Experimental research was carried out on comprehensive recovery of scheelite from molybdenum flotation tailings with a new reagent YP as the collector of scheelite based on the process of heating cleaning of crude scheelite concentrate.The grade of the resultant scheelite concentrate is 65.07%and its recovery is 82.82% by heated closed-circuit tests,increased by 5.97% and 5.92%,respectively,compared with those by normal closed-circuit tests.

Influences of Fe3+on spodumene flotation and its mechanism were systematically studied through flotation tests of pure spodumene,measurement of electric potential,infrared spectrum test and Fe3+solution chemical analysis.The results indicate that the flotation recovery of spodumene is significantly increased with the addition of Fe3+.The surface potential of spodumene significantly shifts after activated by Fe3+and then interacting with the collector,proving that Fe3+is absorbed strongly on the surface of spodumene.IR characteristic absorption peaks of oleic in spodumene are remarkably enhanced after activated by Fe3+and then interacting with the collector,indicating that the addition of Fe3+contributes to the adsorption of oleic acid on spodumene surface.

Vanadium was extracted by roasting with composite additives and leaching with dilute acid.Impacts were investigated of composite additive dosage,roasting temperature,roasting duration,sulfuric acid dosage,leaching duration,leaching temperature and liquid-solid ratio on vanadium leaching rate.The results show that under the conditions of composite additive dosage 6%,roasting temperature 800 ℃,roasting duration 3h,sulfuric acid dosage 3%,leaching duration 3h,leaching temperature 60℃and liquid-solid ratio 3∶1,the vanadium leaching rate of the above process is85.6%,increased by 13.4%compared with that of calcification roasting process.This technology has a good application prospect as an environment-friendly process with less off-gas pollution during roasting and substantially improved vanadium leaching rate.

Vanadium extraction technology was studied from clay vanadium ore by sulphation roasting-water leaching,and the effects were investigated in detail of concentrated sulfuric acid dosage,roasting temperature and time during sulphation roasting,and water temperature,liquid-solid ratio and leaching time during water leaching.The results show that under the conditions of concentrated sulfuric acid dosage 35%,roasting temperature 250℃,roasting time 3hduring sulphation roasting,and leaching temperature 60℃,liquid-solid ratio 4∶1and leaching time 1.5hduring water leaching,average V2O5 leaching rate is 88.98%,and V2O5 content in the leaching residue is lower than 0.2%.

Industrial experiment and production practice are introduced on tellurium extraction from tellurium slag in silver smelting furnace.The influence factors are emphatically analyzed and discussed of overlimit impurity in each process step.And the improvement measures are put forward.

Sources and properties and treatment measures of three wastes are comprehensively introduced during separation of ion-absorbed rare earth deposits.All kinds of wastes are effectively treated and discharged up to the standard by taking reasonable measures.

WC-10Co-4Cr coatings were prepared on 45#steel by plasma spraying(APS),supersonic plasma spraying(SAPS)and high velocity oxy-fuel thermal spraying(HVOF),respectively.The porosity,microhardness,and wear resistance of the three coatings were analyzed and compared.The results show that the two coatings prepared by SAPS and HVOF have similar performance and single phase composition similar to the powders.Compared with the coating prepared by APS,the two coatings prepared by SAPS and HVOF have higher density and microhardness and better wear resistance.

Different amounts of WC was added to the ternary boride Mo2FeB2-based cermet and then vacuum liquid phase sintering was carried out.The sintered samples were characterized.The results show that WC addition doesn't affect the in-situ liquid phase reaction process to generate the ternary boride Mo2FeB2.WC can be the nucleation center of Mo2FeB2 particle to promote material densification during sintering.WC particles and Mo2FeB2 particles well combine to form dual hard phase,dispersing in Fe-based binder phase and effectively enhancing hardness and wear resistance of the Mo2FeB2-based cermet.When mass fraction of the added WC is 20%,the sintered sample has the highest hardness of HRA87.9improved by 7.2%,and the best wear resistance increased by 10 times under the experimental conditions of wheel grinding.

Ti(C,N)-xWC-Ni-Mo-C cermets with different WC contents were prepared by powder metallurgy.Microstructure,fracture morphology and crack propagation path were analyzed by SEM.The results show that the cermets contain black core-gray rim microstructure,as well as white core-gray rim microstructure.The grains are refined with appropriate WC addition,while the grains grow up with 20% WC.The main fracture models of the cermets are intergranular fracture and transgranular fracture.Crack bridging,crack deflection and microcrack occur during crack propagation.

TiC-TiB2 composite ceramics with different Cr content were prepared by combustion synthesis in high gravity field using Ti+B4C as the primary reactive system assisted by different contents of CrO3+Al as the enhancement system.XRD,FESEM and EDS results show that the prepared composite ceramics are mainly composed of many fine TiB2 platelet grains and TiC spherical grains,and most Cr-rich metal phase intertwines with TiB2 platelet grains.With the content of CrO3+Al increased,system adiabatic temperature rises,and volume fraction of Cr-rich metal phase in TiC-TiB2 composite ceramic increases.It is supposed that Ti-Cr-C-B alloy liquid is the product of combustion reaction in high gravity field.During cooling and solidification of the alloy liquid,TiC nucleates and precipitates at first and then TiB2 precipitates.Finally,Cr and a small amount of unreacted Ti precipitate to fill the shrinkage cavity in the skeletal structure of TiB2 platelet grains and thereby increase the density of TiC-TiB2 composite ceramics.