Selective Dissolution Research Articles

Investigation of dissolution behavior and surface integrity in electrochemical machining of nickel-based superalloys

ABSTRACT Dissolution behavior and surface integrity during the electrochemical machining (ECM) of nickel-based superalloys are vital for the performance of components. This study examines IN718, 718Plus, and Rene 65 alloys focusing on material removal mechanisms, surface morphology, intergranular corrosion, three-dimensional profiles, surface roughness, microhardness, and residual stresses. The results indicated that as the current density increased, the MRR of all three alloys increased linearly, while the current efficiency initially fluctuated before stabilizing. At low current densities, selective dissolution and intergranular corrosion resulted in rough surfaces for the alloys examined. In contrast, higher current densities produced smooth and uniform surfaces for these alloys. After electrochemical treatment, the surface microhardness of all alloys was reduced, and there was a slight decrease in residual stresses as well. These findings support the development of more precise and effective strategies for achieving higher surface integrity in the ECM of nickel-based superalloys.

A Universal Ternary Solvent System of Surface Passivator Enables Perovskite Solar Cells with Efficiency Exceeding 26.

Surface passivation is a vital approach to improve the photovoltaic performance of perovskite solar cells (PSCs), in which the passivator solvent is an inevitable but easy-ignored factor on passivation effects. Herein, a universal ternary solvent system of surface passivators is proposed through comprehensively considering the solubility and selective perovskite dissolution of the solvent to maximize the passivation effect. Tetrahydrothiophene 1-oxide (THTO) is selected as the passivation promoter by comparing the binding energy with perovskite and the ability to distort the perovskite lattice among various aprotic polar solvent molecules, which can facilitate the passivator's reaction with perovskite and achieve sufficient passivation on perovskite surface. Besides, chlorobenzene (CB) is used as the diluting agent to minimize the amount of isopropanol (IPA), inhibiting the additional solvent-induced defects. As a result, the planar PSCs achieve a power conversion efficiency (PCE) of 26.05%, (certificated 25.66%). Besides, the unencapsulated devices exhibit enhanced stability, which can maintain 95.23% and 95.68% of their initial PCE after 2000h of storage in ambient air and 800h of light-soaking in N2-glovebox. Moreover, this ternary solvent system also exhibits a well applicability and reliability in different passivator such as PEAI, BAI, and so on.

Healable, Recyclable, and Upcyclable Gel Membranes for Efficient Carbon Dioxide Separation

AbstractIonic liquids (ILs) are prized for their selective dissolution of carbon dioxide (CO2), leading to their widespread use in ionogel membranes for gas separation. Despite their advantages, creating sustainable ionogel membranes with high IL contents poses challenges due to limited mechanical strength, leakage risks, and poor recyclability. Herein, we leverage copolymerized and supramolecularly bound ILs to develop ionogel membranes with high mechanical strength, zero leakage, and excellent self‐healing and recycling capabilities. These membranes exhibit superior ideal selectivity for gas separation compared to other reported ionogel membranes, achieving a CO2/nitrogen selectivity of 61.7 and a CO2/methane selectivity of 24.6, coupled with an acceptable CO2 permeability of 186.4 Barrer. Additionally, these gas separation ionogel membranes can be upcycled into ionic skins for sensing applications, further enhancing their utility. This research outlines a strategic approach to molecularly engineer ionogel membranes, offering a promising pathway for developing sustainable, high‐performance materials for advanced gas separation technologies.

Nanoporous Cu-based amorphous alloys prepared by selective dissolution in acidic media

Abstract Functional nanoporous materials are considered a significant category of nanostructured materials that exhibit distinct characteristics like high surface area, porosity, and improved mass transport properties. These qualities render them suitable for a wide range of applications including catalysis, energy storage, biomedical fields, and electrochemical sensors. Dealloying or laser-induced technologies are the primary methods employed to fabricate such nanoporous materials. Dealloying is a dependable top-down approach used to produce hierarchical, disordered nanoporous materials with customizable pore sizes in the range of a few nanometers. The process of dealloying involves the selective elimination or dissolution of one or more elements from an alloy through a corrosion mechanism, using various dealloying techniques, such as chemical, electrochemical, liquid metal, or vapor phase dealloying. In the present study, copper-based amorphous metallic ribbons (Cu75Ni6Sn5P10Ga4) were initially manufactured using the melt-spinning method. The Cu-based amorphous ribbons were structurally investigated by X-ray diffraction and thermal analysis. Subsequently, the ribbons were subjected to a dealloying treatment, using an acidic solution to selectively dissolve the nickel from their composition and to obtain a nanoporous structure. The microstructure and chemical composition of the ribbons before and after the dealloying process were investigated using scanning electron microscopy (SEM), combined with energy-dispersive X-ray spectroscopy. The dealloying process performed in 1 M H2SO4 solution at 25 °C for 60 minutes leads to a large number of nanopores, uniformly distributed onto the surface of the Cu-based ribbons.

