The demand for high-temperature electromagnetic wave absorption(EWA)materials has significantly increased alongside advancements in aerospace and communication technologies.Although traditional magnetic absorbers,such...The demand for high-temperature electromagnetic wave absorption(EWA)materials has significantly increased alongside advancements in aerospace and communication technologies.Although traditional magnetic absorbers,such as ferrites and metal powders,show excellent magnetic loss performance at room temperature,they have significant limitations in harsh environments due to their high density,low Curie temperature,and susceptibility to oxidation.In contrast,carbon-containing materials have emerged as promising candidates for high-temperature EWA applications,owing to their high melting point,low density,tunable dielectric loss mechanisms,and superior thermal stability.Unlike magnetic materials,carbon-based systems primarily dissipate electromagnetic energy through conductance loss,dipole polarization,and interfacial polarization,thereby avoiding performance degradation at elevated temperatures.However,several critical challenges remain,including insufficient oxidation resistance,mechanical reliability issues,and the need for stable impedance matching.To address these limitations,recent strategies such as defect engineering,heterointerface construction,and metamaterial design have been proposed to enhance thermal stability and functional performance.This review provides a systematic summary of recent advances in carbon-containing absorbers,with a focus on dielectric loss mechanisms,optimization strategies,and multiscale structural design principles.By elucidating the structure–property relationships of carbon materials,carbide ceramics,and novel carbon hybrids,this study aims to offer theoretical and technical guidance for the development of advanced high-temperature electromagnetic wave absorbers,thereby promoting their practical applications in aerospace and telecommunications.展开更多
Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promisin...Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promising strategy to address this issue.To realize the synergy,herein,Sn whiskers with an in situ oxide layer served as substrates for magnetic-loss-active CoNi nanosheet growth,forming a hierarchical CoNi@SnO_(2)@Sn(CNS)heterostructure.The CNS absorber achieves a minimum reflection loss(RL_(min))value of-62.29 dB with an effective absorption bandwidth(EAB)of 2.2 GHz,covering the entire C-band with 70%absorption at only 2.61 mm thickness.The nanosheet design of CoNi enhances magnetic anisotropy to promote natural resonance,while the conductive Sn core and abundant Sn/SnO_(2) and CoNi/SnO_(2) heterointerfaces facilitate conduction loss and dielectric polarization.When composited into a thermoplastic polyurethane(TPU)matrix,the resulting CNS/TPU-2 film(20 wt%CNS)exhibits an RL_(min) value of-61.04 dB and a 2.5 GHz EAB.Its in-plane and through-plane thermal conductivities reach 2.41 and 0.51 W m^(-1) K^(-1),representing 4.1 and 2.6 times those of pure TPU films,respectively,facilitating heat dissipation from protected devices.This work provides valuable insights into magnetic-dielectric synergy for low-frequency MA of 1D metal-based materials,offering promising potential for 5G communications and flexible electronics.展开更多
Objective Burning solid cooking fuel contributes to household air pollution and is associated with frailty.However,how solid cooking fuel use contributes to the development of frailty has not been well illustrated.Met...Objective Burning solid cooking fuel contributes to household air pollution and is associated with frailty.However,how solid cooking fuel use contributes to the development of frailty has not been well illustrated.Methods This study recruited 8,947 participants aged≥45 years from the China Health and Retirement Longitudinal Study,2011–2018.Group-based trajectory modeling was employed to identify frailty trajectories.Multinomial logistic regression was used to assess the association between solid cooking fuel use and frailty trajectories.Population-attributable fractions were used to estimate the frailty burden from solid fuel use.Results We identified three frailty trajectories:low-stable(n=5,789),moderate-increasing(n=2,603),and fast-increasing(n=555).Solid fuel use was associated with higher odds of being in the moderate-increasing(OR:1.24,95%CI:1.08–1.42)and fast-increasing(OR:1.48,95%CI:1.14–1.92)trajectories.These associations were strengthened by longer solid fuel use(P for trend<0.001).Switching to clean fuel significantly reduced the risk of being in these trajectories compared with persistent solid fuel users.Without solid fuel,8%of moderate-and 19%of fast-increasing trajectories demonstrated frailty development like the low-stable group.Conclusion Solid cooking fuel use is associated with frailty trajectories in middle-aged and older Chinese populations.展开更多
Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants ...Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants who had BMI repeatedly measured 3–8times between 1989 and 2009,as well as glucose and insulin measured in 2009.BMI trajectories were identified using a latent class growth mixed model.The interplay between BMI trajectories and IR on diabetes was explored using the four-way effect decomposition method.Logistic regression and mediation models were used to estimate the interaction and mediation effects,respectively.Results Three distinct BMI trajectory groups were identified:low-stable(n=1,625),mediumincreasing(n=613),and high-increasing(n=98).Both interaction and mediation effects of BMI trajectories and IR on incident diabetes were significant(P<0.05).The proportion of incident diabetes was higher in the IR-obesity than in the insulin-sensitivity(IS)obesity group(18.9%vs.5.8%,P<0.001).After adjusting for covariates,the odds ratios(95%confidence intervals)of the IR,IS-obesity,and IRobesity groups vs.the normal group were 3.22(2.05,5.16),2.05(1.00,3.97),and 7.98(5.19,12.62),respectively.IR mediated 10.7%of the total effect of BMI trajectories on incident diabetes(P<0.001).Conclusion We found strong interactions and weak mediation effects of IR on the relationship between life-course BMI trajectories and incident diabetes.IS-obesity is associated with a lower risk of incident diabetes than IR-obesity.展开更多
Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for ...Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments,however,the integration of multiple functions in their preparation is extremely challenging.To tackle these challenges,we fabricated a multifunctional SiC@SiO_(2) nanofiber aerogel(SiC@SiO_(2) NFA)with a threedimensional(3D)porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process.The as-prepared SiC@SiO_(2) NFA exhibits an ultralow density(~11 mg cm^(-3)),ultra-elastic,fatigue-resistant and refractory performance,high temperature thermal stability,thermal insulation properties,and significant strain-dependent piezoresistive sensing behavior.Furthermore,the SiC@SiO_(2) NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss(RL_(min))value of-50.36 d B and a maximum effective absorption bandwidth(EAB_(max))of 8.6 GHz.The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.展开更多
