Fe or Ni-doped peanut-like co9s8 material and preparation and application thereof

Abstract

The application relates to a Fe or Ni doped peanut-like Co9S8 material, and preparation and application thereof. The material is obtained through a convenient hydrothermal reaction-hydrogen argon reduction reaction, is in a micron hollow peanut shape after hydrothermal reaction, and is formed by obvious scale-like structures on the surface. The pure-phase Co9S8 is successfully synthesized through hydrogen argon reduction, the surface flake is further crystallized to be compact, and the peanut-like structure is perfectly reserved. Further, cation doping is conducted on the precursor sulfide, and complete peanut-like Fe and Ni doped Co9S8 can be obtained. Different cations have a significant influence on the dielectric and lattice distortion of the material, so that the dielectric loss capacity of the peanut-like sulfide is improved. Meanwhile, the effective absorption bandwidth of the prepared Ni doped peanut-like Co9S8 can reach 6 GHz at 1.6 mm, the maximum reflection loss of the Fe doped peanut-like Co9S8 is-46.2 dB at 1.5 mm, and both can realize microwave full absorption in a Ku wave band (12-18 GHz) frequency range, and excellent electromagnetic wave loss capacity is exhibited.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a peanut-shaped Co9S8 material based on Fe or Ni doping, its preparation and application. Background Technology

[0002] With the rapid development of electronic technology, wireless communication, and high-precision equipment, electromagnetic pollution has brought great inconvenience and harm to people's daily lives. To address the electromagnetic pollution caused by civilian and military electronic equipment, significant efforts have been invested in manufacturing high-efficiency microwave absorbers. Decades of practice have proven that atomic-level modulation, heterojunctions, and morphological design methods for high-performance absorber units are highly competitive. Among these, atomic-level modulation, or atomic doping engineering, is considered a powerful tool for adjusting electronic structure and physicochemical properties. Current work mainly focuses on defect tuning through anion vacancy engineering. The urgent task is to overcome the limitations of atomic-level modulation through the rational design and promotion of cation substitution strategies.

[0003] In fact, significant efforts in atomic reconstruction, defect engineering, and atomic doping have been used to enhance microwave absorption response. For example, it is widely believed that atomic reconstruction can improve dielectric response by adjusting crystal phase and defects. Furthermore, experiments have shown that the conductivity of sulfur-vacancy-rich CoNi2S4 is significantly enhanced due to improved Fermi level hybridization. Therefore, the conductivity of materials can be effectively tuned by rationally introducing defects, lattice distortion, and stress, thereby further enhancing microwave absorption. In recent years, transition metal sulfides have become novel absorbers in the field of microwave materials due to their unique optical, magnetic, and electrical properties. Examples include CoS, Co3S4, MoS2, MnS, and CuS. Among them, cobalt sulfide exists in multiple phases, and microwave absorbers are mainly concentrated in CoS, CoS2, and multiphase mixed states of cobalt sulfide. The electromagnetic properties of traditional single transition metal sulfides have been limited, indicating significant potential for their development as microwave absorbers.

[0004] For example, Chinese patent CN201910427406.0 discloses a Co9S8 / sulfur-nitrogen co-doped carbon composite material and its preparation method. The method involves dissolving water-soluble cobalt, sulfur, and carbon sources in a mixed solvent to form a solution. The uniformly mixed raw materials are then placed in an atmospheric pressure reaction vessel and reacted thoroughly using a solvothermal method. The mixture is then oxidized at low temperature and calcined at high temperature to obtain the Co9S8 / sulfur-nitrogen co-doped carbon composite material. However, the composite material prepared by this method cannot form the desired peanut-shaped structure. Furthermore, this sulfur-nitrogen co-doped carbon composite material does not significantly improve microwave absorption performance. Our method and technology, on the other hand, significantly improve the microwave absorption characteristics of cation-doped sulfides, further broadening the application of metal sulfides in microwave absorption. Summary of the Invention

[0005] The purpose of this invention is to provide a peanut-shaped Co9S8 material based on Fe or Ni doping, its preparation and application, and to improve its attenuation capability for electromagnetic waves.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention provides a method for preparing a peanut-shaped Co9S8 material based on Fe or Ni doping, comprising the following steps:

[0008] (1) Weigh out the cobalt source, nickel source or iron source, trisodium citrate and urea, add them to deionized water, stir to dissolve, and obtain a clear and transparent mixed solution.

