Recovery of valuable metals from spent lithium ion batteries by smelting reduction process based on FeO–SiO2–Al2O3 slag system

A novel smelting reduction process based on FeO–SiO₂–Al₂O₃ slag system for spent lithium ion batteries with Al cans was developed, while using copper slag as the only slag former. The feasibility of the process and the mechanism of copper loss in slag were investigated. 98.83% Co, 98.39% Ni and 93.57% Cu were recovered under the optimum conditions of slag former/battery mass ratio of 4.0:1, smelting temperature of 1723 K, and smelting mass ratio of time of 30 min. The FeO–SiO₂–Al₂O₃ slag system for the smelting process is appropriate under the conditions of m(FeO):m(SiO₂)=0.58:1–1.03:1, and 17.19%–21.52% Al₂O₃ content. The obtained alloy was mainly composed of Fe–Co–Cu–Ni solid solution including small amounts of matte. The obtained slag mainly consisted of fayalite and hercynite. Meanwhile, the mechanism of copper loss is the mechanical entrainment from strip-like fayalite particles in the main form of copper sulfide and metallic copper.     

Co-reduction of Copper Smelting Slag and Nickel Laterite to Prepare Fe-Ni-Cu Alloy for Weathering Steel

In this study, a new technique was proposed for the economical and environmentally friendly recovery of valuable metals from copper smelting slag while simultaneously upgrading nickel laterite through a co-reduction followed by wet magnetic separation process. Copper slag with a high FeO content can decrease the liquidus temperature of the SiO₂-Al₂O₃-CaO-MgO system and facilitate formation of liquid phase in a co-reduction process with nickel laterite, which is beneficial for metallic particle growth. As a result, the recovery of Ni, Cu, and Fe was notably increased. A crude Fe-Ni-Cu alloy with 2.5% Ni, 1.1% Cu, and 87.9% Fe was produced, which can replace part of scrap steel, electrolytic copper, and nickel as the burden in the production of weathering steel by an electric arc furnace. The study further found that an appropriate proportion of copper slag and nickel laterite in the mixture is essential to enhance the reduction, acquire appropriate amounts of the liquid phase, and improve the growth of the metallic alloy grains. As a result, the liberation of alloy particles in the grinding process was effectively promoted and the metal recovery was increased significantly in the subsequent magnetic separation process.     

Effect of Ti (Macro-) Alloying on the High-Temperature Oxidation Behavior of Ternary Mo–Si–B Alloys at 820–1,300 °C

The aim of the present investigation was to gain an initial understanding of the effect of (macro-) alloying with Ti on the oxidation behavior of Mo–Si–B alloys in the ternary phase region of Mo_ss–Mo₃Si–Mo₅SiB₂ at 820–1,300 °C. Motivated by recent studies and thermodynamic calculations, the alloy compositions Mo–9Si–8B–29Ti (at.%) and Mo–12.5Si–8.5B–27.5Ti (at.%) were selected and synthesized by arc-melting. Compared to the reference alloy Mo–9Si–8B, superior initial oxidation rates at 1,100–1,300 °C as well as a significant density reduction by nearly 18 % were observed. Due to enhanced initial evaporation of MoO₃ and mainly inward diffusion of oxygen, a borosilicate-rutile duplex scale with a continuous TiO₂ phase had formed. Detailed investigations of the oxidation mechanism by SEM, EDX, XRD and confocal micro-Raman spectroscopy indicated that Ti alloying is promising with regard to further improvement of the oxidation resistance as well as the strength-to-weight ratio of Mo–Si–B alloys.     

Corrosion resistance of MgO–C refractory to smelting reduction slag containing titania

Abstract

Interactions between smelting reduction slags containing titania (0·2-20 wt-%TiO₂) and MgO-C refractories have been investigated by stationary immersion and rotary immersion at temperatures of 1773-1923 K. The relationship between the concentration of TiO₂ in the slag and the corrosion rate of the refractories, the effects of slag basicity (CaO/SiO₂), and the effect of the temperature of the molten bath on the corrosion rate were examined. Increasing the TiO₂ concentration in the slag caused an increase in the corrosion rate of the MgO-C refractories. The corrosion rate also increased when the temperature was increased. Increasing the basicity of the acid slag decreased the corrosion rate, but this effect was not evident when the basicity of slag exceeded 1·0. The corrosion mechanism of MgO-C refractories in smelting reduction melts containing titania involves the oxidation of graphitic carbon by TiO₂ and the formation of a deterioration layer containing Ti and TiC, together with the reaction of matrix MgO with slag to form MgAl₂O₄, MgCaSiO₄, and MgSiO₃.     

