Formation of volatile nickel carbonyls with CO in catalytic reaction is one of the mechanisms of catalyst deactivation. CO is one of the most popular probe molecules to study the surface properties in model catalysis....Formation of volatile nickel carbonyls with CO in catalytic reaction is one of the mechanisms of catalyst deactivation. CO is one of the most popular probe molecules to study the surface properties in model catalysis. Under ultra-high vacuum (UHV) conditions, the problem of nickel carbonyl impurity almost does not exist in the case that a high purity of CO is used directly. While in the near ambient pressure (NAP) range, nickel carbonyl is easily found on the surface by passing through the Ni containing tubes. Here, the NAP techniques such as NAP-X-ray photoelectron spectroscopy and NAP-scanning tunneling microscopy are used to study the adsorption of nickel carbonyl contaminated CO gas on Cu(111) surface in UHV and NAP conditions. By controlling the pressure of contaminated CO, the Ni-Cu bimetallic catalyst can form on Cu(111) surface. Furthermore, we investigate the process of CO adsorption and dissociation on the formed Ni-Cu bi-metal surface, and several high-pressure phases of CO structures are reported. This work contributes to understanding the interaction of nickel carbonyl with Cu(111) at room temperature, and reminds the consideration of CO molecules contaminated by nickel carbonyl especially in the NAP range study.展开更多
A simple,fast and cost-effective method for monolithic carbon aerogels(CAs) preparation was proposed through sol-gel polycondensation of resorcinol with fo rmaldehyde in a basic aqueous solution followed by ambient pr...A simple,fast and cost-effective method for monolithic carbon aerogels(CAs) preparation was proposed through sol-gel polycondensation of resorcinol with fo rmaldehyde in a basic aqueous solution followed by ambient pressure drying without solvent exchange,and carbonization.The microstructure and network strength of CAs were tailored by adju sting the catalyst concentration([resorcinol]/[sodium carbonate] in the range of 300-2000),water content([deionized water]/[resorcinol] equals to 17 and 24,respectively),and gelation temperature(Tgel in the range of 30-90℃).Resultantly,the CAs with a wide range of density(0.30-1.13 g/cm3),high specific surface area(465-616 m2/g),high compressive strength(6.5-147.4 MPa)and low thermal conductivity(0.065-0.120 W·m-1 K-1) were obtained in this work.Moreover,the largesized CAs(100×100×20 mm3) can also be prepared by this method since the formed robust skeleton network can resist shrinkage/collapse of pore structure and prevent cracking during drying.The improved mechanical strength and monolithic forming abilities could be mainly attributed to the uniform arrangement of carbon particles and pores,fine particle size,abundant network structure and enhanced particle neck.展开更多
Silica aerogels were prepared by sol-gel technique from industrial silicon derivatives （polyethoxydisiloxanes, E40）, followed by silylation and drying under ambient pressure. The specific surface area, pore size dis...Silica aerogels were prepared by sol-gel technique from industrial silicon derivatives （polyethoxydisiloxanes, E40）, followed by silylation and drying under ambient pressure. The specific surface area, pore size distribution and thermal conductivity of the silica aerogels were investigated and the results showed that the diameter of the silica particles is about 6 nm and the average pore size of the silica aerogels is 14.7 nm. The specific surface area of which is about 1000 m^2.g^-1 and the thermal conductivity is about 0.014 wm^-l.K^-1 at room temperature and pressure of 1.01×10^5 Pa. The Si-CH3 groups were also detected on the internal surface of the silica aerogels, which show hydrophobic. Silica aerogels derived by this technique is low cost and have wide applications.展开更多
Three-dimensional graphene-based aerogels have promising applications in oil adsorption and environmental restoration.However,current research of graphene-based aerogels is often hindered by high preparation cost,poor...Three-dimensional graphene-based aerogels have promising applications in oil adsorption and environmental restoration.However,current research of graphene-based aerogels is often hindered by high preparation cost,poor mechanical properties and low recycling efficiency.Here,superelastic graphene aerogel(SGA)was prepared through one-step freezing and twice hydrothermal reduction followed by drying under ambient pressure.The simple atmospheric drying provides a possibility for large-scale preparation of high performance graphene-based aerogels.The prepared SGA not only has the ability of highly repeatable compression rebound,but also exhibits excellent oil adsorption performance.And the overall performance of SGA is better than most of graphenebased aerogels prepared by freeze drying.After the SGA was cyclically compressed with 70%strain for 300 times,it can return to the original shape and height substantially.SGA retained about 90%of the initial adsorption capacity after 50 cycles of adsorption and compression regeneration for cyclohexane.展开更多
The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different a...The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.展开更多
In this paper, the compositions in a laser absorption region can be determined from the experiment of laser impulse coupling. When the ambient pressure varies from 9325 to 33325Pa, the compositions are vapour and plas...In this paper, the compositions in a laser absorption region can be determined from the experiment of laser impulse coupling. When the ambient pressure varies from 9325 to 33325Pa, the compositions are vapour and plasma; while from 35325 to 101325Pa, they are ambient air and plasma. By analysing the relation between the degree of compression and the ambient pressure, the compositions can be determined and the variation of plasma can be explained.展开更多
Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a...Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a vacuum has been investigated by high-speed imaging,the underlying mechanisms governing the heat transfer and molten flow are still not well understood.Herein,we first developed a mesoscopic model of SLM under variable ambient pressure based on our recent laser-welding studies.We simulated the transport phenomena of SLM 316L stainless steel powders under atmospheric and 100 Pa ambient pressure.For typical process parameters(laser power:200W;scanning speed:2m∙s^(-1);powder diameter:27 lm),the average surface temperature of the cavity approached 2800 K under atmospheric pressure,while it came close to 2300 K under 100 Pa pressure.More vigorous fluid flow(average speed:4m∙s^(-1))was observed under 100 Pa ambient pressure,because the pressure difference between the evaporation-induced surface pressure and the ambient pressure was relatively larger and drives the flow under lower pressure.It was also shown that there are periodical ripple flows(period:14ls)affecting the surface roughness of the as-printed track.Moreover,the molten flow was shown to be laminar because the Reynolds number is less than 400 and is far below the critical value of turbulence;thus,the viscous dissipation is significant.It was demonstrated that under a vacuum or lower ambient pressure,the ripple flow can be dissipated more easily by the viscous effect because the trajectory length of the ripple is longer;thus,the surface quality of the tracks is improved.To summarize,our model elucidates the physical mechanisms of the interesting transport phenomena that have been observed in independent experimental studies of the SLM process under variable ambient pressure,which could be a powerful tool for optimizing the SLM process in the future.展开更多
Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low po...Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions.Gasoline direct injection(GDI)has been recognized as one of the most effective ways to improve fuel atomization.As a special direct injection method,the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure.This injection method has excellent application potential and advantages for high performance and lightweight engines.In this study,the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa.External macro characteristics of spray were obtained using high speed backlit imaging.Phase Doppler particle analyzer(PDPA)was utilized to study the microcosmic spray characteristics.The results show that under the flash boiling condition,the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards.The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width.The sauter mean diameter(SMD)of flash boiling condition can be reduced to 5μm compared to the level close to 10μm in the non-flash boiling condition.展开更多
A novel scale-up ambient pressure synthetic strategy for the preparation of imine-based covalent organic frameworks（COFs） was proposed through dynamic imine exchange reaction mechanism. The obtained COFs exhibited g...A novel scale-up ambient pressure synthetic strategy for the preparation of imine-based covalent organic frameworks（COFs） was proposed through dynamic imine exchange reaction mechanism. The obtained COFs exhibited good crystallinity and much higher porosity comparable to their solvothermally synthesized counterparts. Moreover, under ambient pressure, the COF nanofibers could readily grow on the surface of polyimide films, and the resulted nanocomposite film showed an interesting colorimetric acid-responsive behavior.展开更多
An ambient pressure-induced calcination process was proposed to prepare g-C3 N4 with different structures.The porcelain boat with designed porosity is used to control the ambient pressure to change the diffusion behav...An ambient pressure-induced calcination process was proposed to prepare g-C3 N4 with different structures.The porcelain boat with designed porosity is used to control the ambient pressure to change the diffusion behavior of the reaction molecules,thereby controlling the layer structure and rich pyridinic N content of g-C3 N4,thus renders superior lithium storage performance.展开更多
In order to solve the problem of single arc plasma actuator's failure to suppress the boundary layer separation, the effectiveness of the array surface arc plasma actuator to enhance the excitation intensity is ve...In order to solve the problem of single arc plasma actuator's failure to suppress the boundary layer separation, the effectiveness of the array surface arc plasma actuator to enhance the excitation intensity is verified by experiment. In this study, an electrical parameter measurement system and high-speed schlieren technology were adopted to delve into the electrical, flow field, and excitation characteristics of the high-energy array surface arc plasma actuator under low ambient pressure. The high-energy array surface arc discharge released considerable heat rapidly;as a result, two characteristic structures were generated, i.e., the precursor shock wave and thermal deposition area. The duration increased with the increase in environmental pressure. The lower the pressure, the wider the thermal deposition area's influence range. The precursor shock wave exhibited a higher propagation speed at the initial phase of discharge;it tended to decay over time and finally remained at 340 m/s. The lower the environmental pressure, the higher the speed would be at the initial phase. High-energy array surface arc plasma actuator can be employed to achieve effective high-speed aircraft flow control.展开更多
Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas...Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas and adjust pore size distribution. The synthesis process was optimized, and the morphology, structure, adsorption properties and electrochemical behavior of different samples were characterized. The CO2-activated samples achieved a high specific capacitance of 129.2 F/g in 6 M KOH electrolytes at the current density of 1 m A/cm^2 within the voltage range of 0-0.8 V. The optimized activation temperature and duration were determined to be 950 ℃ and 4 h, respectively.展开更多
X-ray photoelectron spectroscopy(XPS)is a crucial surface analysis technique that has become a key tool in the study of heterogeneous catalysis.Detecting surface chemistry under conditions that closely mimic actual in...X-ray photoelectron spectroscopy(XPS)is a crucial surface analysis technique that has become a key tool in the study of heterogeneous catalysis.Detecting surface chemistry under conditions that closely mimic actual industrial catalytic processes is essential for understanding the mechanisms involved.In the past decade,near ambient pressure X-ray photoelectron spectroscopy(NAP-XPS)has been increasingly utilized to study the surface chemistry of catalysts during heterogeneous catalytic processes,offering insights into structure-performance correlations.This review begins with a brief overview of NAP-XPS instrumentation.Next,we discuss the application of NAP-XPS in the study of thermal catalysis reactions,followed by a summary of the research on catalyst restructuring under reaction conditions.Additionally,we address the challenges and future perspectives for the development and application of NAP-XPS.Catalysis is inherently dynamic,requiring an understanding of the real-time behavior of catalysts under varying conditions.Therefore,future improvements in the ability to probe reaction intermediates with higher spatial and temporal resolution under conditions that closely mimic industrial environments are needed.展开更多
Elucidation of a physicochemical process on nanocatalysts,especially under continuously evolving conditions,is often heavily tool-driven because of technical challenges.Recently,ambient pressure X-ray photoelectron sp...Elucidation of a physicochemical process on nanocatalysts,especially under continuously evolving conditions,is often heavily tool-driven because of technical challenges.Recently,ambient pressure X-ray photoelectron spectroscopy(APXPS)emerges as an emerging photon-in-electron-out technique in in-situ/operando analysis by bridging the pressure-gap between conventional ultra-high vacuum(UHV)and near ambient or even close to operating conditions,rendering the advancement of XPS from a UHV-based technique to a versatile and powerful tool that enables the specific probe of numerous events taking place at the gas–solid,liquid–solid and liquid–gas nanoscale interfaces which are critical to nanocatalysis research.For example,APXPS probes information on catalytically active phase and reaction kinetics in nanocatalytic processes;details inside the electric double-layer at an electrolyte/electrode interface can now be accessed;more efficient nanocatalyst design can be achieved and energy transfer venues can be optimized.Here,we aim to critically review the recent advances in instrumentation and the probe of the gas–solid,liquid–solid,and gas–liquid nanoscale interfaces using APXPS-based methodologies,followed by putting forward an outlook of development of APXPS as a rising in-situ/operando analytical means in surface science,nanocatalysis,nanoscience materials science.展开更多
The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of ...The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of the water hammer while the liquid jet impacting onto the boundary are found to increase nonlinearly with increasing ambient pressure. The collapse time and the formation time of the liquid jet are found to decrease nonlinearly with increasing ambient pressure. The ratios of the jet formation time to the collapse time, and the displacement of the bubble center to the maximal radius while the jet formation stay invariant when ambient pressure changes. These ratios are independent of ambient pressure.展开更多
Here we present an economical ambient pressure drying method of preparing monolithic silica aerogels from methyltrimethoxysilane precursor while using sodium bicarbonate solution as the exchanging solvent.We prepared ...Here we present an economical ambient pressure drying method of preparing monolithic silica aerogels from methyltrimethoxysilane precursor while using sodium bicarbonate solution as the exchanging solvent.We prepared silica aerogels with a density and a specific surface area of 0.053 g·cm^(-3) and 423 m^(2)·g^(-1) respectively.The average pore diameter of silica aerogels is 23 nm as the pore specific volume is 1.11 cm^(3)·g^(-1),Further,the contact angle between water droplet and the surface of silica aerogels in specific condition can be as high as 166°,which indicates a super-hydrophobic surface of aerogels.展开更多
Atomically thin MoS2 films have attracted significant attention due to excellent electrical and optical properties.The development of device applications demands the production of large-area thin film which is still a...Atomically thin MoS2 films have attracted significant attention due to excellent electrical and optical properties.The development of device applications demands the production of large-area thin film which is still an obstacle.In this work we developed a facile method to directly grow large-area MoS2 thin film on Si O2 substrate via ambient pressure chemical vapor deposition method. The characterizations by spectroscopy and electron microscopy reveal that the as-grown MoS2 film is mainly bilayer and trilayer with high quality. Back-gate field-effect transistor based on such MoS2 thin film shows carrier mobility up to 3.4 cm2V-1s-1 and on/off ratio of 105. The large-area atomically thin MoS2 prepared in this work has the potential for wide optoelectronic and photonic device applications.展开更多