CORROSION BEHAVIOUR OF MAGNESIUM ALLOYS NZ30K AND NZ30K ALLOYED WITH SILVER IN THE MODEL SOLUTION OF THE OSTEOSYNTHESIS PROCESS

The corrosion behaviour of magnesium alloys NZ30K and NZ30K alloyed with 0.1 wt.% silver in Ringer's Locke solution has been studied, since their components are not toxic to the human body and do not cause clinical complications in the treatment of bone fractures, and silver has antibacterial properties inherent in antibiotics. It has been found that the Ecor potential of the silver-alloyed NZ30K sample was -1.57V during the first 100 seconds of testing, but then it intensively shifted to the positive side to -1.54V within 512 seconds at a rate of 0.051 mV/s, which decreased to 0.014 mV/s after the next 1000 seconds, and a stationary value of the potential Ecor on the sample has been recorded. The sample to uniform general corrosion has been subjected, and the improvement of its potential Ecor during its corrosion study was due to the most intense selective dissolution of magnesium, which has the most negative value of the standard potential among the alloy components, and the enrichment of its surface with Zn, Nd, Zr, Ag, which have a positive value of the standard potential. This trend contributed to a decrease in the rate of general corrosion and made it impossible to develop local corrosion. The NZ30K alloy alloyed with 0.1 wt.% silver is recommended for further potentiodynamic and volumetric corrosion studies to justify its selection as a structural material for the production of biodegradable implants in osteosynthesis.

Electrochemical Production of Tungsten Oxides from Wc-Co Carbide-Type Pseudo-Alloy Waste

Electrochemical research is devoted to the development of a method of processing secondary raw materials containing tungsten in the form of a pseudoalloy of the carbide type WC–Co in sulfate solutions. The target processing products are: powders of tungsten oxides of lower oxidation states, which can be reduced to metallic tungsten with lower costs. Using the methods of linear and cyclic voltammetry, it was established that the selective dissolution of the cobalt component of the pseudoalloy in the studied solutions occurs at potentials more positive than 0.2 V, carbon is removed from the working electrode at a potential > 0.8 V. At the same time, tungsten is oxidized to the higher oxide WO3. It was determined that in sulfuric acid, with an increase in its concentration from 1 to 5 mol∙dm-3, the current density decreases, which is associated with the formation of a solid surface layer of tungsten oxide on the surface of the anode, which passivates the surface. It was established experimentally that when adding 1 mol∙dm-3 of H2SO4 hexamine (C6H12N4) with a concentration of 0.9 mol∙dm-3 to a solution, it is possible to block the process of formation of a passivating film and obtain powders of tungsten oxides of lower oxidation states.

Mineralogical examination of biomass ashes: A preliminary study for potassium enrichment and phosphoric acid (H3PO4) production

In this study, biomass fly ash was investigated and determined by XRD to be predominantly langbeinite, aphthitalite, sylvine, apatite and hydroxyapatite. An alkaline leaching study was carried out on the material in a glass reactor at l/s ratio 4 temperature 600C at pH 12.85 and after drying was analyzed by ICP. The crystal structure composition of K2SO4 72.28% and potassium content of 33.47%(w/w) was recovered. The elemental transformations in this leaching process were: K 74.16%, Mg 0.55% was found to be 0.8%. It was found that a minimum of 4.84 g H2SO4 per 100 g fly ash was required to precipitate the Ca(OH)2 migrated into the liquid solution and the overall leaching efficiency was found to be 29.85%. In the alkaline leaching process, potassium was found to be easily recovered from each biomass ash. By adding 40 g H2SO4/100 g biomass waste remaining after leaching, a phosphorus recovery of 74.9% was observed. In this preliminary study, unsatisfactory results were obtained in obtaining the industry standard H3PO4. The reason for this is that the Al, Mg and K in the fly ash are subject to selective dissolution as a result of working at high pH in the alkaline leaching process.

