A MoS2 / Ti2CT x MXene composite microwave absorbing material and its preparation method

Abstract

The present invention belongs to the field of microwave absorbing materials, and specifically discloses a MoS2 / Ti2CT x MXene composite microwave absorbing material and a preparation method thereof. The method is as follows: Dissolve Ti2CTx MXene, ammonium molybdate and thiourea in polyethylene glycol, mix well to obtain a mixed solution, heat the mixed solution to 190 °C to 240 °C, cool to room temperature after the reaction ends, and wash and dry the reaction product to obtain MoS2 / Ti2CT x MXene composite microwave absorbing material. The present invention takes Ti2CT x MXene as the main body, adds Ti2CT x to the precursor of MoS2, and loads molybdenum sulfide onto the Ti2CTx matrix through microwave solvothermal method to obtain a novel MoS2 / Ti2CTx MXene composite microwave absorbing material. The present invention provides a new preparation method for MoS2 / MXene nanocomposites, and solves the problems of long preparation period, limited yield and easy oxidation of raw materials in the hydrothermal method.

Description

Technical Field

[0001] The present invention belongs to the field of microwave absorption materials, and particularly relates to a MoS2 / Ti2CT x MXene composite microwave absorption material and a preparation method thereof. Background Art

[0002] With the advent of the 5G era, the problem of electromagnetic interference has become increasingly serious, posing higher requirements for electromagnetic shielding materials. Materials with higher shielding efficiency, wider coverage, light weight, and stable performance are needed. MXene is a material with a graphene-like structure. Due to its unique properties, it has great research value in energy storage, adsorption, catalysis, optoelectronic conversion, sensors, and electromagnetic shielding. In particular, the high conductivity (up to 2×10 4 S / cm) and layered structure of MXene make it a very promising candidate material for electromagnetic shielding. On the other hand, transition metal sulfides represented by MoS2 have special energy band structures (when molybdenum disulfide changes from bulk to monolayer, the energy band structure changes from indirect bandgap to direct bandgap, and the bandgap width is about 1.9 eV), excellent mechanical properties, etc., and have broad application prospects in many fields such as nanoelectronic devices and optoelectronics. By compounding MoS2 with MXene materials, the microwave absorption performance of MXene materials can be improved.

[0003] Due to advantages such as a relatively low reaction temperature, easy process control, wide applicability, relatively inexpensive and easily available raw materials, and special morphologies of products, the hydrothermal method has been widely used in the preparation of MoS2 / MXene nanocomposites. However, there are still problems in the preparation of MoS2 / MXene composites by the hydrothermal method, such as a long preparation cycle, limited yield, and the easy oxidation of MXene in a hydrothermal environment. Summary of the Invention

[0004] Aiming at the problems and deficiencies in the prior art, the purpose of the present invention is to provide a MoS2 / Ti2CT x MXene composite microwave absorption material and a preparation method thereof.

[0005] To achieve the purpose of the invention, the technical scheme adopted by the present invention is as follows:

[0006] The present invention provides a preparation method of a MoS2 / Ti2CT x MXene composite microwave absorption material, and the method is: dissolving Ti2CT x MXene, ammonium molybdate, and thiourea in polyethylene glycol, mixing evenly to obtain a mixed solution, heating the mixed solution to 190°C to 240°C, cooling to room temperature after the reaction ends, and washing and drying the reaction product to obtain the MoS2 / Ti2CT x MXene composite microwave absorption material.

[0007] According to the described preparation method, preferably, the molecular weight of the polyethylene glycol is 200 to 400.

[0008] According to the described preparation method, preferably, the Ti2CT x The mass ratio of MXene to ammonium molybdate is 1:8 to 12, and the Ti2CT x The mass ratio of MXene to thiourea is 1:15 to 30.

[0009] According to the described preparation method, preferably, the heating method is microwave heating.

[0010] According to the described preparation method, preferably, the heating time is 20 to 40 min.

[0011] According to the described preparation method, preferably, the heating rate during the heating process is 80 to 100 °C / min.

[0012] According to the described preparation method, preferably, the washing is to wash the product with ethanol.

[0013] According to the described preparation method, preferably, the Ti2CT x MXene is prepared by adding Ti2AlC powder to a mixed solution of LiF and hydrochloric acid and heating.

