Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Nanomechanics of Mg-Gd-Y-Nd-Zn alloy with LPSO and MgRE phases

The mechanical properties of two main precipitating phases(LPSO and MgRE)and matrix in Mg-Gd-Y-Nd-Zn bioalloy were examined using nanoindentation method.A new is suggested for characterizing the elastic-plastic behavior,fracture toughness and strain rate sensitivity(SRS)of materials within micro/nanoscale.Firstly,a nanomechanical model was developed for extracting hardness(H),young’s modulus(E)and yield stress(σY)from the characteristic load points which were subsequently analyzed by atomic force microscope(AFM)images.The elasticity data and AFM data were then utilized for determination of plastic deformation in constituent phases.The displacement of the indentation gets the highest value for Mg matrix and between precipitates,depth is more in LPSO rather than that of MgRE.The serrated flow or the behavior of shear bands may originate from the side effect of the interface region in Mg alloys with precipitates.It can be deduced that the KIC produced by both L method and energy-based calculation are both reliable for KIC approximation.The maximum load in simulation withμ=0.2 friction is marginally lesser than that of the frictionless(μ=0)one while elastic recovery of indentation withμ=0.2 is higher to some extent.

Numerical Solutions of the Classical and Modified Buckley-Leverett Equations Applied to Two-Phase Fluid Flow

Climate change is a reality. The burning of fossil fuels from oil, natural gas and coal is responsible for much of the pollution and the increase in the planet’s average temperature, which has raised discussions on the subject, given the emergencies related to climate. An energy transition to clean and renewable sources is necessary and urgent, but it will not be quick. In this sense, increasing the efficiency of oil extraction from existing sources is crucial, to avoid waste and the drilling of new wells. The purpose of this work was to add diffusive and dispersive terms to the Buckley-Leverett equation in order to incorporate extra phenomena in the temporal evolution between the water-oil and oil-water transitions in the pipeline. For this, the modified Buckley-Leverett equation was discretized via essentially weighted non-oscillatory schemes, coupled with a three-stage Runge-Kutta and a fourth-order centered finite difference methods. Then, computational simulations were performed and the results showed that new features emerge in the transitions, when compared to classical simulations. For instance, the dispersive term inhibits the diffusive term, adding oscillations, which indicates that the absorption of the fluid by the porous medium occurs in a non-homogeneous manner. Therefore, based on research such as this, decisions can be made regarding the replacement of the porous medium or the insertion of new components to delay the replacement.

Enhancement of MAD/MIR phasing at low resolution and a new procedure for automatic phase extension

To achieve de novo protein structure determination of challenging cases, multi-wavelength anomalous diffraction(MAD) and multiple isomorphous replacement(MIR) phasing can be powerful tools to obtain low-resolution initial phases from heavy-atom derivative datasets, then phase extension is needed against high-resolution data to obtain accurate structures.In this context, we propose a direct-methods procedure here that could improve the initial low-resolution MAD/MIR phase quality.And accordingly, an automated process for extending initial phases to high resolution is also described.These two procedures are both implanted in the newly released IPCAS pipeline.Three cases are used to perform the test, including one set of 4.17 ? MAD data from a membrane protein and two sets of MAD/MIR data with derivatives truncated down to 6.80 ? and 6.90 ?, respectively.All the results have shown that the initial phases generated from the direct-methods procedure are better than that from the conventional MAD/MIR methods.The automated phase extensions for the latter two cases starting from 6.80 ? to 3.00 ? and 6.90 ? to 2.80 ? are proved to be successful, leading to complete models.This may provide convenient and reliable tools for phase improvement and phase extension in difficult low-resolution tasks.

