Search Results (201)

The high-voltage spinel ${\mathrm{LiNi}}_{0.5}{\mathrm{Mn}}_{1.5}{\mathrm{O}}_4$ (LNMO) is a promising cobalt-free cathode material for lithium-ion batteries, yet its integration as a binder-free thin film on metallic current collectors via simple solution routes remains underexplored. Here, LNMO films were synthesized on 304 stainless steel (SS304) by metal–organic decomposition (MOD) from metal–acetate precursors in ethanol, followed by spin-coating and annealing at 500, 600, and 700 °C under flowing ${\mathrm{O}}_2$. The films were characterized by XRD, FESEM–FIB cross-sectioning, EDS, and XPS, and tested as binder-free cathodes by cyclic voltammetry and galvanostatic charge/discharge. All samples are dense, approximately 1.9 μm thick, and crystallize in the disordered spinel phase. The LNMO crystallite size increases from 21.9 to 43.8 nm between 500 and 700 °C, while the grain size also shows a temperature dependence, increasing the average size from 25 up to 56 nm in diameter. XPS confirms ${\mathrm{Mn}}^{4+}$ as the dominant manganese surface species (45–49%) across all samples. The films deliver reversible discharge capacities of 92, 92, and 70 mAh ${\mathrm{g}}^{-1}$ at 0.1 C for LNMO500, LNMO600, and LNMO700, respectively, with well-defined ${\mathrm{Ni}}^{2+}{\mathrm{/Ni}}^{3+}$ and ${\mathrm{Ni}}^{3+}{\mathrm{/Ni}}^{4+}$ redox peaks at 4.7 and 4.8 V. DFT calculations independently predict a voltage plateau at ∼4.7 V for $0.2\le x\le 1$, in agreement with the experimental profiles. These findings establish MOD as a viable, vacuum-free route to the synthesis of nanostructured LNMO cathodes. Full article

This paper aims to analyse the microstructure and properties of the titanium- and boron-alloyed high-carbon medium-manganese 140Mn6Cr3TiB steel deposit before and after high-frequency mechanical impact (HFMI) treatment. XRD, SED, and EDS analyses were applied to evaluate the microstructural peculiarities of the studied deposit. Nanoindentation and scratch/sliding tests respectively revealed distinct correlations between the phase composition and the deformation/wear behaviour. HFMI results in the formation of the strain-induced ε- and α’-martensites (~66% and 3–6%, respectively), a significant grains/crystallites refinement (down to 31–54 nm), and dislocation density, which support essential hardening (by ~50%). The HFMI regime (load = 100 N, amplitude = 10 µm, and time = 60 s) was found to be the best, which led to the enhanced wear resistance (decreased wear volume) by ~4 times. The heterogeneous nature of the steel deposit creates a “shield-and-buffer” effect, where the hard eutectic framework resists penetration and tough matrix prevents brittle failure, maintaining a high tolerance to abrasion damage. The HFMI-hardening changed the wear mechanism from the ‘wedge/pile-up’ formation to ploughing. Thus, the HFMI shows a good efficiency in finishing the protective medium-manganese steel deposits of enhanced wear resistance to prolong the operation life of responsible parts. Full article

Despite its excellent impact toughness and work-hardening capacity, high-manganese steel (HMS) suffers from low initial hardness, limiting its wear resistance under low-stress conditions. Conventional surface hardening methods for HMS involve high cost and intensive energy consumption and produce only shallow hardened layers; moreover, the understanding of laser transformation hardening in HMS remains insufficient. To address these gaps, this study employs a high-energy-density laser for rapid and precise surface modification of Mn13 HMS. The studied Mn13 steel contains 1.98 wt.% Cr, which contributes to solid-solution strengthening and influences the phase transformation behavior during laser transformation hardening. By optimizing the laser power, a well-defined laser-quenched layer with a gradient microstructure along the thickness direction is obtained. Microhardness at the surface treated by laser transformation hardening at 1.5 kW improved significantly, primarily due to grain refinement and a dense dislocation network. The small fraction of martensite contributes indirectly by generating geometrically necessary dislocations and acting as local barriers to dislocation glide. Along the depth direction, the microhardness varies with the gradient microstructure: coarse columnar grains at intermediate depths cause a slight decrease in microhardness, while the substrate restores it. Correspondingly, the laser-quenched surface exhibits improved wear resistance, as indicated by reduced friction coefficient, wear depth, and wear volume, and the dominant wear mechanism shifts from adhesive to abrasive wear. Importantly, this gradient configuration maintains a mechanically compatible transition between the quenched layer and the substrate, preserving impact toughness comparable to that of the untreated material. Full article