[0014] The second aspect of the present invention provides a MoS2 / Ti2CT prepared by the first aspect x MXene composite absorbing material.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The traditional hydrothermal method uses water as a solvent when preparing the MoS2 / MXene nanocomposite. When the heating temperature exceeds 100 °C, the reaction solution boils easily and the reactants are oxidized. The present invention provides a new preparation method for the MoS2 / MXene nanocomposite. This method selects polyethylene glycol as the solvent, and the heating temperature of 190 °C to 240 °C is still lower than the boiling point of the reaction solution, solving the problem of easy oxidation of MXene in the traditional hydrothermal method. At the same time, by heating the system with a microwave reaction device, the shorter reaction time also greatly reduces the possibility of oxidation of Ti2CT x MXene.

[0017] (2) The present invention uses Ti2CT x MXene as the main body, adds Ti2CT x to the precursor of MoS2, and loads molybdenum sulfide onto Ti2CT xOn the substrate, a new type of MoS2 / Ti2CT x MXene composite microwave absorbing material is obtained. After microwave solvothermal compounding, the Ti2CT in the composite x still maintains a multi-layer flaky structure, and MoS2 grows uniformly on the flakes of Ti2CT x , and Ti2CT x and MoS2 cooperate to absorb the incident microwave.

[0018] (3) The MoS2 / Ti2CT x MXene composite microwave absorbing material prepared by the present invention has good microwave absorption performance, and its RL min is as low as -53.26 dB at minimum, and the effective bandwidth is within 2.0 - 4.50 GHz. Description of the Drawings

[0019] Figure 1 are the XRD diagrams of the materials prepared in Comparative Examples 1 - 3 and Examples 1 - 3;

[0020] Figure 2 is the detailed XRD diagram of the MoS2 / Ti2CT x composite microwave absorbing material prepared in Example 2;

[0021] Figure 3 are the SEM diagrams of the materials prepared in Comparative Example 1, Comparative Example 3 and Examples 1 - 3;

[0022] Figure 4 are the impedance matching contour diagrams of the materials prepared in Comparative Examples 1, 2 and Examples 1 - 3;

[0023] Figure 5 are the three-dimensional reflection loss diagram and two-dimensional reflection loss contour diagram of the Ti2CT x material prepared in Comparative Example 1;

[0024] Figure 6 are the three-dimensional reflection loss diagram and two-dimensional reflection loss contour diagram of the MoS2 / Ti2CT x material prepared in Comparative Example 2;

[0025] Figure 7 are the three-dimensional reflection loss diagram and two-dimensional reflection loss contour diagram of the MoS2 / Ti2CT x composite microwave absorbing material prepared in Example 1;

[0026] Figure 8 are the three-dimensional reflection loss diagram and two-dimensional reflection loss contour diagram of the MoS2 / Ti2CT x composite microwave absorbing material prepared in Example 2;

[0027] Figure 9The MoS2 / Ti2CT prepared in Example 3 x Three-dimensional reflection loss diagram and two-dimensional reflection loss contour map of the composite wave-absorbing material. Specific implementation mode

[0028] The following examples are only applicable to further illustrate the present invention. It should be noted that all technologies and scientific terms used in the present invention have the same meaning as those in the technical field to which the present invention belongs unless otherwise specified. The experimental methods without specific conditions indicated in the following examples are all conventional techniques in the technical field or are carried out according to the conditions recommended by the manufacturer; reagents or instruments without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0029] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific examples.

[0030] Example 1

[0031] (1) Preparation of Ti2CT x :

[0032] Measure 50 mL of 8 mol / L hydrochloric acid into a beaker, add 2.5 g of LiF powder to it, and mix evenly to obtain an etching solution. Slowly add 2 g of Ti2AlC powder to the etching solution, stir magnetically at 40 °C for 48 h. After the reaction, wash the precipitate successively with deionized water, dilute hydrochloric acid and absolute ethanol by high-speed centrifugation, and dry the precipitate to obtain black Ti2CT x powder.

