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Controlling the MC and M2C carbide precipitation in Ferrium® M54® steel to achieve optimum ultimate tensile strength/fracture toughness balance
Highlights: • Small and uniformly distributed undissolved Ti-rich MC carbides control the grain size during the austenitization • High austenitizing temperature (1060°C) allows the full dissolution of the coarse carbides (size > several of 100nm) • Intensive nanometer-sized carbides precipitate during tempering thanks to the high supersaturation of alloying elements • Coarse carbides dissolution and nanometer-size carbides precipitation is necessary to achieve high UTS/K{sub I}C balance - Abstract: Ferrium® M54® exhibits an excellent UTS/K{sub 1C} balance allowing its application in aeronautical structures. This steel belongs to the Co-Ni UHS steels family with M{sub 2}C nanometer-size carbide precipitation during tempering. These steels provide very high strength with a very good fracture toughness thanks to the M{sub 2}C fine precipitation during tempering, but also because coarse particles are dissolved during austenitizing without grain coarsening. The goal of this article is to identify the different carbide populations in M54®. A small addition of Ti in M54® forms a Ti-rich MC carbide precipitation that is stable at high temperature. Consequently, during austenitization at 1060 °C, all other types of coarse carbides are dissolved in the matrix without grain coarsening. As a very small part of the initial carbon content is needed to form MC carbides, efficient and intensive nanometric M{sub 2}C carbide precipitation takes place during tempering, leading to very high final strength. Due to this double precipitation of carbides in M54®, the steel achieves an outstanding UTS/K{sub 1C} balance.
Effect of secondary phase particles on thermal stability of ultra-fine grained Mg-4Y-3RE alloy prepared by equal channel angular pressing
Highlights: • UFG structure with grain size of ~340 nm was achieved in WE43 by ECAP. • Fine Mg{sub 5}RE particles are responsible for microstructural stability up to 280 °C. • Segregation of Y and RE solutes in grain boundaries was observed. • Hardening at 200–280 °C was observed due to segregation and precipitation. • Effect of particles dissolution and grain growth on softening was discussed. - Abstract: As-cast magnesium alloy WE43, containing yttrium and rare earth elements, was processed by equal channel angular pressing (ECAP). The processing led to a significant grain refinement together with a massive precipitation of the secondary phase particles. Thermal stability of the ultra-fine grain (UFG) structure together with microstructural changes due to exposure to elevated temperatures were studied by several complementary techniques in the temperature range of 160–500 °C. It was found that UFG structure consisting of grains with size of ~340 nm and high density of Mg{sub 5}RE particles is stable up to 280 °C for 1 h of annealing. Moreover, only negligible change of the microstructure occurred after annealing for 16 h at 250 °C. Excellent thermal stability of UFG structure was caused by fine Mg{sub 5}RE particles, which suppressed the grain growth. Exceeding the limit of thermal stability of these particles above 280 °C resulted in material softening. Moreover, statistically significant hardening of the UFG material occurred in the temperature range of 200–280 °C. Segregation of yttrium and rare earth elements and eventually precipitation at grain boundaries was proved to be responsible for observed hardening by in-situ and ex-situ transmission electron microscope and positron annihilation spectroscopy analysis. Finally, individual effect of particles dissolution and grain growth on the material softening was investigated and discussed.
Influence of temperature on the lattice misfit and elastic moduli of a Ni based single crystal superalloy with high volume fraction of γ′ phase
Highlights: • The variation of the lattice misfit with temperature in a Ni based single-crystal superalloy with high volume fraction of γ' phase was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. • When the temperature was higher than 1100 °C, the γ' phase obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of the lattice misfit. • The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. • When the temperature exceeded 1100 °C, the difference of elastic moduli of γ and γ′ phases increased with rising temperature was attributed to the elastic modulus of γ phase decreased significantly. - Abstract: The variation of the lattice parameter with temperature in a Ni based single-crystal superalloy with high volume fraction of γ′ phase IC32 was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. The effects of the temperature, especially the ultra-high temperature (beyond 1100 °C), on lattice misfit, elastic moduli, γ′ volume fraction and composition of γ, γ′ phases were investigated in this study. The results show that the absolute value of lattice misfit first increased and then decreased with increasing temperature and reached the maximum of 0.53% at 1100 °C. When the temperature was higher than 1100 °C, the γ′ precipitate obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of lattice misfit. The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. Moreover, when the temperature was above 1100 °C, the elastic moduli of the γ phase and alloy decreased significantly, while this phenomenon was not observed in the γ′ phase.
