Regulating the freedom and distribution of H_(2)O molecules has become the decisive factor in enlarging the electrochemical stability window(ESW)of aqueous electrolytes.Compared with the water in a bulk electrolyte,H_...Regulating the freedom and distribution of H_(2)O molecules has become the decisive factor in enlarging the electrochemical stability window(ESW)of aqueous electrolytes.Compared with the water in a bulk electrolyte,H_(2)O molecules at the electrode-electrolyte interface tend to directly split under bias potential.Therefore,the composition and properties of the interfacial microenvironment are the crux for optimizing ESW.Herein,we developed a heterogel electrolyte with wide ESW(4.88 V)and satisfactory ionic conductivity(4.4 mS/cm)inspired by the bicontinuous architecture and surfactant self-assembly behavior in the ionic liquid microemulsion-based template.This electrolyte was capable of expanding the ESW through the dynamic oil/water/electrode interface ternary structure,which enriched the oil phase and assembled the hydrophobic surfactant tails at the interface to prevent H_(2)O molecules from approaching the electrode surface.Moreover,the surfactant Tween 20 and polymer network effectively suppressed the activity of H_(2)O molecules through H-bond interactions,which was beneficial in expanding the operating voltage range and improving the temperature tolerance.The prepared gel electrolyte demonstrated unparalleled adaptability in various aqueous lithium-based energy storage devices.Notably,the lithium-ion capacitor showed an extended operating voltage of 2.2 V and could provide a high power density of 1350.36 W/kg at an energy density of 6 Wh/kg.It maintained normal power output even in the challenging harsh environment,which enabled 11,000 uninterrupted charge-discharge cycles at 0℃.This work focuses on the regulation of the interfacial microdomain and the restriction of the degree of freedom of H_(2)O molecules to boost the ESW of aqueous electrolytes,providing a promising strategy for the advancement of energy storage technologies.展开更多
The rod-like assembly from BAB block copolymer with hydrophilic middle block A in aqueous solution was described. The copolymer used is polystyrene (PS)39-b-poly(4-vinylpyridine)(P4VP)98-b-PS39 (the subscripts are the...The rod-like assembly from BAB block copolymer with hydrophilic middle block A in aqueous solution was described. The copolymer used is polystyrene (PS)39-b-poly(4-vinylpyridine)(P4VP)98-b-PS39 (the subscripts are the average polymerization degree of corresponding blocks) triblock copolymer with Mw/Mn = 1.15. The aggregates were characterized by transmission electron microscopy and atomic force microscopy. The dependence of rod-like aggregate formation on solvents, pH, and polymer concentrations was investigated. The rod-like aggregates were formed when using dioxane as initial solvent, while spherical micelles were formed using DMF. Elevating pH values from 4 to 5 to 7 and decreasing initial copolymer concentrations from 1.5 wt% to 1.0 wt% to 0.5 wt% were favorable for the formation of well-defined rod-like aggregates. In addition, the bicontinuous rods and lamellae were observed when preparing colloid solutions in appropriate conditions.展开更多
The rich phase behavior of block copolymers(BCPs)has drawn great attention in recent years.However,the double diamond(DD)phase is rarely obtained because of the competition between the minimization of interfacial ener...The rich phase behavior of block copolymers(BCPs)has drawn great attention in recent years.However,the double diamond(DD)phase is rarely obtained because of the competition between the minimization of interfacial energy and packing frustration.Here,a rod-coil BCP containing mesogen-jacketed liquid crystalline polymer is designed to acquire ordered bicontinuous network nanostructures.The reduction of internal energy originating from the orientational interaction among the rod blocks can compensate for the free energy penalty of packing frustration to stabilize the DD structure.The resulting BCP can also experience lamellae-to-DD and double gyroid-to-lamellae transitions by changing the annealing temperature.These results make the rod-coil BCP an excellent candidate for the self-assembly of ordered network structures,demonstrating great potential in nanopatterning and metamaterials.展开更多
This study presents a novel process for the fabrication of metal-intermetallic composites with a 3D bicontinuous structure, achieved through a combination of liquid metal dealloying(LMD) and subsequent alloying. Initi...This study presents a novel process for the fabrication of metal-intermetallic composites with a 3D bicontinuous structure, achieved through a combination of liquid metal dealloying(LMD) and subsequent alloying. Initially, porous Ti structures are produced using the LMD process, followed by immersion in a molten Mg-3Al(wt%) metal. Due to the higher thermodynamic miscibility of Al with Ti compared to Mg, the concentration of Al in the Ti matrix increases as the immersion time increases. This results in a sequential phase transition within the Ti matrix: α-Ti → Ti_(3)Al → Ti Al. The phase transition considerably affects the hardness and strength of the composite material,with the Mg-Ti_(3)Al-Ti Al composite exhibiting a maximum hardness nearly twice as high as that of the conventional Mg-Ti composite. This innovative process holds potential for the development of various bicontinuous metal-intermetallic composites.展开更多
