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Enhanced in-vitro degradation resistance and cytocompatibility of a thermomechanically processed novel Mg alloy:Insights into the role of microstructural attributes

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Journal of Magnesium and Alloys 2024年第2期12卷 700-725页

作者： Darothi Bairagi Santanu Mandal Mangal Roy Manas Paliwal Sumantra Mandal department of metallurgical and Materials Engineering Indian Institute of TechnologyKharagpur 721302India

The role of microstructural features on in-vitro degradation and surface film development of a thermomechanically processed Mg-4Zn-0.5Ca-0.8Mn alloy has been investigated employing electrochemical studies,scanning electron microscopy and X-ray photoelectron spectroscopy.The specimen forged at 523 K temperature developed a coarse unimodal microstructure consisting of basal oriented grains,whereas the specimens forged at 623 K and 723 K temperatures exhibited bimodal microstructures containing randomly oriented fine grains and basal oriented coarse grains.The bimodal microstructures exerted higher resistance to corrosion compared to the unimodal microstructure in presence of a protective surface film.The optimum size distribution of fine and coarse grains as well as the prevalence of basal oriented grains led to the lowest anodic current density in the specimen forged at 623 K.The morphology of Ca_(2)Mg_(6)Zn_(3)precipitates governed the cathodic kinetics by controlling the anode to cathode surface area ratio.Despite the specimen forged at 723 K comprised comparatively lower fraction of precipitates than at 623 K,the mesh-like precipitate morphology increased the effective cathodic surface area,leading to enhanced localised corrosion in the former specimen.Optimal microstructural features developed at 623 K forging temperature formed a well-protective surface film with lower Mg(OH)_(2)to MgO ratio,exhibiting distinctly high polarization resistance and superior cytocompatibility in terms of cell-proliferation and cell-differentiation.

关键词： Magnesium alloy Microstructure Corrosion Electrochemical impedance spectroscopy X-ray photoelectron spectroscopy Cytotoxicity

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Direct microwave leaching conditions of rare earth elements in fluorescent wastes

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Journal of Rare Earths 2024年第6期42卷 1165-1174,I0007页

作者： A.Bilen B.Birol M.N.Saridede S.S.Kaplan M.S.Sonmez department of metallurgical and Materials Engineering Yildiz Technical UniversityIstanbulTurkey department of Chemical Engineering and Materials Science Stevens Institute of TechnologyNew JereyUSA department of metallurgical and Materials Engineering Istanbul Technical UniversityIstanbulTurkey

The luminescent phosphor powder in the fluorescent lamp constitutes 2%of the lamp’s weight.It can be mentioned that fluorescent wastes are a crucial raw material to produce rare earth oxides.In the present study,microwave leaching process was conducted to dissolve rare earth elements yttrium(Y),europium(Eu),and remaining rare earth elements(REEs)present in the phosphor powder of the fluorescent lamp.and the yields were compared.In the microwave leaching process,the effects of the temperature(80-160℃),acid type(hydrochloric acid(HCl),nitric acid(HNO_(3)),sulphuric acid(H_(2)SO_(4))),acid concentration(0.5-6 mol/L),solid to liquid ratio(0.1:10-0.5:10)and reaction time(5-90 min)parameters on leaching efficiencies of varying rare earth elements and calcium were investigated.The highest yield was obtained in the direct microwave leaching of fluorescent waste with the experimental conditions of 6 mol/L HCl,160℃,0.1:10 solid-to-liquid ratio(S:L),and 90 min.Activation energy calculations were made,and kinetic models of the reactions were obtained,and it is observed that Y and Eu dissolution is diffusion-controlled,on the other hand,lanthanum(La),cerium(Ce),and terbium(Tb)were examined to be chemical reaction controlled.Moreover,calcium(Ca)and gadolinium(Gd)seem coherent with the mixed model.Concurrently,mathematical models of all experimental studies are created with the response surface Box-Behnken method and the correlation coefficients of all the models are over 90%.

