[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broad...[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.展开更多
The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks...The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti_(3)C_(2)Tx nanosheets through electrostatic self-assembly.The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti_(3)C_(2)Tx nanoflakes.Based on the synergistic e ectsof multi-components and special well-constructed structure,NiCo layered double hydroxides@Ti_(3)C_(2)Tx(LDHT-9)absorber remarkably achieves unexpected e ective absorption bandwidth(EAB)of 6.72 GHz with a thickness of 2.10 mm,covering the entire Ku-band.After calcination,transition metal oxide@Ti_(3)C_(2)Tx(TMOT-21)absorber near the percolation threshold possesses minimum reflection loss(RLmin)value of-67.22 dB at 1.70 mm within a filler loading of only 5 wt%.This work enlightens a simple strategy for constructing MXene-based composites to achieve high-e cient microwave absorbents with lightweight and tunable EAB.展开更多
Duplex-structured Mg-7Li-2Al-1.5Sn alloys with high strength were fabricated and their strengthening mechanism was investigated.The Mg-7Li-2Al-1.5Sn alloys were prepared by casting and extruded at the temperature of 5...Duplex-structured Mg-7Li-2Al-1.5Sn alloys with high strength were fabricated and their strengthening mechanism was investigated.The Mg-7Li-2Al-1.5Sn alloys were prepared by casting and extruded at the temperature of 533 K with an extrusion ratio of 25:1.The microstructure and mechanical properties of Mg-7Li-2Al-1.5Sn alloys were systematically investigated by OM,XRD,SEM,TEM,and tensile tests.The results show that Mg-7Li-2Al-1.5Sn alloys are mainly composed ofα-Mg,β-Li,LiMgAl_(2),Mg_(2)Sn and Li_(2)MgSn phases.The yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)of the extruded alloy at room temperature reach 250 MPa,324 MPa and 11.9%,respectively.A lot of Sn-rich precipitates(Mg_(2)Sn and Li_(2)MgSn)are precipitated during extrusion with an average size of∼14 nm,which is beneficial to the grain refinement.Dynamic recrystallization occurs during hot deformation and the nanoprecipitates effectively refine the dynamic recrystallized(DRXed)grains.Besides,the residual dislocations existed in DRXed and un-DRXed grains result in the dislocation strengthening in the extruded alloy.Mg7Li-2Al-1.5Sn alloys possess excellent high-temperature mechanical properties with the YS,UTS and EL of 200 MPa,237 MPa and 26.7%at 423 K,respectively.Sn-rich precipitates with good thermal stability can effectively prevent grain growth,which is good for the improvement of the high-temperature performance of Mg-Li-Al-Sn alloy.展开更多
The pursuit to mimic skin exteroceptive ability has motivated the endeavors for epidermal artificial mechanoreceptors.Artificial mechanoreceptors are required to be highly sensitive to capture imperceptible skin defor...The pursuit to mimic skin exteroceptive ability has motivated the endeavors for epidermal artificial mechanoreceptors.Artificial mechanoreceptors are required to be highly sensitive to capture imperceptible skin deformations and preferably to be self-powered,breathable,lightweight and deformable to satisfy the prolonged wearing demands.It is still struggling to achieve these traits in single device,as it remains difficult to minimize device architecture without sacrificing the sensitivity or stability.In this article,we present an all-fiber iontronic triboelectric mechanoreceptor(ITM)to fully tackle these challenges,enabled by the high-output mechano-to-electrical energy conversion.The proposed ITM is ultralight,breathable and stretchable and is quite stable under various mechanical deformations.On the one hand,the ITM can achieve a superior instantaneous power density;on the other hand,the ITM shows excellent sensitivity serving as epidermal sensors.Precise health status monitoring is readily implemented by the ITM calibrating by detecting vital signals and physical activities of human bodies.The ITM can also realize acoustic-to-electrical conversion and distinguish voices from different people,and biometric application as a noise dosimeter is demonstrated.The ITM therefore is believed to open new sights in epidermal electronics and skin prosthesis fields.展开更多
