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Difficult-to-cut titanium matrix composites (TiB+TiC)/Ti6Al4V have extensive application prospects in the fields of biomedical and aerospace metal microcomponents due to their excellent mechanical properties. Jet electrochemical micromilling (JEMM) technology is an ideal method for machining microstructures that leverages the principle of electrochemical anodic dissolution. However, the matrix Ti6Al4V is susceptible to passivation during electrochemical milling, and the inclusion of high-strength TiB whiskers and TiC particles as reinforcing phases further increases the machining difficulty of (TiB+TiC)/Ti6Al4V. In this study, a novel approach using NaCl+NaNO3 mixed electrolyte for the JEMM of (TiB+TiC)/Ti6Al4V was adopted. Electrochemical behaviors were measured in NaCl and NaCl+NaNO3 electrolytes. In the mixed electrolyte, a higher transpassive potential was required to break down the passive film, which led to better corrosion resistance of (TiB+TiC)/Ti6Al4V, and the exposed reinforcing phases on the dissolved surface were significantly reduced. The results of the JEMM machining indicate that, compared to NaCl electrolyte, using mixed electrolyte effectively mitigates stray corrosion at the edges of micro-grooves and markedly improves the uniformity of both groove depth and width dimensions. Additionally, the surface quality was noticeably improved, with a reduction in Ra from 2.84 μm to 1.03 μm and in Rq from 3.41 μm to 1.40 μm.

This study determined the critical parameters for the morphological development of the electrode surface (the critical potential and the critical charge) during anodic selective dissolution of a Cu–Pd alloy with a volume concentration of 15 at.% palladium. When the critical values were exceeded, a phase transition occurred with the formation of palladium’s own phase. Chronoamperometry aided in the determination of the partial rates of copper ionization and phase transformation of palladium under overcritical selective dissolution conditions. The study determined that the formation of a new palladium phase is controlled by a surface diffusion of the ad-atom to the growing three-dimensional nucleus under instantaneous activation of the nucleation centres. We also identified the role of this process in the formation of the electrocatalytic activity of the anodically modified alloy during electro-oxidation of formic acid. This study demonstrated that HCOOH is only oxidated at a relatively high rate on the surface of the Cu85Pd15 alloy, which is subjected to selective dissolution under overcritical conditions. This can be explained by the fact that during selective dissolution of the alloy, a pure palladium phase is formed on its highly developed surface which has prominent catalytic activity towards the electro-oxidation of formic acid. The rate of electro-oxidation of HCOOH on the surface of the anodically modified alloy increased with the growth of the potential and the charge of selective dissolution, which can be used to obtain an electrode palladium electrocatalyst with a set level of electrocatalytic activity towards the anodic oxidation of formic acid.

The frontiers of material corrosion research are transitioning from macroscopic corrosion to the micro or even nanoscale. The presence of a substantial number of simulated atoms in metal nanomaterials introduces considerable complexity when studying corrosion mechanisms. Therefore, under the framework of lattice dynamics, combined with nano-thermodynamic theory, the electrochemical Butler-Volmer (BV) equation is developed to simplify the investigation of the anodic dissolution behavior of nanomaterials. The results show that the difference between the lattice parameters optimized using the General Utility Lattice Program (GULP) and the Cambridge Sequential Total Energy Package (CASTEP) results is 0.01 Å, and the variation in cohesion and surface energies is only 0.001 eV and 0.005 eV/Å 2 . Meanwhile, the anodic dissolution rates of Magnesium (Mg) at the (0001), (10一0), and (111一0)2 crystal planes calculated from the BV model based on lattice dynamics are in agreement with the results derived from first principles. During the active dissolution zone, the corrosion potential increases from -6.91 V vs. SHE to -5.02 V vs. SHE, and the corrosion current density (Log i ) decreases from 42.27 A/cm 2 to 26.47 A/cm 2 as the Mg nanoparticles size increases from 1 nm to 7.5 nm. The improved model quantifies the relationship between surface properties and corrosion behavior through the size effect of nanoparticles, which enriches the way of studying electrochemical properties at the nanoscale.