The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stab...The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stable ordered Nb-Ti compound under ambient pressure.Extensive first-principles calculations have provided insights into the electronic structure,bonding and superconducting properties of Nb_(7)Ti.The superconducting transition temperature(T_(c))for Nb_(7)Ti at ambient pressure is estimated within the framework of BCS theory to be about 17.5 K,which is significantly higher—nearly double—that of the widely utilized NbTi alloy.Furthermore,the results unveil that the high T_(c) is mainly attributed to the unique ordered lattice along with the strong electron-phonon coupling driven by interatomic interactions at mid-frequency and phonon softening induced by low-frequency Fermi surface nesting.Valuable insights are provided for the subsequent synthesis of application-oriented superconductors at low pressure.展开更多
A novel‐structured Mo‐Cu‐Fe‐O composite was successfully prepared by co‐precipitation and impregnation method.The properties of the as‐prepared samples were determined using X‐ray diffraction,temperature‐progr...A novel‐structured Mo‐Cu‐Fe‐O composite was successfully prepared by co‐precipitation and impregnation method.The properties of the as‐prepared samples were determined using X‐ray diffraction,temperature‐programmed reduction by H2,cyclic voltammetry,and temperature‐programmed desorption by O2.The results showed that Mo6+diffused into the Cu‐Fe‐O crystal lattice and then formed a new crystalline phase of CuMoO4.The Mo‐Cu‐Fe‐O catalyst had redox properties,and its surface contained active sites for oxygen adsorption.In addition,the catalytic activity of the Mo‐Cu‐Fe‐O composite was evaluated by the degradation of Cationic Red GTL,Crystal Violet,and Acid Red in catalytic wet air oxidation(CWAO)at ambient temperature and pressure.The Mo‐Cu‐Fe‐O catalyst showed excellent activity at basic conditions for the degradation of Cationic Red GTL.High removal efficiencies of91.5%and92.8%were achieved for Cationic Red GTL and Crystal Violet,respectively,in wastewater,and the efficiency remained high after seven cycles.However,almost no degradation of Acid Red occurred in the CWAO process.Furthermore,hydroxyl radicals were formed in the CWAO process,which induced the decomposition of the two cationic dyes in wastewater,and the toxicity of their effluents was decreased after degradation.The results indicate that the Mo‐Cu‐Fe‐O composite shows excellent catalytic activity for the treatment of wastewater contaminated with cationic dyes.展开更多
Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and ...Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.展开更多
基金supported by the National Natural Science Foundation of China(No.91845109)Key Laboratory of Surface Physics and Chemistry Discipline Development Fund(XKFZ201711)
文摘Formation of volatile nickel carbonyls with CO in catalytic reaction is one of the mechanisms of catalyst deactivation. CO is one of the most popular probe molecules to study the surface properties in model catalysis. Under ultra-high vacuum (UHV) conditions, the problem of nickel carbonyl impurity almost does not exist in the case that a high purity of CO is used directly. While in the near ambient pressure (NAP) range, nickel carbonyl is easily found on the surface by passing through the Ni containing tubes. Here, the NAP techniques such as NAP-X-ray photoelectron spectroscopy and NAP-scanning tunneling microscopy are used to study the adsorption of nickel carbonyl contaminated CO gas on Cu(111) surface in UHV and NAP conditions. By controlling the pressure of contaminated CO, the Ni-Cu bimetallic catalyst can form on Cu(111) surface. Furthermore, we investigate the process of CO adsorption and dissociation on the formed Ni-Cu bi-metal surface, and several high-pressure phases of CO structures are reported. This work contributes to understanding the interaction of nickel carbonyl with Cu(111) at room temperature, and reminds the consideration of CO molecules contaminated by nickel carbonyl especially in the NAP range study.
基金supported by the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation of NSFC and CASC, China Grant No. U1537204National Natural Science Foundation of China Grant No. 51802313 and 51902315+2 种基金National Science and Technology Major Project (2017-VI-0020-0093)Research Fund of Youth Innovation Promotion Association of CAS, China Grant No. 2014171National Key R&D Program of China Grant No. 2018YFF01013600。
文摘A simple,fast and cost-effective method for monolithic carbon aerogels(CAs) preparation was proposed through sol-gel polycondensation of resorcinol with fo rmaldehyde in a basic aqueous solution followed by ambient pressure drying without solvent exchange,and carbonization.The microstructure and network strength of CAs were tailored by adju sting the catalyst concentration([resorcinol]/[sodium carbonate] in the range of 300-2000),water content([deionized water]/[resorcinol] equals to 17 and 24,respectively),and gelation temperature(Tgel in the range of 30-90℃).Resultantly,the CAs with a wide range of density(0.30-1.13 g/cm3),high specific surface area(465-616 m2/g),high compressive strength(6.5-147.4 MPa)and low thermal conductivity(0.065-0.120 W·m-1 K-1) were obtained in this work.Moreover,the largesized CAs(100×100×20 mm3) can also be prepared by this method since the formed robust skeleton network can resist shrinkage/collapse of pore structure and prevent cracking during drying.The improved mechanical strength and monolithic forming abilities could be mainly attributed to the uniform arrangement of carbon particles and pores,fine particle size,abundant network structure and enhanced particle neck.
