FeCoNiCr / pdms composite flexible coating, preparation method and application thereof

Abstract

This invention discloses a FeCoNiCr / PDMS composite flexible coating, its preparation method, and its applications, belonging to the field of electromagnetic wave compatibility materials technology. The preparation method includes: first, using Fe, Co, Ni, and Cr elemental powders in an equimolar ratio as raw materials, preparing FeCoNiCr high-entropy alloy powder through a ball milling process; then, mixing the obtained powder with polydimethylsiloxane (PDMS) at a certain mass ratio, followed by stirring, casting, and curing to obtain the composite coating. The advantages of this invention are: by combining the FeCoNiCr high-entropy alloy with a flexible PDMS substrate, a coating material with both flexible and self-supporting properties is successfully obtained. This material exhibits excellent electromagnetic shielding performance in the terahertz band and can be widely used in electromagnetic compatibility and protection in the field of terahertz technology.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic functional composite materials technology, and specifically provides a flexible FeCoNiCr high-entropy alloy / PDMS composite terahertz shielding coating, its preparation method, and its application. Background Technology

[0002] With the rapid development of 6G communication, bio-imaging, and other fields, terahertz technology is being applied more and more widely. However, the resulting electromagnetic interference, information leakage, and health risks urgently need to be addressed. Traditional metallic shielding materials, while possessing good conductivity, rely primarily on reflection mechanisms, making them prone to secondary pollution, and also suffer from limitations such as high density and poor flexibility. Current technologies face challenges related to material stability, flexibility, and the cost of large-scale fabrication in complex environments. Future research will focus on achieving terahertz shielding materials that are primarily shielding, lightweight, flexible, and multifunctionally integrated to support the application needs of next-generation electronic devices in extreme environments and smart wearable scenarios.

[0003] High-entropy alloys are a novel type of metallic material that revolutionizes traditional alloy design concepts. The core of high-entropy alloys lies in the high-entropy effect brought about by multi-principal element mixing; that is, the extremely high mixing entropy can overcome the tendency for phase separation between elements, promoting the formation of simple, stable solid solution structures (such as face-centered cubic (FCC) or body-centered cubic (BCC)) rather than complex intermetallic compounds. Through lattice distortion, hysteresis diffusion, and the "cocktail" effect, high-entropy alloys exhibit superior properties such as high strength, high hardness, excellent corrosion resistance, and resistance to high-temperature softening. In terms of preparation methods, in addition to traditional casting technologies such as vacuum arc melting and vacuum induction melting, scientists have also developed advanced processes such as mechanical alloying combined with spark plasma sintering, laser cladding, and magnetron sputtering to meet the needs of different forms and application scenarios. High-entropy alloys, with their four unique effects, have excellent application prospects in the field of terahertz wave shielding. The high-entropy effect endows the material with excellent structural stability, ensuring its reliable service in complex environments. The lattice distortion effect, by introducing atomic-scale stress and defects, greatly enhances electron scattering loss. The hysteresis diffusion effect facilitates the formation of nanostructures and amorphous phases, creating numerous heterogeneous interfaces and significantly enhancing the material's absorption capacity for terahertz waves. The "cocktail" effect provides excellent electromagnetic performance designability, allowing for synergistic optimization of conductive and dielectric loss mechanisms through flexible element mixing. Polydimethylsiloxane (PDMS) is a widely used silicon-based organic polymer material composed of an inorganic silicon-oxygen backbone (-Si-O-Si-) and organic methyl side groups. This unique structure gives it both the stability of inorganic materials and the flexibility of organic materials. PDMS is a transparent emulsion or elastomer under normal conditions, possessing optical transparency, chemical inertness, strong hydrophobicity, good thermal stability, excellent biocompatibility, and high flexibility. Currently, there are no reports on an effective approach to preparing flexible terahertz shielding coatings by combining high-entropy alloys and PDMS.

[0004] Patent CN116855888B discloses a flexible high-entropy alloy coating, its preparation method, and its applications. This invention prepares a high-entropy alloy coating using magnetically filtered cathode vacuum arc deposition technology. By changing the vacuum chamber layout and potential distribution to increase plasma density, the elemental composition and content can be adjusted. The prepared coating possesses excellent tribological, corrosive, and antioxidant properties, and the film is dense and smooth with good adhesion to the substrate. The film thickness can be controlled at the nanometer scale, avoiding the problems of high internal stress and difficulty in achieving flexibility in traditional high-entropy coatings. However, this patent mainly focuses on the mechanical and chemical protective properties of the coating and does not address electromagnetic wave absorption functions, especially its application in the terahertz band.

