A spheroidal Al_3(Zr,Sc) precipitate with a double-shell structure, comprising a Sc-enriched core enveloped by a Zr-enriched inner shell and a Sc-enriched outer shell(～9 nm in thickness), appears in an Al-0.2 Zr-0.1 ...A spheroidal Al_3(Zr,Sc) precipitate with a double-shell structure, comprising a Sc-enriched core enveloped by a Zr-enriched inner shell and a Sc-enriched outer shell(～9 nm in thickness), appears in an Al-0.2 Zr-0.1 Sc alloy cable after thermomechanical treatment. The average diameter of the spheroidal Al_3(Zr,Sc) precipitate is approximately 80 nm. The double-shelled Al_3(Zr,Sc) precipitate presents three different interfaces and is semi-coherent with the Al matrix. Atom probe tomography(APT) analyses further show that the outer shell of Al_3(Zr,Sc) precipitate is Sc element enrichment. The electrical conductivity of Al-0.2 Zr-0.1 Sc alloy cable increases by 6.5 MS/m within the aging time from 0.2 to 100 h at 350 ℃, with double-shelled Al_3(Zr,Sc)precipitate.展开更多
High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode se...High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode severely restrict their further practical application.Here,a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host.A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process,which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres.This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials,high electronic conductivity,and fast lithium-ion diffusive pathways.In addition,additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species,dramatically accelerating their conversion kinetics and re-utilization.The detailed defect-induced interface catalytic reaction mechanism is firstly proposed.As expected,the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g^−1 at 0.2 C and a desirable rate performance(593 mAh·g^−1 at 5.0 C),implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.展开更多
Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structu...Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface morphologies.In this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is reported.By tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni alloys.It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells.It is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity.The asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.展开更多
The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricat...The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.展开更多
Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employ...Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.展开更多
The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is li...The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is limited by the low contact point between the core and shell.Herein,we propose a general strategy of simultaneous construction of sufficient reserved space and multicontinuous active channels by pyrolysis of two carbon substrates.A double-shell structure consisting of Co_(3)O_(4) anchored to hollow carbon sphere and external self-supporting zeolitic imidazolate framework(ZIF)layer was constructed by spray pyrolysis and additional carbon coating in-situ growth.In the process of high-temperature calcination,the carbon and nitrogen layers between the shells separate,creating additional space,while the Co_(3)O_(4) particles between the shells remain are still in close contact to form continuous and fast electron conduction channels,which can realize better charge transfer.Due to the synergy of these design principles,the material has ultra-high initial discharge capacities of 2,183.1 mAh·g^(−1) at 0.2 A·g^(−1) with capacity of 1,121.36 mAh·g^(−1) after 250 cycles,the long-term capacities retention rate is about 92.4%after 700 cycles at 1 A·g^(−1).This unique channel-type double-shell structure fights a way out to prepare novel electrode materials with high performance.展开更多
Cu@MOF core-shell nanowires are synthesized by introducing oxidizable and CTAB-modified metal nanowires as self-engaged templates and supporting MOFs for a one-dimension nanostructure.The following thermal process is ...Cu@MOF core-shell nanowires are synthesized by introducing oxidizable and CTAB-modified metal nanowires as self-engaged templates and supporting MOFs for a one-dimension nanostructure.The following thermal process is controlled to obtain several one-dimension structure s ofCuCo-mixed materials,such as nanorods,single-shell and double-shell nanowires.The hollow structure for electrode materials enlarges the surface area,provides buffer space for electrolyte to accelerate the ion/charge transfers and for the structure to reduce injuries of volume expansion during cycling.Together with some other merits,such as adequate oxidation of the MOFs,small crystal grains of the material,and well-mixed Cu/Co oxides,the double-shell Cu@MOF nanowires(CuCo-DS5)applied for pseudocapacitors deliver advanced electrochemical performance with a specific capacitance of 563.8 F g^(-1)at 1 A g^(-1)as well as an outstanding cycling stability with a 92%retention after 3000 cycles at 5 A g^(-1).Meanwhile,an asymmetric pseudocapacitor constructed with the CuCo-DS5 and active carbon(AC)shows a high specific capacitance and energy density.展开更多
This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-...This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.展开更多
基金Project supported by the 2011 Program of the Ministry of Education in China(043010100)
文摘A spheroidal Al_3(Zr,Sc) precipitate with a double-shell structure, comprising a Sc-enriched core enveloped by a Zr-enriched inner shell and a Sc-enriched outer shell(～9 nm in thickness), appears in an Al-0.2 Zr-0.1 Sc alloy cable after thermomechanical treatment. The average diameter of the spheroidal Al_3(Zr,Sc) precipitate is approximately 80 nm. The double-shelled Al_3(Zr,Sc) precipitate presents three different interfaces and is semi-coherent with the Al matrix. Atom probe tomography(APT) analyses further show that the outer shell of Al_3(Zr,Sc) precipitate is Sc element enrichment. The electrical conductivity of Al-0.2 Zr-0.1 Sc alloy cable increases by 6.5 MS/m within the aging time from 0.2 to 100 h at 350 ℃, with double-shelled Al_3(Zr,Sc)precipitate.
