Highly Porous Yet Transparent Mechanically Flexible Aerogels Realizing Solar-Thermal Regulatory Cooling

The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging.Herein,a delaminated aerogel film(DAF)is fabricated through filtration-induced delaminated gelation and ambient drying.The delaminated gelation process involves the assembly of fluorinated cellulose nanofiber(FCNF)at the solid-liquid interface between the filter and the filtrate during filtration,resulting in the formation of lamellar FCNF hydrogels with strong intra-plane and weak interlayer hydrogen bonding.By exchanging the solvents from water to hexane,the hydrogen bonding in the FCNF hydrogel is further enhanced,enabling the formation of the DAF with intra-layer mesopores upon ambient drying.The resulting aerogel film is lightweight and ultra-flexible,which pos-sesses desirable properties of high visible-light transmittance(91.0%),low thermal conductivity(33 mW m^(-1) K^(-1)),and high atmospheric-window emissivity(90.1%).Furthermore,the DAF exhibits reduced surface energy and exceptional hydrophobicity due to the presence of fluorine-containing groups,enhancing its durability and UV resistance.Consequently,the DAF has demonstrated its potential as solar-thermal regulatory cooling window materials capable of simultaneously providing indoor lighting,thermal insulation,and daytime radiative cooling under direct sunlight.Significantly,the enclosed space protected by the DAF exhibits a temperature reduction of 2.6℃ compared to that shielded by conventional architectural glass.

Harness High-Temperature Thermal Energy via Elastic Thermoelectric Aerogels

Despite notable progress in thermoelectric(TE)materials and devices,developing TE aerogels with high-temperature resistance,superior TE performance and excellent elasticity to enable self-powered high-temperature monitoring/warning in industrial and wearable applications remains a great challenge.Herein,a highly elastic,flame-retardant and high-temperature-resistant TE aerogel,made of poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)/single-walled carbon nanotube(PEDOT:PSS/SWCNT)composites,has been fabricated,displaying attractive compression-induced power factor enhancement.The as-fabricated sensors with the aerogel can achieve accurately pressure stimuli detection and wide temperature range monitoring.Subsequently,a flexible TE generator is assembled,consisting of 25 aerogels connected in series,capable of delivering a maximum output power of 400μW when subjected to a temperature difference of 300 K.This demonstrates its outstanding high-temperature heat harvesting capability and promising application prospects for real-time temperature monitoring on industrial high-temperature pipelines.Moreover,the designed self-powered wearable sensing glove can realize precise wide-range temperature detection,high-temperature warning and accurate recognition of human hand gestures.The aerogel-based intelligent wearable sensing system developed for firefighters demonstrates the desired self-powered and highly sensitive high-temperature fire warning capability.Benefitting from these desirable properties,the elastic and high-temperature-resistant aerogels present various promising applications including self-powered high-temperature monitoring,industrial overheat warning,waste heat energy recycling and even wearable healthcare.

Highly Aligned Graphene Aerogels for Multifunctional Composites

Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,and thermal properties.To maximize the utilization of graphene’s in-plane properties,pre-constructed and aligned structures,such as oriented aerogels,films,and fibers,have been designed.The unique combination of aligned structure,high surface area,excellent electrical conductivity,mechanical stability,thermal conductivity,and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions,enabling advancements in diverse fields.This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites.It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively.The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties,showing enhanced electrical,mechanical,and thermal properties along the alignment at the sacrifice of the perpendicular direction.This review showcases remarkable properties and applications of aligned graphene aerogels and their composites,such as their suitability for electronics,environmental applications,thermal management,and energy storage.Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

Three-dimensional porous bimetallic metal–organic framework/gelatin aerogels: A readily recyclable peroxymonosulfate activator for efficient and continuous organic dye removal