[0005] Patent CN119391296B discloses a highly flexible microwave absorbing coating based on a spherical / sheet composite, its preparation method, and its application. This coating comprises spherical absorbers, sheet-like absorbers, a rubber toughening agent, and a resin matrix. Through a "seesaw" structure design of the spherical / sheet absorbers, it reduces interparticle frictional resistance while ensuring reflection loss performance, thereby increasing the coating's Poisson's ratio and enhancing flexibility. However, the absorber system in this patent uses conventional spherical / sheet composite fillers (such as ferrites and carbon materials), does not use high-entropy alloys as functional phases, and does not explicitly design for or apply to the terahertz band.

[0006] Patent CN113185829B discloses a broadband terahertz absorbing material and its preparation method. This material uses rubber as a substrate and a nanoscale carbon-based absorber as the functional phase. It is molded using a die and has a rough surface, achieving broadband absorption in the 0.1–4 THz frequency band. However, the absorber in this patent is a carbon-based material, and the material system is completely different from high-entropy alloys. Furthermore, its molding method is compression molding, the material itself lacks inherent properties, and its flexibility depends on the selected rubber matrix; it is not specifically designed for flexible coating structures. Summary of the Invention

[0007] This invention relates to a flexible FeCoNiCr high-entropy alloy / PDMS composite coating, its preparation method, and its application in the field of terahertz shielding.

[0008] With the rapid development of terahertz technology in communications, imaging, and security inspection, the development of coating materials that combine high-efficiency electromagnetic shielding with flexibility and thinness has become an urgent need. In existing technologies, single materials or conventional composite materials often struggle to achieve both excellent terahertz wave attenuation capabilities and good flexibility. High-entropy alloys, due to their unique "cocktail" effect—the synergistic effect of multiple elements within a high-entropy alloy that allows the overall material performance to surpass the linear summation of the individual element performances, achieving a "1+1>2" effect—show promise in the field of electromagnetic functional materials. However, how to effectively combine them with flexible substrates and achieve performance tuning for the terahertz band still requires further exploration.

[0009] The purpose of this invention is to provide a flexible FeCoNiCr high-entropy alloy / PDMS composite coating and its preparation method. This method is simple, highly controllable, and can produce composite materials with stable structure, tunable dielectric properties, and no complex post-processing required. The resulting composite coating exhibits excellent electromagnetic shielding performance in the terahertz band.

[0010] The present invention also provides a method for preparing the above-mentioned composite coating, comprising the following steps: S1. Preparation of high-entropy alloy powder: Fe, Co, Ni and Cr elemental powders were weighed in equimolar ratio, anhydrous ethanol was used as the process control agent, and the powders were synthesized by mechanical ball milling. After drying, FeCoNiCr high-entropy alloy powder was obtained. S2. Preparation of composite coating: The high-entropy alloy powder obtained in step S1 is uniformly mixed with PDMS at a predetermined mass ratio, stirred, poured into a mold, and cured to obtain the composite coating. By systematically adjusting parameters such as ball milling time (to control the morphology and structure of the powder) and powder doping ratio, the electromagnetic shielding performance of the composite coating in the terahertz band can be effectively controlled.

[0011] The beneficial effects of this invention are as follows: Simple, green and efficient process: High-entropy alloy powder is prepared by mechanical ball milling and combined with PDMS solution composite process. The equipment requirements are low, the process is simple, safe and reliable, and it is suitable for large-scale preparation.

[0012] Unique structure and excellent performance: The prepared FeCoNiCr powder has a lamellar structure and exhibits dual-phase characteristics of BCC and FCC. This lamellar structure in the PDMS matrix facilitates multiple reflections and scattering of terahertz waves. Combined with the resistive loss and dielectric relaxation loss of the high-entropy alloy itself, the composite material behaves as an absorption-dominant electromagnetic shielding material in the 170~750 GHz frequency band, with a total electromagnetic shielding effectiveness (SET) of up to 92.8 dB.

