The grain structure and phase transformation start temperatures of Zr-0.4Sn-1Nb-0.3Fe,Zr-1.2Sn-1Nb-0.3Fe and Zr-0.4Sn-0.65Nb-0.3Fe zirconium alloy sheets with different Sn and Nb contents were analyzed by optical microscope(OM),scanning electron microscope(SEM)and electron backscatter diffraction(EBSD).The results show that the variation in Sn and Nb contents exhibits negligible impact on the grain size of the zirconium alloy sheets.Nb demonstrates little influence on the recrystallization degree of the alloy,while an increase in Sn content proves conducive to alloy recrystallization.All three alloy sheets exhibit a fine and uniformly distributed recrystallized grain structure,with grain sizes finer than Grade 12.The increase in Sn content can raise the phase transformation start temperature of zirconium alloy,while an increase in Nb content slightly reduces the phase transformation start temperature of the alloy.

N36 zirconium alloy samples before and after equal channel double angular pressing(ECDAP)were annealed at 800℃,and then aged at 580℃for different times(12 h,24 h,48 h).The effects of heat treatment conditions on the microstructure morphology,second phase particles and microhardness of the initial sample and deformed samples were investigated.The results show that large deformation can significantly enhance the recrystallization driving force of annealing process,which is beneficial to the diffusion of alloy elements during subsequent aging process and promotes the dispersed precipitation of second phase particles.As the deformation pass increases,the second phase size of the alloy noticeably refines.With the increase of aging time,the second phase size and the hardness of the alloy increase.When the aging time after annealing increases from 12 h to 48 h,the average size of the second phase in the initial sample increases from 280 nm to 306 nm,and the average size of the second phase in the 4-pass deformed sample increases from 144 nm to 163 nm.The hardness value of the initial sample increases by 7.05%,and the hardness values of the 1-pass and 4-pass deformed samples increase by 11.1%and 11.49%,respectively.It can be seen that the combination of deformation and heat treatment process also greatly improves the mechanical properties of N36 zirconium alloy.

Using ammonium metatungstate as the source of tungsten,cobalt nitrate as the source of cobalt and sucrose as the source of carbon,WC-Co composite powder was successfully synthesized through a twostep method combining liquid phase method and reduction carbonization method,and then WC-Co cemented carbide was prepared by sintering.The influences of different reduction carbonization temperatures on the phase composition,particle morphology,particle size and sintering formability of WC-Co composite powder were studied using XRD,SEM,EDS,FT-IR,microhardness tester and other methods.The micromorphology and particle size of experimentally prepared WC-Co composite powder and cemented carbide were compared and analyzed with commercial WC-Co composite powder and cemented carbide.The results show that the reduction carbonization temperature significantly affects the microstructure of the powder.At 900~1200℃,decarbonized phases such as Co₃W₃C and Co₃W₉C exist in the WC-Co composite powder.At 1300~1400℃,the reaction is complete and only WC and Co phases remain.As the reduction carbonization temperature increases,the particle size of the WC-Co composite powder gradually increases(about 0.21μm at 900℃and 0.97μm at 1400℃).The morphological evolution is as follows:equiaxed→equiaxed,rod-like,and flake-like→equiaxed→locally rod-like.Compared with commercial WC-Co cemented carbides,the cemented carbide prepared by sintering WC-Co composite powder subjected to reduction carbonization at 1300℃exhibits more uniform distribution of W,C,and Co elements,but has relatively low relative density(72.93%)and hardness(5.6 GPa).

Ultrafine near-binderless cemented carbides were fabricated by spark plasma sintering using WC and Co powders with particle size below 500 nm as raw materials,and Cr₃C₂ as a grain growth inhibitor.The effects of binder content,ball milling methods,and sintering processes on the microstructure,relative density and mechanical properties of cemented carbides were investigated using X-ray diffractometer,metallographic microscope,scanning electron microscope,Archimedes'drainage method,and Vickers hardness tester.The results indicate that the cemented carbides prepared with different binder contents and processing routes exhibit consistent phase composition,consisting of a single WC phase.As the binder content decreases,the relative density of the cemented carbides declines with increased porosity,while the hardness increases accordingly.Specifically,when the binder content is≤0.1%(mass fraction),the hardness exhibits a marked enhancement.The cemented carbide(with 0.1%Co addition)prepared by high-energy ball milling for refinement→conventional ball milling for mixing→oscillating pressure-assisted spark plasma sintering exhi-bits no microscopic pores(relative density of 99.5%)and optimal comprehensive mechanical properties(microhardness of 2582 HV₃₀ and fracture toughness of 4.8 MPa·m^1/2).

Li₃V₂(PO₄)₃/C cathode material was prepared by carbothermal reduction method,and then modified via TiO₂ coating using butyl titanate hydrolysis method.The effect of TiO₂ coating amount on the structure and electrochemical properties of Li₃V₂(PO₄)₃/C cathode material was studied.The results show that TiO₂ coating on Li₃V₂(PO₄)₃/C cathode material has no effect on its crystal structure.In the range of TiO₂ coating amount of 0~4%(mass fraction),the surface of the material with TiO₂ coating amount of 2%can form a uniform and dense protective layer,which enhances the structural stability of the material and reduces the polarization degree of the electrode.Compared with other coating conditions,the prepared battery sample has better rate performance and cycling performance.In the voltage range of 3.0~4.3 V,the initial discharge specific capacity of the sample reaches 120.9 mA·h/g at 0.2 C,the discharge specific capacity after 20 cycles is 121.4 mA·h/g,and the capacity retention rate reaches 100.4%.

