Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic pr...Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.展开更多
To advance the understanding of the corrosion behavior of stainless steel bellows in marine atmospheric environments and enhance the precision of service life predictions,this study employs finite element simulations ...To advance the understanding of the corrosion behavior of stainless steel bellows in marine atmospheric environments and enhance the precision of service life predictions,this study employs finite element simulations to investigate the pitting corrosion rates and pit morphologies of bellows peaks and troughs under varying electrolyte film thicknesses.The model incorporates localized electrochemical reactions,oxygen concentration,and homogeneous solution reactions.For improved computational accuracy,the fitted polarization curve data were directly applied as nonlinear boundary conditions on the electrode surface via interpolation functions.Simulation results reveal that the peak regions exhibit faster corrosion rates than the trough regions.With increasing electrolyte film thickness(from 10μm to 500μm),corrosion rates at both peaks and troughs decrease progressively,and after 120 hours of simulation,the maximum corrosion rate at the peaks declines from 0.720 mm/a to 0.130 mm/a,and at the troughs from 0.520 mm/a to 0.120 mm/a,with the disparity in corrosion rates diminishing over time.Furthermore,as corrosion progresses,pits propagate deeper into the substrate,exhibiting both vertical penetration and lateral expansion along the passive film interface,ultimately breaching the substrate.This research offers valuable insights into designing corrosion mitigation strategies for stainless steel bellows in marine environments.展开更多
In order to study the variation o f the asphalt pavement water film thickness influenced by multi-factors,anew method for predicting water film thickness was developed by the combination o f the artificial neural netw...In order to study the variation o f the asphalt pavement water film thickness influenced by multi-factors,anew method for predicting water film thickness was developed by the combination o f the artificial neural network(ANN)a d two-dimensional shallow water equations based on hydrodynamic theory.Multi-factors included the rainfall intensity,pavement width,cross slope,longitudinal slope a d pavement roughness coefficient.The two-dimensional hydrodynamic method was validated by a natural rainfall event.Based on the design scheme o f Shen-Sha expressway engineering project,the limited training data obtained by the two-dimensional hydrodynamic simulation model was used to predict water film thickness.Furthermore,the distribution of the water film thickness influenced by multi-factors on the pavement was analyzed.The accuracy o f the ANN model was verified by the18sets o f data with a precision o f0.991.The simulation results indicate that the water film thickness increases from the median strip to the edge o f the pavement.The water film thickness variation is obviously influenced by rainfall intensity.Under the condition that the pavement width is20m and t e rainfall intensity is3m m/h,t e water film thickness is below10mm in the fast lane and20mm in t e lateral lane.Athough there is fluctuation due to the amount oftraining data,compared with the calculation on the basis o f the existing criterion and theory,t e ANN model exhibits a better performance for depicting the macroscopic distribution of the asphalt pavement water film.展开更多
The dispersion of a solid particle in a liquid may lead to the formation of solvation film on the particle surface, which can strongly increase the repulsive force between particles and thus strongly affect the stabil...The dispersion of a solid particle in a liquid may lead to the formation of solvation film on the particle surface, which can strongly increase the repulsive force between particles and thus strongly affect the stability of dispersions. The solvation film thickness, which varies with the variation of the property of suspension particles and solutions, is one of the most important parameters of the solvation film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on the Einstein viscosity equation of dispersions, for determining the solvation film thickness of particles is developed. This method was tested on two kinds of silica spherical powders （namely M1 and M2） dispersed in ethyl alcohol, in water, and in a water-ethyl alcohol mixture （1：1 by volume） through measuring the relative viscosity of dispersions of the particles as a function of the volume fraction of the dry particles in the dispersion, and of the specific surface area and the density of the particles. The calculated solvation film thicknesses on M1 are 7.48, 18.65 and 23.74 nm in alcohol, water and the water-ethyl alcohol mixture, 12.41, 12.71 and 13.13 nm on M2 in alcohol, water and the water-ethyl alcohol mixture, respectively.展开更多
TaNx thin films were deposited on commercial polished Al2O3 ceramic substrates by reactive dc magnetron sputtering. The influences of the film thickness on the electrical properties of the samples were examined in det...TaNx thin films were deposited on commercial polished Al2O3 ceramic substrates by reactive dc magnetron sputtering. The influences of the film thickness on the electrical properties of the samples were examined in detail. It is found that the film thickness does not influence the phase structures of the TaNx thin films. The sheet resistances of the samples shift from 173 Ω/sq. to 7.5 Ω/sq. with the film thickness shifting from 30 nm to 280 nm. With the increase of the film thickness from 30 nm to 280 nm, the temperature coefficient of resistance （TCR） of the samples shifts from negative value to positive value. When the film thickness is about 100 nm, TaNx thin films exhibits a near-zero TCR value （approximately -15×10^-6/℃）. This fact implies that TaNx thin films with a null TCR can be obtained by adjusting the film thickness. The variation in the electrical properties of the TaNx thin films with the film thickness can be qualitatively explained by the parallel connection of surface layer with high resistivity and negative TCR and TaNx layer with low resistivity and positive TCR.展开更多
