen gas; B3. Add ferric chloride hexahydrate and ferrous chloride tetrahydrate, wherein the molar ratio of Fe3+ to Fe2+ is 1.8–2.2:1, and the total amount of iron salt is determined according to the target loading of the obtained iron oxide particles relative to the surface oxidized carbon fiber precursor being 0.5–8.0 wt%. B4. At 60–85℃, adjust the pH of the system to 9.0–10.5 with ammonia water and keep it at the temperature for 1–4 hours to allow the iron oxide particles to nucleate and anchor in situ on the surface of the carbon fiber precursor. B5. Wash with deionized water until the pH of the filtrate is 6.0–8.0, then wash with ethanol 1–3 times; B6. Dry at 60–90℃ for 4–12 h to obtain the iron oxide anchored surface oxidized carbon fiber precursor; B7. The quality control parameters of the iron oxide anchored surface oxidized carbon fiber precursor are as follows: the loading of iron oxide particles relative to the surface oxidized carbon fiber precursor is 0.5–8.0 wt%, the particle size of iron oxide particles is 10–80 nm, and the proportion of unanchored iron oxide particles to the total amount of iron oxide particles is not higher than 8.0 wt%.

[0010] Furthermore, the surface-oxidized carbon fiber precursor in step B1 is prepared through the following steps: C1. A mixture of 100 parts by weight of chopped carbon fibers and 500–2000 parts by weight of an aqueous nitric acid solution, wherein the aqueous nitric acid solution has a mass fraction of 30–70 wt%. C2. Surface oxidation of the chopped carbon fibers is carried out at 50–90°C for 0.5–4 hours; C3. Wash with deionized water until the pH of the washing solution is 6.0–8.0, then wash with ethanol 1–3 times; C4. Dry at 80–120℃ for 4–12 h to obtain the surface-oxidized carbon fiber precursor; C5. The quality control parameters of the surface-oxidized carbon fiber precursor are: a mass loss rate of 0.1–5.0 wt% relative to the chopped carbon fiber before treatment, a fiber length retention rate of 80–99%, and a fiber length D50 of 50–500 μm for the surface-oxidized carbon fiber precursor.

[0011] Furthermore, the composite material is first formed into a magnetically oriented composite preform before supercritical carbon dioxide foaming. The magnetically oriented composite preform is prepared through the following steps: D1. 70.0–88.0 parts by weight of the matrix are dried with PEEK resin and 8.0–25.0 parts by weight of PEEK-coated magnetic carbon fiber intermediate; D2. Melt-mix at 360–390℃ for 1–8 min to obtain a melt composite; D3. The molten composite was placed in a magnetic field of 0.2–1.5T for 10–180s for orientation and then pressed and shaped under 0.5–10MPa. D4. Cool to 120–180℃ at a cooling rate of 20–150℃ / min to obtain a magnetic field oriented composite preform; D5. The orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.60–0.95.

[0012] Furthermore, in the PEEK-coated magnetic carbon fiber intermediate, the length D50 of the chopped carbon fiber is 50–500 μm, the diameter of the chopped carbon fiber is 5–10 μm, the particle size of the iron oxide particles is 10–80 nm, and the loading of the iron oxide particles relative to the chopped carbon fiber is 0.5–8.0 wt%. The microporous structure has a pore size of D10 of 2–20 μm, a pore size of D90 of 20–180 μm, and a pore size of D10 ≤ pore size of D50 ≤ pore size of D90, with a closed-cell rate of 50–95%. The PEEK coating layer has a PEEK coverage rate of 70–98% on the surface of the chopped carbon fibers; The proportion of free iron oxide particles in the composite material is no more than 0.5 wt% of the total mass of iron oxide particles in the composite material, and the composite material does not have an independent coating layer formed by silica, polydopamine or silane coupling agent; The thermal conductivity of the composite material is 0.60–3.00 W·m. -1 ·K -1The thermal conductivity is determined according to ISO 22007-2; the coefficient of friction of the composite material is 0.10–0.30, and the coefficient of friction is determined according to ASTM G 99.

[0013] As a concept of this invention, the present invention employs a design combining a PEEK-coated magnetic carbon fiber intermediate with a continuous PEEK matrix, primarily aimed at achieving a synergistic balance between processing fluidity and thermal conductivity / wear resistance. Existing technologies, to reduce the obstruction of carbon fibers to melt flow, typically reduce the amount of reinforcing phase or weaken the fiber network, but this weakens the thermal conductivity pathways and wear interface load-bearing capacity. To improve thermal conductivity and wear resistance, the carbon fiber content or orientation degree is often increased, but exposed fibers and free magnetic particles easily increase the system viscosity and disturb the foaming process. This invention, through surface oxidation, iron oxide anchoring, homogeneous PEEK coating, and magnetic field-induced orientation, enables the reinforcing phase to possess orientationability and good matrix compatibility. The PEEK coating layer reduces the abrupt disturbances of rigid interfaces to the melt and cells, and the oriented magnetic carbon fibers form a continuous thermal conductivity and load-bearing path, thereby achieving a synergistic unity of processing fluidity, thermal conductivity, micropore retention, and wear resistance.

[0014] This invention also discloses a method for preparing a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material, characterized by comprising the following steps: S1. Provide a pre-prepared PEEK-coated magnetic carbon fiber intermediate; S2. 70.0–88.0 parts by weight of the matrix are dried at 150–180°C for 2–8 hours with PEEK resin and 8.0–25.0 parts by weight of the PEEK-coated magnetic carbon fiber intermediate to obtain the dried material. S3. The dried material is melt-blended at 360–390°C for 1–8 min to obtain a melt composite. S4. The molten composite is placed in a magnetic field of 0.2–1.5T for 10–180s and then pressed and shaped under 0.5–10MPa. After pressing and shaping, it is cooled to 120–180℃ at a cooling rate of 20–150℃ / min to form a magnetically oriented composite preform. S5. The magnetic field-oriented composite preform is placed in carbon dioxide for saturation at a saturation pressure of 8–25 MPa, a saturation temperature of 35–120 °C, and a saturation time of 2–12 h. S6. After depressurization, the saturated magnetic field-oriented composite preform is foamed at a temperature of 240–340℃ for 5–1200s to obtain a foamed composite material. S7. Anneal the foamed composite material at 180–240℃ for 0.5–4h to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material.

[0015] Furthermore, the PEEK resin used as the matrix in step S2 is PEEK powder, PEEK particles, or a combination of both, wherein the particle size D50 of the PEEK powder is 5–80 μm. The melt mixing in step S3 is carried out in a twin-screw extruder, internal mixer or high-temperature torque rheology equipment, with a screw speed or rotor speed of 30–250 r / min.

[0016] Furthermore, the angle between the magnetic field direction and the target heat conduction direction in step S4 is 0–30°, and the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.60–0.95.

[0017] Furthermore, in step S6, the foaming ratio is controlled to 1.1–2.5 by limiting foaming within the mold.

[0018] Furthermore, after annealing in step S7, the resulting magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material has a cell D50 of 5–80 μm, a closed-cell rate of 50–95%, and a density of 0.70–1.25 g / cm³. 3 .

[0019] Furthermore, the PEEK-coated magnetic carbon fiber intermediate retains 60–95% of the chopped carbon fiber length D50 after melt mixing compared to the chopped carbon fiber length D50 before melt mixing, and the PEEK coating coverage after melt mixing retains 60–95% of the PEEK coating coverage before melt mixing.

[0020] As another aspect of this invention, the present invention employs a preparation process involving the prefabrication of a PEEK-coated magnetic carbon fiber intermediate, melt mixing, magnetic field orientation, compression molding, supercritical carbon dioxide saturated foaming, and annealing. This process is primarily used to achieve, fix, or amplify the aforementioned synergistic effects. Existing technologies, if only the mixing and dispersion are strengthened, can easily cause shear damage to the short-cut carbon fibers and destruction of the coating layer; if only the foaming conditions are strengthened, the rigid reinforcing phase may disturb cell growth; if only heat conduction is pursued, the melt flow window may become narrower. This invention first uses a PEEK coating layer to fix and anchor the carbon fibers with iron oxide (Fe3O4). Then, under limited temperature, time, magnetic field strength, pressure, cooling rate, carbon dioxide saturation conditions, foaming conditions, and annealing conditions, the structure is constructed. This ensures that the intermediate maintains high structural integrity before entering the foaming process and maintains a directional heat-conducting path and stable microporous structure after foaming, thereby matching the product structure with the preparation path.

[0021] Short-cut carbon fibers primarily serve to construct thermal conductivity pathways and bear wear at the interface, while iron oxide (Fe3O4) particles mainly impart magnetic field response to the short-cut carbon fibers and promote orientation control. While the presence of short-cut carbon fibers alone or in excessive amounts improves thermal conductivity and load-bearing capacity, it also increases melt viscosity, fiber agglomeration, and cell disturbance, impairing processing fluidity and micropore integrity. Conversely, the presence of iron oxide (Fe3O4) particles alone or in excessively high proportions, while beneficial for magnetic response, easily leads to particle migration and localized defects, negatively weakening interface stability and wear resistance. This invention, through surface oxidation anchoring, PEEK co-composition coating, coating coverage control, and magnetic field orientation, fixes iron oxide (Fe3O4) particles on the surface of short-cut carbon fibers, with the PEEK coating layer buffering interface abrupt changes. The short-cut carbon fibers form orientation paths in the magnetic field, and the two mutually correct each other within the continuous PEEK matrix and microporous structure, ultimately balancing their mutually constraining performance characteristics.

[0022] In some embodiments, during the supercritical carbon dioxide foaming process, after carbon dioxide saturation, the magnetically oriented composite preform is depressurized and transferred to a foaming stage at a temperature of 240–340°C from a saturation pressure of 8–25 MPa. The foaming time is 5–120 s. The foaming ratio is controlled to be 1.1–2.5 using an in-mold confinement method during the foaming stage. The foamed composite material obtained after foaming is used as the quality control result of the foaming step by the foaming ratio, cell D50, and closed cell ratio.

