An Equivalent Substitute Strategy for Constructing 3D Ordered Porous Carbon Foams and Their Electromagnetic Attenuation Mechanism

Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.

Vibration and sound transmission loss characteristics of porous foam functionally graded sandwich panels in thermal environment

This study investigates the vibration and acoustic properties of porous foam functionally graded(FG)plates under the influence of the temperature field.The dynamics equations of the system are established based on Hamilton's principle by using the higher-order shear deformation theory under the linear displacement-strain assumption.The displacement shape function is assumed according to the four-sided simply-supported(SSSS)boundary condition,and the characteristic equations of the system are derived by combining the motion control equations.The theoretical model of vibro-acoustic coupling is established by using the acoustic theory and fluid-structure coupling solution method under the simple harmonic acoustic wave.The system's natural frequency and sound transmission loss(STL)are obtained through programming calculations and compared with the literature and COMSOL simulation to verify the validity and reliability of the theoretical model.The effects of various factors,such as temperature,porosity coefficients,gradient index,core thickness,width-to-thickness ratio on the vibration,and STL characteristics of the system,are discussed.The results provide a theoretical basis for the application of porous foam FG plates in engineering to optimize vibration and sound transmission properties.

Non-enzymatic Glucose Sensor Based on Porous Foam Au/MXene Nanocomposites

A novel electrochemical non-enzymatic glucose sensor based on three-dimensional Au/MXene nanocomposites was developed.MXenes were prepared using the mild etched method,and the porous foam of Au nanoparticles was combined with the MXene by means of in situ synthesis.By controlling the mass of MXene in the synthesis process,porous foam with Au nanoparticles was obtained.The three-dimensional foam structure of nanoparticles was confirmed by scanning electron microscopy.Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the electrochemical performance of the Au/MXene nanocomposites.The Au/MXene nanocomposites acted as a fast redox probe for nonenzymatic glucose oxidation and showed good performance,including a high sensitivity of 22.45μA·(mmol/L)^(-1)·cm^(-1)and a wide linear range of 1-12 mmol/L.Studies have shown that MXene as a catalyst-supported material is beneficial to enhance the conductivity of electrons and increase the loading rate of the catalyst materials.The foam structure with Au nanoparticles can provide a larger surface area,increase the contact area with the molecule in the catalytic reaction,and enhance the electrochemical reaction signal.In summary,this study shows that Au/MXene nanoparticles have the potential to be used in non-enzymatic glucose sensors.

High-performance wearable bimetallic nanowire-assisted composite foams for efficient electromagnetic interference shielding,infrared stealth,and piezoresistive sensing

With the accelerated development of modern detection and communication technology,the multifunctional wearable materials with excellent electromagnetic interference(EMI)shielding,infrared stealth,and human monitoring for improving military combat capability have received extensive attention.In this work,the lightweight melamine foam(MF)@silver nanowires(AgNWs)-iron nanowires(FeNWs)(AgFe-MF)was fabricated by a vacuum-assisted dip-coating method.Due to the porous structure and synergistic electrical and magnetic losses,this lightweight(0.115 g/cm^(3))composite foam with an ultra-low filler content(0.62 vol.%)exhibited an ideal EMI shielding efficiency of 38.4 dB.On the other hand,the AgFe-MF realized a powerful multifunctional integration.The surface saturation temperature of the AgFe-MF reached 94.2℃under a low applied voltage of 1.8 V and remained extremely fast heating and cooling response and terrific working stability,resulting in excellent infrared stealth and camouflage effects.Furthermore,taking virtues of the elastic porous conductive architecture,the AgFe-MF was utilized as a piezoresistive sensor exhibiting board compressive interval of 0–1.62 kPa(50%strain)with a good sensitivity of 0.57 kPa^(−1).This work will provide new ideas and insights for developing multifunctional wearable devices in the fields of EMI shielding,thermal management,and piezoresistive sensing.

