Tungsten slag contains not only valuable elements such as W,Sn,Ta and Nb,but also toxic elements such as As and Pb.If tungsten slag is randomly stacked or buried,not only the environment will be polluted,but also its value as secondary resources will be wasted.This paper reviews the research progress of comprehensive recovery and utilization technologies of alkali-boiled tungsten slag,such as hydrometallurgy,beneficiation-metallurgy combination,pyro-hydrometallurgy combination and pyrometallurgy.Their technical advantages and disadvantages are analyzed.It is pointed out that pyrometallurgy has the characteristics of short process flow and will become the development direction of comprehensive utilization technology of alkali-boiled tungsten slag.

The reduction smelting process was used to process wolframite alkali-leaching residue and recover valuable elements such as Fe,Mn,W,Sn and Nb in the form of alloys,and the harmful elements such as As and Pb were separated.The effects of reducing agent(graphite powder)dosage,smelting temperature and time on smelting efficiency were studied.The experimental results show that the alloying rates of Fe,Mn,W,Sn and Nb in wolframite alkali-leaching residue are 88.67%,56.28%,98.23%,67.74% and 84.72%,respectively,when reducing agent dosage is 16%,smelting temperature is 1550℃,and smelting time is 120 min.Meanwhile,As,Pb and Bi basically enter the smoke and dust.

Vacuum induction smelting experiments were carried out using beryllium beads with different magnesium contents and different particle size ratios,and the effect of the chemical composition and particle size of the beryllium beads on the yield of beryllium ingots was investigated.Based on the long-term accumulated production experience,the influences of design and manufacture of beryllium oxide crucible,control of smelting power,smelting vacuum,casting temperature and speed on the yield of beryllium ingots are discussed.The experimental results show that the beryllium ingot yield is increased by 5%~8% on ave-rage,by strictly controlling the magnesium content(<0.8%)of the raw beryllium beads,scientifically matching the particle size of beryllium beads and reasonably arranging the furnace loading sequence,carefully designing and manufacturing beryllium oxide crucibles,and controlling the smelting power,vacuum,casting temperature and speed.

The reaction process and thermodynamic properties of silver extraction with sulfonated kerosene as diluent and octylamine as extractant were studied.Silver was extracted in temperature range of 293.15~318.15K and ionic strength of 0.2~2.0mol/kg.The pH value of aqueous phase was determined by pH meter,and the silver content in aqueous phase was determined by atomic absorption spectrophotometry.The extraction rate of the extraction reaction was calculated and the optimum extraction conditions were determined.The standard equilibrium constant K■ at different temperatures wow obtained by polynomial fitting,and the relations between K■,entropy or enthalpy,Gibbs free energy and temperature were stu-died.The experimental results show that low temperature and low ionic strength are more conducive to the extraction of silver by octylamine.Thermodynamic calculation shows that the Gibbs free energy,enthalpy and entropy of extraction reaction increase with the decrease of temperature,which are negatively correlated with temperature.

La₂Y₂Al₂O₉ fluorescent matrix material was synthesized by solution combustion method with lanthanum nitrate hexahydrate,yttrium oxide and aluminum nitrate nonahydrate having La:Y:Al molar ratio of 1:1:1 as raw materials,and glycine(C₂H₅NO₂),mannitol(C₆H₁₄O₆)and urea(CO(NH₂)₂)as combustion agents,respectively.The effects of calcination temperature,calcination time and combustion agents on the phase and appearance of the synthetic powder were analyzed by X-ray diffractometer(XRD)and scanning electron microscope(SEM).Under the optimized process conditions of glycine(C₂H₅NO₂)as combustion agent,calcination temperature 800℃ and calcination time 4 h,a new compound La₂Y₂Al₂O₉ with high crystallinity and purity,good morphology and hammer net distribution can be obtained,and it belongs to the monoclinic crystal system.The luminescent properties of La₂Y₂Al₂O₉ powder were characte-rized by ultraviolet visible spectrometer and fluorescence spectrometer.The results show that the product has a wide and strong ultraviolet absorption band at 200~400 nm and a wide fluorescence excitation band at 350~440 nm.Therefore,La₂Y₂Al₂O₉ powder can be used as a matrix material in the preparation of luminescent powder.