基金The work was financially supported by the National Natural Science Foundation of China(Nos.51672146 and 21805157)the Natural Science Foundation of Shandong Province(No.ZR2018BEM011).
文摘High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode severely restrict their further practical application.Here,a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host.A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process,which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres.This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials,high electronic conductivity,and fast lithium-ion diffusive pathways.In addition,additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species,dramatically accelerating their conversion kinetics and re-utilization.The detailed defect-induced interface catalytic reaction mechanism is firstly proposed.As expected,the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g^−1 at 0.2 C and a desirable rate performance(593 mAh·g^−1 at 5.0 C),implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.
基金the National Key R&D Program of China(No.2016YFB0101201)the National Natural Science Foundation of China(Grant No.21533005).
文摘Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface morphologies.In this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is reported.By tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni alloys.It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells.It is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity.The asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.
基金financially supported by the National Natural Science Foundation of China (Grant No. 22275173)the Open Project of State Key Laboratory of Environment-friendly Energy Materials (Grant No. 22kfhg10)。
文摘The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.
文摘Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.
基金supported by the National Natural Science Foundation of China(Nos.21871005 and 22171005)the Program for Innovative Research Team of Anhui Education Committee,the Project for Collaborative Innovation of Anhui Higher Education Institutes(Nos.GXXT-2020-005,GXXT-2021-012,and GXXT-2021-013)+1 种基金the Natural Science Foundation of the Education Department of Anhui Province(No.KJ2020A0075)the Foundation of the Anhui Province Key Laboratory of Clean Energy Materials and Chemistry for Sustainable Conversion of Natural Resources(No.LCECSC-10).
文摘The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is limited by the low contact point between the core and shell.Herein,we propose a general strategy of simultaneous construction of sufficient reserved space and multicontinuous active channels by pyrolysis of two carbon substrates.A double-shell structure consisting of Co_(3)O_(4) anchored to hollow carbon sphere and external self-supporting zeolitic imidazolate framework(ZIF)layer was constructed by spray pyrolysis and additional carbon coating in-situ growth.In the process of high-temperature calcination,the carbon and nitrogen layers between the shells separate,creating additional space,while the Co_(3)O_(4) particles between the shells remain are still in close contact to form continuous and fast electron conduction channels,which can realize better charge transfer.Due to the synergy of these design principles,the material has ultra-high initial discharge capacities of 2,183.1 mAh·g^(−1) at 0.2 A·g^(−1) with capacity of 1,121.36 mAh·g^(−1) after 250 cycles,the long-term capacities retention rate is about 92.4%after 700 cycles at 1 A·g^(−1).This unique channel-type double-shell structure fights a way out to prepare novel electrode materials with high performance.
基金supported by the National Natural Science Fundsgrant number 51821091,51872233the Shaanxi Natural Science Funds grant number 2018JM5044。
文摘Cu@MOF core-shell nanowires are synthesized by introducing oxidizable and CTAB-modified metal nanowires as self-engaged templates and supporting MOFs for a one-dimension nanostructure.The following thermal process is controlled to obtain several one-dimension structure s ofCuCo-mixed materials,such as nanorods,single-shell and double-shell nanowires.The hollow structure for electrode materials enlarges the surface area,provides buffer space for electrolyte to accelerate the ion/charge transfers and for the structure to reduce injuries of volume expansion during cycling.Together with some other merits,such as adequate oxidation of the MOFs,small crystal grains of the material,and well-mixed Cu/Co oxides,the double-shell Cu@MOF nanowires(CuCo-DS5)applied for pseudocapacitors deliver advanced electrochemical performance with a specific capacitance of 563.8 F g^(-1)at 1 A g^(-1)as well as an outstanding cycling stability with a 92%retention after 3000 cycles at 5 A g^(-1).Meanwhile,an asymmetric pseudocapacitor constructed with the CuCo-DS5 and active carbon(AC)shows a high specific capacitance and energy density.
基金Project supported by the NSAF Joint Fund set up by the National Natural Science Foundation of China and the Chinese Academy of Engineering Physics (CAEP)(Nos. 10676005, 10676004, and10676120)the National Natural Science Foundation of China (No. 10702011)+1 种基金the Natural Science Foundation of CAEP (No. 2007B09001)the Scientific Research Foundation for Returned Overseas Chinese Scholars of Ministry of Education of China
文摘This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.
