The volatilization characteristics and kinetic mechanisms of arsenic were investigated in the temperature range of 623−773 K and pressure ranges of 10−10000 Pa.The experimental results reveal that the evaporation rate...The volatilization characteristics and kinetic mechanisms of arsenic were investigated in the temperature range of 623−773 K and pressure ranges of 10−10000 Pa.The experimental results reveal that the evaporation rate increases with increasing temperature and decreasing pressure.Surface reaction control dominates at low pressures(<100 Pa),whereas diffusion control dominates at high pressures(>5000 Pa).The evaporation behavior is successfully described by an Arrhenius-type model for temperature dependence and Logistic model for pressure dependence.Key kinetic parameters,including the critical pressure,maximum evaporation rate and evaporation coefficient,were calculated.The evaporation coefficient varies between 0.010 and 0.223,and the critical pressures vary between 281 and 478 Pa with temperature.展开更多
The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain ...The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.展开更多
Nanophase iron particles(np-Fe^(0))have multiple formation mechanisms in lunar soil,which are mostly related to meteorite and micro meteorite impacts.Thermal modification of the impact is critical.Metal oxides have un...Nanophase iron particles(np-Fe^(0))have multiple formation mechanisms in lunar soil,which are mostly related to meteorite and micro meteorite impacts.Thermal modification of the impact is critical.Metal oxides have unique chemical and physical properties that allow np-Fe^(0) to form at a lower initial reaction temperature.Through the insitu heating experiment of ilmenite in the Chang'e-5 sample,it was found that ilmenite can form np-Fe^(0) at 400℃under high vacuum(10-6 Pa).This fills in the missing information on the lowest measured temperature at which ilmenite forms np-Fe^(0).At 400-800℃,only np-Fe^(0) and vesicles were formed without new Ti-rich minerals.At the same time,thermodynamic calculations showed that decomposition of ilmenite occurs in two stages.The experiments correspond to the initial stage of ilmenite thermal decomposition under high vacuum.The study explains the thermal decomposition reaction of ilmenite in a vacuum environment,provides a reference for the minimum measured temperature required for the formation of np-Fe^(0),and further improves the formation mechanism of np-Fe^(0).展开更多
Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-cond...Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-conditioned clay soils were investigated,with their potential use as an alternative means to assess foam optimization being examined.A series of laboratory and fieldtests was conducted,including vacuum dewatering tests that considered the effects of filtrationtime and pressure,vane shear tests,and improved cone pullout tests under different gravimetric water content(w)and foam injection ratio(FIR)conditions.It was found that the filtrate loss(FL),which characterizes dewaterability,was increased by extended vacuum filtrationtime and elevated pressure.While increases in w and FIR enhanced FL,reductions were observed in the undrained shear strength(cu),tangential adhesion stress(Fs),and normal adhesion stress(Fn).Furthermore,a linear decrease in FL with increasing mechanical indices(cu,Fs,and Fn)was demonstrated by both laboratory and fielddata fittingresults,regardless of w,FIR,and dewatering conditions.This study provides novel insights into the understanding of vacuum dewatering mechanisms in foam-conditioned clay soils,while a simple approach is proposed for evaluating foam conditioning effectiveness in EPB shield tunneling applications.展开更多
The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is consi...The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is considered one of the most feasible strategies for early lunar infrastructure development. However, the extreme temperature fluctuations on the lunar surface pose potential threats to the structural stability of sintered regolith materials. To investigate the mechanical deterioration and damage mechanism of vacuum-sintered lunar regolith under extreme cryogenic-thermal cycling, lunar regolith simulants are used to fabricate specimens through vacuum sintering. A series of cryogenic-thermal cycling tests is designed, combined with uniaxial compression and X-ray CT scanning, to systematically analyze their macro-micro responses. The results show that with increasing extreme cryogenic-thermal cycles, the stress-strain curves evolve from typical brittle failure to quasiductile behavior, with uniaxial compressive strength and elastic modulus decreasing by approximately 33.86% and 61.98%, respectively. CT analyses reveal that the pore structure transforms from isolated pores to connected networks, with the pore volume fraction increasing from 13.33% to 22.64%, and the fractal dimension increases from 2.465 to 2.544, and stabilizes after multiple cycles. A significant negative correlation(R^(2)> 0.96) exists between pore structural complexity and mechanical performance. Based on these findings, a thermal fatigue damage mechanism dominated by thermal stress concentration due to mismatched thermal expansion coefficients among mineral phases is proposed. This study provides scientific insights for the design, durability evaluation, and ISRU-based construction of lunar surface infrastructure.展开更多
Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In ad...Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In addition,the joint formation mechanism was discussed,and the correlation between joint microstructure and mechanical performance was established.Results show that adding appropriate amount of In into the filler can significantly reduce the filler melting point and enhance the wettability of filler on diamond.When the brazing temperature is 750°C and the soaking time is 10 min,a uniformly dense braze seam with excellent metallurgical bonding can be obtained,and its average joint shear strength reaches 322 MPa.The lower brazing temperature can mitigate the risk of diamond graphitization and also reduce the residual stresses during joining.展开更多
