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.

This article reviews the research progress on the application of rare metal elements in cemented carbides at home and abroad.The effects of four types of elements,including rare refractory metals,rare earths,rare and precious metals,and rare-scattered metals,on the microstructure and properties of cemented carbides are analyzed,and the application prospects of rare metal elements in cemented carbides is also suggested.

To explore an efficient strengthening treatment technology for cemented carbide,the effects of electric field treatment on the microstructure and performance of YG8 cemented carbide were studied.TEM and SEM were used to analyze the microstructure of YG8 cemented carbide samples and their cutting tools before and after electric field treatment,with their mechanical performance being tested by a Vickers hardness tester and cutting experiments being conducted using a CNC lathe.The results show that after the electric field treatment,the fracture toughness of the YG8 cemented carbide samples increases,the cutting performance of the tools is improved,and the surface quality of the workpiece processed with the electric field treated tools is also significantly improved.Under the action of pulse current,the material undergoes electroplastic effect which provides a driving force for dislocation movement,making dislocation more prone to proliferation and slip,increasing dislocation density,and beneficially improving the performance of the material.When the pulse current is 15 A/mm²,the fracture toughness reaches a maximum value of 9.41 MPa·m^1/2,which is nearly 10%higher than the fracture toughness without electric field treatment.The YG8 cemented carbide tools treated with the electric field reduces the cutting temperature during the cutting process,effectively preventing the formation of chip deposits,improving the friction state during the cutting process,ensuring cutting quality,and significantly improving the surface quality of the processed workpiece.

Compared with the Li₃V₂(PO₄)₃/C(LVP/C-S)prepared by sol-gel method,the Li₃V₂(PO₄)₃/C(LVP/C-R)composite cathode material prepared by hydrothermal ultrasonic-assisted rheological phase method combined with solution deposition method has better electrochemical performance.The synthesized materials were characterized by XRD,SEM and Raman spectroscopy.The synthesized materials were used as cathodes of lithium-ion batteries to assemble half-cells for rate and cycling performance tests,while the electrode reaction kinetics were analyzed by cyclic voltammetry,electrochemical impedance,and galvanostatic intermittent titration technique.The results show that the Li₃V₂(PO₄)₃(LVP-R)synthesized by hydrothermal ultrasonic-assisted rheological phase method is coated with a carbon layer by solution deposition,leading to an increase in the crystal plane spacing,a smaller particle size,an increase in the electrical conductivity and tap density,and a significant enhancement in the dispersion.This facilitates the insertion/extraction of Li⁺in the cathode material and shortens the diffusion path of Li⁺,resulting in improved rate performance,coulombic efficiency and cycling stability of lithium-ion batteries.As the cathode material of lithium-ion batteries,LVP/C-R exhibits a high initial discharge specific capacity(160.12 mA·h/g)at a current density of 0.1 C,and the discharge capacity retention rate is 89.16%after 200 cycles at a current density of 1 C,which is much higher than that of LVP/C-S.In addition,LVP/C-R has a larger apparent Li⁺-diffusion coefficient and better kinetic performance in lithium-ion batteries compared to LVP/C-S and LVP-R.