Lithium-sulfur batteries as one of the most promising next-generation high-energy storage system, the shuttle effect, the expansion of cathode and the slow electrode redox kinetics limit its further development. Herei...Lithium-sulfur batteries as one of the most promising next-generation high-energy storage system, the shuttle effect, the expansion of cathode and the slow electrode redox kinetics limit its further development. Herein, we report a two-dimensional, ultrathin and ultra-light bimetal-Ni Co-organic framework as the interlayer for Li-S batteries. This kind of interlayer can effectively block polysulfides and accelerate the conversion with a thickness of only 1 μm and a load of 0.1 mg/cm^(2). Because the MOF nanosheets with a thickness of a few nanometers have a large specific surface and a large number of exposed accessible active sites. At the same time, the intrinsic activity of each site is enhanced and the catalytic performance is improved due to the synergistic effect of mixed metals and the unique coordination environment around the active sites. So, 2D NiCo MOF/CNT totally meets the requirements for the lightweight and effective interlayer. The initial discharge capacity of cell with 2D NiCo MOF/CNT interlayer can reach 1132.7 m Ah/g at 0.5 C. It remained 709.1 m Ah/g after 300 cycles, showing good cycling stability and rate performance.展开更多
For electromagnetic wave-absorbing materials,maximizing absorption at a specific frequency has been constantly achieved,but enhancing the absorption properties in the entire band remains a challenge.In this work,a 3D ...For electromagnetic wave-absorbing materials,maximizing absorption at a specific frequency has been constantly achieved,but enhancing the absorption properties in the entire band remains a challenge.In this work,a 3D porous pyrolytic carbon(PyC)foam matrix was synthesized by a template method.Amorphous carbon nanotubes(CNTs)were then in-situ grown on the matrix surface to obtain ultralight CNTs/Py C foam.These in-situ grown amorphous CNTs were distributed uniformly and controlled by the catalytic growth time and can enhance the interface polarization and conduction loss of composites.When the electromagnetic wave enters the internal holes,the electromagnetic energy can be completely attenuated under the combined action of polarization,conductivity loss,and multiple reflections.The ultralight CNTs/Py C foam had a density of 22.0 mg·cm^(-3)and a reflection coefficient lower than-13.3 d B in the whole X-band(8.2-12.4 GHz),which is better than the conventional standard of effective absorption bandwidth(≤-10 dB).The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in the X-band.展开更多
Lightweight materials with wide absorption capabilities,particularly in the C-band,have remained a challenge thus far.Recent research has indicated that effective absorption networks built by microfiber polarization l...Lightweight materials with wide absorption capabilities,particularly in the C-band,have remained a challenge thus far.Recent research has indicated that effective absorption networks built by microfiber polarization loss can be a significant factor in increasing the effective absorption bandwidth(EAB).In this study,leaf vein-like carbon(LVC)was synthesized using an in situ blowing strategy.Taking inspiration from photosynthesis energy conversion mechanisms,a leaf veins-like hierarchical structure was created to establish an effective impedance-matching network and generate a high-density polarization region through leaf vein microfibers.This enhanced polarization relaxation effectively broadens the EAB of the LVC.At a low filling ratio of 6.3 wt%,the EAB of the LVC covers 80%of the C-band,as well as100%of the X-band and Ku-band.Achieving such a wide EAB in the C-band,especially in the multi-band context,relies on impedance matching and optimized polarization relaxation.This work demonstrates the crucial role of leaf vein micronetwork engineering in enhancing the C-band absorption properties of carbon-based materials,thus providing a viable reference for the development of lightweight,broadband,and highly absorptive materials for electromagnetic applications.展开更多
