Two-phase Region Research Articles

Generalized thermodynamic modeling of hydrogen storage tanks for truck application

Hydrogen-driven heavy-duty trucks are a promising technology for reducing CO2 emissions in the transportation sector. Thus, storing hydrogen efficiently onboard is vital. The three available or currently developed physical hydrogen storage technologies (compressed gaseous, subcooled liquid, and cryo-compressed hydrogen) are promising solutions. For a profound thermodynamic comparison of these storage systems, a universally applicable model is required. Thus, this article introduces a generalized thermodynamic model and conducts thermodynamic comparisons in terms of typical drive cycle scenarios. Therefore, a model introduced by Hamacher et al. [1] for cryo-compressed hydrogen tanks is generalized by means of an explicit model formulation using the property cv2P from REFPROP [2], which is understood as a generic specific isochoric two-phase heat capacity. Due to an implemented decision logic, minor changes to the equation system are automatically made whenever the operation mode or phase of the tank changes. The resulting model can simulate all three storage tank systems in all operating scenarios and conditions in the single- and two-phase region. Additionally, the explicit model formulation provides deeper insights into the thermodynamic processes in the tank. The model is applied to the three physical hydrogen storage technologies to compare drive cycles, heat requirement, dormancy behavior, and optimal usable density. The highest driving ranges were achieved with cryo-compressed hydrogen, however, it also comes with higher heating requirements compared to subcooled liquid hydrogen.

Numerical simulation on the effect of non-condensable gas on direct contact condensation of steam jet in a narrow pipe

A numerical model was developed to investigate the phenomenon of direct contact condensation involving steam-air jet in subcooled waterflow. This study encompassed a comprehensive exploration of the influence exerted by non-condensable gas from a multi-faceted perspective. These aspects included an examination of gas plume shape, distribution of air mass fraction, variation in axial thermodynamic parameters, the local heat transfer coefficient, and the local condensation rate. It was observed that the presence of non-condensable gas had the effect of extending the penetration length of the steam plume. Notably, the non-condensable gas was predominantly concentrated in proximity to the gas-liquid interface, a phenomenon that introduced hindrances to both heat and mass transfer processes. A detailed analysis of axial thermodynamic parameters further unveiled an intriguing trend. As the air content increased, the expansion of gas plume weakened, subsequently leading to a reduction in the condensation rate. This resulted in diminished pressure fluctuations in the two-phase mixing region. Moreover, the presence of non-condensable gas was shown to curtail the local heat transfer coefficient and the local condensation rate at the interface. This observation offered valuable insights into the underlying mechanisms responsible for the protraction of the gas plume.

Improved microstructure and mechanical properties by in-situ formed nano borides of high-Nb TiAl composites under ultrasound in the solid-liquid two-phase region

To form in situ nano-borides in the solid-liquid two-phase region, Ti46 A l8Nb2·6C0.8TaxB alloys were prepared under ultrasound to improve the microstructural and mechanical properties. The morphology and distribution of borides and the characteristics of lamellar colonies were observed with scanning and transmission electron microscopy and X-ray diffraction; these analyses revealed the influence of borides on microstructural evolution and improved strength and plasticity. The borides that form are elongated and spherical. As the B content increases, the borides gradually spheroidise, and nano-borides precipitate on the lamellar phase. There are a large number of dislocations around the borides to form stacking faults and dislocation walls. The average size of the lamellar colonies decreases from 26.9 to 19.3 μm. The increase in boride nucleation sites as the B content increases and ultrasound-mediate breaking of primary borides are the reasons for forming B27-type borides. The increase in nucleation particles refines the lamellar colony. The compressive strength increases from 2058 to 2299 MPa, and the strain increases from 25.2% to 32.3% when the addition of B increases from 0% to 1.2%. The significantly improved mechanical properties are due to uniformly distributed nano-borides that hinder the movement of dislocations to form stacking faults and dislocation walls and refinement of the lamellar colonies.

