The significance of graphene and its two-dimensional(2D)analogous inorganic layered materials especially as hexagonal boron nitride(h-BN)and molybdenum disulphide(MoS2)for“clean energy”applications became apparent o...The significance of graphene and its two-dimensional(2D)analogous inorganic layered materials especially as hexagonal boron nitride(h-BN)and molybdenum disulphide(MoS2)for“clean energy”applications became apparent over the last few years due to their extraordinary properties.In this review article we study the current progress and selected challenges in the syntheses of graphene,h-BN and MoS2 including energy storage applications as supercapacitors and batteries.Various substrates/catalysts(metals/insulator/semiconducting)have been used to obtain graphene,h-BN and MoS2 using different kinds of precursors.The most widespread methods for synthesis of graphene,h-BN and MoS2 layers are chemical vapor deposition(CVD),plasma-enhanced CVD,hydro/solvothermal methods,liquid phase exfoliation,physical methods etc.Current research has shown that graphene,h-BN and MoS2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries.This review article also contains the discussion on the opportunities and perspectives of these materials(graphene,h-BN and MoS2)in the energy storage fields.We expect that this witen review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene,h-BN and MoS2 layers based materials.展开更多
Sodium-ion batteries(SIBs)have attracted much scientific interest for use in large-scale energy storage systems because sodium is cheaper than lithium.However,the large radius of Na^(+)and barriers to Na^(+)transport ...Sodium-ion batteries(SIBs)have attracted much scientific interest for use in large-scale energy storage systems because sodium is cheaper than lithium.However,the large radius of Na^(+)and barriers to Na^(+)transport result in sluggish kinetics and complicated structural distortion,leading to unsatisfactory rate capability and poor cycling stability.It therefore is essential to develop an electrode with enhanced kinetics and a stable structure during cycling to improve SIB performance.Among the various layered oxide cathodes,those with a spinel-like structure could play an important role in boosting electron transport because of their excellent intrinsic conductivity,including by coordinating with Na^(+)insertion/extraction.Moreover,thanks to the inherent high stability of the spinel-like phase,it could function as a stabilizer for host cathode structures.This review summarizes recent advances in spinel engineering on layered oxide cathodes to boost Na^(+)transport kinetics and provide structural stability to achieve high-performance SIBs,focusing particularly on post-spinel structures,layered oxide integrated spinel-like structures,and spinel transitions.The insights proposed in this review will be useful for guiding rational structural engineering and design to drive the development of new materials and chemistries in Na-based electrode materials.展开更多
This work was aimed to study the interfacial microstructures and three-point bending properties of Al/Cu/Al bimetallic laminates produced by the asymmetrical roll bonding and annealing. It is found that the microstruc...This work was aimed to study the interfacial microstructures and three-point bending properties of Al/Cu/Al bimetallic laminates produced by the asymmetrical roll bonding and annealing. It is found that the microstructure and bonding strength of the Al/Cu interface are different with those of the Cu/Al interface. The interfacial microstructure of Cu/Al interface is improved due to the large interfacial plastic deformation caused by the different rotation speeds of roll in the asymmetrical roll bonding process. The bonding strength between Al and Cu layer can be enhanced by the moderate atomic diffusion, but is dramatically depressed by the formation of intermetallic compounds in the interface.The bending strength of bimetallic laminates is enhanced when the Cu/Al interface is loaded in tension because of the improvement of stress transition and damping by the Cu/Al interface during the three-point bending deformation. The bending fracture reveals that the interfacial cracks can be inhibited from the restricted stress concentration in the improved Cu/Al interface.展开更多
The structural flexibility of hybrid perovskite materials allows for phase transition and consequently thermochromic properties.Here we investigate the thermochromic performance in a series of copper-based layered per...The structural flexibility of hybrid perovskite materials allows for phase transition and consequently thermochromic properties.Here we investigate the thermochromic performance in a series of copper-based layered perovskites with organic cations having different alky chain lengths. Their transition temperature is found to be dependent on the organic cations due to molecular motion and hydrogen bond interaction, providing possibilities to prepare thermochromic semiconductors near room temperature for smart window applications.展开更多