A novel process for recovering LNCM battery cathode material using cryolite-based electrolyte through selective dissolution - Acid leaching - Coprecipitation

Around the world the number of scrapped lithium-ion batteries (LIBs), which are rich in valuable elements worthy of recycling, is increasing. In this study, a method using cryolite-based electrolyte to recycle cathode materials from spent lithium nickel-cobalt-manganese oxide (LNCM) batteries is proposed. Firstly, a molten cryolite-based electrolyte is used to decompose the microstructure of spent LIB cathode material, releasing valuable lithium element into the electrolyte, which can be used in aluminum electrolysis industry. As nickel-cobalt-manganese oxides have low solubilities in the cryolite-based electrolyte, they sink to the bottom of the molten electrolyte, which is then cooled down, forming an upper and lower layer. Lithium element can be quickly and conveniently separated from nickel-cobalt-manganese oxides, which are enriched in the lower layer of the electrolyte. Then, a hydrochloric acid solution is used to leach nickel-cobalt-manganese components from the lower layer of the cryolite-based electrolyte. The effects of acid concentration, liquid-solid ratio, and temperature on the leaching process are investigated through single factor experiments. The highest leaching rates of nickel, cobalt, and manganese elements reach 99.47%, 98.94%, and 98.27%, respectively. By using NaOH + NH3·H2O to adjust the pH of the leaching solution, coprecipitation of nickel, cobalt, and manganese elements occur, producing a hydroxide precursor and resulting in recovery rates of over 99%. The recycled hydroxide precursor and new lithium source are then roasted to regenerate an LNCM811 cathode material, which has a layered microstructure and is assembled into a battery. Test results show that the battery has a discharge capacity of 200.8 mAh·g−1 initially and 170.4 mAh·g−1 after 100 cycles.

Healable, Recyclable, and Upcyclable Gel Membranes for Efficient Carbon Dioxide Separation.

Ionic liquids (ILs) are prized for their selective dissolution of carbon dioxide (CO2), leading to their widespread use in ionogel membranes for gas separation. Despite their advantages, creating sustainable ionogel membranes with high IL contents poses challenges due to limited mechanical strength, leakage risks, and poor recyclability. Herein, we leverage copolymerized and supramolecularly bound ILs to develop ionogel membranes with high mechanical strength, zero leakage, and excellent self-healing and recycling capabilities. These membranes exhibit superior ideal selectivity for gas separation compared to other reported ionogel membranes, achieving a CO2/nitrogen selectivity of 61.7 and a CO2/methane selectivity of 24.6, coupled with an acceptable CO2 permeability of 186.4 Barrer. Additionally, these gas separation ionogel membranes can be upcycled into ionic skins for sensing applications, further enhancing their utility. This research outlines a strategic approach to molecularly engineer ionogel membranes, offering a promising pathway for developing sustainable, high-performance materials for advanced gas separation technologies.

Morphology Control of Nanoporous Gold Through Selective Dissolution of Au–Ge Eutectic Microstructures

The synthesis of nanoporous gold (np‐Au) through the conventional method of dealloying a more reactive element from AuTherma alloys has been extensively studied and applied in various fields, particularly catalysis. Herein, a novel approach to creating droplet‐like np‐Au through the selective dissolution of Au–Ge eutectic microstructures is explored. This work reveals that adjusting the undercooling of the eutectic melt during solidification allows for the tuning of pore and ligament sizes. It is demonstrated that this undercooling can be modified, either directly or indirectly, by adjusting either the cooling rate or the heterogeneous nucleation site density of the eutectic melt. The findings, aligned with the model based on classical theory for eutectic solidification, elucidate the connection between the tuning of pore and ligament sizes in the eutectic microstructure and the undercooling of the eutectic melt. Importantly, it is established that this phenomenon is applicable across a variety of compositions, including hypereutectic, eutectic, and hypoeutectic. The ability to regulate pore and ligament size in single crystals of np‐Au droplets offers a novel approach to synthesizing catalytic np‐Au crystals with enhanced mechanical and thermal stability compared to conventional methods.

