Silver-loaded molybdenum carbide composite microwave absorption material and its method for photoinduced self-reduction preparation

Abstract

The present invention discloses a silver-loaded molybdenum carbide composite microwave absorption material and a method for its photo-induced self-reduction preparation. In the present invention, a molybdenum carbide matrix material is obtained by high-temperature carbonization, and then silver nanoparticles are uniformly loaded on the surface of molybdenum carbide by a photo-induced self-reduction method under the condition of no reducing agent, obtaining a silver-loaded molybdenum carbide composite microwave absorption material. This method improves the traditional process of metal-doped molybdenum carbide, avoids the aggregation of silver nano-ions, and the silver nanoparticles are well combined with the molybdenum carbide matrix. The obtained material has good electromagnetic wave absorption performance. When the frequency is 17.6 GHz and the thickness is 1.5 mm, the minimum RL value is -45 dB. At the same time, the preparation process of this invention is simple, with low energy consumption, easy to control conditions, green and environmentally friendly, and suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic composite electromagnetic wave absorbing materials, specifically relates to a silver-loaded molybdenum carbide composite absorbing material, and also relates to a photoinduced self-reduction preparation method of the silver-loaded molybdenum carbide composite absorbing material. Background Art

[0002] In recent years, with the continuous rapid development of science and technology, electronic information technology has brought great convenience to people's lives. However, the electromagnetic pollution caused by excessive electromagnetic radiation has also brought great harm to information security and people's health. Absorbing materials can effectively suppress the harm caused by electromagnetic waves and enhance public safety. Molybdenum carbide, as an ideal absorbing material, has good dielectric properties, and at the same time exhibits high melting point, good chemical stability and mechanical properties. However, single molybdenum carbide has defects such as a single loss mechanism and a narrow absorption frequency band, and its performance cannot meet the requirements of "thin, light, strong, and wide" for commercial absorbing materials. Therefore, the research on the preparation and absorbing properties of molybdenum carbide-based composites has attracted extensive attention. Researchers have begun to dope metal elements into molybdenum carbide to improve its absorbing properties. Gao et al. synthesized a one-dimensional nickel / molybdenum carbide nanocomposite by a hydrothermal method and found that the minimum RL value was -55.91 dB at a frequency of 9.28 GHz (Frontiers in Chemistry, 2019, 7, 427). Dai et al. prepared a cobalt / molybdenum carbide composite by a high-temperature sintering method, and the minimum RL value was -20 dB at a frequency of 6 GHz (Dalton Trans., 2018, 47, 14767). It can be found that doping metal elements into molybdenum carbide has an obvious improvement effect on the absorption of electromagnetic waves by molybdenum carbide. However, at present, the preparation of molybdenum carbide doped with metals to form composites generally uses a high-temperature sintering method. This method has a long reaction time, an unsafe production process, is easy to generate harmful gases, pollutes the air, and the doped metals are uneven and easy to form agglomerated particles. Summary of the Invention

[0003] The purpose of the present invention is to provide a photoinduced self-reduction preparation method of a silver-loaded molybdenum carbide composite absorbing material, which solves the problems of complex preparation process and easy environmental pollution of the existing absorbing materials doped with metals.

[0004] The technical solution adopted by the present invention is a silver-loaded molybdenum carbide composite absorbing material and its photoinduced self-reduction preparation method. The specific operation steps are as follows:

[0005] Step 1: Mix molybdate, 4-chloro-o-phenylenediamine, and deionized water and stir evenly. Add an acid to adjust the pH value of the mixed solution; place the mixed solution in an oil bath and heat and stir it at a constant temperature. After naturally cooling to room temperature, centrifuge and dry to obtain a yellowish-brown solid powder A;

[0006] Step 2: Place A in a tubular furnace and calcine it in a nitrogen atmosphere to obtain black powder B;

[0007] Step 3: Add black powder B to silver nitrate solutions with different concentrations, and ultrasonically mix them evenly to obtain a mixed solution C.