Microwave absorption(MA) materials have been captured extensive attentions due to the serious electromagnetic(EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with mag...Microwave absorption(MA) materials have been captured extensive attentions due to the serious electromagnetic(EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with magnetic constituents as cores and dielectric constituents as shells, which inevitably suppressed the magnetic coupling causing the decrease of magnetic loss to some extent. Herein, the coreshell structural carbon(C) microsphere/magnetic metal composites were fabricated through the combination of an electrostatic assembly approach and subsequent in-situ reduction reaction. The complex permittivity and permeability of core-shell C@magnetic metal composite system can be effective adjusted by the constituent and microstructure of shells. Thanks to the distinct magnetic coupling from the subtle designed structures and the promotion of the magnetic-dielectric synergy, the C@magnetic metal composite exhibited enhanced MA properties. The optimal reflection loss(RL) of C@Ni composite was-54.1 dB with a thickness of 3.4 mm, meanwhile the effective absorbing band could reach over 5.5 GHz at only a1.8 mm thickness. Broad absorption bandwidth with RL below-10 d B could achieve 6.0 GHz and 6.7 GHz for C@Co and C@Ni Co composites with a thin 2.1 mm thickness, respectively. Our exciting findings might lead a guide on the novel structure design for the functional core-shell structural composites used for microwave absorption.展开更多
A novel entropy-stabilized(ES)(Ca,Sr,Ba)ZrO_(3) ceramic has been designed and synthesized by pressureless sintering of CaZr03,SrZr03 and BaZr03 powders mixtures at 1450℃,1500℃and 1550℃for 3 h.X-ray diffraction,scan...A novel entropy-stabilized(ES)(Ca,Sr,Ba)ZrO_(3) ceramic has been designed and synthesized by pressureless sintering of CaZr03,SrZr03 and BaZr03 powders mixtures at 1450℃,1500℃and 1550℃for 3 h.X-ray diffraction,scanning electron microscopy and transmission electron microscopy analyses collectively indicate that a single solid solution is formed with a homogeneous distribution of metal elements after sintering at 1550℃.The relative density and hardness of the ES(Ca,Sr,Ba)ZrO_(3) ceramic sintered at 1550℃are 97.79%and 10.840.33 GPa,re s pectively.This ES(Ca,Sr,Ba)ZrO_(3) exhibits lower thermal conductivity from 373 K to 1073 K than their constituting zirconates,CaZrO_(3),SrZrO_(3) and BaZrO_(3).Most importantly,the ES(Ca,Sr,Ba)ZrO_(3) ceramic possesses good corrosion resistance to TiNi alloy melt and no distinct reaction layer exists between TiNi alloy and ES(Ca,Sr,Ba)ZrO_(3) ceramic in the contact region.The combination of these properties indicates that ES(Ca,Sr,Ba)ZrO_(3) ceramic is promising for use as a novel crucible material for the melting of titanium alloys.展开更多
Semiconductor-noble metal composite has become a research focus due to its superior performance compared with its respective component.Although various methods have been developed to synthesize semiconductor-noble met...Semiconductor-noble metal composite has become a research focus due to its superior performance compared with its respective component.Although various methods have been developed to synthesize semiconductor-noble metal heterostructures,most of them are relatively complex multistep and use toxic reactants of high cost and risk.In this work,a series of Cu_(2)O/Ag heterojunctions were quickly prepared in one step via simple microwave-assisted green route.XRD,SEM,TEM,EDS,XPS,etc.were used to characterize obtained products,and the results indicate a Cu_(2)O/Ag metal-semiconductor heterojunction in micro-nano size was fabricated successfully.In addition,antibacterial behavior of Cu_(2)O/Ag heterojunctions against E.coli and S.aureus were investigated.Owing to the synergistic effect of Cu_(2)O and Ag,the heterojunction exhibits much better antibacterial performance than the pristine Cu_(2)O does.This work provides new insights into the green design and fabrication of surface-modified Cu_(2)O hybrid multifunctional materials for antibacterial applications.展开更多
Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric const...Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric constant of Ti_(3)C_(2)T_(x)MXene,we have successfully synthesized core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres.This architecture,comprising SiO_(2) as the core,MXene as the intermediate layer,and MoS_(2) as the outer shell,is achieved through an electrostatic self‐assembly method combined with a hydrothermal process.This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS_(2) nanosheets.Notably,the synergistic combination of SiO_(2) and MoS_(2) with highly conductive MXene enables the suitable dielectric constant of the composites,ensuring optimal impedance matching.Therefore,the core‐shell structured SiO_(2)@MXene@MoS_(2) nanospheres exhibit excellent EMW absorption performance,featuring a remarkable minimum reflection loss(RL_(min))of−52.11 dB(2.4 mm).It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth(EAB)of 6.72 GHz.This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by“wide bandwidth and strong reflection loss.”展开更多
Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such ma...Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials,particularly when adjustment of the constitution or mixing ratio is limited.In this study,bowl-like and honeycomb titanium dioxide/carbon nanotube(TiO_(2)/CNT)composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration,respectively.Compared to the honeycomb structure,the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization,and augmented multiple reflections.The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics.The bowl-like TiO_(2)/CNT composite exhibited a minimum reflection loss(RL_(min))of-38.6 dB(1.5 mm)with a wide effective absorption band(EAB;<-10 dB)of4.2 GHz,while the honeycomb TiO_(2)/CNT composite showed an RLminof-34.8 dB(2.1 mm)with an EAB of 4.3 GHz.The required mixing ratio in the matrix was only 15 wt%,outperforming that of the most closely related composites.Thus,both the bowl-like and honeycomb TiO_(2)/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.展开更多
With the gradually increasing protection awareness about electromagnetic pollution,the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention.In this work,co...With the gradually increasing protection awareness about electromagnetic pollution,the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention.In this work,composites consisting of straw-derived biochar combined with NiCo alloy were successfully fabricated through high-temperature carbonization and subsequent hydrothermal reaction.The electromagnetic parameters of the porous biocarbon/NiCo composites can be effectively modified by altering their NiCo content,and their improved absorbing performance can be attributed to the synergy effect of magnetic-dielectric characteristics.An exceptional reflection loss of-27.0 dB at 2.2 mm thickness and an effective absorption bandwidth of 4.4 GHz(11.7-16.1 GHz)were achieved.These results revealed that the porous biocarbon/NiCo composites could be used as a new generation absorbing material because of their low density,light weight,excellent conductivity,and strong absorption.展开更多
One-dimensional(1D)metals are well known for their exceptional conductivity and their ease of formation of interconnected networks that facilitate electron migration,making them promising candidates for electromagneti...One-dimensional(1D)metals are well known for their exceptional conductivity and their ease of formation of interconnected networks that facilitate electron migration,making them promising candidates for electromagnetic(EM)attenuation.However,the impedance mismatch from high conductivity and their singular mode of energy loss hinder effective EM wave dissipation.Construction of cable structures not only optimizes impedance matching but also introduces a multitude of heterojunctions,increasing attenuation modes and potentially enhancing EM wave absorption(EMA)performance.Herein,we showcase the scalable synthesis of tin(Sn)whiskers from a Ti_(2)SnC MAX phase precursor,followed by creation of a 1D tin@carbon(Sn@C)cable structure through polymerization of PDA on their surface and annealing in argon.The EMA capabilities of Sn@C significantly surpass those of uncoated Sn whiskers,with an effective absorption bandwidth reaching 7.4 GHz.Remarkably,its maximum radar cross section reduction value of 27.85 dBm2 indicates its exceptional stealth capabilities.The enhanced EMA performance is first attributed to optimized impedance matching,and furthermore,the Sn@C cable structures have rich SnO2/C and Sn/SnO2 heterointerfaces and the associated defects,which increase interfacial and defect-induced polarization losses,as visually demonstrated by off-axis electron holography.The development of the Sn@C cable structure represents a notable advancement in broadening the scope of materials with potential applications in stealth technology,and this study also contributes to the understanding of how heterojunctions can improve EMA performance.展开更多