Atomic-Scale Behavior of Perovskite-Supported Ir-Pd-Ru Nanoparticles under Redox Atmospheres.

An advanced materials solution utilizing the concept of "smart catalysts" could be a game changer for today's automotive emission control technology, enabling the efficient use of precious metals via their two-way switching between metallic nanoparticle forms and ionic states in the host perovskite lattice as a result of the cyclical oxidizing/reducing atmospheres. However, direct evidence for such processes remains scarce; therefore, the underlying mechanism has been an unsettled debate. Here, we use advanced scanning transmission electron microscopy to reveal the atomic-scale behaviors for a LaFe0.95Pd0.05O3-supported Ir-Pd-Ru nanocatalyst under fluctuating redox conditions, thereby proving the reversible dissolution/exsolution for Ir and Ru but with a limited occurrence for Pd. Despite such selective dissolution during oxidation, all three elements remain cooperatively alloyed in the subsequent reduction, which is a key factor in preserving the catalytic activity of the ternary nanoalloy while displaying its self-regenerating functionality and control of particle agglomeration.

Phase quantification analysis in cement-blended slag system with the PONKCS method

The Partial Or No Known Crystal Structure (PONKCS) method, an XRD analysis technique, is widely employed for phase quantification in cement-blended supplementary cementitious materials (SCMs). This study emphasized unsolved factors in applying this method to SCMs blends, including obtaining accurate SCM structure information, accounting for chemical composition variation, and identifying suitable C–S–H profiles. Ground granulated blast furnace slag was chosen as the representative SCM. Results show that four fundamental parameter (FP) type peaks were sufficient to index slag pseudo-structure without Pawley fitting. Slag weight fraction quantification was minimally impacted by slag pseudo-structures from slag with SiO2 content variations up to 3.03%. The C–S–H profile, with negligible clinker residue and a Lorentzian crystallite size of approximately 6.9 nm, was found suitable for PONKCS method application. Combining selective dissolution method with PONKCS method improved its accuracy. This study enhances improving quantification precision and extending the applications of PONKCS method in variable SCMs systems.

Tuning surface Mn defects on LaMnO3 perovskite oxides by selective dissolution strategy for enhanced phosphate removal

Selective dissolution is widely used to adjust the surface state of LaMnO3 perovskite oxides. In this study, LaMnO3(LMO) with B-Site vacancies was synthesized using ascorbic acid to selectively remove Mn cations and enhance phosphate adsorption. The optimized LMO with Mn defects (LMO-AA3) presented large surface area, plenty of mesoporosity and suitable electronic structure. Particularly, the adsorption capacity (113.48 mg/g) of LMO-AA3 was about10 times that of LMO. Adsorption experiments showed adsorption occurred both chemically and physically on the heterogeneous adsorption surfaces, as the pseudo-second-order kinetic model and the Redlich-Peterson isotherm model predicted. The stimulated mechanism of LMO-AA3 achieved phosphate absorption through enhancing electrostatic attraction and ligand exchange by –OH groups. Regeneration testing showed that LMO-AA3 can be used for both high and low-concentration purification of phosphate. The selectively remove Mn cations method may offer an appropriate choice for enhancing the material characteristics of effective phosphate capture.

The effect of thermal-induced phase transformation on the corrosion behavior of Inconel 625 alloy in NaCl-KCl-MgCl2 molten salt

In this paper, the effect of thermal-induced phase transformation in Inconel 625 alloy on corrosion behavior in high-temperature molten NaCl-KCl-MgCl2 salt was investigated. The results showed that the corrosion behavior was effectively influenced by the redistribution of Cr induced by the thermal-induced phase transformation. The Cr-rich chain carbides at the grain boundary and the Cr-rich regions between the needle-like δ phases formed the continuous Cr-rich channels from the grain boundary to the grain interior, which aggravated the inhomogeneous distribution of Cr and promoted the corrosion process. On this basis, the corrosion process occurred with the selective dissolution of the Cr element and invasion of Mg and O, which led to surface corrosion products composed of MgO/MgCr2O4 and subsurface corrosion holes. The research results of this paper are useful for understanding the role of phase transformation in superalloys during high-temperature molten salt corrosion.