Calculation of phase transformation latent heat based on cooling curves in end-quench test and its application in nickel-based superalloy

To obtain the phase transformation latent heat corresponding to different cooling rates with low test workload and cost,the Newton thermal analysis method and the improved Newtonian thermal analysis method were discussed based on the cooling curve obtained in the end-quench test.The validity of two methods was given by the latent heat calculation of 45^(#) steel.The results show that the relative error of latent heat is 5.20%through the improved Newtonian thermal analysis method,which is more accurate than the Newtonian thermal analysis method.Furthermore,the latent heat release of phase transformation of the self-designed CSU-A1 powder metallurgy nickel-based superalloy increases from 4.3 to 12.29 J/g when the cooling rate decreases from 50.15 to 33.40℃/min,because there is more sufficient time for the alloy microstructure to complete the phase transformation process when the cooling rate is smaller.

FEM simulation and experimental verification of temperature field and phase transformation in deep cryogenic treatment

Combining with the low temperature material properties and the boiling heat transfer coefficient of specimen immersed in the liquid nitrogen, a numerical model based on metallo-thermo-mechanical couple theory was established to reproduce the deep cryogenic treatment （DCT） process of a newly developed cold work die steel Cr8Mo2SiV （SDC99）. Moreover, an experimental setup for rapid temperature measurement was designed to validate the simulation results. The investigation suggests that the differences in temperature and cooling rate between the surface and core of specimen are very significant. However, it should be emphasized that the acute temperature and cooling rate changes during DCT are mainly concentrated on the specimen surface region about 1/3 of the sample thickness. Subjected to DCT, the retained austenite of quenched specimen continues to transform to martensite and finally its phase volume fraction reduces to 2.3%. The predicted results are coincident well with the experimental data, which demonstrates that the numerical model employed in this study can accurately capture the variation characteristics of temperature and microstructure fields during DCT and provide a theoretical guidance for making the reasonable DCT procedure.

PEG-combined liquid phase synthesis and electrochemical properties of carbon-coated Li_3V_2(PO_4)_3

The carbon-coated monoclinic Li3V2(PO4)3(LVP) cathode materials were successfully synthesized by liquid phase method using PEG as reducing agent and carbon source. The effects of relative molecular mass of PEG on the properties of Li3V2(PO4)3/C were evaluated by X-ray diffraction(XRD), scanning electron microscope(SEM) and electrochemical performance tests. The SEM images show that smaller size particles are obtained by adding larger and smaller PEGs. The electrochemical cycling of Li3V2(PO4)3/C prepared by both PEG200 and PEG20 k has a high initial discharge capacity of 131.1 mA·h/g at 0.1C during 3.0-4.2 V, and delivers a reversible discharge capacity of 123.6 m A·h/g over 30 cycles, which is better than that of other samples. The improvement in electrochemical performance is caused by its improved lithium ion diffusion coefficient for the macroporous morphology, which is verified by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).

RESEARCH ON METHOD TO CALCULATE VELOCITIES OF SOLID PHASE AND LIQUID PHASE IN DEBRIS FLOW

Velocities of solid phase and liquid phase in debris flow are one key problem to research on impact and abrasion mechanism of banks and control structures under action of debris flow. Debris flow was simplified as two-phase liquid composed of solid phase with the same diameter particles and liquid phase with the same mechanical features. Assume debris flow was one-dimension two-phase liquid moving to one direction, then general equations of velocities of solid phase and liquid phase were founded in two-phase theory. Methods to calculate average pressures, volume forces and surface forces of debris flow control volume were established. Specially, surface forces were ascertained using Bingham＇s rheology equation of liquid phase and Bagnold＇s testing results about interaction between particles of solid phase. Proportional coefficient of velocities between liquid phase and solid phase was put forward, meanwhile, divergent coefficient between theoretical velocity and real velocity of solid phase was provided too. To state succinctly before, method to calculate velocities of solid phase and liquid phase was obtained through solution to general equations. The method is suitable for both viscous debris flow and thin debris flow. Additionally, velocities every phase can be identified through analyzing deposits in-situ after occurring of debris flow. It is obvious from engineering case the result in the method is consistent to that in real-time field observation.

