Controllable synthesis of mesoporous carbon hollow microsphere twined by CNT for enhanced microwave absorption performance

The low dielectric loss of mesoporous carbon hollow microsphere(PCHM)requires high filler loading(higher than 20 wt%)when it is used as microwave absorbers.In order to decrease the filler loading of PCHM,a new strategy for synergistic increase of polarization and conductive loss was developed by twining PCHM with carbon nanotube(CNT)according to theoretic calculation.By the optimization of CNT content,the minimum reflection coefficient was -34.6 dB with a filler loading of only 10 wt%,which was much lower than -2.1 dB of PCHM.In addition,the effective absorption bandwidth was 3.6 GHz at X band with a thickness of 2.8 mm.The enhanced microwave absorption performance can be ascribed to the unique combination of hollow PCHM and one-dimensional CNT with higher graphitization degree,leading to increase of conductivity and heterogeneous interfaces.As a result,the conductive loss increased from 0.12 to 2.27 and polarization loss increased from 0.15 to 0.67,achieving the balance between attenuation ability and impedance match.

Low Infrared Emissivity and Strong Stealth of Ti-Based MXenes

Advanced scenario-adaptable infrared(IR)stealth materials are crucial for creating localized closed thermal environments.Low emissivity over the broadest possible band is expected,as is superior mechanical deformability.Herein,we report a series of Ti-based MXenes with naturally low emissivity as ideal IR shielding materials.Over a wavelength ranging from 2.5 to 25μm,Ti_(3)C_(2)T_(X) film delivers an average emissivity of 0.057 with the lowest point of 0.042.Such a low emissivity coupled with outstanding structural shaping capability is beyond the current grasp.The reflection-dominated mechanism is dissected.Also,some intriguing scenarios of IR stealth for wearable electronic devices and skin thermal control are demonstrated.This finding lights an encouraging path toward next-generation IR shielding by the expanding MXene family.

Electromagnetic interference shielding Ti3C2Tx-bonded carbon black films with enhanced absorption performance

The demand for flexible and freestanding electromagnetic interference(EMI)shielding materials are more and more urgent to combat with serious electromagnetic(EM)radiation pollution.Twodimensional Ti3C2Tx is considered as promising EMI shielding material to graphenes because of the low cost and high electrical conductivity.However,the shielding performance still needs to be optimized to decrease the reflection effectiveness(SER)and increase absorption effectiveness(SEA).Herein,we prepared Ti3C2Tx-bonded carbon black films with a porous structure.The SER decreased from 20 dB to12 dB and the SEA increased from 31 dB to 47 dB.The best EMI shielding effectiveness can be as high as60 dB with SEA of 15 dB and SER of45 dB.Their calculated specific shielding effectiveness can be as high as8718 dB cm^2/g.These results indicate that the porous structure can enhance the absorption of the EMI shielding films,resulting from the enhanced scattering and reflectio n.Conseque ntly,this work provides a promising MXene-based EMI shielding film with lightweight and flexibility.

A SiC nanowires/Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8) ceramic heterojunction for stable electromagnetic absorption under variable-temperature

The application of semiconductor materials was limited as electromagnetic absorption materials,due to the unstable absorption performance caused by the temperature sensitivity.In this work,a structurally controllable ceramic heterojunction was developed by assembling structural units of SiC nanowires(SiCnws)and Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8)(BSAS).Benefiting from the optimization of the energy gap and the construction of heterogeneous interfaces,the ceramic heterojunction can achieve stable electromagnetic absorption from room temperature to 600℃,the effective absorption bandwidth is almost unchanged.And the minimum reflection loss value reached-63.6 dB at 600℃.Meanwhile,the SiCnws/BSAS ceramic heterojunction shows stable electromagnetic absorption performance in various simulated outdoor environments,including acid rain,seawater,high temperature and water vapor corrosion.This result provides a fire-new idea to realize the environmental adaptability of electromagnetic absorption materials and largely broadens its application prospect.