基金This work was supported by tile National Natural Science Foundation of China(Grant No.20133040,59802007,69978017)Chinese National Foundation of High Technology(2002AA842052)+2 种基金Shanghai Committee of Science and Technology(055211010,0352nm022,0352nm056)Shanghai Key Subject Programme,Shanghai Phospher Program(05QMH1413)Trans-Century Training Programme Foundation for the Talents by the State Education Commission.
文摘Silica aerogels were prepared by sol-gel technique from industrial silicon derivatives （polyethoxydisiloxanes, E40）, followed by silylation and drying under ambient pressure. The specific surface area, pore size distribution and thermal conductivity of the silica aerogels were investigated and the results showed that the diameter of the silica particles is about 6 nm and the average pore size of the silica aerogels is 14.7 nm. The specific surface area of which is about 1000 m^2.g^-1 and the thermal conductivity is about 0.014 wm^-l.K^-1 at room temperature and pressure of 1.01×10^5 Pa. The Si-CH3 groups were also detected on the internal surface of the silica aerogels, which show hydrophobic. Silica aerogels derived by this technique is low cost and have wide applications.
基金the financial support of National Natural Science Foundation of China (22078366)
文摘Three-dimensional graphene-based aerogels have promising applications in oil adsorption and environmental restoration.However,current research of graphene-based aerogels is often hindered by high preparation cost,poor mechanical properties and low recycling efficiency.Here,superelastic graphene aerogel(SGA)was prepared through one-step freezing and twice hydrothermal reduction followed by drying under ambient pressure.The simple atmospheric drying provides a possibility for large-scale preparation of high performance graphene-based aerogels.The prepared SGA not only has the ability of highly repeatable compression rebound,but also exhibits excellent oil adsorption performance.And the overall performance of SGA is better than most of graphenebased aerogels prepared by freeze drying.After the SGA was cyclically compressed with 70%strain for 300 times,it can return to the original shape and height substantially.SGA retained about 90%of the initial adsorption capacity after 50 cycles of adsorption and compression regeneration for cyclohexane.
基金Supported by the FRGS under Grant No R.J130000.7809.4F519
文摘The laser induced plasma dynamics of graphite material are investigated by optical emission spectroscopy. Abla- tion and excitation of the graphite material is performed by using an 1064nm Nd：YAG laser in different ambient pressures. Characteristics of graphite spectra as line intensity variations and signal-to-noise ratio are presented with a main focus on the influence of the ambient pressure on the interaction of laser-induced graphite plasma with an ambient environment. Atomic emission lines are utilized to investigate the dynamical behavior of plasma, such as the excitation temperature and electron density, to describe emission differences under different ambient conditions. The excitation temperature and plasma electron density are the primary factors which contribute to the differences among the atomic carbon emission at different ambient pressures. Reactions between the plasma species and ambient gas, and the total molecular number are the main factors influencing molecular carbon emis- sion. The influence of laser energy on the plasma interaction with environment is also investigated to demonstrate the dynamical behavior of carbon species so that it can be utilized to optimize plasma fluctuations.
基金Project supported by the National Science Foundation of China (Grant Nos 60578015 and 60208004)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20050288025)
文摘In this paper, the compositions in a laser absorption region can be determined from the experiment of laser impulse coupling. When the ambient pressure varies from 9325 to 33325Pa, the compositions are vapour and plasma; while from 35325 to 101325Pa, they are ambient air and plasma. By analysing the relation between the degree of compression and the ambient pressure, the compositions can be determined and the variation of plasma can be explained.
基金This research was supported by the National Science Fund for Excellent Young Scholars(52022033)the National Key Research and Development Program of China(2017YFE0100100 and 2018YFB1105300)+1 种基金was partially supported by the Government of Perm Krai(S-26/794)the Russian Foundation for Basic Research(16-48-590208).