As promising catalysts for the degradation of organic pollutants,metal–organic frameworks(MOFs)often face limitations due to the particle agglomeration and challenging recovery in liquid-catalysis application,stemming from their powdery nature.Engineering macroscopic structures from pulverous MOF is thus of great importance for broadening their practical applications.In this study,three-dimensional porous MOF aerogel catalysts were successfully fabricated for degrading organic dyes by activating peroxymonosulfate(PMS).MOF/gelatin aerogel(MOF/GA)catalysts were prepared by directly integrating bimetallic FeCo-BDC with gelatin solutions,followed by freeze-drying and low-temperature calcination.The FeCo-BDC-0.15/GA/PMS system exhibited remarkable performance in degrading various organic dyes,eliminating 99.2%of rhodamine B within a mere 5 min.Compared to the GA/PMS system,there was over a 300-fold increase in the reaction rate constant.Remarkably,high removal efficiency was maintained across varying conditions,including different solution pH,co-existing inorganic anions,and natural water matrices.Radical trapping experiments and electron paramagnetic resonance analysis revealed that the degradation involved radical(SO_(4)^(-)·)and non-radical routes(^(1)O_(2)),of which ^(1)O_(2) was dominant.Furthermore,even after a continuous 400-min reaction in a fixed-bed reactor at a liquid hourly space velocity of 27 h^(-1),the FeCo-BDC/GA composite sustained a degradation efficiency exceeding 98.7%.This work presents highly active MOF-gelatin aerogels for dye degradation and expands the potential for their large-scale,continuous treatment application in organic dye wastewater management.

Tuning the surface electronic structure of noble metal aerogels to promote the electrocatalytic oxygen reduction

The sluggish kinetics of the oxygen reduction reaction(ORR)is the bottleneck for various electrochemical energy conversion devices.Regulating the electronic structure of electrocatalysts by ligands has received particular attention in deriving valid ORR electrocatalysts.Here,the surface electronic structure of Ptbased noble metal aerogels(NMAs)was modulated by various organic ligands,among which the electron-withdrawing ligand of 4-methylphenylene effectively boosted the ORR electrocatalysis.Theoretical calculations suggested the smaller energy barrier for the transformation of O^(*) to OH^(*) and downshift the d-band center of Pt due to the interaction between 4-methylphenylene and the surface metals,thus enhancing the ORR intrinsic activity.Both Pt3Ni and Pt Pd aerogels with 4-methylphenylene decoration performed significant enhancement in ORR activity and durability in different media.Remarkably,the 4-methylphenylene modified Pt Pd aerogel exhibited the higher halfwave potential of 0.952 V and the mass activity of 10.2 times of commercial Pt/C.This work explained the effect of electronic structure on ORR electrocatalytic properties and would promote functionalized NMAs as efficient ORR electrocatalysts.

Tree‑Inspired Structurally Graded Aerogel with Synergistic Water,Salt,and Thermal Transport for High‑Salinity Solar‑Powered Evaporation

Solar-powered interfacial evaporation is an energy-efficient solution for water scarcity.It requires solar absorbers to facilitate upward water transport and limit the heat to the surface for efficient evaporation.Furthermore,downward salt ion transport is also desired to prevent salt accumulation.However,achieving simultaneously fast water uptake,downward salt transport,and heat localization is challenging due to highly coupled water,mass,and thermal transport.Here,we develop a structurally graded aerogel inspired by tree transport systems to collectively optimize water,salt,and thermal transport.The arched aerogel features root-like,fan-shaped microchannels for rapid water uptake and downward salt diffusion,and horizontally aligned pores near the surface for heat localization through maximizing solar absorption and minimizing conductive heat loss.These structural characteristics gave rise to consistent evaporation rates of 2.09 kg m^(-2) h^(-1) under one-sun illumination in a 3.5 wt%NaCl solution for 7 days without degradation.Even in a high-salinity solution of 20 wt%NaCl,the evaporation rates maintained stable at 1.94 kg m^(-2) h^(-1) for 8 h without salt crystal formation.This work offers a novel microstructural design to address the complex interplay of water,salt,and thermal transport.

