A Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber and a preparation method thereof

Abstract

The application belongs to the technical field of terahertz wave absorption, and relates to a terahertz wave absorber, in particular to a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber and a preparation method thereof, which provides an integrated high-stress absorber with wide-band absorption characteristics, high-temperature resistance and oxidation resistance for the terahertz frequency band; the application is based on 3D printing technology to shape the structure, and a kind of inverted-pyramid structure is designed, then a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber is prepared by Joule flash, which has a minimum reflection loss of 25dB in the frequency band of 1-4THz, and the maximum reflection loss can reach 50dB, with good absorption performance; at the same time, the terahertz absorber has the characteristics of high temperature resistance and strong stress, and shows outstanding application prospect in the field of terahertz wave absorption.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of terahertz wave absorption, and relates to a terahertz wave absorber, and particularly relates to a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber and a preparation method thereof. BACKGROUND

[0002] Terahertz waves (0.1 THz-10 THz) are an important wave band between microwaves and infrared rays, have many very unique properties, and have good optical resolution, strong penetration ability and wideband spectrum and other characteristics. With the rapid development of various high-frequency electronic devices, the devices inevitably radiate a large amount of terahertz waves to space, which also leads to the emergence of problems such as terahertz wave electromagnetic interference; EMI not only affects the normal operation of other electronic devices, but also causes serious harm to human health and the environment, and the terahertz wave absorbing material can convert the incident electromagnetic wave into heat or other forms of energy for dissipation, thereby greatly reducing the harm of electromagnetic wave radiation.

[0003] MAX phase material is a new type of ceramic material, which has excellent mechanical properties, electrical properties, thermal stability and oxidation resistance due to its dual characteristics of metal and ceramic, and is an excellent choice as a functional wave-absorbing material. As described in the document "Shi Y M, Luo F, Liu Y, Zhou W C, Zhang X H. Preparation and microwave absorption properties of Ti3AlC2 synthesized by pressureless sintering TiC / Ti / Al [J]. International Journal of Applied Ceramic Technology, 2015, 12: E174-E177.", TiC powder, Ti powder and Al powder are used as raw materials, and Ti3AlC2-MAX phase material is prepared by pressureless sintering at 1350 DEG C. The influence of different paraffin filling ratios on the wave-absorbing performance of the material is also studied. It is found that the reflection loss of 70wt% MAX phase is greater than 10 dB in the X wave band, and has the best wave-absorbing performance. However, the wave-absorbing performance is still limited by the high electrical conductivity of the material itself, so when the pure MAX phase is used as a wave-absorbing agent alone, the high electrical conductivity will cause strong reflection of electromagnetic waves, resulting in a decrease in the wave-absorbing ability.

[0004] It is an effective strategy to improve wave-absorbing performance by using multiple scattering and reflection of periodic structures to achieve better impedance matching to reduce the impact of strong reflection. However, traditional hot pressing relies on molds and can only produce simple shapes such as flat plates and cylinders, making it difficult to achieve 3D printing-supported hollow, porous, cantilevered, or biomimetic structures. Moreover, complex structures require multiple processing steps such as cutting and bonding, increasing the risk of defects. In addition, mold design and processing can take weeks to months, making it difficult to respond to rapid prototyping needs. Furthermore, hot pressing requires mechanical processing of sintered bulk materials into the target shape, resulting in 30-70% loss of raw materials (such as cutting debris). In contrast, 3D printing does not require molds and can be completed in just a few hours from design to finished product. Moreover, 3D printing controls waste rates to less than 5% through additive manufacturing. Therefore, using additive manufacturing structures to improve wave-absorbing performance is a feasible technical solution. As described in the literature "Liu, Pei, et al. Direct ink writing printed flexible double-layer staggered woodpile structure for multi-band compatible absorption of gigahertz and terahertz waves." Chemical Engineering Journal 478 (2023): 147474, a flexible double-layer staggered woodpile structure was prepared using direct ink writing (DIW) 3D printing technology. The unique periodic geometric design and material gradient characteristics of the structure enable efficient multi-band compatible absorption in the GHz (1 GHz-18 GHz) and THz (0.1 THz-2 THz) frequency bands. By adjusting the size and spacing of the two-layer woodpile units and the impedance matching of the carbon-based composite ink, the structure achieves a reflectivity of less than -10 dB in multiple frequency bands, while also being lightweight (density <0.1 g / cm 3 ) and flexible, providing a new solution for cross-band stealth and electromagnetic protection. However, there is still a need for integrated high-stress wave-absorbing materials with wide-band absorption characteristics, high-temperature resistance, and oxidation resistance in the terahertz wave band. SUMMARY

