Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temp...Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473K for 30rain. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy （XTEM） analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases. The growth of He bubbles after high temperature annealingabides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914＋0.236eV.展开更多
It is anticipated that alkaline water electrolysis(AWE)technology will assume a significant role in the future energy sector,facilitating the integration of renewable energy and hydrogen production.Regrettably,the eff...It is anticipated that alkaline water electrolysis(AWE)technology will assume a significant role in the future energy sector,facilitating the integration of renewable energy and hydrogen production.Regrettably,the effi-ciency of AWE is not yet optimal.In particular,the inefficiency caused by bubbles at increased current density is often overlooked,necessitating a detailed understanding of the intricate relationship between bubble evolution and electrolytic reactions.This paper presents a comprehensive review of the fundamental theory and recent research on bubbles,and outlines the primary challenges and research directions for bubble dynamics in AWE.First,the theory of bubble nucleation,growth,and detachment is reviewed and summarized.Subsequently,the impact of bubbles on the diverse processes occurring during the electrolysis reaction is meticulously delineated and examined.The following section presents a thorough compilation and categorization of the methods employed to remove bubbles,with a detailed analysis of the strategies deployed to mitigate the impact of gas bubble traffic.Additionally,an in-depth exploration of the research methodology employed at each stage of the bubble evolution process is provided.Finally,the review concludes with a summary and outlook on the oppor-tunities and challenges associated with studying bubble dynamics in AWE,offering insights into innovative av-enues for efficient electrolytic hydrogen production.展开更多
We report helium ion irradiation experiments for a new type of dispersion-strengthened NiMo-Y_(2)O_(3)alloy with three different irradiation doses and varying irradiation dose rates at 750℃to evaluate its helium-indu...We report helium ion irradiation experiments for a new type of dispersion-strengthened NiMo-Y_(2)O_(3)alloy with three different irradiation doses and varying irradiation dose rates at 750℃to evaluate its helium-induced damage behavior.Transmission electron microscopy was used to reveal the evolution of helium bubbles after irradiation.The experimental results show that with increasing ion dose,the number density of helium bubbles increases continuously.However,the mean size of helium bubbles first increases and then decreases,mainly due to the varied ion dose rates.The volume fractions of helium bubbles in the three investigated samples after irradiation are 0.15%,0.32%,and 0.27%,which are lower than that of the Hastelloy N alloy(0.58%)after similar irradiation conditions.This indicates that the NiMo-Y_(2)O_(3)alloy exhibits better helium-induced-swelling resistance than the Hastelloy N alloy,highlighting its potential applicability to MSRs,from the perspective of irradiation performance.展开更多
Two-phase flow with complex phase interfaces is commonly observed in both nature and industrial processes.The bubble size distribution(BSD) is a crucial parameter in gas-liquid two-phase flow,impacting various flow ch...Two-phase flow with complex phase interfaces is commonly observed in both nature and industrial processes.The bubble size distribution(BSD) is a crucial parameter in gas-liquid two-phase flow,impacting various flow characteristics including interfacial forces,void fraction distribution,and interfacial area transport.Throughout the flow progression,the BSD changes along the channel due to variations in pressure and interactions among bubbles.Accurately predicting the evolution of BSD can enhance the modeling of two-phase flow.This study presents a novel BSD evolution(BSDE) model,where the governing equation for the probability density function is formulated by considering the conservation of bubbles within a onedimensional control volume in the channel.The downstream BSD is predicted based on the upstream BSD and the effects of pressure variations and bubble interactions along the channel.To account for the multiscale nature of the two-phase flow,the bubbles are categorized into small groups(G_(1)) and large groups(G_(2)).Six distinct source term distributions for intra/inter bubble interactions have been developed.Each source term accounts for the distributions of consumed and generated bubbles,ensuring the conservation of bubble volume through constraints on model coefficients.The model has been tested on a tight-lattice rod bundle using experimental data,with deviations of less than 5% and 15% for G_(1)and G_(2) flow,respectively.Since the model development is independent of specific geometry,the framework of the BSDE model can also be effectively applied to channels of varying shapes.展开更多