— Experimental study of the anodic dissolution of titanium and its alloys over a wide range of current densities, including pulsed currents (up to 100 A/cm 2 ), under controlled hydrodynamic conditions and surface temperature in nitrate and chloride solutions, showed that the process is mediated by electrochemical formation of an anodic oxide film (AOF), which undergoes chemical dissolution. The AOF has a bilayer structure (two barrier films: at the interface with the metal and solution). It is described by PDM-III (Point Defect Model). Under certain conditions, it is possible to achieve a steady state in which the film growth rate is compensated by the rate of its chemical dissolution (during a pulsed treatment). In this case, there is a 100% current efficiency in terms of titanium ionization in the oxidation state of four. Under the conditions of the described experiments, i.e., when using direct current, the rate of the AOF electrochemical formation exceeds that of its chemical dissolution, which leads to a decrease in the current efficiency, which does not exceed 75%. Due to the temperature dependence of the electrical resistance of the barrier film at the interface with the solution, which determines its thickness, the current efficiency increases with an increase in the flow rate of the electrolyte. When the thermokinetic instability (TKI) of the AOF is reached (thermal explosion caused by positive feedback: the rate of electrochemical reaction–surface temperature–the rate of electrochemical reaction), the interaction of electrolyte components with the surface free from the film leads to “anomalous” anodic dissolution of the AOF with a current efficiency exceeding 100%. Regardless of the nature of the electrolyte, the TKI conditions are reached at ~1 A/cm 2 . It has been shown that the dissolution rate in nitrate solutions for certain pulsed treatment parameters (relative pulse duration of 2, dc = 50%) (and the displacement of cathode tool in electrochemical machining) may exceed the machining rate with direct current of the same density by more than a factor of two.

Stress Corrosion Cracking (SCC) process through which cracks occur in a variety of susceptible materials is a result of a combination of residual or applied stresses and corrosion. In oil and gas field, buried pipeline steels are made of low-alloy steels with a ferritic-pearlitic structure, such as X70. In dilute solutions, these materials are prone to SCC failure. The Near-neutral simulated soil solution (NS4) solution is established to imitate SCC conditions and subsequently became the industry requirement for crack growth experiments in the majority of laboratories. The strain-assisted active crack pathways are considered while modelling SCC growth as an oxide film rupture and anodic dissolution process. It’s been hypothesized that increasing the strain concentration can help with dissolution at the film-free crack tip. This research focuses on estimating the SCC crack growth rate under various environmental conditions in oil and gas pipelines using finite element modelling. The simulation is carried out using the J-integral theory in the COMSOL Multiphysics program. Simulations are performed to model the crack growth rate (CGR) using slip anodic dissolution (film rupture) mechanism. The plastic strain gradient is required to compute the SCC CGR (da/dt). Because the plastic strain located at crack tip increases proportionally to the crack length as it propagates, the CGR increases as the stress intensity factor (SIF) increases. The crack growth rates increase when constant loads are applied and as the temperature rises, and elevating the cathodic potential has a minimal influence on the propagation rate of cracks but raises the material yield strength and imparts brittle behavior to it.

—Two Tafel regions with slopes of 0.06 and 0.09 V were observed on the dependences of the anodic dissolution of Fe in NaCl solutions with additions of NH 4 OH and H 2 O 2 at low current densities. It was shown that the sign of the surface charge changed at the potential of the transition from one Tafel region to another. In the first and second sections, the dissolution of iron occurred according to the Heusler scheme with the participation of Fe(OH) ads . The deceleration in the second section was associated with the adsorption of oxygen and the redistribution of the potential jump between the jump localized in the dipole oxygen layer and the jump in the ionic cover of the EDL. The contribution of the dipole layer to the potential jump at the electrode/solution interface was determined.

The long-standing issue of lithium dendrite growth during repeated deposition or dissolution processes hinders the practical use of lithium-metal anodes for high-energy density batteries. Here, we demonstrate a promising lithiophilic–lithiophobic gradient interfacial layer strategy in which the bottom lithiophilic zinc oxide/carbon nanotube sublayer tightly anchors the whole layer onto the lithium foil, facilitating the formation of a stable solid electrolyte interphase, and prevents the formation of an intermediate mossy lithium corrosion layer. Together with the top lithiophobic carbon nanotube sublayer, this gradient interfacial layer can effectively suppress dendrite growth and ensure ultralong-term stable lithium stripping/plating. This strategy is further demonstrated to provide substantially improved cycle performance in copper current collector, 10 cm 2 pouch cell and lithium–sulfur batteries, which, coupled with a simple fabrication process and wide applicability in various materials for lithium-metal protection, makes the lithiophilic–lithiophobic gradient interfacial layer a favored strategy for next-generation lithium-metal batteries. Lithium metal batteries suffer from the dendrite growth upon electrochemical cycling. Here the authors introduce a lithiophilic-lithiophobic gradient interfacial ZnO/CNT layer, which facilitates the formation of a stable solid electrolyte interphase, and suppresses the growth of lithium dendrite.

