Micron-sized silicon anodes offer significant industrial advantages over nanoscale counterparts due to their cost-effectiveness and scalability.However,their practical applications are significantly hindered by severe...Micron-sized silicon anodes offer significant industrial advantages over nanoscale counterparts due to their cost-effectiveness and scalability.However,their practical applications are significantly hindered by severe stress-induced fragmentation,leading to rapid capacity decay.Addressing this challenge,we introduce a novel dual-conformal encapsulated micron-sized porous Si(μm-pSi)anode by utilizingμm-Si recycled from the photovoltaic industry as the Si precursor.This encapsulation design of the internal conformal SiO_(x)/C layer and external Ti_(3)C_(2)Tx MXene layer forms intergranular and intragranular protective skins onμm-pSi,ensuring simultaneous mechanical and electrochemical stability for efficient Li+storage.As a result,the fabricated WpSi@SiO_(x)/C@MXene anode demonstrates an exceptional cycling performance,delivering 535.1 mA h g^(−1)after 1500 cycles at 5 A g^(−1)with a minimal capacity decay of 0.003%per cycle.Chemo-mechanical modeling and SEI analysis reveal that the dual-conformal coating achieves exceptional mechanical and electrochemical stability through robust mechanical confinement and ultra-fast Li+diffusion kinetics during lithiation,coupled with a Li_(2)CO_(3)/LiF-rich hybrid SEI that facilitates Li+transport,collectively enabling rate-insensitive stress evolution,long-term structural durability,and stable cycling under high-rate conditions.This work provides a compelling design strategy for leveraging sustainableμm-Si to achieve high-rate and long-life lithium-ion batteries.展开更多
Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cyclin...Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cycling leads to the accumulation of undesirable stresses,resulting in pulverization of silicon microparticles and shortened lifespan of the batteries.Herein,a composite film of Cu-PET-Cu is proposed as the current collector(CC)forμSi anodes to replace the conventional Cu CC.Cu-PET-Cu CC is prepared by depositing Cu on both sides of a polyethylene terephthalate(PET)film.The PET layer promises good ductility of the film,permitting the Cu-PET-Cu CC to accommodate the volumetric changes of silicon microparticles and facilitates the stress release through ductile deformation.As a result,theμSi electrode with Cu-PET-Cu CC retains a high specific capacity of 2181 mA h g^(-1),whereas theμSi electrode with Cu CC(μSi/Cu)exhibits a specific capacity of 1285 mA h g^(-1)after 80 cycles.The stress relieving effect of CuPET-Cu was demonstrated by in-situ fiber optic stress monitoring and multi-physics simulations.This work proposes an effective stress relief strategy at the electrode level for the practical implementation ofμSi anodes.展开更多
In the exploitation process of offshore natural gas hydrate(“hydrate”for short),it is necessary to take into consideration the wear of wellbore equipment caused by micron-sized sand particles after their breaking th...In the exploitation process of offshore natural gas hydrate(“hydrate”for short),it is necessary to take into consideration the wear of wellbore equipment caused by micron-sized sand particles after their breaking through the sand control facility of the wellbore.At present,however,there is no literature on the migration,deposition and blockage of micron-sized sand particles(<44 μm)after their flowing into the wellbore with the formation fluid.To deal with this situation,this paper took the sand particles in a throttling helical tube section for water transport in the process of depressurization hydrate exploitation as the research object.After a geometric model of flow channel was established for numerical simulation,the migration and deposition laws of micron-sized sand particles were analyzed and the critical non-deposition water velocity of micronsized sand particles under different conditions was obtained.And the following research results were obtained.First,micron-sized sand particles are mainly accumulated in the helical tube section of a complex pipeline,and the deposition of sand particles decreases with the increase of water velocity.The sand particles deposited in the upper part of the helical tube section are more difficult to clean than those in the lower part.Second,the critical non-deposition water velocity increases gradually with the increase of sand particle size and sand production concentration.Third,the variables are nondimensionalized by applying the Buckingham-P theorem.And the model for predicting the sand deposition concentration in the local complex wellbore section during hydrate production test can be obtained using the OriginPro 2019 non-linear fitting tool.Fourth,based on the proposed concept of sand deposition concentration ratio,combined with the deposition prediction model,it is convenient to calculate critical non-deposition water velocity of micron-sized sand particles and to judge the situation of sand deposition in the wellbore.In conclusion,a method for determining the critical non-deposition water velocity of micron-sized sand particles in the local complex wellbore section during the hydrate production test is proposed.And by virtue of this method,the critical non-deposition water velocity of micron-sized sand particles under three particle sizes and three sand production concentrations is obtained respectively.And the research results provide a basis for the reasonable arrangement of hydrate production system and pressure reduction range.展开更多