This study evaluates fatigue crack growth in marine high-manganese steel LNG (Liquefied Natural Gas) storage tanks under cryogenic conditions. A 3D simulation framework using the M-integral for stress intensity extraction and the VCTD (Vertical Crack Tip Displacement) criterion for path prediction was developed. Parametric simulations showed that crack propagation is strongly directional, with the surface growth rate exceeding the depthwise rate. Fatigue life decreased with increasing initial crack surface length and maximum load but increased with crack inclination angle. In addition, the Mode I stress intensity factor along the depthwise path converged during propagation and rose sharply when the crack depth approached 90% of the wall thickness. An XGBoost-based dual-target model further achieved accurate prediction of crack depth and residual life. Full article

Accurate prediction of the stacking fault energy (SFE) is critical for controlling deformation mechanisms, specifically transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), in high-manganese (high-Mn) austenitic steels, which are of growing importance in automotive and structural applications that demand exceptional strength–ductility combinations. This study presents a systematic comparative evaluation of six supervised machine learning (ML) models—Multiple Linear Regression (MLR), Random Forest (RF), Extra Trees (ETs), Gradient Boosting (GB), Support Vector Regression (SVR), and a stacking ensemble—trained on a curated, outlier-cleaned experimental database of Fe-Mn-C-Si-Al-Cr-Ni-N spanning SFE values from 5.0 to 63.0 mJ/m² (mean 23.7 ± 11.2 mJ/m²). After Z-score outlier removal (|Z| > 3) and 80/20 train–test splitting with nested 5-fold cross-validation hyperparameter optimization using GridSearchCV, ET and GB achieved training R² values of 0.988 and 0.990, respectively, confirming that SFE is highly predictable from alloy composition alone. The stacking ensemble delivered the best generalization on the independent held-out test set (test R² = 0.603, RMSE = 5.60 mJ/m², MAE = 4.86 mJ/m²), outperforming all the individual learners. Random Forest feature importance analysis identified Al (22.3%), Fe (20.5%), and Mn (17.7%) as the three most influential compositional variables, collectively explaining 60.6% of the predicted variance. Pearson correlation analysis confirmed that Al was the strongest individual linear predictor (r = +0.421, p < 0.001), whereas Fe showed a significant negative correlation (r = −0.327, p < 0.001). Mn, C, and the remaining elements showed no statistically significant linear correlations with SFE, underscoring the dominance of nonlinear compositional interactions. Composition–SFE design maps derived from the GB model delineate the TRIP/TWIP regime boundaries in the Mn–C and Mn–Al composition spaces, providing a validated computational tool for targeted high-Mn steel alloy design. Full article

High-manganese steel has emerged as a potential alternative material to austenitic stainless steel for liquid hydrogen storage and transportation environments, owing to its superior mechanical characteristics and limited hydrogen diffusivity. However, its hydrogen embrittlement (HE) susceptibility limits its engineering applications. This study investigates the effect of microstructural regulation through trace titanium (Ti, 0.021 wt%) addition on HE resistance in high-manganese steel. By means of Electron Backscatter Diffraction (EBSD), TEM, SEM, and Slow Strain Rate Tensile (SSRT) tests, the effects of Ti on the microstructure, mechanical properties, and HE susceptibility of high-manganese steel are systematically investigated. The results show that the addition of Ti did not significantly alter the average austenite grain size or phase composition, but it generated a large number of Ti(C,N) nanoscale precipitates with sizes ranging from 20 to 70 nm within the matrix. The elongation loss of the 25Mn-Ti specimen was significantly lower than that of the 25Mn specimen when hydrogen-charged for 72 h, decreasing from 18.4% to 9.3%. The fracture surfaces consistently exhibited ductile dimple morphology, whereas 25Mn steel demonstrated significant cleavage-induced brittle fracture. EBSD analysis revealed that hydrogen-charged 25Mn-Ti steel exhibited higher Kernel Average Misorientation (KAM) value retention rate and more uniform grain strain distribution, indicating enhanced microstructural deformation compatibility. The main mechanism was that Ti pre-formed nanoscale Ti(C,N) precipitates during the preparation of 25Mn high-manganese steel, which played a key role in inhibiting HE. These precipitates altered hydrogen diffusion behavior and distribution patterns, reduced stress concentration levels, and inhibited hydrogen-induced crack initiation. This work is of great significance for improving the HE resistance of high-manganese steels. Full article