[0033] (2) Preparation of MoS2 / Ti2CT x :

[0034] Weigh 0.1000 g of Ti2CT x powder, 0.6618 g of ammonium molybdate tetrahydrate and 1.4266 g of thiourea, dissolve them in 150 mL of polyethylene glycol (molecular weight 200), stir until evenly mixed, add the mixed solution into a three-necked flask, and place the flask in a microwave reactor. Heat the microwave reactor to 200 °C at a rate of 100 °C / min and keep it warm for 30 min. After the reaction, wash the product by centrifugation with ethanol, and then vacuum-dry the product at 60 °C for 12 h to obtain MoS2 / Ti2CT x composite wave-absorbing material.

[0035] Example 2

[0036] Weigh 0.1000 g of Ti2CT obtained in step (1) of Example 1 x0.8824 g of ammonium molybdate tetrahydrate and 1.9020 g of thiourea were dissolved in 150 mL of polyethylene glycol (molecular weight 200), and stirred until evenly mixed. The mixed solution was placed in a three-necked flask, and the flask was placed in a microwave reactor. The microwave reactor was heated to 200 °C at a rate of 100 °C / min and held for 30 min. After the reaction, the product was centrifugally washed with ethanol, and then the product was vacuum dried at 60 °C for 12 h to obtain MoS2 / Ti2CT x composite microwave absorbing material.

[0037] Example 3

[0038] Weigh 0.1000 g of Ti2CT obtained in step (1) of Example 1 x powder, 1.1030 g of ammonium molybdate tetrahydrate and 2.3775 g of thiourea were dissolved in 150 mL of polyethylene glycol (molecular weight 200), and stirred until evenly mixed. The mixed solution was placed in a three-necked flask, and the flask was placed in a microwave reactor. The microwave reactor was heated to 200 °C at a rate of 100 °C / min and held for 30 min. After the reaction, the product was centrifugally washed with ethanol, and then the product was vacuum dried at 60 °C for 12 h to obtain MoS2 / Ti2CT x composite microwave absorbing material.

[0039] Example 4

[0040] Weigh 0.2000 g of Ti2CT obtained in step (1) of Example 1 x powder, 0.2206 g of ammonium molybdate tetrahydrate and 0.4755 g of thiourea were dissolved in 150 mL of polyethylene glycol (molecular weight 200), and stirred until evenly mixed. The mixed solution was placed in a three-necked flask, and the flask was placed in a microwave reactor. The microwave reactor was heated to 200 °C at a rate of 100 °C / min and held for 30 min. After the reaction, the product was centrifugally washed with ethanol, and then the product was vacuum dried at 60 °C for 12 h.

[0041] Finally, the experimental product obtained was very little and difficult to collect. And it was a light brown powder, which did not match the color of typical black MoS2 and black Ti2CT x Under this ratio, too little molybdenum disulfide was generated, and it was difficult to synthesize the ideal MoS2 / Ti2CT x material.

[0042] Comparative Example 1

[0043] Step (1) in Example 1 was used as Comparative Example 1.

[0044] Comparative Example 2 (traditional hydrothermal method)

[0045] Weigh 0.2000 g of Ti2CT obtained in step (1) of Example 1x , 0.2206 g of ammonium molybdate tetrahydrate and 0.4755 g of thiourea were dissolved in 50 mL of deionized water, stirred until evenly mixed, the mixed solution was placed in a polytetrafluoroethylene reaction kettle, and the reaction kettle was placed in an oven at 200 °C for 18 h. The product after the hydrothermal reaction was washed successively with deionized water and ethanol, and vacuum dried at 60 °C for 12 h to obtain MoS2 / Ti2CT x .

[0046] Comparative Example 3 (traditional hydrothermal method)

[0047] Weighed 0.1000 g of the Ti2CT x powder obtained in step (1) of Example 1, 0.8824 g of ammonium molybdate tetrahydrate and 1.9020 g of thiourea were dissolved in 50 mL of deionized water, stirred until evenly mixed, the mixed solution was placed in a polytetrafluoroethylene reaction kettle, and the reaction kettle was placed in an oven at 200 °C for 18 h. The product after the hydrothermal reaction was washed successively with deionized water and ethanol, and vacuum dried at 60 °C for 12 h to obtain MoS2 / Ti2CT x .

