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The present study was to reduce the adhesion and wear that happened on the rake face during machining of Ti6Al4V alloys by employing volcano-like textured coated tools. A combination of experimental and simulative investigation was adopted. DEFORM-3D software with updated Lagrangian formulation was used for numerical simulation, and the thermo-mechanical analysis was performed using Johnson–Cook material model to predict the cutting forces, cutting temperature, chip morphology, and tool wear. In cutting experiments, volcano-like textures with different area densities (10%, 20%, 30%) were fabricated by fiber laser on the rake face of cemented carbide tools close to the main cutting edge. Then, these textured tools were deposited with CrAlN coating through cathodic vacuum arc ion plating technique. Experiments in cutting Ti6Al4V alloys were carried out with the textured coated tools and non-textured coated tool under dry and wet cutting conditions. Then, cutting forces, chip morphology, and tool wear were investigated. The results showed that textured coated tools were superior to the conventional tool. Especially in wet cutting, the main cutting force and radial force of the coated tool with texture area density of 20% (VCT2) were reduced by 11.6% and 21.25%, respectively. Surface morphology of VCT2 tool had lower workpiece adhesion on the rake face. Therefore, VCT2 tool showed a better cutting performance. Finally, the mechanisms of textured coated tools under wet cutting conditions were proposed.

HighlightsThe representatively engineering strategies of cations/anions doping, bimetallic/bi-anionic transition metal compounds and heterostructure composites catalysts for lithium sulfur batteries are comprehensively reviewed.The promoted mechanism of catalytic performance by regulating electronic structure is focused on, including energy band, electron filling, d/p-band center, valence state.The superiority of the modified transition metal compounds is comprehensively summarized.Engineering transition metal compounds (TMCs) catalysts with excellent adsorption-catalytic ability has been one of the most effective strategies to accelerate the redox kinetics of sulfur cathodes. Herein, this review focuses on engineering TMCs catalysts by cation doping/anion doping/dual doping, bimetallic/bi-anionic TMCs, and TMCs-based heterostructure composites. It is obvious that introducing cations/anions to TMCs or constructing heterostructure can boost adsorption-catalytic capacity by regulating the electronic structure including energy band, d/p-band center, electron filling, and valence state. Moreover, the electronic structure of doped/dual-ionic TMCs are adjusted by inducing ions with different electronegativity, electron filling, and ion radius, resulting in electron redistribution, bonds reconstruction, induced vacancies due to the electronic interaction and changed crystal structure such as lattice spacing and lattice distortion. Different from the aforementioned two strategies, heterostructures are constructed by two types of TMCs with different Fermi energy levels, which causes built-in electric field and electrons transfer through the interface, and induces electron redistribution and arranged local atoms to regulate the electronic structure. Additionally, the lacking studies of the three strategies to comprehensively regulate electronic structure for improving catalytic performance are pointed out. It is believed that this review can guide the design of advanced TMCs catalysts for boosting redox of lithium sulfur batteries.

Lacustrine shale oil has the potential to lead the development of China's oil and gas industry. By integrating scanning electron microscopy, low-temperature CO2 and N2 adsorption, high-pressure mercury intrusion, and nuclear magnetic resonance with centrifugation at different speeds, the pore system and pore fluid distribution of Da’anzhai Member lacustrine shale in the Sichuan Basin are studied. The results show that: (1) The reservoir space is mainly inorganic pores and micro-fractures. Nano-micron scale pores are commonly found and widely distributed in the Da’anzhai shale with multiple peaks of 28 nm, 200 nm, 900 nm, and 3.5 µm. The total pore volume ranges from 0.00849 to 0.02808 cm³/g, and the pores ranging from 100 nm to 1000 nm are the main contributors to total pore volume. (2) Pore fluid can be divided into movable oil, bound oil, and adsorption oil. The proportion of movable oil, bound oil, and adsorbed oil is 21.4%, 12.4%, and 66.2% in Da’anzhai shale, respectively. Movable oil mainly occurs in pores larger than 350 nm, bound oil is 30–350 nm, while adsorbed oil mainly exists in pores below 30 nm. (3) The higher the total organic carbon content and clay minerals content, the smaller the pore size, resulting in the low content of movable oil. The higher the content of brittle minerals such as quartz, the better the development of intergranular pores and microfractures, and the higher the content of movable oil. Through the grading evaluation of shale pore structure and pore fluid, it is conducive to guide the exploration and development of Da’anzhai shale oil, which has important theoretical and practical significance.

