In order to more selectively enrich rare earths in rare earth-containing slags,melting-cooling ex-periments were carried out on the CaO-SiO₂-Al₂O₃-La₂O₃-CeO₂ slag system.The influence law of basicity(CaO/SiO₂ mass ratio)and P₂O₅ content(mass fraction)on the crystallization behavior of the slag system was studied by XRD,SEM-EDS,EPMA and other methods.The results show that when the P₂O₅ content remains constant,as the basicity increases from 0.86 to 1.20,the precipitated phase in the slag system transforms from a single RE-rich phase to a coexistence of two phases:the RE-rich phase and gehlenite phase(Ca2Al2SiO7).However,at a basicity of 1.20,10%P₂O₅ has an inhibitory effect on the precipitation of the Ca2Al2SiO7 phase.In addition,the area fraction and grain size of the RE-rich phase increase with the increase of basicity,and its RE content does not change much.When the basicity remains constant,as the mass fraction of P₂O₅ increases from 0 to 10%,the area fraction and average crystal size of the RE-rich phase increase,but its RE content relatively decreases.Considering the purity of the crystalline phase and the degree of rare earth enrichment comprehensively,adding 5%~10%P₂O₅ at lower alkalinity(R≤1.00)is more conducive to the enrichment and subsequent separation and extraction of rare earths in CaO-SiO₂-Al₂O₃-La₂O₃-CeO₂ slag system.

This paper presented an introduction of ion-adsorption rare earth hydrometallurgy and separation process,analyzed the generation of ammonia nitrogen wastewater and CO₂ in the process,and proposed a resource recovery and utilization scheme for the"internal circulation"of ammonia-carbon resources.For the ammonia nitrogen wastewater,the stripping and distillation method is employed to recover NH₃·H₂O with a mass fraction of 20%.About 80%of this recovered NH₃·H₂O is formulated into 8 mol/L dilute ammonia water,which is reused in the saponification stage of the extraction process.About 20%NH₃·H₂O reacts with CO₂ produced in the calcination process,and is converted into 2 mol/L NH4HCO3 solution through the integrated ammonia capture and carbonation technology,which is then recycled to the precipi-tation process.This approach not only addresses the pollution issue caused by ammonia nitrogen wastewater,but also realizes the"internal circulation"of ammonia-carbon resources.Taking a 10000-ton rare earth hydrometallurgy and separation project designed by the author as an example,and basing on the calculation that 50%of the products are prepared by carbon precipitation process,the capture and absorp-tion of CO₂ in the flue gas generated during the calcination of rare earth carbonate can reduce the direct emissions of CO₂ by about 4830 t/a,which is equivalent to reducing the consumption of standard coal by about 1930 t/a.The production of per ton of rare earth products(calculated by REO)can reduce CO₂ di-rect emissions by an average of about 0.5 t,indicating a remarkable carbon emission reduction effect.

The current status of high-purity manganese sulfate production processes is reviewed.The princi-ples,advantages and disadvantages of different techniques in the major production steps during high-purity manganese sulfate are analyzed and compared.Furthermore,selection principles for critical process parame-ters in each step are established.The critical factors in the leaching process are raw material selection and leachate concentration control.Compared with the roasting-acid leaching method,the two-ore acid addition method reduces energy consumption by over 500 kW·h per ton of manganese sulfate while also lowering auxiliary material usage.The critical factors in the purification process are cost control and solution quali-ty.The fluoride precipitation method can reduce the content of impurities such as Ca,Mg,and F to below 20 g per ton of manganese sulfate.For the crystallization process,energy consumption is the key parame-ter.The high-temperature and high-pressure crystallization method consumes 0.4~0.6 tons of steam per ton of manganese sulfate.Therefore,the currently optimal technical route for high-purity manganese sul-fate production is two-ore acid leaching→fluoride precipitation purification→high-temperature and high-pressure crystallization.This article can provide references for enterprises in selecting suitable production processes and designing manufacturing procedures for high-purity manganese sulfate.