The friction-induced stick-slip vibration (FISSV) generated by intense friction between the brake disc and brake pads of high-speed trains is a critical issue affecting braking stability, the service life of foundational braking components, and ride comfort. The floating friction block structure, which effectively regulates interfacial contact characteristics through the elastic deformation of disc springs, thereby improving tribological behavior, represents an effective approach for mitigating FISSV. However, the topic of how to design the floating structure of the friction block to produce the best suppression impact on FISSV emerges, using the choice of disc spring material as an example. Thus, the purpose of this study is to look at how disc spring material affects stick-slip vibration (SSV) at the high-speed train floating brake interface. Four typical disc spring materials—304 stainless steel, Mubea-specific spring steel, 50CrVA high-alloy spring steel, and 60Si₂MnA silicon-manganese spring steel—were selected. Through braking tribological tests and explicit dynamics-wear coupling simulations, the effects of material differences on interfacial friction-wear characteristics and SSV behavior were systematically studied. The findings show that the stiffness of the disc spring material greatly influences the dynamic responsiveness of the system and the contact pressure distribution at the braking interface, elasticity, and damping characteristics. 60Si₂MnA spring steel, owing to its excellent elastic recovery and load equalization capability, promoted the formation of uniformly dispersed medium-to-small contact platforms on the interface, resulting in the mildest wear. Concurrently, its system vibration energy exhibited a more dispersed distribution in the frequency domain, with low SSV intensity and weak nonlinear behavior, demonstrating the best comprehensive performance. Materials with poorer compatibility, such as 304 stainless steel, tended to cause localized stress concentration, exacerbating wear and intensifying severe high-frequency SSV. The influence mechanism of disc spring material at the interface is shown by this work, providing an important basis for material optimization and vibration suppression design in floating brake pad structures. Full article

Thermal accumulation is a critical constraint in robotic grinding of ZGMn13 high-manganese steel, whereas the variables that can be prescribed or monitored reliably online are often limited to the normal load $F_z$, spindle speed $n$, and feed speed ${\nu }_w$. Most existing studies focus on single-pass conditions or scalar thermal indicators, while full-process near-surface transient temperature histories in multi-layer robotic grinding remains insufficiently addressed. This study presents a full-process near-surface transient temperature histories framework for multi-layer robotic grinding under fixed wheel–workpiece conditions and limited online sensing. Multi-channel near-surface thermal measurements were first reorganized into layer-resolved time-series data. A process-driven thermal surrogate was then constructed from the deployable inputs $\left(F_z,n,{\nu }_w\right)$, and a recursive temperature-evolution model was developed by incorporating intra-layer thermal retention and interlayer residual-heat inheritance. The proposed formulation predicts the near-surface transient temperature history over successive grinding layers. Experimental results showed clear layer-wise transience and progressive thermal accumulation during multi-layer grinding. Under representative conditions, the proposed framework reproduced the dominant transient structure of the measured full-process near-surface temperature histories, and grouped validation further showed that the recursive formulation preserved more useful history-level information than the reduced baselines within the tested domain. Within the tested operating domain, the predicted histories were further reduced to derived thermal indicators and planning-oriented peak-temperature maps. Full article