Effect of intermediate annealing time on microstructure, texture and mechanical properties of Al-Mg-Si-Cu alloy
Highlights: • Long intermediate annealing time could be beneficial to the improvement of deep drawability. • Long intermediate annealing time could give rise to more particles with a larger average size. • As intermediate annealing time increases, strength will change and it has no positive correlation with annealing time, • A particle dissolution model is proposed to illustrate the variation of the strengths with intermediate annealing time. - Abstract: The effect of intermediate annealing time on the microstructure, texture and mechanical properties of Al-Mg-Si-Cu alloys was studied by mechanical properties, microstructure and texture characterization in the present study. The results show that the intermediate annealing time has some influence on the microstructure, recrystallization texture, and final mechanical properties. After the pre-aging treatment and natural aging treatment (T4P treatment), in contrast to the sheet with short intermediate annealing time, the sheet with long intermediate annealing time possesses higher plastic strain ratio r value. Strength has no positive correlation with annealing time, and when applying the annealing time of 16 h, the strength is highest. Before solution treatment, the sheet with long intermediate annealing time has more particles with a larger average size, compared with the sheet with short intermediate annealing time. After solution treatment, they possess the similar recrystallization equiaxed grain structure and recrystallization texture. The sheet with short intermediate annealing time is comprised of Cube{sub ND} {001} <310>, Goss {110}<001> and P {011}<122> orientations, while the sheet with long intermediate annealing time possesses weak texture including Cube{sub ND} {001}<310>, Goss {110}<001> and {015}<751> orientations. Finally, a particle dissolution model during solution treatment is proposed to explain the variation of strength with annealing time.
Mechanism of chlorine-induced stress corrosion cracking of two 304 SS heats in simulated marine environment through in situ X-ray tomography and diffraction: Role of deformation induced martensite and crack branching
In this work, In-situ synchrotron x-ray tomography and diffraction experiments were conducted on two heats of 304SS undergoing chlorine-induced stress-corrosion-cracking (CISCC) in a simulated marine environment. The role of deformation induced martensite on CISCC was investigated through diffraction analysis where no significant amount of martensite was found to form during CISCC, indicating that it may not play a significant role in affecting the process. Tomography combined with stress-intensity analysis revealed the influence of stress-intensity on branching types with single crack growth, micro-branching, and macro-branching. Post experimental electron microscopy characterization revealed the presence of FeCl 2 , CrCl 2 , and NiCl 2 ·6H 2 O compounds at the crack, which infers a dissolution mechanism during the experiment. A dissolution mechanism highlighting the synergy between stress and corrosion was proposed to explain chlorine-induced stress-corrosion-cracking and crack branching.
Iron acquisition and mineral transformation by cyanobacteria living in extreme environments
Iron is an essential micronutrient for most living organisms, including cyanobacteria. These microorganisms have been found in Earth's driest polar and non-polar deserts, including the Atacama Desert, Chile. Iron-containing minerals were identified in colonized rock substrates from the Atacama Desert, however, the interactions between microorganisms and iron minerals remain unclear. In the current study, we determined that colonized gypsum rocks collected from the Atacama Desert contained both magnetite and hematite phases. A cyanobacteria isolate was cultured on substrates consisting of gypsum with embedded magnetite nanoparticles. Transmission electron microscopy imaging revealed a significant reduction in the size of magnetite nanoparticles due to their dissolution, which occurred around the microbial biofilms. Concurrently, hematite was detected, likely from the oxidation of the magnetite nanoparticles. Higher cell counts and production of siderophores were observed in cultures with magnetite nanoparticles suggesting that cyanobacteria were actively acquiring iron from the magnetite nanoparticles. Magnetite dissolution and iron acquisition by the cyanobacteria was further confirmed using large bulk magnetite crystals, uncovering a survival strategy of cyanobacteria in these extreme environments.