The W-Ni-Cu-Co alloy was prepared by liquid-phase sintering and rotary swaging,and the effects of different tempering temperatures on its microstructure and mechanical properties were investigated.The results show that the W-Ni-Cu-Co alloy mainly consists of W phase andγphase after rotary swaging.Tem-pering treatment at appropriate temperature can effectively eliminate the residual stress caused by rotary swaging,promote atomic diffusion and rearrangement,and result in a more uniform W particle size distri-bution.Additionally,the interfacial bonding strength between W andγphases is higher,and the plastic de-formation capability of W particles is enhanced.The W-Ni-Cu-Co alloy exhibits optimal mechanical proper-ties when tempered at 500℃,with tensile strength,elongation at break,and microhardness of 804 MPa,8.3%,and 445 HV1,respectively.The tensile fracture mode is cleavage fracture of W particles.Excessive tempering temperature leads to the generation and growth of brittle WNi4 phases,deteriorating the me-chanical properties of the alloy.The fracture mode transforms into intergranular brittle fracture due to W-γinterface failure.

The niobium-tungsten alloy bars prepared by steel mold cold pressing were sintered at high tem-peratures of 1700℃,1800℃,1900℃,and 2000℃.The effects of sintering temperature on the micro-structure,properties,and impurity content of the alloy bars were investigated using a infrared oxygen/ni-trogen analyzer,infrared carbon/sulfur analyzer,metallographic microscope,glow discharge mass spec-trometer,Archimedes drainage method,and photoelectric deflection tester.The results indicate that the densification degree,shrinkage rate,and deflection of the alloy bars increase progressively with elevated sintering temperature.The relative density of the alloy bars sintered at 1900℃and 2000℃both exceeds 95%.With the increase of sintering temperature,the elongated fibrous microstructure in the alloy bars gradually diminishes and eventually disappears,while the grains progressively evolve into an equiaxed mor-phology,accompanied by a continuous reduction in impurity content.The alloy bars sintered at 1900℃have oxygen and carbon contents of 0.054%and 0.058%,respectively,demonstrating significant removal of carbon and oxygen impurities.When the sintering temperature reaches 2000℃,over-sintering induces partial melting of grain boundaries,resulting in excessive densification of the alloy bars due to extreme shrinkage rate.This hinders subsequent electron beam melting purification.Additionally,the alloy bars ex-hibit excessive deflection and reduced straightness,making them unsuitable for refining bundle.The opti-mal sintering temperature for niobium-tungsten alloy bars is determined to be 1900℃based on compre-hensive analysis.

A series of CeO₂/TiO₂ catalysts with varying CeO₂ loadings were prepared by impregnation with cerium nitrate solution followed by microwave calcination,using modified TiO₂ as the catalyst carrier.The CeO₂/TiO₂ catalysts were characterized using XRD,SEM,H2-TPR,NH₃-TPD,XPS,and in-situ DRIFTS techniques,and the influence of preparation conditions(including microwave calcination temperature,mi-crowave power,and CeO₂ loading)on the denitration performance of the catalysts was systematically stu-died.The results indicate that the CeO₂/TiO₂ catalyst with 15%CeO₂ loading exhibits the best denitration performance when the microwave calcination temperature is 500℃and the microwave power is 2000 W.Its denitration efficiency remains above 80%at 300~450℃,with a peak denitration efficiency exceeding 90%at 350℃.The 15%CeO₂/TiO₂ catalyst exhibits a loose and porous surface structure,abundant acidic sites,excellent redox capability,and a high proportion of Ce3+and Oα,which contribute to its superior de-nitration activity.During the NH₃-SCR reaction,the 15%CeO₂/TiO₂ catalyst follows both the E-R and L-H mechanisms.

To achieve the comprehensive utilization of metallurgical solid waste titanium-containing blast furnace slag resources,the titanium-containing blast furnace slag(TiO₂ mass fraction<20%)was used as the titanium source,and the Ce-doped titanium-containing blast furnace slag photocatalytic material was prepared by a high-temperature solid-phase doping method.The photocatalyst was characterized by XRD,SEM-EDS and UV-Vis DRS analytical techniques,and the effects of catalyst dosage,UV irradiation time and Rhodamine B(RhB)solution pH value on the photocatalytic performance of Ce-doped titanium-contai-ning blast furnace slag were investigated.The results show that Ce ions are successfully doped into the lat-tice of perovskite(CaTiO₃)and diopside(CaO·MgO·2SiO₂)by the high-temperature solid-phase do-ping method,and both CaTiO₃ and CaO·MgO·2SiO₂ participate in the photocatalytic degradation reac-tion of RhB solution.The addition of Ce ions enhances the light absorption capacity of titanium-containing blast-furnace slag and improves the efficiency of the catalyst in RhB degradation.Under the conditions of a catalyst dosage of 1.00 g,a irradiation time of 2.0 h,and a solution pH of 2,the degradation rate of 100 mL RhB solution with an initial concentration of 10 mg/L reaches 97.2%.