Magnesium hydroxide is an important chemi- cal, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtr...Magnesium hydroxide is an important chemi- cal, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal （MSMPR） crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction （XRD）, Scanning Electron Micro- scopy （SEM） and Malvem laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg（OH）2. The spherical Mg（OH）2 with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients （R2） based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size- dependent growth models.展开更多
The development of high energy density LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode materials for lithium-ion batteries are challenged by capacity degradation,which becomes more aggravated particularly at elevated temperature...The development of high energy density LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode materials for lithium-ion batteries are challenged by capacity degradation,which becomes more aggravated particularly at elevated temperatures.Thus,the practical strategy with facile craft and the viability of large-scale preparation for industrialized applications should be developed urgently.In this work,a micron-sized LNMO single crystals is synthesized by a facile two-step method consisting of an alcohol gel solvent method and a segmented sintering reaction.Results show that the truncated polyhedron LNMO-900 sample,with the moderate D50 characteristic value of 4.429 mm and the highest tap density of 2.31 g cm^(-3),provides a stable structural and chemical stability even at elevated testing temperature due to its moderate specific surface area and the few Fd-3m phase.The LNMO/Li half-cells display more excellent capacity retention(87.3% at 1C and 25℃ after 500 cycles)and better thermal stability(76.65% at 1C and 55℃ after 200 cycles)than those of the single crystals of LNMO-850 and LNMO-950.Besides,the XPS,in-situ EIS and electrochemical tests results also prove that the LNMO-900 exhibits the lowest electrolyte decomposition degree,owing to a thin and effective solid-electrolyte interfacial film formed after cycles.展开更多
During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of san...During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of sand particles on hydrate formation mechanisms and rheological properties remains poorly understood.Consequently,using a high-pressure reactor system,the phase equilibrium conditions,hydrate formation characteristics,hydrate concentration,and the slurry viscosity in micron-sized sand system are investigated in this work.Furthermore,the effects of sand particle size,sand concentration,and initial pressure on these properties are analyzed.The results indicate that a high concentration of micron-sized sand particles enhances the formation of methane hydrates.When the volume fraction of sand particles exceeds or equals 3%,the phase equilibrium conditions of the methane hydrate shift to the left relative to that of the pure water system(lower temperature,higher pressure).This shift becomes more pronounced with smaller particle sizes.Besides,under these sand concentration conditions,methane hydrates exhibit secondary or even multiple formation events,though the formation rate decreases.Additionally,the torque increases significantly and fluctuates considerably.The Roscoe-Brinkman model yields the most accurate slurry viscosity calculations,and as sand concentration increases,both hydrate concentration and slurry viscosity also increase.展开更多
Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas hydrates.The effect of micronsized sands ...Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas hydrates.The effect of micronsized sands with various concentrations and particle sizes on the hydrate formation,dissociation,and viscosity in gas-water-sand system are investigated in this work.The experimental results show that the hydrate induction time in the sandy system is slightly prolonged compared to the pure gas-water system,and the inhibition effect first strengthens and then weakens as the sand concentration increases from0 wt%to 5 wt%.Besides,the difference of hydrate formation amount in various cases is not obvious.The concentration and particle size of sand have little effect on the kinetics of hydrate formation.Both promoting and inhibiting effects on hydrate formation have been found in the sandy multiphase fluid.For the viscosity characteristics,there are three variations of hydrate slurry viscosity during the formation process:Steep drop type,S-type and Fluctuation type.Moreover,appropriate sand size is helpful to reduce the randomness of slurry viscosity change.Meanwhile,even at the same hydrate volume fraction,the slurry viscosity in the formation process is significantly higher than that in dissociation process,which needs further research.This work provides further insights of hydrate formation,dissociation,and viscosity in gas-water-sand system,which is of great significance for safe and economic development of natural gas hydrates.展开更多
Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,...Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.展开更多
A B_(4)C@amorphous carbon(APC)/Al matrix composite was fabricated by using hydrothermal carbonized deposition on chips(HTCDC)process and solid-state synthesis process.The microstructure and mechanical properties of th...A B_(4)C@amorphous carbon(APC)/Al matrix composite was fabricated by using hydrothermal carbonized deposition on chips(HTCDC)process and solid-state synthesis process.The microstructure and mechanical properties of the B_(4)C@APC/Al matrix composite were investigated.After HTCDC process,nano-B_(4)C particles(50 nm)and micron-sized B_(4)C@APC core-shell spheres with a diameter of 2μm were found in the composites.The microhardness of the micron-sized B_(4)C@APC spheres is 1.66 GPa,which is greater than that of theα-Al matrix(1.06 GPa).Dislocation accumulation is observed around the micron-sized B_(4)C@APC spheres,indicating that the micron-sized B_(4)C@APC spheres have a strengthening effect on theα-Al matrix.Due to the formation of micron-sized B_(4)C@APC spheres,the reinforcement of nano-B_(4)C particles into the composites is transformed from single-sized particle enhancement to bimodal-sized particle enhancement.The strengthening mechanism for B_(4)C@APC/Al matrix composites with bimodalsized particles of nano-B_(4)C and micron-sized B_(4)C@APC spheres were analyzed,which includes thermal mismatch strengthening generated by the mismatch of coefficient of thermal expansion(CTE)between micron-sized B_(4)C@APC core-shell spheres andα-Al matrix,Orowan strengthening produced by nano-B_(4)C particles,Hall-Petch strengthening and load transfer strengthening produced by the bimodal-sized enhancement from nano and microspheres.A relationship model between the yield strength(YS)increment and the conversion rate(x)of micron-sized B_(4)C@APC core-shell spheres was estimated.展开更多
水系质子电池具有安全、环保、动力学快、成本低等优点,是一种很有前途的电化学储能系统.这些优点的实现依赖于开发合适且易于获取的电极材料.本文研究了微米尺度的H_(2)MoO_(3)/VPANI作为质子电池负极材料的高倍率性能和稳定性.与大多...水系质子电池具有安全、环保、动力学快、成本低等优点,是一种很有前途的电化学储能系统.这些优点的实现依赖于开发合适且易于获取的电极材料.本文研究了微米尺度的H_(2)MoO_(3)/VPANI作为质子电池负极材料的高倍率性能和稳定性.与大多数负极材料的赝电容性质相反,H_(2)MoO_(3)/PANI同时具有的高比容量和高倍率性能是基于扩散控制的电荷存储机制.H_(2)MoO_(3)/PANI电极在1.0 A g^(-1)时具有268.2 mAh g^(-1)的高比容量,在200.0 A g^(-1)的极高电流密度下也仍然具有高达50%的比容量保持率.本文详细分析了H_(2)MoO_(3)/PANI中超快质子传导的Grotthuss机制.基于H_(2)MoO_(3)/PANI构建的质子全电池在800.0 W kg^(-1)下的能量密度高达42.1 Wh kg^(-1).令人印象深刻的是,即使在冷冻电解质中,质子全电池仍然具有快速的质子传输能力,在-20℃保持了约70%的是室温比容量.这些优异的质子存储性能为微米尺度的电极材料在低温质子电池中的实际应用提供了重要见解.展开更多
基金the financial support from the Natural Science Foundation of Shanghai(23ZR1423800)Open Research Fund of Shanghai Key Laboratory of Green Chemistry and Chemical Processes(East China Normal University,202503)+1 种基金State Key Laboratory of Advanced Fiber Materials(Donghua University,KF2406)Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Nankai University。
文摘Micron-sized silicon anodes offer significant industrial advantages over nanoscale counterparts due to their cost-effectiveness and scalability.However,their practical applications are significantly hindered by severe stress-induced fragmentation,leading to rapid capacity decay.Addressing this challenge,we introduce a novel dual-conformal encapsulated micron-sized porous Si(μm-pSi)anode by utilizingμm-Si recycled from the photovoltaic industry as the Si precursor.This encapsulation design of the internal conformal SiO_(x)/C layer and external Ti_(3)C_(2)Tx MXene layer forms intergranular and intragranular protective skins onμm-pSi,ensuring simultaneous mechanical and electrochemical stability for efficient Li+storage.As a result,the fabricated WpSi@SiO_(x)/C@MXene anode demonstrates an exceptional cycling performance,delivering 535.1 mA h g^(−1)after 1500 cycles at 5 A g^(−1)with a minimal capacity decay of 0.003%per cycle.Chemo-mechanical modeling and SEI analysis reveal that the dual-conformal coating achieves exceptional mechanical and electrochemical stability through robust mechanical confinement and ultra-fast Li+diffusion kinetics during lithiation,coupled with a Li_(2)CO_(3)/LiF-rich hybrid SEI that facilitates Li+transport,collectively enabling rate-insensitive stress evolution,long-term structural durability,and stable cycling under high-rate conditions.This work provides a compelling design strategy for leveraging sustainableμm-Si to achieve high-rate and long-life lithium-ion batteries.