Shale-fluid interactions during forced lmbibition and flow-back
One way to minimize the need for disposal of flow-back waters produced during the hydraulic fracturing of unconventional reservoirs is, potentially, to recycle these fluids by recovering and re-injecting them during hydraulic fracturing of nearby new wells. These flow-back waters contain, however, large concentrations of dissolved salts. During hydraulic fracturing of unconventional reservoirs, a well may undergo extended shut-in periods, following the initial hydraulic-fracture stimulation. The concern here, therefore, is that the salts dissolved in the re-injected flow-back waters may precipitate in the subsurface, thus promoting scale formation; or alternately, because of their high salinity, these same fluids may cause the dissolution of various minerals present in the subsurface. Large divalent cations (e.g., Ca²⁺, Ba²⁺ and Sr²⁺) and anions (e.g., CO3²⁻ and SO4²) may chemically interact with and cause the swelling of clay fractions, thus blocking pores in certain pore size ranges. All these phenomena (i.e., scale formation, clay swelling, minerals dissolution) can influence the petrophysical properties of the formation, including its permeability, porosity, contact angle, etc. One way to potentially overcome some of these technical challenges, is to pre-treat these flow-back waters, prior to re-injection (e.g., via chemical precipitation, followed by membrane filtration) in order to remove unwanted salts. However, such pre-treatment is costly, and the degree of salt removal needed to prevent formation damage is important in determining the economic viability of flow-back water recycle via re-injection. A key focus of this work, therefore, is to study the impact that the injection of flow-back waters, that have undergone varying degrees of pre-treatment and clean-up, will have on the flow-through characteristics of a tight-gas reservoir, particularly of the Marcellus Shale formation. To do so, we have carried-out forced-imbibition experiments with shale samples from various depths in the Marcellus formation, whose properties span high to low ranges of TOC, clay content and matrix permeabilities. We have studied the forced-imbibition characteristics, at an injection pressure of 24,233 kPa (3500 psig), of various flow-back fluids into shale cores saturated with methane at a pore pressure of 17,338 kPa (2500 psig) and a confining stress of 27,680 kPa (4000 psig). Following the forced imbibition experiments, we analyzed the cores for potential changes in permeability and porosity. Quantification of the ion content of the injected and recovered fluids was also performed using Ion Chromatography (IC). The IC analysis of the recovered fluids indicates substantial interactions and geochemical reactions between the invading fluids and the shale cores. The injection of flow-back fluids shows significant impact on the flow-through characteristics, with untreated flow-back fluids, which have the highest cation and anion content, also exhibiting the highest observable reductions in permeability (>90%).
Delamination recycling of multilayer plastic films: Solvent-assisted separation pathways and recovery of solid polyolefins
Multilayer plastic films are excellent packaging materials due to the bound layers of multiple polymers, with each different polymer contributing to the film properties. Desirable properties lead to continuously growing demand for multilayer films. Multilayer plastic films are typically single-use and, as such, their increased production and disposal have led to waste management problems. Multilayer films are not currently recyclable primarily due to the multiple bound polymers. This work advances delamination as a recycling process to separate and sequester valuable polymers from multilayer films, facilitating the incorporation of these polymers into the circular economy. We effect delamination in a physical process that preserves targeted polymers as solid film, hence retaining their embodied energy. This work documents three different pathways of inducing delamination of multilayer films, with appropriate solvents disrupting adhesion between adjacent layers or dissolving a minor component of the film in less than an hour and at temperatures below 90°C, and where all initial polyethylene is maintained in its solid form throughout the process and is recovered at high purity. Solvent-based delamination is exemplified on commercial multilayer films with majority polyethylene (PE), and polyethylene terephthalate (PET) or ethylene vinyl alcohol copolymer (EVOH) or nylon also present. Solvent-based delamination is an energy-efficient and environmentally friendly recycling process that improves upon dissolution-precipitation recycling, since delamination involves very little dissolution and no precipitation, and is superior to pyrolysis which breaks down the polymers, while delamination keeps polymer chains intact. Furthermore, delamination recycling can contribute to the sustainable use of multilayer films as they continue to protect our food and medicine.