[0005] The application aims to provide a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber and a preparation method thereof, and provide an integrated high-stress absorber with wide-band absorption characteristics, high-temperature resistance and oxidation resistance in the terahertz frequency band.

[0006] To achieve the above-mentioned purposes, the technical scheme adopted by the application is:

[0007] A Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber, characterized in that the terahertz wave absorber is in a grid structure, each grid unit adopts an inverted-pyramid structure; the inverted-pyramid structure is a cavity structure, which is composed of N layers of square wires stacked in sequence, the centers of each layer of square wires are arranged in coincidence, and the side length of the square wire is increased by equal amount in sequence from bottom to top; the square wire is made of Ti3AlC2-MAX phase material.

[0008] Further, in the inverted-pyramid structure, the number of layers of the square wire is N≥4.

[0009] Further, in the inverted-pyramid structure, the unit period of the grid unit is 2-5mm.

[0010] Further, in the inverted-pyramid structure, the wire diameter of each layer of square wire is the same, specifically 0.8mm-1.2mm.

[0011] Further, the preparation method of the Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber, characterized in that it comprises the following steps:

[0012] Step 1: carboxymethyl cellulose sodium (CNF) is used as a binder, the binder is ball-mixed with Ti source raw material, C source raw material and Al source raw material to obtain a mixture; the mixture is mixed with deionized water to form CNF@Ti3AlC2-MAX precursor 3D printing ink;

[0013] Step 2: a CNF@Ti3AlC2 MAX precursor embryo is printed by DIW 3D printing technology;

[0014] Step 3, the CNF@Ti3AlC2-MAX precursor embryo is sintered at 1375-1425 DEG C for 1-3 min by adopting a joule flash burning process, and a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber is obtained.

[0015] Further, in step 1, the ratio of the Ti source raw material, the C source raw material and the Al source raw material is Ti:C:Al=3:2:1.2.

[0016] Further, in step 1, the mass ratio of sodium carboxymethyl cellulose (CNF) is 2wt%-6wt%.

[0017] Further, in step 1, the specific process of mixing the mixture with deionized water is as follows: according to the ratio of 10.33:3, deionized water is added to the mixture, and the mixture is mixed into a gel state; according to the ratio of 10.33:3.5, deionized water is added again, and the mixture is mixed to form a CNF@Ti3AlC2-MAX precursor 3D printing ink.

[0018] Further, in step 2, the printing process is as follows: a three-axis driven desktop dispensing machine is used as a printing device, and the printing parameters are set as follows: nozzle diameter 0.8-1.2 mm, X / Y axis movement speed: 30-40 mm / s, Z axis movement speed: 20-30 mm / s, printing speed: 1-2 mm / s, and printing pressure: 0.25-0.40 Mpa.

[0019] Further, in step 3, the specific process of joule flash burning is as follows: sintering gas pressure: 0.1-0.12 Mpa, heating time: 5-10 s, holding time: 1-3 min, cooling time: 8-10 min, and sintering temperature: 1375-1425 DEG C.