Modifying electrocatalysts nanostructures and tuning their electronic properties through defects-oriented synthetic strategies are:essential to improve the oxygen evolution reaction(OER)performance of electrocatalysts...Modifying electrocatalysts nanostructures and tuning their electronic properties through defects-oriented synthetic strategies are:essential to improve the oxygen evolution reaction(OER)performance of electrocatalysts.Current synthetic strategies about.electrocatalysts mainly target the single or double structural defects,while the researches about the synergistic effect of multiple'structural defects are rare.In this work,the ultrathin NiFe layered double hydroxide nanosheets with a holey structure,oxygen;vacancies and Ni^(3+)defects on nickel foam(NiFe-LDH-NSs/NF)are prepared by employing a simple and green H202-assisted etching 1 method.The synergistic effect ofthe above three defects leads to the exposure of.more active sites and significant improvement of:the intrinsic activity.The optimized catalyst exhibits an excellent OER performance with an extraordinarily low overpotential of 170 mV;at to mA·cm^(-2) and a small Tafel slope of 39.3 mV·dec^(-1) in 1 M KOH solution.Density functional theory calculations reveal this OER;performance arises from pseudo re-oxidized metal-stable Ni^(3+)near oxygen vacancies(O_(vac)),which suppresses 3d-e_(g) of Ni-site and!elevates d-band center towards the competitively low electron-transferbarrier.This work provides a new insight to fabricate advanced electrocatalysts for renewable energy conversion technologies.展开更多
Numerous scenarios of direct contact between electronic components and skin appear in wearable electronic devices. As the “second skin” that lies next to the biological skin of the human body, flexible wearable devi...Numerous scenarios of direct contact between electronic components and skin appear in wearable electronic devices. As the “second skin” that lies next to the biological skin of the human body, flexible wearable devices need to be equipped with thermal protection. However, the use of flexible phase change materials(PCMs) for wearable devices remains a challenge due to their low thermal conductivity, weakened mechanical strength, and liquid leakage. Herein, we developed a multilayered polyimide(PI) composite film integrating stable latent heat absorption, high thermal conductivity, and enhanced mechanical strength. This single piece of material achieved more prominent hotspot protection than traditional foams. The in-plane thermal conductivity of the resultant substrate layer is up to 2.655 W/(m K), which provides a fast response and in-plane dissipation for heat flow. The deliberately arranged interlayer of the material significantly improved the tensile strength(37.6 MPa) of the composite film,representing 128.9% greater strength than that of a bilayer film without a dense layer. The top layer with abundant pores provides reversibly latent heat storing and releasing function after being well infiltrated with paraffin wax. The resulting synergistic effect between three functional layers shows superb heat-suppressing performance in the thickness direction in both thermal shockresistant tests and simulation results. Impressively, the maximum temperature drop reached 40.2℃ compared with the pure PI film. The heating time was delayed by 12 s, providing sufficient warning time for human emergency response. This strategy can potentially pave the way for the design and fabrication of multifunctional films for wearable electronics in thermal protection applications.展开更多
Layered double hydroxides(LDHs)are a class of two-dimensional(2D)clay compounds that consist of positively charged host layers and exchangeable interlayer anions.The stability of their assemblies in aqueous environmen...Layered double hydroxides(LDHs)are a class of two-dimensional(2D)clay compounds that consist of positively charged host layers and exchangeable interlayer anions.The stability of their assemblies in aqueous environment is a challenge due to the extremely high hydrophilicity,which limits their use in membrane-based technologies.Here,we propose a graphene oxide(GO)armour protection strategy to substantially improve the stability of LDH membranes in aqueous solution.The sandwich structured GO/LDH/GO membranes(GLGMs)possess a negative-positive-negative charge heterojunction in the vertical direction that effectively blocks the transport of both cations and anions,i.e.,NaCl,but allows the permeation of water molecules.Following this mechanism,the GLGMs are used for desalination in a forward osmosis mode.A high rejection rate of over 95.2% for NaCl and water flux of over 2.1 Lm^(-2)h^(-1) are achieved with simulated seawater.展开更多