Preparation and Characterization of Sodium Sulfate/Silica Composite as a Shape-stabilized Phase Change Material by Sol-gel Method

A sodium sulfate （NaeSO4）/silica （SiO2） composite was prepared as a shape-stabilized solid-liquid phase change material by a sol-gel procedure using Na2SiO3 as the silica source. Na2SO4 in the composite acts as a latent heat storage substance for solid-liquid phase change, while SiO2 acts as a support material to provide structural strength and prevent leakage of melted NazSO4. The microstructure and composition of the prepared composite were characterized by the N2 adsorption, transmission electron microscope （TEM）, scanning electron microscope （SEM）, Fourier transform infrared spectroscopy （FTIR） and X-ray diffraction. The results show that the prepared Na2SOJSiO2 composite is a nanostructured hybrid of NazSO4 and SiO2 without new substances produced during the phase change. The macroscopic shape of the NazSO4/SiO2 composite after the melting and freezing cycles does not change and there is no leakage of Na2SO4. Determined by differential scanning calorimeter （DSC） analysis, the values of phase change latent heat of melting and freezing of the prepared NazSO4/SiO2 （50%, by mass） composite are 82.3 kJ.kg i and 83.7 kJ.kg-1, and temperatures of melting and freezing are 886.0 ℃ and 880.6 ℃, respectively. Furthermore, the Na2SOJSiO2 composite maintains good thermal energy storage and release ability even after 100 cycles of melting and freezing. The satisfactory thermal storage performance renders this composite a versatile tool for high-temperature thermal energy storage.

An improvement to the simulation of phase-change heat-transfer during soil freezing and thawing

A new variable time step method,which is called the backwards calculating time step method,is presented in this paper.It allows numerical simulation of soil freezing and thawing while avoiding "phase change missing and overflowing".A sensitive heat capacity model is introduced through which the calculation errors are analyzed.Then the equation using the self-adjusted time step is presented and solved using finite differences.Through this equation,the time needed for a space cell to reach the phase change point temperature is calculated.Using this time allows the time step to be adjusted so that errors caused by "phase change missing and overflowing" are successfully eliminated.Above all,the obvious features of this method are an accelerated rate for adjusting the time step and simplifing the computations.An actual example proves that this method can accurately calculate the temperature fields during soil freezing and thawing.It is an improvement over traditional methods and can be widely used on complicated multi-dimensional phase change problems.

Effect of microalloying on wettability and interface characteristics of Zr-based bulk metallic glasses with W substrate

The infiltration casting method is widely employed for the preparation of ex-situ composite materials.However,the production of composite materials using this method must necessitates a comprehensive understanding of the wettability and interface characteristics between the reinforcing phase and the bulk metallic glasses(BMGs).This work optimized the composition of Zr-based BMGs through microalloying methods,resulting in a new set of Zr-based BMGs with excellent glass-forming ability.Wetting experiments between the Zr-based BMGs melts and W substrates were conducted using the traditional sessile drop method,and the interfaces were characterized utilizing a scanning electron microscope(SEM)equipped with energy dispersive X-ray spectroscopy(EDS).The work demonstrates that the microalloying method substantially enhances the wettability of the Zr-based BMGs melt.Additionally,the incorporation of Nb element impedes the formation of W-Zr phases,but the introduction of Nb element does not alter the extent of interdiffusion between the constituent elements of the amorphous matrix and W element,indicating that the influence of Nb element on the diffusion of individual elements is minute.