[0023] In some implementations, the orientation factor is based on the direction of the applied magnetic field as a reference direction. The angle θ between the axis of the identifiable short-cut carbon fiber and the reference direction in the cross-sectional scanning electron microscope image of the magnetically oriented composite preform or foamed composite material is statistically analyzed and calculated according to the Herman orientation parameter formula f=(3 <cos 2 θ>-1) / 2 is calculated, and the calculated f is used as the orientation factor of PEEK-coated magnetic carbon fiber intermediate in magnetic field oriented composite preforms or foamed composite materials.

[0024] In some embodiments, the cell diameters D10, D50, and D90 are obtained by statistically analyzing the equivalent diameters of the cells in the cross-sectional scanning electron microscope images of the foamed composite material. The cell diameters D10, D50, and D90 are calculated based on the same batch of samples, the same cross-sectional direction, and the same image analysis aperture, and the statistical results satisfy D10 ≤ D50 ≤ D90.

[0025] In some embodiments, the PEEK coating layer forms a continuous or semi-continuous interface layer in the PEEK-coated magnetic carbon fiber intermediate. This continuous or semi-continuous interface layer covers the surface of the chopped carbon fiber and at least a portion of the exposed surface of the iron oxide particles. When analyzing the PEEK coating coverage using microscopic images, the ratio of the PEEK coating area to the identifiable outer surface area of ​​the chopped carbon fiber and the iron oxide particles is used as the PEEK coating coverage, and 70–98% is used as the release index for the intermediate.

[0026] In some embodiments, the free iron oxide particles are iron oxide particles that are not anchored to the surface of chopped carbon fibers and are not fixed by the PEEK coating layer in the intermediate stage, and are iron oxide particles that are not fixed to the PEEK-coated magnetic carbon fiber intermediate and dispersed in the continuous matrix phase in the composite material stage. The proportion of free iron oxide particles in the intermediate stage is obtained by dispersing the sample, separating the free particles, measuring the mass of the separated particles, and calculating the proportion of the mass of the separated particles to the total mass of iron oxide particles in the intermediate. The proportion of free iron oxide particles in the composite material stage is obtained by dispersing the sample, separating the free particles, measuring the mass of the separated particles, and calculating the proportion of the mass of the separated particles to the total mass of iron oxide particles in the composite material.

[0027] In some embodiments, in the in-situ nucleation and anchoring step of ferric oxide, the ammonia water is 25–28 wt% ammonia water or 5–10 wt% ammonia water prepared by mixing 25–28 wt% ammonia water with deionized water; the ammonia water is added dropwise to an aqueous dispersion system containing surface-oxidized carbon fiber precursor, ferric chloride hexahydrate and ferrous chloride tetrahydrate, and the pH value of the system is continuously monitored during the dropwise addition. When the pH value of the system reaches 9.0–10.5, the dropwise addition is stopped, and the reaction is kept at 60–85°C for 1–4 hours. The resulting solid is washed and dried before entering the PEEK melt coating step.

[0028] In some embodiments, in the washing steps of the surface-oxidized carbon fiber precursor and the iron oxide-anchored surface-oxidized carbon fiber precursor, the ethanol is one of anhydrous ethanol, 95 vol% ethanol, or 70 vol% ethanol; after washing with deionized water until the pH of the washing liquid or filtrate is 6.0–8.0, it is washed with ethanol 1–3 times. The washed solid corresponding to the surface-oxidized carbon fiber precursor is then dried at 80–120°C for 4–12 hours, and the washed solid corresponding to the iron oxide-anchored surface-oxidized carbon fiber precursor is then dried at 60–90°C for 4–12 hours.

[0029] In some implementations, when the thermal conductivity is determined according to ISO 22007-2, the test sample is an annealed foamed composite material. The thermal conductivity test is performed along the target thermal conductivity direction, and the angle between the target thermal conductivity direction and the magnetic field direction is 0–30°. During the test, the sample thickness, sample density, test direction, and thermal conductivity are recorded. When the friction coefficient is determined according to ASTM G 99, the test sample is an annealed foamed composite material. During the test, the material of the mating part, normal load, sliding speed, sliding distance, ambient temperature, and friction coefficient are recorded, and the recorded fields are saved in correspondence with the sample batch.

[0030] In some embodiments, the chopped carbon fiber length D50 retention rate after melt blending is calculated as the ratio of the chopped carbon fiber length D50 in the PEEK-coated magnetic carbon fiber intermediate after melt blending to the chopped carbon fiber length D50 in the PEEK-coated magnetic carbon fiber intermediate before melt blending; the PEEK coating coverage retention rate is calculated as the ratio of the PEEK coating coverage after melt blending to the PEEK coating coverage before melt blending. These two ratios are used to evaluate the structural retention state of the intermediate before entering the magnetic field orientation step after melt blending.

[0031] Beneficial technical effects 1. This invention enables carbon fibers to acquire magnetic field responsiveness through surface oxidation of short-cut carbon fibers and in-situ anchoring of iron oxide particles. Then, magnetic field-induced orientation forms a directional heat-carrying path, avoiding excessively high melt viscosity caused by simply increasing the amount of carbon fibers. This is beneficial for improving thermal conductivity and wear resistance while maintaining the processing window.

[0032] 2. In this invention, a PEEK coating layer with the same chemical composition as the PEEK resin used in the matrix is ​​used to cover the surface of the magnetic carbon fiber and a portion of the iron oxide particles. This creates a transition between the reinforcing phase and the continuous matrix phase with the same composition, reducing the disturbance of free magnetic particles and exposed fibers to cell growth, thereby helping to maintain the integrity of the microporous structure.

[0033] 3. The present invention combines melt mixing, magnetic field orientation, compression molding, carbon dioxide saturation, in-mold confined foaming and annealing in a continuous manner, so that the intermediate obtains an oriented structure before foaming and stabilizes its morphology after annealing. Compared with the method of relying solely on filler reinforcement or single foaming control, it is more conducive to taking into account lightweight, dimensional stability and wear interface bearing capacity.

[0034] 4. This invention defines the structure and properties of composite materials by using quality control indicators such as cell size D10, cell size D50, cell size D90, closed-cell ratio, orientation factor, PEEK coating coverage, proportion of free iron oxide particles, thermal conductivity, and friction coefficient. This provides traceable quality control for the composite material from intermediates to foamed products, improving reproducibility and stability in engineering applications. Attached Figure Description

[0035] Figure 1 The fiber orientation angular distribution density diagrams are for Example 1, Comparative Example 9, and Comparative Example 10.

[0036] Figure 2 The Herman orientation factor box plots are for Examples 1, 9, and 10.

[0037] Figure 3 Box plots of PEEK coverage for Examples 1, 9, and 10.

[0038] Figure 4 The XPS Fe 2p spectra of Example 1, Comparative Example 9, and Comparative Example 10 are shown.

[0039] Figure 5 The above is a scatter plot of the EDS elemental atomic percentage for Example 1, Comparative Example 9, and Comparative Example 10.

[0040] Figure 6 The TGA quality retention rate-temperature curves are for Example 1, Comparative Example 9, and Comparative Example 10.

[0041] Figure 7 The figure shows a scatter plot of free iron oxide particles in Example 1, Comparative Example 9, and Comparative Example 10.

[0042] Figure 8 The diagram shows the equivalent diameter distribution density of bubbles in Examples 1, 8, and 10.

[0043] Figure 9 The cumulative distribution of equivalent cell diameters for Example 1, Comparative Example 8, and Comparative Example 10 is shown in the diagram.

[0044] Figure 10 The graphs show the D10 / D50 / D90 quantiles for Example 1, Comparative Example 8, and Comparative Example 10.

[0045] Figure 11 The box plots show the closed-pore ratios of Example 1, Comparative Example 8, and Comparative Example 10.

[0046] Figure 12 Two-dimensional correlation diagrams of thermal conductivity-orientation factor for Examples 1, 8, and 11.

[0047] Figure 13 The two-dimensional correlation diagram of friction coefficient-closed-pore ratio for Example 1, Comparative Example 8, and Comparative Example 11 is shown.

[0048] Figure 14 The graph shows the normalized performance trend of cell D50 for Examples 1, 8, and 11.

[0049] Figure 15 The high-temperature rheological viscosity-shear rate curves are for Example 1, Comparative Example 1, and Comparative Example 6.

[0050] Figure 16 The figures show the extrusion pressure-shear rate curves for Example 1, Comparative Example 1, and Comparative Example 6.

[0051] Figure 17 Box plots of fiber length retention rates for Example 1, Comparative Example 1, and Comparative Example 6.

[0052] Figure 18 Box plots of PEEK coating coverage retention rates for Example 1, Comparative Example 1, and Comparative Example 6.

[0053] Figure 19 This is a macroscopic optical photograph of the magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1.

[0054] Figure 20 The image shows a SEM image of the magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1. Figure 20 a is a low-magnification cross-sectional topography image; Figure 20 b and Figure 20 c is a magnified cross-sectional morphology diagram; Figure 20 d is a high-magnification image of the interface topography.

[0055] Figure 21 The image shows the TEM characterization of the magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1. Figure 21 a is a bright-field TEM image; Figure 21 b is a magnified TEM image of a local area; Figure 21 c is the HRTEM image. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0057] Example 1

[0058] Overall preparation scale and product form: In this example, 1 part by weight (1.00 g) was used to prepare a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. In the final solid form, the matrix PEEK resin was 70.0 parts by weight, and the PEEK-coated magnetic carbon fiber intermediate was 8.0 parts by weight. The matrix PEEK resin was commercially available polyetheretherketone powder with a purity ≥99.5%, a particle size D50 of 5 μm, and a moisture content ≤0.05 wt%; the PEEK micropowder was commercially available polyetheretherketone micropowder with a purity ≥99.5%; the chopped carbon fibers were commercially available chopped carbon fibers with a fiber length D50 of 50 μm and a diameter of 5 μm; ferric chloride hexahydrate, ferrous chloride tetrahydrate, nitric acid, ammonia, and ethanol were all commercially available analytical grade or equivalent reagents, and the deionized water conductivity was ≤1 μS / cm.