Colonoscopy represents a safe procedure that is widely used in medical practice either to diagnose or treat various gastrointestinal diseases.During the last few years,the incidence rate of perforations in colonoscopi...Colonoscopy represents a safe procedure that is widely used in medical practice either to diagnose or treat various gastrointestinal diseases.During the last few years,the incidence rate of perforations in colonoscopic procedures has increased,especially in therapeutic colonoscopies.The recent advancements in endoscopic techniques and gastrointestinal tumoral resection procedures such as endoscopic mucosal resection,endoscopic full-thickness resection,and endoscopic submucosal dissection(ESD)could be a risk factor for this increased risk.The incidence rate of mortality of serious colonoscopic perforations is 7.1%.The management plan for these perforations starts with conservative treatment in mild cases,endoscopic closure,and surgical management in severe cases.Recently,endoluminal vacuum therapy was found to be effective in the management of colorectal perforations and this has been reported in multiple case reports.This editorial provides an overview of the current guidelines for the management of iatrogenic colorectal perforations.These insights are from the perspectives of endoscopists and gastroenterologists.We also present a management algorithm based on the guidelines of the European Society of Gastrointestinal Endoscopy,the American Gastroenterological Association,and the World Society of Emergency Surgery.We also discussed in brief the use of endoluminal vacuum therapy in colorectal perforations.展开更多
The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with B...The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.展开更多
In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to...In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.展开更多
Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate...Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate than aluminum,and its greater complexity poses challenges to existing recycling processes.Although vacuum distillation can be used to recycle Mg alloy scrap,this requires optimizing and maximizing metal recirculation,but there has been no thermodynamic analysis of this process.In this study,the feasibility and controllability of separating inclusions and 23 metal impurities were evaluated,and their distribution and removal limits were quantified.Thermodynamic analyses and experimental results showed that inclusions and impurity metals of separation coefficient lgβ_(i)≤-5,including Cu,Fe,Co,and Ni below 0.001 ppm,could be removed from the matrix.All Zn entered the recycled Mg,while impurities with-1<lgβ_(i)<-5 such as Li,Ca,and Mn severely affected the purity of the recycled Mg during the later stage of distillation.Therefore,an optimization strategy for vacuum distillation recycling:lower temperatures and higher system pressures for Zn separation in the early stage,and the early termination of the recovery process in the later stage or a continuous supply of raw melt can also prevent contamination during recycling.The alloying elements Al and Zn in Mg alloy scrap can be further recovered and purified by vacuum distillation when economically feasible,to maximize the recycling of metal resources.展开更多
Magnesium and magnesium alloys,serving as crucial lightweight structural materials and hydrogen storage elements,find extensive applications in space technology,aviation,automotive,and magnesium-based hydrogen industr...Magnesium and magnesium alloys,serving as crucial lightweight structural materials and hydrogen storage elements,find extensive applications in space technology,aviation,automotive,and magnesium-based hydrogen industries.The global production of primary magnesium has reached approximately 1.2 million tons per year,with anticipated diversification in future applications and significant market demand.Nevertheless,approximately 80%of the world’s primary magnesium is still manufactured through the Pidgeon process,grappling with formidable issues including high energy consumption,massive carbon emission,significant resource depletion,and environmental pollution.The implementation of the relative vacuum method shows potential in breaking through technological challenges in the Pidgeon process,facilitating clean,low-carbon continuous magnesium smelting.This paper begins by introducing the principles of the relative vacuum method.Subsequently,it elucidates various innovative process routes,including relative vacuum ferrosilicon reduction,aluminum thermal reduction co-production of spinel,and aluminum thermal reduction co-production of calcium aluminate.Finally,and thermodynamic foundations of the relative vacuum,a quantitative analysis of the material,energy flows,carbon emission,and production cost for several new processes is conducted,comparing and analyzing them against the Pidgeon process.The study findings reveal that,with identical raw materials,the relative vacuum silicon thermal reduction process significantly decreases raw material consumption,energy consumption,and carbon dioxide emissions by 15.86%,30.89%,and 26.27%,respectively,compared to the Pidgeon process.The relative vacuum process,using magnesite as the raw material and aluminum as the reducing agent,has the lowest magnesium-to-feed ratio,at only 3.385.Additionally,its energy consumption and carbon dioxide emissions are the lowest,at 1.817 tce/t Mg and 7.782 t CO_(2)/t Mg,respectively.The energy consumption and carbon emissions of the relative vacuum magnesium smelting process co-producing calcium aluminate(12CaO·7Al_(2)O_(3),3CaO·Al_(2)O_(3),and CaO·Al_(2)O_(3))are highly correlated with the consumption of dolomite in the raw materials.When the reduction temperature is around 1473.15 K,the critical volume fraction of magnesium vapor for different processes varies within the range of 5%–40%.Production cost analysis shows that the relative vacuum primary magnesium smelting process has significant economic benefits.This paper offers essential data support and theoretical guidance for achieving energy efficiency,carbon reduction in magnesium smelting,and the industrial adoption of innovative processes.展开更多
BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a ...BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a total of 13 procedures within our medical facility,including five performed under local anesthesia and eight performed under general anesthesia.The source of the ailment was ultimately identified as Enterobacter cloacae.After the last procedure,the patient's symptoms were alleviated,and the recovery process was satisfactory.Three months post-operation,the Japanese Orthopaedic Association scores had improved to 100%.Imageological examination revealed a satisfactory position of internal fixation,and the abnormal signals in the vertebral body and intervertebral space had been eliminated when compared to the pre-operative results.CONCLUSION The study demonstrates that the extreme lateral approach debridement combined with multiple VSD operations is a secure and successful method of treatment for recurrent spinal infection,providing an alternative to traditional surgery.展开更多
Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of meth...Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of methyl iodide and humidity interference are two major issues of the vacuum ultraviolet(VUV)lamp initiated CIMS for on-line gaseous formic and acetic acids analysis.In this work,we present a new CIMS based on VUV lamp,and the ion-molecular reactor is separated into photoionization and chemical ionization zones by a reducer electrode.Acetone was added to the photoionization zone,and the VUV photoionization acetone provided low-energy electrons for methyl iodide to generate I−,and the addition of acetone reduced the amount of methyl iodide by 2/3.In the chemical ionization zone,a headspace vial containing ultrapure water was added for humidity calibration,and the vial changes the sensitivity as a function of humidity from ambiguity to well linear correlation(R2>0.95).With humidity calibration,the CIMS can quantitatively measure formic and acetic acids in the humidity range of 0%-88%RH.In this mode,limits of detection of 10 and 50 pptv are obtained for formic and acetic acids,respectively.And the relative standard deviation(RSD)of quantitation stability for 6 days were less than 10.5%.This CIMS was successfully used to determine the formic and acetic acids in the underground parking and ambient environment of the Shandong University campus(Qingdao,China).In addition,we developed a simple model based formic acid concentration to assess vehicular emissions.展开更多
High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.Hi...High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.High-purity indium was prepared by combining zone refining with vacuum distillation.Results show that the average removal efficiency of impurity Sb can approach 95%,while the removal efficiency of impurities Sn and Bi can reach over 95%,and the removal efficiency of Si,Fe,Ni,and Pb can reach over 85%.Ultimately,the amount of Sn and Sb impurities is reduced to 2.0 and 4.1μg/kg,respectively,and that of most impurities,including Fe,Ni,Pb,and Bi,is reduced to levels below the instrumental detection limit.The average impurity removal efficiency is 90.9%,and the indium purity reaches 7N9.展开更多
Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints...Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints were investigated.Besides,the joint's interface microstructure,composition,and phases were analyzed.Results show that the AgCuInTi filler metal exerts a good wetting effect to the surface of cemented carbide and steel.With the increase in brazing temperature,the wetting angle decreases and the spreading area increases.The suitable temperature for vacuum brazing of PDC cutters is 770℃,and the maximum shear strength is 228 MPa at this temperature.展开更多
In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,t...In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.展开更多
Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintill...Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintillation performance is challenging.Herein,we report an effective way to prepare high-quality scintillation films of two synthesized Cu(Ⅰ)clusters through vacuum evaporation deposition.The developed Cu(Ⅰ)clusters with rigid molecular structures show excellent scintillation performance with a high light yield of up to 19356.7 photons/MeV and a low detection limit of 158 nGy/s.The scintillation film based on the Cu(Ⅰ)clusters made by vacuum evaporation deposition is highly uniform with a small surface roughness value of 1.04 nm,which can be applied to X-ray imaging for various objects.These results not only provide important guidance to develop high-performance organic-inorganic hybrid scintillators,but also pave a straightforward way to prepare non-doped scintillation screens for remarkable X-ray imaging applications.展开更多
