The method of sulfation roasting-selective decomposition-water leaching was used to recover rare earth from CeFeB waste,and meanwhile the reaction mechanism of CeO₂ and Ce valence change in the re-covery process were investigated.The results show that the optimal recovery process conditions are sulfuric acid concentration of 14.5mol/L,sulfuric acid dosage of 2times the theoretical amount,sulfation roasting temperature and time of 300℃and 60min,and selective decomposition temperature and time of 700℃and 120min.Under the above optimized conditions,the rare earth leaching rate reaches 95.46%,the impurity Fe enters into the filter residue in the form of Fe₂O₃,and the rare earth oxide Nd_0.20Ce_0.80O_1.90is ob-tained after the leaching solution is precipitated with oxalic acid and the precipitate is roasted.The products of sulfation roasting process are Ce(SO₄)₂,RE₂(SO₄)₃and Fe₂(SO₄)₃.Ce₂(SO₄)₃,Fe₂O₃and indecompo-sable other RE₂(SO₄)₃are obtained in the selective decomposition process,and the decomposition product SO₃further reacts with unreacted CeO₂to form Ce₂(SO₄)₃.During the water leaching process,the water-soluble Ce₂(SO₄)₃and RE₂(SO₄)₃dissolve into the leachate,and the water-insoluble Fe₂O₃enters into the filter residue,thereby realizing the effective separation and recovery of rare earth from CeFeB waste.

Titanium dioxide waste water is a kind of acidic waste water containing a lot of iron ions, which has important recovery value.Using titanium dioxide waste water as raw material, ferrous oxalate was prepared by adding sodium oxalate.The effects of sodium oxalate dosage, reaction temperature, stirring strength and reaction time on the precipitation rate of iron were analyzed.The phase and microstructure of the precipitated products were analyzed by XRD and SEM-EDS.The results show that the precipitation rate of iron is more than 82% under the optimized conditions of titanium dioxide waste water volume of 50 mL,temperature of 20 ℃,sodium oxalate dosage of 12 g, stirring strength of 300 r/min and reaction time of 30 min, and the precipitate is the granular crystal of ferrous oxalate dihydrate with a purity of more than 98%.This study provides a method for efficient recovery of iron resources in acidic solution system.

The purification process and mechanism of hafnium metal by iodination-electron beam smelting were studied by thermodynamic analysis.The results show that when hafnium is purified by iodization, Zr and Ti cannot be separated because the binding ability of Zr, Ti and Hf to iodine is very close.When hafnium is purified by electron beam smelting, the vapor pressure of W,Nb, Zr and Ti is lower than or close to that of Hf, which makes them impossible to separate.The decomposition pressure of HfN near the melting point of Hf is very low, which is not easy to decompose and cannot be separated.In general, after metal hafnium iodination-electron beam smelting treatment, except for Zr and Ti which cannot be separated, other elements with relatively high content can be effectively separated.The actual production data further proves the correctness of the theoretical analysis of hafnium iodination-electron beam smelting purification mechanism, and Fe, Cr, Al, N,O and Si can be effectively separated from Hf.

A method for recovering rubidium and cesium was proposed from rubidium-cesium alum, a by-product of lithium extraction from lepidolite.The rubidium-cesium alum was leached with sodium hydro-xide, and the effects of sodium hydroxide concentration, liquid-solid ratio and leaching time on the leaching rate of rubidium and cesium were investigated.The results show that the leaching rate of rubidium-cesium is above 99% under the optimized leaching conditions of leaching temperature 25 ℃,NaOH solution concentration 1.5 mol/L,liquid to solid ratio 8∶1,and leaching time 40 min.Rubidium-cesium was extracted from alkaline leaching solution with t-BAMBP,and the four-stage countercurrent extraction was carried out under the conditions of temperature 25 ℃,pH=13.75,C_t-BAMBP=0.6 mol/L,O/A=1.5∶1 and extraction time 5 min.The extraction rates of rubidium and cesium are respectively over 92% and 99.9%,only 1.53% K impurity is extracted, and the elements of Li, Na, Al are not extracted.The loaded organic phase is washed and selectively stripped for rubidium and cesium, and the obtained rubidium chloride and cesium chloride solutions have purity of more than 92% and 98%,respectively.The rubidium in the washing solution is recovered and enriched, and the rubidium chloride solution with a concentration of 21 g/L and a purity of more than 98% is obtained.

Rhenium is mainly associated with copper-molybdenum ore.Rhenium enters the contaminated acid with flue gas during copper smelting.Due to the complex composition of the contaminated acid and its low rhenium content, there are few production examples of extracting and separating rhenium from copper smelting contaminated acid at present.The research progress is reviewed of extraction and separation technology of rhenium from copper smelting contaminated acid at home and abroad in recent years, and the development trend of rhenium extraction technology is prospected.