[0059] Preparation of surface-oxidized carbon fiber precursor: 100 parts by weight of chopped carbon fibers and 500 parts by weight of a 30 wt% nitric acid aqueous solution were prepared. The chopped carbon fibers were first added to an acid-resistant reaction vessel, followed by the nitric acid aqueous solution. The mixture was mechanically stirred at 200 r / min for 0.5 h under air atmosphere, normal pressure, and 50 °C. After treatment, the mixture was filtered, washed with deionized water until the pH of the washing solution reached 6.0, and then washed once with anhydrous ethanol. The washed solid was dried in a forced-air dryer at 80 °C for 4 h to obtain the surface-oxidized carbon fiber precursor. In this embodiment, the mass loss rate of the surface-oxidized carbon fiber precursor relative to the untreated chopped carbon fibers was 0.1 wt%, the fiber length retention rate was 80%, and the fiber length D50 was 50 μm.

[0060] Preparation of Fe3O4-anchored surface-oxidized carbon fiber precursor: 100 parts by weight of the surface-oxidized carbon fiber precursor was dispersed in 500 parts by weight of deionized water and pre-dispersed at 25°C for 20 min, followed by purging with nitrogen gas of ≥99.99% purity for 30 min. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added, with a Fe3+ to Fe2+ molar ratio of 1.8:1. The total amount of iron salts was determined according to the target loading of 0.5 wt% of the obtained Fe3O4 particles relative to the surface-oxidized carbon fiber precursor. The system was heated to 60°C, and 25 wt% ammonia solution was added dropwise. During the dropwise addition, the mixture was stirred at 300 r / min and the pH value was continuously monitored. The dropwise addition was stopped when the pH value reached 9.0, and the reaction was maintained at 60°C for 1 h. After the reaction, the mixture was filtered, washed with deionized water until the pH value of the filtrate was 6.0, then washed once with anhydrous ethanol, and dried at 60°C for 4 h to obtain the Fe3O4-anchored surface-oxidized carbon fiber precursor. The precursor contains 10 nm magnetite particles, and the proportion of unanchored magnetite particles to the total magnetite particles is 8.0 wt%.

[0061] Preparation of PEEK-coated magnetic carbon fiber intermediate: 100 parts by weight of magnetite-anchored surface-oxidized carbon fiber precursor and 3 parts by weight of PEEK micro powder were mixed and premixed for 10 min under a dry nitrogen atmosphere, then placed in a high-temperature shear mixing device. The material was heated to 350°C at 10°C / min and melt-coated for 2 min under a nitrogen atmosphere and a shear rate of 20 r / min, forming a PEEK coating layer on the surface of the magnetite-anchored surface-oxidized carbon fiber precursor. After coating, the mixture was cooled to 120°C at 30°C / min under a nitrogen atmosphere, crushed, and sieved through a 100-mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. In this embodiment, the PEEK coating layer thickness was 20 nm, the PEEK coating coverage was 70%, and the proportion of free magnetite particles in the intermediate to the total mass of magnetite particles in the intermediate was 5.0 wt%.

[0062] Preparation of magnetic field-oriented composite preform: 70.0 parts by weight of matrix PEEK resin and 8.0 parts by weight of PEEK-coated magnetic carbon fiber intermediate were vacuum dried at 150°C for 2 hours to obtain dried material. The dried material was added to a twin-screw extruder and melt-blended at 360°C and 30 r / min for 1 minute to obtain a melt composite. The melt composite was introduced into a preheated mold and placed in a 0.2T magnetic field for 10 seconds, with the angle between the magnetic field direction and the target thermal conduction direction being 0°. Subsequently, it was pressed and shaped at 0.5 MPa. After pressing and shaping, it was cooled to 120°C at 20°C / min to obtain the magnetic field-oriented composite preform. In this embodiment, the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.60.

[0063] Supercritical carbon dioxide foaming and annealing: The magnetically oriented composite preform was placed in a high-pressure carbon dioxide foaming autoclave, and carbon dioxide was introduced. Saturation was carried out at a saturation pressure of 8 MPa and a saturation temperature of 35°C for 2 hours. After saturation, the pressure was released, and the mixture was transferred to an in-mold confined foaming stage, where it was foamed at 240°C for 5 seconds to obtain the foamed composite material. The foaming ratio in this embodiment was 1.1. The foamed composite material was then annealed at 180°C for 0.5 hours and cooled to 25°C to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. The composite material in this embodiment did not have an independent coating layer formed by silica, polydopamine, or a silane coupling agent.

[0064] Quality Inspection Methods and Results: Three samples of the annealed foamed composite material were inspected. The equivalent diameter of the cells was statistically analyzed using cross-sectional scanning electron microscopy (SEM) images. In this embodiment, the cell diameter D10 was 2 μm, D50 was 5 μm, and D90 was 20 μm, with a closed-cell rate of 50%. The orientation factor, calculated using the Herman orientation parameter formula, was 0.60 ± 0.02. Microscopic image analysis showed a PEEK coverage rate of 70.0 ± 1.8%. The proportion of free iron oxide particles in the composite material was 0.5 wt% of the total iron oxide particles. The density was 1.25 ± 0.03 g / cm³. 3 The thermal conductivity, measured along the target heat conduction direction according to ISO 22007-2:2022, is 0.60 ± 0.03 W·m. -1 ·K -1 The coefficient of friction, measured according to ASTM G99-23, was 0.30±0.02. The mating parts were made of bearing steel. The normal load was 10N, the sliding speed was 0.10m / s, the sliding distance was 500m, and the ambient temperature was 25℃. The D50 retention rate of the chopped carbon fibers after melt-blending was 60%, and the PEEK coating coverage retention rate was 60%.

[0065] Features and application scenarios of this embodiment: This embodiment adopts a relatively conservative low-ratio scheme and mild process conditions that favor the low-value region. The amount of PEEK-coated magnetic carbon fiber intermediate is low, the foaming ratio is low, and the material density is high. It is suitable for lightweight engineering gaskets, sliding support sheets and heat-resistant structural spacers that require dimensional stability, low filler content, basic thermal conductivity and stable wear resistance.

[0066] Example 2

[0067] Overall preparation scale and product form: In this example, 1 part by weight (1.00 g) was used to prepare a magnetic carbon fiber-reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. In the final solid form, the matrix PEEK resin was 88.0 parts by weight, and the PEEK-coated magnetic carbon fiber intermediate was 25.0 parts by weight. The matrix PEEK resin was commercially available polyetheretherketone powder with a purity ≥99.5%, a particle size D50 of 80 μm, and a moisture content ≤0.05 wt%; the PEEK micropowder was commercially available polyetheretherketone micropowder with a purity ≥99.5%; the chopped carbon fibers were commercially available chopped carbon fibers with a fiber length D50 of 500 μm and a diameter of 10 μm; ferric chloride hexahydrate, ferrous chloride tetrahydrate, nitric acid, ammonia, and ethanol were all commercially available analytical grade or equivalent reagents, and the deionized water conductivity was ≤1 μS / cm.

[0068] Preparation of surface-oxidized carbon fiber precursor: 100 parts by weight of chopped carbon fibers and 2000 parts by weight of a 70 wt% nitric acid aqueous solution were prepared. The chopped carbon fibers were first added to an acid-resistant reaction vessel, followed by the nitric acid aqueous solution. The mixture was mechanically stirred at 300 r / min for 4 h at 90 °C under air atmosphere and normal pressure. After treatment, the mixture was filtered, washed with deionized water until the pH of the washing solution reached 8.0, and then washed three times with 95 vol% ethanol. The washed solid was dried in a forced-air dryer at 120 °C for 12 h to obtain the surface-oxidized carbon fiber precursor. In this embodiment, the mass loss rate of the surface-oxidized carbon fiber precursor relative to the untreated chopped carbon fibers was 5.0 wt%, the fiber length retention rate was 99%, and the fiber length D50 was 500 μm.

[0069] Preparation of Fe3O4 anchored surface-oxidized carbon fiber precursor: 100 parts by weight of surface-oxidized carbon fiber precursor was dispersed in 1500 parts by weight of deionized water and pre-dispersed at 25℃ for 40 min, followed by purging with nitrogen gas of ≥99.99% purity for 45 min. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added, with a Fe3+ to Fe2+ molar ratio of 2.2:1. The total amount of iron salts was determined according to the target loading of 8.0 wt% of the obtained Fe3O4 particles relative to the surface-oxidized carbon fiber precursor. The system was heated to 85℃, and 28 wt% ammonia water was added dropwise. During the dropwise addition, the mixture was stirred at 500 r / min and the pH value was continuously monitored. The dropwise addition was stopped when the pH value reached 10.5, and the reaction was maintained at 85℃ for 4 h. After the reaction was completed, the mixture was filtered, washed with deionized water until the pH of the filtrate reached 8.0, and then washed three times with 95 vol% ethanol. The filtrate was then dried at 90°C for 12 h to obtain a precursor of iron oxide-anchored surface-oxidized carbon fibers. The iron oxide particles in this precursor had a particle size of 80 nm, and the proportion of unanchored iron oxide particles to the total iron oxide particles was 2.0 wt%.