Understanding bubbles evolution kinetics on electrodes with varied geometries is of fundamental importance for advanced electrodes design in gas evolution reaction.In this work,the evolution kinetics of electro-genera...Understanding bubbles evolution kinetics on electrodes with varied geometries is of fundamental importance for advanced electrodes design in gas evolution reaction.In this work,the evolution kinetics of electro-generated hydrogen bubbles are recorded in situ on three(i.e.smooth,nanoporous,and nanoarray)Pt electrodes to identify the geometry dependence.The bubble radius shows a time-dependent growth kinetic,which is tightly-connected to the electrode geometry.Among the three electrodes,the smooth one shows a typical time coefficient of 0.5,in consistence with reported values;the nanoporous one shows a time coefficient of 0.47,less than the classic one(0.5);while the nanoarray one exhibits fastest bubble growth kinetics with a time coefficient higher than 0.5(0.54).Moreover,the nanoarray electrode has the smallest bubble detachment size and the largest growth coefficient(23.3)of all three electrodes.Based on the experimental results,a growth model combined direct bottom-injection with micro-convection is proposed to illustrate the surface geometry dependent coefficients,i.e.,the relationship between geometry and bubble evolution kinetics.The direct injection of generated gas molecules from the bottom of bubbles at the three phase boundaries are believed the key to tailor the bubble wetting states and thus determine the bubble evolution kinetics.展开更多
Bubble evolution behaviors play important roles in bubble emission reactions.Here we fabricated one-dimensional(1D)-aligned MoSx microgrids to investigate the influence of the periodic structure on bubble releasing.It...Bubble evolution behaviors play important roles in bubble emission reactions.Here we fabricated one-dimensional(1D)-aligned MoSx microgrids to investigate the influence of the periodic structure on bubble releasing.It is demonstrated that the utilization of the surface energy released during coalescence of bubbles causes them to jump from the electrode,which can be an effective route to eliminate the bubble shielding effect.Under the optimized architecture with 40-μm-wide grooves,the generated bubbles tend to coalesce and release from the electrode with much smaller size(65%less in volume).By balancing the coalescence efficiency and the adhesive work via the architecture engineering,the electrocatalytic performance can be promoted with the rapid bubble removal and lowered ohmic resistance.The results provide new insights into the rational design of novel catalytic electrode architectures and promote their applications in related fields.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11475229
文摘Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473K for 30rain. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy （XTEM） analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases. The growth of He bubbles after high temperature annealingabides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914＋0.236eV.
基金support from National Natural Science Foundation of China,Grant Nos.52241701 and 52307249Shanghai Pujiang Program,Nos.22PJ1413100Fundamental Research Funds for the Central Universities at Tongji University,Nos.PA22120220426.
文摘It is anticipated that alkaline water electrolysis(AWE)technology will assume a significant role in the future energy sector,facilitating the integration of renewable energy and hydrogen production.Regrettably,the effi-ciency of AWE is not yet optimal.In particular,the inefficiency caused by bubbles at increased current density is often overlooked,necessitating a detailed understanding of the intricate relationship between bubble evolution and electrolytic reactions.This paper presents a comprehensive review of the fundamental theory and recent research on bubbles,and outlines the primary challenges and research directions for bubble dynamics in AWE.First,the theory of bubble nucleation,growth,and detachment is reviewed and summarized.Subsequently,the impact of bubbles on the diverse processes occurring during the electrolysis reaction is meticulously delineated and examined.The following section presents a thorough compilation and categorization of the methods employed to remove bubbles,with a detailed analysis of the strategies deployed to mitigate the impact of gas bubble traffic.Additionally,an in-depth exploration of the research methodology employed at each stage of the bubble evolution process is provided.Finally,the review concludes with a summary and outlook on the oppor-tunities and challenges associated with studying bubble dynamics in AWE,offering insights into innovative av-enues for efficient electrolytic hydrogen production.
基金supported by the National Natural Science Foundation of China(Grant Nos.12022515,11975304,and 91126012)the Youth Innovation Promotion Association,CAS(Grant No.202063)。
文摘We report helium ion irradiation experiments for a new type of dispersion-strengthened NiMo-Y_(2)O_(3)alloy with three different irradiation doses and varying irradiation dose rates at 750℃to evaluate its helium-induced damage behavior.Transmission electron microscopy was used to reveal the evolution of helium bubbles after irradiation.The experimental results show that with increasing ion dose,the number density of helium bubbles increases continuously.However,the mean size of helium bubbles first increases and then decreases,mainly due to the varied ion dose rates.The volume fractions of helium bubbles in the three investigated samples after irradiation are 0.15%,0.32%,and 0.27%,which are lower than that of the Hastelloy N alloy(0.58%)after similar irradiation conditions.This indicates that the NiMo-Y_(2)O_(3)alloy exhibits better helium-induced-swelling resistance than the Hastelloy N alloy,highlighting its potential applicability to MSRs,from the perspective of irradiation performance.
