Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,an...Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,and thermal properties.To maximize the utilization of graphene’s in-plane properties,pre-constructed and aligned structures,such as oriented aerogels,films,and fibers,have been designed.The unique combination of aligned structure,high surface area,excellent electrical conductivity,mechanical stability,thermal conductivity,and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions,enabling advancements in diverse fields.This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites.It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively.The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties,showing enhanced electrical,mechanical,and thermal properties along the alignment at the sacrifice of the perpendicular direction.This review showcases remarkable properties and applications of aligned graphene aerogels and their composites,such as their suitability for electronics,environmental applications,thermal management,and energy storage.Challenges and potential opportunities are proposed to offer new insights into prospects of this material.展开更多
Meniscal injury,a prevalent and challenging medical condition,is characterized by poor self-healing potential and a complex microenvironment.Tissue engineering scaffolds,particularly those made of silk fibroin(SF)/hya...Meniscal injury,a prevalent and challenging medical condition,is characterized by poor self-healing potential and a complex microenvironment.Tissue engineering scaffolds,particularly those made of silk fibroin(SF)/hyaluronic acid methacryloyl(HAMA)and encapsulating Mg^(2+),are promising options for meniscal repair.However,the inflammatory response following implantation is a significant concern.In this study,we prepared a composite SF/HAMA-Mg hydrogel scaffold,evaluated its physical and chemical properties,and detected its fibrochondrogenic differentiation effect in vitro and the healing effect in a rabbit meniscus defect model in vivo.Our results showed that the scaffold differentiates pro-inflammatory M1 macrophages into anti-inflammatory M2 macrophages after implantation,thereby reducing inflammation and facilitating the growth and repair of meniscus tissue.Further,the composite scaffold provided a conducive milieu for cell proliferation,anticipatory differentiation,and generation of extracellular matrix.In summary,composite SF/HAMA-Mg scaffolds exhibit exceptional biocompatibility and anti-inflammatory properties,demonstrating superior potential for meniscal repair.展开更多
The endeavor to attain prolonged stability and heightened electromagnetic interference shielding effec-tiveness(EMI SE)in polymer-matrix composites remains an arduous pursuit,particularly when subjected to external me...The endeavor to attain prolonged stability and heightened electromagnetic interference shielding effec-tiveness(EMI SE)in polymer-matrix composites remains an arduous pursuit,particularly when subjected to external mechanical trauma or adverse environmental conditions.In this context,a self-healing and efficient EMI shielding polycaprolactone(PCL)composite with a unique electromagnetic gradient and interface-metalized segregated structure is assembled through layer-by-layer casting and a hot-pressing process.The combined effect of the induction of the electromagnetic gradient layer and the massive mul-tiple interface reflection and scattering from the segregated-like structure results in an exceptional EMI SE of 57.0 dB and a low reflection(R)value of only 0.28.Additionally,the composite boasts impressive photothermal and electrothermal properties,allowing for self-healing under solar irradiation or electri-cal stimulation.Remarkably,this self-healing capability has been demonstrated through five cutting and healing cycles,exhibiting an impressive EMI SE retention rate of 88%.Consequently,the composite with rapid photo/electro-driven self-healing properties will be able to maintain EMI shielding performance.展开更多
Self-healing(SH)polymeric composites hold the promise of revolutionizing material performance and durability,but the challenge lies in achieving a delicate balance between healing efficiency and mechanical strength.He...Self-healing(SH)polymeric composites hold the promise of revolutionizing material performance and durability,but the challenge lies in achieving a delicate balance between healing efficiency and mechanical strength.Healing processes typically require dynamic,reversible bonds,which can weaken overall material strength,whereas robust materials rely on strong covalent bonds that resist healing.2D materials offer a solution by acting as nanofillers that not only improve mechanical properties but also introduce multifunctional benefits like electrical and thermal conductivity,responsiveness to stimuli,and enhanced barrier properties.Depending on their surface chemistry,thesematerials can either actively participate in the healing process or passively reinforce the polymer matrix.This review examines recent advancements in SH polymer composites enhanced with 2D fillers,exploring how factors like filler type,surface interactions,and loading levels impact both healing efficiency and mechanical strength.It compares the contributions of various 2D materials,identifying similarities and critical differences in their roles within polymermatrices.The article also highlights the need for standardized testing and advanced characterization techniques to better understand interfacial properties and healing mechanisms.By addressing current knowledge gaps and proposing future research directions,this review provides a comprehensive resource for advancing SH polymer systems,particularly in the integration of 2D materials for applications ranging from aerospace to electronics.展开更多