[0048] The MoS2 / Ti2CT x MXene composite absorbing material prepared by the present invention

[0049] 1. X-ray diffraction

[0050] The materials prepared by the present invention were subjected to X-ray diffraction. The XRD of the materials obtained in Comparative Examples 1, 2, 3 and Examples 1, 2, 3 are as Figure 1 shown. The detailed XRD pattern of the MoS2 / Ti2CT x composite absorbing material obtained in Example 2 is as Figure 2 shown.

[0051] It can be seen from Figure 1 that taking the XRD spectrum of Comparative Example 2 as an example, the peaks at 2θ = 14.3°, 32.8° and 58.5° correspond to the (002), (102) and (110) crystal planes of MoS2 (PDF#37-1492) respectively, indicating that MoS2 has been successfully prepared by the hydrothermal method of the present invention. However, these diffraction peaks are broadened and have low intensity, indicating that the MoS2 prepared by the hydrothermal method has poor crystallinity. The characteristic peak at 2θ = 18.1° corresponds to the (111) crystal plane of Ti2CT x , but the characteristic peak of Ti2CT x at 7.65° disappears, and characteristic peaks of TiO2 appear at 2θ = 25.3°, 38.5°, 48.1°, 54.5° and 62.6°. The same situation also occurs in Comparative Example 3. This is because during the traditional hydrothermal reaction process, Ti2CTx It is extremely easy to oxidize, and most of the Ti2CT x has been oxidized, thus introducing the TiO2 phase.

[0052] It can be found by comparing with the spectral lines of Comparative Example 2 that Figure 1 Examples 1 to 3 in it have diffraction peaks of Ti2CT at 7.02° (002) and 18.1° (111). x Compared with the position of the main peak (002) in pure Ti2CT of Comparative Example 1, x for the MoS2 / Ti2CT x composite materials synthesized in Examples 1 to 3, the position of the (002) peak significantly shifts to a smaller angle, indicating that the introduction of MoS2 increases the interlayer spacing of Ti2CT. x No characteristic peak of TiO2 appears in the spectral lines of Examples 1 to 3, indicating that the microwave solvothermal method effectively prevents the oxidation of Ti2CT during the reaction x to TiO2, solving the problem of easy oxidation in the traditional hydrothermal method. In addition, both Comparative Example 2 and Examples 1 to 3 have a diffraction peak at 9.3°. This diffraction peak corresponds to the (002) crystal plane of partially intercalated MoS2. This is because after the sulfur source concentration increases, more thiourea molecules are inserted into the interlayer of MoS2, making the interlayer spacing larger and the diffraction peak shift to a smaller angle.

[0053] 2. Scanning electron microscope (SEM) test

[0054] The Ti2CT prepared in Comparative Example 1 of the present invention x , the MoS2 / Ti2CT prepared in Comparative Example 3 x and the MoS2 / Ti2CT prepared in Examples 1, 2, and 3 x materials are tested by a scanning electron microscope. See the SEM images in Figure 3 , where (a), (b), (c), (d), and (e) correspond to Comparative Example 1, Comparative Example 3, Example 1, Example 2, and Example 3 in sequence.

[0055] It can be seen from Figure 3 that in (a), for Ti2CT x (Comparative Example 1), since the Al layer is etched away and the interlayer is opened, it shows a typical accordion structure. In (b), for the composite material, due to excessive loading of MoS2, the interlayer spacing shrinks and the layered structure is damaged, which is not conducive to the wave absorption performance of the material. While in (c), (d), and (e), the layered structure of Ti2CT x is relatively complete, indicating that the microwave solvothermal method and the proportion of each substance provided by the present invention are more conducive to the intercalation of MoS2 in Ti2CT xGrowth on the substrate. Among them, due to the relatively large amount of MoS2 loaded in the material obtained in Example 3, MoS2 agglomerates between layers while growing on the Ti2CT x substrate, while the amount of MoS2 loaded in the materials obtained in Example 1 and Example 2 is relatively small, and MoS2 can grow evenly on the surface and between layers of the Ti2CT x substrate. And as the loading amount of MoS2 decreases, the flakes that were originally thickened due to the attachment of a large amount of MoS2 gradually become thinner, and the layered structure becomes clearer. Therefore, within a certain range of MoS2 loading amount, the layered structure of the MoS2 / Ti2CT x material prepared by the present invention is more complete and clear.

