It is of significance to investigate deeply the hydrodynamic featu res of the bubble co ntaminated by impurities in view of the fact that the industrial liquid is difficult to keep absolutely pure.On the basis of the ...It is of significance to investigate deeply the hydrodynamic featu res of the bubble co ntaminated by impurities in view of the fact that the industrial liquid is difficult to keep absolutely pure.On the basis of the finite volume method,the bubble interface contaminated by the surfactant(1-pentanol)is achieved through solving the concentration transport equations in liquid and along the bubble interface,and solving the absorption and desorption equation at the bubble interface.And the three-dimensional momentum equation is solved at the same time.It is investigated in detail on the influence of interfacial contamination degrees(described with the cap angleθ)on hydrodynamic characteristics of the spherical bubble when the bubble Reynolds number(Re)is larger than 200.Theθis realized by changing the surfactant concentration(C_(0)) in liquid.The present results show that the hydrodynamic characteristics,such as interfacial concentration,interfacial shear stress,interfacial velocity and wake flow,are related to both Re and C_(0) for the contaminated bubble.When C_(0) is relatively low in liquid(i.e.,the contamination degree of the bubble interface is relatively slight),the hydrodynamic characteristics of the bubble can still keep the 2 D features even if Re>200.The decrease ofθor the increase of Re can promote the appearance of the unsteady wake flow.For the present investigation,when Re>200 andθ≤60°,the hydrodynamic characteristics of the bubble show the 3D phenomena,which indicates that axisymmetric model is no longer valid.展开更多
The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble...The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble size.In this paper,the formation,growth,and detachment of single bubbles in Newtonian liquids based on capillary needles were studied in detail using a volume of fluid method.The authors investigated the effects of gas injection velocity,gravitational level,surface tension coefficient,needle radius,and liquid-phase properties(liquid viscosity and density)on the process of bubble generation,and the effects of the above factors on bubble shape,detachment diameter,and time were analyzed.The results show that an increase in gas injection rate,liquid-phase viscosity,needle radius,and surface tension coefficient can lead to an increase in bubble detachment diameter;however,an increase in liquid-phase density and gravitational level can lead to a decrease in bubble detachment diameter.It is found that the effect of the liquid-phase viscosity on bubble detachment diameter and time is slight,but the effect of gravitational level on detachment diameter and time is significant.Among all the forces,buoyancy,surface tension,and pressure are the most important ones that control the generation of bubbles.展开更多
Dimethylformamide(DMF)and polyvinylpyrrolidone(PVP)were chosen as precursors for the synthesis of a carbon-coated and fully nitrogen-doped Ni_(9)S_(8)/Ni_(3)S_(2)nanocomposite denoted as N-NiS-X,which was successfully...Dimethylformamide(DMF)and polyvinylpyrrolidone(PVP)were chosen as precursors for the synthesis of a carbon-coated and fully nitrogen-doped Ni_(9)S_(8)/Ni_(3)S_(2)nanocomposite denoted as N-NiS-X,which was successfully prepared through a simple oil bath chelation process followed by annealing.The N-NiS-2 electrode revealed optimal electrochemical performance with a sulfur addition of 18.6 mmol.The synthesized composite demonstrated a first-cycle discharge capacity of 1151.3 mAh·g^(-1)at 50 mA·g^(-1),with initial Coulombic efficiency measuring 64.4%.Following 500 cycles of galvanostatic charge–discharge testing at 0.5 A·g^(-1),this prepared electrode maintained 110.1%of its original capacity,which suggested superior kinetic characteristics during electrochemical processes.Electrochemical impedance analysis further demonstrated a reduction in the solution resistance and charge transfer resistance to 5.17 and 32.46Ω,respectively,highlighting enhanced charge transport capabilities.Consequently,the dual roles of in situ nitrogen doping and carbon coating,which effectively suppress the volume expansion effect of Ni_(x)S_(y),are realized by DMF and PVP as nitrogen and carbon sources,respectively.These functionalities markedly improve the structural integrity and electrical conductivity of materials,thereby highlighting their substantial prospects for commercial applications.展开更多