Hierarchical layered structures,whether in a compact form like nacre or a porous manner like bone,are well known for their combined features of high stiffness,strength,and lightweight,inspiring many man-made materials...Hierarchical layered structures,whether in a compact form like nacre or a porous manner like bone,are well known for their combined features of high stiffness,strength,and lightweight,inspiring many man-made materials and structures for high performance applications.The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers,although the fabrication and processing remain a great challenge.In this work,a bio-inspired lightweight nano-cellular epoxy/graphene-Fe_(3)O_(4) nanocomposite with high nanofiller loading of 75 wt.%was successfully fabricated by combining features from both nacre and bone structures,via a simple compression molding process together with an eco-friendly supercritical CO_(2) foaming process to achieve robust mechanical strength and excellent electromagnetic interference(EMI)shielding effectiveness(SE)simultaneously.Highly aligned graphene-Fe_(3)O_(4) nanoplatelets with well controlled nanoscale porous structures(52.6 nm)enabled both low density(1.26 g/cm^(3))and high specific EMI SE>5200 dB/cm^(2)/g,as well as preserved tensile strength of 67 MPa.This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications,from portable electronics to healthcare devices.展开更多
The effect of silicon on synthesis of Ti3AlC2 by spark plasma sintering （SPS） from TiC/Ti/Al powders was investigated. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used for phase identific...The effect of silicon on synthesis of Ti3AlC2 by spark plasma sintering （SPS） from TiC/Ti/Al powders was investigated. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used for phase identification and microstructure evaluation. The results show that addition of silicon can considerably accelerate the synthesis reaction of Ti3AlC2 and fully dense, essentially single-phase （purity 〉98%） polycrystalline Ti3AlC2 could be successfully obtained by sintering 2TiC/lTi/lAl/0.2Si powders at 1 200- 1 250 ℃ under a pressure of 30 MPa. SEM photographs show that the obtained Ti3AlC2 samples from mixtures powders are in plane-shape with a size of about 2-5 μm and 10-25 μm in the thickness dimension and elongated dimension, respectively.展开更多
Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM ind...Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM indicated well-dispersed NMMT platelets in the films prepared. The ideal dispersity achieved was thought to be the result of aqueous compatibility between CEAR molecules and NMMT platelets and the result of the water-involved process as well. The modulus and strength of the polymer/clay nanocomposite coatings tested by tensile testing and nano-indentation were effectively improved compared to those of the virgin CEAR film. In addition,the adhesion strength,flexibility and water-resistance represented by Chinese national standard (GB) kept the best grades.展开更多
Thermoelectric(TE)performance of Ca_(3)Co_(4)O_(9)(CCO)has been investigated extensively via a doping strategy in the past decades.However,the doping sites of different sublayers in CCO and their contributions to the ...Thermoelectric(TE)performance of Ca_(3)Co_(4)O_(9)(CCO)has been investigated extensively via a doping strategy in the past decades.However,the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system.In this work,Sr and Ti are chosen to realize doping at the[Ca_(2)CoO_(3)]and[CoO_(2)]sublayers in CCO.It was found that figure of merit(ZT)at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO.The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co^(4+) originating from the Sr doping effects in[Ca_(2)CoO_(3)]sublayer,which are evidenced by the scanning electron microscope(SEM),Raman,Hall,and X-ray photoelectron spectroscopy(XPS)analysis.Furthermore,the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in[Ca_(2)CoO_(3)]sublayer.Our findings demonstrate that doping at Ca sites of[Ca_(2)CoO_(3)]layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient,and reducing the thermal conductivity simultaneously.This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.展开更多
基金R.K.acknowledges Japan Society for the Promotion of Science(JSPSStandard)for international postdoctoral fellowship(P18063)and this research work was supported by JSPS KAKENHI Grant No.18F18063.A.M.acknowledges the financial support from JSPS KAKENHI Grant JP-18H03841 and JSPS KAKENHI Grant JP-17K18985.R.K.and A.M.would like to thanks Toyohashi University of Technology,Toyohashi,Aichi,Japan for providing the necessarily support and facilities to complete this work.S.S.acknowledges DST-SERB,India for the national postdoctoral fellowship(NPDF File No.PDF/2017/000328).D.P.S.acknowledges with gratitude the financial support from Millennium Institute for Research in Optics(MIRO),CHILE.R.K.would like to dedicate this work to the memory of late Prof.Yoshiyuki Suda.