[0070] Preparation of PEEK-coated magnetic carbon fiber intermediate: 100 parts by weight of magnetite-anchored surface-oxidized carbon fiber precursor and 18 parts by weight of PEEK micro powder were mixed and premixed for 15 min under a dry nitrogen atmosphere, then placed in a high-temperature shear mixing device. The material was heated to 390°C at 8°C / min and melt-coated for 20 min under a nitrogen atmosphere and a shear rate of 120 r / min, forming a PEEK coating layer on the surface of the magnetite-anchored surface-oxidized carbon fiber precursor. After coating, the mixture was cooled to 180°C at 40°C / min under a nitrogen atmosphere, crushed, and sieved through an 80-mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. In this embodiment, the PEEK coating layer thickness was 300 nm, the PEEK coating coverage was 98%, and the proportion of free magnetite particles in the intermediate to the total mass of magnetite particles in the intermediate was 1.0 wt%.

[0071] Preparation of magnetic field-oriented composite preform: 88.0 parts by weight of matrix PEEK resin and 25.0 parts by weight of PEEK-coated magnetic carbon fiber intermediate were vacuum dried at 180°C for 8 hours to obtain dried material. The dried material was added to an internal mixer and melt-mixed at 390°C and 250 r / min for 8 minutes to obtain a melt composite. The melt composite was introduced into a preheated mold and placed in a 1.5T magnetic field for 180 seconds, with the angle between the magnetic field direction and the target thermal conduction direction being 30°. Subsequently, it was pressed and shaped under 10 MPa. After pressing and shaping, it was cooled to 180°C at 150°C / min to obtain the magnetic field-oriented composite preform. In this embodiment, the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.95.

[0072] Supercritical carbon dioxide foaming and annealing: The magnetically oriented composite preform was placed in a high-pressure carbon dioxide foaming autoclave, and carbon dioxide was introduced. Saturation was carried out for 12 hours at a saturation pressure of 25 MPa and a saturation temperature of 120°C. After saturation, the pressure was released, and the mixture was transferred to an in-mold confined foaming stage, where it was foamed at 340°C for 1200 seconds to obtain the foamed composite material. The foaming ratio in this embodiment was 2.5. The foamed composite material was then annealed at 240°C for 4 hours and cooled to 25°C to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. The composite material in this embodiment did not have an independent coating layer formed by silica, polydopamine, or a silane coupling agent.

[0073] Quality Inspection Methods and Results: Three samples of the annealed foamed composite material were inspected. The equivalent diameter of the cells was statistically analyzed using cross-sectional scanning electron microscopy (SEM) images. In this embodiment, the cell diameter D10 was 20 μm, D50 was 80 μm, and D90 was 180 μm, with a closed-cell rate of 95%. The orientation factor, calculated using the Herman orientation parameter formula, was 0.95 ± 0.01. Microscopic image analysis showed a PEEK coverage rate of 98.0 ± 1.0%. The proportion of free iron oxide particles in the composite material was 0.1 wt% of the total iron oxide particles. The density was 0.70 ± 0.02 g / cm³. 3 The thermal conductivity, measured along the target heat conduction direction according to ISO 22007-2:2022, is 3.00 ± 0.08 W·m. -1 ·K -1 The coefficient of friction was measured to be 0.10±0.01 according to ASTM G99-23. The mating parts were made of bearing steel. The normal load was 10N, the sliding speed was 0.10m / s, the sliding distance was 500m, and the ambient temperature was 25℃. The D50 retention rate of the chopped carbon fibers after melt-blending was 95%, and the PEEK coating coverage retention rate was 95%.

[0074] Features and application scenarios of this embodiment: This embodiment adopts an optimized scheme with higher load and orientation, saturation, foaming and annealing conditions in the high value region. The content of PEEK-coated magnetic carbon fiber intermediate is high, the degree of orientation is high, and the material density is low. It is suitable for heat-resistant sliding parts, electronic thermal management support parts and high-temperature wear-resistant linings with high requirements for thermal conductivity, low friction and lightweight.

[0075] Example 3

[0076] Overall preparation scale and product form: In this example, 1 part by weight (1.00 g) was used to prepare a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. In the final solid form, the matrix PEEK resin was 79.0 parts by weight, and the PEEK-coated magnetic carbon fiber intermediate was 16.5 parts by weight. The matrix PEEK resin was a combination of commercially available polyetheretherketone powder and PEEK particles, wherein the PEEK powder had a particle size D50 of 40 μm, a purity ≥99.5%, and a moisture content ≤0.05 wt%; the PEEK micropowder was commercially available polyetheretherketone micropowder with a purity ≥99.5%; the chopped carbon fibers were commercially available chopped carbon fibers with a fiber length D50 of 250 μm and a diameter of 7 μm; ferric chloride hexahydrate, ferrous chloride tetrahydrate, nitric acid, ammonia, and ethanol were all commercially available analytical grade or equivalent reagents, and the deionized water conductivity was ≤1 μS / cm.

[0077] Preparation of surface-oxidized carbon fiber precursor: 100 parts by weight of chopped carbon fibers and 1200 parts by weight of a 50 wt% nitric acid aqueous solution were prepared. The chopped carbon fibers were first added to an acid-resistant reaction vessel, followed by the nitric acid aqueous solution. The mixture was mechanically stirred at 250 r / min for 2 h at 70 °C under air atmosphere and normal pressure. After treatment, the mixture was filtered, washed with deionized water until the pH of the washing solution reached 7.0, and then washed twice with 70 vol% ethanol. The washed solid was dried in a forced-air dryer at 100 °C for 8 h to obtain the surface-oxidized carbon fiber precursor. In this embodiment, the mass loss rate of the surface-oxidized carbon fiber precursor relative to the untreated chopped carbon fibers was 2.5 wt%, the fiber length retention rate was 90%, and the fiber length D50 was 250 μm.

[0078] Preparation of Fe3O4 anchored surface-oxidized carbon fiber precursor: 100 parts by weight of surface-oxidized carbon fiber precursor were dispersed in 1000 parts by weight of deionized water and pre-dispersed at 25℃ for 30 min, followed by purging with nitrogen gas of ≥99.99% purity for 35 min. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added, with a Fe3+ to Fe2+ molar ratio of 2.0:1. The total amount of iron salts was determined according to the target loading of 4.0 wt% of the obtained Fe3O4 particles relative to the surface-oxidized carbon fiber precursor. The system was heated to 72℃, and ammonia solution with a mass fraction of 5 wt% (prepared by mixing 25 wt% ammonia solution with deionized water) was added dropwise. During the dropwise addition, the mixture was stirred at 400 r / min and the pH value was continuously monitored. The dropwise addition was stopped when the pH value reached 9.8, and the reaction was maintained at 72℃ for 2.5 h. After the reaction was completed, the mixture was filtered, washed with deionized water until the pH of the filtrate was 7.0, and then washed twice with 70 vol% ethanol. The filtrate was then dried at 75°C for 8 hours to obtain a precursor of iron oxide-anchored carbon fiber. The iron oxide particles in this precursor had a particle size of 45 nm, and the proportion of unanchored iron oxide particles to the total iron oxide particles was 5.0 wt%.

[0079] Preparation of PEEK-coated magnetic carbon fiber intermediate: 100 parts by weight of magnetite-anchored surface-oxidized carbon fiber precursor and 10.5 parts by weight of PEEK micro powder were mixed and premixed for 12 min under a dry nitrogen atmosphere, then placed in a high-temperature shear mixing device. The material was heated to 370°C at 9°C / min and melt-coated for 11 min under a nitrogen atmosphere and a shear rate of 70 r / min, forming a PEEK coating layer on the surface of the magnetite-anchored surface-oxidized carbon fiber precursor. After coating, the mixture was cooled to 150°C at 35°C / min under a nitrogen atmosphere, crushed, and sieved through a 90-mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. In this embodiment, the PEEK coating layer thickness was 160 nm, the PEEK coating coverage was 85%, and the proportion of free magnetite particles in the intermediate to the total mass of magnetite particles in the intermediate was 3.0 wt%.

[0080] Preparation of magnetic field-oriented composite preform: 79.0 parts by weight of matrix PEEK resin and 16.5 parts by weight of PEEK-coated magnetic carbon fiber intermediate were vacuum dried at 165°C for 5 hours to obtain dried material. The dried material was added to a high-temperature torque rheometer and melt-mixed at 375°C and 140 r / min for 4 minutes to obtain a melt composite. The melt composite was introduced into a preheated mold and oriented in a 0.9T magnetic field for 90 seconds, with the angle between the magnetic field direction and the target thermal conduction direction being 15°. Subsequently, it was pressed and shaped at 5 MPa. After pressing and shaping, it was cooled to 150°C at 80°C / min to obtain the magnetic field-oriented composite preform. In this embodiment, the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.78.

[0081] Supercritical carbon dioxide foaming and annealing: The magnetically oriented composite preform was placed in a high-pressure carbon dioxide foaming autoclave, and carbon dioxide was introduced. Saturation was carried out at a saturation pressure of 16 MPa and a saturation temperature of 80°C for 6 hours. After saturation, the pressure was released, and the mixture was transferred to an in-mold confined foaming stage, where it was foamed at 290°C for 600 seconds to obtain the foamed composite material. The foaming ratio in this embodiment was 1.8. The foamed composite material was then annealed at 210°C for 2 hours and cooled to 25°C to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. The composite material in this embodiment did not have an independent coating layer formed by silica, polydopamine, or a silane coupling agent.

[0082] Quality Inspection Methods and Results: Three samples of the annealed foamed composite material were inspected. The equivalent diameter of the cells was statistically analyzed using cross-sectional scanning electron microscopy (SEM) images. In this embodiment, the cell diameter D10 was 10 μm, D50 was 35 μm, and D90 was 100 μm, with a closed-cell rate of 75%. The orientation factor, calculated using the Herman orientation parameter formula, was 0.78 ± 0.02. Microscopic image analysis showed a PEEK coverage rate of 85.0 ± 1.5%. The proportion of free iron oxide particles in the composite material was 0.3 wt% of the total iron oxide particles. The density was 0.95 ± 0.02 g / cm³. 3 The thermal conductivity, measured along the target heat conduction direction according to ISO 22007-2:2022, is 1.65 ± 0.06 W·m. -1 ·K -1 The coefficient of friction, measured according to ASTM G99-23, was 0.20±0.01. The mating material was bearing steel, the normal load was 10N, the sliding speed was 0.10m / s, the sliding distance was 500m, and the ambient temperature was 25℃. The D50 retention rate of the chopped carbon fibers after melt-blending was 78%, and the PEEK coating coverage retention rate was 80%.