[0020] Based on the above technical solution, the application has the following advantages:

[0021] The application provides a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber and a preparation method thereof. First, a CNF@Ti3AlC2 MAX precursor ink is prepared. On this basis, an inverted-pyramid structure is designed by using a direct ink writing (DIW) 3D printing technology, and the structure has good self-supporting performance. Finally, a Ti3AlC2-MAX phase inverted-pyramid structure terahertz wave absorber is prepared by using a joule flash burning method. The material has a minimum reflection loss of 25 dB in the frequency band of 1-4 THz, and the maximum reflection loss can reach 50 dB, has good absorption performance, and has the advantages of high temperature resistance and strong stress, and has a prominent application prospect in the field of terahertz wave absorption. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1Rheological property diagram of the 3D printing ink of the CNF@Ti3AlC2 MAX precursor in the application.

[0023] Figure 2 Structural schematic diagram of the inverted-pyramid-like structure in the application.

[0024] Figure 3 Principle schematic diagram of the ink direct writing (DIW) 3D printing.

[0025] Figure 4 Actual photograph of the inverted-pyramid-like structure embryo of the CNF@Ti3AlC2 MAX precursor in the application.

[0026] Figure 5 SEM diagram of the sintered sample of the inverted-pyramid-like structure of the CNF@Ti3AlC2 MAX phase in the application.

[0027] Figure 6 XRD diagram of the sintered sample of the inverted-pyramid-like structure of the CNF@Ti3AlC2 MAX phase in the application.

[0028] Figure 7 Reflection loss frequency domain diagram of the sintered sample of the inverted-pyramid-like structure of the CNF@Ti3AlC2 MAX phase in the application. DETAILED DESCRIPTION

[0029] To make the purpose, technical scheme and beneficial effects of the application more clear and explicit, the application is further described in detail below in combination with the drawings and examples.

[0030] The embodiment provides an inverted-pyramid-like structure terahertz wave absorber of a Ti3AlC2-MAX phase and a preparation method thereof, the inverted-pyramid-like structure terahertz wave absorber is prepared by 3D printing, and mainly comprises the following steps: preparation of 3D printing ink of a CNF@Ti3AlC2-MAX precursor, inverted-pyramid-like structure 3D printing based on ink direct writing (DIW), and sintering of the CNF@Ti3AlC2 MAX phase material based on joule flash sintering. The technical scheme information of the embodiment is described in detail below in combination with tests,

[0031] 1. Preparation of 3D printing ink of CNF@Ti3AlC2 MAX precursor.

[0032] According to the molar ratio of Ti:C:Al=3:2:1.2, the raw materials are weighed, 7.2 g of Ti powder, 1.2 g of graphite powder, and 1.62 g of Al powder, and 3wt% of sodium carboxymethyl cellulose is added (relative to the total mass of Ti powder, graphite powder and Al powder); then the powder is poured into a ball mill tank, a ring of sealing glue is sealed on the edge of the tank body to reduce the oxidation of oxygen in the air, and then the ball mill tank is placed in a planetary ball mill, the planetary ball mill is adjusted to a working frequency of 20 Hz, and the ball milling is carried out in a positive and negative mode for 8 h, so that the CNF@Ti3AlC2-MAX precursor powder is obtained;

[0033] Then, the milled precursor powder is placed in an agate mortar, 3 g of deionized water is injected into the agate mortar using a pipette, and the mixture is stirred and ground for 5 min until no powder-like sample appears in the mortar, i.e., the powder and deionized water are fully mixed to form a gel; then 3.5 g of deionized water is added, and a total of 6.5 g of deionized water is added, so that the viscosity of the powder is adjusted to an appropriate range, thereby preparing the CNF@Ti3AlC2 MAX precursor ink for 3D printing.