One-dimensional tantalum carbide(TaC)nanorodsare considered promising candidates for high-temperature electromagnetic wave(EMW)absorption because of their intrinsically high electrical conductivity and exceptional the...One-dimensional tantalum carbide(TaC)nanorodsare considered promising candidates for high-temperature electromagnetic wave(EMW)absorption because of their intrinsically high electrical conductivity and exceptional thermal stability.However,conventional synthesis approaches typically yield products with low quality and poor efficiency,limiting their practical applicability.Here,we report the rapid and scalable synthesis of high-quality TaC nanorods via a molten salt-assisted carbothermal reduction strategy integrated with microwave heating.The formation of well-defined one-dimensional TaC nanorods was achieved within 20 min at 1300℃by precisely tuning the precursor composition(Ta_(2)Os:C:NaCl:Ni=1:8:2:0.08).The resulting TaC nanorods exhibit notable EMW absorption properties,with a maximum effective absorption bandwidth(EABma)of 3.0 GHz at a simulated thickness of 1.0 mm and a minimum reflection loss(RLmin)of-30.5 dB.Off-axis electron holography reveals pronounced charge accumulation at the Ta_(2)Os shell/TaC core interface,indicative of interfacial polarization effects.Furthermore,radar scattering cross-section(RCs)l simulations demonstrate substantial attenuation of the backscattered signal from a perfect electric conductor(PEC)substratel coated with the TaC layer,with the strongest electromagnetic energy dissipation observed at a coating thickness ofl 1.0 mm.These results underscore the viability of microwave-assisted synthesis as an efficient and sustainable route for producing high-performance TaC nanorods for EMW absorption applications under extreme thermal conditions.展开更多
With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace...With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace and national defense infrastructures.As the electromagnetic environment has become increasingly complex and congested,electromagnetic waves have not only brought unprecedented convenience but also introduced serious challenges,including electromagnetic interference,radiation pollution,and information insecurity.Consequently,the rational design and development of microwave absorption materials(MAMs)are critically important for protecting human health,mitigating electromagnetic pollution,and strengthening information security in the information age.展开更多
Despite the extensive research conducted on dielectric-magnetic coupling in metal-organic frameworks(MOF)-derived absorbers,the underlying mechanisms associated with defects,interfaces,and orbital hybridization remain...Despite the extensive research conducted on dielectric-magnetic coupling in metal-organic frameworks(MOF)-derived absorbers,the underlying mechanisms associated with defects,interfaces,and orbital hybridization remain inadequately investigated.To address this,we developed coral-like MOF-derived nickel-phosphorous@carbon(NP@C)nanocomposites by adjusting the pyrolysis temperature,revealing for the first time the link between structure and electromagnetic(EM)performance.The composite features nickel phosphide nanoparticles(Ni_(12)P_(5) core/Ni_(2)P shell)embedded in an amorphous carbon matrix,where a unique crystal orientation and interfacial coupling enhance EM wave dissipation.The calculations show that charge transfer(0.66e)at the C-Ni_(12)P_(5) interface increases conductance loss,whereas the C-Ni_(2)P-Ni_(12)P_(5) heterostructure generates interfacial polarization and defect states via negative charge transfer(0.20e),synergistically enhancing dielectric and magnetic loss.Electronic structure analysis revealed that sharp Ni 3d orbital peaks near the Fermi level coexist with broad carbon matrix peaks,enabling both conductive and spin-related magnetic loss mechanisms.The NP@C nanocomposite achieves a reflection loss of −54.1 dB and an effective absorption band covering 4.1 GHz at a thin thickness of 1.37 mm.This study clarifies the atomic-and electronic-level EM response mechanisms of MOF-derived carbon materials,offering new insights for designing high-performance absorbers.展开更多
Ceramic-based electromagnetic interference(EMI)shielding materials have emerged as promising solutions because of their tunable dielectric and magnetic properties,excellent chemical stability,and favorable cost‒perfor...Ceramic-based electromagnetic interference(EMI)shielding materials have emerged as promising solutions because of their tunable dielectric and magnetic properties,excellent chemical stability,and favorable cost‒performance ratio.Despite their advantages,enhancing electrical conductivity and optimizing microstructural design remain key technical challenges.This review presents a systematic analysis of the working mechanisms,advanced fabrication techniques,and performance optimization strategies for ceramic-based EMI shielding materials.This study provides an in-depth analysis of the key factors influencing shielding efficiency and discusses the shielding mechanisms and performance enhancement strategies for both conventional ceramics(e.g.,silicon carbide and ferrites)and advanced ceramics(e.g.,MXenes and high-entropy ceramics).Future research directions are identified,including wideband shielding design to meet the requirements of 5G and terahertz communication;the integration of mechanical,thermal,and electromagnetic functionalities;and the development of intelligent,responsive materials.Additionally,this review highlights the potential of machine learning(ML)and artificial intelligence(AI)in accelerating material design and performance optimization.By critically analyzing the interrelationships among material properties,fabrication processes,and shielding mechanisms,this work offers a comprehensive perspective on the innovative application of advanced ceramics in EMI shielding,with the aim of bridging the gap between fundamental research and industrial implementation.展开更多
Transition metal carbides exhibit outstanding mechanical properties but suffer from a critical hardness-toughness trade-off.Spinodal decomposition-mediated phase separation,induced by high-temperature aging,is an effe...Transition metal carbides exhibit outstanding mechanical properties but suffer from a critical hardness-toughness trade-off.Spinodal decomposition-mediated phase separation,induced by high-temperature aging,is an effective strategy for enhancing the mechanical properties of carbide ceramics.However,the typically high stacking fault energy in carbide ceramics restricts the dislocation pinning effects of spinodal decomposition interfaces,hampering potential hardness and toughness improvements.Guided by first-principles calculations,this study employs(Ti,Zr)C carbide ceramics as a representative system and systematically lowers its stacking fault energy through nitrogen(N)incorporation.With optimized composition and controlled aging,distinct stacking faults emerged after short-term aging.As the aging time increased,these stacking faults progressively transformed into dislocation sources,facilitating dislocation multiplication.Mechanical testing revealed that samples incorporating 25%N followed by aging exhibited significant enhancements:The hardness and fracture toughness increased by approximately 40% and 50%,respectively,compared with those of the initial material.However,at higher N concentrations,excessive elastic strain energy accumulation induced lamellar thickening,diminishing the extent of improvement in hardness and toughness.This work designs a strategy to lower the stacking fault energy in carbide ceramics,overcoming its constraint on performance enhancement via spinodal decomposition and enabling hardness-toughness synergy via spinodal decomposition through theoretical and processing solutions.展开更多