In situ carbon-coated Co_(3)Se_(4)/CoSe_(2)(Co_(x)Se_(y))nanoparticles(NPs)attached on three-dimensional(3D)reduced graphene oxide(rGO)sheets were skillfully developed in this work,which involved the environment-frien...In situ carbon-coated Co_(3)Se_(4)/CoSe_(2)(Co_(x)Se_(y))nanoparticles(NPs)attached on three-dimensional(3D)reduced graphene oxide(rGO)sheets were skillfully developed in this work,which involved the environment-friendly hydrothermal method,freeze drying,and selenide calcination.Within the structure,the glucose-derived carbon layer exhibited significantly homogeneous dispersion under an argon environment.This structure not only has enhanced stability,but also can effectively mitigate the volume swell of Co_(x)Se_(y) particles.The resulted Co_(3)Sea/CoSe_(2)@C/rGO(CSe@C/rGO)exhibited a specific surface area(SSA)of 240.9 m^(2)·g^(-1),offering more electrochemically active sites for the storage of energy related to lithium ions.The rGO matrix held exceptional flexibility and functional structural rigidity,facilitating the swift ion intercalation and ensuring the high conductivity and recyclability of the structure.When applied to anodes designed for lithium-ion batteries(LiBs),this material demonstrated distinguished rate and ultra-high reversible capacity(872.98 mA·h·g^(-1) at 0.5 A·g^(-1)).Meanwhile,its capacity retention reached 119.5%after 500 cycles at 2 A·g^(-1),with a coulombic efficiency of 100%.This work potentially paves the way for generating fast and powerful metal selenide anodes and initiating LiBs with good performance.展开更多
基金financial support from the National Natural Science Foundation of China Fund(51376026)Qinglan Project of Jiangsu province。
文摘It is of significance to investigate deeply the hydrodynamic featu res of the bubble co ntaminated by impurities in view of the fact that the industrial liquid is difficult to keep absolutely pure.On the basis of the finite volume method,the bubble interface contaminated by the surfactant(1-pentanol)is achieved through solving the concentration transport equations in liquid and along the bubble interface,and solving the absorption and desorption equation at the bubble interface.And the three-dimensional momentum equation is solved at the same time.It is investigated in detail on the influence of interfacial contamination degrees(described with the cap angleθ)on hydrodynamic characteristics of the spherical bubble when the bubble Reynolds number(Re)is larger than 200.Theθis realized by changing the surfactant concentration(C_(0)) in liquid.The present results show that the hydrodynamic characteristics,such as interfacial concentration,interfacial shear stress,interfacial velocity and wake flow,are related to both Re and C_(0) for the contaminated bubble.When C_(0) is relatively low in liquid(i.e.,the contamination degree of the bubble interface is relatively slight),the hydrodynamic characteristics of the bubble can still keep the 2 D features even if Re>200.The decrease ofθor the increase of Re can promote the appearance of the unsteady wake flow.For the present investigation,when Re>200 andθ≤60°,the hydrodynamic characteristics of the bubble show the 3D phenomena,which indicates that axisymmetric model is no longer valid.
文摘The interphase mass,heat transfer efficiency,and flow resistance are strongly dependent on bubble size in gas-liquid two-phase systems,so it is very important for engineering applications to effectively control bubble size.In this paper,the formation,growth,and detachment of single bubbles in Newtonian liquids based on capillary needles were studied in detail using a volume of fluid method.The authors investigated the effects of gas injection velocity,gravitational level,surface tension coefficient,needle radius,and liquid-phase properties(liquid viscosity and density)on the process of bubble generation,and the effects of the above factors on bubble shape,detachment diameter,and time were analyzed.The results show that an increase in gas injection rate,liquid-phase viscosity,needle radius,and surface tension coefficient can lead to an increase in bubble detachment diameter;however,an increase in liquid-phase density and gravitational level can lead to a decrease in bubble detachment diameter.It is found that the effect of the liquid-phase viscosity on bubble detachment diameter and time is slight,but the effect of gravitational level on detachment diameter and time is significant.Among all the forces,buoyancy,surface tension,and pressure are the most important ones that control the generation of bubbles.