Phase equilibrium data prediction and process optimizationin butadiene extraction process

In response to the lack of reliable physical parameters in the process simulation of the butadiene extraction,a large amount of phase equilibrium data were collected in the context of the actual process of butadiene production by acetonitrile.The accuracy of five prediction methods,UNIFAC(UNIQUAC Functional-group Activity Coefficients),UNIFAC-LL,UNIFAC-LBY,UNIFAC-DMD and COSMO-RS,applied to the butadiene extraction process was verified using partial phase equilibrium data.The results showed that the UNIFAC-DMD method had the highest accuracy in predicting phase equilibrium data for the missing system.COSMO-RS-predicted multiple systems showed good accuracy,and a large number of missing phase equilibrium data were estimated using the UNIFAC-DMD method and COSMO-RS method.The predicted phase equilibrium data were checked for consistency.The NRTL-RK(non-Random Two Liquid-Redlich-Kwong Equation of State)and UNIQUAC thermodynamic models were used to correlate the phase equilibrium data.Industrial device simulations were used to verify the accuracy of the thermodynamic model applied to the butadiene extraction process.The simulation results showed that the average deviations of the simulated results using the correlated thermodynamic model from the actual values were less than 2%compared to that using the commercial simulation software,Aspen Plus and its database.The average deviation was much smaller than that of the simulations using the Aspen Plus database(>10%),indicating that the obtained phase equilibrium data are highly accurate and reliable.The best phase equilibrium data and thermodynamic model parameters for butadiene extraction are provided.This improves the accuracy and reliability of the design,optimization and control of the process,and provides a basis and guarantee for developing a more environmentally friendly and economical butadiene extraction process.

Dual-phase coexistence enables to alleviate resistance drift in phase-change films

The amorphous phase-change materials with spontaneous structural relaxation leads to the resistance drift with the time for phase-change neuron synaptic devices. Here, we modify the phase change properties of the conventional Ge_2Sb_2Te_5(GST) material by introducing an SnS phase. It is found that the resistance drift coefficient of SnS-doped GST was decreased from 0.06 to 0.01. It can be proposed that the origin originates from the precipitation of GST nanocrystals accompanied by the precipitation of SnS crystals compared to single-phase GST compound systems. We also found that the decrease in resistance drift can be attributed to the narrowed bandgap from 0.65 to 0.43 eV after SnS-doping. Thus, this study reveals the quantitative relationship between the resistance drift and the band gap and proposes a new idea for alleviating the resistance drift by composition optimization, which is of great significance for finding a promising phase change material.

Frost heaving and crack initiation characteristics of tunnel rock mass in cold regions under low-temperature degradation

Water freezing in rock fractures causes volumetric expansion and fracture development through frost heaving.This study introduces a novel analytical model to investigate how uneven freezing force and surrounding rock pressure influence fracture initiation,based on mass conservation,elasticity,and water-ice phase transition principles.A model for rock fracture initiation considering freezing temperature,uneven freezing expansion,in-situ stress,and lateral pressure was proposed based on fracture mechanics.Equations for stress intensity factors were developed and validated using the phase field method.The effects of rock elastic modulus anisotropy and critical fracture energy density on fracture initiation were also discussed.The results show that the values of KI and KII exhibit an upward trend as the freezing temperature,uneven expansion,in-situ stress,and lateral pressure increase.The uneven freezing expansion has the most significant influence on KI and KII values among these parameters.As the uneven freezing expansion coefficient increases to 0.5,the fracture initiation mode shifts from tensile fracture to shear fracture.As the lateral pressure coefficient increases to 1,the fracture initiation mode shifts from tensile fracture to shear fracture.Rock elastic modulus anisotropy causes fractures to propagate in a clockwise direction,forming a'butterfly'pattern.Critical fracture energy density an isotropy causes counterclockwise deviation in propagation direction,resulting in branching paths and an'H'-shaped pattern.

Analysis on high-temperature oxidation and growth stress of iron-based alloy using phase field method

High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.