Piezoelectric silicon carbide(SiC)has been quite attractive due to its superior chemical and physical properties as well as wide potential applications.However,the inherent brittleness and unsatisfactory piezoelectric...Piezoelectric silicon carbide(SiC)has been quite attractive due to its superior chemical and physical properties as well as wide potential applications.However,the inherent brittleness and unsatisfactory piezoelectric response of piezoelectric semiconductors remain the major obstacles to their diversified applications.Here,flexible multifunctional PVDF/6H-SiC composite fiber films are fabricated and utilized to assemble both piezoelectric nanogenerators(PENGs)and stress/temperature/light sensors.The open cir-cuit voltage(V_(oc))and the density of short circuit current(I_(sc))of the PENG based on the PVDF/5 wt%6H-SiC composite fiber films reach 28.94 V and 0.24μA cm^(-2),showing a significant improvement of 240%and 300%compared with that based on the pure PVDF films.The effect of 6H-SiC nanoparticles(NPs)on inducing interfacial polarization and stress concentration in composite fiber films is proved by first-principles calculation and finite element analysis.The stress/temperature/light sensors based on the composite fiber film also show high sensitivity to the corresponding stimuli.This study shows that the PVDF/6H-SiC composite fiber film is a promising candidate for assembling high-performance energy harvesters and diverse sensors.展开更多
Recently,multifunctional materials have received widespread attention from researchers.Cellulose nanofibers(CNF)is one of biomass materials with abundant hydroxyl groups,which shows great potential in manufacturing mu...Recently,multifunctional materials have received widespread attention from researchers.Cellulose nanofibers(CNF)is one of biomass materials with abundant hydroxyl groups,which shows great potential in manufacturing multifunctional composite material.In this paper,a kind of polyaniline@CNF/polyvinyl alcohol-H_(2)SO_(4) multifunctional composite material(PANI@CNF/PVA-H_(2)SO_(4))was successfully designed by in-situ chemical polymerization of conductive polyaniline(PANI)onto CNF aerogel with high aspect ratio,and then coated with PVA-H_(2)SO_(4) gel.The composite material has a specific capacitance of 502.2 F/g at a scan rate of 5 mV/s as supercapacitor electrode.Furthermore,when the composite was assembled into a symmetrical supercapacitor,it can still provide an energy density of 11.49 W·h/kg at a high power density of 413.55 W/kg.Besides,the as-obtained PANI@CNF/PVA-H_(2)SO_(4) composite has an excellent electromagnetic shielding performance of 34.75 dB in X-band.In addition,due to the excellent flexibility of CNF and PVA,the PANI@CNF/PVA-H2SO4 composites can be further applied to stress sensors to detect pressure and human motion signals.展开更多
The rational design of composition and microstructure is a proven strategy for developing multifunctional high-performance electromagnetic wave(EMW)absorbers.In this study,a sandwich-structured multilayer nanoplate-li...The rational design of composition and microstructure is a proven strategy for developing multifunctional high-performance electromagnetic wave(EMW)absorbers.In this study,a sandwich-structured multilayer nanoplate-like Bi_(2)Fe_(4)O_(9)@Polypyrrole(BFO@PPy)heterostructure was successfully designed and fabricated using an efficient microwave hydrothermal method and an in situ polymerization process.Specifically,Bi_(2)Fe_(4)O_(9)enhances the chemical activity of ammonium persulfate,which in turn initiates the polymerization of pyrrole monomers,resulting in the formation of BFO@PPy heterostructures.The thickness of the PPy coating layer in the BFO@PPy composite can be precisely controlled at the nanoscale,optimizing electromagnetic parameters,conduction losses and interface polarization loss.The fabricated BFO@PPy composite achieves a minimum reflection loss(RL_(min))of-57.8 dB at a thickness of 2.5 mm and an effective absorption bandwidth(EAB)of 6.96 GHz.Furthermore,the EMW absorption performance and mechanism were systematically validated through theoretical calculations,radar cross-sectional simulations(RCS),and first-principles analysis.Notably,the RCS simulation of a 1:1 scale F-22 Raptor fighter model provides a realistic evaluation of the composite's EMW absorption potential in military applications.The efficient fabrication method and superior electromagnetic absorption performance make BFO@PPy a promising candidate for use in complex electromagnetic environments and military domains.Additionally,the BFO@PPy composite exhibits rapid electrothermal conversion at a low voltage(3V),achieving active infrared camouflage within a controllable temperature range,further highlighting its multifunctional properties.展开更多
Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from slugg...Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from sluggish electronic/ionic conductivities and huge volume variation, which severely deteriorate the rate capacities and cycling performances. Understanding the intrinsic reaction mechanism and further developing ideal TMC-based anode with high specific capacity, excellent rate capabilities, and longterm cycling stability are critical for the practical application of TMCs. In this review, we firstly focus on the fundamental electrochemical energy-storage mechanisms of TMCs, in terms of conversionreaction process, pseudocapacitance-type charge storage, valence change for charge storage and catalytic conversion mechanisms. Based on the reaction mechanisms, various modification strategies to improve the electrochemical performance of TMCs are summarized, covering:(i) micro-nano structural engineering, in which the influence factors on the morphology are discussed, and multiple architectures are listed;(ii) elemental doping, in which the intrinsic mechanisms of metal/nonmetal elements doping on the electrochemical performance are deeply explored;(iii) multifunctional compositing strategies, in which the specific affections on structure, electronic conductivity and chemo-mechanical stability are summarized.Finally, the key challenges and opportunities to develop high-performance TMCs are discussed and some solutions are also proposed. This timely review sheds light on the path towards achieving cost-effective and safe LIBs with high energy density and long cycling life using TMCs-based anode materials.展开更多
Dielectric polymers featuring high thermal conductivity,excellent mechanical,and stable dielectric properties over a broad temperature range have attracted extensive scientific attention.In this work,a large-scale,lay...Dielectric polymers featuring high thermal conductivity,excellent mechanical,and stable dielectric properties over a broad temperature range have attracted extensive scientific attention.In this work,a large-scale,layered film was fabricated using blade-coating approach,which integrated aramid nanofibers(ANFs)and boron nitride nanosheets(BNNSs)through a typical solgel transformation procedure.The as-prepared film with 20 wt.%BNNS displays high thermal conductivity(14.03 W·m^(−1)·K^(−1)),103-fold higher than pure ANF film,attributing to massive continuous thermal conduction pathway between BNNSs so as to facilitate fast phonon transmission.The film boasts excellent mechanical properties(stress 97.14±5.17 MPa,strain 19.36±0.35%),high degradation temperature(~542℃),a moderate dielectric constant(~6.9 at 104 Hz),together with low dielectric loss(~0.026 at 104 Hz).Meanwhile,the film reveals high breakdown voltage(310 MV·m^(−1))and volume resistivity(1013Ω·cm).Notably,these dielectric properties remain largely unchanged over a wide temperature range(25 to 200℃).展开更多
The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle an...The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle and aerospace component.In this study,to build a low-voltage activating,fast responding ETA,a robust and flexible carbon nanotube film(CNTF)with excellent electrical and thermal conductivity was adopted as the conductive material.Then,an asymmetric bilayer structured ETA was manufactured by coating a thin layer of polydimethylsiloxane(PDMS)with high coefficient of thermal expansion(9.3×10^(-4)℃^(−1)),low young’s modulus(2.07 MPa)on a thin CNTF(~11μm).The as-produced CNTF/PDMS composite ETA exhibited a large deformation(bending angle~324°)and high electro heating performance(351℃)at a low driving voltage of 8 V within~12 s.The actuated movement and the generated heat could be controlled by adjusting the driving voltages and showed almost the same values in 20 cycles.Furthermore,the influences of the PDMS thickness and driving voltage on CNTF/PDMS composite ETA performance were systematically investigated.The CNTF/PDMS soft robotic hand which can lift 5.1 times and crab 1.3 times of its weight demonstrated its potential capability.展开更多
Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects,substantial tumor recurrence,and long-lasting bone reconstruction post tumor resection.Magnesium and...Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects,substantial tumor recurrence,and long-lasting bone reconstruction post tumor resection.Magnesium and its alloys have recently emerged in clinics as orthopedics implantable metals but mostly restricted to mechanical devices.Here,by deposition of calcium-based bilayer coating on the surface,a Mg-based composite implant platform is developed with tailored degradation characteristics,simultaneously integrated with chemotherapeutic(Taxol)loading capacity.The delicate modulation of Mg degradation occurring in aqueous environment is observed to play dual roles,not only in eliciting desirable osteoinductivity,but allows for modification of tumor microenvironment(TME)owing to the continuous release of degradation products.Specifically,the sustainable H_(2) evolution and Ca^(2+) from the implant is distinguished to cooperate with local Taxol delivery to achieve superior antineoplastic activity through activating Cyt-c pathway to induce mitochondrial dysfunction,which in turn leads to significant tumor-growth inhibition in vivo.In addition,the local chemotherapeutic delivery of the implant minimizes toxicity and side effects,but markedly fosters osteogenesis and bone repair with appropriate structure degradation in rat femoral defect model.Taken together,a promising intraosseous administration strategy with biodegradable Mg-based implants to facilitate tumor-associated bone defect is proposed.展开更多
Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and ...Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and feasible technique,has been used to prepare shape memory polymer fbers(SMPFs)and expand their structures.SMPFs show some advanced features and functions in many felds.In this review,we give a comprehensive overview of SMPFs,including materials,fabrication methods,structures,multifunction,and applications.Firstly,the mechanism and characteristics of SMP are introduced.We then discuss the electrospinning method to form various microstructures,like non-woven fbers,core/shell fbers,hollow fbers and oriented fbers.Afterward,the multiple functions of SMPFs are discussed,such as multi-shape memory efect,reversible shape memory efect and remote actuation of composites.We also focus on some typical applications of SMPFs,including biomedical scafolds,drug carriers,self-healing,smart textiles and sensors,as well as energy harvesting devices.At the end,the challenges and future development directions of SMPFs are proposed.展开更多
Three-dimensional(3D)graphene is a promising active component for various engineering fields,but its performance is limited by the hidebound electrical conductivity levels and hindered electrical transport.Here we pre...Three-dimensional(3D)graphene is a promising active component for various engineering fields,but its performance is limited by the hidebound electrical conductivity levels and hindered electrical transport.Here we present a novel approach based on interlayer engineering,in which graphene oxide(GO)nanosheets are covalently functionalized with varied molecular lengths of diamine molecules.This has led to the creation of an unprecedented class of 3D graphene with highly adjustable electronic properties.Theoretical calculations and experimental results demonstrate that ethylenediamine,with its small diameter acting as a molecular bridge for facilitating electron transport,has the potential to significantly improve the electrical conductivity of 3D graphene.In contrast,butylene diamine,with its larger diameter,has a reverse effect due to the enlarged spacing of the graphene interlayers,resulting in conductive degradation.More importantly,the moderate conductive level of 3D graphene can be achieved by combining the interlayer spacing expansion effect and theπ-electronic donor ability of aromatic amines.The resulting 3D graphene exhibits highly tunable electronic properties,which can be easily adjusted in a wide range of 2.56-6.61 S·cm^(-1)compared to pristine GO foam(4.20 S·cm^(-1)).This opens up new possibilities for its use as an active material in a piezoresistive sensor,as it offers remarkable monitoring abilities.展开更多
基金The financial support by the National Natural Science Foundation of China(No.52002020)is acknowledged.
文摘Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,and thermal properties.To maximize the utilization of graphene’s in-plane properties,pre-constructed and aligned structures,such as oriented aerogels,films,and fibers,have been designed.The unique combination of aligned structure,high surface area,excellent electrical conductivity,mechanical stability,thermal conductivity,and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions,enabling advancements in diverse fields.This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites.It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively.The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties,showing enhanced electrical,mechanical,and thermal properties along the alignment at the sacrifice of the perpendicular direction.This review showcases remarkable properties and applications of aligned graphene aerogels and their composites,such as their suitability for electronics,environmental applications,thermal management,and energy storage.Challenges and potential opportunities are proposed to offer new insights into prospects of this material.