Ca^(2+)/Cr^(3+)co-doped LaAlO_(3) infrared(IR)ceramics have been proven to be potential energy-saving materials for high-temperature industries because of their high emissivity and high-temperature stability.However,C...Ca^(2+)/Cr^(3+)co-doped LaAlO_(3) infrared(IR)ceramics have been proven to be potential energy-saving materials for high-temperature industries because of their high emissivity and high-temperature stability.However,Cr^(6+)formation commonly occurs in materials and poses environmental and health risks,such as Cr^(6+)dissolution in water and CrO_(3)(g)volatilization.In this study,we combined high emissivity with in situ detoxification by introducing residual Al_(2)O_(3) into Ca^(2+)/Cr^(3+)co-doped LaAlO_(3) ceramics.Compared with the undoped ceramics,the addition of 20 wt%residual Al_(2)O_(3) resulted in a 78.5%reduction to 18.44 mg/kg(lower than the EU standard of 20 mg/kg)in Cr^(6+)dissolution and a decrease in 77.8%CrO_(3)(g)volatilization.This significant detoxification effect can be attributed to the formation of CaAl_(12−x)Cr_(x)O_(19).Additionally,as the residual Al_(2)O_(3) content increased from 5 to 20 wt%,the ceramics maintained high emissivity,above 0.896 in the near-infrared band and 0.781 in the mid-infrared band.Furthermore,the IR coating effectively increased the surface temperature(from 767.1 to 790.7℃/min)and the heat radiation of the heating source,increasing the heating rate from 31.7 to 34.6℃/min during water heating.This work offers a promising approach for designing environmentally friendly IR ceramics with excellent IR performance for energy-saving applications in the high-temperature industry.展开更多
Multi-component occupancies of perovskite materials(ABO_(3))have brought diverse crystallographic distortions and highly tunable defect structures.These structural features enable ABO_(3)to have customizable dielectri...Multi-component occupancies of perovskite materials(ABO_(3))have brought diverse crystallographic distortions and highly tunable defect structures.These structural features enable ABO_(3)to have customizable dielectric and magnetic properties,offering new opportunities for advancing microwave absorbing materials.In this study,entropy-driven strategies,including composition optimization,structural/defective design,microstructure engineering,and microwave absorption simulation,are proposed to improve the microwave absorption capacity of(Ba_(1/3)Sr_(1/3)Ca_(1/3))FeO_(3).The hexagonal perovskite structure(Ba_(1/3)Sr_(1/3)Ca_(1/3))FeO_(3)prepared at 1100℃exhibits exceptional electromagnetic wave absorption properties,with a minimum reflection loss of−40.58 dB at a thickness of 1.2 mm and a maximum effective absorption bandwidth of 4.16 GHz.The results indicate that the interconnection of octahedra,and structural distortions,oxygen vacancies,and other defects enhance the dielectric polarization of the material,leading to excellent wave absorption performance.The entropy-driven design strategy for perovskite ABO_(3)materials offers valuable insights for the development of advanced electromagnetic wave absorption materials.展开更多
Two-dimensional(2D)transition metal carbides(MXene)possess attractive conductivity and abundant surface functional groups,providing immense potential in the field of electromagnetic wave(EMW)absorption.However,high co...Two-dimensional(2D)transition metal carbides(MXene)possess attractive conductivity and abundant surface functional groups,providing immense potential in the field of electromagnetic wave(EMW)absorption.However,high conductivity and spontaneous aggregation of MXene suffer from limited EMW response.Inspired by dielectric–magnetic synergy effect,the strategy of decorating MXene with magnetic elements is expected to solve this challenge.In this work,zigzag-like Mo_(2)TiC_(2)–MXene nanofibers(Mo-based MXene(Mo–MXene)NFs)with cross-linked networks are fabricated by hydrofluoric acid(HF)etching and potassium hydroxide(KOH)shearing processes.Subsequently,Co-metal–organic framework(MOF)and derived CoNi layered double hydroxide(LDH)ultrathin nanosheets are grown inside Mo–MXene NFs,and the N-doped carbon matrix anchored by CoNi alloy nanoparticles formed by pyrolysis is firmly embedded in the Mo–MXene NFs network.Benefiting from synergistic effect of highly dispersed small CoNi alloy nanoparticles,a three-dimensional(3D)conductive network assembled by zigzag-like Mo–MXene NFs,numerous N-doped hollow carbon vesicles,and abundant dual heterogeneous interface,the designed Mo–MXene/CoNi–NC heterostructure provides robust EMW absorption ability with a reflection loss(RL)value of−68.45 dB at the thickness(d)of 4.38 mm.The robust EMW absorption performance can be attributed to excellent dielectric loss,magnetic loss,impedance matching(Z),and multiple scattering and reflection triggered by the unique 3D network structure.This work puts up great potential in developing advanced MXene-based EMW absorption devices.展开更多
基金supported by the National Natural Science Foundation of China(52572086 and 52502371)the Natural Science Foundation of Henan(242300421010)+2 种基金Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province(22HASTIT001)the Henan Province Natural Science Foundation Outstanding Youth Fund Project(242300421009)the Henan Province science and technology research project(252102320354and 252102230037)。
文摘The demand for high-temperature electromagnetic wave absorption(EWA)materials has significantly increased alongside advancements in aerospace and communication technologies.Although traditional magnetic absorbers,such as ferrites and metal powders,show excellent magnetic loss performance at room temperature,they have significant limitations in harsh environments due to their high density,low Curie temperature,and susceptibility to oxidation.In contrast,carbon-containing materials have emerged as promising candidates for high-temperature EWA applications,owing to their high melting point,low density,tunable dielectric loss mechanisms,and superior thermal stability.Unlike magnetic materials,carbon-based systems primarily dissipate electromagnetic energy through conductance loss,dipole polarization,and interfacial polarization,thereby avoiding performance degradation at elevated temperatures.However,several critical challenges remain,including insufficient oxidation resistance,mechanical reliability issues,and the need for stable impedance matching.To address these limitations,recent strategies such as defect engineering,heterointerface construction,and metamaterial design have been proposed to enhance thermal stability and functional performance.This review provides a systematic summary of recent advances in carbon-containing absorbers,with a focus on dielectric loss mechanisms,optimization strategies,and multiscale structural design principles.By elucidating the structure–property relationships of carbon materials,carbide ceramics,and novel carbon hybrids,this study aims to offer theoretical and technical guidance for the development of advanced high-temperature electromagnetic wave absorbers,thereby promoting their practical applications in aerospace and telecommunications.