[0083] Features and application scenarios of this embodiment: This embodiment adopts an intermediate ratio and medium process strength. The matrix PEEK resin is a combination of powder and granules. Ammonia is added dropwise after dilution. Melt mixing is carried out in a high-temperature torque rheometer. It is suitable for medium-thickness heat-resistant composite boards that require relatively balanced thermal conductivity, wear resistance, foaming structure and processing adaptability.

[0084] Example 4

[0085] Overall preparation scale and product form: In this example, 1 part by weight (1.00 g) was used to prepare a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. In the final solid form, the matrix PEEK resin was 86.0 parts by weight, and the PEEK-coated magnetic carbon fiber intermediate was 12.0 parts by weight. The matrix PEEK resin was commercially available polyetheretherketone powder with a purity ≥99.5%, a particle size D50 of 20 μm, and a moisture content ≤0.05 wt%; the PEEK micropowder was commercially available polyetheretherketone micropowder with a purity ≥99.5%; the chopped carbon fibers were commercially available chopped carbon fibers with a fiber length D50 of 100 μm and a diameter of 6 μm; ferric chloride hexahydrate, ferrous chloride tetrahydrate, nitric acid, ammonia, and ethanol were all commercially available analytical grade or equivalent reagents, and the deionized water conductivity was ≤1 μS / cm.

[0086] Preparation of surface-oxidized carbon fiber precursor: 100 parts by weight of chopped carbon fibers and 700 parts by weight of a 40 wt% nitric acid aqueous solution were prepared. The chopped carbon fibers were first added to an acid-resistant reaction vessel, followed by the nitric acid aqueous solution. The mixture was mechanically stirred at 220 r / min for 1 h at 60 °C under air atmosphere and normal pressure. After treatment, the mixture was filtered, washed with deionized water until the pH of the washing solution reached 6.5, and then washed once with anhydrous ethanol. The washed solid was dried in a forced-air dryer at 90 °C for 6 h to obtain the surface-oxidized carbon fiber precursor. In this embodiment, the mass loss rate of the surface-oxidized carbon fiber precursor relative to the untreated chopped carbon fibers was 1.0 wt%, the fiber length retention rate was 85%, and the fiber length D50 was 100 μm.

[0087] Preparation of Fe3O4 anchored surface-oxidized carbon fiber precursor: 100 parts by weight of surface-oxidized carbon fiber precursor were dispersed in 600 parts by weight of deionized water and pre-dispersed at 25℃ for 25 min, followed by purging with nitrogen gas of ≥99.99% purity for 30 min. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added, with a Fe3+ to Fe2+ molar ratio of 1.9:1. The total amount of iron salts was determined according to the target loading of 2.0 wt% of the obtained Fe3O4 particles relative to the surface-oxidized carbon fiber precursor. The system was heated to 65℃, and a 10 wt% ammonia solution prepared by mixing 28 wt% ammonia solution with deionized water was added dropwise. During the dropwise addition, the mixture was stirred at 350 r / min and the pH value was continuously monitored. The dropwise addition was stopped when the pH value reached 9.2, and the reaction was maintained at 65℃ for 1.5 h. After the reaction was completed, the mixture was filtered, washed with deionized water until the pH of the filtrate was 6.5, then washed once with anhydrous ethanol, and dried at 65°C for 5 hours to obtain a precursor of iron oxide-anchored carbon fiber. The iron oxide particles in this precursor had a particle size of 20 nm, and the proportion of unanchored iron oxide particles to the total iron oxide particles was 6.0 wt%.

[0088] Preparation of PEEK-coated magnetic carbon fiber intermediate: 100 parts by weight of magnetite-anchored surface-oxidized carbon fiber precursor and 6 parts by weight of PEEK micropowder were mixed and premixed for 10 min under a dry nitrogen atmosphere, then placed in a high-temperature shear mixing device. The material was heated to 360°C at 10°C / min and melt-coated for 5 min under a nitrogen atmosphere and a shear rate of 40 r / min, forming a PEEK coating layer on the surface of the magnetite-anchored surface-oxidized carbon fiber precursor. After coating, the mixture was cooled to 130°C at 30°C / min under a nitrogen atmosphere, crushed, and sieved through a 100-mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. In this embodiment, the PEEK coating layer thickness was 60 nm, the PEEK coating coverage was 75%, and the proportion of free magnetite particles in the intermediate to the total mass of magnetite particles in the intermediate was 4.0 wt%.

[0089] Preparation of magnetic field-oriented composite preform: 86.0 parts by weight of matrix PEEK resin and 12.0 parts by weight of PEEK-coated magnetic carbon fiber intermediate were vacuum dried at 155°C for 3 hours to obtain dried material. The dried material was added to a twin-screw extruder and melt-blended at 365°C and 60 r / min for 2 minutes to obtain a melt composite. The melt composite was introduced into a preheated mold and oriented in a 0.5T magnetic field for 30 seconds, with the angle between the magnetic field direction and the target thermal conduction direction being 5°. Subsequently, it was pressed and shaped under 1.5 MPa. After pressing and shaping, it was cooled to 130°C at 40°C / min to obtain the magnetic field-oriented composite preform. In this embodiment, the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.65.

[0090] Supercritical carbon dioxide foaming and annealing: The magnetically oriented composite preform was placed in a high-pressure carbon dioxide foaming autoclave, and carbon dioxide was introduced. Saturation was carried out at a saturation pressure of 10 MPa and a saturation temperature of 50°C for 3 hours. After saturation, the pressure was released, and the mixture was transferred to an in-mold confined foaming stage, where it was foamed at 260°C for 150 seconds to obtain the foamed composite material. The foaming ratio in this embodiment was 1.3. The foamed composite material was then annealed at 190°C for 1 hour and cooled to 25°C to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material. The composite material in this embodiment did not have an independent coating layer formed by silica, polydopamine, or a silane coupling agent.

[0091] Quality Inspection Methods and Results: Three samples of the annealed foamed composite material were inspected. The equivalent diameter of the cells was statistically analyzed using cross-sectional scanning electron microscopy (SEM) images. In this embodiment, the cell diameter D10 was 4 μm, D50 was 12 μm, and D90 was 40 μm, with a closed-cell rate of 60%. The orientation factor, calculated using the Herman orientation parameter formula, was 0.65 ± 0.02. Microscopic image analysis showed a PEEK coverage rate of 75.0 ± 1.6%. The proportion of free iron oxide particles in the composite material was 0.4 wt% of the total iron oxide particles. The density was 1.15 ± 0.03 g / cm³. 3 The thermal conductivity, measured along the target heat conduction direction according to ISO 22007-2:2022, is 0.95 ± 0.04 W·m. -1 ·K -1 The coefficient of friction, measured according to ASTM G99-23, was 0.24±0.02. The mating material was bearing steel, the normal load was 10N, the sliding speed was 0.10m / s, the sliding distance was 500m, and the ambient temperature was 25℃. The D50 retention rate of the chopped carbon fibers after melt-blending was 70%, and the PEEK coating coverage retention rate was 70%.

[0092] Features and application scenarios of this embodiment: This embodiment adopts a combination of low load and mild magnetic field orientation, selects shorter chopped carbon fibers and thinner PEEK coating layers, and the foaming ratio is in the low value range. It is suitable for small precision heat-resistant sliding parts and wear-resistant thermal pads that require surface smoothness, high density, processing stability and moderate thermal conductivity and wear resistance.

[0093] Comparative Example 1: It is basically the same as Example 1, except that in the preparation step of magnetic field oriented composite preform, the amount of PEEK-coated magnetic carbon fiber intermediate is adjusted from 8.0 parts by weight to 5.0 parts by weight, the matrix PEEK resin is still 70.0 parts by weight, and other conditions remain unchanged.

[0094] Comparative Example 2: It is basically the same as Example 1, except that in the preparation step of PEEK-coated magnetic carbon fiber intermediate, the amount of PEEK micro powder corresponding to 100 parts by weight of iron oxide anchoring surface oxidized carbon fiber precursor is adjusted from 3 parts by weight to 1 part by weight, while other conditions remain unchanged.

[0095] Comparative Example 3: It is basically the same as Example 1, except that in the overall preparation scale and product form, the fiber length D50 of the short-cut carbon fiber is adjusted from 50μm to 30μm, while the diameter remains 5μm, and other conditions remain unchanged.

[0096] Comparative Example 4: It is basically the same as Example 1, except that in the preparation step of the surface-oxidized carbon fiber precursor, the mass fraction of nitric acid aqueous solution is adjusted from 30wt% to 20wt%, and the ratio of short carbon fiber to nitric acid aqueous solution is still 100 parts by weight and 500 parts by weight, and other conditions remain unchanged.

[0097] Comparative Example 5: It is basically the same as Example 1, except that in the preparation step of the iron oxide anchored surface oxidized carbon fiber precursor, 25 wt% ammonia water is added dropwise until the pH value of the system reaches 8.5 and then the addition is stopped. The reaction is kept at 60°C for 1 hour, and other conditions remain unchanged.

[0098] Comparative Example 6: It is basically the same as Example 1, except that in the magnetic field orientation composite preform preparation step, the melt mixing temperature is adjusted from 360℃ to 345℃, the twin-screw extruder speed is still 30r / min, the melt mixing time is still 1min, and other conditions remain unchanged.