文摘Recent reports on the selective laser melting(SLM)process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products.Although the physical process of SLM in a vacuum has been investigated by high-speed imaging,the underlying mechanisms governing the heat transfer and molten flow are still not well understood.Herein,we first developed a mesoscopic model of SLM under variable ambient pressure based on our recent laser-welding studies.We simulated the transport phenomena of SLM 316L stainless steel powders under atmospheric and 100 Pa ambient pressure.For typical process parameters(laser power:200W;scanning speed:2m∙s^(-1);powder diameter:27 lm),the average surface temperature of the cavity approached 2800 K under atmospheric pressure,while it came close to 2300 K under 100 Pa pressure.More vigorous fluid flow(average speed:4m∙s^(-1))was observed under 100 Pa ambient pressure,because the pressure difference between the evaporation-induced surface pressure and the ambient pressure was relatively larger and drives the flow under lower pressure.It was also shown that there are periodical ripple flows(period:14ls)affecting the surface roughness of the as-printed track.Moreover,the molten flow was shown to be laminar because the Reynolds number is less than 400 and is far below the critical value of turbulence;thus,the viscous dissipation is significant.It was demonstrated that under a vacuum or lower ambient pressure,the ripple flow can be dissipated more easily by the viscous effect because the trajectory length of the ripple is longer;thus,the surface quality of the tracks is improved.To summarize,our model elucidates the physical mechanisms of the interesting transport phenomena that have been observed in independent experimental studies of the SLM process under variable ambient pressure,which could be a powerful tool for optimizing the SLM process in the future.
基金Supported by Beijing Institute of Technology Research Fund Program for Young Scholars(2019CX04-031)Foundation Research Funds of Ministry of Industry and Information Technology(JCKY2019602D018)。
文摘Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions.Gasoline direct injection(GDI)has been recognized as one of the most effective ways to improve fuel atomization.As a special direct injection method,the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure.This injection method has excellent application potential and advantages for high performance and lightweight engines.In this study,the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa.External macro characteristics of spray were obtained using high speed backlit imaging.Phase Doppler particle analyzer(PDPA)was utilized to study the microcosmic spray characteristics.The results show that under the flash boiling condition,the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards.The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width.The sauter mean diameter(SMD)of flash boiling condition can be reduced to 5μm compared to the level close to 10μm in the non-flash boiling condition.
基金financially supported by the National Natural Science Foundation of China (Nos. 21174089, 21674068 and 51633004)
文摘A novel scale-up ambient pressure synthetic strategy for the preparation of imine-based covalent organic frameworks（COFs） was proposed through dynamic imine exchange reaction mechanism. The obtained COFs exhibited good crystallinity and much higher porosity comparable to their solvothermally synthesized counterparts. Moreover, under ambient pressure, the COF nanofibers could readily grow on the surface of polyimide films, and the resulted nanocomposite film showed an interesting colorimetric acid-responsive behavior.
基金financial support from National Natural Science Foundation of China(Nos.51702046,51772050 and 51822202)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University。
文摘An ambient pressure-induced calcination process was proposed to prepare g-C3 N4 with different structures.The porcelain boat with designed porosity is used to control the ambient pressure to change the diffusion behavior of the reaction molecules,thereby controlling the layer structure and rich pyridinic N content of g-C3 N4,thus renders superior lithium storage performance.
文摘In order to solve the problem of single arc plasma actuator's failure to suppress the boundary layer separation, the effectiveness of the array surface arc plasma actuator to enhance the excitation intensity is verified by experiment. In this study, an electrical parameter measurement system and high-speed schlieren technology were adopted to delve into the electrical, flow field, and excitation characteristics of the high-energy array surface arc plasma actuator under low ambient pressure. The high-energy array surface arc discharge released considerable heat rapidly;as a result, two characteristic structures were generated, i.e., the precursor shock wave and thermal deposition area. The duration increased with the increase in environmental pressure. The lower the pressure, the wider the thermal deposition area's influence range. The precursor shock wave exhibited a higher propagation speed at the initial phase of discharge;it tended to decay over time and finally remained at 340 m/s. The lower the environmental pressure, the higher the speed would be at the initial phase. High-energy array surface arc plasma actuator can be employed to achieve effective high-speed aircraft flow control.
基金Funded by the National High Technology Research and Development Program(863 Program)(No.2013AA050905),China Academy of Engineering Physics,Mianyang,China
文摘Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas and adjust pore size distribution. The synthesis process was optimized, and the morphology, structure, adsorption properties and electrochemical behavior of different samples were characterized. The CO2-activated samples achieved a high specific capacitance of 129.2 F/g in 6 M KOH electrolytes at the current density of 1 m A/cm^2 within the voltage range of 0-0.8 V. The optimized activation temperature and duration were determined to be 950 ℃ and 4 h, respectively.