Historically long accepted to be the singular root cause of capacity fading, transition metal dissolution has been reported to severely degrade the anode. However, its impact on the cathode behavior remains poorly understood. Here we show the correlation between capacity fading and phase/surface stability of an LiMn 2 O 4 cathode. It is revealed that a combination of structural transformation and transition metal dissolution dominates the cathode capacity fading. LiMn 2 O 4 exhibits irreversible phase transitions driven by manganese(III) disproportionation and Jahn-Teller distortion, which in conjunction with particle cracks results in serious manganese dissolution. Meanwhile, fast manganese dissolution in turn triggers irreversible structural evolution, and as such, forms a detrimental cycle constantly consuming active cathode components. Furthermore, lithium-rich LiMn 2 O 4 with lithium/manganese disorder and surface reconstruction could effectively suppress the irreversible phase transition and manganese dissolution. These findings close the loop of understanding capacity fading mechanisms and allow for development of longer life batteries. To unlock the potential of Mn-based cathode materials, the fast capacity fading process has to be first understood. Here the authors utilize advanced characterization techniques to look at a spinel LiMn 2 O 4 system, revealing that a combination of irreversible structural transformations and Mn dissolution takes responsibility.

Rechargeable lithium metal (Li 0 ) batteries (RLMBs) are considered attractive for improving Li-ion batteries. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) has been extensively used as a conducting salt for RLMBs due to its advantageous stability and innocuity. However, LiTFSI-based electrolytes are corrosive towards aluminium (Al 0 ) current collectors at low potentials (>3.8 V versus Li/Li + ), thereby excluding their application in 4-V-class RLMBs. Herein, we report on a non-corrosive sulfonimide salt, lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (LiDFTFSI), that remarkably suppresses the anodic dissolution of the Al 0 current collector at high potentials (>4.2 V versus Li/Li + ) and significantly improves the cycling performance of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC111) cells. In addition, this sulfonimide salt results in the growth of an advantageous solid electrolyte interphase on the Li 0 electrode. The replacement of either LiTFSI or LiPF 6 with LiDFTFSI endows a Li 0 ||NMC111 cell with superior cycling stability and capacity retention (87% at cycle 200), demonstrating the decisive role of the salt anion in dictating the electrochemical performance of RLMBs. Lithium bis(trifluoromethanesulfonyl)imide is used as a conducting salt for rechargeable lithium metal batteries because of its stability, but corrosion with aluminium current collectors is an issue. A non-corrosive sulfonimide salt is shown to suppress anodic dissolution of an Al current collector at high potentials while improving cycling.

HighlightsThe Zn/MnO2 cell with inorganic colloidal electrolyte demonstrates unprecedented durability over 1000 cycles.For the cathode, the presence of the protective film can inhibit the dissolution of manganese element and the formation of irreversible by-products.For the anode, it can reduce the corrosion and de-solvation energy, inhibit the growth of dendrite and irreversible by-products.Zinc-ion batteries (ZIBs) is a promising electrical energy storage candidate due to its eco-friendliness, low cost, and intrinsic safety, but on the cathode the element dissolution and the formation of irreversible products, and on the anode the growth of dendrite as well as irreversible products hinder its practical application. Herein, we propose a new type of the inorganic highly concentrated colloidal electrolytes (HCCE) for ZIBs promoting simultaneous robust protection of both cathode/anode leading to an effective suppression of element dissolution, dendrite, and irreversible products growth. The new HCCE has high Zn2+ ion transference number (0.64) endowed by the limitation of SO42−, the competitive ion conductivity (1.1 × 10–2 S cm−1) and Zn2+ ion diffusion enabled by the uniform pore distribution (3.6 nm) and the limited free water. The Zn/HCCE/α-MnO2 cells exhibit high durability under both high and low current densities, which is almost 100% capacity retention at 200 mA g−1 after 400 cycles (290 mAh g−1) and 89% capacity retention under 500 mA g−1 after 1000 cycles (212 mAh g−1). Considering material sustainability and batteries’ high performances, the colloidal electrolyte may provide a feasible substitute beyond the liquid and all-solid-state electrolyte of ZIBs.