基金supported by the National Natural Science Foundation of China(52171033,52431003,U23A20574)the Fundamental Research Funds for the Central Universities(2242025K20004)the SEU Innovation Capability Enhancement Plan for Doctoral Students(CXJH_SEU 24148,CXJH_SEU 25036).
文摘Microwave absorption(MA)materials often face poor synergy between impedance matching and attenuation in the low-frequency range.Balancing permittivity and permeability through magnetic-dielectric synergy is a promising strategy to address this issue.To realize the synergy,herein,Sn whiskers with an in situ oxide layer served as substrates for magnetic-loss-active CoNi nanosheet growth,forming a hierarchical CoNi@SnO_(2)@Sn(CNS)heterostructure.The CNS absorber achieves a minimum reflection loss(RL_(min))value of-62.29 dB with an effective absorption bandwidth(EAB)of 2.2 GHz,covering the entire C-band with 70%absorption at only 2.61 mm thickness.The nanosheet design of CoNi enhances magnetic anisotropy to promote natural resonance,while the conductive Sn core and abundant Sn/SnO_(2) and CoNi/SnO_(2) heterointerfaces facilitate conduction loss and dielectric polarization.When composited into a thermoplastic polyurethane(TPU)matrix,the resulting CNS/TPU-2 film(20 wt%CNS)exhibits an RL_(min) value of-61.04 dB and a 2.5 GHz EAB.Its in-plane and through-plane thermal conductivities reach 2.41 and 0.51 W m^(-1) K^(-1),representing 4.1 and 2.6 times those of pure TPU films,respectively,facilitating heat dissipation from protected devices.This work provides valuable insights into magnetic-dielectric synergy for low-frequency MA of 1D metal-based materials,offering promising potential for 5G communications and flexible electronics.
基金supported by the National Natural Science Foundation of China(82222064,81973147)the National Key Research and Development Program(2022YFC2010100)the Shandong University Distinguished Young Scholars。
文摘Objective Burning solid cooking fuel contributes to household air pollution and is associated with frailty.However,how solid cooking fuel use contributes to the development of frailty has not been well illustrated.Methods This study recruited 8,947 participants aged≥45 years from the China Health and Retirement Longitudinal Study,2011–2018.Group-based trajectory modeling was employed to identify frailty trajectories.Multinomial logistic regression was used to assess the association between solid cooking fuel use and frailty trajectories.Population-attributable fractions were used to estimate the frailty burden from solid fuel use.Results We identified three frailty trajectories:low-stable(n=5,789),moderate-increasing(n=2,603),and fast-increasing(n=555).Solid fuel use was associated with higher odds of being in the moderate-increasing(OR:1.24,95%CI:1.08–1.42)and fast-increasing(OR:1.48,95%CI:1.14–1.92)trajectories.These associations were strengthened by longer solid fuel use(P for trend<0.001).Switching to clean fuel significantly reduced the risk of being in these trajectories compared with persistent solid fuel users.Without solid fuel,8%of moderate-and 19%of fast-increasing trajectories demonstrated frailty development like the low-stable group.Conclusion Solid cooking fuel use is associated with frailty trajectories in middle-aged and older Chinese populations.
基金supported by Grant 82222064 from the National Natural Science Foundation of Chinathe Shandong University Distinguished Young Scholars。
文摘Objective This study aimed to explore the interplay between the life-course body mass index(BMI)trajectories and insulin resistance(IR)on incident diabetes.Methods This longitudinal cohort included 2,336 participants who had BMI repeatedly measured 3–8times between 1989 and 2009,as well as glucose and insulin measured in 2009.BMI trajectories were identified using a latent class growth mixed model.The interplay between BMI trajectories and IR on diabetes was explored using the four-way effect decomposition method.Logistic regression and mediation models were used to estimate the interaction and mediation effects,respectively.Results Three distinct BMI trajectory groups were identified:low-stable(n=1,625),mediumincreasing(n=613),and high-increasing(n=98).Both interaction and mediation effects of BMI trajectories and IR on incident diabetes were significant(P<0.05).The proportion of incident diabetes was higher in the IR-obesity than in the insulin-sensitivity(IS)obesity group(18.9%vs.5.8%,P<0.001).After adjusting for covariates,the odds ratios(95%confidence intervals)of the IR,IS-obesity,and IRobesity groups vs.the normal group were 3.22(2.05,5.16),2.05(1.00,3.97),and 7.98(5.19,12.62),respectively.IR mediated 10.7%of the total effect of BMI trajectories on incident diabetes(P<0.001).Conclusion We found strong interactions and weak mediation effects of IR on the relationship between life-course BMI trajectories and incident diabetes.IS-obesity is associated with a lower risk of incident diabetes than IR-obesity.
基金financially supported by the National Natural Science Foundation of China(No.U2004177 and U21A2064)Outstanding Youth Fund of Henan Province(No.212300410081)+1 种基金Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province(22HASTIT001)The Research and Entrepreneurship Start-up Projects for Overseas Returned Talents。
文摘Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments,however,the integration of multiple functions in their preparation is extremely challenging.To tackle these challenges,we fabricated a multifunctional SiC@SiO_(2) nanofiber aerogel(SiC@SiO_(2) NFA)with a threedimensional(3D)porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process.The as-prepared SiC@SiO_(2) NFA exhibits an ultralow density(~11 mg cm^(-3)),ultra-elastic,fatigue-resistant and refractory performance,high temperature thermal stability,thermal insulation properties,and significant strain-dependent piezoresistive sensing behavior.Furthermore,the SiC@SiO_(2) NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss(RL_(min))value of-50.36 d B and a maximum effective absorption bandwidth(EAB_(max))of 8.6 GHz.The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.
基金financially supported from the National Natural Science Foundation of China (Grant Nos. 51725101, 11727807, 51672050, and 61790581)the Ministry of Science and Technology of China (973 Project No. 2018YFA0209102)+2 种基金Science Foundation for the Excellent Youth Scholars of Henan Province (Grant No. 212300410089)the Support Program for Scientific and Technological Innovation Talents of Higher Education in Henan Province (Grant No. 21HASTIT004)China Postdoctoral Science Foundation (Grant No. 2019M661352)。
文摘Microwave absorption(MA) materials have been captured extensive attentions due to the serious electromagnetic(EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with magnetic constituents as cores and dielectric constituents as shells, which inevitably suppressed the magnetic coupling causing the decrease of magnetic loss to some extent. Herein, the coreshell structural carbon(C) microsphere/magnetic metal composites were fabricated through the combination of an electrostatic assembly approach and subsequent in-situ reduction reaction. The complex permittivity and permeability of core-shell C@magnetic metal composite system can be effective adjusted by the constituent and microstructure of shells. Thanks to the distinct magnetic coupling from the subtle designed structures and the promotion of the magnetic-dielectric synergy, the C@magnetic metal composite exhibited enhanced MA properties. The optimal reflection loss(RL) of C@Ni composite was-54.1 dB with a thickness of 3.4 mm, meanwhile the effective absorbing band could reach over 5.5 GHz at only a1.8 mm thickness. Broad absorption bandwidth with RL below-10 d B could achieve 6.0 GHz and 6.7 GHz for C@Co and C@Ni Co composites with a thin 2.1 mm thickness, respectively. Our exciting findings might lead a guide on the novel structure design for the functional core-shell structural composites used for microwave absorption.
