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Dy-Cu master alloy was prepared by molten salt electrolysis using LiF-DyF3 as basic molten electrolyte and Dy2O3 and Cu2O as raw materials.The morphology and phase composition of the electrolytic products were analyzed by scanning electron microscope(SEM),energy dispersive spectrometer(EDS) and X-ray diffractometer(XRD).The electrolysis reduction process of Dy(Ⅲ) and Cu(Ⅰ) in tungsten cathode was investigated by cyclic voltammetry.The results show that Dy-Cu master alloy with the main phase of CuDy can be prepared in LiF-DyF3(24 mol%)-3%Dy2O3-1%Cu2O system at 970 ℃ for 1.0 h.When the electrolysis process is stable,cell voltage changes little with the same cathode current density.However,with the increase of cathode current density,the cell voltage gradually increases,and the current efficiency firstly increases and then decreases.In LiF-DyF3(24 mol%) molten salt system,the electrolysis reduction process of Dy2O3 and Cu2O is completed in one step.The reduction potential of Dy(Ⅲ) on tungsten electrode is about-0.6^-0.4 V,and that of Cu(Ⅰ) on tungsten electrode is about-0.6 V.

In order to effectively recover Ge from germanium dust,the germanium dust was treated by se-condary enrichment at high temperature-hydrochloric acid leaching distillation.The interaction between SiO2 and GeO2 and the effect of SiO2 on extraction of Ge by hydrochloric acid leaching distillation were studied.Different proportions of SiO2 and GeO2 were treated at different temperatures for 6 h.The phases after treatment and their effects on hydrochloric acid leaching distillation were analyzed.The results show that with the increase of treatment temperature,the content of GeO2 in SiO2 continuously increases.When the treatment temperature is higher than 1 140 ℃,GeO2 can be completely dissolved in SiO2,and the recovery rate of Ge by hydrochloric acid leaching distillation is only about 11.3%.After adding CaO to SiO2-GeO2 system,GeO2 and CaO can form CaGeO3,which greatly reduces the amount of GeO2 dissolved in SiO2,and improves the recovery rate of Ge by hydrochloric acid leaching distillation.After adding CaO with the same molar ratio as GeO2 at 1 140 ℃,the recovery rate of Ge by hydrochloric acid leaching distillation increases from 11.25% to 87.24%.

For the electric furnace smelting of tin-containing intermediate materials,a new process is designed that combines the four process steps of drying,granulation,coarse dust collection of flue gas,and waste heat utilization.By comparing and analyzing the new process with the conventional process,it is concluded that the new process has more advantages than the conventional process in terms of equipment investment,construction site,environmental protection and energy saving.

Using coarse and fine tungsten powder and copper wire as raw materials,tungsten skeletons were prepared by powder metallurgy,and then copper infiltrated tungsten composites with low copper content(mass fraction lower than 10%) were produced by copper liquid infiltration.The density and microstructure of the composites were analyzed by electronic balance,metallographic microscope and scanning electron microscope,and the densification mechanism of the composites in the infiltration process was discussed.The results show that both capillary force and grain boundary diffusion are the driving force in the infiltration process of tungsten infiltrated copper composites,and the infiltration path can be explained by root system model.Adding inducible metals such as Ni to the tungsten skeleton can strengthen the infiltration process.To prepare dense copper infiltrated tungsten composites with low copper content,tungsten skeletons with high density and interconnected grain boundaries or pores are required.

Ni60-WC composite coatings were prepared on Cr12 MoV steel surface by sintering cladding of Ni60-WC alloy powder.The phase composition,microstructure,interfacial structure and cross-sectional hardness distribution of Ni60-WC composite coatings were analyzed by metallographic microscope,X-ray diffractometer and Rockwell hardness tester.The effects of sintering temperature,insulation time and heat treatment process on microstructure and properties of the composite coatings were studied.The results show that Ni60-WC composite coatings mainly consist of γ-Ni-based solid solution and hard phases such as WC,W2C,B6Fe23,BNi3 and FeNi.When sintering temperature is 1 050 ℃ and insulation time is 30 min,the composite coating is compact with few pores and good metallurgical bond at the interface.Heat treatment promotes the diffusion of alloying elements between the coating and the substrate.The hardness of the substrate and the coating is effectively improved also by heat treatment,and the hardness value of the coating is increased from 59 HRC to 65 HRC.

TiC and NbC were prepared by vacuum carbothermal reduction of TiO2 and Nb2O5 ball-milled mixture.The effects of molar ratio of TiO2,Nb2O5 and activated carbon,milling time,reduction temperature and reduction time on the preparation of NbC and TiC were studied by orthogonal experiments.The particle size,phase and micro morphology of the mixture and reduction products were analyzed by laser particle size analyzer,X-ray diffractometer(XRD) and scanning electron microscope(SEM).The results show that the order of the influence of the factors on reduction rate is as follows:reduction temperature > milling time of mixture > molar ratio of Nb2O5∶TiO2∶C > reduction time.The optimized experimental conditions are Nb2O5 ∶TiO2 ∶C molar ratio of 1∶3∶20,milling time of 10 h,reduction temperature of 1 600 ℃,and reduction time of 2 h.Under these conditions,the reduction rate of Nb2O5 and TiO2 mixture reaches 93.90%.Vacuum carbothermal reduction of Nb2O5 and TiO2 mixture requires lower temperature than that of Nb2O5 alone,and pure TiC and NbC can be obtained without secondary reduction.In addition,with the increase of the content of TiO2 and activated carbon,the particle size of the reduction product is finer and can reach the nanometer level.

Using cerium nitrate as raw material,nano-CeO2 powder was prepared with supercritical water oxidation method under different conditions of cerium nitrate concentration,pH,filling degree and reaction time.The crystal structure and morphology of the prepared samples were characterized by XRD and FE-SEM,and their particle size,specific surface area and Zeta potential in sol were also analyzed.The results show that as the concentration of Ce(NO3)3·6 H2O aqueous solution decreases,the particle size of the prepared nano-CeO2 powder decreases,and its morphology is approximately spherical with agglomeration.As solution pH decreases,the particle morphology changes from approximately spherical to fibrous rod-shaped and then to a cubic structure.The fibrous rod-shaped nano-CeO2 particles have a larger specific surface area of 83.4 m^2/g.When the concentration is 0.1 mol/L and the solution pH is 2,CeO2 sol has the highest Zeta potential and good stability to prevent aggregation.

The phase composition,phase transformation and microstructure of Pr-Fe-B alloy prepared by arc melting were characterized by X-ray diffractometer,differential scanning calorimeter and electron probe microanalyzer.The results show that the main phases in the as-cast microstructure of Pr5Fe75B20 alloy are Pr2Fe14B,Pr1.1Fe4B4,Fe2B and fcc-Fe,while those of Pr18Fe75B7 alloy are Pr2Fe14B,Pr1.1Fe4B4,α-Fe,dhcp-Pr and Pr2Fe17.With the increase of boron content in the alloy,the content of dhcp-Pr phase significantly decreases.The non-equilibrium solidification of Pr-Fe-B ternary alloy was simulated using calculation of phase diagram with Scheil module of Thermo-Calc software.The calculated results are in good agreement with the experimental results,which provides basic data for the composition and microstructure design of Nd-Pr-Fe-B permanent magnetic alloy.