High-strength Fe-Mn-Al-C-Ni low-density steels are highly desirable in lightweight transportation,safe infrastructure,and advanced energy applications.However,these steels generally suffer from limited ductility owing...High-strength Fe-Mn-Al-C-Ni low-density steels are highly desirable in lightweight transportation,safe infrastructure,and advanced energy applications.However,these steels generally suffer from limited ductility owing to the formation of coarse B2 particles at grain boundaries.In this study,we proposed a strategy to introduce copious intragranular B2 nanoprecipitates within fully-recrystallized fine austenitic grains in a Fe-26Mn-11Al-0.9C-5Ni ultralight steel by a simple cold rolling and annealing process.Compared with steel where B2 particles are mainly distributed at grain boundaries,the yield strength and ultimate tensile strength of this steel increased from 768 MPa and 1100 MPa to 954 MPa and 1337 MPa,respectively,whereas the total elongation increased from 38%to 50%.The higher yield strength was primarily due to the synergistic strengthening effect of intragranular B2 nanoprecipitates and grain refinement.The excellent ductility and sustained work hardening were mainly attributed to the strong dislocation storage capability mediated by the intragranular B2 nanoprecipitates and the greater dynamic slip band refinement strengthening effect.Hence,the achievement of copious intragranular B2 nanoprecipitation in fully recrystallized ultralight steel offers an effective pathway for developing lightweight materials with high strength and large ductility.展开更多
Improving cell-level gravimetric and volumetric energy density is essential to achieve high-performance batteries in the rapidly evolving field of energy storage technology,which requires consideration of all cell com...Improving cell-level gravimetric and volumetric energy density is essential to achieve high-performance batteries in the rapidly evolving field of energy storage technology,which requires consideration of all cell components.Traditional current collectors(CCs)made of metal foil,especially the copper(Cu)current collector of the anode,possess high mass and cost yet do not contribute to capacity.Reducing the weight of Cu CC with minimum thickness and desirable mechanical strength is critical in enhancing energy density but is technically challenging.Herein,we demonstrate a fast and scalable chemical coating method based on electroless plating for fabricating ultralight CC(∼1.72mg cm^(−2))with a thin Cu layer(500nm)on an ultrathin polyethylene(PE)polymer scaffold(5μm).The ultralight and ultrathin CC possesses high metal purity,high mechanical strength,high thermal stability,and outstanding electrochemical performances in lithium-ion and lithium-metal battery systems.Our ultralight CC only exhibits∼30% of the weight of 6μm Cu foil,leading to a 5−10% improvement in cell-level gravimetric energy density without sacrificing volumetric energy density.Moreover,the simplicity and scalability of the chemical coating method make it a promising solution for the mass production of ultra-thin and lightweight current collectors.展开更多
Ultrathin(thickness less than 10μm)and ultralight flexible perovskite solar cells(FPSCs)have attracted extensive research enthusiasm as power sources for specific potential lightweight applications,such as drones,bli...Ultrathin(thickness less than 10μm)and ultralight flexible perovskite solar cells(FPSCs)have attracted extensive research enthusiasm as power sources for specific potential lightweight applications,such as drones,blimps,weather balloons and avionics.Currently,there is still a certain gap between the power conversion efficiency(PCE)of ultrathin FPSCs and common FPSCs.This study demonstrates ultrathin FPSCs on 3-μm-thick parylene-C substrates via a flip-over transferring process.The Zr,Ti and Ga-doped indium oxide(ITGZO)film is employed as the bottom transparent electrode of ultrathin inverted FPSCs with a remarkable PCE of 20.2%,which is comparable to that based on common FPSCs.Devices on glasses and parylene-F(i.e.,parylene-VT4)substrates were also constructed to verify the advantages of parylene-C.Furthermore,an excellent powerper-weight of 30.3 W g^(-1) is achieved attributed to remarkable PCE and ultrathin-ultralight substrates,demonstrating the great promise of fabricating efficient,ultrathin and ultralight solar cells with parylene-C films.展开更多
美国材料实验协会(American Society of Testing Materials,ASTM)F2052-21标准(对应中文标准YY/T 0987.2)规定了磁共振环境中医疗器械磁致位移力的标准测试方法,在国际上被广泛接受和应用。该方法是用细线将被测植入物悬挂于磁场中,测...美国材料实验协会(American Society of Testing Materials,ASTM)F2052-21标准(对应中文标准YY/T 0987.2)规定了磁共振环境中医疗器械磁致位移力的标准测试方法,在国际上被广泛接受和应用。该方法是用细线将被测植入物悬挂于磁场中,测量悬线相对竖直方向的偏转角,从而计算磁致位移力相对重力的大小。然而,当该方法应用于极轻型植入物测试时,很难满足悬线质量小于植入物质量的1%的要求。该文提出了一种基于配重修正的极轻型植入物磁致位移力测试方法:使用质量超出待测植入物质量的1%的悬线和夹持物,按照标准方法测量偏转角度,再使用待测植入物质量在被测物总质量中的占比对偏转角度进行修正,从而获得准确的测量结果。该文对配重修正法进行了理论计算和实验验证,结果表明,所提出的配重修正法能够有效测量极轻型植入物的磁致位移力偏转角。展开更多
基金National Natural Science Foundation of China (52371171, 52222106, 51971008, 52121001)Fund of National Key Laboratory of Scattering and Radiation (Beijing Institute of Environmental Features)。