Mg films of various thicknesses were deposited on Si（111） substrates at room temperature by resistive thermal evaporation method, and then the Mg/Si samples were annealed at 40 ℃ for 4 h. The effects of Mg film thi...Mg films of various thicknesses were deposited on Si（111） substrates at room temperature by resistive thermal evaporation method, and then the Mg/Si samples were annealed at 40 ℃ for 4 h. The effects of Mg film thickness on the formation and structure of Mg2Si films were investigated. The results showed that the crystallization quality of Mg2Si films was strongly influenced by the thickness of Mg film. The XRD peak intensity of Mg2Si （220） gradually increased initially and then decreased with increasing Mg film thickness. The XRD peak intensity of Mg2Si （220） reached its maximum when the Mg film of 380 um was used. The thickness of the Mg2Si film annealed at 400℃ for 4 h was approximately 3 times of the Mg film.展开更多
Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterize...Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterized by intermittent motion of film region and slug region.This work aims to develop the ultrasonic Doppler method to realize the simultaneous measurement of the velocity profile and liquid film thickness of slug flow.A single-frequency single-channel transducer is adopted in the design of the field-programmable gate array based ultrasonic Doppler system.A multiple echo repetition technology is used to improve the temporal-spatial resolution for the velocity profile.An experiment of horizontal gas-liquid two-phase flow is implemented in an acrylic pipe with an inner diameter of 20 mm.Considering the aerated characteristics of the liquid slug,slug flow is divided into low-aerated slug flow,high-aerated slug flow and pseudo slug flow.The temporal-spatial velocity distributions of the three kinds of slug flows are reconstructed by using the ultrasonic velocity profile measurement.The evolution characteristics of the average velocity profile in slug flows are investigated.A novel method is proposed to derive the liquid film thickness based on the instantaneous velocity profile.The liquid film thickness can be effectively measured by detecting the position and the size of the bubbles nearly below the elongated gas bubble.Compared with the time of flight method,the film thickness measured by the Doppler system shows a higher accuracy as a bubble layer occurs in the film region.The effect of the gas distribution on the film thickness is uncovered in three kinds of slug flows.展开更多
The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thicknes...The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thickness mainly focus on stagnant flow,and some of them remain inaccurate performance.However,in the industrial process,the slug flow essentially is co-current flow.Therefore,in this paper,the liquid film thickness is studied by theoretical analysis and experimental methods under two conditions of stagnant and co-current flow.Firstly,under the condition of stagnant flow,the present work is based on Batchelor's theory,and modifies Batchelor's liquid film thickness model,which effectively improves its prediction accuracy.Under the condition of co-current flow,the prediction model of average liquid film thickness in slug flow is established by force and motion analysis.Taylor bubble length is introduced into the model as an important parameter.Dynamic experiments were carried out in the pipe with an inner diameter of 20 mm.The liquid film thickness,Taylor bubble velocity and length were measured by distributed ultrasonic sensor and intrusive cross-correlation conductivity sensor.Comparing the predicted value of the model with the measured results,the relative error is controlled within 10%.展开更多
In plain mortar,the water film thickness(WFT)has been found to play a key role in the fresh properties.However,in fiber-reinforced mortar,the role of WFT has not been investigated yet.In this research,basalt fibers of...In plain mortar,the water film thickness(WFT)has been found to play a key role in the fresh properties.However,in fiber-reinforced mortar,the role of WFT has not been investigated yet.In this research,basalt fibers of different lengths were added to the mortar,and the dynamic and static flowability,cohesiveness,adhesiveness,and packing density were tested to study the effects of fiber length on the packing density and WFT,and the combined effects of fiber length and WFT on the fresh properties.The results showed that in fiber-reinforced mortar,the WFT also plays a key role,whereas the fiber length exerts its influences through the indirect effects on the packing density and WFT and the direct effect on fiber-mortar interaction.Basically,an increase in fiber length decreases the packing density and WFT,decreases the dynamic and static flowability needed for placing,increases the cohesiveness needed for avoiding segregation,and,quite unexpectedly,decreases the adhesiveness needed for rendering and spraying applications.Regression analysis yielded good correlation of the fresh properties to fiber length and WFT,and best-fit formulas for the mix design for basalt fiber-reinforced mortar were obtained.展开更多
We investigated the effects of molecular weight and film thickness on the crystallization and microphase separation in semicrystalline block copolymer polystyrene-block-poly（L-lactic acid） （PS-b-PLLA） thin films, ...We investigated the effects of molecular weight and film thickness on the crystallization and microphase separation in semicrystalline block copolymer polystyrene-block-poly（L-lactic acid） （PS-b-PLLA） thin films, at the early stage of film evolution （when Tg 〈 T 〈 TODT） by in situ hot stage atomic force microscopy. For PS-b-PLLA 1 copolymer which had lower molecular weight and higher PLLA fraction, diffusion-controlled break-out crystallization started easily. For PS-b-PLLA 2 with higher molecular weight, crystallization in nanometer scales occurs in local area. After melting of the two copolymer films, islands were observed at the film surface： PS-b-PLLA 1 film was in a disordered phase mixed state while PS-b-PLLA 2 film formed phase-separated lamellar structure paralleling to the substrate. Crystallization-melting and van der Waals forces drove the island formation in PS-b-PLLA 1 film. Film thickness affected the crystallization rate. Crystals grew very slowly in much thinner film of PS-b-PLLA 1 and remained almost unchanged at long time annealing. The incompatibility between PS and PLLA blocks drove the film fluctuation which subsequently evolved into spinodal-like morphology.展开更多
