Abstract ：

In the field of precision machining, with the popularity of brittle and hard materials such as infrared windows, has become difficult for conventional diamond grinding wheels to effectively perform high-quality machining. The structuring of traditional diamond grinding wheels using a pulsed laser is a key technology to effectively improve the grinding quality of grinding wheels. In this paper, three new shark fin diamond grinding wheels (SFSGW) with different slot widths are designed based on the excellent drag-reducing and channelizing properties of shark dorsal fins. The grinding performance of traditional grinding wheels (USGW) and SFSGW magnesium fluoride ceramics was compared. The effects of SFSGW on the surface quality, surface roughness and wheel damage of the workpiece were investigated. The results showed that the surface roughness of ceramics after grinding by SFSGW was reduced by 22.15 % compared with USGW, and the surface quality was better. Proper construction increases the material removal rate of the wheel and improves the wear resistance and service life of the wheel.

Keyword ：

Laser processing Wear resistance Shark fin-like structure Precision machining MgF(2)ceramics Surface roughnes

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Abstract ：

The ageing behaviour and phase transformation of a range of Si-microalloyed low Mg/Zn ratio Al-5.0Zn-1.0Mg-Cu alloys were investigated at a temperature of 150°C by using TEM and microhardness tests. Adding Si had a important influence on the proportion of precipitates and microhardness. As Si content increased, the precipitated phase underwent a gradual transition from the T+η precipitates to the fine GPB-II precipitates. Concurrently, the microhardness exhibited a notable enhancement from 120 HV to 150 HV when the alloys were subjected to 150°C aging. Existence of small and even GPB-II phases in the Si-adding alloy was identified as underlying cause of this result. This GPB-II phase exhibited a bilayer microstructure. In core region predominantly comprise Zn, Si and Mg, and the shell region primarily consist of Zn and Cu. This structure effectively inhibited phase growth, maintaining the phases at a smaller scale and enhancing the alloy's hardening effect. © 2024 Institute of Physics Publishing. All rights reserved.

Keyword ：

Strain hardening Zinc alloys Copper alloys Vanadium alloys Tin alloys Precipitates Rockwell hardness Age hardening Si-Ge alloys Microhardness Magnesium alloys

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Abstract ：

The microstructure, mechanical properties and intergranular corrosion resistance of Al-Cu-Mn-Si-Mg-Er-Zr alloy with squeeze casting in the peak aging state at different temperatures were studied. The alloy was aged at 165 °C, 175 °C and 185 °C, and reached peak aging at 18 h, 12 h and 8 h respectively, among them, the alloy treated with 175 °C/12 h aging has the highest hardness, reaching 149 HV, and the yield strength is also the highest, which is 387 MPa. It is because the Q phase precipitated during the aging process of the alloy provides a heterogeneous nucleation site for the θ′ phase, the average size of the θ′ phase is 73.38 nm. The intergranular corrosion depth of the alloy after aging treatment at 175 °C/12 h was the deepest, reaching 284.91μm. At this time, the width of precipitation-free zone(PFZ) is the widest in the grain boundary microstructure, which is 92.21 nm, and the grain boundary precipitation phase is continuously distributed. © 2024 IOP Publishing Ltd.

Keyword ：

Intergranular corrosion Copper alloys Zircaloy Magnesium alloys Grain boundaries Manganese alloys Textures Aluminum alloys Corrosion resistant alloys Corrosive effects Corrosion resistance Nucleation Silicon alloys Aluminum corrosion Copper corrosion Simulated annealing

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Abstract ：

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification. © 2024 Elsevier B.V.