文摘[Background and purposes]In recent years,there has been growing attention in academia and industry on the development of high-performance electromagnetic wave(EMW)absorbing materials.However,creating lightweight broadband absorbers remains a challenge in terms of practical applications.EMW absorbing materials primarily rely on the magnetic loss of magnetic materials and/or the dielectric loss of dielectric materials to convert EMW energy into thermal energy for dissipation.Among various magnetic materials,Fe_(3)O_(4) plays an irreplaceable role in EMW absorption due to its high saturation magnetization,low cost and compatible dielectric loss in the gigahertz frequency range.Nevertheless,the high density,large matching thickness and narrow absorption bandwidth of Fe_(3)O_(4) pose significant challenges for practical applications.In contrast,one-dimensional(1D)structures not only retain the characteristic properties of lightweight,chemical stability and high dielectric loss,but also exhibit anisotropic structures and large aspect ratios.Additionally,researchers have found that the minimum reflection loss(RL)of hollow carbon materials with mesopores is nearly four times that of non-porous hollow carbon materials and nine times that of dense carbon materials.According to Maxwell's EMW theory,composites consisting of Fe_(3)O_(4) and one-dimensional(1D)mesoporous carbon materials can leverage their respective advantages by optimizing the composition and structure of the composites to balance u,and Er,thereby enhancing EMW absorption performance.Additionally,numerous studies have demonstrated that composites composed of multi-component heterostructures significantly enhance the EAB.This enhancement is primarily ascribed to the numerous interface polarization losses generated by the additional heterostructure interfaces,which also improve the overall impedance matching of the composites.In this study,we leverage the advantages of magnetic/carbon composites,one-dimensional(1D)mesoporous carbon and multi-component heterostructures to prepare a composite of 1D mesoporous carbon-coated manganese oxide(Mn_(3)O_(4) and MnO,denoted as Mn_(x)O_(y))embedded with Fe_(3)0_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4)).This composite was synthesized and its formation mechanism and microstructure were analyzed in detail.At the same time,the influence of this Mn_(x)O_(y)/C@Fe_(3)O_(4) structure on EMW properties and absorbing performance was further discussed.[Methods]Firstly,MnO_(2) nanowires were synthesized by using a simple hydrothermal method.Then,the MnO_(2) nanowires served as templates for the synthesis of MnO_(2)/PDA@Fe^(3+)composites through the in-situ polymerization of dopamine and Fe^(3+)adsorption.Finally,1D mesoporous carbon-coated manganese oxide composite embedded with Fe_(3)O_(4) nanoparticles(Mn_(x)O_(y)/C@Fe_(3)O_(4))composites were obtained after heat treatment at 550℃ in N_(2).The crystal structure of the samples was analyzed using X-ray diffractometer with Cu Ka irradiation.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(TEM)were used to observe microstructure and morphology of the samples.Nitrogen sorption measurements were obtained at 77 K on a Quantachrome surface area and pore size analyzer to measure the specific surface area and pore size distribution.XPS analysis was performed on X-ray photoelectron spectrometer with monochromatic Al Ka radiation.Magnetization curves of the samples were recorded with a Quantum Design physical property measurement system(PPMS-9)at room temperature.The electromagnetic parameters of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites were measured using an Agilent N5230C network analyzer in the frequency range of 2-18 GHz.For electromagentic testing,the Mn,Oy/C@Fe34 composites and paraffin wax were mixed at 50°C according to the mass ratio of 15 wt.%,20 wt.%and 25 wt.%,and pressed in a special mold to make coaxial rings(inner diameter=3.04 mm,outer diameter-7 mm),which were denoted as S-1,S-2 and S-3,respectively.