Ultra-broadband microwave absorber and high-performance pressure sensor based on aramid nanofiber,polypyrrole and nickel porous aerogel

Electronic devices have become ubiquitous in our daily lives,leading to a surge in the use of microwave absorbers and wearable sensor devices across various sectors.A prime example of this trend is the aramid nanofibers/polypyrrole/nickel(APN)aerogels,which serve dual roles as both microwave absorbers and pressure sensors.In this work,we focused on the preparation of aramid nanofibers/polypyrrole(AP15)aerogels,where the mass ratio of aramid nanofibers to pyrrole was 1:5.We employed the oxidative polymerization method for the preparation process.Following this,nickel was thermally evaporated onto the surface of the AP15 aerogels,resulting in the creation of an ultralight(9.35 mg·cm^(-3)).This aerogel exhibited a porous structure.The introduction of nickel into the aerogel aimed to enhance magnetic loss and adjust impedance matching,thereby improving electromagnetic wave absorption performance.The minimum reflection loss value achieved was-48.7 dB,and the maximum effective absorption bandwidth spanned 8.42 GHz with a thickness of 2.9 mm.These impressive metrics can be attributed to the three-dimensional network porous structure of the aerogel and perfect impedance matching.Moreover,the use of aramid nanofibers and a three-dimensional hole structure endowed the APN aerogels with good insulation,flame-retardant properties,and compression resilience.Even under a compression strain of 50%,the aerogel maintained its resilience over 500 cycles.The incorporation of polypyrrole and nickel particles further enhanced the conductivity of the aerogel.Consequently,the final APN aerogel sensor demonstrated high sensitivity(10.78 kPa-1)and thermal stability.In conclusion,the APN aerogels hold significant promise as ultra-broadband microwave absorbers and pressure sensors.

In Situ Mineralization of Biomass-Derived Hydrogels Boosts Capacitive Electrochemical Energy Storage in Free-Standing 3D Carbon Aerogels

Here,a novel fabrication method for making free-standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass-derived hydrogels is presented.In situ formed flower-like CaCO_(3)molecularly embedded within the hydrogel network regulated the pore structure during in situ mineralization assisted one-step activation graphitization(iMAG),while the intrinsic structural integrity of the carbon aerogels was maintained.The homogenously distributed minerals simultaneously acted as a hard template,activating agent,and graphitization catalyst.The decomposition of the homogenously distributed CaCO_(3)during iMAG followed by the etching of residual CaO through a mild acid washing endowed a robust carbon aerogel with high porosity and excellent electrochemical performance.At 0.5 mA cm^(-2),the gravimetric capacitance increased from 0.01 F g^(-1)without mineralization to 322 F g^(-1)with iMAG,which exceeds values reported for any other free-standing or powder-based biomass-derived carbon electrodes.An outstanding cycling stability of~104%after 1000 cycles in 1 M HClO4 was demonstrated.The assembled symmetric supercapacitor device delivered a high specific capacitance of 376 F g^(-1)and a high energy density of 26 W h kg^(-1)at a power density of 4000 W kg^(-1),with excellent cycling performance(98.5%retention after 2000 cycles).In combination with the proposed 3D printed mold-assisted solution casting(3DMASC),iMAG allows for the generation of free-standing carbon aerogel architectures with arbitrary shapes.Furthermore,the novel method introduces flexibility in constructing free-standing carbon aerogels from any ionically cross-linkable biopolymer while maintaining the ability to tailor the design,dimensions,and pore size distribution for specific energy storage applications.