Edge sulfurized graphene nanoplatelets via vacuum mechano-chemical reaction for lithium–sulfur batteries

Lithium–sulfur batteries have great potential for high energy applications due to their high capacities,low cost and eco-friendliness. However, the particularly rapid capacity decay owing to the dissolution and diffusion of polysulfide intermediate into the electrolyte still hamper their practical applications.And the reported preparation procedures to sulfur based cathode materials are often complex, and hence are rather difficult to produce at large scale. Here, we report a simple mechano-chemical sulfurization methodology in vacuum environment applying ball-milling method combined both the chemical and physical interaction for the one-pot synthesis of edge-sulfurized grapheme nanoplatelets with 3D porous foam structure as cathode materials. The optimal sample of 70%S–Gn Ps-48 h(ball-milled 48 h) obtains 13.2 wt% sulfur that chemically bonded onto the edge of Gn Ps. And the assembled batteries exhibit high initial discharge capacities of 1089 mAh/g at 0.1 C and 950 mAh/g at 0.5 C, and retain a stable discharge capacity of 776 mAh/g after 250 cycles at 0.5 C with a high Coulombic efficiency of over 98%. The excellent performance is mainly attributed to the mechano-chemical interaction between sulfur and grapheme nanoplatelets. This definitely triggers the currently extensive research in lithium–sulfur battery area.

Flexible and breathable 3D porous SSE/MXene foam towards impact/electromagnetic interference/bacteria multiple protection performance for intelligent wearable devices

As intelligent wearable devices,they will inevitably be subjected to various damages and disturbances from the external environment during daily use.Therefore,it is urgent to develop safeguarding materials with multiple protective properties.Herein,this work developed a flexible and breathable three-dimensional(3D)porous shear stiffening elastomer(SSE)/MXene(M-SSE)foam with impact/electromagnetic interference(EMI)/bacteria multiple protection performance for intelligent wearable devices.The continuous conductive MXene network in the 3D SSE porous structure made M-SSE foam exhibit excellent electromagnetic interference shielding property with a high shielding effectiveness of 34 dB.Attributed to the shear stiffening effect of porous SSE matrix,M-SSE foam possessed unique anti-impact and protection properties.The energy dissipation rate reached up to more than 85%,illustrating M-SSE foam could effectively attenuate the external impact force and absorb the impact energy.Inherited from the excellent photothermal performance of MXene,M-SSE foam achieved a considerable saturated temperature of 98℃ under 0.57 W/cm^(2) laser power.Therefore,M-SSE foam showed extraordinary antimicrobial property for Staphylococcus aureus according to the principle of photothermal sterilization.Finally,for the development of intelligent wearable devices,conductive MSSE foam could be used as an intelligent sensor to monitor various human movements owing to the highly sensitive property.This work greatly expanded the application prospect of multifunctional protective materials in various complex environments and promoted the development of multifunctional smart wearable devices in protection field.

Microwave-assisted synthesis of Cr_(3)C_(2)@C core shell structure anchored on hierarchical porous carbon foam for enhanced polysulfide adsorption in Li-S batteries

In this paper,we use microwave reduction strategy to synthesize a new bi-functional sulfur host material at the service of cathode substrate for lithium-sulfur batteries(LSBs),the composite is made of hierarchical porous carbon foam supported carbon-encapsulated chromium carbide nano-particles(Cr_(3)C_(2)@C/HPCF),in which the well-distributed conductive Cr_(3)C_(2) nano-particles can act as powerful chemical adsorbent and are effective in restraining the shuttle effect of lithium polysulfides(LiPSs).Test results show that the Cr_(3)C_(2)@C/HPCF based sulfur electrodes with 75 wt.%of sulfur exhibit a high initial discharging capacity of 1,321.1 mAh·g^(−1) at 0.1 C(3.5 mg·cm^(−2)),and a reversible capacity can still maintain stability at 1,002.1 mAh·g^(−1) after 150 cycles.Even increasing the areal sulfur loading to 4 mg·cm^(−2),the electrodes can still deliver an initial discharging capacity of 948.0 mAh·g^(−1) at 0.5 C with ultra-slow capacity decay rate of 0.075%per cycle during 500 cycles.Furthermore,the adsorption energy between the Cr_(3)C_(2) surface and LiPSs as well as theoretic analysis based on first-principles is also investigated.