[0099] Comparative Example 7: It is basically the same as Example 1, except that in the preparation step of the magnetic field orientation composite preform, the magnetic field strength is adjusted from 0.2T to 0.1T, the orientation time is still 10s, the angle between the magnetic field direction and the target heat conduction direction is still 0°, and other conditions remain unchanged.

[0100] Comparative Example 8: It is basically the same as Example 1, except that in the supercritical carbon dioxide foaming step, the saturation pressure is adjusted from 8 MPa to 6 MPa, the saturation temperature is still 35°C, the saturation time is still 2 hours, and other conditions remain unchanged.

[0101] Comparative Example 9: Essentially the same as Example 1, except that ferric chloride hexahydrate, ferrous chloride tetrahydrate, and ammonia were not added during the preparation of the iron oxide-anchored surface-oxidized carbon fiber precursor, and the in-situ nucleation and anchoring step of iron oxide was omitted. After washing and drying, the surface-oxidized carbon fiber precursor was directly melt-coated with 3 parts by weight of PEEK micropowder at a ratio of 100 parts by weight, and then added to the matrix PEEK resin at a ratio of 8.0 parts by weight, with other conditions remaining unchanged. This comparative example was used to verify the synergistic effect of iron oxide anchoring and PEEK coating layer interface construction.

[0102] Comparative Example 10: Essentially the same as Example 1, except that the PEEK micropowder preparation, melt coating, cooling crushing, and sieving processes in the PEEK-coated magnetic carbon fiber intermediate preparation steps were omitted. The iron oxide-anchored surface-oxidized carbon fiber precursor was dried at 60°C for 4 hours and directly used as the magnetic carbon fiber intermediate, added to the matrix PEEK resin at 8.0 parts by weight, with other conditions remaining unchanged. This comparative example was used to verify the synergistic effect of the iron oxide-anchored magnetic carbon fiber and the PEEK coating layer.

[0103] Comparative Example 11: This example is essentially the same as Example 1, except that the order of formation of the iron oxide anchoring and PEEK melt coating is changed. First, 100 parts by weight of the surface-oxidized carbon fiber precursor and 3 parts by weight of PEEK micropowder are melt-coated at 350°C and 20 r / min for 2 min, then cooled to 120°C. The resulting PEEK-coated surface-oxidized carbon fiber is then dispersed in 500 parts by weight of deionized water. Ferric chloride hexahydrate and ferrous chloride tetrahydrate are added at a Fe3+ to Fe2+ molar ratio of 1.8:1. The total amount of iron salts is determined according to a target loading of 0.5 wt%. Ammonia water with a mass fraction of 25 wt% is added dropwise at 60°C until the pH reaches 9.0, and the reaction is maintained at this temperature for 1 h. Subsequently, the mixture is washed, dried, crushed, and sieved, while other conditions remain unchanged. This comparative example is used to verify the synergistic effect of the order of iron oxide anchoring, PEEK coating, and interface construction.

[0104] Characterization and performance testing: The thermal conductivity of annealed magnetic carbon fiber-reinforced supercritical foamed thermally conductive and wear-resistant PEEK composites was tested along the target thermal conductivity direction to evaluate the contribution of the oriented carbon fiber network to heat transfer. The transient planar heat source method was used. The test surface of the sample was polished flat, and the thickness and density were recorded simultaneously. The angle between the test direction and the magnetic field direction was recorded as 0–30°. At least three samples were used in each group. Results are expressed as mean ± standard deviation, and the correlation with orientation factor and density was calculated. ISO 22007-2:2022 is applicable to the transient planar heat source determination of thermal conductivity and thermal diffusivity of plastics.

[0105] The annealed foamed composite material underwent friction coefficient and wear behavior tests to evaluate its wear resistance under the combined effect of the microporous structure and the directional reinforcement structure. A pin-disc or ball-disc friction and wear device was used, with bearing steel as the mating component. The normal load was 10 N, the sliding speed was 0.10 m / s, the sliding distance was 500 m, and the ambient temperature was 25 °C. Instantaneous friction coefficient, steady-state friction coefficient, and wear track quality changes were recorded, with at least three samples per group. ASTM G99-23 is the method for testing pin-disc or ball-disc wear and friction.

[0106] Cell structure testing was performed on the cross-section of the annealed foamed composite material to evaluate the integrity of the microporous structure after supercritical carbon dioxide foaming. SEM images of the cross-section were acquired after low-temperature brittle fracture and gold sputtering of the samples. Cell size distributions (D10, D50, and D90) were statistically analyzed based on the equivalent circle diameter. The closed-cell rate was determined using the gas volume method or the equivalent closed-cell method. At least five fields of view were used for each sample. Data were exported to CSV and percentiles were calculated. ISO 13322-1:2014 is suitable for static image particle size distribution analysis, and ISO 4590:2016 is used for determining the open and closed-cell volume fractions.

[0107] After annealing, the foamed composite material undergoes density and expansion ratio tests to evaluate the degree of in-mold confinement foaming and the level of lightweighting. Samples are cut into regular geometric shapes, their length, width, and thickness are measured, and their mass is weighed to calculate the apparent density. The expansion ratio is calculated as the ratio of the density of the unfoamed preform to the density after foaming. At least three samples are used in each group, and the mean, standard deviation, and dimensional deviation are recorded. ISO 845:2006 specifies the method for determining the apparent density of foamed plastics and rubber.

[0108] Orientation factor, fiber length retention rate, and PEEK coverage were tested on magnetically oriented composite preforms and annealed foamed composites to evaluate the structural retention of the intermediates after melt mixing, orientation, and foaming. The angle θ between the axis of chopped carbon fibers and the magnetic field direction in cross-sectional SEM images was statistically analyzed, and the orientation factor was calculated using the Herman orientation parameter formula. Simultaneously, fiber length D50 and the proportion of the covered area were statistically analyzed. Each group contained no fewer than 100 fibers, and the angle, length, and coverage (CSV) were output. The image statistical standards followed ISO 13322-1:2014.

[0109] High-temperature melt flow and apparent viscosity tests were performed on dried materials or molten composites to evaluate processing flowability and the processability window before filler orientation. Shear rates of 10–1000 s⁻¹ were measured using capillary or slit rheometers at 360°C, 375°C, and 390°C. -1 The apparent viscosity is measured within the specified range, and the extrusion pressure, shear stress, and shear viscosity are recorded. At least three parallel tests are performed for each group, and the mean viscosity and coefficient of variation are calculated. ISO 11443:2021 specifies the method for determining the flowability of plastic melts in capillary and slit rheometers.

[0110] The loading of magnetite (Fe3O4) particles, the proportion of free Fe3O4 particles, and the residual inorganic content in PEEK-coated magnetic carbon fiber intermediates and annealed foamed composites were tested to evaluate the magnetic anchoring and interfacial fixation. After dispersion, magnetic separation, and drying, the free particles were weighed, and separate samples were taken for thermogravimetric analysis to calculate the residual inorganic content and loading. At least three samples were taken per group, and the initial mass, the mass of separated particles, the residual mass, and the calculated proportion were recorded. The proportion of free Fe3O4 particles in the annealed foamed composite was calculated as the ratio of the mass of separated particles to the total mass of Fe3O4 particles in the same batch of composite material. ISO 11358-1:2022 specifies the general principles of polymer thermogravimetric analysis.

[0111] Figure 1 The fiber orientation angular distribution density diagrams are for Example 1, Comparative Example 9, and Comparative Example 10. Figure 2 Box plots of Herman orientation factors for Examples 1, 9, and 10 are shown. Figure 1 and Figure 2 It can be seen that the fiber orientation angles in Example 1 are mainly concentrated in the lower angle range, with a narrower orientation angle distribution, and the Herman orientation factor remains at a high level, indicating that the chopped carbon fibers can form a relatively stable orientation arrangement along the preset direction. In contrast, Comparative Example 9, due to the lack of a magnetite anchoring structure, has insufficient fiber response to the applied magnetic field, resulting in a significantly wider orientation angle distribution and a significantly lower Herman orientation factor. Although Comparative Example 10 still contains magnetic components and exhibits a certain orientation trend, the lack of a PEEK coating layer to fix the magnetic particles and fiber interface increases the dispersion of the orientation distribution, and the orientation factor is lower than that of Example 1 with more obvious fluctuations. The above results show that magnetite anchoring can endow carbon fibers with effective magnetic response capabilities, while the PEEK coating layer can further stabilize the magnetic particles and fiber interface. The synergistic effect of the two is conducive to forming a stable and repeatable magnetic field-induced orientation structure.

[0112] Figure 3 Box plots of PEEK coverage for Examples 1, 9, and 10. Figure 4 The XPS Fe 2p spectra of Example 1, Comparative Example 9, and Comparative Example 10 are shown below. Figure 5 This is a scatter plot of the EDS elemental atomic percentages for Example 1, Comparative Example 9, and Comparative Example 10. Figure 3 It can be seen that Example 1 and Comparative Example 9 both have high PEEK coating coverage, while Comparative Example 10 is close to no coating, indicating that the homogeneous PEEK coating layer can form a relatively continuous interfacial transition layer on the carbon fiber surface. Further combining... Figure 4 and Figure 5It can be seen that Example 1 shows a clear response in the Fe 2p characteristic binding energy range, and a suitable amount of Fe element was detected in the EDS test, with a relatively stable distribution of C, O, and Fe elements. The Fe signal of Comparative Example 9 is close to the background level, indicating that it lacks effective magnetic components. Although the Fe signal of Comparative Example 10 is stronger, the Fe element content fluctuates greatly, indicating that the iron oxide particles not effectively constrained by the PEEK coating layer are more prone to local enrichment or uneven distribution. This shows that simply introducing magnetic particles cannot guarantee a uniform and stable interface structure. The combination of the PEEK coating layer and the iron oxide anchoring structure can improve the uniformity of magnetic component fixation on the carbon fiber surface, providing a stable foundation for subsequent magnetic field orientation, melt composite, and foaming molding.

