China Nonferrous Metallurgy

Abstract:So advantageous are TiC-based iron matrix composites in terms of high hardness, strength, good plasticity and toughness, and simple molding that they are widely used in industries such as aerospace, mechanical equipment, and automobiles. In the preparation process of existing TiC-based iron matrix composites, high-purity Ti powder, Fe powder, C powder, B4C powder and other materials are mostly selected for synthesis.In this study, vanadium-titanium iron concentrate and coal powder were used as the main raw materials, and a new type of TiC-based iron matrix composite was prepared by carbothermal reduction-acid leaching process. The effects of carbothermal reduction and acid leaching process parameters on the preparation of TiC-based iron matrix composites were investigated by single factor experiments.The results illustrate that temperature exerts a remarkable influence on the phase composition of the products. With the increase in temperature, Fe gradually changes from existing in the form of Fe_0.9Si_0.1 to Fe₃Si. Under the conditions of a ball-to-material ratio of 4∶1, a reduction temperature of 1550℃, and a reduction time of 30 minutes, the main components of the phase composition are Fe₃Si, Ti(C,N), excessive C, and MgAl₂O₄. By employing a 10% hydrochloric acid (HCl) solution, maintaining a solid-to-liquid ratio of 20∶1, setting the leaching temperature at 85℃, and conducting the leaching process for 120 minutes, the acid-leaching operation effectively removed the extraneous impurities. As a result, the TiC/Fe composite material was successfully fabricated.The morphology and particle size showed little change before and after acid leaching. The particle size was 22μm before acid leaching and 23μm after acid leaching. It should be noted that the reinforcing phase TiC in the prepared TiC/Fe composite material is impure and predominantly exists in the form of Ti(C,N). However, this problem can be effectively circumvented by selecting an appropriate raw-material-to-ball ratio, appropriately adjusting the carbothermal reduction time, and maximizing the carbothermal reduction temperature to the greatest extent possible.

Abstract:High temperature titanium alloy ingot was prepared by vacuum induction suspension melting in this paper, and the nominal composition of alloy was Ti-5.8Al-3Sn-8Zr-0.5Mo-0.7Nb-0.25Si. Metallographic microscope, X-ray diffractometer, universal tensile testing machine and thermal simulation testing machine were used to research the evolution of microstructure and mechanical properties of large size titanium alloy ingot from the center to the edge. The experimental results show that the basket structure formed with the wider α-Ti lamella due to the slow cooling rate of the center of the titanium alloy ingot. The lamella width of α-Ti gradually reduced from 6.65μm to 2.99μm as the test location moved from the center to the edge, however, it is worth noting that the width of the α-Ti lamella in the middle position between the center and the edge fluctuated greatly and the distribution was uneven. Tensile properties at room temperature show that the strength from the centerto the edge decreases first and then increases, and the edge position has little difference with the strength of the center because the deterioration effect of defects on mechanical properties weakens the strengthening effect of fine-grained strengthening. The mechanism of high-temperature tensile deformation was mainly controlled by dislocation slip mechanism and diffusion deformation mechanism. At temperatures ranging from 600℃ to 700℃, the higher the temperature, the lower the strength and the better the elongation. The tensile strength of the edge sample was slightly higher than that of the center, and there was a trend of reducing the strength difference as the temperature increases. The hot compression test showed that the limiting compressive strength of the titanium alloy at 950℃ was almost the same for different sampling positions, with the strength of the center position slightly higher than that of the edge position. At 950℃, the deformation mechanism of the material wass completely a high-temperature diffusion-type deformation mechanism.

Abstract:TiAl-based alloys have excellent properties. However, due to the high price of titanium sponge, the preparation cost of TiAl-based alloys is high, which limits the application of TiAl-based alloys. In this paper，TiAl-M (Cr, Fe) alloy was prepared by one-step synthesis using TiO₂, Fe₂O₃, CrO₃ as raw materials and Al as reducing agent by aluminum thermal reduction method. The experimental results show that TiAl-Cr alloy can be separated from the reduced slag with good effect under the conditions of roasting temperature of 1550℃, Al/TiO₂=0.9, slag ratio of CaO∶Al₂O₃∶CaF₂=40%∶40%∶20% and roasting time of 30 min.The Cr element in the alloy can be regulated according to the amount of CrO₃ in the raw material.The alloy yield can reach up to 88%, Ti yield up to 92.4% and Cr yield up to 99.5%. The main phases of TiAl-Cr alloy are Ti₃Al and Al₈Cr₅. TiAl-Fe alloy is brittle, and the main phases of TiAl-Fe alloy are Ti₃Al and Al₆Fe.