Exploring the electronic influence on coordination complexes formed from appended pyrrolidine azothioformamide ligands and copper(I) salts

Redox-active arylazothioformamide (ATF) ligands have seen attention through their unique coordination complexes formed with salts of late transition metals and their known ability to oxidatively dissolve zerovalent metals. When mixed with Cu(I) salts, ATF ligands form both 2:1 and 2:2 coordination complexes remaining neutral without undergoing any redox event. Herein, a series of para-substituted pyrrolidine-ATFs were synthesized, incorporating both electron-donating groups (i.e., -OMe and -Me) as well as electron-withdrawing groups (i.e., -CF3, and -CN). These ligands were then mixed with Cu(I) salts, including CuBr, CuI, and [(CH3CN)4Cu](BF4) to form coordination complexes. The resulting complexes underwent thorough characterization, with several producing X-ray quality crystals for detailed structural analysis. Both strong and weak intermolecular interactions were found through Hirshfeld surface analysis and the redox activity of the complexes was probed using cyclic voltammetry in the voltage range of -1.8 to 1.8 V. Through a UV–Vis titration study, the binding interactions between the ligand host and Cu(I) metal salt guest molecules were determined and ranged from 4,000 – 100,000 M-1. Computational modeling was employed to calculate the change in Gibbs free energy (ΔG) for the formation of the complexes, revealing the optimal orientations between the ligand and the metal. These studies have confirmed that para-substituted pyrrolidine-ATFs containing electron-donating groups exhibit a higher binding affinity towards Cu(I) metal salts compared to those with electron-withdrawing groups. With a thorough understanding of ATF-metal coordination, further ligand design can lead to exciting new catalysts and/or selective metal dissolution agents.

The spontaneous passivation of (CoFeNi)(1-x)/3Crx alloys in sulfuric acid

The influence of at% Cr on the spontaneous passivation of (CoFeNi)(1-x)/3Crx alloys in 0.1 M H2SO4 was investigated. During spontaneous passivation, Cr enrichment occurs due to the selective dissolution of the matrix elements. The quantity of Cr enrichment is relatively constant with at% Cr while the total quantity of alloy dissolved decreases with increasing at% Cr. Element resolved polarization curves predict spontaneous passivation by comparing the critical dissolution rate with the cathodic kinetics near the corrosion potential. The stoichiometric relationships between the spontaneous dissolution rate, Cr enrichment, and the open circuit potential were determined and discussed.

Corrosion kinetics and mechanisms of 15–15Ti steel in flowing liquid lead-bismuth eutectic at 500°C

The application of Liquid Lead-Bismuth Eutectic (LBE) as a coolant in Lead-cooled Fast Reactors (LFRs) presents significant challenges due to its corrosive nature, especially at elevated temperatures. This study investigates the corrosion kinetics and mechanisms of 15–15Ti stainless steel in flowing LBE at 500 °C with oxygen concentrations ranging from 1 to 3 × 10−6 wt% and a flow rate of 1 m s-1. The research highlights the formation and growth of the Fe-Cr spinel oxide layer, which follows a parabolic rate law indicative of a diffusion-controlled process, crucial for long-term material stability predictions. Despite the initial effectiveness of the Fe-Cr spinel layer in mitigating corrosion, its integrity is compromised over time due to spallation and dissolution, allowing penetration of LBE elements and selective dissolution of Fe, Ni, and Cr. The study reveals a complex interplay between direct dissolution of steel components and spallation of the oxide layer, providing critical insights into material loss mechanisms and the degradation of structural materials in LBE-cooled reactors.

Development of Thin-Film Nanoporous Ruthenium Electrocatalysts Using Atom Probe Tomography