We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisti...We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisticated techniques to realize nanoscale preparation of high-quality epitaxial oxide thin films.On the other hand,electrochemistry is a simple,very sensitive,and non-destructive analysis technique for solid-liquid interfaces.To ensure the reproducibility in experiment of the interfaces of such epitaxial oxide films,as well as bulk oxide single-crystals,with IL,we employ a home-built PLD-electrochemical(EC)system with IL as an electrolyte.The system allows one to perform all-in-vacuum experiments during the preparation of well-defined oxide electrode surfaces to their electrochemical analyses.The topics include electrochemical evaluations of the oxide’s own properties,such as carrier density and relative permittivity,and the interfacial properties of oxides in contact with IL,such as flat band potential and electric double layer(EDL)capacitance,ending with future perspectives in all-solid-state electrochemistry.展开更多
AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the...AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the interface was investigated.Moreover,the interface bonding mechanisms of the AZ31/Al/Ta composites during the VHCB process were explored.The results demonstrate that as the VHCB temperature increases,the phase composition of the interface between Mg and Al changes from the Mg-Al brittle intermetallic compounds(Al_(12)Mg_(17)and Al_(3)Mg_(2))to the Al-Mg solid solution.Meanwhile,the width of the Al/Ta interface diffusion layer at 450℃increases compared to that at 400℃.The shear strengths are 24 and 46 MPa at 400 and 450℃,respectively.The interfacial bonding mechanism of AZ31/Al/Ta composites involves the coexistence of diffusion and mechanical meshing.Avoiding the formation of brittle phases at the interface can significantly improve interfacial bonding strength.展开更多
Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output ...Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output of primary magnesium accounting for>80%of the world’s total annual output.The smelting process represented by the Pidgeon process plays the leading role in China because of its simple process flow and equipment and the flexibility of the production scale.However,the Pidgeon process always has the problems of low utilization of reduction heat,a short lifetime of the reduction tank,a high cost of the reduction furnace,and a discontinuous production process.Therefore,how to produce magnesium in a clean,efficient and continuous manner has been the focus of industry development research.In this work,from the perspective of the preparation of magnesium by thermal reduction,the production of high-purity magnesium,and the recycling of waste magnesium alloys,the research status of magnesium preparation by direct vacuum and relative vacuum processes was reviewed,including the reduction mechanism,migration and condensation patterns and production efficiency of magnesium.The effects of the reducing agent,reduction temperature,holding time and other factors on the preparation of magnesium were emphasized.Finally,by comparing the production processes of magnesium by direct vacuum and relative vacuum methods,the advantages and disadvantages of the two methods for the preparation of magnesium were mainly discussed,and the future development of magnesium was proposed.展开更多
基金Yunnan Fundamental Research Project,China(No.202201BE070001-056)。
文摘The volatilization characteristics and kinetic mechanisms of arsenic were investigated in the temperature range of 623−773 K and pressure ranges of 10−10000 Pa.The experimental results reveal that the evaporation rate increases with increasing temperature and decreasing pressure.Surface reaction control dominates at low pressures(<100 Pa),whereas diffusion control dominates at high pressures(>5000 Pa).The evaporation behavior is successfully described by an Arrhenius-type model for temperature dependence and Logistic model for pressure dependence.Key kinetic parameters,including the critical pressure,maximum evaporation rate and evaporation coefficient,were calculated.The evaporation coefficient varies between 0.010 and 0.223,and the critical pressures vary between 281 and 478 Pa with temperature.
基金supported by the National Natural Science Foundation of China(Nos.52175206,52205187,52130509)the Science and Technology Planning Project of Guizhou Province,China(No.ZK[2022]013)。
文摘The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.
基金funding support from the National Natural Science Foundation of China(Grant Nos.42441804,42403043,42273042,42303041,and U24A2008)Youth Innovation Promotion Association CAS awards+5 种基金"From 0 to 1"Original Exploration Cultivation Project,Institute of Geochemistry,Chinese Academy of Sciences(Grant No.DHSZZ2023.3)Bureau of Frontier Sciences and Basic Research,CAS,(Grant No.QYJ-2025-0103)Guizhou Provincial Foundation for Excellent Scholars Program(Grant No.GCC[2023]088)Provincial Key Research and Development(R&D)Plan Projects of Heilongjiang(Grant No.2024ZXDXB52)The Innovation and Development Fund of Science and Technology of Institute of Geochemistry,Chinese Academy of SciencesGuizhou Province Basic Research Program Project(QKHJC-ZK[2023]-General 473)。
文摘Nanophase iron particles(np-Fe^(0))have multiple formation mechanisms in lunar soil,which are mostly related to meteorite and micro meteorite impacts.Thermal modification of the impact is critical.Metal oxides have unique chemical and physical properties that allow np-Fe^(0) to form at a lower initial reaction temperature.Through the insitu heating experiment of ilmenite in the Chang'e-5 sample,it was found that ilmenite can form np-Fe^(0) at 400℃under high vacuum(10-6 Pa).This fills in the missing information on the lowest measured temperature at which ilmenite forms np-Fe^(0).At 400-800℃,only np-Fe^(0) and vesicles were formed without new Ti-rich minerals.At the same time,thermodynamic calculations showed that decomposition of ilmenite occurs in two stages.The experiments correspond to the initial stage of ilmenite thermal decomposition under high vacuum.The study explains the thermal decomposition reaction of ilmenite in a vacuum environment,provides a reference for the minimum measured temperature required for the formation of np-Fe^(0),and further improves the formation mechanism of np-Fe^(0).