文摘The significance of graphene and its two-dimensional(2D)analogous inorganic layered materials especially as hexagonal boron nitride(h-BN)and molybdenum disulphide(MoS2)for“clean energy”applications became apparent over the last few years due to their extraordinary properties.In this review article we study the current progress and selected challenges in the syntheses of graphene,h-BN and MoS2 including energy storage applications as supercapacitors and batteries.Various substrates/catalysts(metals/insulator/semiconducting)have been used to obtain graphene,h-BN and MoS2 using different kinds of precursors.The most widespread methods for synthesis of graphene,h-BN and MoS2 layers are chemical vapor deposition(CVD),plasma-enhanced CVD,hydro/solvothermal methods,liquid phase exfoliation,physical methods etc.Current research has shown that graphene,h-BN and MoS2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries.This review article also contains the discussion on the opportunities and perspectives of these materials(graphene,h-BN and MoS2)in the energy storage fields.We expect that this witen review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene,h-BN and MoS2 layers based materials.
基金Y.-F.Z.and Y.X.contributed equally to this work.This work was supported by the National Natural Science Foundation of China(No.51971124)Australian Renewable Energy Agency(ARENA S4)project(grant no.G00849)+2 种基金Yan-Fang Zhu is supported by the China Scholarship Council(201706240170)Y.Xiao acknowledges the National Postdoctoral Program for Innovative Talents(BX20200222)the China Postdoctoral Science Foundation(Grant No.2020M682878).
文摘Sodium-ion batteries(SIBs)have attracted much scientific interest for use in large-scale energy storage systems because sodium is cheaper than lithium.However,the large radius of Na^(+)and barriers to Na^(+)transport result in sluggish kinetics and complicated structural distortion,leading to unsatisfactory rate capability and poor cycling stability.It therefore is essential to develop an electrode with enhanced kinetics and a stable structure during cycling to improve SIB performance.Among the various layered oxide cathodes,those with a spinel-like structure could play an important role in boosting electron transport because of their excellent intrinsic conductivity,including by coordinating with Na^(+)insertion/extraction.Moreover,thanks to the inherent high stability of the spinel-like phase,it could function as a stabilizer for host cathode structures.This review summarizes recent advances in spinel engineering on layered oxide cathodes to boost Na^(+)transport kinetics and provide structural stability to achieve high-performance SIBs,focusing particularly on post-spinel structures,layered oxide integrated spinel-like structures,and spinel transitions.The insights proposed in this review will be useful for guiding rational structural engineering and design to drive the development of new materials and chemistries in Na-based electrode materials.
基金financially supported by the National Natural Science Foundation of China (Nos. 50971038 and 51174058)
文摘This work was aimed to study the interfacial microstructures and three-point bending properties of Al/Cu/Al bimetallic laminates produced by the asymmetrical roll bonding and annealing. It is found that the microstructure and bonding strength of the Al/Cu interface are different with those of the Cu/Al interface. The interfacial microstructure of Cu/Al interface is improved due to the large interfacial plastic deformation caused by the different rotation speeds of roll in the asymmetrical roll bonding process. The bonding strength between Al and Cu layer can be enhanced by the moderate atomic diffusion, but is dramatically depressed by the formation of intermetallic compounds in the interface.The bending strength of bimetallic laminates is enhanced when the Cu/Al interface is loaded in tension because of the improvement of stress transition and damping by the Cu/Al interface during the three-point bending deformation. The bending fracture reveals that the interfacial cracks can be inhibited from the restricted stress concentration in the improved Cu/Al interface.
基金supported by the Ministry of Science and Technology of China (2017YFA0204502)the National Natural Science Foundation of China (21873105)
文摘The structural flexibility of hybrid perovskite materials allows for phase transition and consequently thermochromic properties.Here we investigate the thermochromic performance in a series of copper-based layered perovskites with organic cations having different alky chain lengths. Their transition temperature is found to be dependent on the organic cations due to molecular motion and hydrogen bond interaction, providing possibilities to prepare thermochromic semiconductors near room temperature for smart window applications.
