In the molten salt electrolysis process of rare earth oxide in fluoride system,the crystallization behavior of the molten salt significantly affects the electrolysis process.The study investigated three molten salt systems,namely NdF₃-LiF-Nd₂O₃,NdF₃-LiF-NdF₂,and NdF₃-LiF-Nd₂O₃-NdF₂(with a fixed mass ratio of NdF₃ to LiF of 85∶15),to measure the crystallization temperature of the molten salt using the cooling viscosity curve and analyze the crystalline phase by XRD.The results show that in the molten salt systems of NdF₃-LiF-Nd₂O₃ and NdF₃-LiF-NdF₂,the crystallization temperature of the molten salt increases with the increase in Nd₂O₃ or NdF₂ content,and the crystalline phases are NdOF and NdF₂,respectively.In the molten salt system of NdF₃-LiF-Nd₂O₃-NdF₂,when the Nd₂O₃ content is in the range of 2%~3%with the NdF₂ content in the range of 1%~3%,the crystallization temperature of the molten salt is in 981~988℃,and NdOF cocrystallizes with NdF₂.To inhibit the crystallization and precipitation of the molten salt during the molten salt electrolysis process of rare earth,effective measures could be taken by appropriately increasing the temperature at the bottom of the electrolysis cell and improving the flowability of the molten salt at the bottom.

The blank roasting process and kinetics of power generation ash from vanadium phosphate ore were studied.The results show that in the ash,vanadium mainly exists in the form of vanadium mica,predominately in the V³⁺.The optimum process parameters for the blank roasting of the ash are as follows:grinding 90%of the ash to a fineness of-0.074 mm before roasting and then roasting the ash at 880~900℃for 16 h,the leaching rate of V₂O_5 reaches approximately 71%.The blank roasting of the ash is controlled by interfacial chemical reaction,with an apparent activation energy of 89.75 kJ/mol and a kinetic equation of 1-(1-x)^1/3=114.47exp[-89750/(RT)]t.

In the process of lithium carbonate production by carbonate precipitation method,about 20%of lithium is lost in lithium precipitation mother liquor.Recovering lithium from the mother liquor can not only solve the problem of wastewater discharge in the lithium carbonate production process,but also improve the overall recovery rate of lithium,which is of great significance to the national strategic energy reserve and industrial production.Among various processes for recovering lithium from the mother liquor,the sodium precipitation method is simple and easy to operate,but it can only produces industrial gradeⅡlithium carbonate products with low value.The precipitation method greatly improves the recovery rate of lithium from the mother liquor,but the use of phosphate and fluoride will introduce a large number of phosphate ions and fluoride ions,which has a significant adverse impact on the environment.The adsorption method has the advantages of a simple process,good lithium selectivity,and high recovery rate,but it faces such problems as limited actual adsorption capacity and significant dissolution loss of adsorbents.The extraction method demonstrates strong selectivity and high extraction rate of lithium,but the traditional extraction systems adopt inorganic acid stripping,which leads to severe equipment corrosion and poor working conditions due to high stripping acidity.Developing lowcost,highly efficient,and environmentally friendly recovery technologies is the inevitable direction for lithium recovery from lithium precipitation mother liquor in the future.

To address the challenge of low current efficiency resulted from the hydrogen evolution at the stainless steel cathode during the electrowinning process of gallium under alkaline conditions,the effects of current density,initial sodium hydroxide concentration,Ga³⁺concentration,and electrowinning temperature on the current efficiency were studied to optimize the gallium electrowinning process conditions.The expe-rimental results show that using gallium-plated stainless steel as the cathode,the optimal process parameters include a temperature of 45℃,current density of 500 A/m²,initial sodium hydroxide concentration of 140 g/L,and initial gallium ion concentration of 150 g/L.The optimal conditions effectively reduce the evolution of hydrogen,with the current efficiency remaining at over 75%and a product purity of 99.995%.

ZnCo₂O₄ nanoneedle arrays were grown on nickel foam by hydrothermal synthesis method,and then CoWO₄ nanosheets were deposited on the surface to prepare a core-shell ZnCo₂O₄@CoWO₄ composite electrode material.The microstructure,phase structure,and electrochemical properties of the electrode material were characterized by SEM,XRD,and electrochemical workstation.The results show that the ZnCo₂O₄@CoWO₄ electrode material exhibits a rod-like microstructure,with CoWO₄ nanosheets tightly wrapping the surface of ZnCo₂O₄ nanoneedles.Meanwhile,the electrochemical properties of ZnCo₂O₄@CoWO₄ electrode material are significantly improved on the basis of the monomer.Additionally,ZnCo₂O₄@CoWO₄ composite electrode material has a high specific capacity and an enhanced charge-discharge cycle perfor-mance,effectively addressing the problems of poor conductivity and cycle stability caused by the volume expansion of momoner ZnCo₂O₄ material.

Different mass fractions of NH₃SO₃-modified rare earth tailings NH₃-SCR denitration catalysts were prepared using ball milling and microwave roasting methods.The denitration activity and SO₂/H₂O tolerance of the catalysts were analyzed by BET,SEM-EDS,XRD,NH₃-TPD and H₂-TPR.The results show that NH₃SO₃ modification significantly improves the denitration activity of the catalysts,and the denitration activity of the 10%NH₃SO₃-modified catalyst could reach about 90%at 300~350℃.The combined action of SO₂/H₂O can further improve the denitration activity of the 10%NH₃SO₃-modified catalyst to 97%,and its promoting effect remains stable and reversible.After the rare earth tailings are modified by NH₃SO₃,the specific surface area,acidic sites,and strength of the catalysts increace.The dispersion of surface active substances of the tailings is improved,and the crystalline structure is weakened.The adsorption capacity and redox ability of the catalysts are improved,thereby enhancing catalytic denitration activity and maintaining excellent SO₂/H₂O tolerance.