基金supported by the the National Key R&D Program of China(2022YFB3803500)the Natural Science Foundation of Hubei Province(2021CFA066).
文摘Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cycling leads to the accumulation of undesirable stresses,resulting in pulverization of silicon microparticles and shortened lifespan of the batteries.Herein,a composite film of Cu-PET-Cu is proposed as the current collector(CC)forμSi anodes to replace the conventional Cu CC.Cu-PET-Cu CC is prepared by depositing Cu on both sides of a polyethylene terephthalate(PET)film.The PET layer promises good ductility of the film,permitting the Cu-PET-Cu CC to accommodate the volumetric changes of silicon microparticles and facilitates the stress release through ductile deformation.As a result,theμSi electrode with Cu-PET-Cu CC retains a high specific capacity of 2181 mA h g^(-1),whereas theμSi electrode with Cu CC(μSi/Cu)exhibits a specific capacity of 1285 mA h g^(-1)after 80 cycles.The stress relieving effect of CuPET-Cu was demonstrated by in-situ fiber optic stress monitoring and multi-physics simulations.This work proposes an effective stress relief strategy at the electrode level for the practical implementation ofμSi anodes.
基金supported by the National Major Science and Technology Project“Drilling hydraulics and borehole cleaning supporting techniques for complex structural cluster wells”(No.:2017ZX05009-003)National Natural Science Foundation Project of China“Rotary drive mechanism study on the hydraulicmagnetic coupling self-rotation borehole cleaning tools”(No.:51674087)Innovative Science and Research Project for the Postgraduates of Northeast Petroleum University“Cohesion mechanism and flow assurance study on the natural gas hydrates during deep-water drilling”(No.:YJSCX2017-008NEPU).
文摘In the exploitation process of offshore natural gas hydrate(“hydrate”for short),it is necessary to take into consideration the wear of wellbore equipment caused by micron-sized sand particles after their breaking through the sand control facility of the wellbore.At present,however,there is no literature on the migration,deposition and blockage of micron-sized sand particles(<44 μm)after their flowing into the wellbore with the formation fluid.To deal with this situation,this paper took the sand particles in a throttling helical tube section for water transport in the process of depressurization hydrate exploitation as the research object.After a geometric model of flow channel was established for numerical simulation,the migration and deposition laws of micron-sized sand particles were analyzed and the critical non-deposition water velocity of micronsized sand particles under different conditions was obtained.And the following research results were obtained.First,micron-sized sand particles are mainly accumulated in the helical tube section of a complex pipeline,and the deposition of sand particles decreases with the increase of water velocity.The sand particles deposited in the upper part of the helical tube section are more difficult to clean than those in the lower part.Second,the critical non-deposition water velocity increases gradually with the increase of sand particle size and sand production concentration.Third,the variables are nondimensionalized by applying the Buckingham-P theorem.And the model for predicting the sand deposition concentration in the local complex wellbore section during hydrate production test can be obtained using the OriginPro 2019 non-linear fitting tool.Fourth,based on the proposed concept of sand deposition concentration ratio,combined with the deposition prediction model,it is convenient to calculate critical non-deposition water velocity of micron-sized sand particles and to judge the situation of sand deposition in the wellbore.In conclusion,a method for determining the critical non-deposition water velocity of micron-sized sand particles in the local complex wellbore section during the hydrate production test is proposed.And by virtue of this method,the critical non-deposition water velocity of micron-sized sand particles under three particle sizes and three sand production concentrations is obtained respectively.And the research results provide a basis for the reasonable arrangement of hydrate production system and pressure reduction range.
