A cerium-doped iron-based thermally conductive and microwave-absorbing nanomaterial, its preparation method and application

Abstract

This invention discloses an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial, its preparation method, and its application, belonging to the field of thermal conductivity-microwave absorption technology. This invention utilizes a one-step hydrothermal method to prepare, for the first time, polycrystalline iron-doped cerium-based composite nanorods / wires, which are Fe... 0 ,Fe 2+ ,Fe 3+ A novel co-doped Ce(OH)3 / CeO2 core-shell composite exhibits a novel structure and formation mechanism. The size and aspect ratio of iron-doped cerium-based composite polycrystalline nanorods / wires can be further controlled by altering the molar ratios of strong base to cerium salt, iron salt to cerium salt, reaction temperature, and reaction time. The resulting material possesses excellent thermal conductivity and microwave absorption properties. The preparation method disclosed in this invention is simple to operate and produces novel product morphologies, overcoming the limitations of previous preparation methods, such as harsh reaction conditions, difficulty in controlling product morphology, and poor experimental repeatability. It has good potential for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of thermal conductivity-microwave absorption technology, and relates to a method for preparing polycrystalline iron-doped cerium-based composite nanorods / wires and their applications in thermal conductivity and microwave absorption, sensors, supercapacitors, photocatalysis, or lithium-ion batteries. Background Technology

[0002] Cerium-based compounds (such as CeO2, Ce(OH)3, CeOHCO3, and Ce2O3) have attracted considerable interest due to their lanthanide contraction, unpaired 4f electron orbitals, and abundant defects (lattice and oxygen vacancies), and have wide applications in catalysis, photoluminescence, fuel cells, biomedicine, and microwave absorption. Cerium-based compounds are dielectric microwave absorbing materials; their electromagnetic wave absorption mechanism originates from dielectric polarization, dielectric relaxation, and conductivity loss. Cerium-based compounds are derived from Ce... 4+ To Ce 3+ The oxidation state changes, which can balance polarization loss and conductivity loss, thereby enhancing microwave shielding, absorption capacity and thermal conductivity. It is a promising material in the field of thermal conductivity-microwave absorption.

[0003] Currently, there are several methods to improve the thermal conductivity and microwave absorption properties of cerium-based compounds / composites, including morphology and size control, heteroatom doping, defect engineering, and heterostructure construction. (i) Morphology / size control can be used to adjust shape anisotropy and directional polarization: Chinese patent document (CN108178178A) discloses a method for preparing small-particle-size basic cerium carbonate, but the experimental process requires a large amount of pure water to rinse the precipitate, which is cumbersome and complicated; Chinese patent document (CN103896322B) discloses a method for preparing dendritic basic cerium carbonate, using urea as a precipitant to synthesize basic cerium carbonate by hydrothermal method, but the urea pyrolysis reaction is relatively large, and the experimental yield is low. (ii) By combining cerium-based compounds with other materials (Fe, iron(II,III) oxide, polyaniline, etc.) to form heterojunctions, interface modulation to improve interfacial polarization has been achieved: Chinese patent document (CN114082396A) discloses a method for preparing a persimmon-shaped cerium ferrite / cerium dioxide composite adsorbent, but the experimental process requires high-temperature calcination, which is relatively cumbersome; Chinese patent document (CN103100389B) discloses a magnetic nano-cerium dioxide ozone catalyst, but the experimental process requires stirring under nitrogen protection for 5-10 hours, which is time-consuming and complex. In addition, the above-mentioned iron-doped cerium-based composite nanorods / wires have not been reported, and they are synthesized by a one-step hydrothermal method, which is simple and uses inexpensive and readily available raw materials.

[0004] The development of 5G communication technology has placed greater demands on advanced multifunctional materials with high microwave absorption and thermal conductivity. Among various candidate materials, nano-cerium-based composite materials have broad application prospects in the field of thermal conductivity-wave absorption. However, the morphology and size of existing cerium-based materials are difficult to control, the experimental procedures are cumbersome, the conditions are harsh, the operation is complicated, and the experimental repeatability is poor. In addition, it is difficult to meet the requirements of "thin, light, wide, and strong" microwave absorption performance and high thermal conductivity.

[0005] Therefore, how to develop a nano-cerium-based composite material that is easy to process and industrialize, has controllable morphology, size and composition, and has good thermal conductivity and microwave absorption properties is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of this invention is to address the problems existing in the prior art by providing an iron-doped cerium-based composite nanorod / wire thermally conductive and microwave-absorbing nanomaterial that is easy to process and has controllable size.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A thermally conductive and microwave-absorbing nanomaterial based on iron-doped cerium, wherein the thermally conductive and microwave-absorbing nanomaterial is an iron-doped cerium-based composite nanorod / wire prepared by a one-step hydrothermal method; the composite nanorod / wire is Fe 0 ,Fe 2+ ,Fe 3+ The co-doped Ce(OH)3 / CeO2 core-shell composite has a polycrystalline structure with a diameter of 15.5–59.3 nm and a length of 0.20–7.27 μm; and the atomic ratio of Fe / Ce in the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial is 0–0.432.

