SiAlON / C nanowire composite material with electromagnetic absorption and mechanical toughening functions and preparation method of SiAlON / C nanowire composite material

Abstract

The invention discloses a SiAlON / C nanowire composite material with electromagnetic absorption and mechanical toughening functions and a preparation method of the SiAlON / C nanowire composite material, and belongs to the technical field of nanocomposite materials. The preparation method comprises the steps of ball milling, high-pressure sintering, ultrasonic dispersion and drying; the step of ball milling comprises the following steps: mixing Si3N4 and aluminum powder, adding water, and carrying out ball milling and drying; the step of high-pressure sintering comprises the following steps: mixing the dried ball-milled product with graphene in a crucible, then putting the crucible into a tubular furnace, carrying out high-pressure sintering, and unsealing the crucible. The SiAlON / C nanowire composite material is obtained by doping graphene into preparation of beta-SiAlON nanowires, the graphene serves as a carbon source, and the adding amount of the graphene can be adjusted according to experimental requirements to control the thickness of a carbon layer and generation of a SiC intermediate layer at an interface, so that the composite material with excellent electromagnetic wave absorption performance is obtained.

Description

Technical field: The present invention relates to the technical field of nanocomposite materials, and in particular to a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions and a preparation method thereof. Background technology: With advances in automation and information technology, electronic equipment is becoming increasingly prevalent in the aerospace sector. The resulting electromagnetic pollution has a significant adverse effect on the stable operation of precision instruments. To address this issue, researchers have explored various materials that enhance electromagnetic wave absorption. However, current research on microwave-absorbing materials primarily focuses on powders and nanoparticles, which lack sufficient mechanical strength, limiting their application in complex environments.

[0001] SiAlON ceramics are a type of solid solution formed by replacing Si and N atoms in Si3N4 with Al and O atoms, which has excellent mechanical properties and chemical stability. The classification of SiAlON ceramics includes α-SiAlON, β-SiAlON and O'-SiAlON, among which β-SiAlON (Si 6-z Al z O z N 8-z , 0 ≤ z ≤ 4.2) has great potential for application in electromagnetic wave absorption due to its excellent mechanical properties, electromagnetic wave transmission capabilities, and compatibility with various materials. Notably, SiAlON ceramics, in addition to their normal bulk morphology, can also be grown into nanowires under specific conditions. Existing research has demonstrated that nanowire-like SiAlON ceramics exhibit excellent toughening properties.

[0002] Previous research has shown that microwave-transmitting ceramics can effectively optimize the dielectric constant and impedance matching of composite materials, thereby producing high-performance microwave absorbing materials. However, due to its limited dielectric properties, SiAlON ceramics are often used as microwave-transmitting ceramics and rarely used in microwave absorption applications. Therefore, we propose a new synthesis method for composite materials composed of SiAlON nanowires and carbon. This method aims to synergistically enhance the material's microwave absorption performance and mechanical toughness. Summary of the invention: The present invention provides a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions and a preparation method thereof. The SiAlON / C nanowire composite material is obtained by incorporating graphene into the preparation of β-SiAlON nanowires. The graphene is used as a carbon source, and its addition amount can be adjusted according to experimental requirements to control the thickness of the carbon layer, thereby obtaining a composite material with excellent electromagnetic wave absorption performance.

[0003] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions, comprising: ball milling, high-pressure sintering, ultrasonic dispersion, and drying; The ball milling comprises mixing Si3N4 and aluminum powder, adding water, ball milling, and drying to obtain a dry ball milled product; In the ball milling, the ratio of Si3N4 to aluminum powder is 14-16g:7.5-8.5g; The ratio of Si3N4 to water is 14-16g:140-160mL; The ball milling speed is 250-300 rpm and the time is 3-4 hours; Si3N4 is β phase with a particle size of 1-3μm; The high-pressure sintering comprises mixing the dried ball-milled product with graphene in a crucible, placing the crucible in a tube furnace, performing high-pressure sintering, and unsealing the crucible to obtain a crude SiAlON / C nanowire product; The ratio of Si3N4 in the ball milling to graphene in the high pressure sintering is 14-16g:9-11g; The graphene has a model of AP-3 and a d50 of 4-6 μm; During the high-pressure sintering, the temperature during the high-pressure sintering is 1800-1900° C. and the pressure is 10-15 MPa; The high pressure sintering is carried out in a nitrogen atmosphere; The high pressure sintering time is 2-3 hours; The ultrasonic dispersion is performed by placing the SiAlON / C nanowire crude product in the crucible into deionized water, adding a coupling agent, and performing ultrasonic dispersion treatment to obtain a suspension; The ratio of Si3N4 in the ball mill to deionized water in the ultrasonic dispersion is 14-16 g:80-100 mL; The ratio of Si3N4 in the ball mill to the coupling agent in the ultrasonic dispersion is 14-16g:0.9-1.2g; In the ultrasonic dispersion, the coupling agent is KH-450 coupling agent; The ultrasonic dispersion treatment time is 1-2h; The drying step comprises centrifuging the suspension and then allowing the suspension to stand for stratification, taking the upper suspension layer, and drying the upper suspension layer to obtain a SiAlON / C nanowire composite material; During the drying process, the centrifugal speed is 8000-10000 rpm and the time is 30-40 min; When taking the upper suspension, accurately extract the upper suspension using a pipette.

