Investigation of bubbles escape behavior from low basicity mold flux for high-Mn high-Al steels using 3D X-ray microscope

During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.

Role of iron ore in enhancing gasification of iron coke:Structural evolution,influence mechanism and kinetic analysis

The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.

MOF-based quasi-solid-state electrolyte for long-life Al-Se battery

Aluminum-selenium(Al-Se)batteries,which possess a high theoretical specific capacity of 1357 mA h g^(-1),represent a promising energy storage technology.However,they suffer from significant attenuation of capacity and low cycle life due to the shuttle effect.To mitigate the shuttle effect induced by soluble selenium chloroaluminate compound that tends to migrate towards the negative electrode,a quasi-solid-state Al-Se battery was fabricated through the synthesis of a multi-aperture structure quasisolid-state electrolyte(MOF@GPE)based on metal-organic framework(MOF)material and gel-polymer electrolyte(GPE).The high ionic conductivity(1.13×10^(-3)S cm^(-1))of MOF@GPE at room temperature,coupled with its wide electrochemical stability window(2.45 V),can facilitate ion transport kinetics and enhance the electrochemical performance of Al-Se batteries.The MOF@GPE-based quasi-solidstate Al-Se batteries exhibit outstanding long-life cycling stability,delivering a high specific discharge capacity of 548 mA h g^(-1)with a maintained discharge specific capacity of 345 mA h g^(-1)after 500 cycles at a current density of 200 mA g^(-1).The stable ion transmission and high ion transport kinetics in MOF@GPE can be attributed to the stable structure and permeable channel of MOF,which effectively captures the soluble selenium chloroaluminate compound and further restrains the shuttle effect,resulting in improved cycling performance.

Competitive oxidation behavior of Ni-based superalloy GH4738 at extreme temperature

A high thrust-to-weight ratio poses challenges to the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperatures has been investigated by isothermal and non-isothermal experiments. As a result of the competitive diffusion of alloying elements, the oxide scale included an outermost porous oxide layer (OOL), an inner relatively dense oxide layer (IOL), and an internal oxide zone (IOZ), depending on the temperature and time. A high temperature led to the formation of large voids at the IOL/IOZ interface. At 1200℃, the continuity of the Cr-rich oxide layer in the IOL was destroyed, and thus, spallation occurred. Extension of oxidation time contributed to the size of Al-rich oxide particles with the increase in the IOZ. Based on this finding,the oxidation kinetics of GH4738 was discussed, and the corresponding oxidation behavior at 900-1100℃ was predicted.

Development and prospects of molten steel deoxidation in steelmaking process

In the long traditional process of steelmaking,excess oxygen is blown into the converter,and alloying elements are used for deoxidation.This inevitably results in excessive deoxidation of products remaining within the steel liquid,affecting the cleanliness of the steel.With the increasing requirements for steel performance,reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary.After more than a hundred years of development,the total oxygen content in steel has been reduced from approximately 100×10^(-6)to approximately 10×10^(-6),and it can be controlled below 5×10^(-6)in some steel grades.A relatively stable and mature deoxidation technology has been formed,but further reducing the oxygen content in steel is no longer significant for improving steel quality.Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process.The technology combines silicon–manganese predeoxidation,ladle furnace diffusion deoxidation,and vacuum final deoxidation.We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation.Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4×10^(-6) and 8×10^(-6),altering the type of inclusions,eliminating large particle Ds-type inclusions,improving the flowability of the steel liquid,and deriving a higher fatigue life.The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.

Hybrid model for BOF oxygen blowing time prediction based on oxygen balance mechanism and deep neural network

The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.

Cross-upgrading of biomass hydrothermal carbonization and pyrolysis for high quality blast furnace injection fuel production:Physicochemical characteristics and gasification kinetics analysis

The paper proposes a biomass cross-upgrading process that combines hydrothermal carbonization and pyrolysis to produce high-quality blast furnace injection fuel.The results showed that after upgrading,the volatile content of biochar ranged from 16.19%to 45.35%,and the alkali metal content,ash content,and specific surface area were significantly reduced.The optimal route for biochar pro-duction is hydrothermal carbonization-pyrolysis(P-HC),resulting in biochar with a higher calorific value,C=C structure,and increased graphitization degree.The apparent activation energy(E)of the sample ranges from 199.1 to 324.8 kJ/mol,with P-HC having an E of 277.8 kJ/mol,lower than that of raw biomass,primary biochar,and anthracite.This makes P-HC more suitable for blast furnace injection fuel.Additionally,the paper proposes a path for P-HC injection in blast furnaces and calculates potential environmental benefits.P-HC of-fers the highest potential for carbon emission reduction,capable of reducing emissions by 96.04 kg/t when replacing 40wt%coal injec-tion.