Numerical Simulation Study of Oil-Water Emulsion Separation in an Ultrasonic Field:Effect of Coupling between Acoustic and Flow Field Parameters

In this study,the separation and coalescence of oil-in-water emulsions are explored in an ultrasonic field using the lattice Boltzmann method.By simulating the propagation of ultrasonic waves,this study focuses on examining the effects of acoustic wave frequency,the ratio of oil to water components,and the aspect ratio of the boundary on the emulsification and separation processes of oil-water mixtures.The following conclusions are drawn.①Frequency affects the speed of oil droplet separation,leading to an increase in droplet size over time.Larger droplets are found near the source,while smaller droplets are distributed throughout the wave web.②As the boundary aspect ratio increases,the emulsification efficiency of the droplets weakens,and the system takes longer to stabilize.③Emulsions with a higher component of oil can better resist acoustic waves.④At the same acoustic frequency,longer wavelength ultrasonic fields promote the formation of uniformly distributed,smaller oil droplets,which is beneficial to the storage of emulsions.These numerical simulation results offer insights for optimizing conditions for oil-in-water separation and serve as a numerical reference for the study of oil-in-water emulsion separation in ultrasonic environments.

Controllable Synthesis of Mixed-Phase TiO_2 with Small Anatase and Rutile Particle and Its Enhanced Photocatalytic Activity

Mixed-phase TiO_2 photocatalysts with small particle size of anatase and rutile(~5 nm) have been successfully synthesized using hydrothermal method. The effects of curing temperature and curing time before the hydrothermal treatment on the crystalline phase, the phase composition, and the particle size of TiO_2 were investigated by the X-ray diffraction spectroscopy(XRD) and the transmission electron microscopy(TEM), respectively. It was found that the anatase and rutile phase contents in the TiO_2 particles were successfully controlled by simply adjusting the curing temperature and the curing time. More importantly, the particle size of both anatase and rutile is small in the mixed-phase TiO_2 particles. The photocatalytic activity of TiO_2 was evaluated by the degradation of Rhodamine B(Rh B) in aqueous solution. The Ti O2 with phase junction formed by anatase and rutile exhibited higher separation rate between the photo-induced electrons and holes, which was confirmed by the surface photovoltage(SPV) spectra, and at the same time exhibited the higher photocatalytic degradation on Rh B than pure anatase-phase TiO_2. Moreover, it was found that TiO_2 with 83% of anatase and 17% of rutile showed a highest photocatalytic activity among the mixed-phase TiO_2 samples.

Morphological evolution and growth kinetics of Kirkendall voids in binary alloy system during deformation process-Phase field crystal simulation study

The formation and growth of Kirkendall voids in a binary alloy system during deformation process were investigated byphase field crystal model.The simulation results show that Kirkendall voids nucleate preferentially at the interface,and the averagesize of the voids increases with both the time and strain rate.There is an obvious coalescence of the voids at a large strain rate whenthe deformation is applied along the interface under both constant and cyclic strain rate conditions.For the cyclic strain rate appliedalong the interface,the growth exponent of Kirkendall voids increases with increasing the strain rate when the strain rate is largerthan1.0×10-6,while it increases initially and then decreases when the strain rate is smaller than9.0×10?7.The growth exponent ofKirkendall voids increases initially and then decreases gradually with increasing the length of cyclic period under a square-waveform constant strain rate.

A Forecasting Model of Vector Similarity in Phase Space for Flood and Drought over the Huanghe-Huaihe-Haihe Plain in China

To represent well the characteristics of temporal and spatial distributions, chart of 3-dekad moving total precipitation is proposed in this paper first. Then this kind of chart is expanded in terms of Chebyshev polynomial at irregular grids, and the quantitative representation of precipitation is got. Finally the Chebyshev coefficients are forecasted by using the forecasting method of vector similarity in phase space proposed by Zhou (1992). Using above mentioned procedures temporal and spatial distributions of precipitation over the Huanghe-- Huaihe-- H aihe Plain in China are forecasted.

PHASE EXTENSION AND STRUCTURE ANALYSIS BY THE MAXIMUM ENTROPY METHOD

Excellent results are obtained in structure analysis with jew phases of structure factors by the maximum-entropy method (MEM) for CaGaN PbCO3 and ReBe22 single crystals. The computation time and memory space are minimized by symmetry operations so that structure analysis by the MEM can be carried out with a personal computer.