基金supported by grants from the Beijing Natural Science Foundation,China(No.7244431)the Postdoctoral Science Foundation of China(No.2022M710260)the National Natural Science Foundation of China(No.82202723).
文摘Meniscal injury,a prevalent and challenging medical condition,is characterized by poor self-healing potential and a complex microenvironment.Tissue engineering scaffolds,particularly those made of silk fibroin(SF)/hyaluronic acid methacryloyl(HAMA)and encapsulating Mg^(2+),are promising options for meniscal repair.However,the inflammatory response following implantation is a significant concern.In this study,we prepared a composite SF/HAMA-Mg hydrogel scaffold,evaluated its physical and chemical properties,and detected its fibrochondrogenic differentiation effect in vitro and the healing effect in a rabbit meniscus defect model in vivo.Our results showed that the scaffold differentiates pro-inflammatory M1 macrophages into anti-inflammatory M2 macrophages after implantation,thereby reducing inflammation and facilitating the growth and repair of meniscus tissue.Further,the composite scaffold provided a conducive milieu for cell proliferation,anticipatory differentiation,and generation of extracellular matrix.In summary,composite SF/HAMA-Mg scaffolds exhibit exceptional biocompatibility and anti-inflammatory properties,demonstrating superior potential for meniscal repair.
基金supported by the Sichuan Science and Technology Program(Nos.2023YFG0210,2022YFG0276,24NSFSC1700).
文摘The endeavor to attain prolonged stability and heightened electromagnetic interference shielding effec-tiveness(EMI SE)in polymer-matrix composites remains an arduous pursuit,particularly when subjected to external mechanical trauma or adverse environmental conditions.In this context,a self-healing and efficient EMI shielding polycaprolactone(PCL)composite with a unique electromagnetic gradient and interface-metalized segregated structure is assembled through layer-by-layer casting and a hot-pressing process.The combined effect of the induction of the electromagnetic gradient layer and the massive mul-tiple interface reflection and scattering from the segregated-like structure results in an exceptional EMI SE of 57.0 dB and a low reflection(R)value of only 0.28.Additionally,the composite boasts impressive photothermal and electrothermal properties,allowing for self-healing under solar irradiation or electri-cal stimulation.Remarkably,this self-healing capability has been demonstrated through five cutting and healing cycles,exhibiting an impressive EMI SE retention rate of 88%.Consequently,the composite with rapid photo/electro-driven self-healing properties will be able to maintain EMI shielding performance.
基金supported by the Ministry of Education,Singapore(Research Centre of Excellence award to the Institute for Functional Intelligent Materials,I-FIM,project No.EDUNC-33-18-279-V12)from the Royal Society(UK,grant number RSRP∖R∖190000).
文摘Self-healing(SH)polymeric composites hold the promise of revolutionizing material performance and durability,but the challenge lies in achieving a delicate balance between healing efficiency and mechanical strength.Healing processes typically require dynamic,reversible bonds,which can weaken overall material strength,whereas robust materials rely on strong covalent bonds that resist healing.2D materials offer a solution by acting as nanofillers that not only improve mechanical properties but also introduce multifunctional benefits like electrical and thermal conductivity,responsiveness to stimuli,and enhanced barrier properties.Depending on their surface chemistry,thesematerials can either actively participate in the healing process or passively reinforce the polymer matrix.This review examines recent advancements in SH polymer composites enhanced with 2D fillers,exploring how factors like filler type,surface interactions,and loading levels impact both healing efficiency and mechanical strength.It compares the contributions of various 2D materials,identifying similarities and critical differences in their roles within polymermatrices.The article also highlights the need for standardized testing and advanced characterization techniques to better understand interfacial properties and healing mechanisms.By addressing current knowledge gaps and proposing future research directions,this review provides a comprehensive resource for advancing SH polymer systems,particularly in the integration of 2D materials for applications ranging from aerospace to electronics.
基金supported by the National Science Fund for Distinguished Young Scholars(No.52025041)the National Natural Science Foundation of China(Nos.51902020,51974021,and 52250091)+2 种基金the Fundamental Research Funds for the Central Universities of NO.FRF-TP-20-02C2This project is supported by the S tate Key Laboratory of Featured Metal Materials and Lifecycle Safety for Composite Structures,Guangxi University(Grant No.2021GXYSOF12)the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(No.FRF-IDRY-21-028).
