To solve the problem of poor leaching effeciency in the extraction process of gallium and germanium from zinc powder replacement residues,this study first conducted atmospheric sulfuric acid leaching tests,investigating the influence of sulfuric acid concentration,reaction temperature,liquid-to-solid ratio,and reaction time on the leaching rates of Ga and Ge,and carried out kinetic analysis of the leaching process.Then,the enhanced leaching tests of Ga and Ge from zinc powder replacement residues were conducted by reduction leaching(sequentially using Na₂SO₃ and SO₂ as reducing agents)and sulfation roasting-water leaching.The results show that under the optimum conditions of sulfuric acid concentration of 150 g/L,reaction temperature of 90℃,liquid-to-solid ratio of 5 mL/g,reaction time of 4 h,and stirring speed of 400 r/min,the leaching rates of Ga and Ge by atmospheric sulfuric acid leaching are 68.4%and 61.7%,respectively.The main phases in the acid leaching residue are PbSO₄ and ZnAl₂O₄,and increasing acidity can further dissolve the residual jarosite and lead aluminum sulfate.The atmospheric sulfuric acid leaching processes of Ga and Ge are mainly controlled by internal diffusion with the apparent activation energies of the reactions of 18.06 kJ/mol and 16.02 kJ/mol,respectively.The leaching residue from the first stage of atmospheric sulfuric acid leaching underwent a second-stage reduction enhanced leaching.Using Na₂SO₃ as the reducing agent,Ga and Ge leaching rates reach 89.4%and 70.1%,respectively,under the conditions of 50 g/L H₂SO₄ and 3 g/L Na₂SO₃.And using SO₂ as the reducing agent,Ga and Ge lea-ching rates reach 88.9%and 86.7%,respectively,under the conditions of SO₂ partial pressure of 0.3 MPa,sulfuric acid concentration of 50 g/L,reaction temperature of 110℃,and reaction time of 3 h.The sulfation roasting-water leaching process significantly improves the Ga leaching efficiency from zinc powder replacement residues,while it is unfavorable to the leaching of Ge.Under the optimum conditions of acid residue volume-to-mass ratio of 1/2.5 mg/L,roasting temperature of 300℃,roasting time of 3 h,water leaching temperature of 80℃,liquid-to-solid ratio of 5 mg/L,and leaching time of 2 h,the leaching rate of Ga increases to 89.1%.

Using copper powder and tungsten powder as raw materials,W-Cu alloys were prepared by mechanical alloying and spark plasma sintering.The effects of different sintering temperatures and the additions of Y₂O₃ and Cr additives on the microstructure and physical and mechanical properties of the alloys were analyzed using SEM,XRD,Vickers hardness tester,electron densitometer,and conductivity tester.The experimental results show that as the sintering temperature increases,the distribution of W and Cu phases becomes more uniform,and the density,hardness,and conductivity of the alloys increase.The W-Cu alloy prepared at a sintering temperature of 1100℃exhibits the best comprehensive physical and mechanical properties.With the increase in Y₂O₃ content,the grains of the W-Cu alloys become finer,the hardness increases,while the density and conductivity decrease.In addition,with the increase in Cr content,the conductivity of the W-Cu alloys decreases,but the hardness and density increase slightly and then decrease significantly.The W-Cu-0.5Cr alloy possesses the best comprehensive physical and mechanical properties.Therefore,adding a small amount of additives can effectively improve the microstructure and physical and mechanical properties of the SPS products(W-Cu alloys).

Anhydrous Pr-Nd fluoride powder was prepared by hydrofluoric acid precipitation,and the effects of oxalic acid addition,bottom water acidity,supernatant recycling times and hydrofluoric acid dosage on the formation of hydrated Pr-Nd fluoride crystal and the morphology,particle size,apparent density and impurities of anhydrous Pr-Nd fluoride powder were investigated.The results show that the optimized process conditions are as follows:oxalic acid addition at 6%~10%of the theoretical amount(1.5 times the molar amount of RE³⁺),bottom water acidity of 1.6~2.0 mol/L,supernatant recycling up to 3 times,and hydrofluoric acid dosage at 100%of the theoretical amount(3 times the molar amount of RE³⁺).The anhydrous Pr-Nd fluoride powder prepared under these optimized process conditions has a median particle size D₅₀of 10~30μm and an apparent density of 0.7~0.8 g/cm³.The content of non-rare earth impurities is low,and the yield rate of rare earth reaches 99.81%.