Evolution of microstructure and properties of a novel Ni-based superalloy during stress relief annealing

We discussed the decrease in residual stress,precipitation evolution,and mechanical properties of GH4151 alloy in different annealing temperatures,which were studied by the scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),and electron backscatter diffraction(EBSD).The findings reveal that annealing processing has a significant impact on diminishing residual stresses.As the annealing temperature rose from 950 to 1150℃,the majority of the residual stresses were relieved from 60.1 MPa down to 10.9 MPa.Moreover,the stress relaxation mechanism transitioned from being mainly controlled by dislocation slip to a combination of dislocation slip and grain boundary migration.Meanwhile,the annealing treatment promotes the decomposition of the Laves,accompanied by the precipitation ofμ-(Mo_(6)Co_(7))starting at 950℃ and reaching a maximum value at 1050℃.The tensile strength and plasticity of the annealing alloy at 1150℃ reached the maximum(1394 MPa,56.1%)which was 131%,200%fold than those of the as-cast alloy(1060 MPa,26.6%),but the oxidation process in the alloy was accelerated at 1150℃.The enhancement in durability and flexibility is primarily due to the dissolution of the brittle phase,along with the shape and dispersal of theγ′phase.

Hydrometallurgical process and recovery of valuable elements for limonitic laterite:A review

Nickel is a strategic resource in social life and defense technology,playing an essential role in many fields,such as alloys and batteries.With the decrease in nickel sulfide,it is of great significance to extract nickel from laterite.The limonitic laterite is a kind of rich nickel-cobalt-scandium resource.At present,there are few reviews on the extraction of limonitic laterite.This study reviews the hydrometallurgical processes for limonitic laterite ores and the methods of recovering valuable elements.The mineralogical characteristics are analyzed,and the typical mineral compositions are summarized.The main hydrometallurgical processes are compared and discussed,including reduction roasting-ammonia leaching,sulfuric acid pressure leaching,nitric acid pressure leaching,and the atmospheric nitric acid leaching(DNi process).The methods of recovering nickel,cobalt,scandium,and iron are emphatically outlined.Finally,reasonable suggestions are proposed for comprehensive utilization.This study can provide a reference for industrial development and diversified applications.

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.

A review of in-situ high-temperature characterizations for understanding the processes in metallurgical engineering

For the rational manipulation of the production quality of high-temperature metallurgical engineering,there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors.To overcome this issue,various in-situ characterization methods have been recently developed to analyze the interactions between the composition,microstructure,and solid-liquid interface of high-temperature electrochemical electrodes and molten salts.In this review,recent progress of in-situ hightemperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering.In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction(s-XRD),laser scanning confocal microscopy,and X-ray computed microtomography(X-rayμ-CT),which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces.In addition,laser-induced breakdown spectroscopy,high-temperature Raman spectroscopy,and ultraviolet-visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts.More importantly,the combination of X-rayμ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface.Therefore,these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.

Preparation of lithium-ion battery anode materials from graphitized spent carbon cathode derived from aluminum electrolysis

Graphitized spent carbon cathode(SCC)is a hazardous solid waste generated in the aluminum electrolysis process.In this study,a flotation-acid leaching process is proposed for the purification of graphitized SCC,and the use of the purified SCC as an anode material for lithium-ion batteries is explored.The flotation and acid leaching processes were separately optimized through one-way experiments.The maximum SCC carbon content(93wt%)was achieved at a 90%proportion of−200-mesh flotation particle size,a slurry concentration of 10wt%,a rotation speed of 1600 r/min,and an inflatable capacity of 0.2 m^(3)/h(referred to as FSCC).In the subsequent acid leaching process,the SCC carbon content reached 99.58wt%at a leaching concentration of 5 mol/L,a leaching time of 100 min,a leaching temperature of 85°C,and an HCl/FSCC volume ratio of 5:1.The purified graphitized SCC(referred to as FSCC-CL)was utilized as an anode material,and it exhibited an initial capacity of 348.2 mAh/g at 0.1 C and a reversible capacity of 347.8 mAh/g after 100 cycles.Moreover,compared with commercial graphite,FSCC-CL exhibited better reversibility and cycle stability.Thus,purified SCC is an important candidate for anode material,and the flotation-acid leaching purification method is suitable for the resourceful recycling of SCC.