文摘Piezoelectric silicon carbide(SiC)has been quite attractive due to its superior chemical and physical properties as well as wide potential applications.However,the inherent brittleness and unsatisfactory piezoelectric response of piezoelectric semiconductors remain the major obstacles to their diversified applications.Here,flexible multifunctional PVDF/6H-SiC composite fiber films are fabricated and utilized to assemble both piezoelectric nanogenerators(PENGs)and stress/temperature/light sensors.The open cir-cuit voltage(V_(oc))and the density of short circuit current(I_(sc))of the PENG based on the PVDF/5 wt%6H-SiC composite fiber films reach 28.94 V and 0.24μA cm^(-2),showing a significant improvement of 240%and 300%compared with that based on the pure PVDF films.The effect of 6H-SiC nanoparticles(NPs)on inducing interfacial polarization and stress concentration in composite fiber films is proved by first-principles calculation and finite element analysis.The stress/temperature/light sensors based on the composite fiber film also show high sensitivity to the corresponding stimuli.This study shows that the PVDF/6H-SiC composite fiber film is a promising candidate for assembling high-performance energy harvesters and diverse sensors.
基金supported by the fund of National Natural Science Foundation of China(22078184,22378249 and 22178208)Key R&D Plan of Shaanxi Province(2024GX-YBXM-335)+1 种基金China Postdoctoral Science Foundation(2019M653853XB)Natural science advance research foundation of Shaanxi University of Science and Technology(2018QNBJ-03).
文摘Recently,multifunctional materials have received widespread attention from researchers.Cellulose nanofibers(CNF)is one of biomass materials with abundant hydroxyl groups,which shows great potential in manufacturing multifunctional composite material.In this paper,a kind of polyaniline@CNF/polyvinyl alcohol-H_(2)SO_(4) multifunctional composite material(PANI@CNF/PVA-H_(2)SO_(4))was successfully designed by in-situ chemical polymerization of conductive polyaniline(PANI)onto CNF aerogel with high aspect ratio,and then coated with PVA-H_(2)SO_(4) gel.The composite material has a specific capacitance of 502.2 F/g at a scan rate of 5 mV/s as supercapacitor electrode.Furthermore,when the composite was assembled into a symmetrical supercapacitor,it can still provide an energy density of 11.49 W·h/kg at a high power density of 413.55 W/kg.Besides,the as-obtained PANI@CNF/PVA-H_(2)SO_(4) composite has an excellent electromagnetic shielding performance of 34.75 dB in X-band.In addition,due to the excellent flexibility of CNF and PVA,the PANI@CNF/PVA-H2SO4 composites can be further applied to stress sensors to detect pressure and human motion signals.
基金financially supported by the Natural Science Foundation of China(NSFC,No.22165032)Beijing Natural Science Foundation(No.2242032)
文摘The rational design of composition and microstructure is a proven strategy for developing multifunctional high-performance electromagnetic wave(EMW)absorbers.In this study,a sandwich-structured multilayer nanoplate-like Bi_(2)Fe_(4)O_(9)@Polypyrrole(BFO@PPy)heterostructure was successfully designed and fabricated using an efficient microwave hydrothermal method and an in situ polymerization process.Specifically,Bi_(2)Fe_(4)O_(9)enhances the chemical activity of ammonium persulfate,which in turn initiates the polymerization of pyrrole monomers,resulting in the formation of BFO@PPy heterostructures.The thickness of the PPy coating layer in the BFO@PPy composite can be precisely controlled at the nanoscale,optimizing electromagnetic parameters,conduction losses and interface polarization loss.The fabricated BFO@PPy composite achieves a minimum reflection loss(RL_(min))of-57.8 dB at a thickness of 2.5 mm and an effective absorption bandwidth(EAB)of 6.96 GHz.Furthermore,the EMW absorption performance and mechanism were systematically validated through theoretical calculations,radar cross-sectional simulations(RCS),and first-principles analysis.Notably,the RCS simulation of a 1:1 scale F-22 Raptor fighter model provides a realistic evaluation of the composite's EMW absorption potential in military applications.The efficient fabrication method and superior electromagnetic absorption performance make BFO@PPy a promising candidate for use in complex electromagnetic environments and military domains.Additionally,the BFO@PPy composite exhibits rapid electrothermal conversion at a low voltage(3V),achieving active infrared camouflage within a controllable temperature range,further highlighting its multifunctional properties.
