| The extensive application of wireless communication technology and the explosive development of electronic equipment greatly facilitated human life and military operations.However,this led to an increase in electromagnetic interference,radiation hazards,and information leakage issues.Traditional electromagnetic protection materials suffer from drawbacks such as low attenuation characteristics,high density,challenging processing,susceptibility to corrosion,and short service life due to their single attenuation mechanism and weak stability.Therefore,designing and preparing electromagnetic protection materials with thin thickness,lightweight,wide frequency,strong attenuation capacity,and multi-function capabilities holds significant strategic and economic value.Metal-organic frameworks（MOFs）featuring that periodically arranged metal ions,controllable heteroatom-doping,large specific surface area and adjustable porosity and provided an efficient method for the preparation of magnetic nanoparticles/porous carbon matrix composites with tunable components and diverse topologies.Furthermore,next-generation electromagnetic protection materials will be applied to various complex and extreme environments,which required robust multifunctionality and environmentally adaptive to adapt to frontier and future military applications.In order to resolve the issues of unclear mechanism,unsatisfactory shielding/wave-absorbing performance,weak interactions,poor functional synergy and unreliable environmental adaptability of electromagnetic protective materials.In this paper,a series of MOFs-derivatives/dielectric matrix nanocomposites with controllable structures and components were constructed using electrostatic adsorption,in-situ self-assembly and pyrolysis processes,and elucidated the correlation between multiphase components,topology,nano-structural defects and heterogeneous interfaces and electromagnetic wave loss performance;the polyfluorinated resin support materials with diverse structures and stable interface behavior was synthesized by molecular structure and curing network design.Varieties of composite that integrate excellent electromagnetic protection,robust environmental adaptability and multifunctionality was obtained by C-F···πinteraction and microwave irradiation strategy,and described the stability evaluation and multi-synergistic mechanism of electromagnetic protective materials under extreme service conditions.Additionally,the research expanded the multi-functional integrated application system and opened up advanced application scenarios of next-generation electromagnetic protection materials,which brought infinite possibilities for the development of electromagnetic protection field.The specific innovations and conclusions are as follows.1.A unique in-situ nitrogen regulation engineering and dielectric composite strategy were proposed for resolving the problems of blind design and dependence on semi-empirical principles in the application of MOFs derivatives in microwave absorption.The research clarified the relationship between multiphase components,topological structure and electromagnetic parameters,and revealed the microwave absorption enhancement mechanism of cobalt-based MOFs derivatives and their dielectric composite nanocomposite.Magnetic nanoparticle/porous carbon matrix composites with different nanomorphologies were prepared by pyrolysis the four different nitrogen-containing bridging ligands cobalt-based MOFs precursors which synthesized in situ self-assembly.The result showed that suitable nitrogen anion modulation produced optimized structural defects and lattice misalignments,such as point defects,discontinuous lattice streaks,and lattice aberrations,thus induced the generation of multiphase and multicomponent heterointerfaces,as well as altered electrical conductivity.The electromagnetic wave absorption/far-field stealth performances of four bridging ligand derivatives at different filling levels were investigated using the transmission line method and RCS simulation calculations,and the electromagnetic absorption mechanisms corresponding to the electromagnetic parameters at the optimal filling levels were discussed in detail to establish a clear correlation between the nitrogen modulation level and the EMW loss capability.Based on the foundation,the in-situ growth of ZIF67on three dielectric substrates（r GO,MXene and CNT）by electrostatic interaction demonstrated the more accurate tunability of dispersion,composition and topology,verified the more obvious structural advantages of multi-component coexistence of nanocomposites than single MOFs materials.The result showed that Co-r GO@6%,Co-MXene@18%and Co-CNT@14%nanocomposites exhibited stronger absorption loss values（-53.03,-51.43 and-57.62 d B）,larger effective absorption bandwidth（4.42,3.23 and 4.43 GHz）,lower load（4,18 and 14%）and thinner matching thickness（1.7,1.5 and 1.7mm）and better electromagnetic stealth behavior,furthermore,elaborated the enhancement mechanism of the dielectric composite strategy with multi-component coexistence.Chapter 2 provided theoretical guidance for the structure and composition design of electromagnetic protective materials with strong environmental adaptability.2.In order to solve the problems of secondary