Mechanism of lime decomposing Al_(2)O_(3)-containing fayalite melt

A method to upgrade the iron grade in copper slag was proposed using lime to decompose Al_(2)O_(3)-containing fayalite melt(AFMT).Thermodynamic calculations indicated that adjusting the CaO/AFMT ratio can yield a residual melt with a FeO concentration of 75−88 wt.%and produce Ca_(2)SiO_(4).In-situ observations suggested that the reaction was impeded in some way.Quenching experiments revealed that the initial reaction products consisted of calcium ferrite compounds and FeO−CaO melt.At the FeO−CaO melt/AFMT interface,Ca_(2)SiO_(4) particles precipitated,forming a dense Ca_(2)SiO_(4) film that significantly impeded mass transfer.Although trace amounts of Al_(2)O_(3) in AFMT temporarily enhanced mass transfer,they were insufficient to overcome this retardation effect.The decomposition reaction was far from achieving equilibrium,demonstrating a self-retardation effect.Measures must be implemented to eliminate this self-retardation effect and enhance the efficiency of reaction kinetics.

Core-shell mesoporous carbon hollow spheres as Se hosts for advanced Al-Se batteries

Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products.In this work,we aim to harness the advantages of Se while reducing its limitations by preparing a core-shell mesoporous carbon hollow sphere with a titanium nitride(C@TiN)host to load 63.9wt%Se as the positive electrode material for Al-Se batteries.Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN,the obtained core-shell mesoporous carbon hollow spheres coated with Se(Se@C@TiN)display superior utilization of the active material and remarkable cycling stability.As a result,Al-Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g^(-1)at a current density of 1000 mA·g^(-1)while maintaining a discharge specific capacity of 86.0 mAh·g^(-1)over 200 cycles.This improved cycling performance is ascribed to the high electrical conductivity of the core-shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.

Growth and inhibition of zinc anode dendrites in Zn-air batteries:Model and experiment

Zinc(Zn)-air batteries are widely used in secondary battery research owing to their high theoretical energy density,good electrochemical reversibility,stable discharge performance,and low cost of the anode active material Zn.However,the Zn anode also leads to many challenges,including dendrite growth,deformation,and hydrogen precipitation self-corrosion.In this context,Zn dendrite growth has a greater impact on the cycle lives.In this dissertation,a dendrite growth model for a Zn-air battery was established based on electrochemical phase field theory,and the effects of the charging time,anisotropy strength,and electrolyte temperature on the morphology and growth height of Zn dendrites were studied.A series of experiments was designed with different gradient influencing factors in subsequent experiments to verify the theoretical simulations,including elevated electrolyte temperatures,flowing electrolytes,and pulsed charging.The simulation results show that the growth of Zn dendrites is controlled mainly by diffusion and mass transfer processes,whereas the electrolyte temperature,flow rate,and interfacial energy anisotropy intensity are the main factors.The experimental results show that an optimal electrolyte temperature of 343.15 K,an optimal electrolyte flow rate of 40 ml·min^(-1),and an effective pulse charging mode.

Rapid prediction of flow and concentration fields in solid-liquid suspensions of slurry electrolysis tanks

Slurry electrolysis(SE),as a hydrometallurgical process,has the characteristic of a multitank series connection,which leads to various stirring conditions and a complex solid suspension state.The computational fluid dynamics(CFD),which requires high computing resources,and a combination with machine learning was proposed to construct a rapid prediction model for the liquid flow and solid concentration fields in a SE tank.Through scientific selection of calculation samples via orthogonal experiments,a comprehensive dataset covering a wide range of conditions was established while effectively reducing the number of simulations and providing reasonable weights for each factor.Then,a prediction model of the SE tank was constructed using the K-nearest neighbor algorithm.The results show that with the increase in levels of orthogonal experiments,the prediction accuracy of the model improved remarkably.The model established with four factors and nine levels can accurately predict the flow and concentration fields,and the regression coefficients of average velocity and solid concentration were 0.926 and 0.937,respectively.Compared with traditional CFD,the response time of field information prediction in this model was reduced from 75 h to 20 s,which solves the problem of serious lag in CFD applied alone to actual production and meets real-time production control requirements.