基金financially supported by the National Natural Science Foundation of China(51802091,51902102,22075074,U21A2081)the Outstanding Young Scientists Research Funds from Hunan Province(2020JJ2004)+3 种基金the Major Science and Technology Program of Hunan Province(2020WK2013)the China Postdoctoral Science Foundation(2020 M672478)the Natural Science Foundation of Hunan Province(2020JJ5035,2021JJ40047,2020JJ5042)the Major Science and Technology Program of Changsha(kq1804010)。
文摘Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from sluggish electronic/ionic conductivities and huge volume variation, which severely deteriorate the rate capacities and cycling performances. Understanding the intrinsic reaction mechanism and further developing ideal TMC-based anode with high specific capacity, excellent rate capabilities, and longterm cycling stability are critical for the practical application of TMCs. In this review, we firstly focus on the fundamental electrochemical energy-storage mechanisms of TMCs, in terms of conversionreaction process, pseudocapacitance-type charge storage, valence change for charge storage and catalytic conversion mechanisms. Based on the reaction mechanisms, various modification strategies to improve the electrochemical performance of TMCs are summarized, covering:(i) micro-nano structural engineering, in which the influence factors on the morphology are discussed, and multiple architectures are listed;(ii) elemental doping, in which the intrinsic mechanisms of metal/nonmetal elements doping on the electrochemical performance are deeply explored;(iii) multifunctional compositing strategies, in which the specific affections on structure, electronic conductivity and chemo-mechanical stability are summarized.Finally, the key challenges and opportunities to develop high-performance TMCs are discussed and some solutions are also proposed. This timely review sheds light on the path towards achieving cost-effective and safe LIBs with high energy density and long cycling life using TMCs-based anode materials.
基金the National Natural Science Foundation of China(No.22075161).
文摘Dielectric polymers featuring high thermal conductivity,excellent mechanical,and stable dielectric properties over a broad temperature range have attracted extensive scientific attention.In this work,a large-scale,layered film was fabricated using blade-coating approach,which integrated aramid nanofibers(ANFs)and boron nitride nanosheets(BNNSs)through a typical solgel transformation procedure.The as-prepared film with 20 wt.%BNNS displays high thermal conductivity(14.03 W·m^(−1)·K^(−1)),103-fold higher than pure ANF film,attributing to massive continuous thermal conduction pathway between BNNSs so as to facilitate fast phonon transmission.The film boasts excellent mechanical properties(stress 97.14±5.17 MPa,strain 19.36±0.35%),high degradation temperature(~542℃),a moderate dielectric constant(~6.9 at 104 Hz),together with low dielectric loss(~0.026 at 104 Hz).Meanwhile,the film reveals high breakdown voltage(310 MV·m^(−1))and volume resistivity(1013Ω·cm).Notably,these dielectric properties remain largely unchanged over a wide temperature range(25 to 200℃).
基金supported by This work was financially supported by the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials as well as the Fundamental Research Fund of Shanghai Natural Science Foundation(Grant No.17ZR1400800).
文摘The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle and aerospace component.In this study,to build a low-voltage activating,fast responding ETA,a robust and flexible carbon nanotube film(CNTF)with excellent electrical and thermal conductivity was adopted as the conductive material.Then,an asymmetric bilayer structured ETA was manufactured by coating a thin layer of polydimethylsiloxane(PDMS)with high coefficient of thermal expansion(9.3×10^(-4)℃^(−1)),low young’s modulus(2.07 MPa)on a thin CNTF(~11μm).The as-produced CNTF/PDMS composite ETA exhibited a large deformation(bending angle~324°)and high electro heating performance(351℃)at a low driving voltage of 8 V within~12 s.The actuated movement and the generated heat could be controlled by adjusting the driving voltages and showed almost the same values in 20 cycles.Furthermore,the influences of the PDMS thickness and driving voltage on CNTF/PDMS composite ETA performance were systematically investigated.The CNTF/PDMS soft robotic hand which can lift 5.1 times and crab 1.3 times of its weight demonstrated its potential capability.