Reducing the use of expensive heavy rare earth elements(such as Dy and Tb)is the key to pro-ducing low-cost,high-performance sintered Nd-Fe-B materials.In this paper,low heavy rare earth alloy Dy₇₀Cu₁₅Ga₁₅ was used as the diffusion source to treat sintered Nd-Fe-B magnet by grain boundary diffu-sion(GBD)technology.The effects of GBD on the properties and microstructure of the magnets were ana-lyzed,and the service performance was characterized.The results show that the coercivity of the sintered Nd-Fe-B magnets significantly increases by 57%after GBD treatment,and the remanence and maximum magnetic energy product slightly decrease.The diffusion of alloying elements into the grain boundary phase optimizes the microstructure of the magnets,and forms a(Nd,Dy)₂Fe₁₄B hard magnetic phase shell on the surface of the matrix grain,mitigating the boundary defects and enhancing the magnetocrystalline anisotro-py field.The magnetic flux loss of the GBD magnet after high temperature treatment is reduced,indicating an improvement in its high temperature stability.Compared with the original magnets,the GBD magnet exhibits better corrosion resistance,with an increase of 18.7% in corrosion potential and a reduction in cor-rosion current density by 54.7% under electrochemical corrosion conditions.

Taking Al-9.6%Sc alloy as the research object,the changes in microstructure,microstructure composition,hardness,grain orientation and grain boundary distribution characteristics of as-cast alumi-num-scandium alloy before and after homogenizing annealing were analyzed using scanning electron micro-scope(SEM),energy dispersive spectrometer(EDS)and electron backscatter diffraction(EBSD).The re-sults show that with the extension of annealing time,the Al₃Sc grains in the aluminum-scandium alloy mi-crostructure undergo recrystallization and grain growth,and the microhardness of the alloy decreases.After homogenizing annealing,the Al₃Sc grains transform from long rod-shaped dendritic structures to sheet-like equiaxed crystals,and the elements in the alloy undergo solid-state diffusion.The maximum deviation be-tween the radial Sc content(mole fraction)of the target blank and the nominal composition decreases from 1.81%to 0.6%,and the average grain size increases by 122.7%from 23.3μm to 51.9μm,with a more uniform grain distribution.Compared with the as-cast alloy,the texture is enhanced,and the proportion of small angle grain boundaries increases.Homogenizing annealing effectively reduces the micro-segregation of the alloy,which is beneficial for obtaining a uniform Al₃Sc structure and a grain orientation distribution that tends to be consistent.

To improve the wear and corrosion resistance of 45 steel(a commonly used material for ship shaft parts)and increase its service life in harsh environments,Ni matrix-TiC composite coatings with dif-ferent CeO₂ contents were successfully prepared on 45 steel substrate using laser cladding technology.The effects of CeO₂ content on the microstructure and properties of the coatings were investigated by SEM,EDS,XRD,microhardness tester,tribometer,and electrochemical workstation.The results show that the rare earth-free coating primarily consists ofγ-(Fe,Ni)solid solution and carbides such as TiC,Fe₃C and Cr₇C₃,whereas the addition of CeO₂ leads to the formation of new phases,including CeNiSi₂ and Ce₂Ni₂₂C₃.The addition of an appropriate amount of CeO₂ contributes to grain refinement and microstruc-ture homogenization of the coating,thereby enhancing its microhardness and wear resistance,while simul-taneously reducing corrosion susceptibility,resulting in superior corrosion resistance of the coating in 3.5% NaCl solution.However,adding excessive CeO₂ induces decomposition of carbides in the coating,resulting in a decrease in its microhardness and wear resistance.Furthermore,the formation of Ce-Ti-O inclusions promotes pitting initiation in the coating,ultimately degrading its corrosion resistance.This study provides a theoretical foundation for rare earth modification of composite coatings for critical ship parts under harsh marine conditions.