Shape-controllable Cu2O / CuS composite material, and preparation method and application thereof

Abstract

The application relates to a morphology-controllable Cu2O / CuS composite material and a preparation method and application thereof. The method realizes accurate regulation of Cu2O crystal growth kinetics and crystal surface exposure by regulating the concentration of NaOH in the Cu2O synthesis process, so that Cu2O precursors with different morphologies are obtained. Subsequently, an in-situ sulfuration strategy is adopted to construct a Cu2O / CuS hetero-composite structure on the basis of maintaining the morphology skeleton of the precursors, realize semiconductor interface coupling and multi-scale interface regulation, and obtain a composite material with excellent and adjustable electromagnetic wave absorption performance. Compared with the prior art, the preparation process route is clear, the conditions are mild, the parameters are controllable, and the repeatability is good; the obtained Cu2O / CuS composite material has the advantages of interface polarization enhancement, synergistic dipole polarization and defect polarization, and conductive loss and dielectric loss coupling, and is beneficial to realize the synchronous improvement of impedance matching and energy attenuation capacity, and has important application value in the fields of electromagnetic wave absorption materials, electronic device electromagnetic protection and electromagnetic pollution treatment.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic functional materials, and in particular to a Cu2O / CuS composite material with controllable morphology, its preparation method, and its application. Background Technology

[0002] With the rapid development of wireless communication, radar detection, satellite navigation, the Internet of Things, and high-density integrated electronic devices, the electromagnetic environment is becoming increasingly complex, and electromagnetic radiation and interference are becoming more prominent in both civilian and military applications. On the one hand, complex electromagnetic signals can cause crosstalk in communication links, false triggering of sensitive devices, and decreased system stability; on the other hand, long-term electromagnetic exposure may pose potential health risks and information security hazards. Especially with the trends of high frequency, miniaturization, and high power density in 5G / 6G, the reflection, scattering, and coupling of electromagnetic waves in a limited space are more significant, placing higher demands on efficient, lightweight, broadband, and thin-layer electromagnetic wave absorbing materials. Currently, electromagnetic wave absorbing materials typically rely on magnetic loss materials (such as ferrites and metallic magnetic particles) or dielectric loss materials (such as carbon materials, conductive polymers, and some metal oxides / sulfides) to dissipate energy. However, traditional magnetic absorbing materials often suffer from problems such as high density, limited matching frequency bands, and high processing difficulty. While conductive absorbing systems, represented by carbon materials, have strong conductivity losses, they are prone to impedance mismatch in high-fill or high-conductivity states, leading to enhanced electromagnetic wave reflection at the material surface and thus weakening the absorption effect. In addition, many single-component absorbing materials have simple loss mechanisms and insufficient interface control, making it difficult to achieve synergistic optimization of both impedance matching and attenuation capability, thereby limiting their practical application in broadband, thin-layer, and complex service environments.

[0003] Against this backdrop, semiconductor heterostructures are considered an important direction for improving dielectric loss and broadband absorption capabilities due to their ability to construct rich interfaces, defects, and charge modulation mechanisms. Cu2O, as a typical p-type semiconductor, has controllable crystal morphology and tunable dielectric response; CuS has higher conductivity and polarization response. When Cu2O and CuS are used to construct a heterocomposite structure, significant charge redistribution and built-in electric fields can be formed at the interface, thereby inducing enhanced interface polarization, dipole polarization, and defect polarization. More reasonable dielectric parameters can be achieved through conductivity path modulation, improving the ability of electromagnetic waves to penetrate the material and energy dissipation efficiency. However, existing Cu-based oxide / sulfide microwave absorbing systems generally suffer from uncontrollable heterostructure construction methods, weak or uneven interface bonding, and difficulty in forming stable and effective polarization centers. The material microstructure (crystal plane exposure, morphology dimension, particle size) lacks programmable control, resulting in large fluctuations and insufficient repeatability of dielectric parameters. Coordinated adjustment of conductivity loss and polarization loss is difficult, easily leading to contradictions such as "high loss but mismatch" or "good matching but insufficient attenuation."