Low-temperature graphitization of lignin via Co-assisted electrolysis in molten salt

The ever-growing energy demand and environmental issues have stimulated the development of sustainable energy technologies.Herein,an efficient and environmentally friendly electrochemical transformation technology was proposed to prepare highly graphitized carbon materials from an abundant natural resource-lignin (LG).The preparation process mainly includes pyrolytic carbonization of raw LG material and electrochemical conversion of amorphous carbon precursor.Interestingly,with the assistance of Co catalyst,the graphitization degree of the products was significantly improved,in which the mechanism was the removal of heteroatoms in LG and the rearrangement of carbon atoms into graphite lattice.Furthermore,tunable microstructures (nanoflakes) under catalytic effects could also be observed by controlling the electrolytic parameters.Compared with the products CN1 (without catalyst) and CN5 (with 10%catalyst),the specific surface area are 158.957 and 202.246 m^(2)g^(-1),respectively.When used as the electrode material for lithium-ion batteries,CN5 delivered a competitive specific capacity of~350 m Ah g^(-1)(0.5 C) compared with commercial graphite.The strategy proposed in this work provides an effective way to extract value-added graphite materials from lignin and can be extended to the graphitization conversion of any other amorphous carbon precursor materials.

Fundamental Understanding on Selenium Electrochemistry:From Electrolytic Cell to Advanced Energy Storage

Selenium(Se),as an important quasi-metal element,has attracted much attention in the fields of thin-film solar cells,electrocatalysts and energy storage applications,due to its unique physical and chemical properties.However,the electrochemical behavior of Se in different systems from electrolytic cell to battery are complex and not fully understood.In this article,we focus on the electrochemical processes of Se in aqueous solutions,molten salts and ionic liquid electrolytes,as well as the application of Se-containing materials in energy storage.Initially,the electrochemical behaviors of Se-containing species in different systems are comprehensively summarized to understand the complexity of the kinetic processes and guide the Se electrodeposition.Then,the relationship between the deposition conditions and resulting structure and morphology of electrodeposited Se is discussed,so as to regulate the morphology and composition of the products.Finally,the advanced energy storage applications of Se in thin-film solar cells and secondary batteries are reviewed,and the electrochemical reaction processes of Se are systematically comprehended in monovalent and multivalent metal-ion batteries.Based on understanding the fundamental electrochemistry mechanism,the future development directions of Se-containing materials are considered in view of the in-depth review of reaction kinetics and energy storage applications.

Effect of carbon species on the reduction and melting behavior of boron-bearing iron concentrate/carbon composite pellets

Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boron- bearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon composite pellet. This is a novel flow sheet for the comprehensive utilization of boron-bearing iron concentrate to produce a new kind of man-made boron ore. The effect of reducing agent species （i.e., carbon species） on the reduction and melting process of the composite pellet was investigated at a laboratory scale in the present work. The results show that, the reduction rate of the composite pellet increases from bituminite, anthracite, to coke at temperatures ranging from 950 to 1300~C. Reduction temperature has an important effect on the microstructure of reduced pellets. Carbon species also affects the behavior of reduced metallic iron particles. The anthracite-bearing composite pellet melts faster than the bituminite- bearing composite pellet, and the coke-bearing composite pellet cannot melt due to the high fusion point of coke ash. With anthracite as the reducing agent, the recovery rates of iron and boron are 96.5% and 95.7%, respectively. This work can help us get a further understanding of the new process mechanism.

Preparation and visible-light photocatalytic property of nanostructured Fe-doped TiO_2 from titanium containing electric furnace molten slag

Nanostructured Fe-doped titanium dioxide was synthesized from titanium containing electric furnace molten slag （TCEFMS） by using an alkali fusion, followed by a hydrolyzation-acidolysis-cMcination route. The effects of Mkali/slag mass ratio, calcinating temperature, calcinating time, and water/slag mass ratio on the extraction efficiency and purity of products were systematically studied in this paper. It is indicated that the best extraction efficiency of nanostructured Fe- doped titanium dioxide is 99.35%, when the molten slag is calcinated at 700℃ for 1 h with the mass ratio of alkali/molten slag of 1.5：1. The influence of alkali/slag mass ratio on the photocatalytic activity of final products was evaluated by the photodegradation of methyl blue under visible light irradiation. A maximum photodegradation efficiency of 88.12% over 30 min was achieved under the optimum conditions.