查看更多>>摘要：With the discovery of the two-dimensional(2D)MXene,it shows a great application potential in the field of electromagnetic interference(EMI)shielding,but the mechanical brittleness and easy oxidation of MXene limit its wide application.For this reason,a double crosslinking strategy is provided to solve the above problems in a nacre-like"brick-mortar"layered MXene/cellulose nanofiber(MXene/CNF)film.Typically,the film was firstly suffered by dopamine modification,then was further reinforced by sec-ondary Ca2+bridging,so as to obtain excellent mechanical properties and antioxidative EMI shielding performance.Comparing with the single crosslinking,the double crosslinking strategy reveals a higher efficiency in improving the mechanical property.The mechanical strength and toughness of the dou-ble crosslinking MXene/CNF film can increase to 142.2 MPa and 9.48 MJ/m3,respectively.More impor-tantly,while achieving good mechanical properties,the MXene composite film still holds a very stable EMI shielding performance of more than 44.6 dB when suffering from the oxidation treatment of high-temperature annealing,showing excellent anti-oxidation ability and environment tolerance.Therefore,this work provides a universal but effective double crosslinking strategy to solve the mechanical brit-tleness and easy oxidation of MXene-based composites,thus showing a huge potential in flexible EMI shielding applications.
查看更多>>摘要：Long period stacking ordered(LPSO)structures are an effective strengthening phase in Mg alloys.How-ever,the coarse LPSO phases in as-cast alloys are very difficult to refine,and they dramatically reduce the strengthening effect.In the present study,friction stir processing(FSP)was employed to refine the structure of an Mg-12.8Y-4.7Zn(wt％)alloy with a very high content of coarse LPSO phases.An opti-mized FSP regime refined the coarse LPSO phases into densely ultrafine blocks with an average width of～200 nm and an average length of～1 μm.An ultrahigh yield strength of～800 MPa was achieved under compression of the FSP region.Theoretical calculations indicated that the strengthening by the densely ultrafine LPSO phases was up to approximately 630 MPa.
查看更多>>摘要：In recent years,graphene has been widely employed in the field of metal corrosion protection owing to its outstanding impermeability and chemical stability,with examples of such metal protection including pure graphene coatings and graphene-based composite coatings.But the conductive graphene could pro-mote the electrochemical reaction at the interface and accelerate the corrosion of metal substrates.More emerging graphene-like 2D nanosheets are attracting research attention for the application of metal anti-corrosion,because of their barrier properties and poor conductivity,mainly including boron nitride(BN),molybdenum disulfide(MoS2),zirconium phosphate(ZrP),and titanium carbide(MXene).In this review,the application of these graphene-like 2D nanosheets to metal protection is comprehensively reviewed.First,the general preparation methods of 2D nanosheets are briefly introduced.Second,surface func-tionalization of 2D nanosheets,including covalent and non-covalent modification,is described in detail.Third,the anticorrosion performance and optimization measures of pure 2D nanosheets coatings are sum-marized.Next,the protection performance,anticorrosive mechanism,and optimizations of 2D nanosheets composite coatings are presented.Finally,the future development of 2D nanosheets-based anticorrosive coatings has been prospected,and the challenges in the industrial application are discussed.
查看更多>>摘要：Carbon nanotubes(CNTs)are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfCNWs)through thermal pyrolysis of Hf-containing polymer precursor.The formed HfCNWs are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C)com-posites and display perfect single crystal appearance.The pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfCNWs.The released waste gasses containing CO,CH4 and CO2 are the main carbon source for the growth of CNTs.Specifically,the flexural strength of HfCNWs reinforced carbon/carbon(HfCNWs-C/C)composites is enhanced by～105％compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to ca-pacitor applications.The present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.
查看更多>>摘要：The construction of scintillating ceramics is of great technological importance for various fundamental ap-plications,including medical diagnostic,security inspection,resource exploration and particle physics.The chief challenge is the facile and scalable synthesis of scintillating ceramics with the desirable combina-tion of pore-free,reliable mechanical properties and excellent scintillating performance.Here we present a pressureless glass crystallization strategy for the construction of scintillating composite with high crys-tallinity.The fabricated scintillating composites are featured by small optical turbidity,excellent mechani-cal properties,and efficient scintillating luminescence with the scintillating light yield of 15,000 pH/MeV and about 2.46 times higher than that of the commercial BGO single crystal.Moreover,the scintillat-ing composite derived radiation detector device is successfully elaborated.The practical application for monitoring gamma ray is demonstrated and the precision of the device is less than that of the tolerable deviation of 30％.Our results suggest an innovative approach for expanding the category of scintillating material candidates,pointing to practical application in the field of radiation detection.