[0008] Step 4: Under the irradiation of an ultraviolet lamp, in-situ reduction of photoinduced silver nanoparticles is achieved under the condition of no reducing agent in the mixed solution C to form a silver-loaded molybdenum carbide composite microwave absorption material, which is black powder D.

[0009] Step 5: Mix black powder D, paraffin, and carbon nanotubes in a certain proportion, and then press them into a ring-shaped sample for microwave absorption performance testing.

[0010] The characteristics of the present invention also lie in that,

[0011] Furthermore, the molybdate in Step 1 is (NH4)6Mo7O 24 ·4H2O, and its mass ratio to 4-chloro-o-phenylenediamine is 1:2 - 3;

[0012] Furthermore, in Step 1, the acidity of the solution is adjusted with perchloric acid, and the pH value of the solution is adjusted to 1 - 3;

[0013] Furthermore, in Step 1, the temperature of the constant-temperature heating in the oil bath is 30 - 60 °C, and the heating and stirring time is 1.5 - 3 h;

[0014] Furthermore, in Step 2, the heating rate of the tubular furnace during the carbonization process is 100 °C / h, and the temperature is maintained at 750 °C for 12 h;

[0015] Furthermore, the black powder in Step 2 is α-phase molybdenum carbide;

[0016] Furthermore, the concentration of the silver nitrate solution in Step 3 is 9 - 11 mmol / L;

[0017] Furthermore, in Step 4, the irradiation intensity of the ultraviolet lamp is 40 - 60 w, and the irradiation time is 0.5 - 2 h;

[0018] Furthermore, in Step 4, the irradiation wavelength of the ultraviolet lamp is 300 - 400 nm.

[0019] The second technical solution adopted by the present invention is that the silver-loaded molybdenum carbide composite microwave absorption material can be used as an electromagnetic wave absorption material.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a method for preparing a silver-loaded molybdenum carbide composite absorbing material by photo-induced self-reduction. First, using molybdenum salt as the raw material, an α-phase molybdenum carbide matrix with a regular face-centered cubic closest-packed structure is prepared through a calcination and carbonization process. Then, silver nanoparticles are loaded on the surface of molybdenum carbide by in-situ photo-induction to form a new molybdenum carbide composite material. This preparation process is simple, the conditions are easy to control, the energy consumption is low, it is green and environmentally friendly, and the yield is high, making it suitable for large-scale industrial production. Different from the existing high-temperature sintering method of doping molybdenum carbide with metals, through the in-situ induction method of ultraviolet light, a layer of Ag nanoparticles is deposited on the surface of the MoC powder, and some Ag nanoparticles enter the interior of the MoC, greatly enhancing the electromagnetic wave absorption performance of the material. This method solves the problems of uneven doping of existing doped metals, complex doping processes, and environmental pollution, and improves the wave absorption performance of the composite material. Brief Description of the Drawings

[0022] Figure 1 It is a synthesis route diagram of the silver-loaded molybdenum carbide composite absorbing material of the present invention.

[0023] Figure 2 It is an XRD spectrum diagram of the silver-loaded molybdenum carbide composite absorbing material of the present invention.

[0024] Figure 3 It is a reflection loss diagram of the silver-loaded molybdenum carbide composite absorbing material of the present invention.

[0025] Figure 4 It is an absorption bandwidth diagram of the silver-loaded molybdenum carbide composite absorbing material of the present invention.

[0026] Figure 5 It is a curve diagram of the dielectric loss parameter of the silver-loaded molybdenum carbide composite absorbing material of the present invention changing with frequency.

[0027] Figure 6 It is a curve diagram of the tangent value of the dielectric loss parameter of the silver-loaded molybdenum carbide composite absorbing material of the present invention changing with frequency. Detailed Embodiments

[0028] The silver-loaded molybdenum carbide composite absorbing material and the method for preparing the same by photo-induced self-reduction provided by the present invention first prepare a molybdenum carbide matrix material, and then under the condition of visible light irradiation and without adding a reducing agent, silver is reduced on the surface of molybdenum carbide to obtain the silver-loaded molybdenum carbide composite absorbing material.