The thickness of TiO2 film is vital to realize the optimization on photovoltaic performance of dye sensitized solar cells （DSSCs）. Herein, the process of charge separation in DSSCs was simulated by using a drift-dif...The thickness of TiO2 film is vital to realize the optimization on photovoltaic performance of dye sensitized solar cells （DSSCs）. Herein, the process of charge separation in DSSCs was simulated by using a drift-diffusion model. This model allows multiple-trapping diffu- sion of photo-generated electrons, as well as the back reaction with the electron acceptors in electrolyte, to be mimicked in both steady and non-steady states. Numerical results on current-voltage characteristics allow power conversion efficiency to be maximized by varying the thickness of TiO2 film. Charge collection efficiency is shown to decrease with film thick- ness, whereas the flux of electron injection benefits from the film thickening. The output of photocurrent is actually impacted by the two factors. Furthermore, recombination rate constant is found to affect the optimized film thickness remarkably. Thicker TiO2 film is suitable to the DSSCs in which back reaction is suppressed sufficiently. On the contrary, the DSSCs with the redox couple showing fast electron interception require thinner film to alleviate the charge loss via recombination. At open circuit, electron density is found to decrease with film thickness, which engenders not only the reduction of photovoltage but also the increase of electron lifetime.展开更多
Equation(6)in Chin.Phys.090833(2000)is corrected.All subsequent derivations were given based on the correct Eq.(6),so the conclusions in the paper are not ffected by the rrata.
This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave(BSW) enhanced Goos–Hanchen(GH) shift in one-dimensional photonic crystal(1DPC). The BSW phe...This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave(BSW) enhanced Goos–Hanchen(GH) shift in one-dimensional photonic crystal(1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization(PSO) algorithm.The relationship between the structure of a 1DPC film composed of TiO_(2) and SiO_(2) layers and the GH shift, is investigated.Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1 × 10^(3) times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift.展开更多
A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two...A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two-fluid model is used to calculate both gas and liquid phases’flow characteristics.The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced.Moreover,energy conservation is applied for obtaining the liquid film thickness distribution along the circumference.Liquid film thickness distribution is calculated accordingly for different cases;its values are compared with other models and available experimental data.As a result,the newly proposed model is tested and good performances are demonstrated.The liquid film thickness distribution in small pipes and inclined pipes is also studied,and regime transition is revealed by liquid film profile evolution.The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference,when the circle angle ranges between 30°and 50°for gas-liquid stratified flow with small superficial velocities.展开更多
The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film prop...The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.展开更多
This work introduces a novel method for measuring thin film thickness,employing a multi-wavelength method that significantly reduces the need for broad-spectrum data.Unlike traditional techniques that require sev⁃eral...This work introduces a novel method for measuring thin film thickness,employing a multi-wavelength method that significantly reduces the need for broad-spectrum data.Unlike traditional techniques that require sev⁃eral hundred spectral data points,the multi-wavelength method achieves precise thickness measurements with data from only 10 wavelengths.This innovation not only simplifies the process of spectral measurement analysis but also enables accurate real-time thickness measurement on industrial coating production lines.The method effectively reconstructs and fits the visible spectrum(400-800 nm)using a minimal amount of data,while maintaining measurement error within 7.1%.This advancement lays the foundation for more practical and efficient thin film thickness determination techniques in various industrial applications.展开更多
Cu/HfOx/n^＋Si devices are fabricated to investigate the influence of technological parameters including film thickness and Ar/02 ratio on the resistive switching （RS） characteristics of HfOx films, in terms of swit...Cu/HfOx/n^＋Si devices are fabricated to investigate the influence of technological parameters including film thickness and Ar/02 ratio on the resistive switching （RS） characteristics of HfOx films, in terms of switch ratio, endurance properties, retention time and multilevel storage. It is revealed that the RS characteristics show strong dependence on technological parameters mainly by altering the defects （oxygen vacancies） in the film. The sample with thickness of 2Onto and Ar/O2 ratio of 12：3 exhibits the best RS behavior with the potential of multilevel storage. The conduction mechanism of all the films is interpreted based on the filamentary model.展开更多
The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the re...The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.展开更多
Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean mi...Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean minimum-quantity lubrication technology still has defects,such as insufficient heat dissipation.The use of cryogenic air instead of normal temperature air,that is,the supply of low-temperature energized lubricant,can effectively improve oil film heat transfer and lubrication performance in a grinding area.Under the premise of ensuring the effective flow of lubricating oil in a grinding zone,the thickness of a liquid film in the wedge zone of a grinding wheel or workpiece is the key factor for determining its performance.However,the dynamic mechanism of droplet formation and distribution of liquid film thickness are still unclear.Hence,the mechanism by which nozzle orientation influences the effective region of a liquid film was analyzed,and the range of nozzle inclination that helps to atomize droplets and enables them to enter the grinding zone was revealed.Then,the dynamic mechanism of atomized droplet film formation was analyzed,and the influence of normal and tangential momentum sources generated by gas impingement perturbation flow and droplet impingement steady flow on the driving effect of liquid film flow was revealed.The thickness distribution model of a liquid film in the impact zone of gas–liquid two-phase flow under different cryogenic air temperatures was established.The model results under different working conditions were obtained by numerical analysis,and validation experiments were carried out.Results show that the measured values agree with the theoretical values.At 0.4 MPa air pressure,the thickness of the liquid film in the impact zone of the atomized droplets increases with decreasing cryogenic air temperature.At−10 and−50°C,the thickness of the liquid film is 0.92 and 1.26 mm,respectively.Further,on the basis of the surface topography model of cubic boron nitride grinding wheel,the pose relationship of any three adjacent abrasive particles was analyzed,and the theoretical model of abrasive clearance volume was established.The dynamic variation of abrasive clearance volume distribution domain is[70.46,78.72]mm3,and the total volume distribution domain is[140.84,155.67]mm3.The research will provide a theoretical basis for the application of cryogenic air minimum quantity lubrication technology to hard metal grinding.展开更多
This study used laser spectroscopy testing technology and independently constructed a testing apparatus to achieve stable measurements of the adsorbed liquid film thickness on copper surfaces.The apparatus measurement...This study used laser spectroscopy testing technology and independently constructed a testing apparatus to achieve stable measurements of the adsorbed liquid film thickness on copper surfaces.The apparatus measurement accuracy reached 91.7%.Using this apparatus,the thickness of the adsorbed liquid film on copper surfaces was measured and analyzed under different temperatures,relative humidity(RH),and salt(NaCl)deposition density conditions.According to the results,increased temperature,RH,and NaCl deposition increased the liquid film thickness.Furthermore,the liquid film thickness increased exponentially with increasing RH under the same temperature and Na Cl deposition conditions.Surface fitting of the obtained liquid film thickness data yielded a fitting calculation formula for the adsorbed liquid film thickness on copper surfaces under typical atmospheric temperature conditions(25–45℃).In addition,artificial neural networks(ANNs)and support vector machine models were constructed based on machine learning methods for predicting liquid film thickness.Comparative results indicated that the ANN prediction model exhibited higher accuracy,with a model determination coefficient (R^(2)) reaching 0.99.Validation by comparing measured and predicted values under typical conditions for liquid film thickness showed that the machine learning-based prediction error was approximately 9.7%.This approach rapidly predicted adsorbed liquid film thickness on copper surfaces subjected to atmospheric humid and hot NaCl deposition.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 22375157 and W2433042)the Key Scientific and Technological Innovation Team of Shaanxi Province(No. 2020TD-001)+1 种基金the Fundamental Research Funds for Central Universities, State Key Laboratory of Electrical Insulation and Power Equipment (No. EIPE23409)the Instrument Analysis Center of Xi’an Jiaotong University for assistance。
文摘Lead-free hybrid double perovskites(LFHDPs) have received a lot of attention due to their environmental friendliness and promising attributes. However, studying the effect of film thickness on LFHDPs optoelectronic properties has not yet been investigated. Herein, we synthesized two new Ruddlesden–Popper LFHDPs, namely(C_(5)H_(12)N)_(4)AgBiI_(8)(CAB-1) and(C_(6)H_(14)N)_(4)Ag Bi I8(CAB-2) using cyclopentylamine and cyclohexylamine as monoamine ligands. Indeed, these two Ag(Ⅰ)-Bi(Ⅲ) LFHDPs form smooth and uniform films ranging in thickness from 250 nm to 1 μm, with preferred orientations. Notably, the studies on the optical properties showed that the direct band gap value decreased from 2.17 e V to 1.91 e V for CAB-1 and from 2.05 e V to 1.86 e V for CAB-2 with increasing thickness. Accordingly, photo-current response using a xenon lamp revealed a significant difference of over 1000 n A between light and dark conditions for1 μm-thickness films, suggesting potential for light harvesting. Other than that, thicker films of CAB-1and CAB-2 exhibit high stability for 90 days in a relatively humid environment(RH of 55%), paving the way for promising optoelectronic applications.
基金supported by the National Natural Science Foundation of China(No.52074130)Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality,Ministry of Education,200237 Shanghai,PR China.
文摘To advance the understanding of the corrosion behavior of stainless steel bellows in marine atmospheric environments and enhance the precision of service life predictions,this study employs finite element simulations to investigate the pitting corrosion rates and pit morphologies of bellows peaks and troughs under varying electrolyte film thicknesses.The model incorporates localized electrochemical reactions,oxygen concentration,and homogeneous solution reactions.For improved computational accuracy,the fitted polarization curve data were directly applied as nonlinear boundary conditions on the electrode surface via interpolation functions.Simulation results reveal that the peak regions exhibit faster corrosion rates than the trough regions.With increasing electrolyte film thickness(from 10μm to 500μm),corrosion rates at both peaks and troughs decrease progressively,and after 120 hours of simulation,the maximum corrosion rate at the peaks declines from 0.720 mm/a to 0.130 mm/a,and at the troughs from 0.520 mm/a to 0.120 mm/a,with the disparity in corrosion rates diminishing over time.Furthermore,as corrosion progresses,pits propagate deeper into the substrate,exhibiting both vertical penetration and lateral expansion along the passive film interface,ultimately breaching the substrate.This research offers valuable insights into designing corrosion mitigation strategies for stainless steel bellows in marine environments.