关键词： Rare earth elements(REEs) Direct microwave leaching Fluorescent waste Kinetic models Response surface method

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Slope stability of reclaimed coal mines through a new water filling index

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 828-839页

作者： Antonios Mikroutsikos Alexandros I.Theocharis Nikolaos C.Koukouzas Ioannis E.Zevgolis Chemical Process&Energy Resources Institute Centre for Research&Technology HellasAthensGreece School of mining and metallurgical Engineering National Technical University of AthensAthensGreece

A common reclamation practice for closed coal surface mines is filling them with water to form pit lakes.The creation and sustainability of these lakes are significantly affected by the stability of the corresponding slopes.The present study provides a general framework for analyzing the water filling’s effect on slope stability based on a new water filling index,which can indirectly consider the factors affecting the process and efficiently quantify the filling speed’s influence.The assumptions of the proposed approach are thoroughly discussed,and the range of the water filling index is identified.Furthermore,the safety factor is calculated using the finite element method with the shear strength reduction technique during the filling process for various conditions(soil properties,slope geometry,hydraulic conditions,and water filling speed).Results are presented as normalized stability charts for practical use.During the water filling,the stability gradually decreases until the reservoir reaches a critical level of 10%e40%of the total height;it then increases to even more stable conditions than the initial one.Overall,the present analysis allows for the preliminary stability evaluation of a coal mine during the formation of a pit lake and the appropriate quantification of the water filling’s effect.

关键词： Post-coal era Open-pit flooding Stability charts Critical level

Optimizing calcination of coal by-products for maximizing REE leaching recovery and minimizing Al,Ca,and Fe contamination

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Journal of Rare Earths 2024年第7期42卷 1354-1365页

作者： Tushar Gupta Ahmad Nawab Rick Honaker MP Materials Mountain Pass Mine department of mining Engineering University of Kentucky

High-temperature calcination is effective in improving the leaching characteristics of rare earth elements(REEs) from conventional REE-bearing minerals by transforming them into more leachable forms.However,the recovery of contaminants such as Al,Fe,and Ca also increases significantly.The objective of the study was to maximize the REE extraction while minimizing the concentration of contaminant ions(Al,Ca,and Fe) in the leach solution.Representative density fractions of the coarse refuse from the Baker and Fire Clay seam coal refuse were pulverized to a top size of 180 μm and used as a feedstock for the study.All the samples generated from thermal treatment were leached at 1%(w/v) using 1.2 mol/L sulfuric acid at 75℃ for 2 h.Test results from a parametric program based on a Box-Behnken design were used for modeling and optimization of three operating parameters associated with the lab-scale calcination process.The parameters included temperature(400-800℃),ramp rate(2-10℃/min) and holding time(0-120 min).It was determined that the calcination temperature was the most significant parameter influencing REE recovery.The majority of the heavy rare earth elements(HREEs) were found to be present in an insoluble form in the calcination products and were marginally affected by thermal treatment.A strong correlation between light rare earth elements recovery(LREEs) and Al suggested a possible association with clays.The optimum operating conditions for high REE recovery with comparatively lower contaminant concentration for 1.6 specific gravity float and 2.2 sink fractions of Baker and Fire Clay seam material were determined to be at 776,800℃ and 407,800℃,calcining temperatures,respectively.A higher optimum temperature of 1.6 float fraction of Baker seam relative to Fire Clay seam material was due to elevated pyrite concentration in Baker seam material.Thermal treatment at 400℃ converted pyrite into a soluble intermedium iron oxide,resulting in a high Fe content in the leachate.Calcining at 776℃ converted most of the solubl

关键词： Calcination Coal refuse Optimization Rare earth elements

Evolution of inclusions in vacuum induction melting of superalloys containing 70%return material

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Journal of Iron and Steel Research(International) 2024年第3期31卷 719-728页

