In order to explore the mechanism of oxidation leaching of stone coal,the vanadium was leached directly from stone coal vanadium ore by sulfuric acid solution at atmospheric pressure.By adding sodium persulfate in the process of acid leaching,the effects of various conditions on vanadium leaching rate were investigated.The results show that V leaching rate reached 88.9% under the experimental conditions of sodium persulfate 2% ,sulfuric acid 35 %,solid-liquid ratio 1:1,leaching temperature 95℃ and leaching time 11 h.Fitting the V leaching rate-time curves at different reaction temperatures shows that the oxidation leaching process conforms to the shrinking core model and the leaching process is controlled by the chemical reaction on the particle surface.According to Arrhenius equation,the apparent activation energy of the reaction was approximately calculated to be 66.08 kJ ·mol^-1 by using curve fitting method.

The extraction and enrichment technologies of gallium in hydrochloric acid system were emphatically introduced,mainly including extraction,adsorption and molecular imprinting methods.The technical characteristics of the gallium extraction methods in hydrochloric acid system were analyzed.Finally,the problems and research and development directions of gallium extraction technology were pointed out,and reasonable suggestions were also proposed.

The morphology of scandium oxalate crystal was controlled b'y changing the conditions of precipitation and crystallization when adding sodium oxalate to scandium chloride solution by liquid precipitation method.The effects of solution pH,feeding method,scandium concentration,surfactant and aging time on the morphology of scandium oxalate and its mechanism were investigated.The results show that many kinds of scandium oxalate crystals,such as hexagonal sheet and thick sheet,spherical,bipyramidal and layered stacking,can be prepared by controlling different experimentaI conditions,which can promote the research and application of scandium-containing powder materials.

Small size and high total cerium carbonate with the total >70 % and the particle size D50<15 μm was prepared by one-step precipitation using ammonium bicarbonate as precipitant.By using laser particle size analyzer,scanning electron microscope and EDTA titration methods,the effects of cerium chloride concentration,molar ratio of ammonium bicarbonate to cerium chloride,reaction temperature and pH value on the particle size and total of cerium carbonate were investigated.The results show that under the condition of cerium chloride concentration of 0.6~0.8 mol/L,molar ratio of ammonium bicarbonate to cerium chloride of 4 :1,reaction temperature of 80℃ and pH of 4,the precipitated cerium carbonate achieving good crystalline form,with particle size D50~15 μm and total >72M can be obtained.

接北京大学图书馆《中文核心期刊要目总览》2017版编委会通知,由中国有色金属学会和长沙有色冶金设计研究院有限公司共同主办、长沙有色冶金设计研究院有限公司主管的《稀有金属与硬质合金》期刊入编《中文核心期刊要目总览》2017年版(即第8版)之冶金工业类核心期刊。这是本刊自2008年起连续第4次入编《中文核心期刊要目总览》。

Nano TiC reinforced Ti-matrix composite powder was prepared by mechanical alloying.The phase,morphology,crystal structure and element distribution of the powder were characterized by XRD, SEM,TEM and EDS.The effects of milling speed,ball-to-powder mass ratio and milling time on phase and morphology of the composite powder were investigated.The results show that milling efficiency has no significant difference when milling speed reaches 300 r/min or higher,and ball-to-powder mass ratio reaches 20 :1 or higher.TiC phase in the powder is obvious when milling time reaches 10 h,and nano TiC reinforcement phase is obtained when milling time is extended to 20 h.Under the conditions of 300 r/min milling speed,20 :1 ball-to-powder mass ratio and 20 h milling time,nano TiC reinforced Ti-matrix composite powder can be obtained,and part of the powder is amorphous,where a large number of nano TiC particles are dispersed.

A new type of Ag-Ti2AlN electrical contact materials were prepared by high energy ball milling and powder metallurgy.The arc erosion behavior and mechanism of the contact materials were studied.The surface microstructure of the contact after arc erosion was analyzed by scanning electron microscopy.The results show that Ti2AlN reinforcement has obvious advantages in improving the arc time,arc energy and welding resistance of Ag-matrix electrical contact materials.The average arc time,arc energy and welding strength of Ag-Ti2AlN contacts are 5.61 ms,59.8 mJ and 15 cN respectively in 70 000 on-off cycle tests. Under the action of vapor arc,the corrosion pit centers such as lava and sweat droplets are formed in the cathode of electric contacts.The Ti2 AlN reinforcement particles are fused into the silver melting pool by the diffusion of titanium and aluminum,which can improve the viscosity of the melt,and then enhance the arc erosion resistance.In addition,because of the preferential oxidation mechanism of Al element,the formed Al2O3 absorbs a lot of heat during vaporization,which reduces the mass gain of the anode and the height of the anode bulge,and effectively improves the reliability of electrical contact materials.

HAP seeds were constructed on Ti substrate by biomimetic preset crystal seeds method to provide nucleation points for the formation of HAP coating,and then HAP coating was obtained by electrodeposition at low temperature.The microstructures of HAP coating prepared by electrodeposition with biomimetic preset crystal seeds were studied by scanning electron microscopy,X-ray diffraction,infrared spectroscopy and Raman spectroscopy,and the cytotoxicity of HAP coating was tested by MTT method.The results show that the surface morphology of HAP coatings prepared by electrodeposition changed from three-dimensional network structure to honeycomb structure as the time of biomimetic preset crystal seeds prolonged from 24 h to 48 h.Compared with the HAP coating prepared by electrodeposition without seeds, the HAP coating prepared by electrodeposition after presetting crystal seeds is more uniform and corn,pact, 3 and has higher bonding strength with the matrix,also is more conducive to the proliferation,metabolism and growth of osteoblasts.

Thermal compression experiments were conducted on Ti-B25 alloy with Gleeble 3800 thermodynamic simulator.The true stress-true strain data were obtained under the conditions of 800-1 000 ℃ and strain rate of 0.01-10 s^-1.By calculating the strain rate sensitive index m,energy dissipation rate η and instability coefficient ζ,the processing maps under different true strain conditions were drawn,and the stable deformation parameters and instability regions corresponding to the true strain were identified.The safe deformation parameters of Ti-B25 titanium alloy in the experimental range were obtained as follows:temperature 900-1 000 ℃ ,strain rate 0.01-0.2 s^-1.In addition,the microstructural analysis shows that the instability modes of Ti-B25 titanium alloy at low temperature and high strain rate are grain breakage and obvious rheological instability.The a phase spheroidization occurs in its two-phase structure at low temperature and low strain rate.While the instability modes at medium temperature and high strain rate are local plastic deformation in the middle large deformation zone,and the dynamic recrystallization occurs mainly at the medium temperature and low strain rates.

Using Bi2Te3 powder as raw material,TeO2 micro-nanostructures were successfully prepared by thermal evaporation.The morphology of the synthesized products was characterized by scanning electron microscopy (SEM).The results illustrate that the miero-nanostructures of the synthesized products are flower-like clusters formed by stacking a large number of micro-nanosheets.It was found by EDS that the sample consisted of two elements of Te and O.The Raman spectra of synthesized products were characterized by eonfocal laser Raman spectroscopy.The results show that the spectra of the synthesized products are consistent with those of TeO2 crystals.Also with the increase of thermal evaporation temperature,the higher the intensity of the Raman peak is,the sharper the characteristic peak is,and the better the crystallinity of the product prepared on Si substrate is.