基金The National Natural Science Foundation of China(No.51478114,51778136)the Transportation Science and Technology Program of Liaoning Province(No.201532)
文摘In order to study the variation o f the asphalt pavement water film thickness influenced by multi-factors,anew method for predicting water film thickness was developed by the combination o f the artificial neural network(ANN)a d two-dimensional shallow water equations based on hydrodynamic theory.Multi-factors included the rainfall intensity,pavement width,cross slope,longitudinal slope a d pavement roughness coefficient.The two-dimensional hydrodynamic method was validated by a natural rainfall event.Based on the design scheme o f Shen-Sha expressway engineering project,the limited training data obtained by the two-dimensional hydrodynamic simulation model was used to predict water film thickness.Furthermore,the distribution of the water film thickness influenced by multi-factors on the pavement was analyzed.The accuracy o f the ANN model was verified by the18sets o f data with a precision o f0.991.The simulation results indicate that the water film thickness increases from the median strip to the edge o f the pavement.The water film thickness variation is obviously influenced by rainfall intensity.Under the condition that the pavement width is20m and t e rainfall intensity is3m m/h,t e water film thickness is below10mm in the fast lane and20mm in t e lateral lane.Athough there is fluctuation due to the amount oftraining data,compared with the calculation on the basis o f the existing criterion and theory,t e ANN model exhibits a better performance for depicting the macroscopic distribution of the asphalt pavement water film.
基金This work is financially supported by the Consejo Nacional de Ciencia y Tecnología (CONACyT) of Mexico under the grant #485100-5-38214-U.
文摘The dispersion of a solid particle in a liquid may lead to the formation of solvation film on the particle surface, which can strongly increase the repulsive force between particles and thus strongly affect the stability of dispersions. The solvation film thickness, which varies with the variation of the property of suspension particles and solutions, is one of the most important parameters of the solvation film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on the Einstein viscosity equation of dispersions, for determining the solvation film thickness of particles is developed. This method was tested on two kinds of silica spherical powders （namely M1 and M2） dispersed in ethyl alcohol, in water, and in a water-ethyl alcohol mixture （1：1 by volume） through measuring the relative viscosity of dispersions of the particles as a function of the volume fraction of the dry particles in the dispersion, and of the specific surface area and the density of the particles. The calculated solvation film thicknesses on M1 are 7.48, 18.65 and 23.74 nm in alcohol, water and the water-ethyl alcohol mixture, 12.41, 12.71 and 13.13 nm on M2 in alcohol, water and the water-ethyl alcohol mixture, respectively.
基金support by the StateKey Laboratory of Electronic Thin Films and Integrated Devices under Grant No.KFJJ200804support by the StateKey Laboratory of Electronic Thin Films and Integrated Devices under Grant No.KFJJ200804Supporting Project of Sichuan under Grant No.2010G20156
文摘TaNx thin films were deposited on commercial polished Al2O3 ceramic substrates by reactive dc magnetron sputtering. The influences of the film thickness on the electrical properties of the samples were examined in detail. It is found that the film thickness does not influence the phase structures of the TaNx thin films. The sheet resistances of the samples shift from 173 Ω/sq. to 7.5 Ω/sq. with the film thickness shifting from 30 nm to 280 nm. With the increase of the film thickness from 30 nm to 280 nm, the temperature coefficient of resistance （TCR） of the samples shifts from negative value to positive value. When the film thickness is about 100 nm, TaNx thin films exhibits a near-zero TCR value （approximately -15×10^-6/℃）. This fact implies that TaNx thin films with a null TCR can be obtained by adjusting the film thickness. The variation in the electrical properties of the TaNx thin films with the film thickness can be qualitatively explained by the parallel connection of surface layer with high resistivity and negative TCR and TaNx layer with low resistivity and positive TCR.
基金Supported by the National Natural Science Foundation of China(No.61264004)the Special Fund for International Cooperation of the Ministry of Science and Technology of China(No.2008DFA52210)+5 种基金the Key Sci-Tech Research Project of Guizhou Province of China(No.20113015)the Special Fund for Construction of Sci-Tech Innovative Talents Team of Guizhou Province of China(No.20114002)the Fund for International Sci-Tech Cooperation of Guizhou Province of China(No.20127004)the National Natural Science Foundation of Guizhou Province of China(No.20112323)the Young Talents Training Project of Guizhou Province of China(No.2012152)the Introducing Talents Foundation for the Doctor of Guizhou University of China(No.2010032)
文摘Mg films of various thicknesses were deposited on Si（111） substrates at room temperature by resistive thermal evaporation method, and then the Mg/Si samples were annealed at 40 ℃ for 4 h. The effects of Mg film thickness on the formation and structure of Mg2Si films were investigated. The results showed that the crystallization quality of Mg2Si films was strongly influenced by the thickness of Mg film. The XRD peak intensity of Mg2Si （220） gradually increased initially and then decreased with increasing Mg film thickness. The XRD peak intensity of Mg2Si （220） reached its maximum when the Mg film of 380 um was used. The thickness of the Mg2Si film annealed at 400℃ for 4 h was approximately 3 times of the Mg film.
