Vanadium is usually associated with other metals as a rare metal.A large number of impurity ions,such as iron,could exist in the sulfuric acid leaching solution of vanadium-bearing ore,which significantly impacts the subsequent separation and enrichment of vanadium.The study of extraction kinetics is an important method for determining the control steps in the extraction process,and the difficulty in extracting metal ions.A self-designed cylindrical constant interface cell was used to study the kinetics of extracting V(Ⅳ)and Fe(Ⅱ)from sulfuric acid solution with P507 as the extractant.The results show that the aqueous phase serves as the diffusion resistance zone of the extraction process,which is a chemical reaction-controlled type.The extraction rates of V(Ⅳ)and Fe(Ⅱ)both demonstrate an upward trend with the increase of stirring speed and extraction temperature.The apparent activation energy of V(Ⅳ)extraction is 48.68 kJ/mol,and that of Fe(Ⅱ)extraction is 135.11 kJ/mol.P507 is more likely to extract V(Ⅳ)from sulfuric acid solution,presenting the potential to achieve the efficient separation of V(Ⅳ)from Fe(Ⅱ).

W-Cu composites are widely used in various industrial fields due to their excellent comprehensive properties, including high hardness, wear resistance, ablation resistance, electrical and thermal conductivity, and low thermal expansion coefficient.This paper introduces the latest research progress of W-Cu compo-sites and their current applications in electrical contacts, microelectronics, military use, and functionally graded materials.In addtion, the paper emphatically summarizes and analyzes the classification and principles of doping modification for W-Cu composites, as well as the influence of doping modification on material properties.Finally, the potential problems and research directions of W-Cu composites in the future are put forward.

The W-6Ni-4Co-2X alloys(X=Nb,Ta,Hf,Mo and Ti)were prepared by powder metallurgy technology,and the effects of adding Nb,Ta,Hf,Mo,and Ti elements on the microstructure and mechanical properties of W-6Ni-4Co alloy were investigated.The results show that the microstructure of the W-6Ni-4Co-2X alloys mainly includes base phase(W phase)and binder phase,and the type and content of the binder phase are related to the precipitation of dissolved W phase in the binder phase(Ni,Co)during sintering.The W grains of W-6Ni-4Co-2Ta alloy and W-6Ni-4Co-2Hf alloy are in the form of irregular polygon,while the W grains of W-6Ni-4Co-2Nb alloy and W-6Ni-4Co-2Ti alloy are ellipsoidal and dispersedly distributed in the binder phase.The uniform microstructure,finer grains,and good interfacial bonding of the W/binder phase in W-6Ni-4Co-2Ta alloy contribute to its superior hardness,bending strength,and yield strength.In W-6Ni-4Co-2Mo alloy,W grains are arranged in network structure,and the continuous W ske-leton structure,in synergy with the ductile binder phase,reduces the strain hardening of the alloy,contributing to its excellent strain hardening resistance.Therefore,adding suitable transition metal elements to W-6Ni-4Co alloy provides an effective way for improving its mechanical properties.

Fluorite-type oxides exhibit outstanding properties,including high melting point,low thermal conductivity,and sintering resistance,making them one of the most extensively researched and highly promising high-entropy material structural systems.As the pyrochlore structure can be considered as an ordered defective fluorite structure,the paper categorizes it into the fluorite-type series.And high-entropy rare earth fluorite-type oxide structural systems at home and abroad can be divided into four categories:AO₂-type,A₂B₂O₇-type,A₂B₂O₆O′-type,and biphasic RE₂Zr₂O₇-type.The current research status of each structural system is comprehensively reviewed,and a future development of high-entropy rare earth fluorite-type oxides is discussed.

In addressing the issue of easy-agglomeration during the roasting process to prepare nanometer Y₂O₃powder by liquid precipitation method,the influence of roasting conditions on the morphology and particle size of Y₂O₃and kinetic behavior of nanometer basic yttrium carbonate,obtained with the mixed precipitation agents of sodium carbonate and sodium bicarbonate,were systematically studied.The results show that under the conditions of a roasting temperature of 860℃,a heating rate of 5.375℃/min,and a roasting time of 1 h,nanometer Y₂O₃with good dispersion of D₅₀=0.050μm and(D₉₀―D₁₀)/(2D₅₀)=0.98 is obtained,and its morphology is similar to that of precursor basic yttrium carbonate.The thermal decomposition of roasting basic yttrium carbonate precursor(Y(OH)CO₃·H₂O)to prepare nanometer Y₂O₃powder includes two stages.In the first stage,Y(OH)CO₃·H₂O decomposes to generate Y(OH)CO₃,with an apparent activation energy E of 90.23 kJ/mol,a pre-exponential factor A of 7.46××10⁵,and a reaction order n of 0.75.In the second stage,Y(OH)CO₃decomposes to generate Y₂O₃,with an apparent activation energy E of 236.55 kJ/mol,a pre-exponential factor A of 1.31×10¹¹,and a reaction order n of 0.82.