[0004] Chinese patent CN108862366A discloses a sheet-like Cu 2-x The application and preparation method of S(0≤x≤1) nanocrystals as microwave absorbers: This method first prepares copper-blue phase CuS nanosheets via a simple and easy wet chemical reaction using water-soluble divalent copper salts, organic surface ligand compounds, and water-soluble sulfides as raw materials. Then, these CuS nanosheets are used as a base material for further reaction with Cu... 2+ The reaction yields Cu with tunable composition. 2-x S nanocrystals. The Cu prepared in this application... 2-x S nanocrystalline materials, when used as microwave absorbers, possess advantages such as a wide absorption band, superior electromagnetic wave absorption performance, and stable performance, showing broad application prospects in fields such as electromagnetic stealth, electromagnetic shielding, and anti-electromagnetic radiation interference. However, Cu2₋ x While CuS nanocrystalline absorbing materials can form CuS nanosheets, their preparation methods rely on water-soluble copper salts and wet chemical reactions, resulting in a lack of controllability in crystal morphology and particle size distribution. This leads to large fluctuations in dielectric parameters and insufficient reproducibility. Furthermore, it is difficult to achieve synergistic control of conductivity and polarization loss, easily resulting in contradictions such as "high loss but mismatch" or "good matching but insufficient attenuation," thereby limiting broadband absorption performance and industrial application.

[0005] Chinese patent CN117696886A discloses an in-situ sulfurization synthesis method for Cu@Cu2S heterostructured nanowires, the method comprising: forming Cu-containing... 2+ The process involves preparing a mixed solution of hexadecylamine and glucose; removing air from the mixed solution and then performing a reduction reaction to obtain a copper nanowire reduction product; separating the reduction product and dispersing it in an ethanol solvent to form a copper nanowire ethanol dispersion; and adding a sulfide to the dispersion followed by a sulfidation reaction to obtain Cu@Cu2S heterostructured nanowire materials. This application describes a simple process with mild conditions, requiring no heating or post-processing, short reaction time, low equipment precision requirements, high controllability of product morphology, and good reproducibility, making it suitable for large-scale industrial production. However, while the in-situ sulfidation process of Cu@Cu2S heterostructured nanowires achieves the generation of Cu2S nanowires, the method is sensitive to reaction conditions and requires high precision in particle size uniformity, morphology control, and interface defect density, limiting its repeatability and scalability.

[0006] Therefore, there is an urgent need to develop an electromagnetic wave absorbing material that is simple to process, has controllable parameters, can be scaled up, and has excellent absorption performance and strong adaptability over a wide frequency range. Summary of the Invention

[0007] The purpose of this invention is to address at least one of the aforementioned problems by providing a morphology-controllable Cu2O / CuS composite material, its preparation method, and its applications. This material aims to achieve synergistic enhancement of impedance matching and multi-mechanism losses through precise control of the Cu2O precursor morphology and in-situ sulfidation to construct a high-quality heterogeneous interface. This results in an electromagnetic wave absorbing material with excellent absorption performance over a wide frequency range, lightweight design, and strong adaptability, meeting the application needs in fields such as electronic device protection, electromagnetic stealth, and electromagnetic pollution control. Given the current era of huge market demand, this material has broad development prospects.

[0008] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a Cu2O / CuS composite material with controllable morphology, comprising the following steps: Step S1: Dissolve the copper source in an ethanol-water mixed solvent and continuously stir it electromagnetically under oil bath conditions to form a homogeneous solution. Then, add an alkaline solution dropwise to the solution, continue stirring, and add a reducing agent to obtain the product Cu2O crystals. Step S2: Disperse the Cu2O crystals obtained in step S1 in deionized water to form a suspension, add a sulfiding agent to the suspension to carry out an in-situ sulfidation reaction, and obtain the target product Cu2O / CuS composite material.