作者： Jin-guo Gao Shu-lei Yang Shu-feng Yang Jing-she Li Wei Liu Meng-jing Zhao An-ren Wang School of metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China metallurgical and Building Materials Business department China International Engineering Consulting CorporationBeijing 100048China

The variation law of inclusions type and size in the vacuum induction melting process and ingot of Ni-based superalloy containing 70%return material was studied by industrial test sampling,and the mechanism of inclusions formation was analyzed with thermodynamic calculations.The results show that there are mainly two types of composite inclusions in the vacuum induction melting of Ni-based superalloys,which are nitride-and oxide-based composite inclusions,like Al_(2)O_(3)-SiO_(2)-Cr_(2)O_(3),TiN-(Mo,Nb)C,etc.The type and proportion of inclusions from the center to the edge of the vacuum induction ingot did not change significantly.The number density of inclusions from the center to the edge of the ingot varied less,and the size of inclusions became smaller from the center to the edge.In addition,thermodynamic calculations show that oxides(M_(2)O_(3))are present in the liquid phase and mainly contain Al,Ti,Cr,Fe and O elements.The nitride consists mainly of Ti and N and contains small amounts of Cr,C,Nb,and Mo elements.This is consistent with the results of industrial tests.As the temperature decreases,the precipitation phases such as M_(2)O_(3),MN,γ,MC,δ,γ'andμphases are gradually precipitated,where oxides and nitrides are present in the liquid phase.The contents of O and N elements are the main influencing factors for the inclusions content and precipitation temperature;when the nitrogen content is reduced to below 0.0015%,it can make MN precipitate below the liquid-phase line.

关键词： Ni-based superalloy Vacuum induction melting Return material Inclusion Thermodynamic

Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

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International Journal of mining Science and Technology 2024年第5期34卷 643-654页

作者： Ahmad F. Zueter Mohammad Zolfagharroshan Navid Bahrani Agus P. Sasmito department of Civil and Resource Engineering Dalhousie University department of mining Engineering Mc Gill University

Current practice of underground artificial ground freezing(AGF) typically involves huge refrigeration systems of large economic and environmental costs. In this study, a novel AGF technique is proposed deploying available cold wind in cold regions. This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer. A refrigeration unit can be optionally integrated to meet additional cooling requirements. The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed, resulting in:(1) steering the cooling resources(cold wind or refrigeration) towards zones of interest; and(2) minimizing refrigeration load. This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon. Two Canadian mines are considered: the Cigar Lake Mine and the Giant Mine. The results show that our proposed design can speed the freezing time by 30% at the Giant Mine and by two months at the Cigar Lake Mine. Further, a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine. Overall, this study provides mining practitioners with sustainable solutions of underground AGF.

关键词： Artificial ground freezing Underground mining Sustainable mining Thermosyphon Air insulation Cold regions

Effect of BaO and MgO on structure and properties of aluminate slag with various CaO/Al_(2)0_(3)ratios

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Journal of Iron and Steel Research(International) 2024年第1期31卷 204-214页

作者： Yu-qi Kong Ting Wu Wen-zhi Xia Wen Yang Hai-chuan Wang School of metallurgical Engineering Anhui University of TechnologyMa’anshan243032AnhuiChina Key Laboratory of metallurgical Emission Reduction and Resource Recycling(Ministry of Education) Anhui University of TechnologyMa’anshan243002AnhuiChina