Using the catalyst powder of rare earth tailings activated by sulfuric acid as raw material,a monolithic catalyst was prepared by adding additives and integral extrusion,and then characterized and analyzed by XRD,BET,XPS,and H₂-TPR.In addition,its catalytic denitration reaction activity and N₂ selectivity were tested on a denitration activity test platform to determine the suitable roasting system of the catalyst.The results show that the strip-shaped catalyst roasted at 350℃presents the best catalytic denitration activity and the largest specific surface area.The XPS spectral peak of its Fe2p orbital shifts towards high binding energy,indicating a significant Fe-Ce synergistic effect.At this roasting temperature,a honeycomb-shaped catalyst with a denitration efficiency of 81%and high N₂ selectivity can be prepared,and its mechanical strength meets the national standard for the monolithic catalysts.

To improve the corrosion resistance of low-carbon microalloyed steel in marine environments,the corrosion behavior of the test steel with different cerium(Ce)contents in a marine environment simulated with 3.5%NaCl solution was studied by employing metallographic microscope,SEM,EBSD,and electrochemical analysis.The results show that the microstructure of the test steel mainly consists of ferrite and pearlite.Ce can refine the grains,reduce the size of inclusions,and modify the Al₂O₃,MnS,and Al₂O₃+MnS inclusions in the test steel into MnS+CeAlO₃ and Ce₂O₃.The modified inclusions significantly reduce the stress,thereby decreasing the probability of micropore and crack initiation.Additionally,the addition of Ce can decrease the corrosion current density of the test steel,increase the corrosion potential,reduce the content ofγ-FeOOH in the corrosion products,and increase the content ofα-FeOOH and Fe₃O₄,lowering the reaction activity and enhancing the protective effect of the rust layer on the substrate.Therefore,compared with low-carbon microalloyed steel without Ce addition,the low-carbon microalloyed steel with Ce addition exhibits better seawater corrosion resistance.

Ti₂AlNb alloy was prepared using high-energy ball milling and spark plasma sintering(SPS).The effects of second-sintering temperature on the microstructure and mechanical properties of the alloy were investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM),and universal tensile testing machine.The results show that the Ti₂AlNb alloys prepared at different second-sintering temperatures consist of B2 phase,equiaxedα₂ phase,and acicular O phase.When the second-sintering temperature is within the range of 900~950℃,the acicular O phase is precipitated as the second phase inside the B2 matrix phase,and the equiaxedα₂ phase agglomerates among the B2 matrix phase.And the equiaxedα₂ phase becomes less concentrated in its distribution and gradually decreases in its number in the range of second-sintering temperature from 1000℃to 1100℃.The Ti₂AlNb alloy prepared at the second-sintering temperature of 1000℃possesses good mechanical properties,with a room-temperature tensile strength of 309 MPa and a Vickers hardness of 466.5 HV.

Lithium niobate(LiNbO₃,LN)piezoelectric ceramics were prepared by vacuum hot-pressing sintering at 900℃and 35 MPa for 120 min.The effects of different Al₂O₃ doping amounts on their piezoelectric properties were studied.Through the analysis of phase,density,microstructure,piezoelectric and dielectric properties,it is found that within the range of Al₂O₃ doping amounts of 0.5%~3%(molar fraction),all LN piezoelectric ceramics samples exhibit the same position of main diffraction peaks that are sharp and indicative of a perovskite-type structure.with the increase of Al₂O₃ doping amount,the particle size of LN piezoelectric ceramics gradually decreases while the porosity increases both in size and quantity.In addition,the density and piezoelectric constant d₃₃increase at first and then decrease,reaching their maximum of 4.65 g/cm³ and 11.3 pC/N,respectively,at an Al₂O₃ doping amount of 1%.The above piezoelectric constant is 88.3%higher than that of LN piezoelectric ceramics prepared by laser sintering.At the test frequency of 1 MHz,the relative dielectric constant of LN piezoelectric ceramics increases gradually with the increase of Al₂O₃ doping amount.