[0009] Furthermore, in step S1, the volume ratio of ethanol to water in the ethanol-water mixed solvent is 1:10-20.

[0010] Furthermore, in step S1, the copper source is copper acetate monohydrate; the mass-volume ratio of the copper source to the ethanol-water mixed solvent is 0.01-0.1 g: 10 ml.

[0011] Furthermore, the temperature of the oil bath in step S1 is 40-60℃.

[0012] Furthermore, in step S1, the alkaline solution is a sodium hydroxide solution with a concentration of 3~9 mol / L.

[0013] Furthermore, in step S1, the reducing agent includes one or more of glucose, fructose, and ascorbic acid, with a concentration of 0.01-0.2 mol / L; the volume ratio of the alkaline solution to the reducing agent is 1:2-4.

[0014] Furthermore, in step S2, the sulfiding agent is either Na2S or thioacetamide, and the mass ratio of Cu2O crystals to the sulfiding agent is 1:0.1-0.5.

[0015] Furthermore, the vulcanization reaction time in step S2 is 20-40 min.

[0016] In a second aspect, the present invention provides a Cu2O / CuS composite material with controllable morphology, wherein the Cu2O morphology of the Cu2O composite material is controlled by controlling the NaOH concentration, and the crystal form of the Cu2O crystal is one of hexahedron, octahedron or pentahedron.

[0017] In a third aspect, the present invention provides an application of a morphology-controllable Cu2O / CuS composite material in electronic device protection, electromagnetic stealth, and electromagnetic pollution control.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention controls the microstructure of Cu2O by manipulating its crystal morphology, thereby regulating its dielectric parameters. In-situ sulfidation of morphology-controllable Cu2O generates a Cu2O / CuS heterocomposite structure. This method is simple and scalable. It utilizes the heterointerface to synergistically enhance multi-mechanism losses, achieves more reasonable dielectric parameters through conductivity path control, and simultaneously improves impedance matching (allowing electromagnetic waves to enter the material's interior) and energy dissipation efficiency (absorption loss). Ultimately, it yields an electromagnetic wave absorbing material with excellent absorption performance and strong adaptability over a wide frequency range. Attached Figure Description

[0019] Figure 1 These are scanning electron microscope (SEM) images of product 3, product 1, and comparative example 1 from Example 1 of the present invention. Figure 1 a represents the sulfide polyhedron Cu₂O / CuS. Figure 1 b represents a sulfide hexahedral Cu₂O / CuS. Figure 1 c represents unsulfurized polyhedron Cu2O; Figure 2 The X-ray diffraction (XRD) patterns of sample 1 in Example 1 and comparative example 1 of the present invention are shown. Figure 3 The diagrams show the absorption performance of product 3, product 1, and comparative example 1 in Example 1 of this invention. Figure 3 a represents the sulfide polyhedron Cu₂O / CuS. Figure 3 b represents a sulfide hexahedral Cu₂O / CuS. Figure 3 c represents unsulfurized polyhedron Cu2O; Figure 4 The reflection loss curves are for the samples prepared in Examples 2-3; Figure 5 The reflection loss curves are for the samples prepared in Examples 3-4; Figure 6 The reflection loss curves are for the samples prepared in Comparative Examples 2-3; Figure 7 Scanning electron microscope images of the samples prepared in Examples 2-3; Figure 8 Scanning electron microscope images of the samples prepared in Examples 4-5; Figure 9 Scanning electron microscope images of the samples prepared for Comparative Examples 2-3. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, each point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value, or combined with other lower or upper limits, to form a range not explicitly stated. In the description of this application, it should be noted that, unless otherwise stated, "above" includes the stated number, and "multiple" in "one or more" means two or more.

[0022] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0023] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these specific details.