Keyword ：

Photocatalytic activity Electric fields Air cleaners Cost effectiveness Oxygen Nanosheets Nitrogen oxides Magnesium Magnesium compounds

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Abstract ：

Selective extraction of Li+ from high Mg2+/Li+ ratio brines with ionic liquid (IL) based collaborative extractants was investigated by experiments, thermodynamic analyses, and quantum chemical (QC) calculations. Effects of different IL cationic structures and organophosphorus ligands on extraction performances were studied. The results demonstrated that the system 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide + trioctyl phosphate ([HOEMIM][Tf2N] + TOP) was considered as the best extractant, with the very high extraction efficiency of Li+ (83.16 %) and separation selectivity of Li+/Mg2+ (742.11), which is higher than values reported in literature. The thermodynamic model ePC-SAFT was first extended to quantitatively predict the phase equilibria of the so-called "organic-inorganic complex strong electrolyte system" presented in this work. The molecular-level extraction mechanism was explored by QC calculation, indicating that the strong multi-site intermolecular interactions between Li+ and [HOEMIM][Tf2N] + TOP break the Li+ hydration. This work provides guidance to rationally design novel IL-based extractants for efficient extraction of Li+

Keyword ：

Quantum chemical calculation Molecular mechanism Ionic liquid Extraction of lithium ePC-SAFT

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In this study, a compressive strength prediction model for Magnesium Phosphate Cement containing solid waste materials (SW-MPC) was developed using machine learning (ML) techniques. Firstly, a database of SW-MPC compressive strength was established through the selection of solid waste materials based on their chemical compositions. Subsequently, various ML algorithms were employed to construct predictive models for SW-MPC compressive strength, and the predictive accuracy of these models was compared. Furthermore, Shapley Additive Explanations (SHAP) analysis was utilized to assess the impact of various parameters on SW-MPC compressive strength. The results revealed that the Extreme Gradient Boosting (XGB) model exhibited the highest predictive accuracy and generalization ability. Among numerous feature parameters, the curing age (Age) and phosphate type (Type_PO4) were identified as the most critical factors influencing SW-MPC compressive strength. SW-MPC compressive strength exhibited a positive correlation with the Si content (Con_Si) and Al content (Con_Al) in the solid waste materials, while it generally displayed a negative correlation with Fe content (Con_Fe). The optimal Magnesium-to-Phosphorus ratio (M/P) for SW-MPC preparation ranged from 4 to 6. Furthermore, the influence of the dosage of solid waste materials (Per_sw) on the compressive strength of SW-MPC was complex, with the optimal content being around 10% and 35%. This complexity arose from the significant impact of the interactive effects between the content of different elements in solid waste materials and Per_sw on the compressive strength of SW-MPC.

Keyword ：

Magnesium phosphate cement Solid waste materials Compressive strength prediction Machine learning

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Abstract ：

As a type of excellent rapid protective material with fast hardening and high early strength characteristics, magnesium phosphate cement (MPC) is used as the cementitious material to fabricate concrete canvas. For a thick MPC canvas, sufficient hydration reaction is crucial in keeping its integrity. Borax is used to adjust the hydration progress of MPC in warp-knitted fabrics. The effects of different borax contents (0 %, 1 %, 2 %, 3 %, 4 %, 5 %, 6 %) on the compactness of reaction products and the mechanical properties of MPC canvas are evaluated. In addition, SEM, XRD, hydration heat, and X-CT are used to systematically analyze the hydration morphology, products, exothermic process, and pore structure of MPC canvas. The results show that borax can effectively delay the setting time of MPC, addressing the issue of incomplete hydration of MPC powder in thick canvas. The 4 % borax content (B4 sample) can ensure the complete reaction in a 20 mm thick MPC canvas, achieving the maximum compressive and flexural strengths of 26.37 MPa and 4.9 MPa at 7 d, respectively. Borax effectively optimizes the pore structure of MPC canvas and achieves a dense bond at the interface between MPC and the canvas fabric with the minimum porosity of 11 % in the B4 sample. Therefore, borax is crucial for the structural of MPC canvas.