Polymeric surfactants at liquid–liquid interfaces: Dependence of structural and thermodynamic properties on copolymer architecture

Polymeric surfactants are amphiphilic molecules with two or more different types of monomers. If one type of monomer interacts favorably with a liquid, and another type of monomer interacts favorably with another, immiscible liquid, then polymeric surfactants adsorb at the interface between the two liquids and reduce the interfacial tension. The effects of polymer architecture on the structural and thermodynamic properties of the liquid–liquid interface are studied using molecular simulations. The interface is modeled with a non-additive binary Lennard-Jones fluid in the two-phase region of the phase diagram. Block and gradient copolymer surfactants are represented with coarse-grained, bead-spring models, where each component of the polymer favors one or the other liquid. Gradient copolymers have a greater concentration at the interface than do block copolymers because the gradient copolymers adopt conformations partially aligned with the interface. The interfacial tension is determined as a function of the surface excess of polymeric surfactant. Gradient copolymers are more potent surfactants than block copolymers because the gradient copolymers cross the dividing surface multiple times, effectively acting as multiple individual surfactants. For a given surface excess, the interfacial tension decreases monotonically when changing from a block to a gradient architecture. The coarse-grained simulations are complemented by all-atom simulations of acrylic-acid/styrene copolymers at the chloroform-water interface, which have been studied in experiments. The agreement between the simulations (both coarse-grained and atomistic) and experiments is shown to be excellent, and the molecular-scale structures identified in the simulations help explain the variation of surfactancy with copolymer architecture.

Structural evolution and redox chemistry of robust ternary layered oxide cathode for sodium-ion batteries

Nickel/manganese-based O3-type layered oxides have been widely deemed to be a family of promising cathode materials for sodium-ion batteries (SIBs) owing to the large theoretical specific capacity and low manufacturing cost, but being usually challenged by unsatisfied electrochemical performance. In this study, a novel ternary layered oxide NaNi1/2Mn1/4Ti1/4O2 is reported as a robust high-capacity cathode for SIBs, and its structural evolution and redox chemistry in the potential range of 1.5–4.2 V (vs Na+/Na) are carefully explored by coupling X-ray diffraction technique, X-ray photoelectron spectroscopy, transmission electron microscope, FTIR spectroscopy, and galvanostatic measurement. Experimental facts reveal that the material undergoes multiple structural phase evolutions involving two solid-solution regions and one two-phase region based on the redox chemistry of Ni2+/Ni3+ and Ni3+/Ni4+ couples. It exhibits excellent electrochemical performance with a high reversible capacity of 145.2 mAh g−1 and an impressive capacity retention of 85.1% after 100 cycles due to the unique structure with robust ternary composition and stable coating interface. The coating interface is mainly related with formation of the amorphous carbonate layer at preparation step and the CEI film containing alkoxy group during the first charge. In addition, initial Na extraction from the material suffers from a “potential jump” phenomenon owing to severe electrochemical polarization caused by large interfacial impedance and charge-transfer impedance. This work provides new insights on interfacial change, structural evolution and redox reaction of high-capacity O3-type layered oxide cathode during Na extraction/insertion.

Crack reduction in laser powder bed fusion of MnAl(C) using graphene oxide coated powders

MnAl(C) is a promising candidate as a rare earth free magnet. When processing MnAl(C) in laser powder bed fusion (L-PBF) the high cooling rates can retain the high temperature ε-phase which can then be annealed at low temperatures to yield the ferromagnetic τ-phase. However, MnAl(C) has been shown to be difficult to print using L-PBF and the material is prone to severe cracking. In this study, we have investigated how the addition of a graphene oxide (GO) coating on the powders can affect the processability of MnAl(C) and properties of the printed parts. MnAl(C) powders were coated with 0.2 wt.% GO using a wet-chemical process. The addition of GO reduced crack formation in the printed parts, and also influenced the degree of ⟨001⟩\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\langle {001} \\rangle$$\\end{document} texture along the build direction. After printing, densities of 93% and 87% could be achieved for the reference and 0.2 wt.% GO, respectively. Furthermore, a 35% reduction of cracking was calculated from image analysis, comparing printed samples produced from coated and non-coated powders. Both powders formed mostly the ε-phase but some two-phase regions with a mix of γ- and ε-phase could be observed in the as-printed parts, but seemed to be more prominent in the uncoated reference samples and could also be linked to cracks. The τ-phase together with smaller amounts of secondary phases was obtained after heat treatment at 560 °C for 5 min for both samples. Vibrating sample magnetometry was used to measure the magnetic properties, the reference had a remanence of 33 Am2/kg and a coercivity of 139 kA/m, and the 0.2 wt.% GO sample showed a similar remanence of 30 Am2/kg and coercivity of 130 kA/m. These results show that GO coating is a viable method to reduce detrimental cracking in L-PBF MnAl without reducing the magnetic performance of the material.