[0024] To further understand the present invention, the following embodiments are provided. It is worth noting that, unless otherwise specified, all raw materials used in the present invention are commercially available; and all methods and equipment employed are common in the art.

[0025] Example 1 A method for controlling the morphology of a polyhedral Cu2O / CuS composite material includes the following steps: (1) Weigh 0.12g Cu(CH3COO)2·H2O and dissolve it in 4 mL of ethanol and 56 mL of deionized water. Stir continuously in a 50℃ water bath to form a Cu ion dispersion.

[0026] (2) Establish an alkaline solution concentration gradient: Dissolve NaOH in deionized water to prepare NaOH solutions with three increasing concentrations of 3 mol / L, 6 mol / L and 9 mol / L. Add 10 ml of the three different concentrations of NaOH solution dropwise to the Cu ion dispersion obtained in step (1). The color of the precipitate gradually changes from light blue to dark brown. Stir for 10 min, maintaining continuous stirring in an oil bath at 50℃ to ensure uniform ion distribution and avoid local oversaturation and rapid precipitation, thus ensuring uniform crystal nuclei. Temperature and stirring rate affect crystal growth kinetics, and the addition of OH... - Concentration control can precisely control the exposure of crystal faces, forming a Cu(OH)2 mixed solution.

[0027] OH - The activity of OH controls the effective surface energy (γ_{hkl}) of different crystal planes, which is the denominator of h_{hkl} / γ_{hkl} in Wulff's law, through selective adsorption of OH. - The molecules can adjust the relative stability of the {100} and {111} planes, thereby controlling the perpendicular distance from the center of the crystal plane to each crystal plane, i.e., the crystal form.

[0028] Choose an appropriate NaOH concentration range based on the target crystal form, for example: {100} Face dominance → Hexahedron formation; {111} Face dominance → Octahedron formation.

[0029] (3) Add 30 ml of 0.1 mol / L glucose solution to the Cu(OH)2 mixed solution obtained in step (2), and then... - Cu(OH)2 was reduced to Cu2O under the condition of adsorption regulation, and the obtained Cu2O nanocrystals were respectively designated as Sample 1-Sample 3.

[0030] In this embodiment, the mixture of samples 1-3 was stirred for 15 minutes until the crystals grew sufficiently. The color changed from light to dark (blue → brick red), indicating that Cu2O nucleation and growth were complete. Cu2O nanocrystals with different morphologies were obtained by centrifugation, washing, and vacuum drying. Analysis showed that the Cu2O nanocrystals obtained with a 3 mol / L sodium hydroxide solution were hexahedral, with {100} faces predominating, sharp edges, and a smooth, dense surface. The Cu2O nanocrystals obtained with a 6 mol / L sodium hydroxide solution were icosahedral, with {111} faces predominating, noticeably blunted edges, and a slightly rough surface. The Cu2O nanocrystals obtained with a 9 mol / L sodium hydroxide solution were pentahedral, with diverse exposed face types, rounded edges, a rough surface, and micropores or stepped structures.

[0031] (4) Weigh 100 mg of Cu2O nanocrystals (samples 1-3) obtained in step (3), disperse them in 50 mL of deionized water, and disperse them for 10 min using an ultrasonic machine to obtain Cu2O aqueous solution.

[0032] (5) Add 20 mg Na2S to 30 mL of deionized water until completely dissolved to obtain an aqueous solution of Na2S.

[0033] (6) Add the Na2S aqueous solution obtained in step (5) to the Cu2O aqueous solution obtained in step (4), stir for 30 min, and carry out sulfidation. At this time, some Cu2O is sulfided into CuS, and a Cu2O / CuS solution is obtained.

[0034] (7) Transfer the Cu2O / CuS solution obtained in step (6) into a centrifuge tube, centrifuge at 3500 r / min for 5 min, wash three times with deionized water to obtain Cu2O / CuS composite material, which are respectively recorded as product 1-product 3.