[0029] The present invention provides a silver-loaded molybdenum carbide composite absorbing material and a method for preparing the same by photo-induced self-reduction. In order to more clearly illustrate the technical solution of the present invention, a complete description will be made in combination with the drawings in the embodiments. The following is further detailed through specific embodiments.

[0030] Example 1

[0031] A method for preparing silver-loaded molybdenum carbide composite microwave absorbing material by photo-induced self-reduction is as follows Figure 1 as shown, and the specific operation steps are as follows:

[0032] Step 1: Add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 into a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h. Wait for natural cooling to room temperature, and then centrifuge and dry to obtain a yellowish-brown precursor A.

[0033] Step 2: Put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 70-120 °C / h, keep the temperature at 750 °C for 8-12 h, and naturally cool to room temperature to obtain a black powder B (i.e., α-MoC matrix);

[0034] Step 3: Add the black powder B into a beaker containing 10 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain a solution C.

[0035] Step 4: Slowly stir the solution C, irradiate it under a UV lamp (365 nm, 50 W) for 1 h. After that, centrifuge (5500 r / min, 10 min), wash with deionized water to obtain a black powder D (i.e., silver-loaded molybdenum carbide composite microwave absorbing material).

[0036] Step 5: Mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, and then press them into a ring-shaped sample for microwave absorption performance testing.

[0037] Example 2

[0038] A method for preparing silver-loaded molybdenum carbide composite microwave absorbing material by photo-induced self-reduction, and the specific operation steps are as follows:

[0039] Step 1: Add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 into a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h. Wait for natural cooling to room temperature, and then centrifuge and dry to obtain a yellowish-brown precursor A.

[0040] Step 2: Put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 100 °C / h, keep the temperature at 750 °C for 12 h, and naturally cool to room temperature to obtain a black powder B (α-MoC matrix).

[0041] Step 3: Add the black powder B into a beaker containing 9 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain a solution C.

[0042] Step 4, slowly stir solution C. Under the irradiation of an ultraviolet lamp (365 nm, 50 W), the irradiation time is 1 h. After completion, perform centrifugation (5500 r / min, 10 min), and wash with deionized water to obtain the black powder D of silver-loaded α-MoC wave-absorbing material.

[0043] Step 5, mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, then press them into a ring-shaped sample and conduct wave-absorbing performance tests.

[0044] Example 3

[0045] A method for preparing a silver-loaded molybdenum carbide composite wave-absorbing material by photoinduced self-reduction, the specific operation steps are as follows:

[0046] Step 1, add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 to a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h, wait for natural cooling to room temperature, and centrifuge and dry to obtain the yellowish-brown precursor A.

[0047] Step 2, put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 100 °C / h, keep the temperature at 750 °C for 12 h, and naturally cool to room temperature to obtain the black powder B (α-MoC matrix).

[0048] Step 3, add the black powder B to a beaker containing a 11 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain solution C.

[0049] Step 4, slowly stir solution C. Under the irradiation of an ultraviolet lamp (365 nm, 50 W), the irradiation time is 1 h. After completion, perform centrifugation (5500 r / min, 10 min), and wash with deionized water to obtain the black powder D of silver-loaded α-MoC wave-absorbing material.

[0050] Step 5, mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, then press them into a ring-shaped sample and conduct wave-absorbing performance tests.

[0051] Example 4

[0052] A method for preparing a silver-loaded molybdenum carbide composite wave-absorbing material by photoinduced self-reduction, the specific operation steps are as follows:

[0053] Step 1: Add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 into a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h. Wait for it to cool naturally to room temperature, and then centrifuge and dry to obtain a yellowish-brown precursor A.

[0054] Step 2: Put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 100 °C / h, keep the temperature at 750 °C for 12 h, and then cool naturally to room temperature to obtain a black powder B (α-MoC matrix).

[0055] Step 3: Add the black powder B into a beaker containing 10 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain a solution C.