Effect of Non-Uniform Concentration Field on TiN Growth in Two-Phase Region with Electropulsing

Ti microalloyed steel has the advantages of high toughness and high strength, but it is easy to form TiN particles with large dimensions at high temperatures, which is harmful to the metal and seriously affects the quality of cast billets. In this paper, by analyzing the kinetic characteristics of Ti element diffusion in the two-phase region with electropulsing, the influence mechanism of pulsed current on the growth of TiN particles in the two-phase region is investigated. The results show that the pulsed current improves the flow rate of Ti and N elements in the molten steel, reduces the concentration of Ti in the liquidoid along the solid-liquid interface, and the more the current intensity, the more obvious the impact; in addition, with the increase of the flow rate, the diffusion flux of Ti elements is also gradually improved. Therefore, the pulsed current promotes the diffusion of Ti elements by improving the concentration field of Ti and other solute elements in the two-phase region, thus inhibiting the growth of TiN.

Hierarchical structure growth across different length scales in the two-phase coexistence region of myristic acid Langmuir monolayers: correlation of static and dynamic heterogeneities.

We investigated the hierarchical structure growth of myristic acid monolayers at the air-water interface across different length scales in the two-phase coexistence region of the first order liquid expanded (LE)-liquid condensed (LC) phase transition. A combined study of surface pressure-area (π-A) isotherm measurements with Brewster angle microscopy (BAM) observations was done at different temperatures. At the nanometer scale, the analysis of the π-A isotherm by application of a thermodynamic cluster equation allowed us to obtain the π dependence of cluster size (cluster distribution) in the LE-LC coexistence region. The cluster distributions showed a peak at the midpoint pressure of the transition. At higher temperature the larger nanocluster size was obtained at the transition midpoint. At the micrometer scale, BAM showed that LC domains have characteristic textures depending on the temperature. At low temperature domain density was lower and the average size of circular domains was larger. A large number of circular domains revealed a virtual boojum texture from the initial to the late stage of the transition. At the final stage some circular domains coalesced to form larger circular stripe domains and others coalesced to each other without the formation of stripe domains, finally resulting in a uniform texture over the entire water surface. At high temperature the domain texture was predominantly uniform, and a small number of domains only included straight line defects from the intermediate to the late stage of the transition. All domains coalesced to each other without the development of any texture including the stripe, different from the case at low temperature. The phase boundary line tension is highly likely to play a key role for understanding the hierarchical growth and coarsening (coalescence) process in the LE-LC transition between the different length scales from the nanometer to the micrometer scale consistently together.

Ispitivanje uticaja temperature austenitizacije na mehaničke, toplotne i strukturne osobine 51CrV4 čelika

In this paper, emphasis is placed on studying the influence of quenching temperature (austenitization) on the mechanical, thermal, and structural properties of 51CrV4 chrome-vanadium steel. Generally, 51CrV4 steel is often categorized as spring steel; however, in recent years, it has been increasingly used in the production of different types of tools, so it can also be categorized as tool steel. To obtain better-quality tools, this steel is subjected to various types of heat treatment, which usually include normalizing, quenching, and medium-temperature tempering. In this investigation, the samples were austenitized at different temperatures, ranging from 780 °C to 920 °C, and subsequently quenched in oil. After quenching, the samples were tempered at a temperature of 350 °C for 2 hours. The goal was to monitor the influence of austenitizing temperature on hardness, thermal conductivity, and microstructure by subjecting the samples to characterization after the applied heat treatment. The results showed that with an increase in the austenitization temperature, the hardness values gradually increase, reach a maximum, and then decrease, regardless of the type of heat treatment. On the other hand, thermal conductivity values show the opposite trend. After the characterization, it was concluded that by choosing a low austenitization temperature (770 °C), samples would be cooled from the two-phase region (a+g), which produces lower hardness values. However, choosing a high austenitization temperature (920 °C) would lead to austenite grain growth and surface decarburization, again lowering hardness values.