[0013] Highly adaptable and with broad application prospects: The resulting composite coating exhibits good environmental stability, requires no complex post-processing, and possesses flexibility. It can be widely used in flexible electronics, local anti-interference of 6G communication equipment, electromagnetic protection of wearable devices, and stealth coatings for special curved surfaces. Attached Figure Description

[0014] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0015] Figure 1 XRD patterns and magnetization curves of FeCoNiCr in Example 1; Figure 2 Scanning electron microscope image of FeCoNiCr in Example 1; Figure 3 In Example 1, the FeCoNiCr / PDMS composite coating exhibited SE performance in the 50~750 GHz frequency band. T Atlas; Figure 4 XRD patterns and magnetization curves of FeCoNiCr in Comparative Example 1 Figure 5 XRD patterns and magnetization curves of FeCoNiCr in Comparative Example 2 Figure 6 In Comparative Example 1, the FeCoNiCr / PDMS composite coating exhibited SE performance in the 50–750 GHz frequency band. T Atlas; Figure 7 In Comparative Example 2, the FeCoNiCr / PDMS composite coating exhibited SE performance in the 50–750 GHz frequency band. T Atlas; Figure 8 Comparative Example 3: Pure PDMS coating under SE conditions in the 50–750 GHz frequency band T Atlas. Detailed Implementation

[0016] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0017] Example 1 This embodiment provides a method for preparing a flexible FeCoNiCr high-entropy alloy / PDMS composite coating, the steps of which are as follows: Preparation of FeCoNiCr high-entropy alloy powder: Equimolar amounts of Fe, Co, Ni, and Cr powders, totaling 10 g, were placed in a ball mill jar. Grinding balls with diameters of 10 mm and 6 mm were added to the jar at a ball-to-powder ratio of 20:1, with a mass ratio of 10 mm to 6 mm balls of 2:1. 40 mL of anhydrous ethanol was then added as a process control agent. The jar was sealed and placed on a planetary ball mill. The milling speed was set to 400 rpm, using a 30-minute run followed by a 4-minute rest cycle, for a total milling time of 70 hours. After milling, the resulting slurry was dried in a vacuum drying oven at 60℃ for 24 hours. The FeCoNiCr high-entropy alloy powder was then obtained after grinding.

[0018] 2. Preparation of the composite coating: PDMS main agent and curing agent were mixed at a mass ratio of 10:1 and stirred to prepare a uniform PDMS prepolymer. Then, the high-entropy alloy powder obtained in step 1 was weighed and added at a ratio of 30 wt% (30% of the total mass of the PDMS prepolymer and powder), and stirred thoroughly until uniformly mixed. The mixture was poured into a circular mold with an inner diameter of 75 mm and a depth of 1 mm, and cured in a 60℃ drying oven for 6 hours. After demolding, a FeCoNiCr / PDMS composite coating with a thickness of approximately 1 mm was obtained.

[0019] Figure 1 a is the XRD pattern of FeCoNiCr prepared in this embodiment. From Figure 1 As shown in Figure a, FeCoNiCr was successfully synthesized.

[0020] Figure 1 b is the magnetization curve of FeCoNiCr prepared in this embodiment. From Figure 1 As can be seen in b, FeCoNiCr is ferromagnetic, with a coercivity of 77.6 Oe and a saturation magnetization of 98.6 emu / g.

[0021] Figure 2 This shows the microstructure of the FeCoNiCr prepared in this embodiment. From... Figure 2 As can be seen, the material has a layered structure, which is beneficial for the loss of electromagnetic waves.

[0022] Figure 3 The FeCoNiCr / PDMS composite coating prepared in this embodiment exhibits SE performance in the 50–750 GHz frequency band. T Atlas. From Figure 3 As can be seen, the prepared composite coating exhibits excellent electromagnetic shielding performance in the terahertz band, and the coating's SE... T It can reach up to 92.8 dB.

[0023] Comparative Example 1 The only difference between this comparative example and Example 1 is that the total ball milling time in step 1 is 60 hours, while the other steps and parameters are exactly the same as in Example 1.

[0024] Figure 4 a is the XRD pattern of FeCoNiCr prepared in this embodiment. From Figure 4 As shown in Figure a, FeCoNiCr was successfully synthesized.

[0025] Figure 4 b is the magnetization curve of FeCoNiCr prepared in this embodiment. From Figure 4 As can be seen in b, FeCoNiCr is ferromagnetic, with a coercivity of 67.4 Oe and a saturation magnetization of 96.7 emu / g.