[0035] Example 2 This embodiment is largely the same as Embodiment 1, except that the oil bath temperature is changed to 40°C. Otherwise, it is the same as Embodiment 1.

[0036] Example 3 This embodiment is largely the same as Embodiment 1, except that the oil bath temperature is changed to 60°C. Otherwise, it is the same as Embodiment 1.

[0037] Example 4 This embodiment is largely the same as Embodiment 1, except that the vulcanization time is changed to 20 minutes. Otherwise, it is the same as Embodiment 1.

[0038] Example 5 This embodiment is largely the same as Embodiment 1, except that the vulcanization time is changed to 40 minutes. Otherwise, it is the same as Embodiment 1.

[0039] Comparative Example 1 An unsulfurized polyhedral Cu2O material is prepared by the following steps: (1) Weigh 0.12g Cu(CH3COO)2·H2O and dissolve it in 4 mL of ethanol and 56 mL of deionized water. Stir continuously in a 50℃ water bath to form a Cu ion dispersion.

[0040] (2) Add 10 mL of 3 mol / L concentrated sodium hydroxide solution dropwise to the Cu ion dispersion obtained in step (1). The color of the precipitate gradually changes from blue to dark brown. Stir for 10 min to form a Cu(OH)2 mixed solution.

[0041] (3) Add 30 mL of 0.1 mol / L glucose solution to the Cu(OH)2 mixed solution and continue stirring the mixture for 15 minutes. Then collect the synthesized brick-red powder by centrifugation, wash it with pure water, and dry it in a vacuum oven to obtain hexahedral Cu2O.

[0042] Comparative Example 2 This comparative example is largely the same as Example 1, except that the sodium hydroxide concentration is changed to 1 mol / L. Otherwise, it is the same as Example 1.

[0043] Comparative Example 3 This comparative example is largely the same as Example 1, except that the sodium hydroxide concentration is changed to 12 mol / L. Otherwise, it is the same as Example 1.

[0044] Performance testing: The products obtained in Example 1 and Comparative Example 1 were subjected to the following tests: 1. The morphology of the sample was determined using a scanning electron microscope.

[0045] 2. Electromagnetic parameters were determined using a vector network analyzer in the 2-18 GHz frequency range. Sample preparation: The sample and paraffin were uniformly mixed at mass ratios of 30% and 70%, respectively, and used for coaxial testing (outer diameter d). out = 7.00 mm, inner diameter d in =3.04 mm). Typically, reflection loss (RL) is used to evaluate the electromagnetic loss performance of the absorber. If the RL value is ≤ -10 dB (meaning 90% of the electromagnetic wave energy is absorbed), the electromagnetic loss at that frequency is considered effective.

[0046] Morphological analysis: Figure 1These are scanning electron microscope (SEM) images of product 3, product 1, and comparative example 1 from Example 1 of the present invention. Figure 1 a represents the sulfide polyhedron Cu₂O / CuS. Figure 1 b represents a sulfide hexahedral Cu₂O / CuS. Figure 1 c represents unsulfurized polyhedral Cu₂O, such as Figure 1 As shown, the SEM image of Example 1 is magnified to 100.0 kx. For sample 3, the overall sample has a near-spherical appearance based on a polyhedral framework, with significantly blunted edges and corners compared to before sulfidation, indicating a certain degree of surface reconstruction during the sulfidation process. Sample 3 exhibits significant roughening characteristics on its surface, forming a granular covering layer. These phenomena indicate that the sulfidation reaction preferentially grows on the polyhedral Cu2O surface and induces a dissolution-redeposition process, resulting in an outer CuS phase covering and generating abundant interface and defect structures, providing more active sites for interface and defect polarization in subsequent electromagnetic wave absorption. For sample 1, the main body of the sample still maintains a regular hexahedral shape with complete geometric contours, indicating that the sulfidation process has good "shape preservation" characteristics. Simultaneously, the particle surface changes from a relatively flat and dense state to a significantly rough state, covered by a uniformly distributed granular outer layer structure, exhibiting characteristics of continuous nucleation and growth of the sulfidation covering layer. This morphology indicates that the CuS phase is uniformly generated on the surface of the hexahedral Cu2O and forms a tight heterogeneous interface with Cu2O, which is beneficial for obtaining a stable and repeatable dielectric response and energy dissipation behavior.