[0056] Step 4: Slowly stir the solution C, irradiate it under a UV lamp (365 nm, 50 W) for 0.5 h. After that, centrifuge (5500 r / min, 10 min), wash with deionized water to obtain a black powder D of silver-loaded α-MoC microwave absorption material.

[0057] Step 5: Mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, and then press them into a ring-shaped sample for microwave absorption performance testing.

[0058] Example 5

[0059] A method for the photoinduced self-reduction preparation of silver-loaded molybdenum carbide composite microwave absorption material, and the specific operation steps are as follows:

[0060] Step 1: Add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 into a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h. Wait for it to cool naturally to room temperature, and then centrifuge and dry to obtain a yellowish-brown precursor A.

[0061] Step 2: Put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 100 °C / h, keep the temperature at 750 °C for 12 h, and then cool naturally to room temperature to obtain a black powder B (α-MoC matrix).

[0062] Step 3: Add the black powder B into a beaker containing 10 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain a solution C.

[0063] Step 4, slowly stir solution C. Under the irradiation of an ultraviolet lamp (365 nm, 50 W), the irradiation time is 1.5 h. After completion, centrifuge (5500 r / min, 10 min), wash with deionized water, and obtain the black powder D of silver-loaded α-MoC microwave absorption material.

[0064] Step 5, mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, then press them into a ring-shaped sample for microwave absorption performance testing.

[0065] Example 6

[0066] A method for preparing silver-loaded molybdenum carbide composite microwave absorption material by photoinduced self-reduction, and the specific operation steps are as follows:

[0067] Step 1, add 1 g of ammonium molybdate and 2.5 g of 4-chloro-o-phenylenediamine solid with a mass ratio of 1:2.5 to a round-bottom flask, pour in 60 mL of deionized water to dissolve, adjust the acidity of the solution with perchloric acid to make the pH 2, control the temperature at 50 °C in an oil bath and stir for 2.5 h, wait for natural cooling to room temperature, and centrifuge and dry to obtain a khaki precursor A;

[0068] Step 2, put the precursor A into a porcelain boat, use a tube furnace in a nitrogen atmosphere, control the heating rate at 100 °C / h, keep the temperature at 750 °C for 12 h, and naturally cool to room temperature to obtain a black powder B (α-MoC matrix);

[0069] Step 3, add the black powder B to a beaker containing 10 mmol / L silver nitrate solution, and ultrasonically mix it evenly to obtain solution C.

[0070] Step 4, slowly stir solution C. Under the irradiation of an ultraviolet lamp (365 nm, 50 W), the irradiation time is 2 h; after completion, centrifuge (5500 r / min, 10 min), wash with deionized water, and obtain the black powder D of silver-loaded α-MoC microwave absorption material;

[0071] Step 5, mix the black powder D, paraffin, and carbon nanotubes in a certain proportion, then press them into a ring-shaped sample for microwave absorption performance testing.

[0072] Detailed description of the drawings:

[0073] As Figure 2 shown, the XRD patterns of the silver-loaded molybdenum carbide composite microwave absorption material and the α-MoC material. It can be found from the XRD patterns that silver nanoparticles are successfully loaded on the surface of α-MoC. The angles at 38.1°, 44.3°, 64.4°, and 77.5° correspond to the (111), (200), (220), and (311) crystal planes of silver.

[0074] AsFigure 3 As shown, it is the microwave absorption performance diagram of the synthesized silver-loaded molybdenum carbide composite microwave absorption material. It can be found that when the frequency is 17.6 GHz and the thickness is 1.5 mm, the minimum RH value is -45 dB.

[0075] As Figure 4 shown, it is the effective microwave absorption bandwidth diagram of the synthesized silver-loaded molybdenum carbide composite microwave absorption material with different thicknesses. When the coating thickness is controlled between 1.0 - 5.0 mm, the covering frequency range of the silver-loaded α-MoC composite material is 10.9 - 15.2 GHz. When the frequency is 112.7 GHz and the thickness is 2.0 mm, the effective absorption bandwidth is the widest.