WCoB-TiC cermets were prepared by the spark plasma sintering process.The effects of SPS temperature on the microstructure and mechanical properties of WCoB-TiC were investigated.The experimental results show that the density and hardness of the cermets firstly increase and then decrease with the increase of sintering temperature.When the sintering temperature is 1300℃,the microstructure compactness of the WCoB-TiC cermet is the best,the density reaches 9.33g/cm³,and the hardness and bending strength are the highest,which are 92HRA and 824MPa,respectively.When the sintering temperature is increased from 1100°C to 1300°C,the fracture mode of the cermets gradually changes from cleavage fracture to quasi-cleavage fracture.When the sintering temperature reaches 1400℃,the grain growth leads to the decline of various mechanical properties of the cermet.

In order to improve the mechanical properties of Ni-based plasma cladding layer, single crystal WC powder was added into the Ni-based powder.The influence of adding different amounts of WC on the microstructure and mechanical properties of Ni-based plasma cladding layer was studied by SEM analysis, hardness test, wear resistance test and other methods.The results show that when 0~30% WC is added into Ni60 alloy powder, with WC addition amount increasing, the macroscopic morphology of Ni-based plasma cladding layer gradually deteriorates, and undecomposed WC particles gather more and more at the fusion line, while the surface hardness of the cladding layer shows an increasing trend, and the wear resistance is gradually improved.In actual production, it is necessary to comprehensively consider the macro-morpho-logy and property requirements of Ni-based cladding layer before reasonably determining WC addition amount.

Taking hot-pressed sintered tungsten carbide(WC)and gas carburized WC coatings as the re-search objects,their microstructure,element composition,crystal orientation,phase composition and distri-bution were characterized by in-situ SEM,EDS,EBSD,XRD and Raman spectrometer.The analysis results show that the coating cross-section contains WC,W₂C and amorphous phase.The grain size of WC main phase is about 3μm,the thickness is about 15μm,and it is hexagonal and polycrystalline.The main peak positions in Raman spectrum of WC layer are consistent with the characteristic peak positions of WC(A₁110cm^-1 and A₂166cm^-1),and the peak shape and position are consistent with those of sintered WC.WC grains grow along(101)crystal plane,showing apreferential orientation and resulting in increased intensi-ty of 75cm^-1 Raman peak,which is consistent with XRD results.The crystal structure of W₂C is hexago-nal,and there are two kinds of W₂C microstructures in the coating:Fine grains of uniform distribution are near the surface layer and the abnormally grown single crystals are near the substrate.The main Raman peak positions of W₂C area are consistent with W₂C characteristic peak positions(E_g128.5cm^-1 and A_1g 220cm^-1),and they have no interference with WC main peaks.The amorphous layer with a width of about 2μm is located between the W₂C fine-grained area and the substrate,and it contains about 2%(molar frac-tion)Fe impurity.Raman spectrum of the amorphous layer shows peakless bulge,which is well distin-guished from other phases.Raman spectrum analysis of the coating verifies the phase distribution results obtained by EBSD,and the phase composition information of the coating material cross-section is enriched.Due to the complexity of EBSD sample preparation,Raman spectrum has an irreplaceable advantage in the rapid identification of WC,W₂C and amorphous phase.

In order to improve the properties of molybdenum wire,using ammonium tetramolybdate,nitric acid,aluminum nitrate and urea as raw materials,MoO₃-Al₂O₃ precursor was prepared by hydrothermal method,and then Mo-Al₂O₃ composite powder was obtained by low temperature calcination and two-stage hydrogen reduction.Then,the Mo-Al₂O₃ molybdenum rod with a diameter of about 20mm was obtained by pressing and high temperature sintering,and finally the Mo-Al₂O₃ molybdenum wire with a diameter of 0.18mm was obtained by blanking,rotary forging,drawing,annealing and cold drawing.The effects of different Al₂O₃ doping contents on the microstructure and properties of molybdenum powder and molybde-num wire were studied,and the strengthening mechanism of molybdenum wire was analyzed.The results show that the addition of Al₂O₃ particles can refine Mo grains and improve the properties of molybdenum wire.The more the addition amount of Al₂O₃ particles,the greater the grain refinement degree of Mo-Al₂O₃,and the better the mechanical properties of molybdenum wire.The strengthening mechanism of Al₂O₃-doped molybdenum wire is dispersion strengthening,grain refinement strengthening,work harden-ing and texture strengthening,which together endow the Al₂O₃-doped molybdenum wire with ultra-high strength.Within the experimental range,the tensile strength and elongation of Mo-0.25%Al₂O₃are the highest,reaching 2243MPa and 3.9%,respectively.

In view of the excellent comprehensive properties of Al-Cu alloys,the research progress of the effects of Sc and the combined addition of Sc and other elements in Al-Cu alloys at home and abroad is re-viewed,which include the changes of grain size,phase composition and distribution,physical and mechani-cal properties of Al-Cu alloys after the addition of Sc or the combined addition of Sc and other elements.The matters needing attention and the contents needing further study in future research are analyzed and discussed.