[Results]SEM images illustrate the preparation process of iD mesoporous carbon-coated manganese oxide embedded with Fe3O4 nanoparticles composites(Mn_(x)O_(y)/C@Fe_(3)O_(4)).Most of the manganese oxide(Mn,Oy)was reduced to granular after heat treatment,while the outer carbon layer remains its 1D morphology and the carbon layer is interspersed with Fe_(3)O_(4) nanoparticles.The diffraction peaks of MnO_(2) nanowires align well with the body-centered tetragonal a-MnO2.For the Mn_(x)O_(y)/C@Fe_(3)O_(4) composites,the signals of α-MnO_(2) disappears,followed by the emergence of Mn_(3)O_(4) and three prominent diffraction peaks for the cubic MnO.In addition,four weak diffraction peaks correspond to the magnetite Fe_(3)O_(4),consistent with the HRTEM results.The corresponding nitrogen adsorption-desorption isotherm and pore size distribution curve are presented to further analyze the mesoporous structure of composite.The surface composition and element valence states of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite were investigated by using XPS.The polarization relaxation processes were analyzed according to the Debye theory which describes the relationship between e'and e".Besides the polarization loss,the contribution of the conduction loss plays an important role for the overall dielectric loss.The magnetization curve of Mn_(x)O_(y)/C@Fe_(3)O_(4) exhibits typical ferromagnetic behavior.The permittivity parameter(Co),defined as Co=u"(u)^(-2)f^(-1) determine the contribution of eddy current effect to magnetic loss.The tand values are all larger than those of tand,for the three samples,indicating that the loss capacity of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites is mainly derived from the dielectric loss.Although tand,is smaller,it plays an important role in improving the impedance matching of Mn_(x)O_(y)/C@Fe_(3)O_(4) composites.When the filler loading is 15 wt.%,the RL of sample S-1 is about-10.0 dB at the thickness of 1.5 mm with narrow EAB.As the filler loading increased to 20 wt.%,the RL of sample S-2 reached-62.0 dB at a thickness of 2.2 mm and the EAB was 6.4 GHz at a small thickness of 1.7 mm.When the filler loading is further increased to 25 wt.%,the microwave absorption performance of sample S3 decreased significantly with a little region of RL<-10.0 dB at the thickness of 5.0 mm.The values of[Zin/Zol of the three samples at thicknesses of 1.5-5.0 mm were calculated.Due to good impedance matching of S-2,the incident EMW can enter the material and then can be dissipated through dipole polarization loss,interface polarization loss,conduction loss,eddy current loss and natural ferromagnetic resonance loss.[Conclusions]1D Mn_(x)O_(y)/C@Fe_(3)O_(4) was synthesized via a process involving the coating of polydopamine,adsorption of Fe(ll)salts and heat treatment,using MnO_(2) nanowires as templates.The multi-component heterostructure of the Mn_(x)O_(y)/C@Fe_(3)O_(4) composite(Mn_(3)O_(4),MnO,Fe_(3)O_(4),and C)enhances the interfacial interactions between the different phases,providing increased interface polarization loss under the action of an alternating electromagnetic field.The numerous defects and terminal groups in the mesoporous carbon provide abundant dipole polarization centers.Additionally,the presence of mesopores reduces the weight of the material while increasing the multiple scattering losses of the electromagnetic waves within the material.The ID carbon structure in the matrix forms a conductive network between adjacent fibers,facilitating electron migration and transition,thereby enhancing conductive loss.The incorporation of magnetic Fe_(3)O_(4) nanoparticles introduces eddy current loss and natural ferromagnetic resonance loss,thus increasing magnetic loss.Moreover,the synergistic effect between dielectric and magnetic losses improves the impedance matching of the material,leading to excellent EMW absorption performance.
基金supported by the National Natural Science Foundation of China(No.52073010)Beijing Natural Science Foundation(2214069)。
文摘The 3D hollow hierarchi-cal architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight,high-e cient and broadband absorbers.Herein,the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti_(3)C_(2)Tx nanosheets through electrostatic self-assembly.The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti_(3)C_(2)Tx nanoflakes.Based on the synergistic e ectsof multi-components and special well-constructed structure,NiCo layered double hydroxides@Ti_(3)C_(2)Tx(LDHT-9)absorber remarkably achieves unexpected e ective absorption bandwidth(EAB)of 6.72 GHz with a thickness of 2.10 mm,covering the entire Ku-band.After calcination,transition metal oxide@Ti_(3)C_(2)Tx(TMOT-21)absorber near the percolation threshold possesses minimum reflection loss(RLmin)value of-67.22 dB at 1.70 mm within a filler loading of only 5 wt%.This work enlightens a simple strategy for constructing MXene-based composites to achieve high-e cient microwave absorbents with lightweight and tunable EAB.