Dealloying corrosion has been used to create high surface area nanoporous metals with promising catalytic properties towards alkaline water electrolysis [1], [2]. The selective dissolution of the less-noble metal from a solid-solution alloy results in a 3D open-pore, nanostructured substrate which is chemically rich in the more noble metal. Ruthenium, the cheapest Pt-group metal [3], has desirable catalytic properties for the hydrogen evolution reaction, however making nanoporous ruthenium (NPR) substrates by dealloying has been challenging due to its limited miscibility with Ag and Cu, compared to the more widely studied Au. Hence, the potential improvement of Ru catalytic properties through dealloying Ru-based systems remains unexploredIn this study, we use magnetron sputtering to make metastable, single-phase, Ag-Ru thin films, with the aim of electrochemically dealloying them to create uniformly NPR substrates. The impact of thin-film structures and chemistry on subsequent dealloying behaviors were investigated by integrating electrochemical measurements with high-resolution characterization techniques including atom probe tomography (APT), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM). Furthermore, we correlate the thin-film properties studied with the structure and chemistry of NPR formed during dealloying. Amongst the valuable insights attained, we reveal atomic-scale compositional fluctuations in as-deposited non-equilibrium Ag-Ru, that impact the nanoligament compositions in dealloyed nanoporous ruthenium. Finally, the electrocatalytic performance of different NPR substrates are reported for hydrogen evolution reaction. Thereby, advancing the development of novel Ru-based nanoporous electrocatalysts and outlining pathways for future guided optimization.[1] Erlebacher, J., Newman, C. & Sieradzki, K. Fundamental physics and chemistry of nanoporosity evolution during dealloying. RSC Nanosci. Nanotechnol. 11–29 (2012). doi:10.1039/9781849735285-00011[2] J. Tian et al., “Dealloying of an amorphous TiCuRu alloy results in a nanostructured electrocatalyst for hydrogen evolution reaction,” Carbon Energy, vol. 5, no. 8, Aug. 2023, doi: 10.1002/cey2.322.[3] Johnson Matthey Inspiring science, enhancing life. Available at: https://matthey.com/products-and-markets/pgms-and-circularity/pgm-management (Accessed: 18 December 2023).

Unprecedented Mutual Separation of Nd–Pr by Selective Dissolution of Nd2O3 Directly from a Nd2O3–Pr6O11 Mixture into an Ionic Liquid Containing a Highly Fluorinated β-Diketone

Unprecedented Mutual Separation of Nd–Pr by Selective Dissolution of Nd₂O₃ Directly from a Nd₂O₃–Pr₆O₁₁ Mixture into an Ionic Liquid Containing a Highly Fluorinated β-Diketone

Mid to Late-Holocene environmental dynamics recorded in Lake Pup Lagoon, East Antarctica: Insights from environmental magnetism and biogeochemical proxies

Paleoenvironmental archives in East Antarctica have revealed significant changes during the Holocene, marked by ice sheet retreat leading to the isolation of submarine basins. These basins offer valuable insights into past climate, glaciology, and oceanography shifts that impact sedimentary processes. In this study, environmental magnetism and biogeochemical proxies to investigate the Mid-to-Late-Holocene transitions in Pup Lagoon, a coastal isolation basin is presented. Our findings reveal distinct stratigraphic zones reflecting shifts from marine to lacustrine environments. The results reveal predominant mechanical weathering in the Stornes region, producing coarse-grained “soft” ferrimagnetic minerals. Notably, a period of warm oceanographic conditions between 6000 and 4722 cal. yr BP was characterized by mixed magnetic grain sizes and ultrafine superparamagnetic grains, indicating relatively oxic open waters in the basin. Subsequent shifts to reducing conditions coincide with persistent marine sea ice cover from 4722 to 2634 cal. yr BP, favoring the retention of coarse-grained ferrimagnets. Finer magnetic grain sizes between 2634 and 2185 cal. yr BP was attributed to the increased freshwater inputs associated with the Mid-Holocene Hypsithermal. Further, diagenetic changes under persistent sea ice cover between 2185 and 1970 cal. yr BP led to the selective dissolution of fine-grained ferrimagnets. Transitioning to freshwater isolated basin conditions between 1970 and 588 cal. yr BP, fine ferrimagnet precipitation indicate oxic to suboxic conditions alongside drier conditions. Biogenic productivity increased post-isolation, which was reflected in increased (Total Organic Carbon) TOC and (Total Nitrogen) TN percentages. Additionally, the presence of greigite in the isolated phase sediment indicates reducing conditions owing to organic matter decomposition. Notably, χfd% exhibits an inverse trend to sea ice concentration, potentially indicating anoxic-dysoxic conditions due to the presence of sea ice. These observations align with broader regional sea ice concentration changes, emphasizing the interconnected behavior of local and regional factors shaping Antarctic coastal environments.