Abstract:Based on the composition and phase characteristics of typical NdFeB magnets, this paper elaborates on the current development status of NdFeB waste recycling processes domestically and internationally. Among these, direct recycling processes demonstrate low energy consumption and environmental friendliness, but they are only applicable to NdFeB magnet waste with relatively intact structures. Hydrometallurgical processes can effectively extract elements such as rare earths and iron from NdFeB magnet waste, yet they involve relatively complex procedures, high acid consumption, and generate secondary acidic and alkaline waste. Pyrometallurgical recycling offers shorter process flows suitable for large-scale operations but suffers from high energy consumption and relatively low rare earth element recovery rates. Hybrid processes overcome the shortcomings of both hydrometallurgical and pyrometallurgical methods, showing promising application prospects. Future development of NdFeB recycling technologies should focus on addressing existing issues such as resource and environmental pollution while strengthening the establishment of fundamental phase transformation thermodynamics databases and microscopic migration kinetics models for valuable metals. Concurrent efforts should prioritize the high-value recycling of non-rare earth metals, driving the NdFeB recycling industry toward greener, lower-cost, shorter-process, and higher-yield development directions.

Abstract:In nature, lithium-bearing clay minerals primarily include lepidolite (polylithionite and trilithionite), zinnwaldite, hectorite, saponite, and others. This article reviews the structure and properties of lithium-bearing clay minerals and compares treatment processes such as acidification and alkalization. Studies indicate that most lithium-bearing clay minerals have a 2∶1 layered structure, where a layer of aluminum-oxygen octahedra is sandwiched between two layers of silicon-oxygen tetrahedra. This structure provides space for the intercalation of lithium ions. Lithium ions can be fixed in the interlayer positions of the mineral crystals through mineralization or isomorphous substitution, thereby achieving lithium enrichment. Currently, the treatment processes for lithium-bearing clay minerals mainly include acidification and alkalization methods. Both methods rely on chemical reactions between acids or bases and the lithium in the minerals to dissociate lithium ions from the mineral structure, enabling lithium extraction. However, these methods also face several challenges that need to be addressed. In terms of reaction mechanisms, the current understanding of the microscopic processes of acid-mineral interactions is not yet thorough, which limits the potential for further process optimization. In process optimization, improving lithium extraction rates, reducing acid consumption, and shortening reaction times are key areas of research. In equipment design, existing setups may not fully meet the specific requirements of acidification methods. Additionally, reagent recovery and waste treatment are significant factors restricting the large-scale application of acidification methods. Therefore, efficiently recovering reagents and safely managing waste are critical challenges that need to be addressed in the future.

Abstract:The discharge of waste from the non-ferrous metallurgical industry continues to grow, posing increasingly severe environmental challenges. Traditional physicochemical treatment technologies, while effective, are associated with high costs. Biological agent technology has garnered attention in the field of non-ferrous metallurgical pollution treatment due to its advantages of cleanliness, sustainability, and low cost. It has been applied in soil remediation and wastewater treatment, yet a comprehensive review of its application progress is lacking. Through bibliometric analysis, it is found that research interest in biological agent technology has been climbing annually over the past two decades, especially in East China, Northwest China, and Northeast China. In terms of application, representative strategies include constructing strain-plant symbiotic systems and algae-bacteria symbiotic systems, supplemented by immobilization methods using porous carriers. Mechanistically, it has been clarified that microorganisms primarily adsorb heavy metals through cell wall adsorption, intracellular accumulation, and extracellular precipitation. In the future, in response to the interference of bacterial species, temperature, and pH values on this technology, efforts should be intensified in the research and development of novel biological agents, pilot-scale application testing, optimization of composite agent design strategies, and the development of new carrier materials. Additionally, given the inadequate and incomplete research on application mechanisms, it is advisable to couple metabolomics, transcriptomics, and isotope labeling to delve deeper into gene regulation mechanisms. This article systematically reviews the research hotspot, application status, and microbial mechanisms of biological agent technology in the treatment of non-ferrous metallurgical pollution, providing a theoretical reference for the improvement and practical application of this technology.