基金supported by the National Natural Science Foundation of China(22472030,21902027)。
文摘X-ray photoelectron spectroscopy(XPS)is a crucial surface analysis technique that has become a key tool in the study of heterogeneous catalysis.Detecting surface chemistry under conditions that closely mimic actual industrial catalytic processes is essential for understanding the mechanisms involved.In the past decade,near ambient pressure X-ray photoelectron spectroscopy(NAP-XPS)has been increasingly utilized to study the surface chemistry of catalysts during heterogeneous catalytic processes,offering insights into structure-performance correlations.This review begins with a brief overview of NAP-XPS instrumentation.Next,we discuss the application of NAP-XPS in the study of thermal catalysis reactions,followed by a summary of the research on catalyst restructuring under reaction conditions.Additionally,we address the challenges and future perspectives for the development and application of NAP-XPS.Catalysis is inherently dynamic,requiring an understanding of the real-time behavior of catalysts under varying conditions.Therefore,future improvements in the ability to probe reaction intermediates with higher spatial and temporal resolution under conditions that closely mimic industrial environments are needed.
基金supported by the National Natural Science Foundation of China(NSFC),Basic Sciences Center Program(Extreme Light Field Manufacturing,No.52488301)and NSFC General Program(No.52475425)the National Key R&D Program of China(No.2022YFB4601300)Aeronautical Science Fund(No.3030021252404).
文摘Elucidation of a physicochemical process on nanocatalysts,especially under continuously evolving conditions,is often heavily tool-driven because of technical challenges.Recently,ambient pressure X-ray photoelectron spectroscopy(APXPS)emerges as an emerging photon-in-electron-out technique in in-situ/operando analysis by bridging the pressure-gap between conventional ultra-high vacuum(UHV)and near ambient or even close to operating conditions,rendering the advancement of XPS from a UHV-based technique to a versatile and powerful tool that enables the specific probe of numerous events taking place at the gas–solid,liquid–solid and liquid–gas nanoscale interfaces which are critical to nanocatalysis research.For example,APXPS probes information on catalytically active phase and reaction kinetics in nanocatalytic processes;details inside the electric double-layer at an electrolyte/electrode interface can now be accessed;more efficient nanocatalyst design can be achieved and energy transfer venues can be optimized.Here,we aim to critically review the recent advances in instrumentation and the probe of the gas–solid,liquid–solid,and gas–liquid nanoscale interfaces using APXPS-based methodologies,followed by putting forward an outlook of development of APXPS as a rising in-situ/operando analytical means in surface science,nanocatalysis,nanoscience materials science.
基金supported by the Nanjing University of Science & Technology Research Funding (Grant No. 2010ZDJH09)
文摘The dynamics of the laser-induced bubble at different ambient pressures was numerically studied by Finite Volume Method (FVM). The velocity of the bubble wall, the liquid jet velocity at collapse, and the pressure of the water hammer while the liquid jet impacting onto the boundary are found to increase nonlinearly with increasing ambient pressure. The collapse time and the formation time of the liquid jet are found to decrease nonlinearly with increasing ambient pressure. The ratios of the jet formation time to the collapse time, and the displacement of the bubble center to the maximal radius while the jet formation stay invariant when ambient pressure changes. These ratios are independent of ambient pressure.
文摘Here we present an economical ambient pressure drying method of preparing monolithic silica aerogels from methyltrimethoxysilane precursor while using sodium bicarbonate solution as the exchanging solvent.We prepared silica aerogels with a density and a specific surface area of 0.053 g·cm^(-3) and 423 m^(2)·g^(-1) respectively.The average pore diameter of silica aerogels is 23 nm as the pore specific volume is 1.11 cm^(3)·g^(-1),Further,the contact angle between water droplet and the surface of silica aerogels in specific condition can be as high as 166°,which indicates a super-hydrophobic surface of aerogels.