[0056] 3. Microwave absorption property test

[0057] The MoS2 / Ti2CT x materials prepared in Examples 1, 2, and 3 of the present invention and the materials prepared in Comparative Examples 1 and 2 were tested for microwave absorption properties. The specific test method is as follows: The test sample was mixed with paraffin in a ratio of 7:3 (i.e., a sample filling ratio of 70 wt%), and pressed into a coaxial ring with an inner ring diameter of 3 mm and an outer ring diameter of 7 mm. The electromagnetic parameters (permeability and complex permittivity) of the material were measured with a vector network analyzer, and the test frequency range was: 2 - 18 GHz. The impedance matching and reflection loss values of the material can be obtained by calculating the electromagnetic parameters.

[0058] 3.1 Impedance matching

[0059] The impedance matching contour lines of each sample are as Figure 4 shown, where (a), (b), (c), (d), and (e) are Comparative Example 1, Comparative Example 2, Example 1, Example 2, and Example 3 in sequence.

[0060] The microwave absorption material needs to have good impedance (Z) matching, which is beneficial to the entry of electromagnetic waves into the material interior. The closer the impedance of the material is to the impedance of free space (i.e., Z = 1), the better the impedance matching. As can be seen from Figure 4 (a), the yellow area of pure-phase Ti2CT x is less, and the impedance matching is poor. This is because the conductivity of the Ti2CT x material is relatively high, resulting in partial reflection of electromagnetic waves after reaching the material surface. Figure 4 (b) - (e) are the impedance matching diagrams of the materials obtained after the combination of Ti2CT x and MoS2. It can be seen that the yellow area of the composite material is significantly more than that of the Ti2CT x material, indicating that the Ti2CT xThe synergistic effect between [substance] and MoS2 can improve the impedance matching of the composite, making it easier for electromagnetic waves to enter the interior of the material. This is because MoS2 is a low-dielectric phase, and the greater its content, the better the impedance matching of the composite material. Therefore, the MoS2 / Ti2CT prepared by the microwave solvothermal method in this invention x The composite material has good impedance matching and wave absorption ability.

[0061] 3.2 Reflection Loss

[0062] The three-dimensional reflection loss diagrams and reflection loss contour lines of each sample are as Figures 5 - 9 shown, Figure 5 where (a1) and (a2) are the three-dimensional reflection loss diagram and reflection loss contour line diagram of the Ti2CT x sample prepared in Comparative Example 1 in sequence, Figure 6 where (b1) and (b2) are the three-dimensional reflection loss diagram and reflection loss contour line diagram of the MoS2 / Ti2CT x sample prepared in Comparative Example 2 in sequence, Figure 7 where (c1) and (c2) are the three-dimensional reflection loss diagram and reflection loss contour line diagram of the MoS2 / Ti2CT x sample prepared in Example 1 in sequence, Figure 8 where (d1) and (d2) are the three-dimensional reflection loss diagram and reflection loss contour line diagram of the MoS2 / Ti2CT x sample prepared in Example 2 in sequence, Figure 9 where (e1) and (e2) are the three-dimensional reflection loss diagram and reflection loss contour line diagram of the MoS2 / Ti2CT x sample prepared in Example 3 in sequence.

[0063] The microwave absorption ability of any wave-absorbing material has a great relationship with the minimum reflection loss value, the thickness of the material, and the effective bandwidth. If the wave-absorbing material produces an RL value less than -10 dB, it indicates that up to 90% of the microwave is consumed, and the material can be predicted as an ideal wave-absorbing material.

[0064] It can be intuitively seen from Figures 5 - 9 that the MoS2 / Ti2CT Figure 8 composite material synthesized in Example 2 ( x ) has the smallest reflection loss value. The minimum reflection loss values of the five materials and their corresponding thicknesses, frequencies, and effective bandwidths are listed and compared in Table 1 as follows.