基金the financial support from the Chongqing Research Program of Basic Research and Frontier Technology(Project No.cstc2019jcyj-msxm X0306)the National Key Research and Development Program of China(Project No.2016YFB0700403&Project No.2016YFB0301100)+1 种基金the fundamental Research funds for Central Universities(Project No.2021CDJJMRH001 and 2020CDJDPT001)the 111 Project(Project No.B16007)by the Ministry of Education and the State Administration of Foreign Experts Affairs of China。
文摘Duplex-structured Mg-7Li-2Al-1.5Sn alloys with high strength were fabricated and their strengthening mechanism was investigated.The Mg-7Li-2Al-1.5Sn alloys were prepared by casting and extruded at the temperature of 533 K with an extrusion ratio of 25:1.The microstructure and mechanical properties of Mg-7Li-2Al-1.5Sn alloys were systematically investigated by OM,XRD,SEM,TEM,and tensile tests.The results show that Mg-7Li-2Al-1.5Sn alloys are mainly composed ofα-Mg,β-Li,LiMgAl_(2),Mg_(2)Sn and Li_(2)MgSn phases.The yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)of the extruded alloy at room temperature reach 250 MPa,324 MPa and 11.9%,respectively.A lot of Sn-rich precipitates(Mg_(2)Sn and Li_(2)MgSn)are precipitated during extrusion with an average size of∼14 nm,which is beneficial to the grain refinement.Dynamic recrystallization occurs during hot deformation and the nanoprecipitates effectively refine the dynamic recrystallized(DRXed)grains.Besides,the residual dislocations existed in DRXed and un-DRXed grains result in the dislocation strengthening in the extruded alloy.Mg7Li-2Al-1.5Sn alloys possess excellent high-temperature mechanical properties with the YS,UTS and EL of 200 MPa,237 MPa and 26.7%at 423 K,respectively.Sn-rich precipitates with good thermal stability can effectively prevent grain growth,which is good for the improvement of the high-temperature performance of Mg-Li-Al-Sn alloy.
基金Research was supported by National Natural Science Foundation of China(52173274)the National Key R&D Project from Minister of Science and Technology(2021YFA1201603)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA16021101)Open access funding provided by Shanghai Jiao Tong University
文摘The pursuit to mimic skin exteroceptive ability has motivated the endeavors for epidermal artificial mechanoreceptors.Artificial mechanoreceptors are required to be highly sensitive to capture imperceptible skin deformations and preferably to be self-powered,breathable,lightweight and deformable to satisfy the prolonged wearing demands.It is still struggling to achieve these traits in single device,as it remains difficult to minimize device architecture without sacrificing the sensitivity or stability.In this article,we present an all-fiber iontronic triboelectric mechanoreceptor(ITM)to fully tackle these challenges,enabled by the high-output mechano-to-electrical energy conversion.The proposed ITM is ultralight,breathable and stretchable and is quite stable under various mechanical deformations.On the one hand,the ITM can achieve a superior instantaneous power density;on the other hand,the ITM shows excellent sensitivity serving as epidermal sensors.Precise health status monitoring is readily implemented by the ITM calibrating by detecting vital signals and physical activities of human bodies.The ITM can also realize acoustic-to-electrical conversion and distinguish voices from different people,and biometric application as a noise dosimeter is demonstrated.The ITM therefore is believed to open new sights in epidermal electronics and skin prosthesis fields.