Keyword ：

Magnesium phosphate cement Borax Structural integrity Concrete canvas

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Magnesium Phosphate Cement (MPC) exhibits high strength, exceptional high-temperature resistance, and outstanding adhesion properties at the steel interface, rendering it an ideal material for fire resistive coatings on steel structures. In this study, natural brucite powder was employed as the magnesium source, while hollow glass microspheres (HGM) were utilized as functional modifiers to formulate brucite-based MPC fire resistive coatings for steel structures. This research explored the influence of the mass ratio of brucite powder to ammonium dihydrogen phosphate (M/P), the brucite particle size, and the addition of HGM on the physical, mechanical, and fire-retardant properties of the coatings. The microstructure of the brucite-based MPC before and after fire testing was examined using SEM, XRD, TG-DTG, and X-CT. The results indicated that with an M/P ratio of 2.5:1 and a brucite particle size of 75-150 mu m, the material exhibited optimal overall performance and was suitable as a matrix material for MPC. The incorporation of an appropriate amount of HGM increased the compressive strength of brucite-based MPC by 33.4 %, reduced the dry density by 20.5 %, extended the fire resistance of the structure, and decreased the thermal conductivity by 48.2 %. This can be attributed to: (i) HGM filling the pores in brucite-based MPC, creating a denser microstructure; (ii) HGM forming a closed porous structure with the MPC matrix, reducing thermal conductivity and increasing thermal resistance; (iii) The low thermal diffusivity of HGM/MPC impeded heat transfer, thereby decelerating thermal decomposition and flame propagation.

Keyword ：

Magnesium phosphate cement Pore structure Fire resistance Thermal conductivity Brucite Hollow glass microspheres

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Abstract ：

The properties of magnesium phosphate cement (MPC) are studied by measurements of setting time, flowability, compressive strength and by multiple technique analyses of pH values, calorimetry, XRD, TG, MIP and SEM taking calcium lactate (CL) content as variables. Results show that CL can significantly prolong the setting time and promote the synergetic development of compressive strength of MPC, but the addition of CL leads to a decrease in flowability of MPC. Comprehensive consideration on these properties, the optimal dosage of CL is 5%. In this case, the setting time, flowability and 1 day & 28 days compressive strength of MPC are 84 minutes, 185 mm, 40.8 MPa & 54.2 MPa, respectively. Multiple technique analyses show that the addition of CL can decrease the liquid phase pH value and hydration rate of MPC, resulting in the extension of setting time. A low content of CL (3%) can improve the reaction degree and optimize the matrix pore structure of MPC, and thus promoting the strength development (50.90 MPa increased to 65.93 MPa). However, an excessive addition of CL (7%) will lead to the decrease in reaction products and the increase in matrix porosity of MPC, resulting in a decrease in compressive strength (43.30 MPa reduced to 37.36 MPa).

Keyword ：

Magnesium phosphate cement Mechanical properties Setting time Reaction degree

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Abstract ：

This study first systematically investigated selective Li+ extraction from Mg2+-rich brines with Na+ and K+ using ionic liquid (IL) based synergistic extractant (SE) systems from molecular mechanisms to extraction performances. The ternary combination 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([AMIM] [Tf2N]), tri-iso-butyl phosphate (TIBP) and dichloromethane (DCM), i.e., [AMIM][Tf2N]-TIBP-DCM was selected as a suitable SE from the diverse organic phosphorus ligands, ILs and diluents. The single-stage Li+ extraction efficiency was as high as 96.87%, and selectivities of beta Li+/Mg2+, beta Li+/Na+, and beta Li+/K+were up to 1161.94, 76.74, and 1263.46, respectively. It was found that Li+ is extracted from the aqueous phase to organic phase in Li+-4TIBP[Tf2N] complex. The molecular-level mechanism was identified as the multi-type interaction formed between metal ions and [AMIM][Tf2N]-TIBP to destroy the hydration of metal ions through quantum chemical (QC) calculations. The work proposes valuable theoretical guidance to develop novel IL-related SE systems for the high-efficiency Li+ extraction from salt lake brines.

Keyword ：

Extraction of lithium Quantum chemical calculation Synergistic extractant Ionic liquid Magnesium -rich brine Molecular mechanism

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