基金financially supported by the National Natural Science Foundation of China(No.51772275)。
文摘A novel entropy-stabilized(ES)(Ca,Sr,Ba)ZrO_(3) ceramic has been designed and synthesized by pressureless sintering of CaZr03,SrZr03 and BaZr03 powders mixtures at 1450℃,1500℃and 1550℃for 3 h.X-ray diffraction,scanning electron microscopy and transmission electron microscopy analyses collectively indicate that a single solid solution is formed with a homogeneous distribution of metal elements after sintering at 1550℃.The relative density and hardness of the ES(Ca,Sr,Ba)ZrO_(3) ceramic sintered at 1550℃are 97.79%and 10.840.33 GPa,re s pectively.This ES(Ca,Sr,Ba)ZrO_(3) exhibits lower thermal conductivity from 373 K to 1073 K than their constituting zirconates,CaZrO_(3),SrZrO_(3) and BaZrO_(3).Most importantly,the ES(Ca,Sr,Ba)ZrO_(3) ceramic possesses good corrosion resistance to TiNi alloy melt and no distinct reaction layer exists between TiNi alloy and ES(Ca,Sr,Ba)ZrO_(3) ceramic in the contact region.The combination of these properties indicates that ES(Ca,Sr,Ba)ZrO_(3) ceramic is promising for use as a novel crucible material for the melting of titanium alloys.
基金financially supported by the National Natural Science Foundation of China(Nos.U2004177 and 21504082)Zhongyuan Thousand Talents Plan Project,Outstanding Youth Fund of Henan Province(No.212300410081)Natural Science Research Project of Henan Educational Committee(No.20A43001)。
文摘Semiconductor-noble metal composite has become a research focus due to its superior performance compared with its respective component.Although various methods have been developed to synthesize semiconductor-noble metal heterostructures,most of them are relatively complex multistep and use toxic reactants of high cost and risk.In this work,a series of Cu_(2)O/Ag heterojunctions were quickly prepared in one step via simple microwave-assisted green route.XRD,SEM,TEM,EDS,XPS,etc.were used to characterize obtained products,and the results indicate a Cu_(2)O/Ag metal-semiconductor heterojunction in micro-nano size was fabricated successfully.In addition,antibacterial behavior of Cu_(2)O/Ag heterojunctions against E.coli and S.aureus were investigated.Owing to the synergistic effect of Cu_(2)O and Ag,the heterojunction exhibits much better antibacterial performance than the pristine Cu_(2)O does.This work provides new insights into the green design and fabrication of surface-modified Cu_(2)O hybrid multifunctional materials for antibacterial applications.
基金Joint Fund of Research and Development Program of Henan Province,Grant/Award Number:222301420002National Natural Science Foundation of China,Grant/Award Number:U21A2064Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province,Grant/Award Number:22HASTIT001。
文摘Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric constant of Ti_(3)C_(2)T_(x)MXene,we have successfully synthesized core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres.This architecture,comprising SiO_(2) as the core,MXene as the intermediate layer,and MoS_(2) as the outer shell,is achieved through an electrostatic self‐assembly method combined with a hydrothermal process.This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS_(2) nanosheets.Notably,the synergistic combination of SiO_(2) and MoS_(2) with highly conductive MXene enables the suitable dielectric constant of the composites,ensuring optimal impedance matching.Therefore,the core‐shell structured SiO_(2)@MXene@MoS_(2) nanospheres exhibit excellent EMW absorption performance,featuring a remarkable minimum reflection loss(RL_(min))of−52.11 dB(2.4 mm).It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth(EAB)of 6.72 GHz.This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by“wide bandwidth and strong reflection loss.”
基金financially supported by the National Natural Science Foundation of China(No.51802289)the Science Foundation for the Excellent Youth Scholars of Henan Province(No.212300410089)+2 种基金the Support Program for Scientific and Technological Innovation Talents of Higher Education in Henan Province(No.21HASTIT004)the China Postdoctoral Science Foundation(No.2019M661352)the Natural Science Basic Research Program in Shaanxi Province(No.202032100067)。
文摘Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials,particularly when adjustment of the constitution or mixing ratio is limited.In this study,bowl-like and honeycomb titanium dioxide/carbon nanotube(TiO_(2)/CNT)composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration,respectively.Compared to the honeycomb structure,the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization,and augmented multiple reflections.The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics.The bowl-like TiO_(2)/CNT composite exhibited a minimum reflection loss(RL_(min))of-38.6 dB(1.5 mm)with a wide effective absorption band(EAB;<-10 dB)of4.2 GHz,while the honeycomb TiO_(2)/CNT composite showed an RLminof-34.8 dB(2.1 mm)with an EAB of 4.3 GHz.The required mixing ratio in the matrix was only 15 wt%,outperforming that of the most closely related composites.Thus,both the bowl-like and honeycomb TiO_(2)/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.
基金supported by the National Natural Science Foundation of China(No.U2004177)the Henan Province Science and Technology Research and Development Project in 2020,China(No.202300410491)the Key Scientific Research Projects of Provincial Universities in 2021,China(No.21A430045)。
文摘With the gradually increasing protection awareness about electromagnetic pollution,the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention.In this work,composites consisting of straw-derived biochar combined with NiCo alloy were successfully fabricated through high-temperature carbonization and subsequent hydrothermal reaction.The electromagnetic parameters of the porous biocarbon/NiCo composites can be effectively modified by altering their NiCo content,and their improved absorbing performance can be attributed to the synergy effect of magnetic-dielectric characteristics.An exceptional reflection loss of-27.0 dB at 2.2 mm thickness and an effective absorption bandwidth of 4.4 GHz(11.7-16.1 GHz)were achieved.These results revealed that the porous biocarbon/NiCo composites could be used as a new generation absorbing material because of their low density,light weight,excellent conductivity,and strong absorption.