基金supported by the National Natural Science Foundation of China(41974139,42274148,42074142)。
文摘Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterized by intermittent motion of film region and slug region.This work aims to develop the ultrasonic Doppler method to realize the simultaneous measurement of the velocity profile and liquid film thickness of slug flow.A single-frequency single-channel transducer is adopted in the design of the field-programmable gate array based ultrasonic Doppler system.A multiple echo repetition technology is used to improve the temporal-spatial resolution for the velocity profile.An experiment of horizontal gas-liquid two-phase flow is implemented in an acrylic pipe with an inner diameter of 20 mm.Considering the aerated characteristics of the liquid slug,slug flow is divided into low-aerated slug flow,high-aerated slug flow and pseudo slug flow.The temporal-spatial velocity distributions of the three kinds of slug flows are reconstructed by using the ultrasonic velocity profile measurement.The evolution characteristics of the average velocity profile in slug flows are investigated.A novel method is proposed to derive the liquid film thickness based on the instantaneous velocity profile.The liquid film thickness can be effectively measured by detecting the position and the size of the bubbles nearly below the elongated gas bubble.Compared with the time of flight method,the film thickness measured by the Doppler system shows a higher accuracy as a bubble layer occurs in the film region.The effect of the gas distribution on the film thickness is uncovered in three kinds of slug flows.
基金supported by National Natural Science Foundation of China(42074142,51527805)。
文摘The hydrodynamic study of the liquid film around Taylor bubbles in slug flow has great significance for understanding parallel flow and interaction between Taylor bubbles.The prediction models for liquid film thickness mainly focus on stagnant flow,and some of them remain inaccurate performance.However,in the industrial process,the slug flow essentially is co-current flow.Therefore,in this paper,the liquid film thickness is studied by theoretical analysis and experimental methods under two conditions of stagnant and co-current flow.Firstly,under the condition of stagnant flow,the present work is based on Batchelor's theory,and modifies Batchelor's liquid film thickness model,which effectively improves its prediction accuracy.Under the condition of co-current flow,the prediction model of average liquid film thickness in slug flow is established by force and motion analysis.Taylor bubble length is introduced into the model as an important parameter.Dynamic experiments were carried out in the pipe with an inner diameter of 20 mm.The liquid film thickness,Taylor bubble velocity and length were measured by distributed ultrasonic sensor and intrusive cross-correlation conductivity sensor.Comparing the predicted value of the model with the measured results,the relative error is controlled within 10%.
基金Project supported by the National Natural Science Foundation of China(Nos.51608131 and 51808134)the European Regional Development Fund(No.01.2.2-LMT-K-718-03-0010)under grant agreement with the Research Council of Lithuania(LMTLT)+3 种基金the Marie Skłodowska-Curie Actions of the European Commission(No.751461)the Colleges Innovation Project of Guangdong Province(No.2017KTSCX061)the Pearl River S&T Nova Program of Guangzhou City(No.201906010064)the Natural Science Foundation of Guangdong Province(No.2021A1515011747),China。
文摘In plain mortar,the water film thickness(WFT)has been found to play a key role in the fresh properties.However,in fiber-reinforced mortar,the role of WFT has not been investigated yet.In this research,basalt fibers of different lengths were added to the mortar,and the dynamic and static flowability,cohesiveness,adhesiveness,and packing density were tested to study the effects of fiber length on the packing density and WFT,and the combined effects of fiber length and WFT on the fresh properties.The results showed that in fiber-reinforced mortar,the WFT also plays a key role,whereas the fiber length exerts its influences through the indirect effects on the packing density and WFT and the direct effect on fiber-mortar interaction.Basically,an increase in fiber length decreases the packing density and WFT,decreases the dynamic and static flowability needed for placing,increases the cohesiveness needed for avoiding segregation,and,quite unexpectedly,decreases the adhesiveness needed for rendering and spraying applications.Regression analysis yielded good correlation of the fresh properties to fiber length and WFT,and best-fit formulas for the mix design for basalt fiber-reinforced mortar were obtained.
基金supported by the National Natural Science Foundation of China(Nos.20621401,50773080, 20834005)the Ministry of Science and Technology of China(No.2009CB930603)
文摘We investigated the effects of molecular weight and film thickness on the crystallization and microphase separation in semicrystalline block copolymer polystyrene-block-poly（L-lactic acid） （PS-b-PLLA） thin films, at the early stage of film evolution （when Tg 〈 T 〈 TODT） by in situ hot stage atomic force microscopy. For PS-b-PLLA 1 copolymer which had lower molecular weight and higher PLLA fraction, diffusion-controlled break-out crystallization started easily. For PS-b-PLLA 2 with higher molecular weight, crystallization in nanometer scales occurs in local area. After melting of the two copolymer films, islands were observed at the film surface： PS-b-PLLA 1 film was in a disordered phase mixed state while PS-b-PLLA 2 film formed phase-separated lamellar structure paralleling to the substrate. Crystallization-melting and van der Waals forces drove the island formation in PS-b-PLLA 1 film. Film thickness affected the crystallization rate. Crystals grew very slowly in much thinner film of PS-b-PLLA 1 and remained almost unchanged at long time annealing. The incompatibility between PS and PLLA blocks drove the film fluctuation which subsequently evolved into spinodal-like morphology.
