An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature unifor...An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature uniformity. To address the high energy consumption of secondary cooling loops in vehicles for cooling immersion oil, this paper proposes a method of immersion coupled cooling tubes. Battery heat is directly absorbed by the immersion liquid and rapidly dissipated via cooling water in the S-type cooling tube(SCT). This work investigated the effects of structural parameters, immersion fluid medium, and operating parameters on the cooling performance of the BTMS. The results showed that the fin height(h_(f)) has no significant effect on the cooling performance. Both Transformer Oil and HFE-7100 delivered outstanding thermal management, reaching a maximum of 36.73℃ and 41.39℃ while maintaining narrow temperature differences of only 3.70℃ and 2.09℃ apart, respectively. When the ambient temperature reached 40℃ and HFE-7100 was used as the immersion liquid, the maximum temperature difference remained consistently below 3℃. Subsequently, a sensitivity analysis was conducted on the respective influential parameters. It was found that inlet water temperature(T_(in)) and immersion fluids exert the most significant influence on the system performance. Finally, different immersion cooling schemes were compared, which demonstrated the advantages of the system proposed in this study under harsh condition, thereby supporting the application of different schemes under various scenarios. It can be directly integrated with the vehicle-mounted cooling circuit system, thereby reducing energy consumption and weight, and offering new insights for research on thermal management systems for EVs.展开更多
In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooli...This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”展开更多
To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water d...To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water distribution states.Uniaxial compression tests were conducted on red sandstone under these conditions.The effects of non-uniform water distribution on deformation,failure,strength,and energy characteristics of red sandstone were analyzed.The impact of non-uniform water distribution on the intensity of rock failure was discussed,and the failure mechanism under non-uniform water distribution was revealed.The hazards of low immersion heights on underground rock structures were analyzed.The results demonstrate that peak strength and elastic modulus of red sandstone exhibit high sensitivity to immersion height,with reductions of 38%and 23%respectively even at L=1/50H.Water immersion reduces both energy storage capacity and energy dissipation capability of red sandstone.The immersion height and duration influence the failure mode of red sandstone by controlling the migration and separation of dry-wet interfaces.Low immersion height poses significant risks to underground rock structures(e.g.,a 38%strength reduction when L=1/50H),and the concentration degree of water non-uniform distribution is the key factor in assessing the weakening effect of water on rocks.展开更多
The self-healing properties of dual-component epoxy microcapsules are evaluated when incorporated into an epoxy coating.The performance of the coating was assessed under immersion in a saline solution,simulating seawa...The self-healing properties of dual-component epoxy microcapsules are evaluated when incorporated into an epoxy coating.The performance of the coating was assessed under immersion in a saline solution,simulating seawater conditions.Initially,synthesized microcapsules are incorporated into the epoxy coating.Then,the self-healing capabilities of the coating are studied under immersion using scanning vibrating electrode technique(SVET),open circuit potential(OCP),electrochemical impedance spectroscopy(EIS)and immersion corrosion test on coated samples with intentionally created artificial defects.The last three tests were conducted in a 3.5%NaCl solution.The adhesion of the coating is also studied by pull-off adhesion test.SVET analyses reveal lower ionic current densities in coated samples containing microcapsules during 24 h of immersion.EIS results demonstrate self-healing at the defect site for up to 12 h of immersion.After this time,the corrosion protection diminishes with prolonged immersion in the saline solution.Despite this,the coating with the microcapsules exhibits decrease in the corrosion process compared to the coating without the microcapsules.These results are consistent and complement the outcomes of the immersion tests conducted over 360 and 1056 h,which indicate that coated samples without microcapsules exhibit double the corroded areas around the scribes compared to coated samples containing the microcapsules.These findings offer a promising outlook for applying this coating on offshore carbon steel structures under immersion aiming for a longer lifetime with less maintenance intervention.展开更多