Carbothermic Reduction of Nickeliferous Laterite Ores for Nickel Pig Iron Production in China: A Review

Both the consumption and production of crude stainless steel in China rank first in the world. In 2011, the nickel production in China amounted to 446 kilotons, with the proportion of electrolytic nickel and nickel pig iron (NPI) registering 41.5% and 56.5%, respectively. NPI is a low-cost feedstock for stainless steel production when used as a substitute for electrolytic nickel. The existing commercial NPI production processes such as blast furnace smelting, rotary kiln-electric furnace smelting, and Krupp-Renn (Nipon Yakin Oheyama) processes are discussed. As low-temperature (below 1300°C) reduction of nickeliferous laterite ores followed by magnetic separation could provide an alternative avenue without smelting at high temperature (~1500°C) for producing ferronickel with low cost, the fundamentals and recent developments of the low-temperature reduction of nickeliferous laterite ores are reviewed.     

Synthesis of nanocrystalline molybdenum powder by hydrogen reduction of industrial grade MoO3

In the present work, ultrafine metal Mo powder with a high purity was successfully prepared by one step direct reduction of MoO₃ vapor with H₂ at 1323 K. MoO₃ vapor was generated by the evaporation of industrial grade MoO₃, which is much cheaper than pure MoO₃. It is found that increasing H₂ concentration is beneficial for the reduction of MoO₃ to metal Mo, as well as for the decrease of particle size of Mo particles. The results obtained at a low H₂ concentration show that the mixture of hexagonal platelet-shaped MoO₂ single crystalline and Mo polycrystalline can be obtained. The present method provides a simple approach to prepare nanocrystalline Mo powder.     

Preparation of ultrafine/nano Mo particles via NaCl-assisted hydrogen reduction of different-sized MoO2 powders

The current study investigated the effects of the amount of NaCl addition, particle size of MoO₂, temperature (under isothermal condition) and heating rate (under non-isothermal condition) on the morphology, particle size and dispersivity of prepared Mo by hydrogen reduction of MoO₂. The formation of sufficient dispersed Mo nuclei and their controllable growth were crucial for transforming the large MoO₂ particles to dispersed ultrafine/nano Mo particles. It was found that in the absence of NaCl, it was hard to control the nucleation and growth of Mo grains, and the morphology and particle size of products still retain those of the raw MoO₂ in the temperature range of 840–1000 °C. However, as the amount of NaCl addition was above 0.05%, it was successful to control the nucleation and growth of Mo. Ultrafine/nano Mo powders with the average particle size from 100 nm to 800 nm were successfully prepared via adjusting the particle size of MoO₂ and temperature under isothermal condition. The use of MoO₂ with small particle sizes can increase the reaction rate and the number of Mo nuclei number, thus improve the particle dispersivity and decrease the particle size. Additionally, after reaction at 900 °C and 1000 °C, the residual Na was reduced to 140 ppm and 33 ppm from the initial value of 380 ppm, respectively. Under non-isothermal condition, the temperatures for the nucleation and growth could be adjusted by changing heating rate and particle size of raw MoO₂ particles. Mo nanoparticles with smaller particle size and better dispersivity were successfully prepared, and the average particle size can decrease to about 80 nm.     

Effects of R2CO3 (R = Li,Na and K) on the reduction of MoO2 to Mo by hydrogen

In the present work, the influence of different factors (additives and temperatures) on the morphologies and sizes of as-prepared metal Mo powders by the hydrogen reduction of MoO₂ in the temperature range of 1053 K to 1353 K are investigated. When pure MoO₂ powders are reduced, the morphologies and sizes of as-prepared metal Mo powders are nearly kept the same as the raw materials. However, it is found that adding a small amount of additives (Li₂CO₃, Na₂CO₃ and K₂CO₃) into MoO₂ has a great influence on that of prepared metal Mo powders. The particles become uniformed, ultrafine and spherical powders. In addition, the particles size of the as-prepared metal Mo powders will become larger as the increase of reaction temperature due to the grains growth. This work provides a new method for the preparation of uniformed, ultrafine and spherical metal Mo powders.     

Oxidation mechanisms in Mo-reinforced Mo5SiB2(T2)–Mo3Si alloys

Results of a systematic investigation of the oxidation in a Mo–Si–B alloy containing the three phases, Mo, Mo₃Si, and Mo₅SiB₂ (T2) are presented. The relative kinetics of B-containing silica-scale formation, permeation of MoO₃ through the viscous scale, the viscosity of the B-containing SiO₂ scale, volatilization of MoO₃ and B₂O₃ from the silica scale, are identified as key parameters that determine the kinetics of the oxidation of the alloy in the temperature range of 500–1300 °C. The oxidation is worst in the intermediate temperature range, 650–750 °C, where MoO₃ begins to volatilize but B₂O₃ does not, resulting in gaseous MoO₃ bubbling through a low viscosity borosilicate scale. In this temperature range, the scale provides insufficient protection suggesting that attempts to improve the oxidation resistance of this system must focus on this temperature range.     

