Research On Photothermal Conversion Mechanism Of V₂C MXene And Its Application In Laser Ignition

As a kind of excellent safety and reliability ignition technology,laser ignition has been widely used in many fields owing to the advantages of strong anti-electromagnetic interference ability,high precision and small energy consumption.MXene,a new two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to the high light absorption performance and perfect internal photothermal conversion efficiency.In this thesis,we report the intriguing photothermal conversion property of vanadium carbide(V₂C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,V₂C MXene can not only convert the incident laser energy into thermal energy through the physical photothermal effect,but also trigger the exothermic oxidation of the V₂C MXene and further release chemical energy.Through the physical/chemical coupling mechanism to release more heat and produce high temperature pluse(HTP).The surface plasmonic resonance(SPR)effect of Au nanorods(Au NRs)can enhance the light absorption of V₂C MXene and promote the release of chemical energy more completely.Owing to the high light absorption performance and unique light-to-heat conversion property,the self-supported Au NRs/V₂C MXene membrane can be served as HTP generator for laser ignition of energetic materials,such as2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(CL-20).Furthermore,taking advantage of the high specific surface area and in-situ generation of VO_X/C composites at high temperature of V₂C MXene,the catalytic ignition performance of V₂C MXene for ammonium perchlorate(AP)has also been studied.The main research contents are as follows:(1)The self-supported Au NRs/V₂C MXene membranes were prepared,and the light absorption of Au NRs/V₂C MXene membrane was significantly improved by the SPR enhancement effect of Au NRs.The laser-induced temperatures of membranes under different laser intensity were measured.The results show that the peak temperature of Au NRs/V₂C MXene membrane is 750?higher than V₂C MXene(650?)and Au NPs/Ti₃C₂ MXene(600?)under the laser intensity of 79.6 W·cm^-2.The XPS characterization of V₂C MXene based membranes before and after laser irradiation revealed that the V₂C MXene based membranes could rapidly undergo redox reaction under irradiation of laser,resulting in more thermodynamically stable products,such as VO_X and C.Moreover,V₂C MXene can release chemical energy more completely than Ti₃C₂ MXene,which is conducive to achieve higher peak temperature.The self-supported Au NRs/V₂C MXene membrane be served as HTP generator,the laser ignition performance of CL-20 was studied.The ignition results show that the ignition delay time is 29 ms and the ignition threshold is 140 m J,which was lower than typical HTP generators such as Au NPs/Ti₃C₂ MXene(220 m J)and GO(240 m J).(2)The V₂C MXene/AP composites were prepared by freeze-drying in order to realize the high specific area contact between AP and V₂C MXene.TGA/DSC results show that the HTP temperature of V₂C MXene/AP composites can decrease from 440.10?to 214.20?by 51.3%,the reaction activation energy decrease from 273.70 k J·mol^-1 to 143.20 k J·mol^-1 by 47.7%,and the heat release increase from 591.7 J·g^-1 to 2377.8 J·g^-1 by 3.1 times,compared with raw materials AP.The laser ignition performance of V₂C MXene/AP composites was further studied.