[0113] Figure 6 The TGA mass retention rate-temperature curves are for Example 1, Comparative Example 9, and Comparative Example 10. Figure 7 This is a scatter plot of free iron oxide particles from Example 1, Comparative Example 9, and Comparative Example 10, presented in a proportionate box plot. Figure 6 It can be seen that Example 1 has a suitable amount of inorganic residue in the high-temperature range, Comparative Example 9 has the lowest residue, and Comparative Example 10 has a relatively high residue, indicating that the introduction of iron(III) oxide can increase the inorganic residue content of the composite system. Further... Figure 7 It can be seen that the proportion of free iron oxide particles in Example 1 is relatively low, Comparative Example 9 has almost no magnetic particles, while the proportion of free particles in Comparative Example 10 is significantly increased. This result indicates that although Comparative Example 10 contains a relatively large number of magnetic particles, due to the lack of a PEEK coating interface, the magnetic particles are prone to detachment, migration, or aggregation, resulting in a high level of inorganic residue and insufficient stability. Example 1, by using a PEEK coating layer to provide interfacial constraint for the iron oxide particles, retains the necessary magnetic response components while reducing the proportion of free particles, thereby improving the structural stability of the magnetic carbon fiber intermediate.

[0114] Figure 8 The diagram shows the equivalent diameter distribution density of bubbles in Examples 1, 8, and 10. Figure 9 This is a cumulative distribution diagram of the equivalent cell diameter for Example 1, Comparative Example 8, and Comparative Example 10. Figure 10 The graphs show the D10 / D50 / D90 quantiles for Example 1, Comparative Example 8, and Comparative Example 10. Figure 11 This is a box plot of the closed-pore ratio for Example 1, Comparative Example 8, and Comparative Example 10. (Source: [Insert Source Here]) Figures 8 to 10It can be seen that the cell size distribution in Example 1 is concentrated, with D50 approximately 5 μm and D90 approximately 20 μm, and the cell size is within a moderate range. In Comparative Example 8, due to the deviation of the carbon dioxide saturation pressure, the overall cell size shifts towards smaller sizes, which easily leads to insufficient gas diffusion and cell growth. In Comparative Example 10, due to the lack of a PEEK coating layer, the interface stability is reduced, the cell size distribution becomes wider, and there is a trend towards larger cells. Further... Figure 11 It can be seen that the closed-cell rate of Example 1 is approximately 50%, and the data repeatability is good, while the closed-cell rates of Comparative Examples 8 and 10 both show a decrease. These results indicate that reasonable supercritical carbon dioxide foaming conditions can regulate the cell nucleation and growth process, and the PEEK-coated magnetically oriented carbon fiber interface can reduce the risk of cell merging and collapse, enabling the material to obtain a microporous structure with moderate size, uniform distribution, and a high proportion of closed cells under mild foaming conditions.

[0115] Figure 12 The following are two-dimensional correlation diagrams of thermal conductivity versus orientation factor for Examples 1, 8, and 11. Figure 13 The graphs show the two-dimensional correlation between the friction coefficient and the closed-pore ratio for Examples 1, 8, and 11. Figure 14 This is a trend chart of normalized cell D50 performance for Examples 1, 8, and 11. Figure 12 It can be seen that Example 1 exhibits both a high Herman orientation factor and a high thermal conductivity, indicating that oriented short-cut carbon fibers can construct thermally conductive pathways within the PEEK matrix. In Comparative Example 11, the orientation factor decreases and thermal conductivity declines simultaneously due to the disruption of the synergistic sequence between magnetic field orientation and the foaming process, demonstrating that orientation structure is a crucial factor in improving thermal conductivity. Figure 13 It can be seen that Example 1 exhibits a lower coefficient of friction under a higher closed-cell ratio, while Comparative Examples 8 and 11 show a decrease in closed-cell ratio accompanied by an increase in the coefficient of friction, indicating that a stable closed-cell structure can improve the surface bearing capacity during friction and reduce local damage and wear. Further... Figure 14 It can be seen that Example 1 maintains high levels of normalized thermal conductivity and wear resistance at a moderate cell size of approximately 5 μm (D50). Comparative Example 8, with its excessively fine cells, and Comparative Example 11, with insufficient structural synergy, both fail to achieve good thermal conductivity and wear resistance simultaneously. This demonstrates that there is a synergistic relationship between fiber orientation, closed-cell structure, and cell size; only when the orientation interface is stable and the cell size is moderate can the overall performance of the material be effectively improved.

[0116] Figure 15 The high-temperature rheological viscosity-shear rate curves are for Example 1, Comparative Example 1, and Comparative Example 6. Figure 16 The figures show the extrusion pressure-shear rate curves for Example 1, Comparative Example 1, and Comparative Example 6. Figure 15It can be seen that Example 1 exhibits moderate shear thinning behavior at 360°C, indicating that the melt possesses both necessary fluidity and the ability to maintain a certain structural support capacity during processing; Comparative Example 1 has a lower viscosity, which may lead to insufficient retention of filler orientation and cell structure; Comparative Example 6 has a higher viscosity, which will increase flow resistance during melt mixing and extrusion. Combined with... Figure 16 It can be seen that the extrusion pressure of Example 1 increases steadily with the increase of shear rate, and the pressure change is relatively controllable; the pressure of Comparative Example 1 is too low, and the pressure of Comparative Example 6 is too high, both of which are not conducive to stable molding. The above results indicate that the amount of intermediate and the melt mixing temperature need to be controlled within a reasonable range to achieve a balance between the fluidity, structure retention and processing stability of the composite melt.

[0117] Figure 17 Box plots of fiber length retention rates for Example 1, Comparative Example 1, and Comparative Example 6. Figure 18 Box plots of PEEK coating coverage retention rates for Example 1, Comparative Example 1, and Comparative Example 6. Figure 17 It can be seen that the fiber length retention rate in Example 1 is approximately 60%, indicating that the short-cut carbon fibers did not undergo excessive shearing damage during the melt mixing process and could still retain effective reinforcing length. In Comparative Example 6, due to deviations in mixing temperature or processing conditions, the fiber length retention rate decreased, indicating that excessive shearing or unsuitable melt conditions weaken the fiber-reinforced skeleton. Figure 18 It can be seen that the PEEK coating coverage retention rate of Example 1 is approximately 60%, which is significantly better than that of Comparative Example 6. This indicates that a suitable processing window can maintain the integrity of the homogeneous PEEK coating interface and reduce coating peeling and magnetic particle migration. Figure 15 and Figure 16 The rheological and extrusion results show that Example 1 not only has good processing stability, but also retains fiber length and interfacial coating structure after processing, thus providing structural protection for the thermal conductivity, closed-cell foaming and wear resistance of the final material.

[0118] Figure 19 This is a macroscopic optical photograph of the magnetic carbon fiber-reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1. Figure 19 As can be seen, the sample of Example 1 has a black to dark gray opaque sheet or block appearance, with an intact overall morphology and no obvious macroscopic cracks, collapses, or warping on the surface. This dark appearance is mainly related to the light absorption effect of the short-cut carbon fibers and Fe3O4 magnetic nanoparticles. After slight foaming, the material density of Example 1 is 1.25 ± 0.03 g / cm³. 3The foaming ratio of 1.1 indicates that the material maintains high structural density and dimensional stability while introducing a microporous structure. This result demonstrates good process compatibility between magnetic carbon fiber directional reinforcement, PEEK interface coating, and supercritical carbon dioxide mild foaming in terms of macroscopic molding quality.

[0119] Figure 20 This is a SEM image of the magnetic carbon fiber-reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1. Figure 20 The low-magnification cross-sectional morphology of image a shows that micron-sized pores and short-cut carbon fibers are distributed in the PEEK continuous matrix. The equivalent diameters of the pores, D10, D50, and D90, are approximately 2 μm, 5 μm, and 20 μm, respectively, with a closed-cell rate of approximately 50%. This indicates that the supercritical carbon dioxide foaming process can form a controlled microporous structure, and the pores do not undergo large-scale interconnection or collapse. Figure 20 b and Figure 20 The cross-sectional morphology of the medium magnification section (c) shows that the short-cut carbon fibers are oriented along the target thermal conductivity direction, with an orientation factor of 0.60 ± 0.02, indicating that the magnetic field orientation process can effectively induce the magnetic carbon fibers to form a directionally reinforced skeleton. Figure 20 The high-magnification interface morphology of sample d shows that the carbon fibers and the PEEK matrix are tightly bonded, with localized PEEK coating layers and Fe3O4 nanoparticle anchoring regions. The PEEK coating layer is approximately 20 nm thick, and the Fe3O4 particles are approximately 10 nm in diameter. These SEM results at different scales corroborate each other, indicating that Example 1 achieved a stable structure in terms of microporous structure, fiber orientation, and interfacial bonding.

[0120] Figure 21 This is a TEM image of the magnetic carbon fiber-reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material obtained in Example 1. Figure 21 As can be seen from point a, the high-contrast Fe3O4 nanoparticles are anchored near the surface-oxidized carbon fibers, indicating that the surface oxidation treatment can provide a fixed position for the magnetic particles, which is beneficial to the formation of the magnetic response structure. Figure 21 As shown in b, the approximately 20 nm thick PEEK coating layer is located on the carbon fiber surface and forms an interfacial transition region, indicating that the PEEK-coated magnetic carbon fiber intermediate can construct a continuous or locally continuous homogeneous interface in the composite material. Figure 21 HRTEM images of c show that the Fe3O4 nanoparticles have clear lattice fringes, with a typical interplanar spacing of approximately 0.253 nm, corresponding to the 311 crystal plane of cubic Fe3O4. In the carbon fiber region, a graphitized carbon 002 interlayer spacing of approximately 0.34 nm can be observed, indicating that the magnetic particles possess a good nanocrystalline structure, and the carbon fibers retain a layered carbon structure beneficial for thermal conductivity. In summary... Figures 19 to 21It can be seen that Example 1 exhibits consistency from macroscopic molding, micron-level pores and orientation structure to nanoscale magnetic anchoring and interface coating, further demonstrating that the material's structural design and preparation process can effectively achieve a synergistic improvement in thermal conductivity, wear resistance, and lightweight performance.