文摘Magnesium hydroxide is an important chemi- cal, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal （MSMPR） crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction （XRD）, Scanning Electron Micro- scopy （SEM） and Malvem laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg（OH）2. The spherical Mg（OH）2 with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients （R2） based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size- dependent growth models.
基金This work was supported by the National Natural Science Foundation of China(no.51962019 and 21766017)the Gansu Province Science and Technology Major Project(no.18ZD2FA012)the Lanzhou University of Technology Hongliu First-class Discipline Construction Program.
文摘The development of high energy density LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode materials for lithium-ion batteries are challenged by capacity degradation,which becomes more aggravated particularly at elevated temperatures.Thus,the practical strategy with facile craft and the viability of large-scale preparation for industrialized applications should be developed urgently.In this work,a micron-sized LNMO single crystals is synthesized by a facile two-step method consisting of an alcohol gel solvent method and a segmented sintering reaction.Results show that the truncated polyhedron LNMO-900 sample,with the moderate D50 characteristic value of 4.429 mm and the highest tap density of 2.31 g cm^(-3),provides a stable structural and chemical stability even at elevated testing temperature due to its moderate specific surface area and the few Fd-3m phase.The LNMO/Li half-cells display more excellent capacity retention(87.3% at 1C and 25℃ after 500 cycles)and better thermal stability(76.65% at 1C and 55℃ after 200 cycles)than those of the single crystals of LNMO-850 and LNMO-950.Besides,the XPS,in-situ EIS and electrochemical tests results also prove that the LNMO-900 exhibits the lowest electrolyte decomposition degree,owing to a thin and effective solid-electrolyte interfacial film formed after cycles.
基金supported by the Natural Science Starting Project of Sichuan Provincial Youth Foundation Project(2025ZNSFSC1356)Southwest Petroleum University,China(2023QHZ019)+1 种基金General Project of the Sichuan Provincial Natural Science Foundation,China(24NSFSC1295)Open fund of Dazhou Industrial Technology Institute of Intelligent Manufacturing,China(ZNZZ2215).
文摘During the production of natural gas hydrates,micron-sized sand particles coexist with hydrate within the transportation pipeline,posing a significant threat to the safety of pipeline flow.However,the influence of sand particles on hydrate formation mechanisms and rheological properties remains poorly understood.Consequently,using a high-pressure reactor system,the phase equilibrium conditions,hydrate formation characteristics,hydrate concentration,and the slurry viscosity in micron-sized sand system are investigated in this work.Furthermore,the effects of sand particle size,sand concentration,and initial pressure on these properties are analyzed.The results indicate that a high concentration of micron-sized sand particles enhances the formation of methane hydrates.When the volume fraction of sand particles exceeds or equals 3%,the phase equilibrium conditions of the methane hydrate shift to the left relative to that of the pure water system(lower temperature,higher pressure).This shift becomes more pronounced with smaller particle sizes.Besides,under these sand concentration conditions,methane hydrates exhibit secondary or even multiple formation events,though the formation rate decreases.Additionally,the torque increases significantly and fluctuates considerably.The Roscoe-Brinkman model yields the most accurate slurry viscosity calculations,and as sand concentration increases,both hydrate concentration and slurry viscosity also increase.
基金supported by the National Natural Science Foundation of China[Grand numbers:52104069,51874323,U20B6005]China Postdoctoral Science Foundation[Grand number:2022M713460]Science Foundation of China University of Petroleum,Beijing[Grand number:2462020YXZZ045]。
文摘Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas hydrates.The effect of micronsized sands with various concentrations and particle sizes on the hydrate formation,dissociation,and viscosity in gas-water-sand system are investigated in this work.The experimental results show that the hydrate induction time in the sandy system is slightly prolonged compared to the pure gas-water system,and the inhibition effect first strengthens and then weakens as the sand concentration increases from0 wt%to 5 wt%.Besides,the difference of hydrate formation amount in various cases is not obvious.The concentration and particle size of sand have little effect on the kinetics of hydrate formation.Both promoting and inhibiting effects on hydrate formation have been found in the sandy multiphase fluid.For the viscosity characteristics,there are three variations of hydrate slurry viscosity during the formation process:Steep drop type,S-type and Fluctuation type.Moreover,appropriate sand size is helpful to reduce the randomness of slurry viscosity change.Meanwhile,even at the same hydrate volume fraction,the slurry viscosity in the formation process is significantly higher than that in dissociation process,which needs further research.This work provides further insights of hydrate formation,dissociation,and viscosity in gas-water-sand system,which is of great significance for safe and economic development of natural gas hydrates.