基金supported by the National Youth Top-notch Talent Support Program of China(Grant No.00389335)the National Natural Science Foundation of China(Grant No.52378392)the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province(Grant No.00387088).
文摘Estimating the properties of foam-conditioned clay soils is important for both conditioning and recycling goals in earth pressure balance(EPB)shield tunneling.In this study,the vacuum dewatering behaviors of foam-conditioned clay soils were investigated,with their potential use as an alternative means to assess foam optimization being examined.A series of laboratory and fieldtests was conducted,including vacuum dewatering tests that considered the effects of filtrationtime and pressure,vane shear tests,and improved cone pullout tests under different gravimetric water content(w)and foam injection ratio(FIR)conditions.It was found that the filtrate loss(FL),which characterizes dewaterability,was increased by extended vacuum filtrationtime and elevated pressure.While increases in w and FIR enhanced FL,reductions were observed in the undrained shear strength(cu),tangential adhesion stress(Fs),and normal adhesion stress(Fn).Furthermore,a linear decrease in FL with increasing mechanical indices(cu,Fs,and Fn)was demonstrated by both laboratory and fielddata fittingresults,regardless of w,FIR,and dewatering conditions.This study provides novel insights into the understanding of vacuum dewatering mechanisms in foam-conditioned clay soils,while a simple approach is proposed for evaluating foam conditioning effectiveness in EPB shield tunneling applications.
基金supported by the National Natural Science Foundation of China (Grant Nos.U23A6018,42362034)the Applied Basic Research Foundation of Yunnan Province,China (Grant No.202401AS070068)。
文摘The construction of lunar bases represents a crucial goal for long-term human residence on the Moon and future deep-space exploration. Vacuum sintering of lunar regolith for in-situ resource utilization(ISRU) is considered one of the most feasible strategies for early lunar infrastructure development. However, the extreme temperature fluctuations on the lunar surface pose potential threats to the structural stability of sintered regolith materials. To investigate the mechanical deterioration and damage mechanism of vacuum-sintered lunar regolith under extreme cryogenic-thermal cycling, lunar regolith simulants are used to fabricate specimens through vacuum sintering. A series of cryogenic-thermal cycling tests is designed, combined with uniaxial compression and X-ray CT scanning, to systematically analyze their macro-micro responses. The results show that with increasing extreme cryogenic-thermal cycles, the stress-strain curves evolve from typical brittle failure to quasiductile behavior, with uniaxial compressive strength and elastic modulus decreasing by approximately 33.86% and 61.98%, respectively. CT analyses reveal that the pore structure transforms from isolated pores to connected networks, with the pore volume fraction increasing from 13.33% to 22.64%, and the fractal dimension increases from 2.465 to 2.544, and stabilizes after multiple cycles. A significant negative correlation(R^(2)> 0.96) exists between pore structural complexity and mechanical performance. Based on these findings, a thermal fatigue damage mechanism dominated by thermal stress concentration due to mismatched thermal expansion coefficients among mineral phases is proposed. This study provides scientific insights for the design, durability evaluation, and ISRU-based construction of lunar surface infrastructure.
基金National MCF Energy R&D Program(2019YFE03100400)。
文摘Ag-Cu-In-Ti low-temperature filler was used to braze the diamond and copper,and the effects of brazing temperature and soaking time on the microstructure and mechanical properties of the joints were investigated.In addition,the joint formation mechanism was discussed,and the correlation between joint microstructure and mechanical performance was established.Results show that adding appropriate amount of In into the filler can significantly reduce the filler melting point and enhance the wettability of filler on diamond.When the brazing temperature is 750°C and the soaking time is 10 min,a uniformly dense braze seam with excellent metallurgical bonding can be obtained,and its average joint shear strength reaches 322 MPa.The lower brazing temperature can mitigate the risk of diamond graphitization and also reduce the residual stresses during joining.
文摘Colonoscopy represents a safe procedure that is widely used in medical practice either to diagnose or treat various gastrointestinal diseases.During the last few years,the incidence rate of perforations in colonoscopic procedures has increased,especially in therapeutic colonoscopies.The recent advancements in endoscopic techniques and gastrointestinal tumoral resection procedures such as endoscopic mucosal resection,endoscopic full-thickness resection,and endoscopic submucosal dissection(ESD)could be a risk factor for this increased risk.The incidence rate of mortality of serious colonoscopic perforations is 7.1%.The management plan for these perforations starts with conservative treatment in mild cases,endoscopic closure,and surgical management in severe cases.Recently,endoluminal vacuum therapy was found to be effective in the management of colorectal perforations and this has been reported in multiple case reports.This editorial provides an overview of the current guidelines for the management of iatrogenic colorectal perforations.These insights are from the perspectives of endoscopists and gastroenterologists.We also present a management algorithm based on the guidelines of the European Society of Gastrointestinal Endoscopy,the American Gastroenterological Association,and the World Society of Emergency Surgery.We also discussed in brief the use of endoluminal vacuum therapy in colorectal perforations.