[0034] The rheological properties of the ink are shown in FIGS. 1 to 4. Figure 1 Figure 1 In FIG. 1, a is a curve of complex viscosity (η*) with respect to oscillation angular frequency (ω), Figure 1 In FIG. 2, b is a curve of G' and G" with respect to oscillatory shear stress, Figure 1 In FIG. 3, c is a curve of η* under two cyclic loads of low shear rate (10 -1 rad / s) and high shear rate (10 2 rad / s), Figure 1 In FIG. 4, d is the corresponding yield stress at the intersection of G' and G"; as can be seen from the figure, the printing ink shows good shear thinning property, and the viscosity of the ink decreases with the increase of shear frequency, which is beneficial to the smooth extrusion of the ink. The printing ink shows a relatively high complex viscosity at a low shear frequency, which is in the order of 10 5 above; at a high shear frequency, the complex viscosity decreases significantly, and changes to 10 3 above. When the two cycles are experienced and the viscosity is restored to a high shear frequency, the retention rate of the viscosity is more than 99%, which shows good thixotropy. The yield stress of the ink is 137.69 Pa, which is relatively consistent with the requirements of 3D printing of ceramic materials, and the good G' also makes the ink have good self-supporting property.

[0035] 2. Inverted pyramid structure 3D printing based on ink direct writing (DIW);

[0036] ​For electromagnetic wave absorption, the wave-absorbing structure composed of wave-absorbing materials requires strong electromagnetic loss capability; on the other hand, a gradient structure needs to be designed to form a gradient distribution in the direction of electromagnetic wave incidence; therefore, in order to realize a high-performance absorbing unit structure with wideband absorption, as shown in Figure 2 , a layered gradient structure is proposed, the layered order is at least 4, each unit adopts a quasi-inverted pyramid structure, the quasi-inverted pyramid structure is a cavity structure, specifically composed of N layers of square line bodies stacked in turn and the centers of each layer of square line bodies coincide, in the order from bottom to top, the side length of the square line body increases by equal amount in turn. The layered gradient design strategy can make the electromagnetic wave absorbing structure realize better impedance matching, at the same time, the grid structure is helpful for the dissipation of electromagnetic waves by the absorbing material, because the electromagnetic waves are reflected multiple times in the periodic structure, accompanied by loss absorption in the medium.

[0037] The quasi-inverted pyramid structure is prepared by direct ink writing (DIW) 3D printing, for direct ink writing (DIW) 3D printing, the principle is as shown in Figure 3 . Using the above ink, using a desktop dispensing machine with three-axis drive as the printing equipment, using a pneumatic extrusion device, according to the designed 3D printing path for DIW 3D printing, after printing, the sample is transferred to a ventilated dry place, dried at room temperature for 24h, thereby obtaining the quasi-inverted pyramid structure embryo of CNF@Ti3AlC2 MAX precursor, as shown in Figure 4 , the specific printing parameters are shown in Table 1:

[0038] Table 1

[0039]

[0040] 3, sintering of CNF@Ti3AlC2 MAX phase material based on joule flash;

[0041] The quasi-inverted pyramid structure embryo of CNF@Ti3AlC2 MAX precursor formed by 3D printing is subjected to joule rapid sintering in an inert atmosphere with argon gas protection, thereby obtaining the CNF@Ti3AlC2 MAX phase material, the specific sintering parameters are shown in Table 2:

[0042] Table 2

[0043]

[0044] In order to further characterize the crystal structure and phase composition of the material, SEM and XRD are used to determine the crystal phase existing in the material. As shown in Figure 5 , the SEM image of the CNF@Ti3AlC2 MAX phase quasi-inverted pyramid structure sintered sample can be seen, the typical layered structure of the Ti3AlC2 MAX phase material. As shown in Figure 6The XRD pattern of the CNF@Ti3AlC2 MAX phase inverted pyramid structure sintered sample is shown. The diffraction peaks are mainly the main diffraction peaks of Ti3AlC2 corresponding to the (104) crystal plane at 38.985°. This indicates that the Ti3AlC2MAX phase material accounts for the majority of the overall material at this temperature, which also demonstrates the effectiveness of sintering.

[0045] To further illustrate the beneficial effects of the present invention, a detailed description of its wave absorption performance is provided below.

[0046] The absorbing characterization was performed using a terahertz time-domain spectroscopy system (THz-TDS), with a usable frequency range of 0.5-4 THz.