[0009] (2) Transfer the mixed solution into the reaction vessel and perform a hydrothermal reaction. Wash and dry the resulting reaction product to obtain the precursor powder.

[0010] (3) Take the precursor powder and sodium sulfide nonahydrate, add them to deionized water, and perform a second hydrothermal reaction. The resulting reaction product is washed, dried, and reduced at high temperature. Then, it is cooled to room temperature to obtain the Fe or Ni-doped Co9S8 material, which is the target product.

[0011] Furthermore, in step (1), the cobalt source is cobalt sulfate heptahydrate; the nickel source is trisodium citrate dihydrate; and the iron source is ferrous sulfate hexahydrate.

[0012] Furthermore, in step (1), when a nickel source is added, the molar ratio of the cobalt source to the nickel source satisfies: Co 2+ Ni 2+ = (0.075~0.15): (0.05~0.075); When an iron source is added, the molar ratio of the cobalt source to the iron source satisfies: Co 2+ Fe 2+ = (0.075~0.15): (0.025~0.035).

[0013] Furthermore, the sum of metal ions contained in the cobalt, nickel, or iron source (i.e., Co...) 2+ with Ni 2+ , or Co 2+ with Fe 2 + The molar ratio of urea and trisodium citrate is (0.005~0.007):0.004:(0.020~0.028), preferably 0.006:0.004:0.02440.

[0014] Specifically, the molar ratio of urea to trisodium citrate dihydrate is 6:1. For example, the mixed solution contains Co... 2+ The concentration is 0.075–0.15 mol / L, Ni 2+ The concentration is 0.05–0.075 mol / L, Fe 2+ The concentration is 0.025–0.035 mol / L.

[0015] Furthermore, in step (2), the temperature of the hydrothermal reaction is 120-180℃, preferably 150℃, and the time is 2-3h, preferably 2.5h.

[0016] Furthermore, in step (3), the mass ratio of the precursor powder to sodium sulfide nonahydrate is 5-7:1, preferably 6:1.

[0017] Furthermore, in step (3), the temperature of the secondary hydrothermal reaction is 150-210℃ and the time is 24-36h.

[0018] Furthermore, in step (3), the high-temperature reduction is carried out under a hydrogen-argon atmosphere.

[0019] Furthermore, in step (3), the temperature of high-temperature reduction is 300-500℃, which can be selected as 300℃, 400℃, 450℃ or 500℃, etc., and the time is 1-3h, which can be selected as 2h.

[0020] The second technical solution of the present invention provides a peanut-shaped Co9S8 material based on Fe or Ni doping, which is prepared by the preparation method described in the navigation. The material is characterized by being a hollow peanut-shaped material at the micrometer scale, with a length of 2 to 3 μm at both ends and a sheet-like structure on the surface.

[0021] The third technical solution of this invention provides an application of Fe or Ni-doped peanut-shaped Co9S8 material in the field of microwave absorption. Specifically, as a multifunctional microwave absorbing material, it can be used as an electromagnetic wave absorbing material. In specific applications, the prepared Fe or Ni-doped peanut-shaped Co9S8 powder is first uniformly mixed with sliced ​​paraffin at a 1:1 mass ratio. The mixture is poured into an aluminum mold and pressed into a ring sample with an inner diameter of 3.0 mm, an outer diameter of 7.0 mm, and a thickness of 2.0 mm. The complex relative permittivity and permeability in the range of 2.0-18.0 GHz are tested using a vector network analyzer of model N5230C.

[0022] This invention employs a convenient and efficient hydrothermal synthesis method to prepare peanut-shaped precursor carbonates. Further sulfidation yields hollow peanut-shaped transition metal sulfides. High-temperature reduction under a hydrogen-argon atmosphere produces pure-phase peanut-shaped hollow Co9S8, with its peanut-shaped exterior composed of nanosheets. This hollow peanut-shaped structure exhibits excellent overall performance in microwave absorption. Simultaneously, this invention also prepares Fe- or Ni-doped peanut-shaped hollow Co9S8, significantly enhancing the dielectric response of transition metal sulfides through cation substitution. Since the ionic radii of Fe and Ni are located on either side of Co, different cation substitutions can significantly enhance the polarization ability of the material, improving the dielectric loss capacity of the peanut-shaped hollow Co9S8.