[0076] As Figure 5 shown, it is the curves of the real part of the permittivity (ε') and the imaginary part of the permittivity (ε”) of the silver-loaded molybdenum carbide composite microwave absorption material varying with frequency. It can be found that ε' and ε” gradually decrease with the increase of frequency. ε' decreases from 17.5 at 2 GHz to 8.5 at 18 GHz. ε” decreases from 9.7 at 2 GHz to 1.0 at 18 GHz.

[0077] As Figure 6 shown, it is the tangent value of the imaginary part of the permittivity (ε”) and the real part of the permittivity (ε') of the silver-loaded molybdenum carbide composite microwave absorption material. The tanδ value shows an overall downward trend with slight fluctuations at 9 and 15 GHz, indicating that the silver-loaded molybdenum carbide composite microwave absorption material has good absorption performance in the low-frequency band.

[0078] It can be found from the above figures that the silver-loaded molybdenum carbide composite microwave absorption material prepared by the present invention through the method of photoinduced self-reduction, compared with the traditional method of doping magnetic metals by high-temperature sintering, not only has no environmental pollution, but also has simple operation and is suitable for large-scale industrial production. And it is a non-magnetic metal silver, still showing excellent microwave absorption performance. When the frequency is 17.6 GHz and the thickness is 1.5 mm, the minimum RL value is -45 dB.

Claims

1. A method for preparing silver-loaded molybdenum carbide composite microwave absorption materials by photo-induced self-reduction, characterized in that, The specific operation steps are as follows: Step 1: Mix molybdate, 4-chloro-o-phenylenediamine, and deionized water and stir evenly. Add acid to adjust the pH value of the mixed solution. Place the mixed solution in an oil bath and heat and stir it at a constant temperature. After naturally cooling to room temperature, centrifuge and dry to obtain a khaki solid powder A; Step 2: Place the solid powder A in a tube furnace and carry out calcination carbonization in a nitrogen atmosphere to obtain a black powder B; Step 3: Add the black powder B to silver nitrate solutions with different concentrations and ultrasonically mix them evenly to obtain a mixed solution C; Step 4: Under the irradiation of an ultraviolet lamp, the in-situ reduction of photo-induced silver nanoparticles is realized under the condition of no reducing agent in the mixed solution C to form a silver-loaded molybdenum carbide composite microwave absorbing material; Step 5: Mix the silver-loaded molybdenum carbide composite microwave absorbing material with paraffin and carbon nanotubes, and then press them into a ring-shaped sample for microwave absorption performance testing.

2. The method for preparing the silver-loaded molybdenum carbide composite microwave absorption material by photo-induced self-reduction according to claim 1, characterized in that, In Step 1, the mass ratio of molybdate to 4-chloro-o-phenylenediamine is 1:2-3.

3. The method for preparing the silver-loaded molybdenum carbide composite microwave absorption material by photo-induced self-reduction according to claim 1, wherein In Step 1, the pH value is adjusted to 1-3, and perchloric acid is used to adjust the mixed solution.

4. The method for preparing the silver-loaded molybdenum carbide composite microwave absorption material by photoinduced self-reduction according to claim 1, wherein, In Step 1, the oil bath temperature can be controlled at 30-60 °C, and the oil bath time is controlled at 1.5-3 h.

5. The method for preparing the silver-loaded molybdenum carbide composite wave-absorbing material by photo-induced self-reduction according to claim 1, characterized in that, In Step 2, the heating rate of the tube furnace can be 70-120 °C / h, and the heat preservation time can be 8 h-16 h.

6. The method for preparing the silver-loaded molybdenum carbide composite microwave absorbing material by photoinduced self-reduction according to claim 1, wherein, In Step 3, the ultrasonic time is 30-60 min.

7. The method for preparing the silver-loaded molybdenum carbide composite microwave absorbing material by photoinduced self-reduction according to claim 1, wherein In Step 3, the concentration of the silver nitrate solution is 9-11 mmol / L.

8. A silver-loaded molybdenum carbide composite microwave absorbing material prepared by the method for photo-induced self-reduction preparation of a silver-loaded molybdenum carbide composite microwave absorbing material according to any one of claims 1-7.

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