WC-6%Co nanocomposite powder was prepared by spray conversion,calcination and low temperature reduction carbonization.And then ultrafine grain WC-Co cemented carbide of about 400 nm WC grain size was successfully prepared with the above nanocomposite powder as the raw material by wet milling,molding and pressure sintering without grain growth inhibitors.The properties of the prepared cemented carbide were compared with those by traditional processes.The results show that the cemented carbide prepared with the nanocomposite powder has more uniform WC grain size and component distribution than those by traditional processes,and it has no abnormally grown grains with higher strength and hardness.

Study was made on the effects of different sintering pressure on metallographic microstructure and physical and mechanical properties of WC-12%Co coarse grained cemented carbide.The results show that the cemented carbide can be highly densified at relatively low sintering pressure.With the increase of sintering pressure,three properties of the cemented carbide have no obvious change.When sintering pressure is about 2 MPa,both flexural strength and impact toughness of the cemented carbide are highest with good comprehensive performance.

The LaB6 sample was dissolved with dilute nitric acid,and then its boron content was determined by acid-base titration with EDTA as the masking agent and mannitol as the complexing agent of boronic acid.Sample dissolution methods,reagent dosage,judgment methods of titration end-point,interfering elements,recovery ratio and precision were investigated.Operation with the method is simple and fast,and the method has good accuracy and precision with boron recovery of 99.45% ~100.48% and RSD less than0.50%。

With conventional pickling process parameters of zirconium alloy pipe,study was made on the law of influence of inner diameter,sampling location,water temperature and flaw depth of the alloy pipe during pickling on its fluorine residue.And the experimental results were analyzed in theory by using finite element method(FEM).The results show that with the increase of Zr-4alloy pipe inner diameter,fluorine residue on pipe inner surface gradually increases.Fluorine residues in the head,middle and tail of Zr-4alloy pipe are nearly identical.With the increase of water temperature,fluorine residue on Zr-4alloy pipe inner surface is reduced.Fluorine residue has no obvious corresponding relation with flaw depth of Zr-4alloy pipe.

Focusing on the occurrence of vanadium in carbonaceous shale,the important role of roasting in the process of extracting vanadium from carbonaceous shale is discussed,and the technical conditions of various roasting processes during extracting vanadium from carbonaceous shale are introduced as well as their advantages and disadvantages.The development trends are forecasted of extracting vanadium from carbonaceous shale in the aspects of comprehensive utilization,beneficiation-metallurgy combination and environment protection.

Experimental study was made on the influence of Na2CO3 as the additive and leaching agent on roasting-leaching of vanadium-bearing carbonaceous shale from Hunan.The results show that vanadium leaching rate changes with different roasting temperature and time and Na2CO3 dosage.The optimal roasting conditions are 800 ℃×2h and 2% Na2CO3 relative to the amount of ore.

The experimental study of vanadium extraction was carried out by direct acid leaching from the burning ash of low-calorific-value vanadium-bearing carbonaceous shale blended with coal.Based on single factor tests,the process conditions were determined including leaching liquid-solid ratio,dosage of sulfuric acid and aid leaching agent,leaching temperature,leaching time and stirring speed.Under the optimum leaching conditions,the leaching rate of vanadium in the ash is over 79%.

The static reducing process was studied for producing V2O3 in the resistance furnace using V2O5 as the raw material and solid carbon material as the reducing agent.The process has the advantages of low consumption of reducing agent,easy operation and high safety factor.Meanwhile,two-stage reduction was carried out during operational control with the first temperature of 650 ℃ and the second temperature of 1050 ℃,reducing vanadium loss and improving conversion speed of V2O5.And then high quality V2O3 can be obtained to provide high quality raw material for the production of high vanadium ferrovanadium and significantly reduce its production cost.

The feasibility was studied of leaching rare earth by column leaching from a low-grade rare metal complex ore containing a small amounts of rare earth and new-found in southwest China.The results show that weathered-crust elution-deposited rare earth ore in adsorption state is only about 30% in the above rare metal complex ore,and most of the rare earth exists in the presence of unweathered independent mineral deposit.After the above ore is processed by roasting-acid leaching,the leaching rate of rare earth is above 81%,the leaching rate of Nb is above 88%,and the leaching rate of Ga reaches 99.08%,with good leaching results of rare earth,niobium and gallium.

The process was studied of rare earth and niobium extraction from tailings of beneficiated complex rare metal associated ore.The results indicate that rare earth and niobium can be efficiently leached by sulfuric acid acidification-staged leaching.When the mass ratio of acid to ore is 1.8,acidification temperature is 350℃,acidification time is 120 min,the liquid-solid ratio of the first leaching stage is 1∶1,leaching temperature is 80℃,leaching time is 90 min,the liquid-solid ratio of the second leaching stage is 8∶1,leaching temperature is 25 ℃ and leaching time is 9 0min,the REO and Nb2O5 contents in the leached tailings are 0.96% and 0.75%,respectively,and the leaching rates of rare earth and niobium are 85.03% and 80.88%,respectively.Niobium leaching rate is 80.26% in the first stage and rare earth leaching rate is83.85%in the second stage.The recovery of niobium and rare earth can be realized by separately treating with the leaching solution from the first stage and the second stage.