Ni-Co alloy coatings have good corrosion resistance and are mostly used for metal corrosion protection.The addition of Ce to the alloy coatings can refine the crystal grains and improve the microstructure densification and corrosion resistance of the alloy coatings.Using marine steel EH40 as the substrate,Ni-Co-Ce alloy coatings were prepared on its surface by composite electrodeposition process.The corrosion resistance of the alloy coatings prepared under different process conditions was tested through tests of potentiodynamic polarization curve and electrochemical impedance spectroscopy in a 3.5%NaCl solution.The surface morphology and phase composition of the coatings were investigated by scanning electron microscope and X-ray diffractometer.The results show that the optimal electrodeposition conditions of the coatings are a cerous sulfate concentration of 0.6 g/L,a current density of 0.04 A/cm²,and an electrodeposition temperature of 50℃.Under these conditions,the prepared coating possesses smooth surface,with the lowest self-corrosion current and self-corrosion potential(absolute value)of 3.6945×10^-6A/cm² and-0.534 V,respectively.In addition,the above coating exhibits the maximum charge transfer impedance of 889.81Ω·cm²,having the best corrosion resistance.

In our country,the large-scale production of rare earth steel has not been achieved mainly due to insufficient understanding of the interaction between rare earth and impurity elements such as O and S in steel.Considering the lack of quantitative analysis of the effect of Ce,O,and S contents on rare earth inclusions in steel,FactSage 7.1 software was used to investigate the interaction between different contents of O,S,and Ce in U71MnG steel,as well as their effects on the precipitation of Ce₂O₂S and Ce₂O₃ inclusions.Thermodynamic calculation results show that in the composition system of U71MnG steel,the precipitation of Ce₂O₃ increases at first and then decreases with the increasing Ce content,and reaches the peak at the ratio of m_O/m_Ceof approximately 1/7.4.The formation of Ce₂O₂S requires the joint action of O,S,and Ce,and the precipitation of Ce₂O₂S reaches the peak at the ratio of m_O+S/m_Ceof approximately 1/3.7.SEM images of steel inclusions and statistical results of the number of inclusion particles show that the number of Ce₂O₃ and Ce₂O₂S inclusions in the test steel with a Ce content of 0.024%is higher than that in the test steel with a Ce content of 0.016%.And the laws of inclusion precipitation in steel are consistent with thermodynamically calculated results.

Sm₂Co_7-xR_x(R=Cu,Zr;x=0,0.1,0.2,0.3,0.4)melt-spun ribbons were prepared by induction melting and melt spinning.The effects of substitution elements,substitution amount,and melt spinning rate on magnetic properties,intergranular interaction and irreversible reversal field of the melt-spun ribbons were studied.The results of the magnetic property test show that Cu and Zr substitution causes strong pinning effect within the melt-spun ribbons,contributing to improving the coercivity of the melt-spun ribbons,and both achieve maximum coercivity at x=0.3.When the substitution amount x of Cu is 0.1,0.2 and 0.4,the remanence and maximum magnetic energy product of the melt-spun ribbons gradually decrease with the melt spinning rate,while they gradually increase at x=0.3.When the Zr substitution amount x is 0.1~0.4,the remanence and maximum magnetic energy product of the melt-spun ribbons increase at first and then decrease with the increase of melt spinning rate.The Henkel curve test results indicate that for both Cu and Zr substitution,δM value reaches its maximum at x=0.3,indicating that the intergranular exchange coupling effect in the melt-spun ribbons reaches its maximum at this point.The ma-ximumδM values of Sm₂(Co,Cu)₇ and Sm₂(Co,Zr)₇ melt-spun ribbons are 1.48 and 1.04,respectively.A moderate substitution amount of Cu and Zr elements can enhance the irreversible reversal field H_n of the Sm₂Co₇ magnet during demagnetization.

To improve the mechanical properties and service temperature of laser additive IN718 alloy components,five improved IN718 laser additive samples with the gradient increase in Ti+Al content were prepared.The mechanical properties at room temperature and high temperature and microstructure of the samples were studied by universal testing machine,SEM,XRD,and JMatpro software.The results indicate that as the Ti+Al content increases,the proportiaon ofγ′phase gradually rises,with an increase in room temperature strength and a significant decrease in elongation.When the content of Ti+Al reaches 7.6%,the proportion ofγ′precipitated phase is 5 times that ofγphase and the hardness is 55.6 HRC.Then the abundant precipitation of brittle phases results in the initiation of cracks.After undergoing 1100℃×1 h+850℃×8 h heat treatment,the high-temperature strength of the samples at 850℃initially increases and then decreases with the increasing Ti+Al content.And when the content of Ti+Al arrives at 5.6%,the high-temperature yield strength and elongation of the samples reach the maximum value of 553 MPa and 12%,respectively,showing consistency in all directions.Meanwhile,the proportions ofγ′precipitated phase andγphase are close(41.5%and 39.9%,respectively).In subsequent research,the Ti+Al content in standard IN718 alloy can be increased to 5.6%,and properly usingγ′strengthening can obtain excellent high-temperature mechanical properties and compatibility of laser additive process.