基金Funded by the National Natural Science Foundation of China(No.52472012)Opening Project of State Silica-Based Materials Laboratory of Anhui Province(No.2022KF11)the Research and Development of Glass Powder for Laser Sealing and Its Sealing Technology(No.K24556)。
文摘The low-melting glass of Bi2O_(3)-B2O_(3)-SiO_(2)(BiBSi)system was used for the first time for laser sealing of vacuum glazing.Under the condition of constant boron content,how the structure and properties vary with Bi/Si ratio in low-melting glass was investigated.In addition,the relationships between laser power,low-melting glass solder with different Bi/Si ratios and laser sealing shear strength were revealed.The results show that a decrease in the Bi/Si ratio can cause a contraction of the glass network of the low-melting glass,leading to an increase of its characteristic temperature and a decrease of its coefficient of thermal expansion.During laser sealing,the copper ions in the low-melting glass play an endothermic role.A change in the Bi/Si ratio will affect the valence state transition of the copper ions in the low-melting glass.The absorbance of the low-melting glass does not follow the expected correlation with the Bi/Si ratio,but shows a linear correlation with the content of divalent copper ions.The greater the concentration of divalent copper ions,the greater the absorbance of the low-melting glass,and the lower the laser power required for laser sealing.The shear strength of the low melting glass solder after laser sealing was tested,and it was found that the maximum shear strength of Z1 glass sample was the highest up to 2.67 MPa.
文摘In recent years,there has been a growing global demand for carbon neutrality and energy efficiency,which are expected to become long-term trends.In the field of architecture,an effective approach to achieve this is to reduce heat loss in buildings.Vacuum insulation panels(VIPs),a type of high-performance insulation material,have been increasingly utilised in the construction industry and have played an increa-singly important role as their performance and manufacturing processes continue to improve.This paper provides a review of the factors affecting the thermal conductivity of VIPs and presents a detailed overview of the research progress on core materials,barrier films,and getters.The current research status of VIPs is summarised,including their thermal conductivity,service life,and thermal bridging effects,as well as their applications in the field of architecture.This review aims to provide a comprehensive understanding for relevant practitioners on the factors influencing the thermal conductivity of VIPs,and based on which,measures can be taken to produce VIPs with lower thermal conductivity and longer service life.
文摘Magnesium(Mg)alloys are widely used lightweight structural materials for automobiles and help reduce carbon emissions.However,their use increases the production of Mg alloy scrap,which is recycled at a much lower rate than aluminum,and its greater complexity poses challenges to existing recycling processes.Although vacuum distillation can be used to recycle Mg alloy scrap,this requires optimizing and maximizing metal recirculation,but there has been no thermodynamic analysis of this process.In this study,the feasibility and controllability of separating inclusions and 23 metal impurities were evaluated,and their distribution and removal limits were quantified.Thermodynamic analyses and experimental results showed that inclusions and impurity metals of separation coefficient lgβ_(i)≤-5,including Cu,Fe,Co,and Ni below 0.001 ppm,could be removed from the matrix.All Zn entered the recycled Mg,while impurities with-1<lgβ_(i)<-5 such as Li,Ca,and Mn severely affected the purity of the recycled Mg during the later stage of distillation.Therefore,an optimization strategy for vacuum distillation recycling:lower temperatures and higher system pressures for Zn separation in the early stage,and the early termination of the recovery process in the later stage or a continuous supply of raw melt can also prevent contamination during recycling.The alloying elements Al and Zn in Mg alloy scrap can be further recovered and purified by vacuum distillation when economically feasible,to maximize the recycling of metal resources.
基金supported by the China Postdoctoral Science Foundation(No.2023T160088)the Youth Fund of the National Natural Science Foundation of China(No.52304324).
