Microwave absorbing material: a novel mxenes / nano carbon sphere composite

Author: Dai Binzhou With the rapid development of modern military, the survival ability of military targets and the penetration ability of weapon systems are seriously challenged, which puts forward higher requirements for the "stealth" ability of weapon equipment Therefore, the rapid development of military requires more and more high-performance electromagnetic wave absorbing materials, which can not only enhance the targets (aircraft, tank, wheel The stealth performance of ships can also greatly improve the survival rate of weapons In addition, with the popularization of electronic equipment and the improvement of communication system, mobile phones (0.8-1.5 GHz, 3 GHz, 4 GHz), satellite broadcasting system (11.7-12.0 GHz), local area network system (2.45 GHz, 5.0 GHz, 19.0 GHz) are in the microwave range, 22.0 GHz) and other communication devices are used more and more frequently These devices facilitate our daily life, but the following electromagnetic pollution problems are more and more serious (harm to health, interference with instruments, information leakage, etc.) Therefore, the development of high-performance electromagnetic wave absorbing materials is of great significance for national defense and civil use Recently, a novel two-dimensional layered Ti 3C 2T x mxenes / nano carbon sphere composite was prepared by Associate Professor Fan Bingbing and Dr Zhao Biao of Zhengzhou University A large number of carbon spheres (d = 30 nm ~ 60 nm) were formed in situ on the surface and between the layers of Ti 3alc2tx after etching Ti 3alc2 ceramics with a certain concentration of hydrofluoric acid for a long time In addition, the formation mechanism of carbon spheres is explained reasonably, and the composite material with excellent electromagnetic wave absorption performance is applied in the field of absorbing materials This achievement was published in Journal of Materials Chemistry C (DOI: 10.1039 / c8tc01404c) under the title of "novel two dimensional Ti 3c2t x mxenes / nano carbon spheres hybrids for high performance microwaveabsorption" The first author of this paper is Dai Binzhou, a master student of Zhengzhou University Fig 1 XRD patterns obtained by etching Ti 3AlC 2 at different times, S1, S2, S3, S4 and S5 correspond to 1 h, 3 h, 6 h, 9 h and 12 h respectively (photo source: J mater Chem C, 2018, advance article doi: 10.1039/c8tc01404c) Fig 2 (a) is the SEM map of Ti 3 ALC 2, (b), (c), (d), (E) and (f) are the SEM maps of Ti 3 ALC 2 corroded at different times, corresponding to 1H, 3h, 6h, 9h and 12h (photo source: J mater Chem C, 2018, advance article doi: 10.1039/c8tc01404c) the author has carried out a series of characterization on two-dimensional layered Ti 3c2t x mxenes / nano carbon spheres composite Fig 1 is the XRD pattern of ti3c2tmxenes / nano carbon spheres composite material It can be seen from the figure that the author has successfully prepared ti3c2tmxenes material The (002) diffraction peak of the material shifts to a low angle with the increase of corrosion time The reason for this phenomenon is that the appearance of carbon spheres will make the interlayer of ti3c2tmxenes larger Fig 2 is the SEM morphology of different samples After 6 hours of corrosion, nano carbon spheres began to appear on the surface of Ti 3c2t x mxenes With the increase of corrosion time, the diameter and quantity of nano carbon spheres increased Fig 3 (a) shows the reflection loss curve of samples S1 (1H), S2 (3H), S3 (6h), S4 (9h) and S5 (12h) mixed with 50 wt% paraffin respectively at a thickness of 2 mm (b) The figure shows the reflection loss curve of sample S5 mixed with 50 wt% paraffin at different thicknesses (c) The figure is a three-dimensional one of (b) (photo source: J mater Chem C, 2018, advance article doi: 10.1039/c8tc01404c) Figure 4 (a) mechanism diagram of Ti 3C 2T x mxenes / nano carbon sphere composite Firstly, the Al layer in Ti 3AlC 2 was extracted by HF solution of certain concentration Then, H + and F - in HF acid solution continue to "attack" ti3c2tx to break part of the ti-c bond, and then the free carbon will migrate to the surface and interlayer of ti3c2tx to form carbon nanospheres (b) Flow chart of Ti 3C 2T x mxenes / nano carbon spheres composite (c) The figure shows the absorption mechanism of Ti 3C 2T x mxenes / nano carbon spheres composite (photo source: J mater Chem C, 2018, advance article doi: 10.1039/c8tc01404c) Figure 3 shows the reflection loss curve of the sample After 12 hours of corrosion, ti3c2tmxenes / nano carbon spheres composite material has very excellent electromagnetic wave absorption performance By adjusting the thickness of the sample, the loss and reflection values can all reach below - 10 dB in the frequency band of 3-18 GHz When the thickness of the sample is 4.8 mm, the minimum reflection loss can reach - 54.67 dB Fig 4 (a) is the mechanism diagram of Ti 3C 2T x mxenes / nano carbon sphere composite First of all, the Al layer in Ti 3AlC 2 was extracted by HF solution of certain concentration Then, H + and F - in HF solution continue to "attack" ti3c2tx to break part of the ti-c bond, and then, the free carbon will migrate to the surface of ti3c2tx and form carbon nanospheres between the layers This is the first time that the formation mechanism of carbon spheres has been proposed Figure 4 (c) shows the absorption mechanism of Ti 3C 2T x mxenes / nano carbon spheres composite Ti 3C 2T x mxenes has high electrical conductivity, but high electrical conductivity is fatal for electromagnetic wave absorbing materials When the electrical conductivity of materials is too high, most of the incident electromagnetic waves will be reflected, rather than entering the material The Ti 3c2t x mxenes / nano carbon spheres composites were obtained by long-term corrosion of Ti 3alc2 with hydrofluoric acid at a certain concentration for the first time The electromagnetic parameters of Ti 3C 2T x mxenes / nano carbon spheres composites were studied The results show that the appearance of carbon spheres can effectively increase the dielectric loss of the samples The author attributed the results to: 1 Amorphous carbon is a good dielectric loss material; 2 Carbon spheres and Ti 3C 2T x mxenes form a heterogeneous interface, which will produce interface polarization in the electromagnetic field In addition, the preparation method of Ti 3c2t x mxenes / nano carbon spheres composite is reported in detail This method is universal and can be extended to the synthesis of other mxenes based heterostructures Professor Zhang Rui