Selective adsorption of tetracycline by β-CD-immobilized sodium alginate aerogel coupled with ultrafiltration for reclaimed water

In this work,a novel composite material based on β-cyclodextrin-immobilized sodium alginate aerogel(β-CD/NaAlg) was developed utilizing cross-linker of epichlorohydrin and applied as an adsorbent to remove tetracycline antibiotics from reclaimed wastewater.A series of characterizations were utilized to confirm the successful synthesis of the adsorbent and this β-CD/NaAlg presented a three-dimensional network at the nanoscale or microscale.Under optimal conditions(pH=4,t=8 h,β-CD:NaAlg=9,adsorbent dosage = 1.5 g·L-1),the maximum removal rate of β-CD/NaAlg to tetracycline was 70%.The adsorption behavior of tetracycline on β-CD/NaAlg conformed to the Freundlich isotherm model(R2=0.9977) and the pseudo-second-order kinetic model(R^(2)=0.9993).Moreover,the adsorbent still removed 55.3% of tetracycline after five cycles.Specially,the adsorbent was integrated with ultrafiltration to adsorb tetracycline antibiotics from simulated reclaimed wastewater,and the removal rate of tetracycline reached 78.9% within 2 h.The existence of Cr(Ⅵ) had a negligible impact on tetracycline removal,while the presence of humic acid exhibited a promoting effect.The possible adsorption mechanisms were also elucidated through X-ray photoelectron spectroscopy and density functional theory analysis.In summary,β-CD/NaAlg represents an environmentally friendly,efficient,and sustainable adsorbent for removing tetracycline antibiotics from reclaimed water.

Extrusion 3D printing of carbon nanotube-assembled carbon aerogel nanocomposites with high electrical conductivity

Carbon nanotubes(CNTs)with high aspect ratio and excellent electrical conduction offer huge functional improvements for current carbon aerogels.However,there remains a major challenge for achieving the on-demand shaping of carbon aerogels with tailored micro-nano structural textures and geometric features.Herein,a facile extrusion 3D printing strategy has been proposed for fabricating CNT-assembled carbon(CNT/C)aerogel nanocomposites through the extrusion printing of pseudoplastic carbomer-based inks,in which the stable dispersion of CNT nanofibers has been achieved relying on the high viscosity of carbomer microgels.After extrusion printing,the chemical solidification through polymerizing RF sols enables 3D-printed aerogel nanocomposites to display high shape fidelity in macroscopic geometries.Benefiting from the micro-nano scale assembly of CNT nanofiber networks and carbon nanoparticle networks in composite phases,3D-printed CNT/C aerogels exhibit enhanced mechanical strength(fracture strength,0.79 MPa)and typical porous structure characteristics,including low density(0.220 g cm^(-3)),high surface area(298.4 m^(2)g^(-1)),and concentrated pore diameter distribution(~32.8nm).More importantly,CNT nanofibers provide an efficient electron transport pathway,imparting 3D-printed CNT/C aerogel composites with a high electrical conductivity of 1.49 S cm^(-1).Our work would offer feasible guidelines for the design and fabrication of shape-dominated functional materials by additive manufacturing.

Multifunctional Integrated Organic-Inorganic-Metal Hybrid Aerogel for Excellent Thermal Insulation and Electromagnetic Shielding Performance

Vehicles operating in space need to withstand extreme thermal and electromagnetic environments in light of the burgeoning of space science and technology.It is imperatively desired to high insulation materials with lightweight and extensive mechanical properties.Herein,a boron-silica-tantalum ternary hybrid phenolic aerogel(BSiTa-PA)with exceptional thermal stability,extensive mechanical strength,low thermal conductivity(49.6 mW m^(-1)K^(-1)),and heightened ablative resistance is prepared by an expeditious method.After extremely thermal erosion,the obtained carbon aerogel demonstrates noteworthy electromagnetic interference(EMI)shielding performance with an efficiency of 31.6 dB,accompanied by notable loading property with specific modulus of 272.8 kN·m kg^(-1).This novel design concept has laid the foundation for the development of insulation materials in more complex extreme environments.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Synthesis and microwave absorption performance of heat-treated RF/SiO_(2)aerogels