[0009] It is worth noting that the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial disclosed in this invention has excellent thermal conductivity and microwave absorption characteristics. The maximum effective bandwidth with a reflectivity of less than or equal to -10 dB is 5.12 to 9.26 GHz, the maximum absorption is -39.27 to -54.64 dB, and the thermal conductivity is 1.864 to 2.581 W / m·K.

[0010] Another objective of this invention is to provide a method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials that is green, environmentally friendly, and suitable for industrial production.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A method for preparing an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial, the method specifically comprising the following steps:

[0013] (1) Weigh the soluble cerium salt and soluble iron salt according to the stoichiometric ratio, and dissolve them in deionized water to obtain a mixed solution for later use;

[0014] (2) Add a strong base to the mixed solution, stir at room temperature for 30-60 min, then transfer to a reaction vessel and perform hydrothermal reaction to obtain the crude product;

[0015] (3) The crude product is soaked in water, and after multiple centrifugal washings, it is freeze-dried to finally obtain the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial.

[0016] The reaction equation is as follows:

[0017] Ce 3+ +OH - →Ce(OH)3

[0018] 4Ce(OH)3 + O2 + 2H2O → 4Ce(OH)4

[0019] Ce(OH)4 → CeO2 + 2H2O

[0020]

[0021]

[0022]

[0023] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0024] The preparation method disclosed in this invention is simple to operate and produces novel product morphology. It overcomes the problems of harsh reaction conditions, difficulty in controlling the morphology of reaction products, and poor experimental repeatability in previous preparation processes, and has good potential for industrial application.

[0025] Preferably, in step (1), the soluble iron salt is at least one of FeCl3·6H2O, Fe2(SO4)3·10H2O, Fe(NO3)3·9H2O, and Fe(Ac)3·4H2O; and the molar ratio of iron ions to cerium ions in the mixed solution is 0 to 1.

[0026] Preferably, in step (2), the strong base is NaOH, KOH or LiOH; the concentration ratio of the base to cerium ions is 5 to 25.

[0027] More preferably, the hydrothermal reaction temperature in step (2) is 120℃~200℃, and the hydrothermal reaction time is 4~24h.

[0028] Preferably, the freeze-drying temperature in step (3) is -60℃ to 90℃, and the freeze-drying time is 12 to 24 hours.

[0029] Another objective of this invention is to provide the application of the above-mentioned iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials in the fields of thermal conductivity-microwave absorption, sensors, supercapacitors, photocatalysis, or lithium-ion batteries.

[0030] As can be seen from the above technical solution, compared with the prior art, the present invention provides an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial, its preparation method and application, which has the following excellent effects:

[0031] 1) This invention presents the first-ever preparation of iron-doped Ce(OH)3 / CeO2 core-shell nanowires / rods using a one-step hydrothermal method, exhibiting novel structure and formation mechanism. Furthermore, the composition and aspect ratio of the iron-doped cerium-based composite were further controlled by altering the molar ratio of strong base to cerium salt, the molar ratio of iron salt to cerium salt, the reaction temperature, and the reaction time. The resulting material also possesses excellent thermal conductivity and microwave absorption properties.

[0032] 2) The iron-doped Ce(OH)3 / CeO2 core-shell nanowires / rods prepared in this invention have excellent properties such as novel structure, good dispersibility and uniformity, and adjustable size. For the first time, they have shown excellent thermal conductivity and microwave absorption performance as a multifunctional material for thermal conductivity and microwave absorption, which is significantly better than most reported materials.

[0033] 3) The iron-doped Ce(OH)3 / CeO2 core-shell nanowires / rods of the present invention are prepared by a one-step hydrothermal method. This method has the advantages of simple process, low risk, green and environmentally friendly, good repeatability, low requirements for instrument precision, high yield, and large-scale production, and therefore has good prospects for industrial application.

[0034] Therefore, in summary, the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials and their preparation methods disclosed in this invention have great market promotion and application value. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figures 1-3 The images show the phase and morphology of the product obtained in Example 1 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0037] Figures 4-6 The phase and morphology of the product obtained in Example 2 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0038] Figures 7-9The phase and morphology of the product obtained in Example 3 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0039] Figures 10-12 The figures show the phase composition, morphology, and absorption performance curves of the product obtained in Example 4 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0040] Figure 13 The morphology of the product obtained in Example 5 of this invention was measured under a scanning electron microscope.