基金financially supported by the National Natural Science Foundation of China (No. 22179007)。
文摘Lithium-sulfur batteries as one of the most promising next-generation high-energy storage system, the shuttle effect, the expansion of cathode and the slow electrode redox kinetics limit its further development. Herein, we report a two-dimensional, ultrathin and ultra-light bimetal-Ni Co-organic framework as the interlayer for Li-S batteries. This kind of interlayer can effectively block polysulfides and accelerate the conversion with a thickness of only 1 μm and a load of 0.1 mg/cm^(2). Because the MOF nanosheets with a thickness of a few nanometers have a large specific surface and a large number of exposed accessible active sites. At the same time, the intrinsic activity of each site is enhanced and the catalytic performance is improved due to the synergistic effect of mixed metals and the unique coordination environment around the active sites. So, 2D NiCo MOF/CNT totally meets the requirements for the lightweight and effective interlayer. The initial discharge capacity of cell with 2D NiCo MOF/CNT interlayer can reach 1132.7 m Ah/g at 0.5 C. It remained 709.1 m Ah/g after 300 cycles, showing good cycling stability and rate performance.
基金supported by the National Natural Science Foundation of China(No.51702197)Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratory,the Natural Science Foundation of Shaanxi Province(No.2022JM248)the Doctoral Scientific Research Foundation of Shaanxi University of Science&Technology(No.BJ16-06)。
文摘For electromagnetic wave-absorbing materials,maximizing absorption at a specific frequency has been constantly achieved,but enhancing the absorption properties in the entire band remains a challenge.In this work,a 3D porous pyrolytic carbon(PyC)foam matrix was synthesized by a template method.Amorphous carbon nanotubes(CNTs)were then in-situ grown on the matrix surface to obtain ultralight CNTs/Py C foam.These in-situ grown amorphous CNTs were distributed uniformly and controlled by the catalytic growth time and can enhance the interface polarization and conduction loss of composites.When the electromagnetic wave enters the internal holes,the electromagnetic energy can be completely attenuated under the combined action of polarization,conductivity loss,and multiple reflections.The ultralight CNTs/Py C foam had a density of 22.0 mg·cm^(-3)and a reflection coefficient lower than-13.3 d B in the whole X-band(8.2-12.4 GHz),which is better than the conventional standard of effective absorption bandwidth(≤-10 dB).The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in the X-band.
基金financially supported by the National Natural Science Youth Foundation of China(No.52402086)Natural Science Foundation of Shandong Province(No.ZR2023QE002)+6 种基金Youth Innovation Team Program in Colleges of Shandong Province(No.2023KJ144)Shandong Province Science and Technology Small and Medium-sized Enterprises Innovation Capability Improvement Project(No.2022TSGC1158)China Postdoctoral Science Foundation(No.2021M691963)Key Research and Development Program of Shandong Province of China(No.2020JMRH0503)the Fundamental Research Funds for the Central Universities(No.HIT.OCEF.2021003)National Natural Science Foundation of China(No.52272067)Doctoral Scientific Research Start-up Foundation from Shandong University of Technology(No.4041/419008)
文摘Lightweight materials with wide absorption capabilities,particularly in the C-band,have remained a challenge thus far.Recent research has indicated that effective absorption networks built by microfiber polarization loss can be a significant factor in increasing the effective absorption bandwidth(EAB).In this study,leaf vein-like carbon(LVC)was synthesized using an in situ blowing strategy.Taking inspiration from photosynthesis energy conversion mechanisms,a leaf veins-like hierarchical structure was created to establish an effective impedance-matching network and generate a high-density polarization region through leaf vein microfibers.This enhanced polarization relaxation effectively broadens the EAB of the LVC.At a low filling ratio of 6.3 wt%,the EAB of the LVC covers 80%of the C-band,as well as100%of the X-band and Ku-band.Achieving such a wide EAB in the C-band,especially in the multi-band context,relies on impedance matching and optimized polarization relaxation.This work demonstrates the crucial role of leaf vein micronetwork engineering in enhancing the C-band absorption properties of carbon-based materials,thus providing a viable reference for the development of lightweight,broadband,and highly absorptive materials for electromagnetic applications.
基金financial support from the Xiongan Science and Technology Innovation Talent Project of MOST,China(No.2022XACX0500)the State Key Research and Development Program of MOST,China(No.2021YFB3702400).