Poly(4-methyl-1-pentene)hollow fiber membranes(PMP HFMs)are commonly used in gas separation membrane and artificial lung membrane in extracorporeal membrane oxygenation(ECMO),and its porous structure and mechanical pr...Poly(4-methyl-1-pentene)hollow fiber membranes(PMP HFMs)are commonly used in gas separation membrane and artificial lung membrane in extracorporeal membrane oxygenation(ECMO),and its porous structure and mechanical properties have a significant impact on the performance of the membrane material.In our work,PMP HFMs were prepared by thermally induced phase separation method.Subsequently,through characterization analysis of powder X-ray diffraction,universal tensile machine,scanning electron microscope and other instruments,the effects of PMP concentration,diluent ratio,quenching temperature,air gap distance and winding speed on the membrane performance were systematically investigated to obtain optimal preparation conditions for PMP HFMs.The results showed that the PMP HFMs prepared under optimal conditions possessed good gas permeability with a nitrogen flux of 10.5 ml·MPa^(-1)·cm^(-2)·min^(-1),a surface dense layer,and a good tensile strength of 9.33 MPa.We believed that this work could provide useful references for the application of PMP membranes in the medical field.展开更多
CONSPECTUS:Nature presents us with numerous complex topological structures,among which ordered bicontinuous structures are widely found in biological systems and exhibit numerous functions,as exemplified by the vibran...CONSPECTUS:Nature presents us with numerous complex topological structures,among which ordered bicontinuous structures are widely found in biological systems and exhibit numerous functions,as exemplified by the vibrant wings of butterflies and the robust skeletons of knobby starfish.In recent decades,significant strides have been made in preparing functional materials with bicontinuous porous structures,e.g.,cubosomes�spherical colloidal particles,which encompass continuous pores and frameworks arranged in a cubic crystal lattice.These cubosomes exhibit many remarkable advantages due to their unique periodic topological structure.(1)The three-dimensional(3D)interconnected pores facilitate the smooth transport of substances throughout the material,resulting in at least a three times higher utilization ratio of internal active sites compared to that of their unconnected pore or nonporous counterparts.Their complex,tortuous,and periodic porous configuration can enhance energy capture,such as solar/electric energy.(2)The 3D continuous pore channels and frameworks provide“highways”for ion and electron transport,leading to an order-of-magnitude reduction in charge-transfer resistance and an over 3-fold increase in the ion diffusion coefficient compared to those of nonporous analogues,thereby improving the electrochemical kinetics of electrodes.(3)Cubosomes have emerged as unique mechanical metamaterials,exhibiting a remarkable capability to alleviate mechanical stress and strain.(4)Their negative-Gaussian-curvature surfaces facilitate the adsorption/desorption of reaction intermediates,thereby lowering the reaction free energy in catalytic reaction processes.Additionally,this distinctive surface structure can enhance the electric field intensity at material interfaces,significantly promoting ion adsorption.With these advantages,functional cubosomes show potential for application in the field of energy storage and conversion.However,due to the big challenges in their preparation,there have been limited studies on their structure−activity relationships in energy-related applications.Therefore,there has not yet been a review regarding functional cubosomes.In this Account,we summarize mainly our latest progress in the study of functional cubosomes.First,we introduce the preparation of polymer cubosomes(PCs)through the self-assembly of block copolymers in solution,along with plotting their morphological phase diagram.Then,the Account describes nanocasting approaches in which polymer cubosomes are employed as templates to prepare a variety of functional cubosomes,including polymers,covalent organic frameworks(COFs),metal−organic frameworks(MOFs),metal−phenolic networks,carbons,inorganic metal compounds,and metals.Finally,to elucidate the application prospects of the functional cubosomes,this Account discusses their advantages in different energy storage and conversion applications,highlighting efficient material and energy utilization,fast mass and electron transport,negative-Gaussian-curvature surfaces,and excellent mechanical stability.We anticipate that this Account will demystify functional cubosomes with bicontinuous porous structures and stimulate their broad interest in the fields of materials science,chemistry,and energy,among others.展开更多
The existence and uniqueness of solutions to the multivalued stochastic differential equations with non-Lipschitz coefficients are proved, and bicontinuous modifications of the solutions are obtained.
SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performa...SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching.Herein,we report ultralight SiC/Si3N4 composite aerogels(~15 mg·cm^(−3))consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons.Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method.The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss(RL,−48.6 dB)and a wide effective absorption band(EAB,7.4 GHz)at a thickness of 2 mm,attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure.In addition,the aerogel exhibits high thermal stability in air until 1000℃and excellent thermal insulation performance(0.030 W·m^(−1)·K^(−1)).These superior performances make the SiC/Si_(3)N_(4) composite aerogel promising to become a new generation of absorption material served under extreme conditions.展开更多
Titania has received considerable attention as a promising anode material of Li-ion battery(LIB).Controlling the structure and morphology of titania nanostructures is crucial to govern their performance.Herein,we repo...Titania has received considerable attention as a promising anode material of Li-ion battery(LIB).Controlling the structure and morphology of titania nanostructures is crucial to govern their performance.Herein,we report a mesoporous titania scaffold with a bicontinuous shifted double diamond(SDD)structure for anode material of LIB.The titania scaffold was synthesized by the cooperative self-assembly of a block copolymer poly(ethylene oxide)-block-polystyrene template and titanium diisopropoxide bis(acetylacetonate)as the inorganic precursor in a mixture solvent of tetrahydrofuran and HCl/water.The structure shows tetragonal symmetry(space group I4_(1)/amd)comprising two sets of diamond networks adjoining each other with the unit cell parameter of a=90 nm and c=127 nm,which affords the porous titania a specific surface area(SSA)of 42 m^(2)·g^(-1)with a mean pore diameter of 38 nm.Serving as an anode material of LIB,the bicontinuous titania scaffold exhibits a high specific capacity of 254 mAh·g^(-1)at the current density of 1 A·g^(-1)and an alluring self-improving feature upon charge/discharge over 1,000 cycles.This study overcomes the difficulty in building up ordered bicontinuous functional materials and demonstrates their potential in energy storage application.展开更多
Main observation and conclusion Polymerization-induced self-assembly(PISA)is an effective method to prepare block copolymer(BCP)particles with various morphologies.However,BCPs with inverse bicontinuous phase structur...Main observation and conclusion Polymerization-induced self-assembly(PISA)is an effective method to prepare block copolymer(BCP)particles with various morphologies.However,BCPs with inverse bicontinuous phase structure have been rarely prepared via PISA.Herein,we report the preparation of particles.展开更多
Structures having nanoscale 3D geometries are valuable as multifunctional materials, where multi-continuous microphases can synergistically influence mechanical, optical, transport and other properties. Such very high...Structures having nanoscale 3D geometries are valuable as multifunctional materials, where multi-continuous microphases can synergistically influence mechanical, optical, transport and other properties. Such very high interface surface to volume ratio structures occur in a variety of materials including natural materials such as butter fly wings and sea urchin exoskeletons and in synthetic self-assembled structures such as surfactant/water systems and block polymers. Quantitative morphological characterization of such complex geometric structures is quite challenging. Unit cell sizes range from 10-300 nm with corresponding feature sizes on the 2-50 nm scale. Since these nanoscale network structures are bicontinuous, when one constituent is removed, the structure is still self supporting. Removal of one component produces a nanoporous material that may be in-filled with another component, or the surfaces of the nanopores can be coated with ultra-thin layers by atomic layer deposition to offer multiftmctional capabilities. Due to the ability to individually tailor the properties of the network（s） and matrix, for example, to create strong dielectric or impedance contrast, such spatially periodic structures are excellent for the interference of waves （electromagnetic for photonic applications and acoustic for phononic applications） that can lead to bandgaps and hence the control of wave propagation in the material. This mini-review will focus on networks formed by bottom up self assembly of block polymers. In addition to structural issues, we emphasize the special physical properties related to bi- or tri-continuous networks.展开更多
Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible...Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible addition-fragmentation chain transfer(RAFT)dispersion alternating copolymerization of styrene and pentafluorostyrene is conducted in 2%v/v toluene/ethanol by simultaneously using poly(N,N-dimethylacrylamide)(PDMA29)as a macromolecular chain transfer agent(macro-CTA)and small molecule CTA.展开更多