基金supported by the National Natural Science Foundation of China (12322510 and 12275174)the Shanghai Rising-Star Program (22QA1404500)+1 种基金the Science and Technology Commission of Shanghai Municipality (24DZ3100300)the Lingchuang Project of China National Nuclear Corporation
文摘Two-phase flow with complex phase interfaces is commonly observed in both nature and industrial processes.The bubble size distribution(BSD) is a crucial parameter in gas-liquid two-phase flow,impacting various flow characteristics including interfacial forces,void fraction distribution,and interfacial area transport.Throughout the flow progression,the BSD changes along the channel due to variations in pressure and interactions among bubbles.Accurately predicting the evolution of BSD can enhance the modeling of two-phase flow.This study presents a novel BSD evolution(BSDE) model,where the governing equation for the probability density function is formulated by considering the conservation of bubbles within a onedimensional control volume in the channel.The downstream BSD is predicted based on the upstream BSD and the effects of pressure variations and bubble interactions along the channel.To account for the multiscale nature of the two-phase flow,the bubbles are categorized into small groups(G_(1)) and large groups(G_(2)).Six distinct source term distributions for intra/inter bubble interactions have been developed.Each source term accounts for the distributions of consumed and generated bubbles,ensuring the conservation of bubble volume through constraints on model coefficients.The model has been tested on a tight-lattice rod bundle using experimental data,with deviations of less than 5% and 15% for G_(1)and G_(2) flow,respectively.Since the model development is independent of specific geometry,the framework of the BSDE model can also be effectively applied to channels of varying shapes.
基金This work was supported by the National Natural Science Foundation of China(NSFC)the National Key Research and Development Project(Nos.2018YFB1502401 and 2018YFA0702002)+3 种基金the Royal Society and the Newton Fund through the Newton Advanced Fellowship award(NAF\R1\191294)the Program for Changjiang Scholars and Innovation Research Team in the University(No.IRT1205)the Fundamental Research Funds for the Central Universitiesthe long-term subsidy mechanism from the Ministry of Finance and the Ministry of Education of China.
文摘Understanding bubbles evolution kinetics on electrodes with varied geometries is of fundamental importance for advanced electrodes design in gas evolution reaction.In this work,the evolution kinetics of electro-generated hydrogen bubbles are recorded in situ on three(i.e.smooth,nanoporous,and nanoarray)Pt electrodes to identify the geometry dependence.The bubble radius shows a time-dependent growth kinetic,which is tightly-connected to the electrode geometry.Among the three electrodes,the smooth one shows a typical time coefficient of 0.5,in consistence with reported values;the nanoporous one shows a time coefficient of 0.47,less than the classic one(0.5);while the nanoarray one exhibits fastest bubble growth kinetics with a time coefficient higher than 0.5(0.54).Moreover,the nanoarray electrode has the smallest bubble detachment size and the largest growth coefficient(23.3)of all three electrodes.Based on the experimental results,a growth model combined direct bottom-injection with micro-convection is proposed to illustrate the surface geometry dependent coefficients,i.e.,the relationship between geometry and bubble evolution kinetics.The direct injection of generated gas molecules from the bottom of bubbles at the three phase boundaries are believed the key to tailor the bubble wetting states and thus determine the bubble evolution kinetics.
基金the National Natural Science Foundation of China(21675007,21676015,21520102002,91622116 and 22005022)the National Key Research and Development Project(2018YFB1502401 and 2018YFA0702002)+2 种基金the Royal Society and Newton Fund through Newton Advanced Fellowship award(NAF\R1\191294)the Program for Changjiang Scholars and Innovation Research Team in the University(IRT1205)the Fundamental Research Funds for the Central Universities and the long-term subsidy mechanism from the Ministry of Finance and the Ministry of Education of China。
文摘Bubble evolution behaviors play important roles in bubble emission reactions.Here we fabricated one-dimensional(1D)-aligned MoSx microgrids to investigate the influence of the periodic structure on bubble releasing.It is demonstrated that the utilization of the surface energy released during coalescence of bubbles causes them to jump from the electrode,which can be an effective route to eliminate the bubble shielding effect.Under the optimized architecture with 40-μm-wide grooves,the generated bubbles tend to coalesce and release from the electrode with much smaller size(65%less in volume).By balancing the coalescence efficiency and the adhesive work via the architecture engineering,the electrocatalytic performance can be promoted with the rapid bubble removal and lowered ohmic resistance.The results provide new insights into the rational design of novel catalytic electrode architectures and promote their applications in related fields.