[0041] Figure 14 The morphology of the product obtained in Example 6 of this invention was measured under a scanning electron microscope.

[0042] Figure 15 The morphology of the product obtained in Example 7 of this invention was measured under a scanning electron microscope.

[0043] Figure 16 The morphology of the product obtained in Example 8 of this invention was measured under a scanning electron microscope.

[0044] Figure 17 The morphology of the product obtained in Example 9 of this invention was measured under a scanning electron microscope.

[0045] Figure 18 The morphology of the product obtained in Example 10 of this invention was measured under a scanning electron microscope. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] This invention discloses an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial with simple processing, controllable size, and good thermal conductivity and microwave absorption properties, as well as its preparation method and application.

[0048] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] Example 1

[0051] A method for preparing a cerium-based thermally conductive and microwave-absorbing nanomaterial includes the following steps:

[0052] 8 mmol of CeCl3·7H2O was dissolved in 20 mL of deionized water and magnetically stirred for 10 min at room temperature. Then, 20 mL of NaOH solution (10 mol / L) was added to the solution, and stirring was continued for 60 min to ensure complete reaction. The solution was then transferred to a polytetrafluoroethylene liner and placed in a high-temperature oven at 180 °C for 24 h. After the product was naturally cooled to room temperature, it was washed with deionized water and then freeze-dried to obtain cerium oxide / cerium hydroxide polycrystalline nanowires.

[0053] The phase composition, morphology, and other properties of the obtained product as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 1-3 As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowire, with a diameter of approximately 36.5 nm and a length of approximately 2.26 μm.

[0054] As shown in Table 1, the obtained CeO2 / Ce(OH)3 polycrystalline nanowires have excellent microwave absorption characteristics, with a maximum effective bandwidth of 5.12 GHz and a maximum absorption of -50.28 dB with a reflectivity of less than or equal to -10 dB. The thickness is 2.4 mm and the thermal conductivity is 1.864 W / m·K.

[0055] Example 2

[0056] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the amount of CeCl3·7H2O is changed to 7.2 mmol and the amount of FeCl3·6H2O is changed to 0.8 mmol based on Example 1.

[0057] The phase composition, morphology, and other properties of the obtained product as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 4-6 As shown in the figure. The above analysis indicates that the product is an iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire with a diameter of approximately 27.5 nm and a length of approximately 1.05 μm. Furthermore, the atomic ratio of Fe to Ce in the iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire is 0.059.

[0058] As shown in Table 1, the obtained iron-doped CeO2 / Ce(OH)3 polycrystalline nanowires have excellent microwave absorption characteristics, with a maximum effective bandwidth of 9.26 GHz and a maximum absorption of -42.33 dB with a reflectivity of less than or equal to -10 dB. The thickness is 1.7 mm and the thermal conductivity is 2.581 W / m·K.

[0059] Example 3

[0060] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the amount of CeCl3·7H2O is changed to 5.6 mmol and the amount of FeCl3·6H2O is changed to 2.4 mmol based on Example 1.

[0061] The phase composition, morphology, and other properties of the obtained product as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 7-9 As shown in the figure. The above analysis indicates that the product is an iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire with a diameter of approximately 27.0 nm and a length of approximately 0.52 μm. Furthermore, the Fe / Ce atomic ratio in the iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire is 0.111.

[0062] As shown in Table 1, the obtained iron-doped CeO2 / Ce(OH)3 polycrystalline nanowires have excellent microwave absorption characteristics, with a maximum effective bandwidth of 6.64 GHz and a maximum absorption of -54.64 dB with a reflectivity of less than or equal to -10 dB. The thickness is 1.5 mm and the thermal conductivity is 2.240 W / m·K.

[0063] Example 4

[0064] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the amount of CeCl3·7H2O is changed to 4 mmol and the amount of FeCl3·6H2O is changed to 4 mmol based on Example 1.

[0065] The phase composition, morphology, and other properties of the obtained product as measured by XRD, EDX, and scanning electron microscopy are as follows: Figures 10-12 As shown in the figure. The above analysis indicates that the product is an iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire / rod with a diameter of approximately 46.0 nm and a length of approximately 0.20 μm. Furthermore, the atomic ratio of Fe to Ce in the iron-doped CeO2 / Ce(OH)3 polycrystalline nanowire / rod is 0.432.

[0066] As shown in Table 1, the obtained iron-doped CeO2 / Ce(OH)3 polycrystalline nanowires / rods have excellent microwave absorption characteristics, with a maximum effective bandwidth of 8.24 GHz and a maximum absorption of -39.27 dB with a reflectivity of less than or equal to -10 dB. The thickness is 1.8 mm and the thermal conductivity is 2.143 W / m·K.