The challenge of effectively eliminating air during gastrointestinal endoscopy using ultrasound techniques is apparent.This difficulty arises from the intricacies of removing concealed air within the folds of the gast...The challenge of effectively eliminating air during gastrointestinal endoscopy using ultrasound techniques is apparent.This difficulty arises from the intricacies of removing concealed air within the folds of the gastrointestinal tract,resulting in artifacts and compromised visualization.In addition,the overlap of folds with lesions can obscure their depth and size,presenting challenges for an accurate assessment.Conversely,in intricately folded regions of the gastrointestinal tract,such as the stomach,intestine,and colon,insufficient delivery of air or CO_(2) into the cavity impedes luminal expansion,hindering the accurate visualization of lesions concealed within the folds.Although this underscores the requirement for substantial airflow,excessive airflow can hinder visualization of bleeding lesions and other abnormalities.Considering these challenges,an ideal endoscopic device would facilitate the observation of lesions without the requirement for air or CO_(2) delivery whereas,ensuring optimal expansion of the gastrointestinal tract.Recently,transparent gels with specific viscosities have been employed more frequently to address this issue.This review aims to elucidate how these gels address these challenges and provide a solution for enhanced endoscopic visualization.展开更多
Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data imm...Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.展开更多
Although room-temperature superconductivity is still difficult to achieve,researching materials with electrical conductivity significantly higher than that of copper will be of great importance in improving energy eff...Although room-temperature superconductivity is still difficult to achieve,researching materials with electrical conductivity significantly higher than that of copper will be of great importance in improving energy efficiency,reducing costs,lightening equipment weight,and enhancing overall performance.Herein,this study presents a novel copper-carbon nanofilm composite with enhanced conductivity which has great applications in the electronic devices and electrical equipment.Multilayer copper-carbon nanofilms and interfaces with superior electronic structures are formed based on copper materials using plasma immersion nanocarbon layer deposition technology,effectively enhancing conductivity.Experimental results show that for a five-layer copper-carbon nanofilm composite,the conductivity improves significantly when the thickness of the carbon nanofilm increases.When the carbon nanofilm accounts for 16%of the total thickness,the overall conductivity increases up to 30.20%compared to pure copper.The mechanism of the enhanced conductivity is analyzed including roles of copper atom adsorption sites and electron migration pathways by applying effective medium theory,first-principles calculations and density of states analysis.Under an applied electric field,the high-density electrons in the copper film can migrate into the nanocarbon film,forming highly efficient electron transport channels,which significantly enhance the material’s conductivity.Finally,large-area electrode coating equipment is developed based on this study,providing the novel and robust strategy to enhance the conductivity of copper materials,which enables industrial application of copper-carbon nanocomposite films in the field of high conductivity materials.展开更多
The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for e...The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.展开更多
A nickel-based coating was deposited on the pure Al substrate by immersion plating,and the Al/Cu bimetals were prepared by diffusion bonding in the temperature range of 450-550 ℃.The interce microstructure and fractu...A nickel-based coating was deposited on the pure Al substrate by immersion plating,and the Al/Cu bimetals were prepared by diffusion bonding in the temperature range of 450-550 ℃.The interce microstructure and fracture surface of Al/Cu joints were studied by scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The mechanical properties of the Al/Cu bimetals were measured by tensile shear and microhardness tests.The results show that the Ni interiayer can effectively eliminate the formation of Al-Cu intermetallic compounds.The Al/Ni interface consists of the Al3Ni and Al3Ni2 phases,while it is Ni-Cu solid solution at the Ni/Cu interce.The tensile shear strength of the joints is improved by the addition of Ni interiayer.The joint with Ni interiayer annealed at 500 ℃ exhibits a maximum value of tensile shear strength of 34.7 MPa.展开更多
基金supported by the Science and Technology Projects of Xizang Autonomous Region,China (Grant No.XZ202501ZY0080)。