Thermal behaviors and growth of reduced ferronickel particles in carbon-laterite composites

The thermal behaviors of single laterite ore and graphite-laterite mixtures were investigated by thermogravimetry (TG), derivative thermo-gravimetry (DTG), and differential thermal analysis (DTA). Four mass loss steps maximized at about 78, 272, 583, and 826°C are observed for the laterite ore, representing the vaporization of free water, the dehydroxylation of goethite, the decomposition of serpentines, and the second dehydroxylation of serpentines, respectively. The reduction reactions of the graphite-laterite mixtures start at around 700°C and can be divided into three major temperature regions. Coal-laterite composites with an addition of 10 wt.% CaO were roasted at 1100-1350°C for 30 min, and the reduced samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indi-cate that the reduction reactions proceed more completely at higher temperatures. The growth of the reduced ferronickel particles is greatly influenced by the roasting temperature. Obvious growth of the reduced ferronickel particles appears with the formation of worm-like crystals for the sample reduced at 1250°C, and spheric particles are observed for the sample reduced at 1300°C. When the reduction temperature in-creases to 1350°C, the reduced ferronickel particles agglomerate to ferronickel granules of 3-8 mm in diameter. The main elements in the granules include iron, nickel, chromium, carbon, and sulfur, with the content of nickel and that of iron of 9.08 wt.% and 85.21 wt.%, respec-tively.     

Size-controlled synthesis of nano Mo powders via reduction of commercial MoO3 with carbon black and hydrogen

In the present work, a novel method was proposed to synthesize pure nano Mo powder via temperature programmed pre-reduction of commercial MoO₃ by carbon black, followed by deep deoxidation with hydrogen. It was found that the carbothermal reduction of MoO₃ included three stages: MoO₃ → MoO₂ → MoO₂ + Mo₂C → Mo. It can be concluded that the morphology and size of the obtained Mo particles are mainly determined at the carbothermic reduction stage. The dispersed nucleation and controlled growth are critical issues for controlling the particle sizes of Mo, which could be achieved at the carbothermic reduction stage by using the raw materials of the MoO₃ and carbon black. Whereas, when the MoO₃ was directly reduced by hydrogen or active carbon with a larger particle size, or commercial MoO₂ were reduced with the carbon black, the dispersed nucleation and controlled growth of products can't be achieved. Meanwhile, to reduce the residual carbon content in the final Mo product, in the carbothermic pre-reduction process, the small amount of MoO₂ was kept in the pre-reduced Mo powders, which was removed by hydrogen at the deep deoxidation stage. The content of residual carbon content in the final produced Mo nanopowders can be reduced to about 0.02%. This method has the advantages of simplicity, low cost, and high efficiency. Therefore, it has great potential for the industrial preparation of nano Mo powders in a large-scale.     

Oxidation behaviour of Mo–Si–B–(Al,Ce) ultrafine-eutectic dendrite composites in the temperature range of 500–700 °C

A comparative study has been carried out to investigate the effects of Al and/or Ce additions on microstructure of Mo–Si–B alloys and their isothermal oxidation behaviour at 500 and 700 °C in laboratory air for 24 h. Microstructure of arc melted Mo–Si–B–(Al, Ce) alloys consists of bcc α-Mo dendrites embedded in ultrafine lamellar Mo₃Si and Mo₅SiB₂ eutectic matrix. Isothermal oxidation kinetics of ultrafine structured Mo–Si–B alloy at 500 °C has been found to show hardly any mass change during 24 h exposure. Addition of Al to Mo–Si–B alloy refines the microstructure, decreases the net mass loss at 700 °C by ～43%, whereas Ce does not bring about any significant change. The enhanced oxidation resistance of Mo–Si–B–Al alloy is due to the formation of Al–O rich inter-layer at the alloy/oxide interface along with the formation of a protective and dense Al₂(MoO₄)₃ outer layer, which reduces the sublimation of MoO₃ at 700 °C. Various transient/complex oxides formed on the alloys during their high temperature exposure have been examined to determine the oxidation mechanisms.     