文摘The thickness of TiO2 film is vital to realize the optimization on photovoltaic performance of dye sensitized solar cells （DSSCs）. Herein, the process of charge separation in DSSCs was simulated by using a drift-diffusion model. This model allows multiple-trapping diffu- sion of photo-generated electrons, as well as the back reaction with the electron acceptors in electrolyte, to be mimicked in both steady and non-steady states. Numerical results on current-voltage characteristics allow power conversion efficiency to be maximized by varying the thickness of TiO2 film. Charge collection efficiency is shown to decrease with film thick- ness, whereas the flux of electron injection benefits from the film thickening. The output of photocurrent is actually impacted by the two factors. Furthermore, recombination rate constant is found to affect the optimized film thickness remarkably. Thicker TiO2 film is suitable to the DSSCs in which back reaction is suppressed sufficiently. On the contrary, the DSSCs with the redox couple showing fast electron interception require thinner film to alleviate the charge loss via recombination. At open circuit, electron density is found to decrease with film thickness, which engenders not only the reduction of photovoltage but also the increase of electron lifetime.
文摘Equation(6)in Chin.Phys.090833(2000)is corrected.All subsequent derivations were given based on the correct Eq.(6),so the conclusions in the paper are not ffected by the rrata.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.51575387 and 51827812)。
文摘This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave(BSW) enhanced Goos–Hanchen(GH) shift in one-dimensional photonic crystal(1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization(PSO) algorithm.The relationship between the structure of a 1DPC film composed of TiO_(2) and SiO_(2) layers and the GH shift, is investigated.Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1 × 10^(3) times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift.
基金support provided by Shandong Provincial Science and Technology Plan Project(No.2023TSGC0625)Natural Resources Defense Council(NRDC,K94).
文摘A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two-fluid model is used to calculate both gas and liquid phases’flow characteristics.The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced.Moreover,energy conservation is applied for obtaining the liquid film thickness distribution along the circumference.Liquid film thickness distribution is calculated accordingly for different cases;its values are compared with other models and available experimental data.As a result,the newly proposed model is tested and good performances are demonstrated.The liquid film thickness distribution in small pipes and inclined pipes is also studied,and regime transition is revealed by liquid film profile evolution.The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference,when the circle angle ranges between 30°and 50°for gas-liquid stratified flow with small superficial velocities.
文摘The a-Si∶H films with different thickness smaller than 1 μm were deposited by plasma enhanced chemical vapor deposition (PECVD) under the optimum deposition conditions. The effect of different thickness on film properties is analyzed.The results show that,with the increase of the film thickness,the dark conductivity, photoconductivity and threshold voltage increase, the optical gap and peak ratio of TA to TO in the Raman spectra decrease, the refractive index keeps almost constant, and the optical absorption coefficient and current ratio of on/off state first maximize and then reduce.
基金Supported by National Key R&D Program of China(2021YFA0715500)National Natural Science Foundation of China(NSFC)(12227901)+2 种基金Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB0580000)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Chinese Academy of Sciences President's International Fellowship Initiative(2021PT0007).
文摘This work introduces a novel method for measuring thin film thickness,employing a multi-wavelength method that significantly reduces the need for broad-spectrum data.Unlike traditional techniques that require sev⁃eral hundred spectral data points,the multi-wavelength method achieves precise thickness measurements with data from only 10 wavelengths.This innovation not only simplifies the process of spectral measurement analysis but also enables accurate real-time thickness measurement on industrial coating production lines.The method effectively reconstructs and fits the visible spectrum(400-800 nm)using a minimal amount of data,while maintaining measurement error within 7.1%.This advancement lays the foundation for more practical and efficient thin film thickness determination techniques in various industrial applications.
基金Supported by the National Natural Science Foundation of China under Grant No 51202196the National Aerospace Science Foundation of China under Grant No 2013ZF53067+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China under Grant No 2014JQ6204the Fundamental Research Funds for the Central Universities under Grant No 3102014JCQ01032the 111 Project under Grant No B08040
文摘Cu/HfOx/n^＋Si devices are fabricated to investigate the influence of technological parameters including film thickness and Ar/02 ratio on the resistive switching （RS） characteristics of HfOx films, in terms of switch ratio, endurance properties, retention time and multilevel storage. It is revealed that the RS characteristics show strong dependence on technological parameters mainly by altering the defects （oxygen vacancies） in the film. The sample with thickness of 2Onto and Ar/O2 ratio of 12：3 exhibits the best RS behavior with the potential of multilevel storage. The conduction mechanism of all the films is interpreted based on the filamentary model.