The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge.Herein,we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel(RF/SiO_(2))with a three-dimensional network structure using sol-gel,atmospheric pressure drying technique as well as heat-treated processes to achieve enhanced microwave absorption capabilities in the low frequency range.The pristine RF/SiO_(2)aerogel presented a typical micropores structure with a surface area,porous volume,and density of 146.82 m^(2)/g,62.40%,and 0.28 cm^(3)/g,respectively.Remarkably,the RF/SiO_(2)aerogel showed an effective absorption bandwidth of 3.56 GHz and a minimum reflection loss value of-46.10 d B at 2.25 mm after being heat-treated at 1500°C,while the maximum effective absorption bandwidth was 3.60 GHz at 2.30 mm.The intricate three-dimensional networks possessed remarkable impedance matching,multiple attenuation mechanisms,interfacial polarization,and dielectric loss,which were attributed to the exceptional ability to absorb electromagnetic microwaves.It offered a fresh approach to creating adaptable and effective microwave absorption materials in military defense.

Plasma-assisted aerogel interface engineering enables uniform Zn^(2+)flux and fast desolvation kinetics toward zinc metal batteries

The poor reversibility of Zn anodes induced by dendrite growth,surface passivation,and corrosion,severely hinders the practical applicability of Zn metal batteries.To address these issues,a plasmaassisted aerogel(PAG)interface engineering was proposed as efficient ion transport modulator that can simultaneously regulate uniform Zn^(2+)flux and desolvation behavior during battery operation.The PAG with ordered mesopores acted as an ion sieve to homogenize Zn deposition and accelerate Zn^(2+)flux,which is favorable for corrosion resistance and dendrite suppression.Importantly,the plasma-assisted aerogel with abundant hydrophilic groups can facilitate the desolvation kinetics of Zn^(2+)due to the multiple hydrogen-bonding interaction with the activated water molecules,thus accelerating the Zn^(2+)migration kinetics.Consequently,the Zn/Zn cell assembled with PAG-modified separator demonstrates stable plating and stripping behavior(over 1400 h at 1 mA cm^(-2))and high Coulombic efficiency(99.8%at1 mA cm^(-2)after 1100 cycles),and the Zn‖MnO_(2)full cell shows excellent long-term cycling stability and maintains a high capacity of 154.9 mA h g^(-1)after 1000 cycles at 1 A g^(-1).This study provides a feasible approach for the large-scale fabrication of aerogel functionalized separators to realize ultra-stable Zn metal batteries.

Investigation of Projectile Impact Behaviors of Graphene Aerogel Using Molecular Dynamics Simulations

Graphene aerogel(GA),as a novel solid material,has shown great potential in engineering applications due to its unique mechanical properties.In this study,the mechanical performance of GA under high-velocity projectile impacts is thoroughly investigated using full-atomic molecular dynamics(MD)simulations.The study results show that the porous structure and density are key factors determining the mechanical response of GA under impact loading.Specifically,the impact-induced penetration of the projectile leads to the collapse of the pore structure,causing stretching and subsequent rupture of covalent bonds in graphene sheets.Moreover,the effects of temperature on the mechanical performance of GA have been proven to be minimal,thereby highlighting the mechanical stability of GA over a wide range of temperatures.Finally,the energy absorption density(EAD)and energy absorption efficiency(EAE)metrics are adopted to assess the energy absorption capacity of GA during projectile penetration.The research findings of this work demonstrate the significant potential of GA for energy absorption applications.