[0023] Compared with existing technologies, the preparation method of Fe or Ni-doped peanut-shaped hollow Co9S8 material of the present invention is simple, easy to operate, and the preparation conditions are relatively mild and easy to control. The obtained target product is peanut-shaped, which facilitates the rapid transport of conductive electrons, and the surface is composed of regularly arranged sheet-like nanosheets, which is beneficial to interfacial polarization, multiple scattering, and impedance matching, thereby greatly enhancing the attenuation ability of Fe or Ni-doped peanut-shaped hollow Co9S8 to electromagnetic waves. At the same time, its hollow symmetrical structure has a large porosity, making it promising for applications in gas adsorption, catalysis, and electromagnetic interference. Attached Figure Description

[0024] Figure 1 The images shown are (a) SEM (scanning electron microscope) image of Co9S8 and (b) TEM (transmission electron microscope) image of Co9S8 in Example 1.

[0025] Figure 2 The images shown are: (a) SEM (scanning electron microscope) image of (Co8Fe)S8 obtained by doping with 0.001 mol Fe, (b) TEM (transmission electron microscope) image of (Co8Fe)S8 obtained by doping with 0.001 mol Fe, (c) SEM (scanning electron microscope) image of (Co7Fe2)S8 obtained by doping with 0.0015 mol Fe, and (d) TEM (transmission electron microscope) image of (Co7Fe2)S8 obtained by doping with 0.0015 mol Fe.

[0026] Figure 3 The images shown are: (a) SEM (scanning electron microscope) image of (Co8Ni)S8 obtained by doping with 0.002 mol Ni; (b) TEM (transmission electron microscope) image of (Co8Ni)S8 obtained by doping with 0.002 mol Ni; (c) SEM (scanning electron microscope) image of (Co7Ni2)S8 obtained by doping with 0.003 mol Ni; and (d) TEM (transmission electron microscope) image of (Co7Ni2)S8 obtained by doping with 0.003 mol Ni.

[0027] Figure 4 The XRD (X-ray diffraction) patterns of Co9S8 in Examples 1-3 and Co9S8 based on Fe or Ni doping are shown.

[0028] Figure 5 The diagram shows the real and imaginary parts of the complex permittivity of Co9S8 and Fe or Ni-doped Co9S8 in Examples 1-3 from 9 to 18 GHz.

[0029] Figure 6 The images shown are the detection spectra of different samples in Examples 4-10, where a) is the SEM image of the sample with a precursor to sodium sulfide ratio of 2:1; b) is the SEM image of the sample with a precursor to sodium sulfide ratio of 4:1; c) are the XRD images of the high-temperature reduction at 500℃ and 600℃; df) are the SEM images of the hydrothermal sulfide reaction time at 18h, 22h and 26h. Detailed Implementation

[0030] 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.

[0031] In the following embodiments, urea, trisodium citrate dihydrate, cobalt sulfate heptahydrate, nickel sulfate heptahydrate, ferrous sulfate heptahydrate, and sodium sulfide nonahydrate were all purchased from Sinopharm Reagent Co., Ltd. Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the art.

[0032] Example 1:

[0033] Synthesis of the peanut-shaped precursor: First, 0.006 mol of cobalt sulfate heptahydrate, 0.004 mol of trisodium citrate dihydrate, and 0.024 mol of urea were placed in the same beaker and dissolved in 40 mL of deionized water with stirring. Then, the solution was transferred to four Teflon-lined stainless steel autoclaves and kept at 150°C for 2.5 hours. The product was collected by centrifugation and washed three times with deionized water.

[0034] Subsequently, 0.2 g of the precursor was added to 40 mL of an aqueous solution along with 1.2 g of sodium sulfide nonahydrate. After thorough mixing, the mixture was transferred to a 50 mL Teflon autoclave and heated in an electric furnace at 180 °C for 30 hours. After the reaction was complete, the sample was centrifuged and dried, and then annealed in a hydrogen-argon atmosphere with a concentration of 5% (volume fraction, hydrogen) at 450 °C for 2 hours to obtain the sample Co9S8.

[0035] Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the field.

[0036] Example 2:

[0037] The majority of the results are the same as in Example 1, except that the precursor powder synthesis process is adjusted as follows:

[0038] 0.005 mol cobalt sulfate heptahydrate, 0.001 mol ferrous sulfate heptahydrate, 0.004 mol trisodium citrate dihydrate, and 0.024 mol urea were placed in the same beaker and dissolved in 40 mL of deionized water with stirring. The solution was then transferred to four Teflon-lined stainless steel autoclaves and kept at 150°C for 2.5 hours. The product was collected by centrifugation and washed three times with deionized water. Alternatively, 0.0045 mol cobalt sulfate heptahydrate and 0.0015 mol ferrous sulfate heptahydrate were used as another example.