[0047] X-ray diffraction spectrum: Figure 2 The X-ray diffraction (XRD) patterns of Sample 1 in Example 1 and Comparative Example 1 of this invention are shown below. Figure 2 As shown, for sample 1, the diffraction characteristic peaks corresponding to Cu2O can be observed, indicating that the main framework / crystal phase of Cu2O can be maintained after sulfidation treatment. Simultaneously, the composite material spectrum shows new weak diffraction peaks / shoulders accompanied by an overall decrease in peak intensity, peak broadening, and background elevation, indicating that a CuS phase is generated on the Cu2O surface during sulfidation. This CuS phase exists in a nano-sized / low-crystallinity or thin-layer covering manner, resulting in diffraction peaks that are not as sharp as those of the Cu2O sample. The comparative example is an unsulfided Cu2O sample, whose XRD diffraction peaks are sharp and the background is stable, indicating a high degree of crystallinity. The positions of the main diffraction peaks are consistent with the standard diffraction characteristics of cubic Cu2O, and no obvious impurity phase peaks are observed, indicating that the obtained precursor Cu2O is relatively pure and has a clearly defined crystal phase. The above results collectively demonstrate that the present invention successfully constructs CuS components on the Cu2O surface through in-situ sulfidation and forms a Cu2O / CuS heterocomposite structure without introducing obvious impurity phases, providing a structural and phase composition basis for interface polarization and multi-mechanism loss in subsequent electromagnetic wave absorption.

[0048] Wave absorption performance analysis: Figure 3 The diagrams show the absorption performance of product 3, product 1, and comparative example 1 in Example 1 of this invention. Figure 3 a represents the sulfide polyhedron Cu₂O / CuS. Figure 3 b represents a sulfide hexahedral Cu₂O / CuS. Figure 3 c represents unsulfurized polyhedral Cu₂O. The cuprous oxide / copper sulfide composite microwave absorbing material prepared in this invention is uniformly mixed with paraffin wax at a mass fraction of 30%, and pressed into a coaxial ring test sample (outer diameter 7 mm, inner diameter 3 mm). The complex permittivity and other electromagnetic parameters of the sample are measured using a vector network analyzer, and the reflection loss (RL) is calculated based on CST software. Figure 3 As shown, product 3 (pentahedral Cu₂O / CuS) exhibits excellent absorption performance even with relatively thin thicknesses: at a thickness of 2.41 mm, the minimum reflection loss at approximately 10.04 GHz reaches -50.02 dB; at a thickness of 2.04 mm, its effective absorption bandwidth (RL≤-10 dB) reaches 5.44 GHz, demonstrating a synergistic advantage of strong and broadband absorption. In contrast, product 1 (hexahedral Cu₂O / CuS) has a minimum reflection loss of -42.53 dB and an effective absorption bandwidth of 4.76 GHz at a thickness of 2.3 mm; Comparative Example 1 (pure Cu₂O) has weak absorption in the 2-18 GHz range, and even when the thickness increases to 5.15 mm, the minimum reflection loss is approximately -29.15 dB and the effective absorption bandwidth is only about 0.52 GHz. The above results demonstrate that the polyhedral Cu₂O / CuS heterojunction composite material of this invention achieves stronger reflection loss and a wider effective absorption bandwidth with a smaller thickness, and its overall absorption performance is significantly better than that of pure Cu₂O and hexahedral Cu₂O / CuS samples. The polyhedral Cu₂O / CuS composite material constructs a tight heterojunction interface through in-situ sulfidation and forms a rough, layered / defect-rich structure, enhancing interfacial polarization and dipole polarization and promoting multiple scattering, thereby improving electromagnetic loss and absorption efficiency.