Heteroatom tuning in agarose derived carbon aerogel for enhanced potassium ion multiple energy storage

The incorporation of heteroatoms into carbon aerogels(CAs)can lead to structural distortions and changes in active sites due to their smaller size and electronegativity compared to pure carbon.However,the evolution of the electronic structure from single-atom doping to heteroatom codoping in CAs has not yet been thoroughly investigated,and the impact of codoping on potassium ion(K+)storage and diffusion pathways as electrode material remains unclear.In this study,experimental and theoretical simulations were conducted to demonstrate that heteroatom codoping,composed of multiple heteroatoms(O/N/B)with different properties,has the potential to improve the electrical properties and stability of CAs compared to single-atom doping.Electronic states near the Fermi level have revealed that doping with O/N/B generates a greater number of active centers on adjacent carbon atoms than doping with O and O/N atoms.As a result of synergy with enhanced wetting ability(contact angle of 9.26°)derived from amino groups and hierarchical porous structure,ON-CA has the most optimized adsorption capacity(−1.62 eV)and diffusion barrier(0.12 eV)of K^(+).The optimal pathway of K^(+)in ON-CA is along the carbon ring with N or O doping.As K^(+)storage material for supercapacitors and ion batteries,it shows an outstanding specific capacity and capacitance,electrochemical stability,and rate performance.Especially,the assembled symmetrical K^(+)supercapacitor demonstrates an energy density of 51.8 Wh kg^(−1),an ultrahigh power density of 443Wkg^(−1),and outstanding cycling stability(maintaining 83.3%after 10,000 cycles in 1M KPF6 organic electrolyte).This research provides valuable insights into the design of highperformance potassium ion storage materials.

Theoretical study on the effective thermal conductivity of silica aerogels based on a cross-aligned and cubic pore model

Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, making them a new type of lightweight and highly efficient nanoscale super-insulating material. However, prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution. To investigate the internal heat transfer mechanism of aerogel nanoporous materials, this study constructed a cross-aligned and cubic pore model(CACPM) based on the actual pore arrangement of SiO_(2) aerogel. Based on the established CACPM, the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction, solid-phase heat conduction, and radiative heat transfer. The derived expression was then compared with available experimental data and the Wei structure model. The results indicate that, according to the model established in this study for the derived thermal conductivity formula of silica aerogel, for powdery silica aerogel under the conditions of T = 298 K, a_(2)= 0.85, D_(1)= 90 μm, ρ = 128 kg/m^(3), within the pressure range of 0–10^(5)Pa, the average deviation between the calculated values and experimental values is 10.51%. In the pressure range of 10^(3)–10^(4)Pa, the deviation between calculated values and experimental values is within 4%. Under these conditions, the model has certain reference value in engineering verification. This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.

rGO aerogel embedded with organic–inorganic hybrid perovskite for lightweight broadband electromagnetic wave absorption

Organic–inorganic hybrid perovskites are quite promising candidates in the field of electromagnetic wave (EMW) absorption due to their unique physicochemical properties. However, it is still a considerable challenge to satisfy the light weight, broad bandwidth, and strong absorption properties simultaneously. Herein, the solution of methylammonium lead iodide (MAPbI3) perovskites was infiltrated into the pores of reduced graphene oxide (rGO) aerogels. After drying, a series of MAPbI3/rGO composite aerogel (MGA) materials were synthesized by anchoring the MAPbI3 perovskite nanoparticles to rGO sheets with the assistance of rGO templates. Through the adjustment of component ratios, excellent EMW absorption properties are obtained with the synergistic effects of polarization loss, conduction loss, and multiple reflection and scattering of MAPbI3 and rGO. The porous structure of the aerogel and the suitable group distribution ratio allowed the MGA-4 samples to obtain excellent impedance matching and ultra-low density of ∼ 7.69 mg·cm−3. At a low filling ratio of 15 wt.%, the MGA-4 sample simultaneously achieves highly efficient and broadband EMW absorption performance at a thin thickness. The MGA-4 sample obtained a minimum reflection loss value of −64.35 dB and the effective absorption bandwidth (EAB) value of 5.4 GHz at a thickness of 2.08 mm and a maximum EAB (EABmax) value of 6.2 GHz under 2.22 mm. The MGA-5 sample obtained a maximum EAB value of 6.4 GHz with the thinckness of 2.16 mm. Furthermore, the simulation results of the radar cross-section (RCS) verified the component-optimized composites are capable of achieving excellent EMW attenuation. This paper provides a new approach and valuable reference for the development of hybrid perovskite-based microwave absorption materials with lightweight, ultra-broadband, and strong absorption properties.