[0039] Example 3:

[0040] The majority of the results are the same as in Example 1, except that the precursor powder synthesis process is adjusted as follows:

[0041] 0.003 mol cobalt sulfate heptahydrate, 0.003 mol nickel sulfate heptahydrate, 0.004 mol trisodium citrate dihydrate, and 0.024 mol urea were placed in the same beaker and dissolved in 40 mL of deionized water with stirring. The solution was then transferred to four Teflon-lined stainless steel autoclaves and kept at 150°C for 2.5 hours. The product was collected by centrifugation and washed three times with deionized water. Another set of examples based on Example 3 was prepared using 0.004 mol cobalt sulfate heptahydrate and 0.002 mol nickel sulfate heptahydrate.

[0042] The microstructure of the Fe or Ni-doped peanut-shaped hollow Co9S8 material in the above embodiments was characterized using scanning electron microscopy (SEM, Hitachi FE-SEM S-4800), with the powder sample coated on a conductive adhesive surface for testing. The microstructure information of a series of alloy materials was characterized using transmission electron microscopy (TEM, JEOL JEM-2100F), with the powder sample ultrasonically dispersed in ethanol, then dropped onto a carbon-supported copper mesh and dried for testing.

[0043] Figure 1The images show scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Example 1. As shown, the Co9S8 synthesized in Example 1 exhibits a hollow, peanut-like structure with a length of approximately 2–2.5 μm and a head width of 1.5 μm. The surface is composed of numerous stacked sheet-like nanosheets. The sample has a relatively uniform particle size distribution and good dispersibility. The morphology and size of Co9S8 after high-temperature reduction showed no significant changes, and the overall sample exhibited a uniform particle size distribution and good dispersibility. When used as a microwave absorber, its effective absorption frequency range is 11.5–17.5 GHz, and its thickness is 2.0 mm.

[0044] Compared with Example 1, such as Figure 2 As shown, the sample in Example 2 still maintained its complete peanut-like structure. The hollow and nanosheet structures maintained a good morphology. Since the entry of Fe ions easily reacts with S, and an excessive Fe ion concentration increases the risk of maintaining the peanut-like sample morphology, a suitable concentration of Fe ions was selected in this invention. Figure 3 As shown in Example 3, Ni ions were introduced. It is evident that Ni is relatively less likely to form bonds with S, and its impact on morphology is relatively minimal, allowing it to retain its original peanut-like structure.

[0045] Figure 4 The results show that the successful synthesis of Co9S8 based on Fe or Ni doping is also evidenced by the successful incorporation of Fe / Ni cations. As the cation concentration increases, a CoS / FeS impurity phase appears.

[0046] Figure 5 The real (μ'), imaginary (μ”) part of the complex permeability and the real (ε'), imaginary (ε”) part of the complex permittivity of Fe or Ni-doped peanut-shaped hollow Co9S8 are given in Examples 1-3 above. The real (μ') and imaginary (μ”) parts of the complex permeability are used to reveal the mechanism of its excellent microwave absorption performance. r =μ′–jμ″). The real part (ε') and imaginary part (ε″) of the complex permittivity are used to reveal the mechanism of its excellent microwave absorption performance (ε). r =ε′–jε″). As shown in the figure, the microwave absorption performance of this composite material mainly originates from dielectric loss and polarization loss. The substitution of cations can create a large number of defects, stresses and lattice distortions inside the material, improve the polarization loss capability of the material, and thus enhance its ability to absorb electromagnetic waves.

[0047] Example 4:

[0048] Most of the contents are the same as in Example 1, except that in this example, the mass ratio of sodium sulfide to the experimental precursor is adjusted to 2:1.

[0049] Example 5:

[0050] Most of the contents are the same as in Example 1, except that in this example, the mass ratio of sodium sulfide to the experimental precursor is adjusted to 4:1.

[0051] Example 6:

[0052] Compared with Example 1, most of them are the same, except that in this example, the high-temperature reduction temperature is adjusted to calcination at 500°C for 2 hours.

[0053] Example 7:

[0054] Compared with Example 1, most of them are the same, except that in this example, the high-temperature reduction temperature is adjusted to calcination at 600°C for 2 hours.