[0004] A SiAlON / C nanowire composite material prepared by the above-mentioned preparation method.

[0005] The beneficial technical effects of the present invention are as follows: (1) The present invention innovates the traditional SiAlON nanowire synthesis method and adds graphene as a carbon source during the synthesis process. A SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening effects is synthesized at high temperature. The addition of the carbon source does not damage the nanowire morphology of SiAlON, but instead enables the carbon layer to be effectively bonded to the surface of the SiAlON nanowire and forms a SiC intermediate interface between the carbon layer and SiAlON.

[0006] (2) The structure of the SiAlON / C nanowire composite material of the present invention is a composite material obtained by coating a carbon layer on the surface of SiAlON nanowires layer by layer. The composite material is composed of nanocrystals, amorphous phases and carbon layers. The interfaces of these heterogeneous nanostructures jointly contribute to the conductivity of the material and synergistically amplify the polarization loss and dipole polarization effect. In addition, the difference in conductivity between the carbon layer, the SiC intermediate layer and the SiAlON substrate will cause a dielectric constant mismatch. This mismatch induces electron rearrangement at the interface, thereby enhancing carrier transport and strengthening the interface polarization effect and conductivity loss, further improving the material's absorption performance.

[0007] (3) The SiAlON / C nanowire composite material of the present invention still retains the basic structure of SiAlON nanowires. Therefore, when forming a composite absorbing device with a matrix such as rubber or resin, the SiAlON / C nanowire composite material can dissipate the fracture energy through the bridging, pulling out and fracture process of the nanowires near the crack propagation zone, thereby inhibiting crack propagation and reducing the degree of fracture. This means that SiAlON / C nanowires will have excellent performance in improving the fracture strength and toughness of the device, highlighting the unique value of SiAlON / C nanowire materials in the field of mechanical strengthening. Moreover, the present invention achieves the synergistic enhancement of microwave loss and mechanical toughness of ceramic nanowires by constructing a C / SiC / SiAlON gradient interface structure on SiAlON nanowires, establishing a new paradigm for multifunctional absorbing materials. These findings provide valuable insights for advanced applications in the fields of aerospace and precision electronics, and demonstrate the great potential for the development of structural and functional integrated materials. Description of the drawings: Figure 1 1 is a transmission electron microscope (TEM) image and an energy dispersive elemental analysis (EDS) distribution diagram of the SiAlON / C nanowire composite material prepared in Example 2; in, Figure 1 a is the TEM image of SiAlON / C nanowire composite material; Figure 1 b is the EDS image of carbon element; Figure 1c is the EDS image of silicon element; Figure 1 d is the EDS image of aluminum element; Figure 1 e is the EDS image of nitrogen; Figure 1 f is the EDS image of oxygen element.

[0008] Figure 2 Schematic diagram of the microwave absorption performance of the SiAlON / C nanowire composite material prepared in Examples 1-3; in, Figure 2 a and Figure 2 d is a schematic diagram of the wave absorbing performance of Example 1, Figure 2 b and Figure 2 e is a schematic diagram of the wave absorbing performance of Example 2, Figure 2 c and Figure 2 f is a schematic diagram of the wave absorbing performance of Example 3.