基金supports from the National Natural Science Foundation of China(Nos.21531006 and 21773163)the State Key Laboratory of Organometallic Chemistry of Shanghai Institute of Organic Chemistry(No.KF2021005)Collaborative Innovation Center of Suzhou Nano Science and Technology,the“Priority Academic Program Development”of Jiangsu Higher Education Institutions,and the Project of Scientific and Technologic Infrastructure of Suzhou(No.SZS201905).
文摘Modifying electrocatalysts nanostructures and tuning their electronic properties through defects-oriented synthetic strategies are:essential to improve the oxygen evolution reaction(OER)performance of electrocatalysts.Current synthetic strategies about.electrocatalysts mainly target the single or double structural defects,while the researches about the synergistic effect of multiple'structural defects are rare.In this work,the ultrathin NiFe layered double hydroxide nanosheets with a holey structure,oxygen;vacancies and Ni^(3+)defects on nickel foam(NiFe-LDH-NSs/NF)are prepared by employing a simple and green H202-assisted etching 1 method.The synergistic effect ofthe above three defects leads to the exposure of.more active sites and significant improvement of:the intrinsic activity.The optimized catalyst exhibits an excellent OER performance with an extraordinarily low overpotential of 170 mV;at to mA·cm^(-2) and a small Tafel slope of 39.3 mV·dec^(-1) in 1 M KOH solution.Density functional theory calculations reveal this OER;performance arises from pseudo re-oxidized metal-stable Ni^(3+)near oxygen vacancies(O_(vac)),which suppresses 3d-e_(g) of Ni-site and!elevates d-band center towards the competitively low electron-transferbarrier.This work provides a new insight to fabricate advanced electrocatalysts for renewable energy conversion technologies.
基金supported by the National Natural Science Foundation of China(Grant No.U21A2094)the CASHIPS Director's Fund(Grant No.YZJJZX202015)。
文摘Numerous scenarios of direct contact between electronic components and skin appear in wearable electronic devices. As the “second skin” that lies next to the biological skin of the human body, flexible wearable devices need to be equipped with thermal protection. However, the use of flexible phase change materials(PCMs) for wearable devices remains a challenge due to their low thermal conductivity, weakened mechanical strength, and liquid leakage. Herein, we developed a multilayered polyimide(PI) composite film integrating stable latent heat absorption, high thermal conductivity, and enhanced mechanical strength. This single piece of material achieved more prominent hotspot protection than traditional foams. The in-plane thermal conductivity of the resultant substrate layer is up to 2.655 W/(m K), which provides a fast response and in-plane dissipation for heat flow. The deliberately arranged interlayer of the material significantly improved the tensile strength(37.6 MPa) of the composite film,representing 128.9% greater strength than that of a bilayer film without a dense layer. The top layer with abundant pores provides reversibly latent heat storing and releasing function after being well infiltrated with paraffin wax. The resulting synergistic effect between three functional layers shows superb heat-suppressing performance in the thickness direction in both thermal shockresistant tests and simulation results. Impressively, the maximum temperature drop reached 40.2℃ compared with the pure PI film. The heating time was delayed by 12 s, providing sufficient warning time for human emergency response. This strategy can potentially pave the way for the design and fabrication of multifunctional films for wearable electronics in thermal protection applications.
基金financially supported by the National Natural Science Foundation of China(21975268)China Postdoctoral Science Foundation(2019M660413)。
文摘Layered double hydroxides(LDHs)are a class of two-dimensional(2D)clay compounds that consist of positively charged host layers and exchangeable interlayer anions.The stability of their assemblies in aqueous environment is a challenge due to the extremely high hydrophilicity,which limits their use in membrane-based technologies.Here,we propose a graphene oxide(GO)armour protection strategy to substantially improve the stability of LDH membranes in aqueous solution.The sandwich structured GO/LDH/GO membranes(GLGMs)possess a negative-positive-negative charge heterojunction in the vertical direction that effectively blocks the transport of both cations and anions,i.e.,NaCl,but allows the permeation of water molecules.Following this mechanism,the GLGMs are used for desalination in a forward osmosis mode.A high rejection rate of over 95.2% for NaCl and water flux of over 2.1 Lm^(-2)h^(-1) are achieved with simulated seawater.