Controlling the corrosion resistance of multi-principal element alloys
Multi-principal element alloys (MPEAs) offer the possibility of many degrees of freedom in the choice of alloying elements to produce either single phase solid solutions or more complex multiphase microstructures. Large ranges of material properties have been observed for MPEAs and mastery of the selection of elements and their compositions can enable novel combinations of properties not possible in traditional alloys. From the aqueous corrosion perspective, optimization of phase stability, control of heterogeneities, passive film identity and its protectiveness, as well as substrate properties such as metal-metal bond strength and activation energy associated with dissolution, can all be controlling factors governed by alloy composition and structure. These factors can mediate the electrochemical reactions controlling spontaneous corrosion. The quest for superior properties based on well-informed element choice is suggested as a path forward guiding MPEA formulations for corrosion performance. However, gaps in fundamental knowledge exist regarding (a) the specific functions of each element, (b) the behavior of elements in unusual combinations, and (c) the formation of complex protective oxides. These issues currently hold back progress in optimization of corrosion properties.
Reductive biomining of pyrite by methanogens
Pyrite (FeS 2 ) is the most abundant iron sulfide mineral in Earth’s crust. Until recently, FeS 2 has been considered a sink for iron (Fe) and sulfur (S) at low temperature in the absence of oxygen or oxidative weathering, making these elements unavailable to biology. However, anaerobic methanogens can transfer electrons extracellularly to reduce FeS 2 via direct contact with the mineral. Reduction of FeS 2 occurs through a multistep process that generates aqueous sulfide (HS – ) and FeS 2 -associated pyrrhotite (Fe 1-x S). Subsequent dissolution of Fe 1-x S provides Fe(II) (aq) , but not HS – , that rapidly complexes with HS – (aq) generated from FeS 2 reduction to form soluble iron sulfur clusters [nFeS (aq) ]. Cells assimilate nFeS (aq) to meet Fe/S nutritional demands by mobilizing and hyperaccumulating Fe and S from FeS 2 . As such, reductive dissolution of FeS 2 by methanogens has important implications for element cycling in anoxic habitats, both today and in the geologic past.
γ-Taxilin temporally regulates centrosome disjunction in a Nek2A-dependent manner
Highlights: • γ-Taxilin co-localizes with Nek2A at the centrosome during interphase. • γ-Taxilin interacts with Nek2A in yeast two-hybrid and pull-down assays. • γ-Taxilin protein expression levels decrease at the onset of mitosis. • γ-Taxilin depletion induces immature splitting of centrosomes. • The immature splitting of centrosomes induced by γ-taxilin depletion depends on Nek2A. Never in mitosis A-related kinase 2A (Nek2A), a centrosomal serine/threonine kinase, is involved in mitotic progression by regulating the centrosome cycle. Particularly, Nek2A is necessary for dissolution of the intercentriole linkage between the duplicated centrosomes prior to mitosis. Nek2A activity roughly parallels its cell cycle-dependent expression levels, but the precise mechanism regulating its activity remains unclear. In this study, we found that γ-taxilin co-localized with Nek2A at the centrosome during interphase and interacted with Nek2A in yeast two-hybrid and pull-down assays and that γ-taxilin regulated centrosome disjunction in a Nek2A-dependent manner. γ-Taxilin depletion increased the number of cells with striking splitting of centrosomes. The precocious splitting of centrosomes induced by γ-taxilin depletion was attenuated by Nek2A depletion, suggesting that γ-taxilin depletion induces the Nek2A-mediated dissolution of the intercentriole linkage between the duplicated centrosomes nevertheless mitosis does not yet begin. Taken together with the result that γ-taxilin protein expression levels were decreased at the onset of mitosis, we propose that γ-taxilin participates in Nek2A-mediated centrosome disjunction as a negative regulator through its interaction with Nek2A.