Microstructure and tensile properties of Mo alloy synthetically strengthened by nano-Y2O3 and nano-CeO2简

Nano-Y2 O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid–solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo–0.3Y, Mo–0.3Ce, and Mo–0.15Y–0.15Ce were prepared through reduction, isostatic pressing, sintering, and drawing. Tensile properties, second phase microstructure and fracture surface appearance of wires were analyzed. The better refining effect for Mo alloy powder can be gotten after two kinds of nanoparticle oxide doped into MoO2 than only one doped. Nano-Y2 O3 and nano-CeO2 have different influences on sintering process. For nano-CeO2, the constraining effect of grain growth focuses on the initial sintering stage, nanoY2 O3 plays refining grains roles in the later densification stage. Nano-Y2 O3 is undistorted and keeps intact in the process of drawing; and nano-CeO2 is elongated and broken into parts in the drawing direction. The strengthening effect of nano-Y2 O3 and nano-CeO2 keeps the finer grains and superior tensile properties for Mo–0.15Y–0.15Ce wire.     

Microstructure and Corrosion Resistance of Electrodeposited Ni-Cu-Mo Alloy Coatings

This paper deals with the electrodeposition of Ni-Cu-Mo ternary alloy coatings on low-carbon steel substrate from an aqueous citrate sulfate bath. The structures and microstructure of coatings were characterized by scanning electron microscopy and x-ray diffractometry. The corrosion resistance of coatings was investigated by potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy techniques. The results show that the Ni-Cu-Mo coatings are mainly composed of fcc-Ni phase and a small amount of NiCu phase. Ni-Cu-Mo coatings exhibit a nodular surface morphology, and the roughness of electroplated coating increases with the increasing of Na₂MoO₄·2H₂O in the bath. The corrosion performance of the coatings is significantly affected by the Mo content of the alloy coating and their surface morphology. The coating prepared in bath containing 40 g/L Na₂MoO₄·2H₂O has the highest corrosion resistance in 3.5 wt.% NaCl solution, while that prepared in bath containing 60 g/L (or more) Na₂MoO₄·2H₂O shows a lower corrosion resistance due to the presence of microcracks on the coating surface.     

两种铸造镍基合金的高温氧化行为

利用热重分析法、XRD和SEM (EDS)对比研究了700℃超超临界发电机组用K317和K325铸造合金在900和1000℃大气环境下氧化行为。结果表明,K317的氧化性能要优于K325。在900℃氧化时,2种合金的氧化增重遵循抛物线规律,而在1000℃氧化时,氧化增重均分段遵循抛物线规律。K317的氧化膜分3层,外层是NiO、TiO_2和NiCr_2O_4,中间层是致密的Cr_2O_3,内层是内氧化产物Al_2O_3。而K325的氧化膜分2层,外层是NiO, NiCr_2O_4和Nb_2O_5,内层是致密的Cr_2O_3和嵌入的Nb_2O_5颗粒,没有内氧化现象发生。在1000℃氧化时,K325中的Mo严重被氧化形成挥发性MoO_3;同时氧化膜发生了局部剥落现象,氧化膜的附着性相对较差。     

Synthesis of Mo-Si-B intermetallic compounds with continuous α-Mo matrix by pulverization of ingot and hydrogen reduction of MoO3 powders

The fabrication of the intermetallic phase T2-Mo₃Si with continuous matrix of α-Mo was attempted with the combination process of high energy ball milling, pulverization of arc-melted ingot, addition of Mo by hydrogen reduction of MoO₃ and spark plasma sintering processes. High energy ball milling or arc melting of Mo-16.7Si-16.7B (at %) powders were performed to obtain to intermetallic phase T2 and Mo₃Si. The Mo phase of 57 vol% distributed intermetallic compound powders were prepared by hydrogen reduction of MoO₃ and further mixing of elemental Mo powders. X-ray diffractometry analysis revealed that the intermetallic phase T2-Mo₃Si can be produced by the pulverization process of arc-melted ingot. Hydrogen reduction of 1 vol% MoO₃ mixed intermetallic powder followed by further addition of Mo powders was a more adequate method enabling the homogeneous distribution of the Mo phase than that of added MoO₃ powders with total amount. The powder mixture was successfully consolidated by spark plasma sintering yielding a sound microstructure comprising the intermetallic phase T2-Mo₃Si uniformly distributed in a continuous matrix of α-Mo.     