Mechanism of boundary bubble drag reduction of Couette flow in nano-confined domain

Bubble drag reduction technology is of great significance in improving the propulsion efficiency of underwater vehicle and reducing the comprehensive energy consumption during navigation. Bubble drag reduction is a highly effective method of reducing the frictional resistance encountered by large ships and underwater vehicles during navigation. It exhibits excellent stability in drag reduction, and has advantages such as environmental friendliness, adaptability to various flow environments, and suitability for all underwater components of ships. Therefore, it is greatly significant to conduct in-depth research on bubble drag reduction and its underlying mechanism. In this work, the flow characteristics and the boundary bubble drag reduction mechanism of gas-liquid Couette flow in parallel wall nanochannels are studied by molecular dynamics method, and the influences of surface wettability, wall roughness, and gas concentration on boundary slip velocity and bubble drag reduction effect are analyzed. The results indicate that the bubble drag reduction effect is enhanced with the increase of boundary slip velocity. In the gas-liquid two-phase flow region, with the increase of shear velocity, the lateral deformation of boundary adsorbed bubble and boundary slip velocity increase, thus enhancing the bubble drag reduction effect. The increase of solid-gas interaction strength and gas concentration can lead to the enrichment of gas atoms near the wall, improve the bubble spreading characteristics on the wall, and thus increase the slip velocity of the solid-liquid interface. The wall roughness can change the spreading characteristics of bubble, affect the boundary slip velocity, and then change the drag reduction effect of the fluid-solid interface. As the rib height increases, gas atoms accumulate in the grooves between ribs and the adsorption quantity of gas atoms on the upper surface of the rib decreases, which leads to the decrease of the boundary slip velocity of the solid-liquid interface and ultimately reduces the drag reduction effect. The research results will provide important theoretical guidance for implementing the boundary drag reduction technology in large ships and underwater vehicles.

Phase relations in the Nd2O3-Fe2O3 system: Structure and magnetic properties of perovskite NdFeO3 ceramics

The phase relations in the Nd2O3-Fe2O3 system at 1300 and 1400 ?C were studied in the whole concentration range by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The isothermal cross-sections of the Nd2O3-Fe2O3 phase diagram at 1300 and 1400 ?C are characterized by the presence of three singlephase (A-Nd2O3, NdFeO3, Fe2O3) and two two-phase (A-Nd2O3 + NdFeO3, NdFeO3 + Fe2O3) regions. The composition corresponding to the perovskite phase is 51mol% Nd2O3 - 49mol% Fe2O3. In the next step, the investigation was focused on this composition. Nanocrystalline NdFeO3 powders with perovskite structure were obtained by the Pechini method and heterogeneous precipitation from nitrate solutions. The influence of the production method on the microstructure, morphology and magnetic properties of the NdFeO3 nanopowders was studied. According to XRD, SEM and TEM, the synthesized perovskite NdFeO3 is single-phase with a particle size of 60-90 nm. The morphology of powder particles primarily depends on the synthesis method. The powder showed ferromagnetic behaviour and had saturation magnetization 0.8 and 0.81 emu/g.

РАСЧЕТ ТЕПЛОЕМКОСТЕЙ СЛОЖНЫХ ОКСИДОВ

The technology for producing a complex oxide is based on knowledge of its thermophysical characteristics, in particular, heat capacity. To calculate its temperature dependence, a previously proposed thermodynamic model of a two-phase local equilibrium region was used. The numerical values of the parameters and coefficients of the model are obtained from a comparison of the theoretical curve with the experimental data given in the literature. It is shown that the construction relations adequately describe experimental arrays of various complex oxides not only in the limited temperature ranges studied, but also make it possible to calculate the heat capacities of oxides in the range from 0 K to their melting point. The need for additional experimental study of the transformation in neodymium orthoniobate in the region of 1000 K is indicated.

Quantitative turbidimetric characterization of stabilized complex coacervate dispersions.