Evolution in the structure of akaganeite and hematite during hydrothermal growth: an in situ synchrotron X-ray diffraction analysis
Synchrotron X-ray diffraction was used to monitor the hydrothermal precipitation of akaganeite ( β -FeOOH) and its transformation to hematite (Fe 2 O 3 ) in situ . Akaganeite was the first phase to form and hematite was the final phase in our experiments with temperatures between 150 and 200 °C. Akaganeite was the only phase that formed at 100 °C. Rietveld analyses revealed that the akaganeite unit-cell volume contracted until the onset of dissolution, and subsequently expanded. This reversal at the onset of dissolution was associated with a substantial and rapid increase in occupancy of the Cl site, perhaps by OH - or Fe 3+ . Rietveld analyses supported the incipient formation of an OH-rich, Fe-deficient hematite phase in experiments between 150 and 200 °C. The inferred H concentrations of the first crystals were consistent with “hydrohematite.” With continued crystal growth, the Fe occupancies increased. Contraction in both a- and c -axes signaled the loss of hydroxyl groups and formation of a nearly stoichiometric hematite.
Long-Term Cyclability of NCM-811 at High Voltages in Lithium-Ion Batteries: an In-Depth Diagnostic Study
High-nickel layered oxides, such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM-811), offer higher energy density than their low-nickel counterparts at a given voltage and are gaining major traction in automotive lithium-ion batteries for electric vehicles. Besides high-Ni content, higher charging voltages above 4.3 V vs Li + /Li boost the energy and represent another focus in battery development. Here, we investigate the long-term cyclability of NCM-811 in graphite pouch cells over 1000 deep cycles between 2.5–4.2, 2.5–4.4, and 2.5–4.5 V through a suite of sensitive characterization techniques. The NCM-811 full cells show severely deteriorated cyclability with higher charging voltages, from 78% at 4.2 V to 52 and 32% at 4.4 and 4.5 V, respectively. At 4.2 V, minor parasitic electrolyte oxidation as well as cathode Li/Ni mixing and cracking are revealed after cycling, while transition-metal dissolution and surface reconstruction into rock-salt NiO are virtually undetectable. At 4.4 and 4.5 V, transition-metal dissolution and crossover to the anode become much more pronounced and a primary contributor to the capacity fade, while significant surface NiO formation causes substantial voltage polarization, which is less noticeable at 4.2 V. Meanwhile, more severe electrolyte oxidation, Li/Ni mixing, and particle pulverization exacerbate the voltage and capacity fade. Finally, these results outline distinct challenges for stable high-Ni layered oxide cathodes in high-voltage Li-ion batteries.
Location-Dependent Cobalt Deposition in Smartphone Cells upon Long-Term Fast-Charging Visualized by Synchrotron X-ray Fluorescence
In this work, we investigate the transition-metal dissolution of the layered cathode material LiCoO 2 upon repeated fast-charging of three smartphone batteries from different manufacturers using synchrotron micro X-ray fluorescence (μ-XRF). Using this spatially resolved technique, dissolution of Co and subsequent location-dependent deposition on the anode are observed. μ-XRF mapping of selected parts of the anode electrode sheets, such as electrode folds and edges of the jelly roll, reveals the difference in the way Co is deposited on specific regions of the anode electrode. While some folds show no depositions, edges of the anode show gradually accumulating Co depositions. Furthermore, careful quantification of the dissolved Co reveals that the capacity loss scales with the amount of deposited Co on the anode, that is, total Co loss from within the cathode. Soft X-ray absorption spectroscopy of the Co depositions on the anode shows that Co is mainly deposited in a reduced 2 + state. While optimization of the fast-charging protocol mitigates Li plating on the anode, no significant difference in the amount of deposited Co can be observed between an optimized and a nonoptimized fast-charging algorithm.