基金support from Key Research and Development Project of Datong(2023003 and 2024011)Basic Research Project Fund of Shanxi Datong University(2022K10 and 2022K11).
文摘Dimethylformamide(DMF)and polyvinylpyrrolidone(PVP)were chosen as precursors for the synthesis of a carbon-coated and fully nitrogen-doped Ni_(9)S_(8)/Ni_(3)S_(2)nanocomposite denoted as N-NiS-X,which was successfully prepared through a simple oil bath chelation process followed by annealing.The N-NiS-2 electrode revealed optimal electrochemical performance with a sulfur addition of 18.6 mmol.The synthesized composite demonstrated a first-cycle discharge capacity of 1151.3 mAh·g^(-1)at 50 mA·g^(-1),with initial Coulombic efficiency measuring 64.4%.Following 500 cycles of galvanostatic charge–discharge testing at 0.5 A·g^(-1),this prepared electrode maintained 110.1%of its original capacity,which suggested superior kinetic characteristics during electrochemical processes.Electrochemical impedance analysis further demonstrated a reduction in the solution resistance and charge transfer resistance to 5.17 and 32.46Ω,respectively,highlighting enhanced charge transport capabilities.Consequently,the dual roles of in situ nitrogen doping and carbon coating,which effectively suppress the volume expansion effect of Ni_(x)S_(y),are realized by DMF and PVP as nitrogen and carbon sources,respectively.These functionalities markedly improve the structural integrity and electrical conductivity of materials,thereby highlighting their substantial prospects for commercial applications.
基金support from the National Natural Science Foundation of China(52071192)the Basic Research Project Fund of Shanxi Province(20210302124491 and 20210302123341)+5 种基金the Key Research and Development Project of Datong(2023003)the Basic Research Project Fund of Shanxi Datong University(2022K10 and 2022K11)the Graduate Education Reform project of Shanxi Datong University(21JG25)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2021L370)the Graduate Student Education Innovation Project of Shanxi Datong University(23CX25,22CX11,and 22CX20)the Doctoral Research Fund of Shanxi Datong University(2016-B-14,2016-B-20,and 2019-B-11).
文摘In situ carbon-coated Co_(3)Se_(4)/CoSe_(2)(Co_(x)Se_(y))nanoparticles(NPs)attached on three-dimensional(3D)reduced graphene oxide(rGO)sheets were skillfully developed in this work,which involved the environment-friendly hydrothermal method,freeze drying,and selenide calcination.Within the structure,the glucose-derived carbon layer exhibited significantly homogeneous dispersion under an argon environment.This structure not only has enhanced stability,but also can effectively mitigate the volume swell of Co_(x)Se_(y) particles.The resulted Co_(3)Sea/CoSe_(2)@C/rGO(CSe@C/rGO)exhibited a specific surface area(SSA)of 240.9 m^(2)·g^(-1),offering more electrochemically active sites for the storage of energy related to lithium ions.The rGO matrix held exceptional flexibility and functional structural rigidity,facilitating the swift ion intercalation and ensuring the high conductivity and recyclability of the structure.When applied to anodes designed for lithium-ion batteries(LiBs),this material demonstrated distinguished rate and ultra-high reversible capacity(872.98 mA·h·g^(-1) at 0.5 A·g^(-1)).Meanwhile,its capacity retention reached 119.5%after 500 cycles at 2 A·g^(-1),with a coulombic efficiency of 100%.This work potentially paves the way for generating fast and powerful metal selenide anodes and initiating LiBs with good performance.