[0026] Figure 5 The FeCoNiCr / PDMS composite coating prepared in this embodiment exhibits SE performance in the 50–750 GHz frequency band. T Atlas. From Figure 5 As can be seen, the prepared composite coating exhibits excellent electromagnetic shielding performance in the terahertz band, and the coating's SE... T The maximum SE is 55.9 dB, lower than the maximum SE of the FeCoNiCr / PDMS composite coating in Example 1. T .

[0027] Comparative Example 2 The only difference between this comparative example and Example 1 is that the total ball milling time in step 1 is 80 hours, while the other steps and parameters are exactly the same as in Example 1.

[0028] Figure 6 a is the XRD pattern of FeCoNiCr prepared in this embodiment. From Figure 1 As shown in Figure a, FeCoNiCr was successfully synthesized.

[0029] Figure 6 b is the magnetization curve of FeCoNiCr prepared in this embodiment. From Figure 1 As can be seen in b, FeCoNiCr is ferromagnetic, with a coercivity of 75.5 Oe and a saturation magnetization of 103.7 emu / g.

[0030] Figure 7 The FeCoNiCr / PDMS composite coating prepared in this embodiment exhibits SE performance in the 50–750 GHz frequency band. T Atlas. From Figure 3 As can be seen, the prepared composite coating exhibits excellent electromagnetic shielding performance in the terahertz band, and the coating's SE... T The maximum SE is 35.9 dB, lower than the maximum SE of the FeCoNiCr / PDMS composite coating in Example 1. T .

[0031] Comparative Example 3 This comparative example is a pure PDMS coating sample. The preparation process is as follows: without adding any high-entropy alloy powder, the PDMS main agent and curing agent are mixed at a mass ratio of 10:1, stirred, poured into a mold of the same specifications as in Example 1, and cured at 60°C for 6 hours to obtain a pure PDMS coating.

[0032] Figure 8 The pure PDMS coating prepared in this embodiment exhibits SE performance in the 50~750 GHz frequency band. T Atlas. From Figure 8As can be seen, the prepared coating exhibits poor electromagnetic shielding performance in the terahertz band, and the SE of the coating... T The maximum value is only 5.0 dB, which proves that the electromagnetic shielding performance of the coatings in Example 1, Comparative Example 1 and Comparative Example 2 above mainly comes from the prepared FeCoNiCr.

[0033] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing a FeCoNiCr / PDMS composite flexible coating, characterized in that, Includes the following steps: S1. Preparation of high-entropy alloy powder: Fe, Co, Ni and Cr element powders in equimolar ratio were ball-milled to obtain FeCoNiCr high-entropy alloy powder; S2. Composite coating forming: The FeCoNiCr high-entropy alloy powder obtained in step S1 is mixed with polydimethylsiloxane, and after stirring, pouring and curing, the FeCoNiCr / PDMS composite flexible coating is obtained.

2. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 1, characterized in that, In step S1, the specific parameters of the ball milling include: the ball milling media consists of ball milling beads with a diameter of 10 mm and a diameter of 6 mm, with a ball-to-material ratio of (18~22):1, wherein the mass ratio of the 10 mm diameter ball milling beads to the 6 mm diameter ball milling beads is (1.8~2.2):1; a process control agent is added during the ball milling process, the ball milling speed is 380~420 rpm, the intermittent mode is adopted, and the total ball milling time is 60~80 h.

3. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 2, characterized in that, The process control agent is anhydrous ethanol, and its addition amount is 35~45 mL per 10g of mixed element powder.

4. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 2, characterized in that, The intermittent mode is as follows: the ball mill runs for 25-35 minutes, followed by an interval of 3-5 minutes.

5. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 1, characterized in that, In step S1, after ball milling, the resulting powder is dried at a temperature of 50-70°C for 20-28 hours.

6. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 1, characterized in that, In step S2, the polydimethylsiloxane comprises a main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is (9.5~10.5):

1.

7. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 1 or 6, characterized in that, In step S2, the mass fraction of the FeCoNiCr high-entropy alloy powder in the mixed system is 20%~40%.

8. The method for preparing the FeCoNiCr / PDMS composite flexible coating according to claim 1, characterized in that, In step S2, the curing conditions are: curing at 50~70℃ for 5~7 h.

9. A FeCoNiCr / PDMS composite flexible coating prepared by the method described in any one of claims 1 to 8.

10. The application of the FeCoNiCr / PDMS composite flexible coating as described in claim 9 in the preparation of terahertz electromagnetic wave shielding materials.

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