Abstract:The carbon thermal reduction-leaching method was proposed to extract valuable metals from spent lithium-ion batteries, and the change of metal valence, leaching activation energy and leaching rate were systematically investigated. The results showed the best roasting conditions as below, roasting temperature 650℃, roasting time 2.0h and carbon addition amount 10 wt%. And the optimal leaching conditions were 3mol/L H2SO4, leaching temperature 60℃, solid-liquid ratio 100g/L and reaction time 90min. The leaching rates of Li, Ni, Co and Mn were up to 93.10%, 98.91%, 99.34% and 99.26%. The activation energies of Ni, Co and Mn were 40.09kJ/mol, 41.04kJ/mol and 14.30kJ/mol, respectively. Compared with the traditional acid leaching method, carbothermal reduction greatly enhances the leaching rate of Ni, Co and Mn with the reduced leaching activation energy, making it easier to leach valuable metals from waste lithium ion batteries.

Abstract:One of the main reasons for the difficulty in treating complex gold ores is the presence of fine gold particles encapsulated within pyrite, which prevents the gold from being leached out. Traditional cyanidation methods cannot effectively break down pyrite, leading to inefficient utilization of gold resources. To improve the gold leaching rate of complex gold ores, this study conducted pre-oxidation treatment experiments based on the excellent oxidation performance of persulfates and the cavitation effect of ultrasound. The effects of process parameters on the oxidation and leaching of gold ores were investigated, and the pre-oxidation mechanism was analyzed in conjunction with characterization results, leading to the following main conclusions. The optimal conditions for oxidative pretreatment were an ultrasonic power of 480W, a sodium persulfate concentration of 180g/L, a liquid-to-solid ratio of 5∶1, a stirring rate of 600r/min, pH=2, and a pretreatment time of 3 hours. Under these conditions, the gold leaching rate could reach 86.97%. With the activation of ultrasound, persulfates can release a large number of ·OH and SO·-4 radicals, which are key to the effective oxidation of sulfides in complex gold ores. Additionally, the cavitation effect of ultrasound can effectively open up the encapsulation of gold by pyrite, increase the specific surface area of the reactant particles, and change the microstructure of complex gold ores, thereby significantly improving the gold leaching rate. This technology increases the gold leaching rate from 49.12% to 86.97%, with significant effects, and is of great importance for the efficient utilization of complex gold ores in China and the expansion of the application field of ultrasound.

Abstract:Aiming at the current low level of automation in rare earth electrolysis industry, a fuzzy control method of rare earth oxide concentration based on genetic algorithm (GA) optimization is proposed. Combined with the characteristics of rare earth molten salt electrolysis process, the relationship between cell resistance, rare earth oxide concentration and discharging rate is analyzed to determine the corresponding concentration control strategy. The iterative optimization ability of the genetic algorithm is used to realize the dynamic adjustment of the quantization factor and the scale factor of the fuzzy control, so as to obtain a fuzzy controller with better performance. Simulation verification is carried out through Simulink, and the results show that when the scale factor and quantization factor Ke, Kec, Ku are 0.01,0.03 and 7.94 respectively, the system reaches the optimal, the overshoot of the fuzzy controller is 0.1%, and the adjustment time is 16s, which is improved compared with the traditional PID control and fuzzy control. The practical engineering application results show that the fuzzy control method can control the concentration of rare earth oxide in the ideal area, which can meet the working requirements of rare earth molten salt electrolysis on site. Because this method is optimized by genetic algorithm, more computing resources and time are needed in the complex system of rare earth oxide concentration control. In the future, the algorithm should be improved to improve the optimization efficiency and accuracy.