基金the National High Technology Research and Development Program of China (863 Program) (Grant No.2013AA031903)the Youth 973 Program (Grant No.2015CB932700)+7 种基金the National Natural Science Foundation of China (Grant Nos.91433107, 51222208, and 51290273)the Doctoral Fund of Ministry of Education of China (Grant No.20123201120026)ARC DP (DP140101501)ARC DECRA (DE120101569)Victoria DSI top-up grantthe Natural Science Foundation of Jiangsu Province (No.BK20130328)China Postdoctoral Science Foundation (No. 2014M551654)Jiangsu Province Postdoctoral Science Foundation (No.1301020A)
文摘Atomically thin MoS2 films have attracted significant attention due to excellent electrical and optical properties.The development of device applications demands the production of large-area thin film which is still an obstacle.In this work we developed a facile method to directly grow large-area MoS2 thin film on Si O2 substrate via ambient pressure chemical vapor deposition method. The characterizations by spectroscopy and electron microscopy reveal that the as-grown MoS2 film is mainly bilayer and trilayer with high quality. Back-gate field-effect transistor based on such MoS2 thin film shows carrier mobility up to 3.4 cm2V-1s-1 and on/off ratio of 105. The large-area atomically thin MoS2 prepared in this work has the potential for wide optoelectronic and photonic device applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.12122405,12274169,and 11574109)the Fundamental Research Funds for the Central Universities。
文摘The high-pressure phase diagram of the Nb-Ti binary system at 0 K is explored by systematic crystal structure prediction.The results highlight a novel niobium-rich bcc phase,Nb_(7)Ti,which is the only dynamically stable ordered Nb-Ti compound under ambient pressure.Extensive first-principles calculations have provided insights into the electronic structure,bonding and superconducting properties of Nb_(7)Ti.The superconducting transition temperature(T_(c))for Nb_(7)Ti at ambient pressure is estimated within the framework of BCS theory to be about 17.5 K,which is significantly higher—nearly double—that of the widely utilized NbTi alloy.Furthermore,the results unveil that the high T_(c) is mainly attributed to the unique ordered lattice along with the strong electron-phonon coupling driven by interatomic interactions at mid-frequency and phonon softening induced by low-frequency Fermi surface nesting.Valuable insights are provided for the subsequent synthesis of application-oriented superconductors at low pressure.
基金supported by the National Natural Science Foundation of China(51678511,51308484)the Natural Science Foundation of Hunan Province(13JJ4049)+3 种基金the Education Department Fund of Hunan Province(14C1094)the Open Fund of Key Laboratory of Mineralogy and Metallogeny in Chinese Academy of Sciences(KLMM20150104)the Major Talent Training Program of Xiangtan University(16PYZ09)the Specialized Research Fund for the Doctoral Program of Xiangtan University(12QDZ18)~~
文摘A novel‐structured Mo‐Cu‐Fe‐O composite was successfully prepared by co‐precipitation and impregnation method.The properties of the as‐prepared samples were determined using X‐ray diffraction,temperature‐programmed reduction by H2,cyclic voltammetry,and temperature‐programmed desorption by O2.The results showed that Mo6+diffused into the Cu‐Fe‐O crystal lattice and then formed a new crystalline phase of CuMoO4.The Mo‐Cu‐Fe‐O catalyst had redox properties,and its surface contained active sites for oxygen adsorption.In addition,the catalytic activity of the Mo‐Cu‐Fe‐O composite was evaluated by the degradation of Cationic Red GTL,Crystal Violet,and Acid Red in catalytic wet air oxidation(CWAO)at ambient temperature and pressure.The Mo‐Cu‐Fe‐O catalyst showed excellent activity at basic conditions for the degradation of Cationic Red GTL.High removal efficiencies of91.5%and92.8%were achieved for Cationic Red GTL and Crystal Violet,respectively,in wastewater,and the efficiency remained high after seven cycles.However,almost no degradation of Acid Red occurred in the CWAO process.Furthermore,hydroxyl radicals were formed in the CWAO process,which induced the decomposition of the two cationic dyes in wastewater,and the toxicity of their effluents was decreased after degradation.The results indicate that the Mo‐Cu‐Fe‐O composite shows excellent catalytic activity for the treatment of wastewater contaminated with cationic dyes.
基金supported by the National Natural Science Foundation of China(Grant Nos.12222413,12174443,12274459,and 12404266)the National Key R&D Program of China(Grant Nos.2023YFA1406500,2022YFA1403800,and 2022YFA1403103)+3 种基金the Natural Science Foundation of Shanghai (Grant No.23ZR1482200)the Natural Science Foundation of Ningbo (Grant No.2024J019)the Science Research Project of Hebei Education Department (Grant No.BJ2025060)the funding of Ningbo Yongjiang Talent Program。
文摘Superconducting elect rides have attracted growing attention for their potential to achieve high superconducting transition temperatures(T_(C))under pressure.However,many known elect rides are chemically reactive and unstable,making high-quality single-crystal growth,characterization,and measurements difficult,and most do not exhibit superconductivity at ambient pressure.In contrast,La_(3) In stands out for its ambient-pressure superconductivity(T_(C)∼9.4 K)and the availability of high-quality single crystals.Here,we investigate its low-energy electronic structure using angle-resolved photoemission spectroscopy and first-principles calculations.The bands near the Fermi energy(E_(F))are mainly derived from La 5d and In 5p orbitals.A saddle point is directly observed at the Brillouin zone(BZ)boundary,while a three-dimensional Van Hove singularity crosses E_(F) at the BZ corner.First-principles calculations further reveal topological Dirac surface states within the bulk energy gap above E_(F).The coexistence of a high density of states and in-gap topological surface states near𝐸F suggests that La3In offers a promising platform for tuning superconductivity and exploring possible topological superconducting phases through doping or external pressure.