基金National Natural Science Foundation of China,Grant/Award Numbers:52171033,52301263,U23A20574SEU Innovation Capability Enhancement Plan for Doctoral Students,Grant/Award Number:CXJH_SEU 24148。
文摘One-dimensional(1D)metals are well known for their exceptional conductivity and their ease of formation of interconnected networks that facilitate electron migration,making them promising candidates for electromagnetic(EM)attenuation.However,the impedance mismatch from high conductivity and their singular mode of energy loss hinder effective EM wave dissipation.Construction of cable structures not only optimizes impedance matching but also introduces a multitude of heterojunctions,increasing attenuation modes and potentially enhancing EM wave absorption(EMA)performance.Herein,we showcase the scalable synthesis of tin(Sn)whiskers from a Ti_(2)SnC MAX phase precursor,followed by creation of a 1D tin@carbon(Sn@C)cable structure through polymerization of PDA on their surface and annealing in argon.The EMA capabilities of Sn@C significantly surpass those of uncoated Sn whiskers,with an effective absorption bandwidth reaching 7.4 GHz.Remarkably,its maximum radar cross section reduction value of 27.85 dBm2 indicates its exceptional stealth capabilities.The enhanced EMA performance is first attributed to optimized impedance matching,and furthermore,the Sn@C cable structures have rich SnO2/C and Sn/SnO2 heterointerfaces and the associated defects,which increase interfacial and defect-induced polarization losses,as visually demonstrated by off-axis electron holography.The development of the Sn@C cable structure represents a notable advancement in broadening the scope of materials with potential applications in stealth technology,and this study also contributes to the understanding of how heterojunctions can improve EMA performance.
基金supported by the National Natural Science Foundation of China(Nos.U24A20101 and 52202072)the Natural Science Foundation Outstanding Youth Fund Project of Henan Province(No.242300421009)+3 种基金the Natural Science Foundation of Henan Province(No.242300421056),the China Postdoctoral Science Foundation(No.2024M760816)the Henan Province Science and Technology Research Project(No 252102231066)the Youth Research Funds Plan of Zhengzhou University of Aeronautics(No.25ZHQN01020)the Henan Province Engineering Research Center of Efficient Use of New Energy of Low Carbon Technologies(No.JDDT2024-09).
文摘One-dimensional tantalum carbide(TaC)nanorodsare considered promising candidates for high-temperature electromagnetic wave(EMW)absorption because of their intrinsically high electrical conductivity and exceptional thermal stability.However,conventional synthesis approaches typically yield products with low quality and poor efficiency,limiting their practical applicability.Here,we report the rapid and scalable synthesis of high-quality TaC nanorods via a molten salt-assisted carbothermal reduction strategy integrated with microwave heating.The formation of well-defined one-dimensional TaC nanorods was achieved within 20 min at 1300℃by precisely tuning the precursor composition(Ta_(2)Os:C:NaCl:Ni=1:8:2:0.08).The resulting TaC nanorods exhibit notable EMW absorption properties,with a maximum effective absorption bandwidth(EABma)of 3.0 GHz at a simulated thickness of 1.0 mm and a minimum reflection loss(RLmin)of-30.5 dB.Off-axis electron holography reveals pronounced charge accumulation at the Ta_(2)Os shell/TaC core interface,indicative of interfacial polarization effects.Furthermore,radar scattering cross-section(RCs)l simulations demonstrate substantial attenuation of the backscattered signal from a perfect electric conductor(PEC)substratel coated with the TaC layer,with the strongest electromagnetic energy dissipation observed at a coating thickness ofl 1.0 mm.These results underscore the viability of microwave-assisted synthesis as an efficient and sustainable route for producing high-performance TaC nanorods for EMW absorption applications under extreme thermal conditions.
文摘With the rapid advancement of information technology,electromagnetic radiation has become deeply integrated into nearly every aspect of modern life,from personal communication and industrial manufacturing to aerospace and national defense infrastructures.As the electromagnetic environment has become increasingly complex and congested,electromagnetic waves have not only brought unprecedented convenience but also introduced serious challenges,including electromagnetic interference,radiation pollution,and information insecurity.Consequently,the rational design and development of microwave absorption materials(MAMs)are critically important for protecting human health,mitigating electromagnetic pollution,and strengthening information security in the information age.
基金supported by the National Natural Science Foundation of China(No.52572086)the Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province(No.22HASTIT001)the Henan Province Natural Science Foundation Outstanding Youth Fund Project(No.242300421009).
文摘Despite the extensive research conducted on dielectric-magnetic coupling in metal-organic frameworks(MOF)-derived absorbers,the underlying mechanisms associated with defects,interfaces,and orbital hybridization remain inadequately investigated.To address this,we developed coral-like MOF-derived nickel-phosphorous@carbon(NP@C)nanocomposites by adjusting the pyrolysis temperature,revealing for the first time the link between structure and electromagnetic(EM)performance.The composite features nickel phosphide nanoparticles(Ni_(12)P_(5) core/Ni_(2)P shell)embedded in an amorphous carbon matrix,where a unique crystal orientation and interfacial coupling enhance EM wave dissipation.The calculations show that charge transfer(0.66e)at the C-Ni_(12)P_(5) interface increases conductance loss,whereas the C-Ni_(2)P-Ni_(12)P_(5) heterostructure generates interfacial polarization and defect states via negative charge transfer(0.20e),synergistically enhancing dielectric and magnetic loss.Electronic structure analysis revealed that sharp Ni 3d orbital peaks near the Fermi level coexist with broad carbon matrix peaks,enabling both conductive and spin-related magnetic loss mechanisms.The NP@C nanocomposite achieves a reflection loss of −54.1 dB and an effective absorption band covering 4.1 GHz at a thin thickness of 1.37 mm.This study clarifies the atomic-and electronic-level EM response mechanisms of MOF-derived carbon materials,offering new insights for designing high-performance absorbers.
基金supported by the National Natural Science Foundation of China(Nos.52572086 and 52502371)the Natural Science Foundation of Henan(No.242300421010)+1 种基金the Henan Province Natural Science Foundation Outstanding Youth Fund Project(No.242300421009)the Henan Province Science and Technology Research Project(No.252102230037).
文摘Ceramic-based electromagnetic interference(EMI)shielding materials have emerged as promising solutions because of their tunable dielectric and magnetic properties,excellent chemical stability,and favorable cost‒performance ratio.Despite their advantages,enhancing electrical conductivity and optimizing microstructural design remain key technical challenges.This review presents a systematic analysis of the working mechanisms,advanced fabrication techniques,and performance optimization strategies for ceramic-based EMI shielding materials.This study provides an in-depth analysis of the key factors influencing shielding efficiency and discusses the shielding mechanisms and performance enhancement strategies for both conventional ceramics(e.g.,silicon carbide and ferrites)and advanced ceramics(e.g.,MXenes and high-entropy ceramics).Future research directions are identified,including wideband shielding design to meet the requirements of 5G and terahertz communication;the integration of mechanical,thermal,and electromagnetic functionalities;and the development of intelligent,responsive materials.Additionally,this review highlights the potential of machine learning(ML)and artificial intelligence(AI)in accelerating material design and performance optimization.By critically analyzing the interrelationships among material properties,fabrication processes,and shielding mechanisms,this work offers a comprehensive perspective on the innovative application of advanced ceramics in EMI shielding,with the aim of bridging the gap between fundamental research and industrial implementation.
