In view of arsenic and ammonia nitrogen existing in wastewater from tungsten metallurgy and high alkalinity of the wastewater,principle,efficiency,advantages and disadvantages of various treatment methods are analyzed and reviewed.The treatment processes of ammonia nitrogen wastewater are mainly introduced,and their advantages and disadvantages are analyzed during application in tungsten metallurgy.It is pointed out that the combined process can deeply remove ammonia nitrogen,save energy consumption and avoid secondary pollution.And the development direction of wastewater treatment is discussed.

Experimental research was carried out on selective leaching of the valuable elements such as Ga,Al and K in gallium-containing alunite concentrate.Under the conditions of leaching temperature 80 ℃,leaching time 120 min,agitation speed 300r/min,H2SO4 concentration 70g/L and liquid to solid ratio4∶1,the leaching rates of Al and K are 81.7% and 89.1%,respectively,while the leaching rate of Ga is0.72%.Ga content in the leaching slag is 171.3g/t,which is 3.16 times as rich as the raw material,showing that Ga is separated from Al and K.

Titanium was recovered from red mud by acid leaching with sulfuric acid,hydrochloric acid or nitric acid as the leaching agent.The effects were investigated of kind and concentration of leaching agents,liquid to solid ratio,leaching temperature and reaction time on titanium recovery.The results show that sulfuric acid is more appropriate as the leaching agent.The leaching rate of titanium reaches 90% under the conditions of sulfuric acid concentration 40%,leaching temperature 100℃,liquid to solid ratio 6∶1and reaction time 60 min.Brookite and calcite disappear,perovskite,hematite and cancrinite decrease and anhydrite forms during acid leaching.Dissolution reaction of perovskite and brookite in sulfuric acid results in titanium recovery from red mud.

WC powder was prepared with mechanical activation assisted molten salt method,where W powder and active C powder were mechanically activated at first and then reacted in molten salt.And the reaction mechanism of WC formation in molten salt was discussed.The research shows that W2 C and WC powders can be successfully prepared in 1 000℃ molten salt.Both the increased reaction temperature and activation time contribute to the formation of W2 C.W2C would gradually transform into WC with the further prolonged time of heat preservation.

W-20%Cu composite material was successfully prepared by SPS with W-20%Cu(mass fraction)composite powders as raw materials obtained by hydrothermal synthesis-coreduction,and its microstructure and properties were analyzed and studied.The results show that with the increase of sintering temperature and heat preservation time,microstructure distribution of W and Cu is more uniform with less porosity,and density,hardness and electrical conductivity of W-20%Cu composite material are subsequently increased.Under the conditions of sintering temperature 950 ℃ and heat preservation time 5min,the density,hardness and electrical conductivity of W-20%Cu composite material are 98.9%,HV222.8and 21.7 MS/m,respectively.

The heavy tungsten alloy of 93W-4.55Ni-1.95Fe-0.5Co was prepared by direct liquid phase sintering process and two-stage sintering process(i.e.solid-state sintering at first and then liquid phase sintering)and its microstructure and properties were investigated.The results show that sintering distortion of the alloy can be controlled by using two-stage sintering process,the distribution of tungsten grain and binder phase is more homogeneous,and the mechanical properties especially ductility and toughness are improved to a great extent.

The principle of X-ray diffraction(XRD)and its application in tungsten powder metallurgy are introduced.Combined with the authors' research on WC-Co nanocomposite powder,the application of XRD technique in preparation of WC-Co nanocomposite powder is emphatically introduced,including qualitative phase analysis,grain size determination and lattice parameter determination.Using soluble cobalt salt,ammonium metatungstate(AMT)and organic carbon source as main raw materials,WC-Co nanocomposite powder was prepared by spray conversion and continuous low-temperature reduction carbonization and the samples were analyzed by XRD during preparation.The results show that the composite powder only having the two phases of WC and Co can be prepared by spray conversion and continuous low-temperature reduction carbonization,W is completely carbonized,the grain size of WC is about 60 nm,and Co phase exists with face-centered cubic structure.

The precursor of fluorine-containing cerium-based rare earth polishing powder was obtained by fluoridization of cerium-based rare earth carbonate added with hydrofluoric acid,and then it was roasted at high temperature and ground and graded to prepare fluorine-containing cerium-based rare earth polishing powder.The effects were investigated of two fluoridization methods on phase structure,particle size and distribution and polishing performance of fluorine-containing cerium-based rare earth polishing powder.The results show that fluoridization method has no obvious effect on polishing performance of cerium-based rare earth polishing powder.However,the particle size is significantly reduced of the polishing power and its precursor prepared by fluoridization with hydrofluoric acid at first and then precipitation with ammonium bicarbonate,and their particle size distribution is narrower.

NdFeB permanent magnet was prepared by rapid solidification strip casting and hydrogenation crushing,and its microstructure and properties were characterized by optical microscopy,scanning electron microscopy and AMT—4magnetic property tester.Investigation was made of the effect of sintering temperature on the microstructure and properties of the magnet.The results show that with sintering temperature increasing,the density of the sintered magnet increases,and its remanence,coercivity and maximum magnetic energy product increase at first and then decrease.The reason is that the major crystalline phase grains grow up and the neodymium-rich phase distribution is more homogeneous with sintering temperature increasing.However,when the sintering temperature reaches a certain value,the magnet microstructure is inhomogeneous and the neodymium-rich phase agglomerates.

LaFe11.1-xCrxCo0.8Si1.1B0.25 and LaFe11.1-xTixCo0.8Si1.1B0.25 series alloys were prepared by adding a small amount of Cr and Ti elements into LaFeCoSi-based alloy,and their magnetocaloric effects were measured using directly measuring instrument at 1.5T magnetic field.The experimental results show that both Cr addition and Ti addition have influence on Curie temperature and magnetocaloric effect of the serie alloy.The properties of the material can be adjusted to some extent taking advantage of these alloying elements.