[0049] Figure 4 , Figure 5 and Figure 6 The reflection loss curves of the samples prepared in Examples 2-3, 4-5, and Comparative Examples 2-3 of this invention are used to illustrate the influence of different synthesis parameters on the microwave absorption performance of the materials. Figure 4 The reflection loss curves are for the samples prepared in Examples 2-3; Figure 5 The reflection loss curves are for the samples prepared in Examples 4-5; Figure 6The reflection loss curves for the samples prepared in Comparative Examples 2-3 are shown. During the test, the obtained samples were uniformly mixed with paraffin at a mass fraction of 30%, pressed into coaxial ring samples (outer diameter 7 mm, inner diameter 3 mm), and the electromagnetic parameters were measured using a vector network analyzer, and the reflection loss (RL) was calculated accordingly. Figure 4 The effect of temperature on the synthesis of the precursor Cu2O (Examples 2-3). At lower temperatures (40°C), the minimum reflection loss of the sample was approximately -18.53 dB, and the effective absorption bandwidth was only 0.88 GHz. At higher temperatures (60°C), the minimum reflection loss increased to -29.36 dB, but the effective absorption bandwidth was only 0.52 GHz. This indicates that although the absorption in local frequency bands was enhanced after the temperature deviated from the suitable range, the overall broadband absorption capability was weak. Figure 5 The effect of different vulcanization times (Examples 4-5). After vulcanization for 20 min, the sample with a thickness of 2.50 mm achieved a minimum reflection loss of -44.20 dB and an effective absorption bandwidth of 3.28 GHz, exhibiting good absorption intensity. However, after vulcanization for 40 min, the minimum reflection loss decreased to -21.17 dB and the effective absorption bandwidth was 2.92 GHz, indicating that excessively long vulcanization time would result in an excessively high degree of surface vulcanization, weakening impedance matching and absorption performance. Figure 6 The effect of alkaline solution concentration on the synthesis of the precursor Cu2O is shown in Comparative Examples 2-3. Under lower alkaline concentration conditions (1M), the minimum reflection loss of the sample is -15.87 dB, and the effective absorption bandwidth is 2.9 GHz; while under higher alkaline concentration conditions (12M), the minimum reflection loss increases to -24.05 dB, and the effective absorption bandwidth is 3.24 GHz, showing superior absorption capacity. These results indicate that synthesis temperature, sulfidation time, and alkaline solution concentration all significantly affect the microwave absorption performance of the Cu2O / CuS composite material. Specifically, the overall microwave absorption performance of the sample under the lower concentration conditions is lower than that obtained under the optimized conditions of this invention, indicating that only within a suitable parameter window can the heterogeneous interface construction, surface defect control, and impedance matching be balanced to achieve a better electromagnetic wave absorption effect.

[0050] Figure 7 , Figure 8 and Figure 9 The images are scanning electron microscope (SEM) images of the samples prepared under the extreme conditions of this invention in Examples 2-3, 4-5, and Comparative Examples 2-3, used to illustrate the influence of different synthesis parameters on the morphology of the precursor Cu2O and the subsequent sulfidation results of the Cu2O / CuS samples.

[0051] Figure 7 The extreme values ​​of the synthesis temperature of the precursor Cu2O correspond to the changes in temperature (Examples 2-3). From Figure 7As can be seen, at a lower temperature of 40 ℃, the sample exhibits a relatively regular octahedral morphology with complete particle outlines and a relatively uniform surface, indicating that crystal growth is relatively mild under these conditions, which is conducive to the formation of regular crystal faces. However, at a higher temperature of 60 ℃, the particles transform into a polyhedral structure with a significantly rough surface and more attached impurities, indicating that the increased temperature accelerates the nucleation and growth rate, leading to an increase in surface by-products and a decrease in morphological uniformity.

