The properties of selenium are introduced, as well as its distribution and resource situation. The extraction-separation methods and application of selenium are expounded emphatically. Meanwhile, the fu-ture development and utilization of selenium resources is pointed out.

Tungsten and molybdenum separation is a technical problem in tungsten and molybdenum extrac-tive metallurgy. The main processes, separation principle and latest development of tungsten and molybde-num separation are summarized. And recommendations for future research and development direction of tungsten and molybdenum separation are made.

Based on the character and composition of lead-tellurium slag, the two-stage leaching process was applied of alkaline leaching-washing-acid leaching. Influences of alkali concentration, leaching temperature, leaching time and liquid to solid ratio were investigated on the leaching rate of lead-tellurium slag. The re-sults show that the optimum alkaline leaching conditions are sodium hydroxide concentration of 100 g/L, leaching temperature of 90 ℃ ,leaching time of 4 h and liquid to solid ration of 10 ： 1. Under the above con-ditions, tellurium leaching rate is 88.80 %. The optimum acid leaching conditions are as follows：hydrochlo-ric acid concentration of 2.5 mol/L,leaching temperature of 75 ℃ ,leaching time of 4 h,and liquid to solid ratio of 5 ： 1 ,and the total tellurium leaching rate is 98.9%.

The object of the study is the spent auto-exhaust catalyst, and its precious metals were recovered by leaching and extraction processes. The results indicate that 80 mL aqua regia has the optimal leaching effects of precious metals by leaching at 80 ℃ for 4 h,with platinum leaching rate of 95.96%. Using tribu-tyl phosphate or trioctylamine as the extractant, extraction effects of leaching solution were studied under different conditions. The results show that the kerosene solution of 10% trioctylamine has the best extrac-tion efficiency for precious metals. Thiourea-hydrochloric acid has low stripping rate from metal-containing extract liquid.

The energy band structure,density of electronic state and absorption spectra of anatase TiO2 be-fore and after W doping were calculated using first-principles based on density functional theory. The re-sults indicate that the band gap of anatase TiO2 narrows and its Fermi level moves into the conduction band after W doping. Substitutional W atoms have significant effects on electronic states of the nearest Ti and O atoms,hut not for the Ti and O atoms far away. W doping weakens UV and visible light absorption of ana-tase TiO2, consistent with the transmission spectra of undoped and W-doped TiO2 films obtained by exper-iments.

The measurement methods are introduced for particle size of CeO2 polishing powders. Research progress are reviewed on the influences of the particle size on polishing process and the related mathemati-cal models. Meanwhile, the existing problems and future research direction of CeOz polishing are pointed out.

Analysis is made of the influences of addition of different mass fraction of Dy2 Oa powders during milling on density, microstructure, orientation degree and magnetic properties of the sintered Nd-Fe-B mag-net （PrNd） 32. 5 Febal Nb0.65 Cu0.20 Al0.65 B1.15. The results show that with the increase of Dy2 O3 the average grain size of the magnet decreases at first and then rapidly increases, its dens mass fraction, ity slightly clines,and orientation degree gradually rises. Both Br and （BH）max decrease linearly with the increase Dy2O3 dosage while Hcj increases and then decreases. During liquid p sulting from Dy diffusion into the ence microstructure and magnetic linearly, and the squareness of d hase sintering process of the mag primary phase grains and Nd2 O3 properties of the magnet. Adding de-of emagnetization curve increases at first net,both （Nd,Dy）2Fe14 B formation re-formation in grain boundary can influ- appropriate Dy2 O3 is beneficial for im- provement of microstructure, orientation degree and magnetic properties of th fraction of Dy2O3 is 0.8%, the grain size of the magnet reaches the minimum of tion,the surface morphology is regular, and the squareness of demagnetization e magnet the most curve is also When the mass uniform distribu-lso the highest.

The magnetic abrasive grains were prepared by hot-pressing sintering and the influences of sinte-ring temperature,pressure and heat preservation time were investigated on the hardness of magnetic abra-sive grains. The results show that with the increase of sintering temperature,the hardness of magnetic ab-rasive grain sample greatly increases, and it begins to decrease when the temperature reaches 1 100 ℃. Meanwhile,it increases as sintering pressure and heat preservation time increase. Under the conditions of sintering temperature 1 100 ℃ ,sintering pressure 50 MPa,heat preservation time 30 rain,the magnetic ab-rasive grains with hardness of HV300-HV310 can be obtained.

With CuC12 as copper source and Na2CO3 as precipitant,CuO microspheres of 1-3 μm diameter were successfully synthesized via hydrothermal method at 180 ℃ for 24 h. The samples were characterized using X-ray diffraction,thermal field emission scanning electron microscope and ultraviolet-visible absorp- tion spectroscopy, respectively. The results indicate that with the increase of Na2 CO3 dosage, the morpholo- gy of CuO microspheres changes from needle-like shape to granular shape. And then needle-like CuO spon- taneously aggregates to form CuO microspheres. CuO microspheres have good optical absorption proper-ties.

The effects of solution and aging on microstructure evolution of thixoformed AZglD magnesium alloy were studied as well as relation between alloy microstructure and mechanical properties. The results show that solution and aging treatment have a significant impact on microstructure of the alloy. The pre-cipitated phase is distributed at the grain boundaries in the form of flake after a certain time of aging. The alloy has obvious age-hardening characteristics. After solution and aging for 16 h, tensile strength, yield strength and hardness of the alloy are 210 MPa, 147 MPa and HV66,respectively, 98 MPa, 65 MPa and HV10 higher than those of the cast alloy. The cast alloy presents intergranular fracture,transformed into intergranular-cleavage mixed fracture of obvious cleavage fracture characteristics after solution and aging.