The nickel (Ni)-based alloy cladding layers on the surface of 6061 aluminum alloy are fabricated successfully using an optimized laser cladding process. An analysis has been conducted to compare the influence of two types of Ni-based powders on the phase composition, macroscopic morphology and microstructure of the cladding layers. The study also elucidates the micro-hardness and friction property of the cladding layers fabricated by two types of Ni-based powders. The results reveal that phases including Al3Ni, Al3Ni2, and α-Al are formed in the pure Ni cladding layer. Nonetheless, in the Ni–Cr–B–Si cladding layer, a new phase characterized by needle-shaped Cr7C3 is observed. Mechanical properties characterization of the cladding layers reveals a notable improvement in microhardness and friction properties compared to the 6061 aluminum alloy substrate. The best properties are achieved in the Ni–Cr–B–Si cladded layer, which demonstrates a microhardness of 714 HV, almost 8.1 times superior to that of the substrate. Its friction and wear rate is merely 21% of that of the base aluminum. Our results are expected to provide significant insights into the design and production of aluminum materials with great resistance to wear.

Pore structure plays a critical role in evaluating shale “sweet spots”. Compared to marine shale, lacustrine shale has more diverse lithofacies types and greater heterogeneity in pore structure due to frequently changing environmental conditions. Using methods such as mercury intrusion porosimetry (MIP), field emission scanning electron microscopy (FE-SEM), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD), this study investigates the micropore structures and heterogeneity of different lithofacies in the Jurassic Dongyuemiao Member lacustrine shale. Image processing and multifractal theory were employed to identify the controlling factors of pore structure heterogeneity. The key findings are as follows. (1) Based on mineral content and laminae types, the lithofacies types of Dongyuemiao lacustrine shale are classified into four types: shell–laminae mixed shale (SLMS), silty–laminae clay shale (SLCS), clast–laminae clay shale (CLCS), and clay shale (CS). (2) Based on genesis, shale reservoirs’ pore and permeability space are categorized into inorganic pores, organic pores, and micro-fractures. Inorganic pores consist of inter-particle pores and intra-particle pores. Pore size distribution curves for all four lithofacies exhibit two main peaks, with pore sizes concentrated in the ranges of 2–10 nm and 50–80 nm. Mesopores and macropores dominate, accounting for over 80% of the total pore volume. Mesopores are most developed in CLCS, representing 56.3%. (3) Quartz content is positively correlated with the multifractal dimension, while clay content shows a negative correlation. Higher quartz content, coupled with lower clay content, weakens pore structure heterogeneity. A negative correlation exists between total organic carbon (TOC) and the multifractal dimension, indicating that higher organic matter content enhances organic pore development and increases microscopic heterogeneity. (4) Porosity heterogeneity in SLMS is effectively characterized by D0-Dmax, while in the other three lithofacies, it is characterized by Dmin-D0. Permeability across all lithofacies correlates with D0-Dmax. In CS, SLMS, and SLCS, permeability is positively correlated with D0-Dmax, with higher values indicating greater permeability heterogeneity. In CLCS, permeability is negatively correlated with D0-Dmax, such that lower values reflect stronger heterogeneity.

Micro- and nano-scale pores develop in shale reservoirs, and the associated pore structure controls the occurrence state, gas content, seepage capacity, and micro-migration and accumulation mechanisms of shale gas. For this study, we mainly conducted tests, using field emission-scanning electron microscopy, of the isothermal methane adsorption of powder-sized samples under high temperatures (60–130 °C) and pressures (0–45 MPa), along with methane-saturated nuclear magnetic resonance tests of plug-sized samples under different temperatures (60–100 °C) and pressures (0–35 MPa). These samples were from Longmaxi shale cores from strata at different burial depths from the Zhaotong, Weiyuan, and Luzhou areas. As the burial depth increases, organic pores transform from complex networks to relatively isolated and circular pore-like structures, and the proportion of organic matter-hosted pores increases from 25.0% to 61.2%. The pore size is influenced by the pressure difference inside and outside the pores, as well as the surface tension of organic matter in situ. As the burial depth increases to 4200 m, the main peak of the pore size first increases from 5–30 nm to 200–400 nm and then decreases to 50–200 nm. This work establishes an NMR method of saturated methane on plug-sized samples to test the free gas content and develop a prediction model of shale reservoirs at different burial depths. The gas content of a shale reservoir is influenced by both burial depths and pore structure. When the burial depth of the shale gas reservoir is less than 2000 m, inorganic pores and microfractures develop, and the self-sealing ability of the reservoir in terms of retaining shale gas is weak, resulting in low gas content. However, due to the small pore size of organic pores and the low formation temperature, the content of adsorbed gas increases, accounting for up to 60%. As the burial depth increases, the free gas and total gas content increase; at 4500 m, the total gas content of shale reservoirs is 18.9 m3/t, and the proportion of free gas can be as high as 80%. The total gas content predicted by our method is consistent with the results of the pressure-holding coring technique, which is about twice our original understanding of gas content, greatly enhancing our confidence in the possibility of accelerating the exploration and development of deep shale gas.