In this paper, the phase behavior and interracial properties of symmetric ternary polymeric blends A/B/AB are studied by dissipative particle dynamics （DPD） simulations. By using the structure factor and nematic ord...In this paper, the phase behavior and interracial properties of symmetric ternary polymeric blends A/B/AB are studied by dissipative particle dynamics （DPD） simulations. By using the structure factor and nematic order parameter, we carefully characterized the diversified phases and phase transitions, and established the phase diagram of such symmetric ternary blends. It can be generally divided into four regions： disordered phase （DIS） region at high temperature, ordered lameUar phase （LAM） region, bicontinuous microemulsion （BμE） channel and phase-separated phase （2P） region at low temperature with the increase of the total volume fractions of homopolymers φn, which shows good accordance with that in previous experimental and theoretical reports. Furthermore, we calculated the elastic constants of 2P and LAM phase, and discussed the transition mechanisms from 2P and LAM to BμE phase, respectively. The results show a direct relevance between the phase transitions and the change of interfacial properties. Finally, we also demonstrate that the B,uE channel becomes narrower in lower temperature caused by the temperature dependence of interfacial properties of ternary blends.展开更多
A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D...A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.22032003 and 22072073)。
文摘Regulating the freedom and distribution of H_(2)O molecules has become the decisive factor in enlarging the electrochemical stability window(ESW)of aqueous electrolytes.Compared with the water in a bulk electrolyte,H_(2)O molecules at the electrode-electrolyte interface tend to directly split under bias potential.Therefore,the composition and properties of the interfacial microenvironment are the crux for optimizing ESW.Herein,we developed a heterogel electrolyte with wide ESW(4.88 V)and satisfactory ionic conductivity(4.4 mS/cm)inspired by the bicontinuous architecture and surfactant self-assembly behavior in the ionic liquid microemulsion-based template.This electrolyte was capable of expanding the ESW through the dynamic oil/water/electrode interface ternary structure,which enriched the oil phase and assembled the hydrophobic surfactant tails at the interface to prevent H_(2)O molecules from approaching the electrode surface.Moreover,the surfactant Tween 20 and polymer network effectively suppressed the activity of H_(2)O molecules through H-bond interactions,which was beneficial in expanding the operating voltage range and improving the temperature tolerance.The prepared gel electrolyte demonstrated unparalleled adaptability in various aqueous lithium-based energy storage devices.Notably,the lithium-ion capacitor showed an extended operating voltage of 2.2 V and could provide a high power density of 1350.36 W/kg at an energy density of 6 Wh/kg.It maintained normal power output even in the challenging harsh environment,which enabled 11,000 uninterrupted charge-discharge cycles at 0℃.This work focuses on the regulation of the interfacial microdomain and the restriction of the degree of freedom of H_(2)O molecules to boost the ESW of aqueous electrolytes,providing a promising strategy for the advancement of energy storage technologies.
文摘The rod-like assembly from BAB block copolymer with hydrophilic middle block A in aqueous solution was described. The copolymer used is polystyrene (PS)39-b-poly(4-vinylpyridine)(P4VP)98-b-PS39 (the subscripts are the average polymerization degree of corresponding blocks) triblock copolymer with Mw/Mn = 1.15. The aggregates were characterized by transmission electron microscopy and atomic force microscopy. The dependence of rod-like aggregate formation on solvents, pH, and polymer concentrations was investigated. The rod-like aggregates were formed when using dioxane as initial solvent, while spherical micelles were formed using DMF. Elevating pH values from 4 to 5 to 7 and decreasing initial copolymer concentrations from 1.5 wt% to 1.0 wt% to 0.5 wt% were favorable for the formation of well-defined rod-like aggregates. In addition, the bicontinuous rods and lamellae were observed when preparing colloid solutions in appropriate conditions.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51921002,22203015 and 51725301)Natural Science Foundation of Fujian Province(No.2021J01591)the National Key R&D Program of China(No.2018YFB0703702).The suggestions and help offered by Prof.Rong-Ming Ho of National Tsing Hua University are greatly appreciated.The authors acknowledge the scientists at the synchrotron X-ray beamline 1W2A at Beijing Synchrotron Radiation Facility(BSRF)and the synchrotron X-ray beamline BL16B1 at Shanghai Synchrotron Radiation Facility(SSRF)for their assistance on the SAXS experiments.