基金supported by the National Key R&D Program of China(No.2023YFB3712600)the National Natural Science Foundation of China(No.52171009).
文摘Transition metal carbides exhibit outstanding mechanical properties but suffer from a critical hardness-toughness trade-off.Spinodal decomposition-mediated phase separation,induced by high-temperature aging,is an effective strategy for enhancing the mechanical properties of carbide ceramics.However,the typically high stacking fault energy in carbide ceramics restricts the dislocation pinning effects of spinodal decomposition interfaces,hampering potential hardness and toughness improvements.Guided by first-principles calculations,this study employs(Ti,Zr)C carbide ceramics as a representative system and systematically lowers its stacking fault energy through nitrogen(N)incorporation.With optimized composition and controlled aging,distinct stacking faults emerged after short-term aging.As the aging time increased,these stacking faults progressively transformed into dislocation sources,facilitating dislocation multiplication.Mechanical testing revealed that samples incorporating 25%N followed by aging exhibited significant enhancements:The hardness and fracture toughness increased by approximately 40% and 50%,respectively,compared with those of the initial material.However,at higher N concentrations,excessive elastic strain energy accumulation induced lamellar thickening,diminishing the extent of improvement in hardness and toughness.This work designs a strategy to lower the stacking fault energy in carbide ceramics,overcoming its constraint on performance enhancement via spinodal decomposition and enabling hardness-toughness synergy via spinodal decomposition through theoretical and processing solutions.
基金financially supported by the National Natural Science Foundation of China(Nos.52372029,U22A20127,52304356,52102028,and 92263205)the Key Research and Development Plan Project in Hubei Province(No.2023BCB100).
文摘Ca^(2+)/Cr^(3+)co-doped LaAlO_(3) infrared(IR)ceramics have been proven to be potential energy-saving materials for high-temperature industries because of their high emissivity and high-temperature stability.However,Cr^(6+)formation commonly occurs in materials and poses environmental and health risks,such as Cr^(6+)dissolution in water and CrO_(3)(g)volatilization.In this study,we combined high emissivity with in situ detoxification by introducing residual Al_(2)O_(3) into Ca^(2+)/Cr^(3+)co-doped LaAlO_(3) ceramics.Compared with the undoped ceramics,the addition of 20 wt%residual Al_(2)O_(3) resulted in a 78.5%reduction to 18.44 mg/kg(lower than the EU standard of 20 mg/kg)in Cr^(6+)dissolution and a decrease in 77.8%CrO_(3)(g)volatilization.This significant detoxification effect can be attributed to the formation of CaAl_(12−x)Cr_(x)O_(19).Additionally,as the residual Al_(2)O_(3) content increased from 5 to 20 wt%,the ceramics maintained high emissivity,above 0.896 in the near-infrared band and 0.781 in the mid-infrared band.Furthermore,the IR coating effectively increased the surface temperature(from 767.1 to 790.7℃/min)and the heat radiation of the heating source,increasing the heating rate from 31.7 to 34.6℃/min during water heating.This work offers a promising approach for designing environmentally friendly IR ceramics with excellent IR performance for energy-saving applications in the high-temperature industry.
基金supported by the Natural Science Foundation Outstanding Youth Fund Project of Henan Province(No.242300421009)the Henan Provincial Science and Technology Research Project(Nos.241111232800 and 232102230115)+1 种基金the Joint Fund of Research and Development Program of Henan Province(No.222301420002)the National Natural Science Foundation of China(No.U21A2064).
文摘Multi-component occupancies of perovskite materials(ABO_(3))have brought diverse crystallographic distortions and highly tunable defect structures.These structural features enable ABO_(3)to have customizable dielectric and magnetic properties,offering new opportunities for advancing microwave absorbing materials.In this study,entropy-driven strategies,including composition optimization,structural/defective design,microstructure engineering,and microwave absorption simulation,are proposed to improve the microwave absorption capacity of(Ba_(1/3)Sr_(1/3)Ca_(1/3))FeO_(3).The hexagonal perovskite structure(Ba_(1/3)Sr_(1/3)Ca_(1/3))FeO_(3)prepared at 1100℃exhibits exceptional electromagnetic wave absorption properties,with a minimum reflection loss of−40.58 dB at a thickness of 1.2 mm and a maximum effective absorption bandwidth of 4.16 GHz.The results indicate that the interconnection of octahedra,and structural distortions,oxygen vacancies,and other defects enhance the dielectric polarization of the material,leading to excellent wave absorption performance.The entropy-driven design strategy for perovskite ABO_(3)materials offers valuable insights for the development of advanced electromagnetic wave absorption materials.
基金This work was supported by the National Natural Science Foundation of China(No.22269010)the Jiangxi Provincial Natural Science Foundation(No.20224BAB214021)+3 种基金the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province(No.20212BCJ23020)the Science and Technology Project of Jiangxi Provincial Department of Education(No.GJJ211305)the National Natural Science Foundation of China(No.U2004177)the Outstanding Youth Fund of Henan Province(No.212300410081).
文摘Two-dimensional(2D)transition metal carbides(MXene)possess attractive conductivity and abundant surface functional groups,providing immense potential in the field of electromagnetic wave(EMW)absorption.However,high conductivity and spontaneous aggregation of MXene suffer from limited EMW response.Inspired by dielectric–magnetic synergy effect,the strategy of decorating MXene with magnetic elements is expected to solve this challenge.In this work,zigzag-like Mo_(2)TiC_(2)–MXene nanofibers(Mo-based MXene(Mo–MXene)NFs)with cross-linked networks are fabricated by hydrofluoric acid(HF)etching and potassium hydroxide(KOH)shearing processes.Subsequently,Co-metal–organic framework(MOF)and derived CoNi layered double hydroxide(LDH)ultrathin nanosheets are grown inside Mo–MXene NFs,and the N-doped carbon matrix anchored by CoNi alloy nanoparticles formed by pyrolysis is firmly embedded in the Mo–MXene NFs network.Benefiting from synergistic effect of highly dispersed small CoNi alloy nanoparticles,a three-dimensional(3D)conductive network assembled by zigzag-like Mo–MXene NFs,numerous N-doped hollow carbon vesicles,and abundant dual heterogeneous interface,the designed Mo–MXene/CoNi–NC heterostructure provides robust EMW absorption ability with a reflection loss(RL)value of−68.45 dB at the thickness(d)of 4.38 mm.The robust EMW absorption performance can be attributed to excellent dielectric loss,magnetic loss,impedance matching(Z),and multiple scattering and reflection triggered by the unique 3D network structure.This work puts up great potential in developing advanced MXene-based EMW absorption devices.