Stabilizing complex coacervate microdroplets is desirable due to their various applications, such as bioreactors, drug delivery vehicles, and encapsulants. Here, we present quantitative characterization of complex coacervate dispersion stability inferred by turbidimetry measurements. The stability of the dispersions is shown to be modulated by the concentrations of comb polyelectrolyte (cPE) stabilizers and salt. We demonstrate cPEs as effective stabilizers for complex coacervate dispersions independent of the chemistry or length of the constituent polyelectrolytes, salts, or preparation routes. By monitoring the temporal evolution of dispersion turbidity, we show that cPEs suppress microdroplet coalescence with minimal change in microdroplet sizes over 48 hours, even at salt concentrations up to 300 mM. The number density and average microdroplet size are shown to be controlled by varying the cPE and salt concentrations. Lastly, turbidity maps, akin to binodal phase maps, depict an expansion of the turbid two-phase region and an increase in the salt resistance of the coacervates upon the introduction of cPEs. The coacervate salt resistance is shown to increase by >3×, and this increase is maintained for up to 15 days, demonstrating that cPEs impart higher salt resistance over extended durations.

Cosolvent incorporation modulates the thermal and structural response of PNIPAM/silyl methacrylate copolymers.

Polymers functionalized with inorganic silane groups have been used in wide-ranging applications due to the silane reactivity, which enables formation of covalently-crosslinked polymeric structures. Utilizing stimuli-responsive polymers in these hybrid systems can lead to smart and tunable behavior for sensing, drug delivery, and optical coatings. Previously, the thermoresponsive polymer poly(N-isopropyl acrylamide) (PNIPAM) functionalized with 3-(trimethoxysilyl)propyl methacrylate (TMA) demonstrated unique aqueous self-assembly and optical responses following temperature elevation. Here, we investigate how cosolvent addition, particularly ethanol and N,N-dimethyl formamide (DMF), impacts these transition temperatures, optical clouding, and structure formation in NIPAM/TMA copolymers. Versus purely aqueous systems, these solvent mixtures can introduce additional phase transitions and can alter the two-phase region boundaries based on temperature and solvent composition. Interestingly, TMA incorporation strongly alters phase boundaries in the water-rich regime for DMF-containing systems but not for ethanol-containing systems. Cosolvent species and content also alter the aggregation and assembly of NIPAM/TMA copolymers, but these effects depend on polymer architecture. For example, localizing the TMA towards one chain end in 'blocky' domains leads to formation of uniform micelles with narrow dispersities above the cloud point for certain solvent compositions. In contrast, polydisperse aggregates form in random copolymer and PNIPAM homopolymer solutions - the size of which depends on solvent composition. The resulting optical responses and thermoreversibility also depend strongly on cosolvent content and copolymer architecture. Cosolvent incorporation thus increases the versatility of inorganic-functionalized responsive polymers for diverse applications by providing a simple way to tune the structure size and optical response.

The influence of rolling at subcritical temperatures on the low-carbon steel structure and properties formation

Problem. In practice, the rolling of a low-carbon steel sheet due to significant heat losses ends in the austenite – ferrite two-phase structure region, which leads to the metal heterogeneous structure formation, that decreases the sheet steel properties of the and its ability to be drawn.
 Adverse temperature conditions characteristic of traditional hot rolling technology can be prevented by metal processing in the single-phase ferrite structure region below the critical point Ar1. Rolling of a thin sheet in the subcritical temperature range will ensure obtaining a uniform metal structure, which determines the level of its mechanical properties, as well as the quality of stamped parts
 Goal. The purpose of the work is study the rolling modes influence at subcritical temperatures on the low-carbon steel structure and properties formation.Methodology. The microstructure of 08ps steel samples was studied using a metallographic and electron microscope JSM-840 with a "Link-860/|500" microanalysis system, the 08ps steel samples cross-section fine structure was studied using an electron microscope JEM - 200Сx. The metal mechanical properties complex was determined by standard tensile test methods.Results. The 08ps steel structure and properties after rolling at subcritical temperatures were studied. The comparative analysis of the fine structure of the initial blank and deformed samples of low-carbon steel was carried out. It was established that changes are observed in the structure of the deformed samples and the initial blank, which indicate the polygonization and recrystallization processes implementation and do not provide the of metal mechanical properties level provided for by DSTU 2834-94.Originality. Тhe thin structure of a 08ps steel sheet deformed in the subcritical temperature range with air cooling was studied. The development differs in the temperatures of the beginning and end of rolling, as well as the cooling rate in the post-deformation period. It allows to expand theoretical ideas about the patterns of 08ps deformed steel structure formation and to use them in practice. Practical value. The results of the work can be applied in determining rational processing modes, which involve rolling at subcritical temperatures, to increase the complex metal properties and obtain high-quality parts by cold stamping.

