Functional graded material(FGM)is a new type of functional composites,of which the macroscopic properties of the material show continuous gradient variation to solve the problem of abrupt changes at the interface between two different materials by controlling the volume content and chemical composition of components in the thickness direction.This paper proposed a method combining powder stacking,pressureless infiltration,and vacuum hot-pressing sintering to prepare iron-lithium niobate FGM with continuously varying component distribution.The method uses layering to control the volume distribution of the material,and by the self weight of high-temperature metals and the voids left by the evaporation of the binder,the liquid metal infiltrates from top to bottom along the void to achieve the effect of eliminating the interlayer interface,and the metal is then densified by vacuum hot-pressing sintering.Finally,a continuous functional graded material with the controlled volume distribution is obtained.The experimental results show that after the pressureless infiltration with a holding time of 120 min at 900℃and the vacuum hot-pressing sintering with a holding time of 120 min at 800℃and 35 MPa,the volume fraction of the prepared iron-lithium niobate FGM is linearly and continuously distributed in the thickness direction.

To study the influence role of deformation temperature on the gradient microstructure and pro-perties of TB8 titanium alloy,gradient extrusion tests were conducted on TB8 titanium alloy at 850℃,900℃and 950℃,and the variation laws of microstructure and microhardness of specimens at different deformation temperatures were investigated by OM and XRD.The experimental results show that after gradient extrusion,the specimen can be divided into three deformation zones,including the core micro-defor-mation zone,the sub-center medium deformation zone,and the edge large deformation zone,showing a gradient distribution of the grain size gradually decreasing from the core to the edge.After the gradient extrusion and deformation,the sub-grain size of the material decreases while its microscopic strain and dislocation density increase significantly;decreasing the deformation temperature can significantly refine the grains and increase the overall hardness value.The hardness of the specimen edge at 850℃increases by 16.32%compared with that of the core.

Yttrium-stabilized zirconia(YSZ)was prepared by hydrothermal hydrolysis using zirconium oxychloride,yttrium chloride,and ammonia as raw materials and polyethylene glycol as a dispersant.The effects of zirconium ion concentration,reaction temperature,yttrium doping amount,dispersant addition,and calcination temperature on the morphology,dispersity,particle size,and crystal form of the zirconia products were systematically studied.The results show that under the conditions of zirconium ion concentration of 0.8 mol/L,reaction temperature of 180℃,yttrium doping amount of 3%(molar fraction),dispersant addition of 2%(mass fraction),and calcination temperature of 1000℃,yttrium-stabilized nano-zirconia powders with good dispersity,uniform particle size distribution and spherical-like shape could be obtained.

Problems in the conventional recycling process of lithium iron phosphate cathode waste include huge resource consumption,tedious steps,and secondary pollution.Using absolute ethanol as the solvent,lithium iron phosphate cathode waste was thermally dissolved to achieve the non-destructive and effective separation of the active substance from the current collector,and the phase structure and electrochemical properties of the regenerated LiFePO_4 cathode material at different calcination temperatures were characterized.The results show that the regenerated LiFePO_4 cathode materials obtained by calcination at diffe-rent temperatures have a pure phase,and the cathode material obtained by pre-calcination at 450°C for 4 h followed by calcination at 650°C for 10 h shows the maximum diffraction intensity.The constant-current charge/discharge test results at room temperature in 2.5~4.3 V voltage range show that the cathode material calcined at 650°C for 10 h exhibits the maximum discharge specific capacity of 137.8 mA·h/g,a capacity retention rate of 92.8%after 100 cycles,and a Coulombic efficiency close to 99%.The electrochemical impedance spectroscopy of this cathode material also exhibits a minimum charge transfer impe-dance of 130Ω.The absolute ethanol thermal dissolution method also provides a new separation way for the recovery of similar materials.

The effects of compound addition of different contents of Cr₃C₂,VC,and TaC as grain growth inhibitors on the microstructure and properties of WC-12%Co ultrafine cemented carbide were studied.The results show that compared with the alloy using Cr₃C₂+VC combined grain growth inhibitor,the comprehensive mechanical properties of the alloy using Cr₃C₂+VC+TaC combined grain growth inhibitor tend to decrease while its thermal conductivity becomes better.The microstructure and mechanical properties of the alloy with Cr₃C₂+VC+TaC combined grain growth inhibitor depend on the inhibitory effect of the grain growth inhibitors rather than the total addition amount,and optimizing the ratio of the three inhibitors is the key to improving the properties of the alloy.

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D3o9 macroporous weakly basic anion exchange resin was used to recover tungsten from the hydrochloric acid leaching solution of scheelite containing arsenotungstic heteropoly acid and transform it into ammonium tungstate solution.The adsorption isotherm,adsorption kinetics,and process conditions of adsorption and desorption of[AsW₁₂O₄₀]^3-by D309 resin were investigated.The results show that the adsorption process of[AsW₁₂O₄₀]^3-by D309 resin fits Langmuir isothermal equation and is monolayer adsorption.The control step of the adsorption process is particle diffusion.Under the optimal conditions of temperature of 55 C,reaction time of 1 h and liquid-solid ratio of 2.5:1,the adsorption rate of tungsten can reach 99.90%.Under the optimal conditions of temperature of 55 C,reaction time of 3 h,ammonia concentration of 210 g/L and liquid-solid ratio of 1.25:1,the desorption rate of tungsten is 91.78%.

The sodium tungstate solution obtained from low-grade scheelite by collaborative leaching with sodium phosphate-sodium hydroxide-calcium fluoride contains a relatively high concentration of fluorine,leading to the fluorine content in the smelting wastewater exceeding the national discharge standard.Based on the low solubility of lanthanum fluoride,lanthanum chloride was added to the sodium tungstate solution and the reaction produced lanthanum fluoride precipitate to thoroughly remove fluorine.The effects of process parameters including the lanthanum chloride dosage,pH value of the solution,reaction temperature,and reaction time on the removal of fluoride were investigated.The results show that the fluorine removal rate reaches 98.8%when fluorine concentration of the sodium tungstate solution is 0.5~2.1 g/L,the dosage of lanthanum chloride is 1.6 times the theoretical amount,the pH value of the solution is 1o.1,the temperature is 60 C,and the reaction time is 30 min,with a tungsten loss of 0.26%in the precipitated slag.After the removal of fluorine,the sodium tungstate solution treated by an ion exchange process can meet the requirement of the national standard for the fluorine content in the discharging wastewater.

Ammonium heptamolybdate was prepared by water dissolving-evaporation concentration removal of ammonia-cooling crystallization method using ammonium dimolybdate as raw material.The effects of concentration degree on crystallization product were investigated,and the effects of concentrated liquid density,cooling rate,crystal growing time,and stirring rate on the particle size and morphology of ammonium heptamolybdate were also studied.The results show that ammonium heptamolybdate crystals with a single phase can be prepared by the evaporation concentration-cooling crystallization method after the water dissolution of ammonium dimolybdate.With a concentrated liquid density of about 1.38 g/cm³,a cooling rate of 30℃/h,a crystal growing time of 1 h,a stirring rate of 150 r/min,and a final cooling temperature of 22℃,the crystals of ammonium heptamolybdate are complete in morphology and prismatic with an average particle size of 337.649μm in a controlled cooling crystallization process.