Zr-Ti alloys with different Ti contents(0~15%by mass)were first prepared by vacuum consumable arc melting,and then turned into sheet samples.The metallographic microstructure of different alloy sheets was analyzed by optical microscope(OM),the mechanical properties by Vickers hardness tester and universal electronic tensile testing machine,and the fracture morphology by scanning electron microscope(SEM).The results show that Ti element can obviously refine the microstructure of Zr-Ti alloy.With the increase of Ti content,the hardness and strength of the Zr-Ti alloy sheets significantly improve,but the elongation decreases markedly.The fracture morphology of all the Zr-Ti alloy sheets is composed of dimples,indicating ductile fracture.And with the increase in Ti content,the fracture dimples of the alloy sheets become shallower,indicating that the ductile fracture characteristics of the alloy are weakened and the machinability is deteriorated.

Be-Al alloy was prepared by laser selective melting.The forming defects,microstructure,and hardness of the Be-Al alloy were analyzed under low or high laser power with two scanning strategies of layer by layer unidirectional line scanning and 67°interlayer staggered scanning.The results show that the primary forming defects in the Be-Al alloy include pores,micropores,hot cracks,and poor fusion.The pores are small in size and few in number,thus having little effect on the properties of the alloy.The micropores can be eliminated by using the 67°interlayer staggered scanning and increasing the laser power.The hot cracks are mainly caused by the tensile stress exerted on the liquid film in the long channels between the columnar structures at the center of the molten pool at the end of solidification,extending in the subsequent layer-by-layer deposition process.And the opening width of the hot cracks increases with the increase of energy density.The molten pool is affected by multiple thermal cycles when it is remelted by the surrounding newly scanned molten pool with a high lap rate,leading to a steady-state transition of Be-Al two-phase diffusion,dendrite growth of Be phase,and difussion of Al phase to cause microvoids that result in poor fusion.The microstructure of the Be-Al alloy prepared by additive manufacturing mainly consists of Al phase,Be phase,and some metastable microstructure,in which the Be phase and metastable microstructure collectively cause a significant residual stress in the alloy.Additionally,while the orientation of the Be phase base plane(0001)in the alloy has a certain preferential distribution,it also exhibits randomness.In contrast,the direction of Al phase(100)has an obvious preferential orientation along the scanning direction of the molten pool,resulting in the anisotropy of the alloy microstructure.Meanwhile,the hardness test along the scanning direction of the molten pool reveals that the Be-Al alloy exhibits higher microhardness due to its fine microstructure and a large number of metastable microstructure.

β-In₂Se₃ is widely used in various fields due to its good mobility and excellent photoresponse.However,Due to the fact that In₂Se₃ has multiple complex crystal structures and indium is prone to hydro-lysis,it is difficult to prepare layeredβ-In₂Se₃ in solution.Using InCl₃,Se powder and ethylenediamine as raw materials,β-In₂Se₃ powder was prepared by the solvothermal method.The structure,morphology and optical properties of the powder were characterized by Raman spectrometer,Fourier infrared spectrometer,thermogravimetric analyzer,scanning electron microscope and fluorescence spectrophotometer.The photocatalytic properties of the powders were investigated using methyl orange solution as the degradation substance.The results show that the main component of the prepared powder isβ-In₂Se₃ with a layered structure.The powder has good absorption in the UV and visible light regions,with an optical bandgap of approximately 2.01 eV,and has excellent fluorescent properties.β-In₂Se₃ powder exhibits photocatalytic activity towards methyl orange,and after 5 h of UV irradiation,the degradation rate of methyl orange can reach 81%.The result expands the application ofβ-In₂Se₃ for the degradation of organic pollutants.