文摘Magnesium and magnesium alloys,serving as crucial lightweight structural materials and hydrogen storage elements,find extensive applications in space technology,aviation,automotive,and magnesium-based hydrogen industries.The global production of primary magnesium has reached approximately 1.2 million tons per year,with anticipated diversification in future applications and significant market demand.Nevertheless,approximately 80%of the world’s primary magnesium is still manufactured through the Pidgeon process,grappling with formidable issues including high energy consumption,massive carbon emission,significant resource depletion,and environmental pollution.The implementation of the relative vacuum method shows potential in breaking through technological challenges in the Pidgeon process,facilitating clean,low-carbon continuous magnesium smelting.This paper begins by introducing the principles of the relative vacuum method.Subsequently,it elucidates various innovative process routes,including relative vacuum ferrosilicon reduction,aluminum thermal reduction co-production of spinel,and aluminum thermal reduction co-production of calcium aluminate.Finally,and thermodynamic foundations of the relative vacuum,a quantitative analysis of the material,energy flows,carbon emission,and production cost for several new processes is conducted,comparing and analyzing them against the Pidgeon process.The study findings reveal that,with identical raw materials,the relative vacuum silicon thermal reduction process significantly decreases raw material consumption,energy consumption,and carbon dioxide emissions by 15.86%,30.89%,and 26.27%,respectively,compared to the Pidgeon process.The relative vacuum process,using magnesite as the raw material and aluminum as the reducing agent,has the lowest magnesium-to-feed ratio,at only 3.385.Additionally,its energy consumption and carbon dioxide emissions are the lowest,at 1.817 tce/t Mg and 7.782 t CO_(2)/t Mg,respectively.The energy consumption and carbon emissions of the relative vacuum magnesium smelting process co-producing calcium aluminate(12CaO·7Al_(2)O_(3),3CaO·Al_(2)O_(3),and CaO·Al_(2)O_(3))are highly correlated with the consumption of dolomite in the raw materials.When the reduction temperature is around 1473.15 K,the critical volume fraction of magnesium vapor for different processes varies within the range of 5%–40%.Production cost analysis shows that the relative vacuum primary magnesium smelting process has significant economic benefits.This paper offers essential data support and theoretical guidance for achieving energy efficiency,carbon reduction in magnesium smelting,and the industrial adoption of innovative processes.
基金Supported by Natural Science Foundation of Shandong Province,No.ZR2023MH331.
文摘BACKGROUND A case study of multiple distinct levels of skipped thoracolumbar spine infection was reported in which 13 successful vacuum sealing drainage(VSD)surgeries were treated.CASE SUMMARY The patient underwent a total of 13 procedures within our medical facility,including five performed under local anesthesia and eight performed under general anesthesia.The source of the ailment was ultimately identified as Enterobacter cloacae.After the last procedure,the patient's symptoms were alleviated,and the recovery process was satisfactory.Three months post-operation,the Japanese Orthopaedic Association scores had improved to 100%.Imageological examination revealed a satisfactory position of internal fixation,and the abnormal signals in the vertebral body and intervertebral space had been eliminated when compared to the pre-operative results.CONCLUSION The study demonstrates that the extreme lateral approach debridement combined with multiple VSD operations is a secure and successful method of treatment for recurrent spinal infection,providing an alternative to traditional surgery.
基金supported by the National Special Fund for the Development of Major Research Equipment and Instrument(No.2020YFF01014503)the Young Taishan Scholars(No.tsqn201909039)the College 20 Project fromJi Nan Science&Technology Bureau(No.2021GXRC058).
文摘Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of methyl iodide and humidity interference are two major issues of the vacuum ultraviolet(VUV)lamp initiated CIMS for on-line gaseous formic and acetic acids analysis.In this work,we present a new CIMS based on VUV lamp,and the ion-molecular reactor is separated into photoionization and chemical ionization zones by a reducer electrode.Acetone was added to the photoionization zone,and the VUV photoionization acetone provided low-energy electrons for methyl iodide to generate I−,and the addition of acetone reduced the amount of methyl iodide by 2/3.In the chemical ionization zone,a headspace vial containing ultrapure water was added for humidity calibration,and the vial changes the sensitivity as a function of humidity from ambiguity to well linear correlation(R2>0.95).With humidity calibration,the CIMS can quantitatively measure formic and acetic acids in the humidity range of 0%-88%RH.In this mode,limits of detection of 10 and 50 pptv are obtained for formic and acetic acids,respectively.And the relative standard deviation(RSD)of quantitation stability for 6 days were less than 10.5%.This CIMS was successfully used to determine the formic and acetic acids in the underground parking and ambient environment of the Shandong University campus(Qingdao,China).In addition,we developed a simple model based formic acid concentration to assess vehicular emissions.
基金National Key Research and Development Program of China(2023YFC2907904)National Natural Science Foundation of China(52374364)。
文摘High-purity indium finds extensive application in the aerospace,electronics,medical,energy,and national defense sectors.Its purity and impurity contents significantly influence its performance in these applications.High-purity indium was prepared by combining zone refining with vacuum distillation.Results show that the average removal efficiency of impurity Sb can approach 95%,while the removal efficiency of impurities Sn and Bi can reach over 95%,and the removal efficiency of Si,Fe,Ni,and Pb can reach over 85%.Ultimately,the amount of Sn and Sb impurities is reduced to 2.0 and 4.1μg/kg,respectively,and that of most impurities,including Fe,Ni,Pb,and Bi,is reduced to levels below the instrumental detection limit.The average impurity removal efficiency is 90.9%,and the indium purity reaches 7N9.