To provide theoretical guidance for performance stability control of low-reactive mold fluxes,the effects of BaO and MgO on the structure and properties of aluminate slag with various CaO/Al_(2)0_(3)(C/A)ratios were investigated using the Fourier transform infrared spectrometer,Raman spectroscope,hemispherical melting point instrument,rotational viscometer and X-ray diffractometer.The results indicated that with BaO and MgO addition,the structure polymerization was first weakened and then enhanced at C/A of 1.1,and the transition contents corresponded to 8 wt.%BaO and 2 wt.%MgO,respectively,while the structure polymerization decreased continuously at C/A of 1.3.Since the viscosity change was well consistent with the structure evolution,the polymerization degree played a more prominent role in the slag viscosity than superheat degree when the melting temperature difference was within 40℃.The break temperature decreased initially and then increased with augment of BaO and MgO at C/A of 1.1,while it manifested a decrease trend with BaO addition,and it decreased obviously but then turned to increase with MgO increment at C/A of 1.3.The crystallization phase and crystallization ratio kept stable with BaO increment,while the crystallization ratio rose greatly with MgO promoting LiAlO_(2)precipitation at C/A of 1.1.The crystal types of all experimental slags were mainly Ca_(12)Al_(14)O_(33)and CaF_(2)at C/A of 1.3,and the precipitation of crystalline phase BaAl2O4 demonstrated a rising trend,while that of Ca_(12)Al_(14)O_(33)gradually declined with BaO augment.

关键词： Aluminate slag Structure MgO BaO Viscosity Property

Numerical modelling of post-failure behaviors of coal specimens

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 514-531页

作者： Ajeet Yadav Bhaskara Behera Gauri Shankar Prasad Singh Sanjay Kumar Sharma department of mining Engineering Indian Institute of Technology(Banaras Hindu University)VaranasiUttar Pradesh221005India

A modelling approach consisting of best-fit relations to estimate the post-yield strength parameters is presented for simulating post-peak behavior beyond the point of residual strength of coal pillars having different w/h ratios.The model was developed based on back-analysis of the complete stress-strain behavior of specimens belonging to six different Indian coal seams with different w/h ratios of 0.5 e13.5.It was found that the simultaneous degradation of the cohesion and friction angle of the Mohr-Coulomb rock material characterizes the post-peak strength behavior of the rock.The resulting expressions are simplistic as they require parameters that can be easily determined using uniaxial and triaxial compression results.Eventually,the developed model was validated by simulating the triaxial tests of coal specimens with different sizes under varying confining stresses and comparing its findings with the published test results.The study showed that its implementation in the numerical model could reproduce laboratory-observed mechanical response,deformation behavior,and failure mechanism very closely.

关键词： Strain softening Dilatancy Interface Shape effect Residual strength

Effect of austenitizing condition on mechanical properties,microstructure and precipitation behavior of AISI H13 steel

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Journal of Iron and Steel Research(International) 2024年第1期31卷 143-156页

作者： An-gang Ning Yang Liu Rui Gao Stephen Yue Ming-bo Wang Han-jie Guo College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan030024ShanxiChina department of mining and Materials Engineering McGill UniversityMontrealQCH3A 0C5Canada ASSAB Tooling Technology(Chongqing)Co. Ltd.Chongqing401120China School of metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China

The effects of austenitizing temperature(1223,1303,and 1373 K)and holding time(1-1500 s)on the microstructure,mechanical properties,and precipitation behavior of the H13 hot work die steel were investigated.The results indicate a softening phenomenon when H13 steel is austenitized at 1303 K beyond 900 s and 1373 K beyond 600 s,respectively.For the sample held for 1200 s,the tensile strength is found capable of reaching up to 2.2 GPa when quenched from a temperature above 1303 K.Meanwhile,prior-austenite grain size increases with the increase in austenitizing temperature.The kinetic behavior of the precipitates(mainly MC-type carbides)in H13 steel could be elaborated through the principles set forth by the Arrhenius and Avrami equations.Finally,the comprehensive strengthening of the H13 steel was discussed in detail.The results show that the activation energy of the transformed fraction of carbides is higher than that of the diffusion process for common alloying elements(Cr,V,Mo,and Ni)found in the austenite.This suggests that it would be difficult for precipitates to dissolve into the matrix when H13 steel is austenitized at high temperatures.With the increasing austenitizing temperature,the precipitation fraction decreases,and the dislocation density increases.The dislocation strengthening is regarded as the dominant strengthening contributed to yield strength in as-quenched H13 steel.

关键词： H13 steel Austenitizing Mechanical property Precipitation behavior Comprehensive strengthening