文摘The rich phase behavior of block copolymers(BCPs)has drawn great attention in recent years.However,the double diamond(DD)phase is rarely obtained because of the competition between the minimization of interfacial energy and packing frustration.Here,a rod-coil BCP containing mesogen-jacketed liquid crystalline polymer is designed to acquire ordered bicontinuous network nanostructures.The reduction of internal energy originating from the orientational interaction among the rod blocks can compensate for the free energy penalty of packing frustration to stabilize the DD structure.The resulting BCP can also experience lamellae-to-DD and double gyroid-to-lamellae transitions by changing the annealing temperature.These results make the rod-coil BCP an excellent candidate for the self-assembly of ordered network structures,demonstrating great potential in nanopatterning and metamaterials.
基金supported by the National Research Council of Science & Technology (NST) grant by the Korea Government (MSIT) (grant no.CRC23011-000)by the National Research Foundation of Korea (NRF) funded by the Ministry of Science,ICT,and Future Planning (MSIP,South Korea) (grant no.NRF-2021R1C1C1007645)。
文摘This study presents a novel process for the fabrication of metal-intermetallic composites with a 3D bicontinuous structure, achieved through a combination of liquid metal dealloying(LMD) and subsequent alloying. Initially, porous Ti structures are produced using the LMD process, followed by immersion in a molten Mg-3Al(wt%) metal. Due to the higher thermodynamic miscibility of Al with Ti compared to Mg, the concentration of Al in the Ti matrix increases as the immersion time increases. This results in a sequential phase transition within the Ti matrix: α-Ti → Ti_(3)Al → Ti Al. The phase transition considerably affects the hardness and strength of the composite material,with the Mg-Ti_(3)Al-Ti Al composite exhibiting a maximum hardness nearly twice as high as that of the conventional Mg-Ti composite. This innovative process holds potential for the development of various bicontinuous metal-intermetallic composites.
基金support of thiswork by Science Fund of State Key Laboratory of Tribology,Tsinghua University(61012205321).
文摘Poly(4-methyl-1-pentene)hollow fiber membranes(PMP HFMs)are commonly used in gas separation membrane and artificial lung membrane in extracorporeal membrane oxygenation(ECMO),and its porous structure and mechanical properties have a significant impact on the performance of the membrane material.In our work,PMP HFMs were prepared by thermally induced phase separation method.Subsequently,through characterization analysis of powder X-ray diffraction,universal tensile machine,scanning electron microscope and other instruments,the effects of PMP concentration,diluent ratio,quenching temperature,air gap distance and winding speed on the membrane performance were systematically investigated to obtain optimal preparation conditions for PMP HFMs.The results showed that the PMP HFMs prepared under optimal conditions possessed good gas permeability with a nitrogen flux of 10.5 ml·MPa^(-1)·cm^(-2)·min^(-1),a surface dense layer,and a good tensile strength of 9.33 MPa.We believed that this work could provide useful references for the application of PMP membranes in the medical field.
基金supported by the National Natural Science Foundation of China(22225501,W2412102,52421006,22305149,52303275,and 52203268)the Shanghai Municipal Science and Technology Major Project,and SJTU 2030B plan(WH510207202).