To develop commercially valuable RE-Fe-B magnets with high Ce content and improve the utilization of high abundance rare earth Ce,the magnetic properties and microstructure of RE-Fe-B magnets with different substitution amounts of Ce were investigated.The experimental results show that the dual main phase magnet with a Ce/(Ce+Nd)mass fraction of 40%still maintains excellent magnetic properties,with a remanence B_rreaching 1.31 T,and a maximum energy product(BH)_maxreaching 310.56 kJ/m³.In single and dual main phase magnets with a Ce substitution of 40%,differences appear in the displacement beha-vior of Nd and Ce elements.In single and dual main phase magnets,Nd element tends to enter the main phase grains,while Ce element tends to aggregate in the grain boundary phase or the surface layers of the main phase grains.In addition,the Ce-poor main phase and(Nd_0.6Ce_0.4)_30.5(Fe,M)_balB_0.97main phase close to the nominal component are formed in the dual main phase magnet.The magnetization behavior of single and dual main phase magnets was analyzed by observing magnetic domain switching,and the enhancement mechanism of coercivity in the dual main phase magnets was studied.The high anisotropy field of the Ce-poor main phase imposes the pinning effect on the magnetic moment of the Ce-rich main phase.The study of the diffusion behavior of Nd and Ce elements provides a basis for the preparation of commercial RE-Fe-B magnets with high Ce content and superior magnetic properties.

A low-grade stone coal vanadium ore in Southern Shaanxi was used as raw material to extract vanadium by two-stage countercurrent sulfuric acid leaching under the condition of adding fluorine-containing leaching aid.The results show that under the conditions of a grinding fineness of stone coal vanadium ore of―0.074 mm accounting for 40%,a leaching aid of 1%NaClO₃+3%2^#fluorine-containing leaching aid,a sulfuric acid dosage of 22%,a two-stage countercurrent leaching temperature of 90℃,a leaching time of 1 h for the first stage,and a leaching time of 2 h for the second stage,the leaching rate of vanadium can reach 94.95%.This process can effectively reduce the amount of sulfuric acid,improve the vanadium lea-ching rate,save the agent,and simplify the subsequent vanadium extraction process.

Nano Ti(C,N)-based green cermet was prepared with different pressing pressures to study the microstructure,shrinkage,and mechanical properties of the cermet after low-pressure sintering.The results show that with the extremely low pressing pressure,the powder arrangement is not tight and the microstructure of the cermet is uneven.And with the extremely high pressing pressure,the microstructure of the cermet is layered,and the porosity and defects are increased.When the pressing pressure is 180 MPa,the obtained nano Ti(C,N)-based cermet exhibits the highest density,with a relative density of 97.06%,a shrinkage coefficient of 1.23,and the lowest porosity of A02B00C00.Simultaneously,the cermet presents the best comprehensive mechanical properties,with a Vickers hardness of 1680 HV₃₀,a flexural strength of 1650 MPa,and a fracture toughness of 8.8 MPa·m^1/2.

Porous Ti-5Mn-xCu(x=0,3,5,10)alloys were prepared by powder metallurgy process with va-cuum sintering using 50%ammonium bicarbonate particles as pore-forming agent,and the effects of Cu content on the microstructure and mechanical properties of porous Ti-5Mn alloys were investigated.The results show that the porosity of the prepared porous Ti-Mn-Cu alloys gradually decreases with increasing Cu content.The macropore diameter slightly reduces,and the number of micropores on the walls of the macropores also decreases gradually.The Ti₂Cu phase appears in the porous Ti-Mn-Cu alloys,with its relative amount increasing gradually with the rise in Cu content.The elastic modulus and compressive strength of porous Ti-Mn-Cu alloys increase accordingly with the increase of Cu content.Porous Ti-Mn-Cu alloys containing 3%~10%Cu and 5%Mn exhibit appropriate pore structures and mechanical properties similar to human bone,showing the potential as antibacterial orthopedic implant materials.

Sn-Ag-Cu alloy coating was prepared by using the self-developed Sn-Ag-Cu mesylate electroplating solution on brass substrate.The effects of electroplating process parameters on the composition,surface morphology,and thickness of Sn-Ag-Cu alloy coating were discussed by scanning electron microscope(SEM)and energy dispersive spectroscope(EDS).The results show that under the conditions of a current density of 4 A/dm²,a temperature of 25℃,and a pH of 5.5,the obtained Sn-Ag-Cu alloy coating has fine and dense crystals,smooth and bright surface,and uniform thickness.