electromagnetic pollution and obvious deficiency of functions in underwater/chemical corrosion environments of shielding materials.Chapter 3 combined with the multifunctionality of double modified graphene,the structure of perfluorinated single-ended epoxy dangling chain,C-F···H-N/πinteraction and microwave irradiation enhancement effect,and the NH2-Co NC@r GO-FEP composite was prepared for excellent electromagnetic shielding（56.21 d B,99.998%shielding effectiveness,SEA>>SER）,high mechanical strength（64.4 MPa,3.4 GPa,33.7k J/m2）,strong superamphiphobicity（154o,151o）and long-term corrosion resistance(30 days,Rc=6.31×1010,Rct=2.51×1011).The enhancement effect of microwave irradiation was quantitatively evaluated by iso-conversional method,and the results showed that“thermal/non-thermal effect”could improve the nanofillers’dispersibility,interfacial bonding strength and regular crosslinking structure.The excellent EMI shielding was attributed to the effective complementary multiple loss mechanisms among magnetic/dielectric coupling,interfacial polarization and dipole relaxation.The low surface energy of the fluorocarbon chain segment and the rough surface of the micro-nano structure synergistically achieved strong superamphiphobicity.The synergistic trinity protection strategy of anode and cathode protection,superhydrophobic shielding and“labyrinth effect”greatly improved the long-term corrosion resistance.The experimental results and mechanism researches of Chapter 3provided new design concepts and technical guidance for the application of epoxy nanocomposites in aerospace,underwater equipment and electronic devices.3.The creative design of the integration of robust environmentally adaptive,multifunctionality and blue energy harvesting was proposed for resolving the issues of structural/functional variation of absorbing materials and energy shortage in extreme environments.And the problem of double environmental pollution was effectively solved by cleverly combining the multi-fluorinated pendant chain network structure and the barrier/catalytic/adsorption functionality of the multi-dimensional carbon/metal framework.The synergistic effect of C-F···πinteraction and microwave irradiation enhanced the dispersibility of nanofillers（Co CNT and Fe Nir GO）,interface bonding strength,and regular cross-linked structure.And the MAMs exhibited an excellent RLminof-75.18 d B（>99.99999%absorption）and EAB of 3.95 GHz benefited from multi-magnetic-dielectric attenuation,abundance interface/dipole relaxation losses,λ/4 interference cancellation,proper conduction loss,impedance matching,and multiple-reflection loss.Remarkably,this composite exhibited robust multifunctionality and environmental adaptive:excellent mechanical（80.3 MPa）,superamphiphobicity（153o and 151o）,long time anticorrosion（45days）,and high flame retardancy（V-0 rating,low heat/smoke release）,and demonstrating the mechanism of stable protection performance.Besides,the nanocomposite was assembled into the liquid-solid triboelectric nanogenerator（LS-TENG）for blue energy harvesting,the synergistic effect of significant negative polyfluorinated dangling chains,micro/nano-rough structures and high-porosity multi-dimensional metal frameworks greatly improved the output performance and durability of LS-TENG.At present,there was no research on the application of MOFs in TENG.Consequently,chapter 4 opened up infinite possibilities for the application of electromagnetic wave absorption technology in complex and sustainable energy scenarios.4.An integrated strategy of 4D printing,multi-stable controllable programming,ultra-efficient electromagnetic wave absorption and robust environment adaptivity was proposed for resolving the problems of weak shape adaptability in complex structural applications and instability of protective functions under extreme application conditions of absorbing materials.The stable and extrudable Co M@Co Ni C-F inks were obtained by optimizing rheological behavior via C-F···πinteraction and multi-dimensional rigid structure.The high-resolution and complex 4D-printed objects were obtained by the DIW technology,and the shape retention and overall mechanical properties were improved by microwave irradiation curing.Besides,the microwave absorbing composites exhibited reliable light/heat induced shape memory properties（Rf>98%,Rr>97.5%）due to the rigid-flexible integration of the two-phase components with a nanoscale bi-continuous phase separation structure,which benefit to fabricate 4D printed structures with dynamic shape evolution behavior.The nanocomposites exhibited excellent RLmin（-64.78 d B）and wide EAB（4.6 GHz）,and achieved the tunable absorbing behavior by simply adjusting the filler content and programmable surface pattern.And RCS simulation further evaluated its excellent EMW stealth behavior under practical far-field conditions（21.35 d B·m2）.It was noteworthy that the environmental adaptivity and multi-synergistic enhancement mechanism of the composite under humidity,seawater,physical damage,chemical corrosion and high-temperature flames extreme conditions were also demonstrated in detail.Chapter 5 provided important technological innovation and design concepts for the development of MAMs,and created infinite feasibility in the advanced assembly field. |