[0067] Example 5

[0068] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the hydrothermal reaction time is changed to 4 hours based on Example 1.

[0069] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 13As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 nanowires with a diameter of about 17.0 nm and a length of about 0.35 μm. The size is significantly smaller than that of Example 1, which confirms the growth mechanism of the nanowires.

[0070] Example 6

[0071] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the hydrothermal reaction time is changed to 12h based on Example 1.

[0072] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 14 As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowire, with a diameter of about 29.5 nm and a length of about 1.92 μm. The size is slightly smaller than that of Example 1, which confirms the growth mechanism of the nanowire.

[0073] Example 7

[0074] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the hydrothermal reaction temperature is changed to 120°C based on Example 1.

[0075] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 15 As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowires with a diameter of about 22.0 nm and a length of about 0.55 μm. The size is significantly smaller than that of Example 1. The lower the temperature, the smaller the size of the nanowires.

[0076] Example 8

[0077] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the hydrothermal reaction temperature is changed to 200℃ based on Example 1.

[0078] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 16 As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowires with a diameter of about 59.3 nm and a length of about 7.27 μm. The size is significantly larger than that of Example 1. The higher the temperature, the larger the size of the nanowires.

[0079] Example 9

[0080] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the amount of NaOH is changed to 0.04 mmol and the concentration ratio of alkali to cerium ions is 5, based on Example 1.

[0081] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 17As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowires, but there are many particulate products. The nanowire diameter is about 15.5 nm and the length is about 0.44 μm. The size is significantly smaller than that of Example 1, which confirms that the nanowire size is smaller when the concentration ratio of alkali to cerium ions is small.

[0082] Example 10

[0083] A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, with other conditions remaining unchanged, except that the amount of NaOH is changed to 0.1 mmol and the concentration ratio of alkali to cerium ions is changed to 12.5 based on Example 1.

[0084] The morphology of the obtained product as measured by scanning electron microscopy is as follows: Figure 18 As shown in the figure. The above analysis shows that the product is CeO2 / Ce(OH)3 polycrystalline nanowires with a diameter of about 29.5 nm and a length of about 0.57 μm. The size is slightly smaller than that of Example 1, which confirms that the nanowire size is smaller when the concentration ratio of alkali to cerium ions is small.

[0085] The scope of this invention is not limited to the above embodiments; a combination of one or more embodiments can also achieve the purpose of this invention.

[0086] Table 1. Microwave absorption properties of the products obtained in Examples 1-4 of this invention.

[0087]

[0088] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterials, characterized in that, The thermally conductive and microwave-absorbing nanomaterial is an iron-doped cerium-based composite nanowire prepared by a one-step hydrothermal method; the composite nanowire is Fe 0 Fe 2+ Fe 3+ The co-doped Ce(OH)3 / CeO2 core-shell composite has a polycrystalline structure with a diameter of 15.5~59.3 nm and a length of 0.20~7.27 μm; and the Fe / Ce atomic ratio in the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial is greater than 0 and less than 0.

432. The nanomaterial exhibits excellent thermal conductivity and wave absorption properties, with a maximum effective bandwidth of 5.12~9.26GHz for reflectivity less than or equal to -10dB, a maximum absorption of -39.27~-54.64dB, and a thermal conductivity of 1.864~2.581W / m·K. The method specifically includes the following steps: (1) Weigh the soluble cerium salt and soluble iron salt according to the stoichiometric ratio, and dissolve them in deionized water to obtain a mixed solution for later use; The soluble iron salt is at least one of FeCl3·6H2O, Fe2(SO4)3·10H2O, Fe(NO3)3·9H2O, and Fe(Ac)3·4H2O; and the molar ratio of iron ions to cerium ions in the mixed solution is greater than 0 and less than or equal to 1. (2) Add a strong base to the mixed solution, stir at room temperature for 30-60 min, then transfer to a reaction vessel and perform hydrothermal reaction to obtain the crude product; The strong base is NaOH, KOH, or LiOH; the concentration ratio of the base to cerium ions is 5-25. The hydrothermal reaction temperature is 120℃~200℃, and the hydrothermal reaction time is 4~24h; (3) The crude product is soaked in water, and after multiple centrifugal washings, it is freeze-dried to finally obtain the iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial.

2. The method for preparing an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial according to claim 1, characterized in that, The freeze-drying temperature in step (3) is -60℃ to 90℃, and the freeze-drying time is 12 to 24 hours.

3. An iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial prepared by the method described in any one of claims 1 to 2.

4. An application of an iron-doped cerium-based thermally conductive and microwave-absorbing nanomaterial prepared by any one of claims 1 to 2 in the field of thermal conductivity-microwave absorption.

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