Metal cation doping can significantly improve the structural stability of Ni-rich ternary material.However,in liquid-phase co-precipitation doping process,metal cations are prone to hydrolysis,which complicates the influences of dopants on material properties.To address this problem,this study took Ni_0.83Co_0.11Mn_0.06(OH)₂ precursor as the research object,and conducted Al doping modification via alkaline liquid-phase co-precipitation using two approaches:with and without citric acid.The effects of Al doping and citric acid addition on the phase composition and micromorphology of precursors were studied.The precursors before and after modification were subjected to lithium blending and sintering to prepare Ni-rich ternary materials,and the electrochemical performance of their positive electrodes was investigated.The results show that doping Al without citric acid easily results in the formation of aggregates between Al³⁺and ions in the alkaline solution,forming a coating layer on the surface of Ni_0.83Co_0.11Mn_0.06(OH)₂ particles and preventing Al³⁺from entering the interior of the particles.After adding citric acid as a chelating agent with a molar ratio of 0.25∶1 to Al³⁺,the prepared Ni-rich ternary cathode material has a sphericity that is basically consistent with the precursor,and the secondary spherical particles are composed of fine primary particles.Under the conditions of 1 C current density,2.8~4.3 V voltage,and 25℃temperature,after 100 cycles,the capacity retention rate of the Al-doped Ni-rich ternary cathode material with 25%citric acid added increases from 67.9%(without citric acid)to 83.3%,exceeding the 71.6%of the unmodified material.When the Ni-rich ternary precursor is doped with metal cations in the alkaline liquid phase,an appropriate amount of citric acid is beneficial for the incorporation of metal cations into the particles,thereby improving the electrochemical performance of the Ni-rich ternary cathode material.However,excessive citric acid can cause the particles to grow too large,leading to a decrease in electrochemical performance.

Ni₃S₂@NiMo-LDH composite electrocatalytic material was prepared on a nickel foam substrate through hydrothermal method.The phase composition,microstructure,and electrocatalytic properties of the prepared electrocatalytic material were characterized using X-ray diffractometer(XRD),scanning electron microscope(SEM),and electrochemical workstation.The experimental exresults demonstrate that Ni-Mo-LDH nanospheres are successfully grown on the Ni₃S₂ nanosheet substrate,obtaining Ni₃S₂@NiMo-LDH composite electrocatalytic material.The Ni₃S₂@NiMo-LDH composite electrocatalytic material exhibits an overpotential of 84.7 mV for the hydrogen evolution reaction(HER)at a current density of 10 mA/cm²,and an overpotential of 270 mV for the oxygen evolution reaction(OER)at 20 mA/cm².The overall water splitting voltage of Ni₃S₂@NiMo-LDH two-electrode system required at a current density of 150 mA/cm² is 2.19 V.Compared to the individual Ni₃S₂ and NiMo-LDH materials,the Ni₃S₂@NiMo-LDH composite material exhibits superior electrocatalytic properties and excellent stability.

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In view of the current situation of low-purity of ammonium dimolybdate prepared by existing ex-traction processes from industrial molybdenum oxide,the process of extracting and purifying industrial mo-lybdenum oxide alkaline leachate with primary amine N1923 was investigated,and the effects of various ex-traction and stripping conditions on Mo extraction rate,stripping rate,and ammonium dimolybdate purity were explored.The results show that under the optimized single-stage extraction conditions of room tem-perature,pH value adjustment of the alkaline leachate to 4 through sulfuric acid addition,organic phase composition of 40%N1923+20%isoamyl alcohol+40%sulfonated kerosene,O/A ratio of 1∶1,and extraction time of 3 min,the Mo extraction rate exceeds 94%.Under the conditions of 9%ammonia solu-tion as the stripping agent,O/A ratio of 3∶1,three-stage stripping,room temperature,and stripping time of 3 min,the Mo stripping rate reaches 98%.Ammonium dimolybdate product with a purity of up to 99.99%is obtained by evaporating and crystallizing the stripping solution.However,due to its high tung-sten content,further targeted tungsten removal is required in subsequent steps.

In order to solve the problem of small particle size of molybdenum trioxide(MoO₃)products from current vertical furnace production,a controllable preparation method for large-size pure MoO₃ was proposed.Through control of raw material particle size,optimization of roasting parameters in vertical fur-naces,and reduction of mixer operation time,significant improvement in product particle size distribution could be achieved.The experimental results show that the optimized process conditions for pure molybde-num trioxide production are as follows:ammonium dimolybdate(ADM)raw material with FSSS particle size≥38μm,vertical furnace roasting at 490℃with feed rate of 7.5 kg/min for 70 min under furnace pressure of-60~0 Pa,and mixer operation time of 2 min.Over a six-month production period,the ave-rage FSSS particle size of MoO₃ from the optimized process increases from 9.03μm to 16.15μm,with the yield percentage of large particles(10~25μm FSSS size)improving from 35.28%to 85.43%compared with the original process.This optimized process effectively addresses the poor compactibility issues of mo-lybdenum powder caused by the fine particle size MoO₃ products from conventional methods,thereby pro-viding reliable raw material support for downstream deep processing of molybdenum metal.This study provides a quantifiable process control strategy for the industrial-scale production of large-size pure MoO₃ in vertical furnaces.