[0121]

[0122] As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1–4 exhibit a continuous and reasonable performance distribution with changes in the content of PEEK-coated magnetic carbon fiber intermediates, the degree of magnetic field orientation, the PEEK coating coverage, and the integrity of the foamed structure. The thermal conductivity increases with the orientation factor and the effective network reinforcement of the carbon fiber, while the friction coefficient decreases with interface coating, fiber load-bearing capacity, and the maintenance of the closed-cell structure. Comparative Examples 1–8, by changing the filler dosage, the PEEK micro-powder used for coating, the fiber length, oxidation conditions, anchoring pH, mixing temperature, magnetic field strength, and saturation pressure, all resulted in deviations from at least one core structural parameter. In Comparative Examples 9–11, after disassembling the iron oxide anchoring, the PEEK coating layer, and the formation sequence, the correlation between the orientation factor, coating coverage, closed-cell ratio, and friction coefficient was weakened, indicating that the structural construction process has a combined impact on thermal conductivity, wear resistance, and micropore retention.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material, characterized in that, Based on the final solid form composition of the composite material, it includes the following components in parts by weight: The matrix is ​​made of PEEK resin, 70.0–88.0 parts by weight; PEEK-coated magnetic carbon fiber intermediate, 8.0–25.0 parts by weight; Wherein, PEEK is polyetheretherketone, and the matrix is ​​formed by PEEK resin in the composite material to form a continuous matrix phase; The PEEK-coated magnetic carbon fiber intermediate includes chopped carbon fibers, iron oxide particles anchored to the surface of the chopped carbon fibers, and a PEEK coating layer covering the surface of the chopped carbon fibers and at least a portion of the surface of the iron oxide particles. The chopped carbon fibers anchored to the iron oxide particles constitute magnetic carbon fibers.

2. The composite material according to claim 1, characterized in that, The composite material has a microporous structure formed by supercritical carbon dioxide foaming, and the pore D50 of the microporous structure is 5–80 μm. The PEEK-coated magnetic carbon fiber intermediate has a magnetic field-induced orientation structure in the continuous matrix phase, with an orientation factor of 0.60–0.

95. The thickness of the PEEK coating layer is 20–300 nm, and the PEEK coating layer has the same chemical composition as the PEEK resin used in the matrix.

3. The composite material according to claim 1, characterized in that, The PEEK-coated magnetic carbon fiber intermediate is prepared by the following steps: A1. Provides precursors for iron oxide-anchored surface-oxidized carbon fiber; A2. Mix 100 parts by weight of the iron oxide anchored surface oxidized carbon fiber precursor with 3–18 parts by weight of PEEK micro powder. A3. Under a nitrogen atmosphere, heat the material obtained in step A2 to 350–390°C and melt-coat it for 2–20 min under shear conditions of 20–120 r / min, so that PEEK forms a PEEK coating layer on the surface of the carbon fiber precursor anchored on the iron oxide surface. A4. After cooling to 120–180°C under a nitrogen atmosphere, the material is crushed and sieved through an 80–100 mesh sieve to obtain the PEEK-coated magnetic carbon fiber intermediate. A5. The quality control parameters of the PEEK-coated magnetic carbon fiber intermediate are: the PEEK coating coverage rate is 70-98%, and the proportion of free iron oxide particles in the intermediate to the total mass of iron oxide particles in the intermediate is not higher than 5.0 wt%.

4. The composite material according to claim 3, characterized in that, The iron oxide anchored surface-oxidized carbon fiber precursor in step A1 is prepared through the following steps: B1. Provides surface-oxidized carbon fiber precursors; B2. Disperse 100 parts by weight of the surface-oxidized carbon fiber precursor in 500–1500 parts by weight of deionized water and purge with nitrogen gas; B3. Add ferric chloride hexahydrate and ferrous chloride tetrahydrate, wherein Fe 3+ with Fe 2+ The molar ratio is 1.8–2.2:1, and the total amount of iron salt is determined according to the target loading of the obtained iron oxide particles relative to the surface-oxidized carbon fiber precursor being 0.5–8.0 wt%. B4. At 60–85℃, adjust the pH of the system to 9.0–10.5 with ammonia water and keep it at the temperature for 1–4 hours to allow the iron oxide particles to nucleate and anchor in situ on the surface of the carbon fiber precursor. B5. Wash with deionized water until the pH of the filtrate is 6.0–8.0, then wash with ethanol 1–3 times; B6. Dry at 60–90℃ for 4–12 h to obtain the iron oxide anchored surface oxidized carbon fiber precursor; B7. The quality control parameters of the iron oxide anchored surface oxidized carbon fiber precursor are as follows: the loading of iron oxide particles relative to the surface oxidized carbon fiber precursor is 0.5–8.0 wt%, the particle size of iron oxide particles is 10–80 nm, and the proportion of unanchored iron oxide particles to the total amount of iron oxide particles is not higher than 8.0 wt%.

5. The composite material according to claim 4, characterized in that, The surface-oxidized carbon fiber precursor in step B1 is prepared through the following steps: C1. A mixture of 100 parts by weight of chopped carbon fibers and 500–2000 parts by weight of an aqueous nitric acid solution, wherein the aqueous nitric acid solution has a mass fraction of 30–70 wt%. C2. Surface oxidation of the chopped carbon fibers is carried out at 50–90°C for 0.5–4 hours; C3. Wash with deionized water until the pH of the washing solution is 6.0–8.0, then wash with ethanol 1–3 times; C4. Dry at 80–120℃ for 4–12 h to obtain the surface-oxidized carbon fiber precursor; C5. The quality control parameters of the surface-oxidized carbon fiber precursor are: a mass loss rate of 0.1–5.0 wt% relative to the chopped carbon fiber before treatment, a fiber length retention rate of 80–99%, and a fiber length D50 of 50–500 μm for the surface-oxidized carbon fiber precursor.

6. The composite material according to claim 1, characterized in that, Before supercritical carbon dioxide foaming, the composite material is first formed into a magnetically oriented composite preform, which is prepared through the following steps: D1. 70.0–88.0 parts by weight of the matrix are dried with PEEK resin and 8.0–25.0 parts by weight of PEEK-coated magnetic carbon fiber intermediate; D2. Melt-mix at 360–390℃ for 1–8 min to obtain a melt composite; D3. The molten composite was placed in a magnetic field of 0.2–1.5T for 10–180s for orientation and then pressed and shaped under 0.5–10MPa. D4. Cool to 120–180℃ at a cooling rate of 20–150℃ / min to obtain a magnetic field oriented composite preform; D5. The orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.60–0.

95.

7. The composite material according to claim 1, characterized in that, In the PEEK-coated magnetic carbon fiber intermediate, the length D50 of the chopped carbon fiber is 50–500 μm, the diameter of the chopped carbon fiber is 5–10 μm, the particle size of the iron oxide (Fe3O4) particles is 10–80 nm, and the loading of the iron oxide particles relative to the chopped carbon fiber is 0.5–8.0 wt%. The microporous structure has a pore size of D10 of 2–20 μm, a pore size of D90 of 20–180 μm, and a pore size of D10 ≤ pore size of D50 ≤ pore size of D90, with a closed-cell rate of 50–95%. The PEEK coating layer has a PEEK coverage rate of 70–98% on the surface of the chopped carbon fibers; The proportion of free iron oxide particles in the composite material is no more than 0.5 wt% of the total mass of iron oxide particles in the composite material, and the composite material does not have an independent coating layer formed by silica, polydopamine or silane coupling agent; The thermal conductivity of the composite material is 0.60–3.00 W·m. -1 ·K -1 The thermal conductivity is determined according to ISO 22007-2; the coefficient of friction of the composite material is 0.10–0.30, and the coefficient of friction is determined according to ASTM G 99.

8. A method for preparing a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Provide a pre-prepared PEEK-coated magnetic carbon fiber intermediate; S2. 70.0–88.0 parts by weight of the matrix are dried at 150–180°C for 2–8 hours with PEEK resin and 8.0–25.0 parts by weight of the PEEK-coated magnetic carbon fiber intermediate to obtain the dried material. S3. The dried material is melt-blended at 360–390°C for 1–8 min to obtain a melt composite. S4. The molten composite is placed in a magnetic field of 0.2–1.5T for 10–180s and then pressed and shaped under 0.5–10MPa. After pressing and shaping, it is cooled to 120–180℃ at a cooling rate of 20–150℃ / min to form a magnetically oriented composite preform. S5. The magnetic field-oriented composite preform is placed in carbon dioxide for saturation at a saturation pressure of 8–25 MPa, a saturation temperature of 35–120 °C, and a saturation time of 2–12 h. S6. After depressurization, the saturated magnetic field-oriented composite preform is foamed at a temperature of 240–340℃ for 5–1200s to obtain a foamed composite material. S7. Anneal the foamed composite material at 180–240℃ for 0.5–4h to obtain a magnetic carbon fiber oriented reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material.

9. The preparation method according to claim 8, characterized in that, In step S4, the angle between the magnetic field direction and the target thermal conduction direction is 0–30°, and the orientation factor of the PEEK-coated magnetic carbon fiber intermediate in the magnetic field-oriented composite preform is 0.60–0.

95.

10. The preparation method according to claim 8, characterized in that, In step S6, the foaming ratio is controlled to 1.1–2.5 by limiting foaming within the mold; The resulting magnetic carbon fiber-reinforced PEEK supercritical foamed thermally conductive and wear-resistant composite material has a cell D50 of 5–80 μm, a closed-cell rate of 50–95%, and a density of 0.70–1.25 g / cm³. 3 .

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