[0009] Figure 3 Graphs showing the mechanical properties of the mechanical test samples in Example 2 and Comparative Example 3; In the figure, Figure 3 a is a schematic diagram of the tensile test of SiAlON / C nanowire toughened device. Figure 3 b is a schematic diagram of the toughening mechanism of SiAlON / C nanowires. Figure 3 c is the stress-strain curve of the mechanical test samples in Example 2 and Comparative Example 3 under tensile test. Specific implementation method: Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0010] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0011] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0012] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0013] The raw materials used in the following examples and comparative examples of the present invention are all commercially available products. For detailed information, please refer to the following table: Table 1 Raw materials used

[0014] Example 1 A method for preparing a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions, specifically comprising: (1) 15 g Si3N4 and 8 g aluminum powder were mixed in a ball mill jar, 150 mL water was added, and the mixture was ball milled at 290 rpm for 3 h. The product was then taken out and dried in an oven.

[0015] (2) The dried ball-milled product was mixed with 10 g of graphene in a crucible. The crucible was then placed in a tube furnace and sintered at 1800°C in a nitrogen atmosphere at 10 MPa. After sintering for 2 hours, the crucible was unsealed to obtain a crude SiAlON / C nanowire product.

[0016] (3) The crude SiAlON / C nanowire product in the crucible was placed in 80 mL of deionized water, 1 g of KH-450 coupling agent was added to adjust the viscosity of the water-based slurry, and then ultrasonic dispersion treatment was performed for 1 h.

[0017] (4) After the ultrasonic dispersion treatment is completed, the suspension is centrifuged for 30 minutes and allowed to stand for stratification. The centrifugal speed is 8000 rpm. After the upper layer of the suspension is accurately extracted by a pipette, the purified SiAlON / C nanowires are obtained by an oven drying process.

[0018] This embodiment also provides a SiAlON / C nanowire composite material prepared by the aforementioned preparation method.

[0019] The SiAlON / C nanowire composite material of this embodiment was used to prepare a mechanical test sample, and the preparation method was as follows: (1) Mix 10 g of SiAlON / C nanowire material with 90 g of silicone rubber, add 1.5 wt.% of ethyl orthosilicate as a curing agent, and stir for 10 minutes to obtain a mixed slurry; (2) Pour the mixed slurry into a standard mold for mechanical testing and then place it in a vacuum machine for degassing to reduce internal porosity; (3) Place in an oven at 80°C and dry for 3 hours to obtain a mechanical test sample.

[0020] Example 2 A method for preparing a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions, specifically comprising: (1) 15 g Si3N4 and 8 g aluminum powder were mixed in a ball mill jar, 150 mL water was added, and the mixture was ball milled at 290 rpm for 3 h. The product was then taken out and dried in an oven.

[0021] (2) The dried ball-milled product was mixed with 15 g of graphene in a crucible. The crucible was then placed in a tube furnace and sintered at 1800°C in a nitrogen atmosphere at 10 MPa. After sintering for 2 hours, the crucible was unsealed to obtain a crude SiAlON / C nanowire product.

[0022] (3) The SiAlON / C nanowire crude product in the crucible was placed in 80 mL of deionized water, 1 g of KH-450 coupling agent was added to adjust the viscosity of the water-based slurry, and then ultrasonic dispersion treatment was performed for 1 h.

[0023] (4) After ultrasonic dispersion, the suspension was centrifuged for 30 min and allowed to stand for stratification. The centrifugal speed was 8000 rpm. The upper layer of suspension was accurately extracted by a pipette and then oven-dried to obtain purified SiAlON / C nanowires.

[0024] This embodiment also provides a SiAlON / C nanowire composite material prepared by the aforementioned preparation method.

[0025] The SiAlON / C nanowire composite material prepared in this embodiment was subjected to transmission electron microscopy analysis and energy spectrum element analysis. The transmission electron microscopy (TEM) image and energy spectrum element analysis (EDS) distribution map obtained are shown in FIG. Figure 1 .

[0026] The SiAlON / C nanowire composite material of this embodiment was used to prepare a mechanical test sample, and the preparation method was as follows: (1) Mix 10 g of SiAlON / C nanowire material with 90 g of silicone rubber, add 1.5 wt.% of ethyl orthosilicate as a curing agent, and stir for 10 minutes to obtain a mixed slurry; (2) Pour the mixed slurry into a standard mold for mechanical testing and then place it in a vacuum machine for degassing to reduce internal porosity; (3) Place in an oven at 80°C and dry for 3 hours to obtain a mechanical test sample.