[0052] Figure 8 The end values ​​of the sulfidation time corresponding to the Cu2O precursor (Examples 4-5). From Figure 8 As can be seen, when the sample is sulfided for 20 min, although the overall sample maintains a polyhedral framework, there are many surface deposits and they are unevenly distributed, indicating that the sulfidation reaction is not yet sufficient and the formation of the CuS outer layer is discontinuous. When the sample is sulfided for 40 min, the particle surface is covered by a denser rough layer, and the original crystal face features are further weakened, indicating that the degree of sulfidation is too high, which can easily cause excessive surface growth and is not conducive to obtaining a uniform and controllable heterostructure.

[0053] Figure 9 The corresponding changes in NaOH concentration during the synthesis of the precursor Cu2O (Comparative Examples 2-3). From Figure 9 As can be seen, under the lower alkali concentration of 1 M, the obtained sample mainly exhibits a hexahedral morphology, but with many surface impurities, indicating that although the crystals can form a relatively regular cubic framework at lower alkali concentrations, the surface purity is poor. However, under the higher alkali concentration of 12 M, the sample transforms into an octahedral morphology, with clear crystal faces and regular outlines, indicating that increasing the OH concentration... - Activity can effectively regulate the relative growth rate of different crystal planes, thereby achieving the transformation of crystal morphology from hexahedron to octahedron. The above results show that synthesis temperature, sulfidation time, and alkali solution concentration all significantly affect the morphology evolution and interface construction of the Cu2O / CuS system. Therefore, reasonable control of the above parameters is the key to optimizing the structure and performance of the material of this invention.

[0054] The foregoing has shown and described the basic process, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Cu2O / CuS composite material with controllable morphology, characterized in that, Includes the following steps: Step S1: Dissolve the copper source in an ethanol-water mixed solvent and continuously stir it electromagnetically under oil bath conditions to form a homogeneous solution. Then, add an alkaline solution dropwise to the solution, continue stirring, and add a reducing agent to obtain the product Cu2O crystals. Step S2: Disperse the Cu2O crystals obtained in step S1 in deionized water to form a suspension, add a sulfiding agent to the suspension to carry out an in-situ sulfidation reaction, and obtain the target product Cu2O / CuS composite material.

2. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S1, the volume ratio of ethanol to water in the ethanol-water mixed solvent is 1:10-20.

3. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S1, the copper source is copper acetate monohydrate; the mass-volume ratio of the copper source to the ethanol-water mixed solvent is 0.01-0.1 g: 10 ml.

4. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S1, the temperature of the oil bath is 40-60℃.

5. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S1, the alkaline solution is a sodium hydroxide solution with a concentration of 3~9 mol / L.

6. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S1, the reducing agent includes one or more of glucose, fructose, and ascorbic acid, with a concentration of 0.01-0.2 mol / L; the volume ratio of alkaline solution to reducing agent is 1:2-4.

7. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, In step S2, the sulfiding agent is either Na2S or thioacetamide, and the mass ratio of Cu2O crystals to the sulfiding agent is 1:0.1-0.

5.

8. The method for preparing a morphology-controllable Cu2O / CuS composite material according to claim 1, characterized in that, The vulcanization reaction time in step S2 is 20-40 min.

9. A Cu₂O / CuS composite material with controllable morphology prepared by any one of the methods described in claims 1-8, characterized in that, The Cu2O / CuS composite material achieves Cu2O morphology regulation by controlling the NaOH concentration, and the Cu2O crystal has a crystal form of hexahedron, octahedron or pentahedron.

10. The application of a morphology-controllable Cu2O / CuS composite material as described in claim 9 in electronic device protection, electromagnetic stealth, and electromagnetic pollution control.

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