Fabrication of amorphous nanoporous ZrO_(2)/SiO_(2) aerogel enabling nonlinear optical properties

Amorphous oxides have unique physicochemical properties with extensive opto-electronic applications such as the thin-film transistor,light-emitting diode backplanes,and supercontinuum generation.In this contribution,we synthesize the amorphous ZrO_(2)/SiO_(2) nanoporous aerogel with high structural integrity.With the femtosecond excitation laser at 800–1,064 nm,the broadband second harmonic generation is observed.The nonlinear optical properties of the as-prepared ZrO_(2)/SiO_(2) aerogel are investigated at 1.0μm and 1.5μm for the first time.Subsequently,the amorphous ZrO_(2)/SiO_(2) saturable absorber is originally applied in the Yb-doped and Er-doped fiber lasers to realize the mode-locking operations.In the Yb-doped fiber laser,the dissipative soliton resonance mode-locking operation is demonstrated with the largest pulse duration of 22 ns at a repetition rate of 7.8 MHz and a high signal-to-noise ratio of 64 dB.In the Er-doped fiber laser,a conventional soliton mod-locking regime is observed with an ultrashort pulse width of 960 fs,a repetition frequency of 6.55 MHz,and a time-bandwidth production of 0.347.Our work shows the good ability of the ZrO_(2)/SiO_(2) aerogel in generating ultrafast pulses and extends the saturable absorber into the amorphous material realm.

Building of lightweight Nb_(2)CT_(x) MXene@Co nitrogen-doped carbon nanosheet arrays@carbon fiber aerogels for high-efficiency electromagnetic wave absorption in X and Ku bands inspired by sea cucumber

The problems of electromagnetic wave(EMW)pollution in X and Ku bands(8–18 GHz)are becoming more and more serious.Therefore,it is urgent to design EMW absorbing materials with high-efficiency such as thin thickness,lightweight,wide bandwidth and strong EMW absorption.Inspired by the biomorph of sea cucumber,Nb_(2)CT_(x) MXene@Co nitrogen-doped carbon nanosheet arrays@carbon fiber aerogels(Nb_(2)CT_(x)@Co-NC@CFA,Nb_(2)CT_(x)=niobium carbide)were constructed by self-assembly,in-situ chemical deposition and subsequent pyrolysis.The carbon fiber aerogel,as the basic skeleton of sea cucumber,forms lightweight three-dimensional interconnected conductive network,enhances the dielectric loss and extends the multiple reflection and absorption paths of EMW.As the tentacles of sea cucumber surface,Nb_(2)CT_(x) MXene and Co nitrogen-doped carbon nanosheet arrays exist rich heterogeneous interfaces,which play an important role in improving EMW polarization loss and optimizing impedance matching.The minimum reflection loss(RLmin)of Nb_(2)CT_(x)@Co-NC@CFA reaches−54.7 dB at 9.84 GHz(2.36 mm)with a low filling ratio of 10 wt.%and the effective absorption bandwidth(EAB)of Nb_(2)CT_(x)@Co-NC@CFA reaches 2.96 GHz(8.48–11.44 GHz)with 2.36 mm and 5.2 GHz(12.8–18 GHz)with 1.6 mm,covering most of X and Ku bands by adjusting thickness.The radar cross section(RCS)value of Nb_(2)CT_(x)@Co-NC@CFA is 26.64 dB·m^(2),which is lower than that of the perfect electrical conductor(PEC),indicating that Nb_(2)CT_(x)@Co-NC@CFA can effectively decrease the probability of the target being detected by the radar detector.This work provides ideas for design and development of EMW absorbing materials with high-efficiency EMW absorption in X and Ku bands.