基金the National Natural Science Foundation of China(Grant No.51773170)the Shaanxi Coal Joint Fund(Grant 2019JLM-24)+3 种基金funded by the International Science&Technology Cooperation Plan of Shaanxi Province(2021KW-52)Fund of Natural Science Foundation of Shaanxi Provincial(2021JQ-111)Fund of Basic and Applied Fundamental Research of Guangdong Provincial(2020A1515110861)sponsored by Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(No.CX202051)。
文摘Hierarchical layered structures,whether in a compact form like nacre or a porous manner like bone,are well known for their combined features of high stiffness,strength,and lightweight,inspiring many man-made materials and structures for high performance applications.The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers,although the fabrication and processing remain a great challenge.In this work,a bio-inspired lightweight nano-cellular epoxy/graphene-Fe_(3)O_(4) nanocomposite with high nanofiller loading of 75 wt.%was successfully fabricated by combining features from both nacre and bone structures,via a simple compression molding process together with an eco-friendly supercritical CO_(2) foaming process to achieve robust mechanical strength and excellent electromagnetic interference(EMI)shielding effectiveness(SE)simultaneously.Highly aligned graphene-Fe_(3)O_(4) nanoplatelets with well controlled nanoscale porous structures(52.6 nm)enabled both low density(1.26 g/cm^(3))and high specific EMI SE>5200 dB/cm^(2)/g,as well as preserved tensile strength of 67 MPa.This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications,from portable electronics to healthcare devices.
基金the National Natural Science Foundation of China(No.50572080)
文摘The effect of silicon on synthesis of Ti3AlC2 by spark plasma sintering （SPS） from TiC/Ti/Al powders was investigated. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used for phase identification and microstructure evaluation. The results show that addition of silicon can considerably accelerate the synthesis reaction of Ti3AlC2 and fully dense, essentially single-phase （purity 〉98%） polycrystalline Ti3AlC2 could be successfully obtained by sintering 2TiC/lTi/lAl/0.2Si powders at 1 200- 1 250 ℃ under a pressure of 30 MPa. SEM photographs show that the obtained Ti3AlC2 samples from mixtures powders are in plane-shape with a size of about 2-5 μm and 10-25 μm in the thickness dimension and elongated dimension, respectively.
基金Supported by the National Natural Science Foundation of China (Grant No. 50572044)the 973 Project (Grant No. 2006CB605207-2)
文摘Polymer/clay nanocomposite films were prepared by means of electrodeposition of aqueous suspension including cathodic electrophoretic acrylic resin (CEAR) and Na+-montmorillonite (NMMT). Studies of XRD,SEM and TEM indicated well-dispersed NMMT platelets in the films prepared. The ideal dispersity achieved was thought to be the result of aqueous compatibility between CEAR molecules and NMMT platelets and the result of the water-involved process as well. The modulus and strength of the polymer/clay nanocomposite coatings tested by tensile testing and nano-indentation were effectively improved compared to those of the virgin CEAR film. In addition,the adhesion strength,flexibility and water-resistance represented by Chinese national standard (GB) kept the best grades.
基金financially supported by the National Natural Science Foundation of China(Grant No.51802181)the Natural Science Foundation of Shaanxi Province(Grant No.2019JQ-771)the Foundation of Shaanxi University of Science&Technology(Grant No.2017GBJ-03).
文摘Thermoelectric(TE)performance of Ca_(3)Co_(4)O_(9)(CCO)has been investigated extensively via a doping strategy in the past decades.However,the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system.In this work,Sr and Ti are chosen to realize doping at the[Ca_(2)CoO_(3)]and[CoO_(2)]sublayers in CCO.It was found that figure of merit(ZT)at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO.The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co^(4+) originating from the Sr doping effects in[Ca_(2)CoO_(3)]sublayer,which are evidenced by the scanning electron microscope(SEM),Raman,Hall,and X-ray photoelectron spectroscopy(XPS)analysis.Furthermore,the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in[Ca_(2)CoO_(3)]sublayer.Our findings demonstrate that doping at Ca sites of[Ca_(2)CoO_(3)]layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient,and reducing the thermal conductivity simultaneously.This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.