Understanding How the Suppression of Insertion-Induced Phase Transitions Leads to Fast Charging in Nanoscale LixMoO2.

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO2, a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO2, the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

Thermoresponsive Polymers under Pressure with a Focus on Poly(N-isopropylacrylamide) (PNIPAM).

Pressure is a key variable in the phase behavior of responsive polymers, both for applications and from a fundamental point of view. In this feature article, we review recent developments, particularly applications of neutron techniques such as small-angle neutron scattering (SANS) and quasi-elastic neutron scattering (QENS), across the temperature-pressure phase diagram. These are complemented by kinetic SANS experiments following pressure jumps. In the prototype system poly(N-isopropylacrylamide) (PNIPAM), QENS revealed the pressure-dependent characteristics of hydration water around the lower critical solution temperature transition. The size, water content, and inner structure of the mesoglobules formed in the two-phase region depend strongly on pressure, as shown by SANS. Beside these changes at the phase transition, the mesoglobule formation at low pressure is determined by kinetic factors, namely the formation of a polymer-rich, rigid shell, which hampers further growth by coalescence. At high pressure, in contrast, the growth proceeds by diffusion-limited coalescence without any kinetic hindrance. The disintegration of the mesoglobules evolves either via chain release from their surface or via swelling, depending on the osmotic pressure of the water. Moreover, we report on the profound influence of pressure on the cononsolvency effect. In the temperature-pressure frame, the one-phase region is hugely expanded upon the addition of the cosolvent methanol. SANS experiments unveil the enthalpic and entropic contributions to the effective Flory-Huggins interaction parameter between the segments and the solvent mixture. QENS experiments demonstrate an increase in polymer associated water with pressure, whereas methanol is released. Correspondingly, the solvent phase becomes enriched in methanol, providing a mechanism for the breakdown of cononsolvency at a high pressure. Finally, we outline future opportunities for high-pressure studies of thermoresponsive polymers, with a focus on neutron methods.

Aging Aware Battery Operation and State of Health Evaluation in Energy Storage Systems

The sources of performance loss in lithium-ion batteries are many and can vary widely dependent on battery usage [1]. Understanding these mechanisms and coupling usage patterns to dominating degradation phenomena can allow smarter use and longer lifetime of the batteries. This can especially bring value in stationary applications, as the usage patterns have different characteristics and second life applications for batteries are considered as well [2].Driven by the development of battery electric vehicles, batteries with higher power and energy densities have revolutionized the market. The lifetime of the batteries is another crucial criterion. A significant amount of work has been performed studying the degradation phenomena and evaluating stress factors. High/low potentials, high C-rates, and temperature deviations from room temperature should be avoided to keep the degradation rate low [3-5]. The power demand for batteries in stationary energy storage systems is lower than vehicle applications and some of these extremes could therefore be avoided [6]. Finding optimal sizing of the batteries, with high energy throughput and low degradation rate, is therefore of interest. The energy delivered by the storage system is further part of the power trading market, hence motivating the need to accurately correlate delivered energy and battery performance loss from different services.In this work the degradation of commercial 18650-type Nickel Cobalt Manganese (NCM)/Graphite cells, in stationary applications is studied. Different scenarios including type of service, sizing, and second-life applications are studied through accelerated testing. The work expands upon a previous study focusing on the degradation effects of combining services [7]. The degradation analysis involves different techniques such as the capacity evolution (Figure 1), electrochemical impedance spectroscopy (EIS), as well as changes in the electrodes revealed by differential voltage analysis (DVA). The electrode balancing, capacity and cell polarization is evaluated in terms of battery state-of-health and important characteristics highlighted. Preliminary results show no additional degradation introduced by scaling the current amplitude 50%. A clear relationship between state-of-charge window and degradation rate is shown, where the graphite two-phase regions are of importance. These regions are also affected by the electrode slippage observed in the DVA. Strategies for battery characterization and operation strategies for second-life applications will be further investigated.Figure 1. Preliminary results of the normalized capacity development of the cells in the study, as an averaged value of duplicate cells. Frequency regulation (FR) is a mild cycle around 50% SOC, current maximum 1C. FR_high has a current maximum of 1.5C. Peak shaving (PS) is a 1C constant current cycling between 22-78% SOC, PS_low has a 0.5C constant current cycling. FRPS is the two cycles combined.References Birkl, C. R.; Roberts, M. R.; McTurk, E.; Bruce, P. G.; Howey, D. A., Degradation diagnostics for lithium ion cells. Journal of Power Sources 2017, 341, 373-386. Martinez-Laserna, E.; Gandiaga, I.; Sarasketa-Zabala, E.; Badeda, J.; Stroe, D. I.; Swierczynski, M.; Goikoetxea, A., Battery second life: Hype, hope or reality? A critical review of the state of the art. Renewable and Sustainable Energy Reviews 2018, 93, 701-718. Baure, G.; Dubarry, M., Battery durability and reliability under electric utility grid operations: 20-year forecast under different grid applications. Journal of Energy Storage 2020, 29. Keil, P.; Schuster, S. F.; Wilhelm, J.; Travi, J.; Hauser, A.; Karl, R. C.; Jossen, A., Calendar Aging of Lithium-Ion Batteries. Journal of The Electrochemical Society 2016, 163 (9), A1872-A1880. Ecker, M.; Nieto, N.; Käbitz, S.; Schmalstieg, J.; Blanke, H.; Warnecke, A.; Sauer, D. U., Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries. Journal of Power Sources 2014, 248, 839-851. Dubarry, M.; Devie, A.; Stein, K.; Tun, M.; Matsuura, M.; Rocheleau, R., Battery Energy Storage System battery durability and reliability under electric utility grid operations: Analysis of 3 years of real usage. Journal of Power Sources 2017, 338, 65-73. Ohrelius, M.; Berg, M.; Wreland Lindström, R.; Lindbergh, G., Lifetime Limitations in Multi-Service Battery Energy Storage Systems. Energies 2023, 16 (7). Figure 1