文摘An effective lithium-ion battery thermal management system(BTMS) ensures the safety of electric vehicles(EVs) and energy storage systems. Immersion cooling is known for high efficiency and excellent temperature uniformity. To address the high energy consumption of secondary cooling loops in vehicles for cooling immersion oil, this paper proposes a method of immersion coupled cooling tubes. Battery heat is directly absorbed by the immersion liquid and rapidly dissipated via cooling water in the S-type cooling tube(SCT). This work investigated the effects of structural parameters, immersion fluid medium, and operating parameters on the cooling performance of the BTMS. The results showed that the fin height(h_(f)) has no significant effect on the cooling performance. Both Transformer Oil and HFE-7100 delivered outstanding thermal management, reaching a maximum of 36.73℃ and 41.39℃ while maintaining narrow temperature differences of only 3.70℃ and 2.09℃ apart, respectively. When the ambient temperature reached 40℃ and HFE-7100 was used as the immersion liquid, the maximum temperature difference remained consistently below 3℃. Subsequently, a sensitivity analysis was conducted on the respective influential parameters. It was found that inlet water temperature(T_(in)) and immersion fluids exert the most significant influence on the system performance. Finally, different immersion cooling schemes were compared, which demonstrated the advantages of the system proposed in this study under harsh condition, thereby supporting the application of different schemes under various scenarios. It can be directly integrated with the vehicle-mounted cooling circuit system, thereby reducing energy consumption and weight, and offering new insights for research on thermal management systems for EVs.
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
文摘This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”
基金supported by the National Natural Science Foundation of China(Nos.52474133,52304227,52304091,and 52374095)the Natural Science Foundation of Hunan Province(Nos.2025JJ50316 and 2023JJ40548).
文摘To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water distribution states.Uniaxial compression tests were conducted on red sandstone under these conditions.The effects of non-uniform water distribution on deformation,failure,strength,and energy characteristics of red sandstone were analyzed.The impact of non-uniform water distribution on the intensity of rock failure was discussed,and the failure mechanism under non-uniform water distribution was revealed.The hazards of low immersion heights on underground rock structures were analyzed.The results demonstrate that peak strength and elastic modulus of red sandstone exhibit high sensitivity to immersion height,with reductions of 38%and 23%respectively even at L=1/50H.Water immersion reduces both energy storage capacity and energy dissipation capability of red sandstone.The immersion height and duration influence the failure mode of red sandstone by controlling the migration and separation of dry-wet interfaces.Low immersion height poses significant risks to underground rock structures(e.g.,a 38%strength reduction when L=1/50H),and the concentration degree of water non-uniform distribution is the key factor in assessing the weakening effect of water on rocks.
基金supported by CAPES scholarship-Brazil Coordination for the Improvement of Higher Education Personnel(No.88887.507764/2020-00)]by CNPq-Brazil National Council of Technological and Scientific Development(No.308564/2023-5).
文摘The self-healing properties of dual-component epoxy microcapsules are evaluated when incorporated into an epoxy coating.The performance of the coating was assessed under immersion in a saline solution,simulating seawater conditions.Initially,synthesized microcapsules are incorporated into the epoxy coating.Then,the self-healing capabilities of the coating are studied under immersion using scanning vibrating electrode technique(SVET),open circuit potential(OCP),electrochemical impedance spectroscopy(EIS)and immersion corrosion test on coated samples with intentionally created artificial defects.The last three tests were conducted in a 3.5%NaCl solution.The adhesion of the coating is also studied by pull-off adhesion test.SVET analyses reveal lower ionic current densities in coated samples containing microcapsules during 24 h of immersion.EIS results demonstrate self-healing at the defect site for up to 12 h of immersion.After this time,the corrosion protection diminishes with prolonged immersion in the saline solution.Despite this,the coating with the microcapsules exhibits decrease in the corrosion process compared to the coating without the microcapsules.These results are consistent and complement the outcomes of the immersion tests conducted over 360 and 1056 h,which indicate that coated samples without microcapsules exhibit double the corroded areas around the scribes compared to coated samples containing the microcapsules.These findings offer a promising outlook for applying this coating on offshore carbon steel structures under immersion aiming for a longer lifetime with less maintenance intervention.