[0047] like Figure 7 The reflection loss curves are shown. It can be seen that the inverted pyramid-like structure has good absorption of more than 22dB in the 0.5-4THz frequency band, and the maximum reflection loss can reach 50dB, demonstrating good absorption performance.

[0048] In summary, this invention, combined with 3D printing technology, provides a terahertz absorber with a Ti3AlC2-MAX phase inverted pyramid structure and its fabrication method, which can achieve beneficial terahertz frequency band absorption performance.

[0049] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A Ti3AlC2-MAX phase quasi-inverted pyramid terahertz absorber, characterized in that, The terahertz absorber has a grid structure, and each grid unit adopts a quasi-inverted pyramid structure. The quasi-inverted pyramid structure is a cavity structure, which is composed of N layers of square wires stacked sequentially. The centers of each layer of square wires coincide, and the side lengths of the square wires increase equally from bottom to top. The square wires are made of Ti3AlC2-MAX phase material. In the quasi-inverted pyramid structure, the number of square wire layers ranges from N≥4.

2. The Ti3AlC2-MAX phase quasi-inverted pyramid terahertz absorber according to claim 1, characterized in that, In the aforementioned inverted pyramid structure, the cell period of the grid unit is 2~5mm.

3. The Ti3AlC2-MAX phase quasi-inverted pyramid terahertz absorber according to claim 1, characterized in that, In the aforementioned inverted pyramid structure, the diameter of each layer of square wires is the same, specifically 0.8mm to 1.2mm.

4. The method for fabricating the Ti3AlC2-MAX phase inverted pyramid terahertz absorber according to claim 1, characterized in that, Includes the following steps: Step 1: Using sodium carboxymethyl cellulose (CNF) as a binder, the binder is ball-milled and mixed with Ti source material, C source material and Al source material to obtain a mixture; the mixture is then mixed with deionized water to form CNF@Ti3AlC2-MAX precursor 3D printing ink; Step 2: Print CNF@Ti3AlC2 MAX precursor preforms using Ink Direct Writing (DIW) 3D printing technology; Step 3: The CNF@Ti3AlC2-MAX precursor preform is sintered at 1375~1425℃ for 1~3 min using the Joule flash sintering process to obtain a terahertz absorber with a Ti3AlC2-MAX phase inverted pyramid structure.

5. The method for fabricating the Ti3AlC2-MAX phase inverted pyramid terahertz absorber according to claim 4, characterized in that, In step 1, the ratio of Ti source material, C source material, and Al source material is: Ti:C:Al = 3:2:1.

2.

6. The method for fabricating the Ti3AlC2-MAX phase inverted pyramid terahertz absorber according to claim 4, characterized in that, In step 1, the mass ratio of sodium carboxymethyl cellulose (CNF) is 2wt%~6wt%.

7. The method for fabricating the Ti3AlC2-MAX phase inverted pyramid terahertz absorber according to claim 4, characterized in that, In step 1, the specific process of mixing the mixture with deionized water is as follows: add deionized water to the mixture at a ratio of 10.33:3, and mix until it reaches a gel state; add deionized water again at a ratio of 10.33:3.5, and mix to form CNF@Ti3AlC2-MAX precursor 3D printing ink.

8. The method for fabricating the Ti3AlC2-MAX phase inverted pyramid terahertz absorber according to claim 4, characterized in that, In step 2, the printing process is as follows: a three-axis driven desktop dispensing machine is used as the printing device, and the printing parameters are set as follows: nozzle diameter 0.8~1.2 mm, X / Y axis movement speed: 30~40 mm / s, Z axis movement speed: 20~30 mm / s, printing speed: 1~2 mm / s, printing pressure: 0.25~0.40 Mpa.

9. The method for fabricating the Ti3AlC2-MAX phase quasi-inverted pyramid terahertz absorber according to claim 4, characterized in that, In step 3, the specific process of Joule flash burning is as follows: sintering gas pressure: 0.1~0.12 MPa, heating time: 5~10s, holding time: 1~3 min, cooling time: 8~10 min, sintering temperature: 1375~1425℃.

Images