文摘CONSPECTUS:Nature presents us with numerous complex topological structures,among which ordered bicontinuous structures are widely found in biological systems and exhibit numerous functions,as exemplified by the vibrant wings of butterflies and the robust skeletons of knobby starfish.In recent decades,significant strides have been made in preparing functional materials with bicontinuous porous structures,e.g.,cubosomes�spherical colloidal particles,which encompass continuous pores and frameworks arranged in a cubic crystal lattice.These cubosomes exhibit many remarkable advantages due to their unique periodic topological structure.(1)The three-dimensional(3D)interconnected pores facilitate the smooth transport of substances throughout the material,resulting in at least a three times higher utilization ratio of internal active sites compared to that of their unconnected pore or nonporous counterparts.Their complex,tortuous,and periodic porous configuration can enhance energy capture,such as solar/electric energy.(2)The 3D continuous pore channels and frameworks provide“highways”for ion and electron transport,leading to an order-of-magnitude reduction in charge-transfer resistance and an over 3-fold increase in the ion diffusion coefficient compared to those of nonporous analogues,thereby improving the electrochemical kinetics of electrodes.(3)Cubosomes have emerged as unique mechanical metamaterials,exhibiting a remarkable capability to alleviate mechanical stress and strain.(4)Their negative-Gaussian-curvature surfaces facilitate the adsorption/desorption of reaction intermediates,thereby lowering the reaction free energy in catalytic reaction processes.Additionally,this distinctive surface structure can enhance the electric field intensity at material interfaces,significantly promoting ion adsorption.With these advantages,functional cubosomes show potential for application in the field of energy storage and conversion.However,due to the big challenges in their preparation,there have been limited studies on their structure−activity relationships in energy-related applications.Therefore,there has not yet been a review regarding functional cubosomes.In this Account,we summarize mainly our latest progress in the study of functional cubosomes.First,we introduce the preparation of polymer cubosomes(PCs)through the self-assembly of block copolymers in solution,along with plotting their morphological phase diagram.Then,the Account describes nanocasting approaches in which polymer cubosomes are employed as templates to prepare a variety of functional cubosomes,including polymers,covalent organic frameworks(COFs),metal−organic frameworks(MOFs),metal−phenolic networks,carbons,inorganic metal compounds,and metals.Finally,to elucidate the application prospects of the functional cubosomes,this Account discusses their advantages in different energy storage and conversion applications,highlighting efficient material and energy utilization,fast mass and electron transport,negative-Gaussian-curvature surfaces,and excellent mechanical stability.We anticipate that this Account will demystify functional cubosomes with bicontinuous porous structures and stimulate their broad interest in the fields of materials science,chemistry,and energy,among others.
基金supported by the National Natural Science Foundation of China (No.10871215).
文摘The existence and uniqueness of solutions to the multivalued stochastic differential equations with non-Lipschitz coefficients are proved, and bicontinuous modifications of the solutions are obtained.
基金support from the National Natural Science Foundation of China (No.52072294)the Characteristic Development Guidance Funds for the Central Universities.
文摘SiC ceramics are attractive electromagnetic(EM)absorption materials for the application in harsh environment because of their low density,good dielectric tunable performance,and chemical stability.However,the performance of current SiC-based materials to absorb EM wave is generally unsatisfactory due to poor impedance matching.Herein,we report ultralight SiC/Si3N4 composite aerogels(~15 mg·cm^(−3))consisting of numerous interweaving SiC nanowires and Si3N4 nanoribbons.Aerogels were prepared via siloxane pyrolysis and chemical vapor reaction through the template method.The optimal aerogel exhibits excellent EM wave absorption properties with a strong reflection loss(RL,−48.6 dB)and a wide effective absorption band(EAB,7.4 GHz)at a thickness of 2 mm,attributed to good impedance matching and multi attenuation mechanisms of waves within the unique network structure.In addition,the aerogel exhibits high thermal stability in air until 1000℃and excellent thermal insulation performance(0.030 W·m^(−1)·K^(−1)).These superior performances make the SiC/Si_(3)N_(4) composite aerogel promising to become a new generation of absorption material served under extreme conditions.
基金The authors appreciate the Instrum ental Analysis Center at Shanghai Jiao Tong University for some analyses.The authors are also grateful for the financial support from the National Natural Science Foundation of China(Nos.21774076,21922304,21873072,52073173)the Program of the Shanghai Committee of Science and Technology(No.17JC1403200)+1 种基金the Program of Shanghai Academic Research Leader(No.19XD1421700)the Program of Shanghai Eastern Scholar and Natural Science Foundation o f Shanghai(No.18ZR1442400).