基金supported by the National Key R&D Program of China(Gran Nos.2022YFA1402304 and 2022YFA1402802)the National Natural Science Foundation of China(Grant Nos.12494591,12122405,12274169,and 92165204)+4 种基金Program for Science and Technology Innovation Team in Zhejiang(Grant No.2021R01004)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)Guangdong Fundamental Research Center for Magnetoelectric Physics(2024B0303390001)Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2401010)the Fundamental Research Funds for the Central Universities。
文摘The discovery of high-temperature superconductivity in bilayer nickelate La_(3)Ni_(2)O_(7)under high-pressure conditions has spurred extensive efforts to stabilize superconductivity at ambient pressure.Recently,the realization of superconductivity in compressively strained La_(3)Ni_(2)O_(7)thin films grown on the SrLaAlO_(4)substrates,with a T_(c)exceeding 40 K,represents a significant step toward this goal.Here,we investigate the influence of film thickness and carrier doping on the electronic structure of La_(3)Ni_(2)O_(7)thin films,ranging from 0.5 to 3 unit cells,using first-principles calculations.For a 2 unit-cell film with an optimal doping concentration of 0.3 hole per formula unit(0.15 hole/Ni),the Ni-d_(z^(2))interlayer bonding state crosses the Fermi level,resulting in the formation ofγpockets at the Fermi surface.These findings align with angle-resolved photoemission spectroscopy experimental data.Our results provide theoretical validation for the recent experimental discovery of ambient-pressure superconductivity in La_(3)Ni_(2)O_(7)thin films and underscore the significant impact of film thickness and carrier doping on electronic property modulation.
基金financially supported by the National Natural Science Foundation of China(Grant No.52375447)Shandong Provincial Natural Science Foundation of General Program,China(Grant No.ZR2024ME205)+1 种基金the Special Fund of Taishan Scholars Project,China(Grant No.tsqn202408220)Shandong Provincial Natural Science Foundation of Youth Fund,China(Grant No.ZR2021QE116).
文摘Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean minimum-quantity lubrication technology still has defects,such as insufficient heat dissipation.The use of cryogenic air instead of normal temperature air,that is,the supply of low-temperature energized lubricant,can effectively improve oil film heat transfer and lubrication performance in a grinding area.Under the premise of ensuring the effective flow of lubricating oil in a grinding zone,the thickness of a liquid film in the wedge zone of a grinding wheel or workpiece is the key factor for determining its performance.However,the dynamic mechanism of droplet formation and distribution of liquid film thickness are still unclear.Hence,the mechanism by which nozzle orientation influences the effective region of a liquid film was analyzed,and the range of nozzle inclination that helps to atomize droplets and enables them to enter the grinding zone was revealed.Then,the dynamic mechanism of atomized droplet film formation was analyzed,and the influence of normal and tangential momentum sources generated by gas impingement perturbation flow and droplet impingement steady flow on the driving effect of liquid film flow was revealed.The thickness distribution model of a liquid film in the impact zone of gas–liquid two-phase flow under different cryogenic air temperatures was established.The model results under different working conditions were obtained by numerical analysis,and validation experiments were carried out.Results show that the measured values agree with the theoretical values.At 0.4 MPa air pressure,the thickness of the liquid film in the impact zone of the atomized droplets increases with decreasing cryogenic air temperature.At−10 and−50°C,the thickness of the liquid film is 0.92 and 1.26 mm,respectively.Further,on the basis of the surface topography model of cubic boron nitride grinding wheel,the pose relationship of any three adjacent abrasive particles was analyzed,and the theoretical model of abrasive clearance volume was established.The dynamic variation of abrasive clearance volume distribution domain is[70.46,78.72]mm3,and the total volume distribution domain is[140.84,155.67]mm3.The research will provide a theoretical basis for the application of cryogenic air minimum quantity lubrication technology to hard metal grinding.
基金financially supported by the Basic Technical Subject of State Administration of Science,Technology and Industry for National DefenceOpen Foundation of the Guangdong Provincial Key Laboratory of Electronic Information Products Reliability Technology
文摘This study used laser spectroscopy testing technology and independently constructed a testing apparatus to achieve stable measurements of the adsorbed liquid film thickness on copper surfaces.The apparatus measurement accuracy reached 91.7%.Using this apparatus,the thickness of the adsorbed liquid film on copper surfaces was measured and analyzed under different temperatures,relative humidity(RH),and salt(NaCl)deposition density conditions.According to the results,increased temperature,RH,and NaCl deposition increased the liquid film thickness.Furthermore,the liquid film thickness increased exponentially with increasing RH under the same temperature and Na Cl deposition conditions.Surface fitting of the obtained liquid film thickness data yielded a fitting calculation formula for the adsorbed liquid film thickness on copper surfaces under typical atmospheric temperature conditions(25–45℃).In addition,artificial neural networks(ANNs)and support vector machine models were constructed based on machine learning methods for predicting liquid film thickness.Comparative results indicated that the ANN prediction model exhibited higher accuracy,with a model determination coefficient (R^(2)) reaching 0.99.Validation by comparing measured and predicted values under typical conditions for liquid film thickness showed that the machine learning-based prediction error was approximately 9.7%.This approach rapidly predicted adsorbed liquid film thickness on copper surfaces subjected to atmospheric humid and hot NaCl deposition.