一体式自漂浮多孔泡沫作为隔热层用于高效光热转换和太阳能脱盐

本文通过冷冻干燥铸造成型和高温表面氢化策略,构筑了一种自漂浮等离子体Ag/黑色TiO_(2)/碳多孔层状泡沫(Ag-BTCFs)作为高效的太阳能热集流体.这种一体式三维(3D)交联自漂浮多孔层状泡沫材料可以实现全光谱吸收(~95.45%),并有效地阻止热量向下层水体传导.Ag-BTCFs受益于光照射下Ag的局域表面等离子体效应驱动的“热点”效应,促进了光生热电子(e^(-))和光生空穴(h^(+))在等离子体辅助半导体中的传输.此外,具有亲水性的黑色TiO_(2)可以作为水的传输介质.与层状碳泡沫的耦合不仅提高了材料的吸收率,而且促进了热电子的弛豫和集热.更重要的是,光生h~+被用来光催化降解污染物,在不影响蒸汽产生效率的情况下实现了降解污染物和淡水生产的同步进行,这种高效的新型轻质自漂浮Ag-BTCFs将在太阳能蒸汽发电和海水淡化中具有潜在的应用前景.

3D shape-stable temperature-regulated macro-encapsulated phase change material:KAl(SO_(4))_(2)·12H_(2)O-C_(2)H_(2)O_(4)·2H_(2)O-CO(NH_(2))_(2) eutectic/polyurethane foam as core and carbon modified silicone resin as shell

Micro-encapsulated phase change materials(PCMs)have been confirmed a high-efficiency way to store latent heat,but their poor mechanical properties,expensive and complicated synthesis block their industrial application.Herein,borrowing from this structure and magnifying it,we prepared a novel 3D shape-stable temperature-regulated macro-encapsulated PCMs.The KAl(SO_(4))_(2)·12H_(2)O-C_(2)H_(2)O_(4)·2H_(2)O-CO(NH_(2))_(2)(APSD-OAD-Urea)was configured as PCM to composite with light-weight porous polyurethane foam(PUF)framework,and the enthalpy reduction of PCM@PUF(core)was only 1.70%.Subsequent,carbon modified silicone resin(CMS,shell)was introduced to macro-encapsulate PCM@PUF.The results showed that with the optimized mass ratio of 75%APSD-25%OAD and extra addition of 10% Urea,the obtained PCM had a relatively high enthalpy(194.6 J/g),appropriate phase transition temperature(42.17℃)and suppressed supercooling(0.504℃).CMS thin-layer with 2.0 mm thickness increased resistance to deformation,impressions,scratches,and possessed a brilliant sealing effect on PCM@PUF to achieve leak-free and operation steady of PCM.PCM@PUF@CMS with low thermal conductivity from inside out displayed an outstanding thermal insulation performance.Moreover,the fluctuation of the thermodynamic property after 150 thermal cycles is relatively small.All these above enable the application of PCM@PUF@CMS in the thermal energy storage system and provide a novel strategy for the preparation of macro-encapsulated PCMs.

X-ray computed tomography of adhesive wicking into carbon foam

Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography(CT)and image processing software have been utilized. Two different laser target configurations have been assessed in situ and volume rendered images of the distribution and quantities of adhesive have been determined for each.

Chitosan foam reinforced by SiC whisker for building insulation with high mechanical strength and vapor permeability

Porous foam based on renewable materials has attracted extensive attention in green energy conservation and sustainable development.However,there is still a requisite for biomass-based porous foam that could meet the demand for excellent mechanical and high thermal insulation performances for building insulation.Herein,we demonstrated a facile strategy to prepare a porous foam made from a chitosan matrix reinforced by SiC whisker,which shows good performance in building insulation and mechanical strength.The prepared porous foam has a low density(20.1–54.4 kg m^(-3))and high porosity(>97.0%).The density of the chitosan-SiC porous foam can be controlled by varying the suspension solid and SiC whisker content in the preparation process.Furthermore,the influences of SiC whisker content on the mechanical properties and thermal conductivity of the porous foams were also investigated.When the content of SiC whisker is 30 wt%,the prepared porous foam has the highest compression modulus of about 89.8 kPa and also low thermal conductivity of 0.0354 W m^(-1)K^(-1).Moreover,the prepared porous foam shows excellent water vapor permeability with a vapor resistance factor of 2.94,which is beneficial for moisture transfer in buildings.This work provides a facile way to manufacture biomass-based porous foam,which is potential for energy saving in buildings.