[0027] Example 3 A method for preparing a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions, specifically comprising: (1) 15 g Si3N4 and 8 g aluminum powder were mixed in a ball mill jar, 150 mL water was added, and the mixture was ball milled at 290 rpm for 3 h. The product was then taken out and dried in an oven.

[0028] (2) The dried ball-milled product was mixed with 20 g of graphene in a crucible. The crucible was then placed in a tube furnace and sintered at 1800°C in a nitrogen atmosphere at 10 MPa. After sintering for 2 hours, the crucible was unsealed to obtain a crude SiAlON / C nanowire product.

[0029] (3) The SiAlON / C nanowire crude product in the crucible was placed in 80 mL of deionized water, 1 g of KH-450 coupling agent was added to adjust the viscosity of the water-based slurry, and then ultrasonic dispersion treatment was performed for 1 h.

[0030] (4) After ultrasonic dispersion, the suspension was centrifuged for 30 min and allowed to stand for stratification at a centrifugal speed of 8000 rpm. The upper layer of the suspension was accurately extracted by pipette and then oven-dried to obtain purified SiAlON / C nanowires.

[0031] This embodiment also provides a SiAlON / C nanowire composite material prepared by the aforementioned preparation method.

[0032] The SiAlON / C nanowire composite material of this embodiment was used to prepare a mechanical test sample, and the preparation method was as follows: (1) Mix 10 g of SiAlON / C nanowire material with 90 g of silicone rubber, add 1.5 wt.% of ethyl orthosilicate as a curing agent, and stir for 10 minutes to obtain a mixed slurry; (2) Pour the mixed slurry into a standard mold for mechanical testing and then place it in a vacuum machine for degassing to reduce internal porosity; (3) Place in an oven at 80°C and dry for 3 hours to obtain a mechanical test sample.

[0033] The wave absorption performance of the SiAlON / C nanowire composite material prepared in Examples 1-3 was analyzed, and the obtained wave absorption performance diagram is shown in FIG. Figure 2 .

[0034] Comparative Example 1 Compared with Example 2, the only difference is that graphene is not added during the preparation of the SiAlON / C nanowire composite material.

[0035] Comparative Example 2 The only difference compared to Example 2 is that after the SiAlON / C nanowire composite material is prepared, it is placed in a tube furnace and heat treated in air at a constant temperature of 800°C for 10 hours. This process is intended to completely remove the carbon component in the SiAlON / C nanowires, resulting in pure SiAlON nanowires.

[0036] Comparative Example 3 Compared with Example 2, the only difference is that no KH-450 coupling agent is added during the ultrasonic dispersion of the crude SiAlON / C nanowire product in ion water.

[0037] Comparative Example 4 Compared with Example 2, the only difference is that the sintering temperature in the tube furnace is 1600°C.

[0038] Comparative Example 5 Compared with Example 2, the only difference is that the sintering time in the tube furnace is 4 hours.

[0039] Comparative Example 6 Compared with Example 2, the only difference is that 25 g of graphene is used.

[0040] Comparative Example 7 Compared with Example 2, the only difference is that the Si3N4 and aluminum powder in the raw materials are mixed with the graphene and sintered after being dried, thus eliminating the process of water ball milling.

[0041] Comparative Example 8 This comparative example only provides one mechanical test sample, and the preparation method is as follows: (1) Mix 90g of silicone rubber with 1.5wt.% of curing agent ethyl orthosilicate and stir for 10 minutes to obtain a mixed slurry; (2) Pour the mixed slurry into a standard mold for mechanical testing and then place it in a vacuum machine for degassing to reduce internal porosity; (3) Place in an oven at 80°C and dry for 3 hours to obtain a mechanical test sample.

[0042] Performance Test 1 To verify the electromagnetic absorption performance of the nanowire composite materials of the present invention, the nanowire composite materials from Examples 1-3 and Comparative Examples 1-7 (the nanowires in Comparative Examples 1, 4, 5, and 7 were not formed and therefore could not be tested) were tested for electromagnetic wave absorption. This test used the coaxial ring method: the absorbing material was mixed with paraffin wax at a ratio of 10 wt.% and pressed into a mold with an inner diameter of 3.04 mm and an outer diameter of 7 mm to form the desired hollow coaxial ring. The test results are shown in Table 2.