基金supported by the National Key Research&Development Program of China(2021YFE0204900)the National Natural Science Foundation of China(52222108)Science and Technology Commission of Shanghai Municipality(22ZR1432000,23JC1402400).
文摘Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects,substantial tumor recurrence,and long-lasting bone reconstruction post tumor resection.Magnesium and its alloys have recently emerged in clinics as orthopedics implantable metals but mostly restricted to mechanical devices.Here,by deposition of calcium-based bilayer coating on the surface,a Mg-based composite implant platform is developed with tailored degradation characteristics,simultaneously integrated with chemotherapeutic(Taxol)loading capacity.The delicate modulation of Mg degradation occurring in aqueous environment is observed to play dual roles,not only in eliciting desirable osteoinductivity,but allows for modification of tumor microenvironment(TME)owing to the continuous release of degradation products.Specifically,the sustainable H_(2) evolution and Ca^(2+) from the implant is distinguished to cooperate with local Taxol delivery to achieve superior antineoplastic activity through activating Cyt-c pathway to induce mitochondrial dysfunction,which in turn leads to significant tumor-growth inhibition in vivo.In addition,the local chemotherapeutic delivery of the implant minimizes toxicity and side effects,but markedly fosters osteogenesis and bone repair with appropriate structure degradation in rat femoral defect model.Taken together,a promising intraosseous administration strategy with biodegradable Mg-based implants to facilitate tumor-associated bone defect is proposed.
基金This work is funded by the National Natural Science Foundation of China(Grant No.11632005,11802075)This work was also supported by the China Postdoctoral Science Foundation funded project.
文摘Shape memory polymer(SMP)is a kind of material that can sense and respond to the changes of the external environment,and its behavior is similar to the intelligent refection of life.Electrospinning,as a versatile and feasible technique,has been used to prepare shape memory polymer fbers(SMPFs)and expand their structures.SMPFs show some advanced features and functions in many felds.In this review,we give a comprehensive overview of SMPFs,including materials,fabrication methods,structures,multifunction,and applications.Firstly,the mechanism and characteristics of SMP are introduced.We then discuss the electrospinning method to form various microstructures,like non-woven fbers,core/shell fbers,hollow fbers and oriented fbers.Afterward,the multiple functions of SMPFs are discussed,such as multi-shape memory efect,reversible shape memory efect and remote actuation of composites.We also focus on some typical applications of SMPFs,including biomedical scafolds,drug carriers,self-healing,smart textiles and sensors,as well as energy harvesting devices.At the end,the challenges and future development directions of SMPFs are proposed.
基金This work was funded by the National Natural Science Foundation of China(No.52103247)the Scientific Research Project of Hunan Provincial Department of Education(No.21B0264)the Natural Science Foundation of Hunan Province(No.2022JJ40877).
文摘Three-dimensional(3D)graphene is a promising active component for various engineering fields,but its performance is limited by the hidebound electrical conductivity levels and hindered electrical transport.Here we present a novel approach based on interlayer engineering,in which graphene oxide(GO)nanosheets are covalently functionalized with varied molecular lengths of diamine molecules.This has led to the creation of an unprecedented class of 3D graphene with highly adjustable electronic properties.Theoretical calculations and experimental results demonstrate that ethylenediamine,with its small diameter acting as a molecular bridge for facilitating electron transport,has the potential to significantly improve the electrical conductivity of 3D graphene.In contrast,butylene diamine,with its larger diameter,has a reverse effect due to the enlarged spacing of the graphene interlayers,resulting in conductive degradation.More importantly,the moderate conductive level of 3D graphene can be achieved by combining the interlayer spacing expansion effect and theπ-electronic donor ability of aromatic amines.The resulting 3D graphene exhibits highly tunable electronic properties,which can be easily adjusted in a wide range of 2.56-6.61 S·cm^(-1)compared to pristine GO foam(4.20 S·cm^(-1)).This opens up new possibilities for its use as an active material in a piezoresistive sensor,as it offers remarkable monitoring abilities.