基金supported by the National Key R&D Program of China(2021YFB2401800)the National Natural Science Foundation of China(22179008,21875022)+2 种基金the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0589,cstc2020jcyjmsxmX0654)the support from Beijing Institute of Technology Research Fund Program for Young Scholarsthe 4B7B beamlines radiation equipment of Beijing Synchrotron Radiation Facility(2021-BEPC-PT-005924,2021-BEPC-PT-005967)。
文摘Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.
基金financially supported by the National Natural Science Foundation of China(No.51704087)the Natural Science Foundation of Heilongjiang Province(No.LH2020E083)。
文摘A B_(4)C@amorphous carbon(APC)/Al matrix composite was fabricated by using hydrothermal carbonized deposition on chips(HTCDC)process and solid-state synthesis process.The microstructure and mechanical properties of the B_(4)C@APC/Al matrix composite were investigated.After HTCDC process,nano-B_(4)C particles(50 nm)and micron-sized B_(4)C@APC core-shell spheres with a diameter of 2μm were found in the composites.The microhardness of the micron-sized B_(4)C@APC spheres is 1.66 GPa,which is greater than that of theα-Al matrix(1.06 GPa).Dislocation accumulation is observed around the micron-sized B_(4)C@APC spheres,indicating that the micron-sized B_(4)C@APC spheres have a strengthening effect on theα-Al matrix.Due to the formation of micron-sized B_(4)C@APC spheres,the reinforcement of nano-B_(4)C particles into the composites is transformed from single-sized particle enhancement to bimodal-sized particle enhancement.The strengthening mechanism for B_(4)C@APC/Al matrix composites with bimodalsized particles of nano-B_(4)C and micron-sized B_(4)C@APC spheres were analyzed,which includes thermal mismatch strengthening generated by the mismatch of coefficient of thermal expansion(CTE)between micron-sized B_(4)C@APC core-shell spheres andα-Al matrix,Orowan strengthening produced by nano-B_(4)C particles,Hall-Petch strengthening and load transfer strengthening produced by the bimodal-sized enhancement from nano and microspheres.A relationship model between the yield strength(YS)increment and the conversion rate(x)of micron-sized B_(4)C@APC core-shell spheres was estimated.
基金supported by the National Natural Science Foundation of China(12274150,12274151)Natural Science Foundation of Hubei Province,China(2022CFB101,2022BAD061)。
文摘水系质子电池具有安全、环保、动力学快、成本低等优点,是一种很有前途的电化学储能系统.这些优点的实现依赖于开发合适且易于获取的电极材料.本文研究了微米尺度的H_(2)MoO_(3)/VPANI作为质子电池负极材料的高倍率性能和稳定性.与大多数负极材料的赝电容性质相反,H_(2)MoO_(3)/PANI同时具有的高比容量和高倍率性能是基于扩散控制的电荷存储机制.H_(2)MoO_(3)/PANI电极在1.0 A g^(-1)时具有268.2 mAh g^(-1)的高比容量,在200.0 A g^(-1)的极高电流密度下也仍然具有高达50%的比容量保持率.本文详细分析了H_(2)MoO_(3)/PANI中超快质子传导的Grotthuss机制.基于H_(2)MoO_(3)/PANI构建的质子全电池在800.0 W kg^(-1)下的能量密度高达42.1 Wh kg^(-1).令人印象深刻的是,即使在冷冻电解质中,质子全电池仍然具有快速的质子传输能力,在-20℃保持了约70%的是室温比容量.这些优异的质子存储性能为微米尺度的电极材料在低温质子电池中的实际应用提供了重要见解.