Toward the Understanding of the Reaction Mechanism of Zn/MnO2 Batteries Using Non-alkaline Aqueous Electrolytes
Zn/MnO 2 systems using non-alkaline aqueous electrolytes have attracted tremendous interest as rechargeable aqueous Zn ion batteries due to their safety and high specific capacities. Despite their promising electrochemical performance, however, their reaction mechanism has remained elusive. Here in this paper, we examined the structural evolution of cryptomelane α-MnO 2 cathode by ex situ transmission electron microscopy after electrochemical testing using two different non-alkaline aqueous Zn electrolytes with acetate and triflate salts of different pH values. We have discovered that the systems tested in both electrolytes exhibit a dissolution–deposition reaction mechanism through dissolution–deposition of Mn 2+ ions from/on the cathodes with a display of similar discharge/charge product formation. We have also found that the cell tested using the acetate electrolyte shows evidence of structural irreversibility that might contribute to its rapid capacity degradation. This finding offers an important insight into optimizing the cathode design for enhanced electrochemical function of aqueous Zn/MnO 2 batteries.
First-Principles Examination of Multiple Criteria of Organic Solvent Oxidative Stability in Batteries
Oxidative instability of the liquid electrolyte at or near battery cathode oxide surfaces has significant detrimental effects on batteries. Organic solvent molecules are often the fuel and precursors of such degradation processes, releasing electrons and protons that react with cathode oxides and electrolyte anions. These reactions contribute to cathode–electrolyte interphase (CEI) film formation, transition-metal ion dissolution, and phase transformation of the surface regions of the cathode. Here we apply density functional theory calculations to examine four criteria of oxidative stability (oxidation potential, hydrogen removal energies, and initial reactivity on two types of oxide facets) using four different solvent/additive molecules (ethylene carbonate, fluoroethylene carbonate, 1,3-dioxolane, and dimethyl ether). The ranking of molecular stability differs with each criterion. Surprisingly, the all-oxygen-terminated basal planes of layered oxides exhibit lower reaction barriers than spinel surface facets with exposed transition-metal cations, especially for ether solvents; the calculations also suggest basal planes contribute to the dissolution of transition-metal ions. Further, the structure–degradation relation complexity underscores the challenge of understanding the function of the CEI but also offers a guide to future degradation-mitigation strategies including facet engineering. Our predictions and models help establish a framework for future studies relevant to high-voltage conditions.
Spatiotemporal and Statistical Mapping of Transition Metal Equilibria in Alkaline Media
Transition metal dissolution and redeposition (D/R) kinetics in alkaline media play a critical role in various chemical and electrochemical processes. Competitive reaction kinetics between different transition metals can modulate individual metal behavior in these processes. To date, these phenomena have remained largely unmeasured, and even when captured, they are difficult to statistically characterize due to their dynamic nature, simultaneous occurrence, and spatially heterogeneous nature. Here, in this study, we develop a statistical analysis framework based on in situ and operando X-ray fluorescence microscopy (XFM) to investigate the relative D/R kinetics of multiple transition metals in alkaline media. By employing statistical analysis, we quantify the spatial distribution of D/R species and assess the rate at which the system reaches equilibrium under varying reaction conditions. We show that pH does not simply change the rate of dissolution and redeposition, but reorganizes the cross-element kinetic correlations among Ni, Fe, and Mn and accelerates the spatial equilibration of D/R events, as quantified through correlation analysis, reaction-rate estimation, probability function distributions, and texture-based monitoring statistics. Additionally, we demonstrate how modifying the solvent environment can influence D/R kinetics, providing a pathway for tuning materials synthesis and process optimization. Our study offers valuable insights into the complex interplay between different transition metals and provides a reliable statistical framework for spatial analysis of diverse imaging data sets, enabling deeper extraction of latent information across multiple modalities.