[0065] Table 1 Minimum reflection loss values of materials in Comparative Examples 1 and 2 and Examples 1 - 3 and their corresponding thicknesses, frequencies, and effective bandwidths

[0066] Group Filling ratio <![CDATA[RL min / dB]]> Frequency / GHz Thickness / mm Effective bandwidth / GHz Comparative example 1 70wt% -39.45 12.57 1.41 2.1 Comparative example 2 70wt% -26.12 4.96 4.98 2.98 Example 1 70wt% -15.66 17.82 1.92 0.87 Example 2 70wt% -53.26 14.50 3.14 4.11 Example 3 70wt% -14.94 11.61 3.4 2.48

[0067] As can be seen from Table 1, for the composite materials prepared by the microwave solvothermal method in the present invention, with the decrease of the MoS2 loading amount (the MoS2 loading amount gradually decreases in Examples 3, 2, and 1), RL min first decreases and then increases and is less than -10 dB in all cases, indicating that the MoS2 / Ti2CT x composite materials prepared in the present invention consume up to 90% of microwaves, and this material is an ideal microwave absorbing material.

[0068] Among them, the RL of the composite material prepared in Example 2 of the present invention min is less than that of the pure-phase Ti2CT in Comparative Example 1 x and the RL of the composite material prepared by the traditional hydrothermal method in Comparative Example 2 min . This is because the combination of MoS2 and Ti2CT x can effectively reduce the extreme value of reflection loss, but a small amount of MoS2 cannot effectively improve impedance matching, and an excessive amount of MoS2 causes agglomerated MoS2 between the Ti2CT x layers, which is not conducive to improving the microwave absorption performance of the material. Comparing Figure 5 (a2), Figure 6 (b2), Figure 7 (c2), Figure 8 (d2) and Figure 9 (e2), it can be clearly seen that the effective bandwidth (EAB) of the material prepared in Example 2 at different thicknesses is greater than that of the pure-phase Ti2CT in Comparative Example 1 x , and the EAB of the material in Example 2 is the widest at higher frequencies. Therefore, the MoS2 / Ti2CT x composite microwave absorbing material prepared by the microwave solvothermal method provided by the present invention has a relatively wide effective bandwidth.

[0069] New microwave absorbing materials need to meet the characteristics of "thin thickness, strong performance, light weight, wide bandwidth", etc. The present invention selects the lighter Ti2CT x as the matrix, and allows MoS2 to grow in-situ on the Ti2CT x matrix through the microwave solvothermal method. This composite material exhibits the synergistic effect of the two-dimensional heterostructure interface and the double dielectric components, enhancing the microwave absorption effect. It can be seen from the experimental results that the MoS2 / Ti2CT x samples prepared in the present invention have excellent microwave absorption performance, and among them, the microwave absorption performance of the MoS2 / Ti2CT x samples prepared in Example 2 exceeds that of most reported MXene-based and MoS2-based materials. Therefore, the present invention provides a new preparation method for MoS2 / MXene nanocomposites, solving the problems of long preparation cycle, limited yield, and easy oxidation of raw materials in the hydrothermal method.

[0070] The above embodiments are specific embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other combinations, changes, modifications, substitutions, and simplifications that do not exceed the design concept of the present invention fall within the protection scope of the present invention.

Claims

1. A preparation method of MoS2 / Ti2CT x MXene composite microwave absorbing material, characterized in that, Dissolve Ti2CT x MXene, ammonium molybdate and thiourea in polyethylene glycol, mix well to obtain a mixed solution, microwave heat the mixed solution to 190 °C - 240 °C, cool to room temperature after the reaction ends, and the reaction product is washed and dried to obtain MoS2 / Ti2CT x MXene composite microwave absorption material; the Ti2CT x The mass ratio of MXene to ammonium molybdate is 1:8 - 12, and the Ti2CT x The mass ratio of MXene to thiourea is 1:15 - 30.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the polyethylene glycol is 200 to 400.

3. The preparation method according to claim 2, wherein The heating time is 20 to 40 min.

4. The preparation method according to claim 3, characterized in that, The heating rate during the heating process is 80 to 100 °C / min.

5. The preparation method according to claim 4, characterized in that, The washing is to wash the product with ethanol.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The Ti2CT x MXene is prepared by heating Ti2AlC powder in a mixed solution of LiF and hydrochloric acid.

7. MoS2 / Ti2CT MXene composite microwave absorption material prepared by the method according to any one of claims 1 to 6 x ​

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