Mm_0.75Mg_0.25Ni_3.5Co_0.2Al_0.3(Mm represents lanthanum-rich mixed rare earth)as-cast alloy was prepared in a high-frequency induction levitation furnace and then annealed at different temperatures.XRD analysis shows that the alloy is mainly composed of LaNi₅ phase and La₂Ni₇ phase.The diffraction peaks of LaNi₅ and La₂Ni₇ alloy phases are strengthened after annealing treatment.At the annealing temperature of 800℃,the unit cell volume of La₂Ni₇ reaches the maximum value of 0.5497nm³,indicating that Co and Al alloying elements can be better dissolved in the main phases after annealing treatment at 800℃.Elec-trochemical test analysis shows that the annealed alloy at 800℃ has a maximum discharge capacity of up to 351.5 mA·h/g,a capacity retention rate of 82.3%after 130charge-discharge cycles,and excellent high-rate discharge performance.

The WC-5.7%Co-5.7%Ni-0.13%Cr medium-grained cemented carbide mixture with carbon content in the range of 6.00%~6.16%was prepared,and then the cemented carbide samples were sintered by hydrogen dewaxing low-pressure sintering integrated furnace.Optical microscope was used to observe the metallographic microstructure of the alloy,X-ray diffractometer was used to analyze the phases of the alloy,scanning electron microscope was used to observe the microstructure of the alloy,and energy disper-sive spectrometer was used to determine the composition ofγphase in the alloy.The results show that there is no decarburization and carburization in the alloy with carbon content of 6.00%~6.16%.The ben-ding strength,hardness and density of the alloy decrease to different extent with the increase of carbon con-tent.The magnetic cobalt ratio of the above alloy is much lower than that of tungsten-cobalt alloy with the same adhesive content,and it increases with the increase of carbon content.The change trend of coercive force of the above alloy is different from that of the traditional tungsten-cobalt alloy:The coercive force in-creases with the increase of carbon content.

In order to study the effect of WC grain size of ultrafine cemented carbide on its friction and wear properties, ultrafine cemented carbides with the average WC grain sizes of 0.25 μm, 0.35 μm and 0.50 μm were prepared by different sintering processes.The alloys were characterized and analyzed by density ba-lance, hardness tester, friction and wear tester, 3 D contour scanner and scanning electron microscope.The results show that the relative density and hardness of the alloys decrease with the increase of WC grain size.The alloy with an average WC grain size of 0.25 μm has high hardness, can effectively resist the effect of grinding balls during reciprocating friction, and has a shallow depth of wear scars, showing good wear resistance.When the average WC grain size increases to 0.35 μm, the penetration depth of the grinding ball significantly increases, and the wear resistance of the alloy decreases.Continuing to increase the average WC grain size to 0.50 μm, the hardness of the alloy continues to decrease, some broken WC particles appear in the wear morphology, the penetration depth of the grinding ball further increases, and the wear resistance is the worst.

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Scheelite is the main industrial raw material for tungsten smelting in China.Most of scheelite concentrates are obtained by flotation, and therefore a large number of organic flotation reagents remain in the concentrates, which can easily lead to overswelling phenomenon during subsequent hydrometallurgical smelting and bring adverse effects on production.At the same time, the traditional alkali pressure boiling process of scheelite is of low production efficiency, and there are certain safety risks.To solve the above problems, a new smelting process for decomposing scheelite through sodium phosphate roasting-water lea-ching-sodium phosphate crystallization cycle was proposed.The research results show that under the conditions of mass ratio of sodium phosphate to scheelite of 2∶1,roasting temperature of 700 ℃,roasting time of 2 h, water leaching temperature of 80 ℃,water leaching time of 2.5 h and water leaching liquid to solid ratio of 2.5∶1,the leaching rate of tungsten reaches 99.81%.The excess sodium phosphate in sodium tungstate solution can be crystallized by adding sodium hydroxide, the recovery rate of sodium phosphate can reach more than 97%,and the sodium phosphate can be recycled for the decomposition of scheelite concentrate.This process can effectively overcome the adverse effects of flotation reagents on traditional hydrometallurgical tungsten smelting, and efficiently improve the utilization rate of scheelite decomposition reagents.

The process of preparing APT by evaporation and crystallization method is simple, but the particle size of the prepared APT is relatively large, which seriously reduces the quality of subsequent products.The influences of stirring speed, ammonium tungstate concentration, and reaction temperature on the D;and Span of APT were studied by response surface method, and then the evaporation and crystallization process of APT was optimized.The results show that among the three factors, the order of influence on D;is reaction temperature>ammonium tungstate concentration>stirring speed, and the order of influence on Span is ammonium tungstate concentration>stirring speed>reaction temperature.The optimal process conditions are stirring speed of 271 r/min, ammonium tungstate concentration of 178.9 g/L,and reaction temperature of 81.6 ℃.Under the optimal process conditions, the D;and Span of the APT prepared in the experiment are 20.31 μm and 1.323,respectively, which are greatly reduced compared with other samples.The reason for the reduction is that low stirring speed and low reaction temperature inhibit crystal growth, and high ammonium tungstate concentration promotes crystal nucleation.

The electrolytic manganese anode slime was subjected to harmless resource treatment by reduction roasting-acid leaching technology to reduce tetravalent manganese to divalent manganese.The reduction product was used as raw material for electrolytic manganese production,and the valuable metal Pb in the slag was also recovered.The experimental results show that when the reduction roasting temperature is 850~900℃,the roasting time is 40~60 min,and the reducing agent dosage is 10%~15%,the manganese leaching rate in sulfuric acid system is more than 99%,the lead content in the slag is more than 50%,and the best effect is achieved of reduction roasting-acid leaching treatment of electrolytic manganese anode slime.

Tungsten powders were prepared by hydrogen reduction with chromium-doped tungsten oxide, purple tungsten oxide and yellow tungsten oxide as raw materials at different reaction temperatures.The phase and microstructure of tungsten powders prepared by reduction of different tungsten oxides were analyzed by XRD and SEM,and the influence of chromium doping on the reduction process of tungsten oxide was explored.The results show that under the same reduction conditions, purple tungsten oxide is the easiest to reduce due to its loose and breathable fine needle-like structure, and the prepared W powder has good dispersibility, fine particle size and uniform distribution.Chromium-doped tungsten oxide is the most difficult to reduce due to the inhibitory effect of Cr₂O₃,and the prepared W powder has a large number of fine-grained aggregates, with poor powder particle size uniformity and small average particle size.The reduction difficulty of yellow tungsten oxide is between purple tungsten oxide and chromium-doped tungsten oxide due to its dense and airtight cubic structure, and the prepared W powder has coarse particle size and serious agglomeration.