文摘High-strength Fe-Mn-Al-C-Ni low-density steels are highly desirable in lightweight transportation,safe infrastructure,and advanced energy applications.However,these steels generally suffer from limited ductility owing to the formation of coarse B2 particles at grain boundaries.In this study,we proposed a strategy to introduce copious intragranular B2 nanoprecipitates within fully-recrystallized fine austenitic grains in a Fe-26Mn-11Al-0.9C-5Ni ultralight steel by a simple cold rolling and annealing process.Compared with steel where B2 particles are mainly distributed at grain boundaries,the yield strength and ultimate tensile strength of this steel increased from 768 MPa and 1100 MPa to 954 MPa and 1337 MPa,respectively,whereas the total elongation increased from 38%to 50%.The higher yield strength was primarily due to the synergistic strengthening effect of intragranular B2 nanoprecipitates and grain refinement.The excellent ductility and sustained work hardening were mainly attributed to the strong dislocation storage capability mediated by the intragranular B2 nanoprecipitates and the greater dynamic slip band refinement strengthening effect.Hence,the achievement of copious intragranular B2 nanoprecipitation in fully recrystallized ultralight steel offers an effective pathway for developing lightweight materials with high strength and large ductility.
基金The authors thank the financial support from Michigan State University.
文摘Improving cell-level gravimetric and volumetric energy density is essential to achieve high-performance batteries in the rapidly evolving field of energy storage technology,which requires consideration of all cell components.Traditional current collectors(CCs)made of metal foil,especially the copper(Cu)current collector of the anode,possess high mass and cost yet do not contribute to capacity.Reducing the weight of Cu CC with minimum thickness and desirable mechanical strength is critical in enhancing energy density but is technically challenging.Herein,we demonstrate a fast and scalable chemical coating method based on electroless plating for fabricating ultralight CC(∼1.72mg cm^(−2))with a thin Cu layer(500nm)on an ultrathin polyethylene(PE)polymer scaffold(5μm).The ultralight and ultrathin CC possesses high metal purity,high mechanical strength,high thermal stability,and outstanding electrochemical performances in lithium-ion and lithium-metal battery systems.Our ultralight CC only exhibits∼30% of the weight of 6μm Cu foil,leading to a 5−10% improvement in cell-level gravimetric energy density without sacrificing volumetric energy density.Moreover,the simplicity and scalability of the chemical coating method make it a promising solution for the mass production of ultra-thin and lightweight current collectors.
基金financially supported by Beijing Natural Science Foundation(JQ21005)the National Key R&D Program of China(2021YFB3800100 and 2021YFB3800101)+1 种基金China Postdoctoral Science Foundation(2020M670036)the R&D Fruit Fund(20210001)。
文摘Ultrathin(thickness less than 10μm)and ultralight flexible perovskite solar cells(FPSCs)have attracted extensive research enthusiasm as power sources for specific potential lightweight applications,such as drones,blimps,weather balloons and avionics.Currently,there is still a certain gap between the power conversion efficiency(PCE)of ultrathin FPSCs and common FPSCs.This study demonstrates ultrathin FPSCs on 3-μm-thick parylene-C substrates via a flip-over transferring process.The Zr,Ti and Ga-doped indium oxide(ITGZO)film is employed as the bottom transparent electrode of ultrathin inverted FPSCs with a remarkable PCE of 20.2%,which is comparable to that based on common FPSCs.Devices on glasses and parylene-F(i.e.,parylene-VT4)substrates were also constructed to verify the advantages of parylene-C.Furthermore,an excellent powerper-weight of 30.3 W g^(-1) is achieved attributed to remarkable PCE and ultrathin-ultralight substrates,demonstrating the great promise of fabricating efficient,ultrathin and ultralight solar cells with parylene-C films.
文摘美国材料实验协会(American Society of Testing Materials,ASTM)F2052-21标准(对应中文标准YY/T 0987.2)规定了磁共振环境中医疗器械磁致位移力的标准测试方法,在国际上被广泛接受和应用。该方法是用细线将被测植入物悬挂于磁场中,测量悬线相对竖直方向的偏转角,从而计算磁致位移力相对重力的大小。然而,当该方法应用于极轻型植入物测试时,很难满足悬线质量小于植入物质量的1%的要求。该文提出了一种基于配重修正的极轻型植入物磁致位移力测试方法:使用质量超出待测植入物质量的1%的悬线和夹持物,按照标准方法测量偏转角度,再使用待测植入物质量在被测物总质量中的占比对偏转角度进行修正,从而获得准确的测量结果。该文对配重修正法进行了理论计算和实验验证,结果表明,所提出的配重修正法能够有效测量极轻型植入物的磁致位移力偏转角。