文摘Titania has received considerable attention as a promising anode material of Li-ion battery(LIB).Controlling the structure and morphology of titania nanostructures is crucial to govern their performance.Herein,we report a mesoporous titania scaffold with a bicontinuous shifted double diamond(SDD)structure for anode material of LIB.The titania scaffold was synthesized by the cooperative self-assembly of a block copolymer poly(ethylene oxide)-block-polystyrene template and titanium diisopropoxide bis(acetylacetonate)as the inorganic precursor in a mixture solvent of tetrahydrofuran and HCl/water.The structure shows tetragonal symmetry(space group I4_(1)/amd)comprising two sets of diamond networks adjoining each other with the unit cell parameter of a=90 nm and c=127 nm,which affords the porous titania a specific surface area(SSA)of 42 m^(2)·g^(-1)with a mean pore diameter of 38 nm.Serving as an anode material of LIB,the bicontinuous titania scaffold exhibits a high specific capacity of 254 mAh·g^(-1)at the current density of 1 A·g^(-1)and an alluring self-improving feature upon charge/discharge over 1,000 cycles.This study overcomes the difficulty in building up ordered bicontinuous functional materials and demonstrates their potential in energy storage application.
基金Financial support from the National Natural Science Founda-ton of China(No.21674059)the Fundamental Research Funds far the Central Universities is thanked.
文摘Main observation and conclusion Polymerization-induced self-assembly(PISA)is an effective method to prepare block copolymer(BCP)particles with various morphologies.However,BCPs with inverse bicontinuous phase structure have been rarely prepared via PISA.Herein,we report the preparation of particles.
基金supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (de-sc0014457)
文摘Structures having nanoscale 3D geometries are valuable as multifunctional materials, where multi-continuous microphases can synergistically influence mechanical, optical, transport and other properties. Such very high interface surface to volume ratio structures occur in a variety of materials including natural materials such as butter fly wings and sea urchin exoskeletons and in synthetic self-assembled structures such as surfactant/water systems and block polymers. Quantitative morphological characterization of such complex geometric structures is quite challenging. Unit cell sizes range from 10-300 nm with corresponding feature sizes on the 2-50 nm scale. Since these nanoscale network structures are bicontinuous, when one constituent is removed, the structure is still self supporting. Removal of one component produces a nanoporous material that may be in-filled with another component, or the surfaces of the nanopores can be coated with ultra-thin layers by atomic layer deposition to offer multiftmctional capabilities. Due to the ability to individually tailor the properties of the network（s） and matrix, for example, to create strong dielectric or impedance contrast, such spatially periodic structures are excellent for the interference of waves （electromagnetic for photonic applications and acoustic for phononic applications） that can lead to bandgaps and hence the control of wave propagation in the material. This mini-review will focus on networks formed by bottom up self assembly of block polymers. In addition to structural issues, we emphasize the special physical properties related to bi- or tri-continuous networks.
基金support by the National Natural Science Foundation of China(nos.51733003 and 21674059)the Fundamental Research Funds for the Central Universities are thanked.
文摘Polymerization-induced cooperative assembly(PICA)is reported to efficiently access inverse bicontinuous mesophases within particles consisting of amphiphilic block copolymers(BCPs)and solvophobic copolymers.Reversible addition-fragmentation chain transfer(RAFT)dispersion alternating copolymerization of styrene and pentafluorostyrene is conducted in 2%v/v toluene/ethanol by simultaneously using poly(N,N-dimethylacrylamide)(PDMA29)as a macromolecular chain transfer agent(macro-CTA)and small molecule CTA.
基金supported by the National Natural Science Foundation of China(21174154,20874110,50930002)
文摘In this paper, the phase behavior and interracial properties of symmetric ternary polymeric blends A/B/AB are studied by dissipative particle dynamics （DPD） simulations. By using the structure factor and nematic order parameter, we carefully characterized the diversified phases and phase transitions, and established the phase diagram of such symmetric ternary blends. It can be generally divided into four regions： disordered phase （DIS） region at high temperature, ordered lameUar phase （LAM） region, bicontinuous microemulsion （BμE） channel and phase-separated phase （2P） region at low temperature with the increase of the total volume fractions of homopolymers φn, which shows good accordance with that in previous experimental and theoretical reports. Furthermore, we calculated the elastic constants of 2P and LAM phase, and discussed the transition mechanisms from 2P and LAM to BμE phase, respectively. The results show a direct relevance between the phase transitions and the change of interfacial properties. Finally, we also demonstrate that the B,uE channel becomes narrower in lower temperature caused by the temperature dependence of interfacial properties of ternary blends.
文摘A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.