基金National Natural Science Foundation of China(52075551,52271045,51975469)Supported by State Key Laboratory of Advanced Welding and Joining(AWJ-22M09)+2 种基金Supported by State Key Laboratory of Advanced Brazing Filler Metals and Technology(SKLABFMT201904)Key Research and Development Program of Shaanxi Province(2022GY-224)Innovative Talent Recommendation Program(Youth Science and Technology New Star Project)of Shaanxi Province(2020 KJX X-045)。
文摘Polycrystalline diamond compact(PDC)cutters and carbon steel were brazed by AgCuInTi filler metal under vacuum condition.The effects of brazing temperature on the wettability of base metal and shear strength of joints were investigated.Besides,the joint's interface microstructure,composition,and phases were analyzed.Results show that the AgCuInTi filler metal exerts a good wetting effect to the surface of cemented carbide and steel.With the increase in brazing temperature,the wetting angle decreases and the spreading area increases.The suitable temperature for vacuum brazing of PDC cutters is 770℃,and the maximum shear strength is 228 MPa at this temperature.
文摘In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.
文摘Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintillation performance is challenging.Herein,we report an effective way to prepare high-quality scintillation films of two synthesized Cu(Ⅰ)clusters through vacuum evaporation deposition.The developed Cu(Ⅰ)clusters with rigid molecular structures show excellent scintillation performance with a high light yield of up to 19356.7 photons/MeV and a low detection limit of 158 nGy/s.The scintillation film based on the Cu(Ⅰ)clusters made by vacuum evaporation deposition is highly uniform with a small surface roughness value of 1.04 nm,which can be applied to X-ray imaging for various objects.These results not only provide important guidance to develop high-performance organic-inorganic hybrid scintillators,but also pave a straightforward way to prepare non-doped scintillation screens for remarkable X-ray imaging applications.
文摘We introduce our state-of-the art of“vacuum consistent electrochemistry”to an investigation of the interfaces between oxides and ionic liquid(IL).Pulsed laser deposition(PLD)has been one of the powerful and sophisticated techniques to realize nanoscale preparation of high-quality epitaxial oxide thin films.On the other hand,electrochemistry is a simple,very sensitive,and non-destructive analysis technique for solid-liquid interfaces.To ensure the reproducibility in experiment of the interfaces of such epitaxial oxide films,as well as bulk oxide single-crystals,with IL,we employ a home-built PLD-electrochemical(EC)system with IL as an electrolyte.The system allows one to perform all-in-vacuum experiments during the preparation of well-defined oxide electrode surfaces to their electrochemical analyses.The topics include electrochemical evaluations of the oxide’s own properties,such as carrier density and relative permittivity,and the interfacial properties of oxides in contact with IL,such as flat band potential and electric double layer(EDL)capacitance,ending with future perspectives in all-solid-state electrochemistry.
基金National Natural Science Foundation of China(52275308,52301146)Fundamental Research Funds for the Central Universities(2023JG007)Supported by Shi Changxu Innovation Center for Advanced Materials(SCXKFJJ202207)。
文摘AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the interface was investigated.Moreover,the interface bonding mechanisms of the AZ31/Al/Ta composites during the VHCB process were explored.The results demonstrate that as the VHCB temperature increases,the phase composition of the interface between Mg and Al changes from the Mg-Al brittle intermetallic compounds(Al_(12)Mg_(17)and Al_(3)Mg_(2))to the Al-Mg solid solution.Meanwhile,the width of the Al/Ta interface diffusion layer at 450℃increases compared to that at 400℃.The shear strengths are 24 and 46 MPa at 400 and 450℃,respectively.The interfacial bonding mechanism of AZ31/Al/Ta composites involves the coexistence of diffusion and mechanical meshing.Avoiding the formation of brittle phases at the interface can significantly improve interfacial bonding strength.
基金the combined funding from the National Natural Science Foundation of China(U1908225,U1702253,U1508217)。
文摘Magnesium plays an important role in biomedicine,new energy vehicles,aerospace and other fields because of its excellent physical and chemical properties.China is a major source of magnesium worldwide,with the output of primary magnesium accounting for>80%of the world’s total annual output.The smelting process represented by the Pidgeon process plays the leading role in China because of its simple process flow and equipment and the flexibility of the production scale.However,the Pidgeon process always has the problems of low utilization of reduction heat,a short lifetime of the reduction tank,a high cost of the reduction furnace,and a discontinuous production process.Therefore,how to produce magnesium in a clean,efficient and continuous manner has been the focus of industry development research.In this work,from the perspective of the preparation of magnesium by thermal reduction,the production of high-purity magnesium,and the recycling of waste magnesium alloys,the research status of magnesium preparation by direct vacuum and relative vacuum processes was reviewed,including the reduction mechanism,migration and condensation patterns and production efficiency of magnesium.The effects of the reducing agent,reduction temperature,holding time and other factors on the preparation of magnesium were emphasized.Finally,by comparing the production processes of magnesium by direct vacuum and relative vacuum methods,the advantages and disadvantages of the two methods for the preparation of magnesium were mainly discussed,and the future development of magnesium was proposed.