Abstract:The preparation of lithium sulfide composite graphite materials is a hot topic for many scholars, and how to prepare high-capacity lithium sulfide composite graphite structural materials is of more research significance. At present, the method of graphite thermal reduction of lithium sulfate is used to produce this material on an industrial scale. The process requires a high-temperature system and belongs to a solid phase reaction. The reaction rate and particle size are limited by lithium sulfate. In this paper, the idea of preparing lithium sulfide/graphite composite cathode material by using high temperature to immerse lithium into a cheap graphite layer in a vacuum system and sulfurizing in the same system is proposed. The effects of various parameters on the lithium volatilization rate and lithium filling rate of the prepared materials were investigated. The main conclusions are as follows: The optimum leaching process parameters are the leaching temperature of 1173K and the time of 180min. The optimum vulcanization process parameters are the vulcanization temperature of 453K and the time of 40min. The reaction process is in a vacuum system, which not only stabilizes the highly active lithium but also improves the reaction degree of lithium and sulfur. The lithium immersed in graphite is protected and the lithium size is limited to the micron level. The lithium in the prepared lithium sulfide/graphite composite cathode material is basically in the graphite interlayer, and the content of lithium sulfide in the product is 78.88%. The structure of lithium sulfide/graphite composite is more conducive to electron conduction. It is used as a positive electrode for energy storage tests. The barrier is only 3.0V, and the specific capacity is as high as 921.6mAh/g.

Abstract:The close combination of Babbitt alloy and bearings (carbon steel) is crucial for the efficiency of bearing operation, and currently iron-tin compounds are mainly used as intermediate materials to improve bearing life. At present, there is no report in relevant literature on the effect of carbon atom content in carbon steel on the diffusion of tin atoms into iron. A series of experiments concerning hot-tin plating on the surfaces of 25 and 35 steel matrix have been carried in this paper. The key indicators involving Fe-Sn equilibrium time diffusion coefficient of Sn atoms and diffusion thickness have also been analyzed, which could be used to estimate the binding quality during the reaction process at 310℃. The results indicate that the distance from tin atoms diffused into the surface of carbon steel increases with the increasing of holding time, and the diffusion coefficient of tin atoms entering 25 steel is 6.6×10-9, which is about twice that of 35 steel at 310℃. The diffusion distance ratio of carbon atoms is inversely proportional to the square root of the carbon concentration quotient in the surfaces of 25 and 35 steel. In addition, the calculated bonding energy of Fe₃C is -133eV/atom, while the bonding energies of FeSn and Fe₃Sn₂ are only -7.4 and -6.9eV/atom, respectively. It is obvious that carbon atoms are easily combined with iron atoms, that is, the high carbon content would hinder tin atoms to diffuse into the steel. This is the fundamental reason why tin atoms are easily diffused towards the surface of 25 steel. As a result, the matrix material of 25 steel is identified as an ideal babbitt alloy bearing material.

Abstract:In response to the challenges posed by low lithium adsorption capacity, slow adsorption rates, and poor stability of titanium-based lithium ion sieves in practical applications, this study synthesizes a lithium ion sieve utilizing lithium carbonate, titanium dioxide, and lithium acetate as raw materials through an improved high-temperature solid-state method. The synthesized precursor of the lithium ion sieve was characterized with respect to its morphological appearance and crystalline phase composition. Performance tests were conducted using brine sourced from a domestic salt lake as the raw material, focusing on selectivity for impurity ions, cyclic adsorption performance, and the mechanisms underlying titanium leaching. The following key conclusions were drawn: The optimal preparation conditions for the precursor of the lithium ion sieve include a calcination temperature of 699℃, a n_TiO2/n（_Li2O+TiO2） ratio of 0.45, a calcination time of 24h, and an n_CH3COOLi/n（_{Li2CO3+CH3COOLi}） ratio of 0.2:1. Under these conditions, the maximum saturated adsorption capacity for brine reached 27.42mg/g; after multiple cycles of adsorption-desorption tests, the working adsorption capacity was determined to be 8mg/g (in comparison to approximately 6mg/g for commercially available adsorbents with a 30-minute adsorption period), with an Li+ desorption rate around 85%. The selectivity towards impurity ions is relatively favorable with ratios such as Li/Na=4.5, Li/K=25, Li/Mg=13, and Li/Ca=40; thus indicating that separation coefficients rank as α_Li/K＞α_Li/Mg＞α_Li/Na＞α_Li/Ca. Furthermore，the leaching of titanium from the lithium ion sieve is attributed to structural dissolution associated with lithia-titanate formation.