To improve the forming quality of V-shaped clamps, a basis for optimal V-shaped clamp mold surface design is provided. In this paper, the V-shaped clamp stamping process is simulated using Abaqus and the influence of the mold’s friction coefficient on the V-shaped clamp stamping parameters is revealed. The regional friction coefficient of the V-shaped clamp mold surface is optimized using an equal horizontal design scheme and the optimal friction coefficient combination for the mold surface is obtained, along with comparison and analysis of the molding parameters before and after optimization. Results show that the mold’s surface friction properties have significant regional characteristics. Increasing the friction coefficient of the bottom, the rounded section of the punch’s V-shaped groove and the bulge filleted corner of the punch while reducing the friction coefficient of the bulge filleted corner and crimping area of the die head contributes to the material flow. Mold surface optimization makes the material flow velocity more uniform, disperses stress on the part’s surface, reduces strain and thickness reduction of the key parts, and improves overall quality. Measurements show that the V-shaped clamp mold’s surface friction characteristics affect the molding parameters significantly and mold optimization improves the V-shaped clamp’s molding quality.

The phenomenon of pressure-solution (PS) is widespread in deep marine shale reservoirs of the Longmaxi Formation in the Sichuan Basin, affecting pore development. However, systematic reports on the study of PS in shale reservoirs are yet to be seen. This study performed large-field scanning electron microscopy, mineral quantitative identification, low-pressure gas adsorption, and high-pressure mercury injection experiments on shale cores from the Longmaxi Formation. The pore structure characteristics and the PS process of deep shale reservoirs were clarified, a semi quantitative analysis method for PS was constructed, and the influence of PS on pore development was explored. Our results demonstrate that PS is widely present in deep gas shale reservoirs, primarily manifesting in the form of mineral transformation and fusion, particularly involving clay and quartz minerals. This process alters the mineral composition and particle size of the shale reservoirs. A semi-quantitative analysis method for PS and the action strength parameter QP has been established, based on the mineral composition and particle size of shale reservoirs. This parameter exhibits a positive correlation with burial depth, water saturation, and quartz content. The primary effect of PS on pore development is that, as mineral transformation results in an elevation of quartz content and an increase in particle size, pore dimensions undergo compression and subsequently diminish. This underscores why shale reservoirs containing over 70% quartz are unfavorable for pore development. Therefore, when the water saturation in the Longmaxi Formation shale reservoir exceeds 40% and the quartz content surpasses 70%, significant risks are present in the exploration and development of shale gas.

Tool-chip adhesion impacts on cutting performance significantly, especially in finish cutting process. To promote cutting tools’ anti-adhesion property, the concave micro-grooves texture (MGT) and convex volcano-like texture (VLT) were fabricated separately on lathe tools’ rake faces by laser surface texturing (LST). Various orientations of MGT and different area densities (9% and 48%) and regions (partial and full) of VLT were considered in textured patterns designing. The following orthogonal cutting experiments, machining of aluminum alloy 5038, analyzed tools’ performances including cutting force, cutting stability, chip shape, rake face adhesion and abrasion. It indicated that under dry finish cutting conditions, MGT contributed to cutting stability and low cutting forces, meanwhile friction and normal force reduced by around 15% and 10%, respectively with a weak correlation to the grooves’ orientation. High density VLT tools, on the other hand, presented an obvious anti-adhesion property. A 5 μm reduction of crater wear’s depth can be observed on textured rake faces after long length cutting and textured rake faces presented half size of BUE regions comparing to the flat tool, however, once the texture morphologies were filled or worn, the anti-adhesion effect could be invalid. The bearing ratio curve was employed to analysis tool-chip contact and durability of textured surfaces contributing to a better understanding of anti-adhesion and enhanced durability of the textured tools.

To mitigate the exploration and development risks, it is necessary to have a deeper understanding of the formation mechanism and gas-bearing control factors of low-resistance shale reservoirs. This study focuses on typical shale gas wells (including low-resistivity wells) in Luzhou area, and identification criteria for low-resistance shale reservoirs are redefined as resistivity less than 10 Ω·m and continuous formation thickness greater than 6 m. At the macro scale, low-resistivity shale reservoirs are characterized by high clay mineral content and high water saturation with low gas content. At the micro scale, the main pore size is less than 10 nm, with a small total pore volume but a large specific surface area. Shale reservoirs close to the Class II fault have high water saturation and strong compaction, which hinders the mutual transformation between minerals, resulting in low-resistivity shale with high clay mineral content, small pore volume, and pore size, which promotes the enhancement of reservoir conductivity. The gas content of low-resistivity shale reservoirs is lower, because the distance from the Class II fault is closer, resulting in high water saturation and strong diagenesis, which is not conducive to pore development and shale gas accumulation. When the water saturation exceeds 40%, the pore volume of shale reservoirs rapidly decreases to as low as 0.0074 cm3/g. In order to reduce the risk of exploration and development of the area, the well location deployment needs to be more than 2.8 km away from the Class II fault.