[0043] Table 2 Electromagnetic wave absorption performance test results

[0044] It can be seen from the test results of Examples 1-3 and Comparative Example 1 that the addition of a carbon source is crucial to the formation of nanowires; it can be seen from the test results of Examples 1-3 and Comparative Example 2 that the carbon layer attached to the SiAlON nanowires is crucial to enhancing the absorption performance; it can be seen from the test results of Examples 1-3 and Comparative Examples 4-5 that indicators such as sintering temperature and time are crucial to the formation of nanowires; it can be seen from the test results of Examples 1-3 and Comparative Example 6 that the amount of carbon source added and the absorption performance of the prepared SiAlON / C nanowire composite material show a nonlinear relationship, and the optimal absorption performance can be obtained by controlling the composition; it can be seen from the test results of Examples 1-3 and Comparative Example 7 that wet ball milling and pre-oxidation of aluminum powder are the key to the preparation of nanowire formation.

[0045] Performance Test 2 In order to verify the mechanical toughening performance of the nanowire composite material of the present invention, the mechanical test samples in Examples 1-3 and Comparative Examples 1-8 (wherein the nanowires of Comparative Examples 1, 4, 5, and 7 were not formed and could not be tested) were subjected to mechanical property tests using a universal testing machine. The test results are shown in Table 3, wherein the stress-strain curves of Example 2 and Comparative Example 3 are shown in Table 3. Figure 3 As shown. According to the test results, the elongation of the mechanical test sample prepared in Example 2 after fracture reached 384%, which is 72.2% higher than that of the pure silicone rubber matrix in Comparative Example 8, indicating that the nanowire composite material prepared in Example 2 has good mechanical toughening ability; according to the performance comparison of Examples 1-3, the thickness of the carbon layer in the SiAlON / C nanowire has no significant effect on the toughening effect of the composite device; according to the stress-strain curves of Example 2 and Comparative Example 3, the fracture toughness of the composite device in Example 2 is 55.1% higher than that of Comparative Example 3, indicating that during the separation and purification process, adding a coupling agent such as KH-450 to adjust the viscosity of the water-based slurry can effectively improve the purity of the finally separated nanowires.

[0046] Table 3 Mechanical properties test results

[0047] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions, characterized in that: Including: ball milling, high pressure sintering, ultrasonic dispersion, drying; The ball milling comprises mixing Si3N4 and aluminum powder, adding water, ball milling, and drying to obtain a dry ball milled product; The high-pressure sintering comprises mixing the dried ball-milled product with graphene in a crucible, placing the crucible in a tube furnace, performing high-pressure sintering, and unsealing the crucible to obtain a SiAlON / C nanowire crude product.

2. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: In the ball milling, the ratio of Si3N4 to aluminum powder is 14-16g:7.5-8.5g; The ratio of Si3N4 to water is 14-16g:140-160mL; Si3N4 is β phase with a particle size of 1-3μm.

3. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: During the ball milling, the speed of the ball milling is 250-300 rpm and the time is 3-4 hours.

4. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: The usage ratio of Si3N4 in the ball milling to graphene in the high pressure sintering is 14-16g:9-11g.

5. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: During the high pressure sintering, the graphene has a model of AP-3 and a d50 of 4-6 μm; The temperature during high pressure sintering is 1800-1900°C and the pressure is 10-15 MPa; The high pressure sintering is carried out in a nitrogen atmosphere; The high pressure sintering time is 2-3 hours.

6. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: The ultrasonic dispersion is performed by placing the SiAlON / C nanowire crude product in a crucible into deionized water, adding a coupling agent, and performing ultrasonic dispersion treatment to obtain a suspension.

7. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: The ratio of Si3N4 in the ball mill to deionized water in the ultrasonic dispersion is 14-16 g:80-100 mL; The amount ratio of Si3N4 in the ball mill to the coupling agent in the ultrasonic dispersion is 14-16g:0.9-1.2g.

8. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: In the ultrasonic dispersion, the coupling agent is KH-450 coupling agent; The ultrasonic dispersion treatment time is 1-2 hours.

9. The method for preparing the SiAlON / C nanowire composite material with both electromagnetic absorption and mechanical toughening functions according to claim 1, characterized in that: The drying step comprises centrifuging the suspension and then allowing the suspension to stand for stratification, taking the upper suspension layer, and drying the upper suspension layer to obtain a SiAlON / C nanowire composite material; During the drying process, the centrifugal speed is 8000-10000 rpm and the time is 30-40 min; When taking the upper suspension, accurately extract the upper suspension using a pipette.

10. A SiAlON / C nanowire composite material prepared by the preparation method according to any one of claims 1 to 9.

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