Effect of ammonium dimolybdate (ADM) on the reduction of molybdenum trioxide

Ammonium dimolybdate ((NH₄)₂Mo₂O₇) or molybdenum trioxide (MoO₃) is used as starting raw materials for manufacturing Mo powders. In the initial step, usually carried out in rotary calciners, (NH₄)₂Mo₂O₇ or MoO₃ is reduced to MoO₂. Agglomeration of powder due to melting of eutectic formed between MoO₃ and Mo₄O₁₁ and due to melting of MoO₃ occurs during this reduction step resulting in several manufacturing issues. The reduction from (NH₄)₂Mo₂O₇ involves an endothermic reaction however, reduction of MoO₃ occurs only by exothermic reaction. It is hypothesized that addition of (NH₄)₂Mo₂O₇ to MoO₃ will decrease agglomeration of powders due to the endothermic reaction involved in the reduction process. The current paper details experiments carried out to verify the hypothesis. MoO₃ containing varying amounts (NH₄)₂Mo₂O₇ were reduced at 550 °C, 650 °C and 750 °C in hydrogen atmosphere. The results show lower agglomeration of powder with addition of (NH₄)₂Mo₂O₇. The thermal analysis results confirm reduction of MoO₃ at lower temperatures with the addition of (NH₄)₂Mo₂O₇.     

Precipitation Behavior of Pt2Mo-Type Superlattices in Hastelloy C-2000 Superalloy with Low Mo/Cr Ratio

This paper focuses on the precipitation behavior of superlattices phases in new Hastelloy C-2000 alloy with low Mo/Cr ratio owing to their detrimental effects on both mechanical and corrosion-resistance properties of the alloys. The precipitation behavior of superlattices phases in the C-2000 alloy was investigated at 600 °C in the aging time range of 100-500 h. The results revealed that Pt₂Mo-type superlattices phases have been precipitated after aging at 600 °C for 100 h. Typically, the Pt₂Mo-type precipitated phases meet to a stoichiometric ratio of Ni₂(Cr, Mo) in this alloy. As increasing aging time from 100 to 500 h, size of the phase increases from around 13 to 55 nm. Besides, morphology of the Ni₂(Cr, Mo) precipitated phases changes from a lean to a fat ellipse with increasing aging time due to the effect of the Mo/Cr atomic ratio and alloying elements on transformation paths from disorder to order. In addition, solution temperature of the Pt₂Mo-type superlattices is around 725 °C determined by differential scanning calorimetry method, which was significantly dependent on the heating rate.     

A Study on Effect of Reactive and Rare Earth Element Additions on the Oxidation Behavior of Mo–Si–B System

Mo–9Si–8B–1Ti, Mo–9Si–8B–1.8Ti, Mo–9Si–8B–0.2La and Mo–9Si–8B–0.4La₂O₃ (at.%) alloys were prepared using mechanical alloying followed by hot isostatic pressing and field assisted sintering. XRD, SEM and EBSD analysis confirmed the formation of Mo solid solution, A15 and T2 phases in the alloys. Isothermal oxidation behavior of the specimens was studied in the temperature range from 750 to 1,300 °C for up to 100 h. Both the Ti and La containing alloys showed superior oxidation behavior compared to unalloyed Mo–Si–B at 900 °C at the initial periods of oxidation. Ti-added alloys suffered higher rate of weight loss at higher temperatures (1,000–1,300 °C) due to the formation of non-protective low viscosity SiO₂-TiO₂-B₂O₃ scale. La-alloyed Mo–Si–B showed superior oxidation resistance at intermediate temperatures (900 °C) as well as at higher temperatures. Enrichment of La at the oxide/alloy interface was found to be the reason for improved oxidation behavior of La-alloyed Mo–Si–B. Amongst the four materials studied, the La₂O₃ containing alloy showed the best oxidation resistance at 900 °C.     

Effects of Withdrawal Rate and Temperature Gradient on the Microstructure Evolution in Directionally Solidified NiAl-36Cr-6Mo Hypereutectic Alloy

The effects of withdrawal rate and temperature gradient on the microstructure and growth interface morphology in directionally solidified Ni-29Al-36Cr-6Mo(at.%) hypereutectic alloy were investigated. Under the temperature gradient of 250 K/cm, well-aligned eutectic microstructure with lamellar morphology was obtained at the withdrawal rate of 6 μm/s. When the withdrawal rate was 10 μm/s, the microstructure changed to Cr(Mo) dendrites + eutectic lamellae. With the increasing withdrawal rate, the interdendritic eutectic growth interface changed from planar to cellular, the number of primary Cr(Mo) dendrites became greater, and the microstructure was refined. When the temperature gradient increased to 600 K/cm, the coupled eutectic growth zone of NiAl-Cr(Mo) alloy was expanded; a well-aligned eutectic microstructure could be obtained at higher rate of 10 μm/s. Furthermore, the planar/cellular transition rate of the interdendritic eutectic growth interface increased. Even at the same withdrawal rate, the number of primary Cr(Mo) dendrites was less and the microstructure was finer under the temperature gradient of 600 K/cm.