Rivers contaminated with metals and petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), are still a problem that threatens aquatic ecosystem function. This study describes iron- and sulfate-reducing bacteria, principal drivers of anaerobic organic matter decomposition in aquatic sediments. A polyphasic approach, including culture-dependent, i.e., enumeration by Most Probable Number (MPN), and independent, Sanger and Next Generation Sequencing (NGS) techniques, as well as analytical geochemical analyses, was employed. This study found exceptionally high levels of metals (Al, Mn, Zn, and Pb), PAHs, and sulfates compared to typical freshwater environments, likely due to co-contamination from past petroleum and steel production waste. Microbial communities were dominated by the Thermoproteobacteria. Analysis of the iron-reducing community determined that Geobacter, critical for degrading organic matter using iron, manganese, or arsenic, was the most prevalent genus. Additionally, the presence of diverse groups involved in sulfur cycling, represented by dsrAB genes, high numbers of viable sulfate reducers, a higher abundance of Geobacter, and high levels of sulfate and iron suggests that the cryptic sulfur cycle (CSC) may be operational in this system. In addition, sulfate and iron reducers are known to enhance biodegradation of organic pollutants in the presence of metal oxides and sulfate, and thus warrant further investigation in this co-contaminated system. Full article

The microstructure of a high-manganese low-activation austenitic steel after aging for 500 and 1000 h at 700 °C was investigated using transmission and scanning electron microscopy. Two structural states were examined: cold rolling (CR) and high-temperature thermomechanical treatment (HTMT). After CR, aging leads to the precipitation of dispersed M₂₃C₆ carbides (M = Cr, W), primarily along grain and deformation twin boundaries. After HTMT, these particles are mainly localized at grain and low-angle boundaries. With increasing aging time, both the size and volume fraction of the particles increase. In both states, the microtwin and substructure are partially retained after aging. Local regions corresponding to the early stages of recrystallization were identified after both treatments. These regions were associated with intense decomposition of the supersaturated solid solution and the coarsening of carbide particles. The mechanical properties were evaluated by tensile testing at 20, 650, and 700 °C. Aging reduced average ductility after both treatments and at all test temperatures, with this trend persisting with increasing aging time. After CR and aging, a significant scatter in elongation to failure was observed, with minimum values of ≈2–3%. This behavior is attributed to the high density of plate-like M₂₃C₆ carbides at grain and microtwin boundaries. Microcrack formation and intercrystalline fracture features were observed, directly linked to the high density of boundary carbides. These effects were less pronounced in the HTMT condition after aging. In this paper, strategies for suppressing carbide precipitation in high-manganese low-activation austenitic steels via chemical composition and thermomechanical processing optimization are discussed. Full article

Steel slags are major by-products of steelmaking, and their variable composition complicates recycling and valorization strategies. This study investigates four representative slag samples obtained from different production pathways at an industrial steel plant in Uzbekistan, using a combined multi-scale characterization approach. Bulk elemental composition was determined using X-ray fluorescence (XRF), while microstructural and phase-level analysis was carried out using scanning electron microscopy with energy-dispersive spectroscopy (SEM–EDS), including both point analysis and automated phase mapping. The XRF results revealed two distinct compositional groups, with one slag dominated by Mn–Si–O chemistry and three slags characterized by high Ca content. SEM–EDS phase mapping further resolved these differences at the microscale, identifying manganese silicate and oxide phases in the Mn-rich slag, Ca–F–O dominant phases in two slags associated with fluorite flux addition, and a more heterogeneous Ca-based system with localized enrichments of Mn, Zn, and Cu in the fourth sample. The combined results demonstrate that slag composition strongly reflects steel grade and fluxing practice. The integration of XRF and SEM–EDS provides a robust framework for linking bulk chemistry with phase distribution, improving slag classification and supporting informed decisions for reuse and environmental management. Full article

This study evaluates the tribological properties of lean medium manganese advanced high-strength steel (AHSS) subjected to five different heat treatment processes. The tests were conducted under dry reciprocating conditions using the ball-on-flat method, with a G40 steel ball, a 10 N load, and 1000 cycles at room temperature. Friction behavior, wear resistance, nanoindentation hardness, surface roughness, and microstructural changes were examined. The results showed that heat treatment significantly influenced the microstructure and hardness of the samples. The Mn-Q sample, with fresh martensite, achieved the highest hardness (483 HV5), while the Mn-Q&P 500 °C sample had the lowest (336 HV5), with a 30% reduction due to tempering. The Mn-HR 500 °C sample showed the highest surface roughness (Sa = 1.876 μm) due to microstructural heterogeneity. Despite similar coefficients of friction across all samples (0.55–0.57), the Mn-Q&P 500 °C sample exhibited the best wear resistance, 18% higher than the Mn-HR 500 °C variant. Wear mechanisms were identified as a combination of abrasion and oxidation, where the latter slightly reduced the coefficient of friction (COF) but increased surface degradation. These findings highlight the potential of lean medium Mn AHSS for tribological applications, offering a favorable balance of wear resistance and frictional stability. Full article