查看更多>>摘要：Flexible,lightweight,robust and versatile properties are essential for the next generation of wearable as well as intelligent electromagnetic interference(EMI)shielding materials.In this work,multilayered films containing cellulose nanofiber(CNF)layers,CNF/MXene layers,and CNF/silver nanowires(CNF/AgNWs)layers were fabricated by an efficient and easy-to-use vacuum filtration method.Compared with a uni-formly mixed film,the resultant layered composite films that loaded with a low MXene and AgNWs content exhibit superior mechanical properties with a tensile strength of 137 MPa,a strain at break of 5.7％,excellent EMI shielding effectiveness(EMI SE)of 61.9 dB,and higher EMI SE/t of 20,653 dB cm-1.This is attributed to the high-performance CNF substrate,the highly efficient layered structures,and ex-tensive hydrogen-bonding interactions.In particular,a high degree of ohmic loss of multiple interfaces and polarization relaxation of local defects,as well as an abundance of terminal groups,favor the loss of electromagnetic waves(EMW)within the material.In addition,the prepared multifunctional layered composite films also show good antibacterial properties.As a result,the obtained new kind of flexible layered structure EMI shielding composite films with excellent EMI shielding performance,and mechan-ical properties present promising application prospects in the fields of EMI shielding and protection for aerospace,portable,and wearable flexible electronic devices.
查看更多>>摘要：This study proposed a strategy for effectively diminishing the carrier concentration in Cu2Te by introduc-ing graphene sheets.Based on thermoelectric property measurements and single parabolic band mod-eling,the incorporated graphene effectively reduced the carrier concentration,not only enhancing the thermoelectric performance of the Cu2Te/graphene composite but also substantially improving its figure of merit up to～1.47 at 1000 K,which is 268％higher than that of pristine Cu2Te.This study gives an insight into the control of carrier concentration and thermoelectric properties in Cu2Te,and it could be extended to other copper chalcogenides for excellent thermoelectrics.
查看更多>>摘要：Herein,a low-cost,biodegradable,and high-performance microwave shielding graphite/starch mate-rial was fabricated via constructing a cation-π interaction between ammonium ions and graphite.The graphite flakes and starch were firstly mixed with distilled water containing ammonium hydroxide to form graphite/starch slurry under an ultrasonic assistant.The cation-π interaction could improve delam-ination degree and dispersion of graphite in starch matrix.The slurry was first used as a coating material on the surface of wood and paper to develop shielding packages.The effect of coating thickness and coating layers on EM shielding property of the materials was investigated.Second,the composites with a high orientation of graphite were fabricated by compression at high pressures.The electrical conductivity and EM shielding effectiveness(SET)of the materials were greatly enhanced by construction of cation-πinteraction and orientation of graphite.Specifically,the EM SET values increased from 56.9 to 66.8 dB for the composites with 50 wt.％graphite and 2.0 mm in thickness by constructing cation-π interaction.The EM SET values raised from 17.4 to 66.8 dB via the graphite orientation in the materials with the same components and thickness.The shielding mechanism of the compressed composites with orientation dis-persion of graphite was also discussed in comparison to the coating layer with random dispersion of graphite.
查看更多>>摘要：A highly efficient absorber with features including lightweight,broad bandwidth,and tunable elec-tromagnetic property still remains challenging for practical applications.Herein,the Porphyra-derived porous carbon(PPC)was fabricated via facile procedures of low-temperature pre-carbonization combined with KOH chemical activation.The composition,microstructure,and electromagnetic wave absorption properties of the samples were elucidated based on X-ray diffraction(XRD),Raman,X-ray photoelec-tron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Brunauer-Emmer-Teller(BET),and vector network analyzer(VNA).The porosity of PPC can be readily regulated by adjusting activation temperature.The PPC obtained at 750℃was composed of a three-dimensional hierarchically porous carbon network.The C and N elements of natural Porphyra were intro-duced into the carbon skeleton during the carbonization process.The large specific surface,dopants,and three-dimensional hierarchically porous carbon network can effectively improve the impedance matching and dielectric dissipation,leading to an excellent electromagnetic wave absorption performance.Espe-cially,the optimal reflection loss(RL)value reached-57.75 dB at 9.68 GHz with a broad bandwidth(RL＜-10 dB)value of 7.60 GHz at 3.5 mm.Overall,the results indicate that the PPC can provide a new way to achieve lightweight,effective,and sustainable absorbers.
查看更多>>摘要：Exploring an advanced and efficient electromagnetic(EM)wave absorbing material by improving dielec-tric loss capacity and adjusting impendence matching is crucial yet challenging.Herein,the bacterial cellulose(BC)derived carbon aerogel(CA)with a robust nanofibrous network was used as a conduc-tive loss scaffold to dissipate EM waves effectively,and the ZnO microparticles with excellent dielectric properties and low electrical conductivity were decorated on the scaffold to adjust dielectric parameters and impedance matching adequately.By using different zinc precursors,the tunable size and morpholo-gies of ZnO crystals were obtained due to the growth rate of different crystallographic,including flower-like,nanorod like,and cauliflower-like morphologies,which is beneficial to strong multiple reflections,intensive interfacial polarization,better impendence matching,as well as excellent maintenance of the hierarchical structure.Owing to the appropriate impendence matching and the considerable EM wave dissipation,the CA@ZnO composites achieve a superior EM absorbing performance with a broad effective absorbing bandwidth(whole X band)and a minimum reflection coefficient(-53.3 dB).This work paves a new way for developing lightweight and highly efficient EM absorbing materials comprising the carbon scaffold and semiconductor microparticles.
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