Quantitative analysis of microstructure evolution, stress partitioning and thermodynamics in the dynamic transformation of Fe-14Ni alloy

Dynamic transformation (DT) of austenite (γ) to ferrite (α) in the hot deformation of various carbon steels was widely investigated. However, the nature of DT remains unclear due to the lack of quantitative analysis of stress partitioning between two phases and the uncertainty of local distribution of substitutional elements at the interface in multi-component carbon steels used in the previous studies. Therefore, in the present study, a binary Fe-Ni alloy with α + γ duplex microstructure in equilibrium was prepared and isothermally compressed in α + γ two-phase region to achieve a quantitative analysis of microstructure evolution, stress partitioning, and thermodynamics during DT. γ to α DT during isothermal compression and α to γ reverse transformation on isothermal annealing under unloaded condition after deformation were accompanied by Ni partitioning. The lattice strains during thermomechanical processing were obtained via in-situ neutron diffraction measurement, based on which the stress partitioning behavior between γ and α was discussed by using the generalized Hooke's law. A thermodynamic framework for the isothermal deformation in solids was established based on the basic laws of thermodynamics, and it was shown that the total Helmholtz free energy change in the deformable material during the isothermal process should be smaller than the work done to the deformable material. Under the present thermodynamic framework, the microstructure evolution in the isothermal compression of Fe-14Ni alloy was well explained by considering the changes in chemical free energy, plastic and elastic energies, and the work done to the material. In addition, the stabilization of the soft α phase in Fe-14Ni alloy by deformation was rationalized since the γ to α transformation decreased the total Helmholtz free energy by decreasing the elastic and dislocation energies.

Microstructure evolution and its effect on the impact toughness of the Ti-Al-V-Mo-Zr alloy tube

Titanium alloys are widely used in the petrochemical industry owing to their excellent overall performance. In this study, a high-temperature solution treatment in the two-phase region was proposed, with a slow cooling rate resulting in the successful partial globularization of lamellar α microstructure, achieving an extruded Ti-Al-V-Mo-Zr alloy tube elongation increase of 69% and impact toughness increase of 51%. The kinking of lamellar α microstructure promoted its continuous globularization by increasing misorientation. Consequently, the elongation and impact toughness of Ti-Al-V-Mo-Zr alloy tubes could be greatly improved by tuning the microstructure to a mix of coarse equiaxed and lamellar α microstructures, the improved strength being attributed to the secondary α phase (αs) obtained using the proposed method and aging. The results of this study can be expected to provide guidance for the fabrication of highly ductile titanium-alloy oil-drilling tubes.Graphical abstract