Taking the third-generation titanium alloy as the research object,the preparation processes such as vacuum melting,powder metallurgy,additive manufacturing and gel-casting are introduced,as well as the treatment processes including cold rolling,aging,laser peening and so on.The biocompatibility of biomedical titanium alloy is reviewed,as well as the effects of microelement addition and such treatment processes as cold rolling and aging on the mechanical properties of various as-cast titanium alloys.The application of biomedical titanium alloy is also prospected.

Using Ti-46.2%Al-8%Ta as the experimental material,TiAl based alloy powder was prepared by spark plasma discharge method with different dielectrics.The results show that when the dielectric is anhydrous ethanol,the composition of the prepared powder is TiC and Al₂O₃,the sphericity of the powder is very low,and the oxygen content is very high.When the dielectric is liquid nitrogen,the powder is composed of TiN and AlN,and the nitrogen content in the powder is very high.When the dielectric is liquid argon,the composition of the prepared powder is TiAl,and the quality of the powder is relatively high,but the powder yield is very low.In subsequent research,liquid argon can be used as the dielectric and the process parameters need to be continuously optimized to further increase the output of the powder,while the quality of the powder is ensured.

The combination of preparation process of high-k dielectric HfO₂film and in-situ deposition process of graphene was studied.Vacuum electron beam evaporation was used to deposit HfO₂ film on heavily doped Si substrate at room temperature,and the film samples were rapidly annealed for 90 s at a constant temperature of 400℃,450℃ and 500℃,respectively.AFM test results show that the root mean square roughness of the HfO₂ film surface after annealing treatment is not higher than 0.30 nm,which is at a low level.XRD test results show that the annealing treatment at different temperatures does not change the film structure,and all the samples are amorphous.Impedance test results show that the relative dielectric constants of the three groups of film samples are greater than 21 and their dielectric loss level is low,indicating that the HfO₂ films have good dielectric properties.The HfO₂ film prepared by electron beam evaporation at room temperature was used as the substrate,and graphene was grown in situ by PECVD at low temperature of 400℃,450℃ and 500℃.AFM and Raman test results show that the surface of the graphene sample deposited at 500℃ has the highest flatness within 10 layers,which achieves a good combination of the preparation processes of the insulating dielectric layer and the active layer of the graphene device.

The thermal decomposition of ternary materials and electrolyte was systematically studied by differential scanning calorimetry(DSC).The effects of different potentials and the amount of electrolyte on the thermal decomposition of ternary materials were analyzed.The results show that the thermal decomposition process of ternary materials undergoes a structural transformation from lamellar structure to spinel and then to rock-salt phase,accompanied by the precipitation of oxygen.The higher the Ni content and the higher the potential,the worse the thermal stability of the ternary material with lower thermal decomposition temperature and greater thermal decomposition enthalpy.For high-nickel materials,there is a corresponding relationship between the thermal stability and the structural phase change during charging,and there is an obvious difference in thermal stability at the phase transition point.The decomposition of electrolyte goes through the endothermic process of lithium salt decomposition and the exothermic process of the reaction of decomposition products with gasification solvent,and the addition amount of electrolyte has a great influence on the thermal decomposition process of ternary materials.

Mg-3.5 Li-6 Al alloy was prepared by alloy smelting,heating and melting of high-purity raw materials,and flux-mixed gas combined protection.The composition,phase,microstructure and mechanical properties at room temperature or high temperature were tested and analyzed.The experimental results show that the magnesium-lithium-aluminium alloy prepared in this way has uniform microstructure and mechanical properties,mainly composed ofα-Mg and Al-Li phases,and Al-Li is distributed in flakes.The peak value of flow stress increases with the increase of strain rate,and decreases with the increase of temperature.The high temperature deformation constitutive equation of Mg-3.5 Li-6 Al can be described by hyperbolic sinusoidal function.The strain activation energy of the alloy at high temperature is 126 kJ/mol,the stress index is 3.98,and the deformation of the alloy is controlled by intracrystalline diffusion.