文摘The challenge of effectively eliminating air during gastrointestinal endoscopy using ultrasound techniques is apparent.This difficulty arises from the intricacies of removing concealed air within the folds of the gastrointestinal tract,resulting in artifacts and compromised visualization.In addition,the overlap of folds with lesions can obscure their depth and size,presenting challenges for an accurate assessment.Conversely,in intricately folded regions of the gastrointestinal tract,such as the stomach,intestine,and colon,insufficient delivery of air or CO_(2) into the cavity impedes luminal expansion,hindering the accurate visualization of lesions concealed within the folds.Although this underscores the requirement for substantial airflow,excessive airflow can hinder visualization of bleeding lesions and other abnormalities.Considering these challenges,an ideal endoscopic device would facilitate the observation of lesions without the requirement for air or CO_(2) delivery whereas,ensuring optimal expansion of the gastrointestinal tract.Recently,transparent gels with specific viscosities have been employed more frequently to address this issue.This review aims to elucidate how these gels address these challenges and provide a solution for enhanced endoscopic visualization.
基金Supported by the National Key R&D Program of China(2022YFB3303500).
文摘Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.
基金support from the National Natural Science Foundation of China(61574091)National Natural Science Foundation of China Key Program(50730008).
文摘Although room-temperature superconductivity is still difficult to achieve,researching materials with electrical conductivity significantly higher than that of copper will be of great importance in improving energy efficiency,reducing costs,lightening equipment weight,and enhancing overall performance.Herein,this study presents a novel copper-carbon nanofilm composite with enhanced conductivity which has great applications in the electronic devices and electrical equipment.Multilayer copper-carbon nanofilms and interfaces with superior electronic structures are formed based on copper materials using plasma immersion nanocarbon layer deposition technology,effectively enhancing conductivity.Experimental results show that for a five-layer copper-carbon nanofilm composite,the conductivity improves significantly when the thickness of the carbon nanofilm increases.When the carbon nanofilm accounts for 16%of the total thickness,the overall conductivity increases up to 30.20%compared to pure copper.The mechanism of the enhanced conductivity is analyzed including roles of copper atom adsorption sites and electron migration pathways by applying effective medium theory,first-principles calculations and density of states analysis.Under an applied electric field,the high-density electrons in the copper film can migrate into the nanocarbon film,forming highly efficient electron transport channels,which significantly enhance the material’s conductivity.Finally,large-area electrode coating equipment is developed based on this study,providing the novel and robust strategy to enhance the conductivity of copper materials,which enables industrial application of copper-carbon nanocomposite films in the field of high conductivity materials.
基金Projects(52204226,52104204,52474276)supported by the National Natural Science Foundation of ChinaProject(tsqnz20221140)supported by the Taishan Scholars Project of China+1 种基金Projects(ZR2022QE243,ZR2024ME097)supported by the Natural Science Foundation of Shandong Province of ChinaProject(252300421010)supported by the Excellent Youth Foundation of Henan Scientific Committee,China。
文摘The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.
基金Projects (51274054,51375070,51271042) supported by the National Natural Science Foundation of ChinaProjects (2013M530913) supported by the China Postdoctoral Science Foundation
文摘A nickel-based coating was deposited on the pure Al substrate by immersion plating,and the Al/Cu bimetals were prepared by diffusion bonding in the temperature range of 450-550 ℃.The interce microstructure and fracture surface of Al/Cu joints were studied by scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The mechanical properties of the Al/Cu bimetals were measured by tensile shear and microhardness tests.The results show that the Ni interiayer can effectively eliminate the formation of Al-Cu intermetallic compounds.The Al/Ni interface consists of the Al3Ni and Al3Ni2 phases,while it is Ni-Cu solid solution at the Ni/Cu interce.The tensile shear strength of the joints is improved by the addition of Ni interiayer.The joint with Ni interiayer annealed at 500 ℃ exhibits a maximum value of tensile shear strength of 34.7 MPa.