[0055] Example 8:

[0056] Most of the results are the same as in Example 1, except that the hydrothermal sulfidation reaction time is adjusted to 18 hours in this example.

[0057] Example 9:

[0058] Most of the results are the same as in Example 1, except that the hydrothermal sulfidation reaction time is adjusted to 22 hours in this example.

[0059] Example 10:

[0060] Most of the results are the same as in Example 1, except that the hydrothermal sulfidation reaction time is adjusted to 26 hours in this example.

[0061] Analysis of Examples 4 and 5 shows that different proportions of the precursor do not affect the morphology of the product after sulfidation, but are only related to the temperature and time of sulfidation. Analysis of Examples 6 and 7 shows that the sulfidized phase of Co9S8 does not change above 450°C. Analysis of Examples 8-10 shows that the hollow structure of the sample is formed directly in the hydrothermal part, and the longer the time, the more complete the sulfidation and the thinner the hollow wall structure.

[0062] As can be seen from the above embodiments, the material of the present invention is obtained through a convenient hydrothermal reaction-hydrogen-argon reduction reaction. Firstly, after hydrothermal treatment, it exhibits a micron-sized hollow peanut-like structure with a distinct scaly surface. Secondly, pure-phase Co9S8 is successfully synthesized through hydrogen-argon reduction, where the surface lamellae further crystallize and become more compact, while the peanut-like structure is perfectly preserved. Furthermore, cation doping of the precursor sulfide yields complete peanut-like Co9S8 based on Fe or Ni doping. Since different cations significantly affect the dielectric and lattice distortion of the material, the dielectric loss capability of the peanut-like sulfide is improved. Simultaneously, the Ni-doped peanut-like Co9S8 prepared by the present invention achieves an effective absorption bandwidth of 6 GHz at 1.6 mm, and the Fe-doped peanut-like Co9S8 has a maximum reflection loss of -46.2 dB at 1.5 mm, both achieving full microwave absorption in the Ku band (12-18 GHz) frequency range, demonstrating excellent electromagnetic wave loss capability.

[0063] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a peanut-shaped Co9S8 material based on Fe or Ni doping, characterized in that, Includes the following steps: (1) Weigh out the cobalt source, nickel source or iron source, trisodium citrate and urea, add them to deionized water, stir to dissolve, and obtain a clear and transparent mixed solution; (2) The mixed solution is transferred to the reaction vessel and subjected to a hydrothermal reaction. The resulting reaction product is washed and dried to obtain the precursor powder. (3) Take the precursor powder and sodium sulfide nonahydrate, add them to deionized water, and perform a second hydrothermal reaction. The resulting reaction product is washed, dried, and reduced at high temperature. Then, after cooling to room temperature, Fe and Ni doped Co9S8 materials are obtained, which are the target products. In step (1), when a nickel source is added, the molar ratio of the cobalt source to the nickel source satisfies: Co 2+ Ni 2+ = (0.075~0.15): (0.05~0.075); When an iron source is added, the molar ratio of the cobalt source to the iron source satisfies: Co 2+ Fe 2+ = (0.075~0.15): (0.025~0.035); The molar ratio of the sum of metal ions contained in the cobalt, nickel, or iron source to urea and trisodium citrate is (0.005~0.007):0.004:(0.020~0.028). In step (2), the temperature of the hydrothermal reaction is 120~180℃ and the time is 2-3h; In step (3), the mass ratio of precursor powder to sodium sulfide nonahydrate is 6:1; In step (3), the temperature of the secondary hydrothermal reaction is 150~210℃ and the time is 24-36h; In step (3), the high-temperature reduction is carried out under a hydrogen-argon atmosphere; The high-temperature reduction is carried out at a temperature of 300-500℃ for 1-3 hours.

2. The method for preparing a peanut-shaped Co9S8 material based on Fe or Ni doping according to claim 1, characterized in that, In step (1), the cobalt source is cobalt sulfate heptahydrate; the nickel source is trisodium citrate dihydrate; and the iron source is ferrous sulfate hexahydrate.

3. A peanut-shaped Co9S8 material based on Fe or Ni doping, prepared by the preparation method described in claim 1 or 2, characterized in that, The material is shaped like a hollow peanut at the micrometer scale, with a length of 2~3μm at both ends and a sheet-like structure on the surface.

4. The application of the Fe or Ni-doped peanut-shaped Co9S8 material as described in claim 3 in the field of microwave absorption.

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