In this study, hardfacing and a flux-cored/self-shielded powder wire of the FCAW-S-90G13N4 type was employed to produce and investigate the deposits of high-manganese steel. The effects of high-frequency mechanical impact (HFMI) treatment on the microstructure, hardening, and scratch resistance of the deposits were studied to evaluate and predict the impact wear resistance of the hardfacing deposits under controlled impact load conditions. As observed by XRD, SEM, and nanoindentation, the microstructure of deposited metal comprised a soft austenite matrix, dispersed hard carbides, and an ε phase (~26 vol.%). The wear resistance is thus not controlled by carbides alone but arises from the synergistic action of a hard carbide network within a ductile matrix. HFMI resulted in twinning, an increase in dislocation density, a grown volume fraction of ε (>60%) and α′-martensite. The interaction between twins, martensites, and dislocations provides a double/triple increase in microhardness (from HV_0.2 = 2.78 GPa to HV_0.2 = 6–7.69 GPa). After HFMI, scratch tests showed lower restored depths of scratch tracks and a 36–68% deceleration in the wear rate regarding those of the initial deposit. The underlying wear mechanisms were assessed accounting for the SEM observations of the scratch track morphologies and a ‘counterbody penetration vs. shear stresses ratio’ map. The initial plastic deformation-related mechanism (wedge/pile-up formation) changed by HFMI to ploughing. The obtained results allow one to evaluate and predict the impact wear resistance of the hardfacing deposits under controlled impact load conditions. Full article

With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), zinc slag, lithium slag (LS), electrolytic manganese residue (EMR), phosphogypsum (PG), water treatment sludge (WTS), sewage sludge, blast furnace slag (BFS), steel slag (SS), coal fly ash (CFA), coal gasification slag (CGS), copper smelting slag (CSS), and lead smelting slag (LSS). Having been chemically processed, they exhibit complex compositions that pose challenges for further utilization. In this paper, we comprehensively review the preparation of adsorbents from IISWs as raw materials, the applications of IISW-derived adsorbents, and their adsorption mechanisms. The obtained adsorbents include modified IISWs, zeolites, porous ceramics, and composite and hybrid adsorbents. The adsorption mechanisms, such as van der Waals forces, electrostatic interactions, and π–π interactions, contribute to the rapid adsorption kinetics and high adsorption capacity observed in these adsorbents. Full article

This study investigates the thermodynamic and experimental aspects of producing a chromium–manganese ligature under high-temperature smelting conditions using low-grade iron–manganese ore and ferrosilicochrome (FeSiCr) dust as both a reducing agent and a chromium source. Thermodynamic modeling of the multicomponent Fe–Cr–Mn–Si–Al–Ca–Mg–O system was carried out using the HSC Chemistry 10 and FactSage 8.4 software packages to substantiate the temperature regime, reducing agent consumption, and conditions for the formation of a stable metal–slag system. The calculations indicated that efficient reduction of manganese oxides and formation of the metallic phase are achieved at a smelting temperature of 1600 °C with a reducing agent consumption of approximately 50 kg. Experimental smelting trials conducted in a laboratory Tammann furnace under the calculated parameters confirmed the validity of the thermodynamic predictions and demonstrated the feasibility of obtaining a concentrated chromium–manganese ligature. The resulting metallic product exhibited a high total content of alloying elements and had the following chemical composition (wt.%): Fe 35.41, Cr 41.10, Mn 8.15, and Si 4.31. SEM–EDS microstructural analysis revealed a uniform distribution of chromium and manganese within the metallic matrix, indicating stable reduction behavior and favorable melt crystallization conditions. The obtained results demonstrate the effectiveness of an integrated thermodynamic–experimental approach for producing chromium–manganese ligatures from low-grade mineral raw materials and industrial by-products and confirm the potential applicability of the proposed process for complex steel alloying. Full article