In order to solve the problem of ununiform thermal field distribution in rare earth electrolytic cell,a three-dimensional model of 15 kA rare earth electrolytic cell was established and the distance between anode and cathode of the model was adjusted. COMSOL software was used to simulate and analyze the electrothermal fibld in the electrolytic cell with different center distance between anode and cathode,to obtain the distribution of the three-dimensional electrothermal field in the electrolytic cell. The results show that with the increase of cathode and anode center distance, the high temperature isothermal surface in the electrolytic cell constantly shift towards the center of the cell, the highest isothermal surface of the right cathode gradually narrows to fall off the anode, and the highest isothermal surface near the left cathode constantly extends and shifts towards to the cell center. The maximum current density in the electrolytic cell has no obvious change regularity with the increase of cathode and anode center distance, reaching the maximum value at the center distance of d=33 mm and meanwhile obtaining the most uniform distribution of high temperature isothermal surface. The optimal distance between anode and cathode in the electrolytic cell is 33 mm.

The effects were studied of additives on the separation of iron, rare earth and niobium from low grade rare earth-niobium-iron crude concentrate during reduction roasting. The results show that when the crude concentrate with 31.9% TFe,3.16G REO and 2.91~//00 Nb205 is processed by direct reduction roast- ing,the iron grade of magnetic material is only 54. 45% ,and the recoveries of rare earth and niobium are 44.28% and 62.65% ,respectively. The reduction roasting effect is the best when 15% Na2SO4 and 5% activated carbon powder are added,the iron grade of magnetic material in the product is 89. 32% ,the iron recovery is 91.47%, REO and Nb20s contents of the non-magnetic materials are 5. 36% and 4. 62%, and their recoveries reach 96.09% and 95.83% ,respectively. The microstructure research results indicate that in the product from reduction roasting without additives, the iron granules are fine and have no clear boundary with other minerals, the aggregation degree of most rare earth and niobium granules are low, the grains are not well-knit, and the separation is not effective. In the product from reduction roasting added with Na2SO4 and activated carbon powder,iron,rare earth and niobium granules aggregate and grow up, and boundary between iron, rare earth, niobium and other minerals is clear, which is benefit for separation.

Based on the analysis of carbonization process and carbonization mechanism, using blue tungsten oxide （WOa9） and violet tungsten oxide （WO2.72） as the raw material,the effects of carbonization temperature, carbonization time and particle size of W powder on the particle size of tungsten carbide powder were studied. The experimental results show that using WO2.72 as the raw material,the particle size of the prepared powder is smaller than that using WO2.9 as the raw material. Therefore, WO2 72 is the optimal raw material for the preparation of ultrafine tungsten carbide powder by reduction carbonization. Under the conditions of tungsten powder particle size of 0. 2-0.3 μm,carbonization temperature of 1 350 ℃,and carbonization time of 10 min/boat,the particle size of the final tungsten carbide powder is 0.4-0.5 μm,completely in accordance with the ultrafine WC powder standard.

The study was carried out on the microstructure of Nd2.28 Fe13.58B1.11 alloy with different content of rare earth La and the magnetic properties of the melt-spun ribbons. The experimental results show that the main phase of the alloy is still Nd2 Fe14 B phase after La addition. With the increase of La addition, the crystal cell volume of Nd2Fe14B phase slightly increases,both the coercivity and remanence of the meltspun ribbons decreases,and the Curie temperature also decreases.

The effect of La addition on high temperature oxidation of high carbon alloy tool steel was stud- ied. The high-temperature oxidation behavior of high carbon alloy tool steel without and with rare earth La was analyzed with thermal analyzer and weight gain method. The morphology of oxide film was observed by scanning electron microscopy. The structure of the oxide layer and its layering were analyzed by observing the cross-sectional morphology of the oxide layer. The results show that all the kinetic curves of iso- thermal oxidation at 900 ℃, 1 000 ℃, 1 100 ℃ and 1 200 ℃ of high carbon alloy tool steels with and without La are in accordance with the parabolic law,and the oxide films of the two alloy tool steels are protective. The oxidation reaction activation energy of high carbon alloy tool steel with rare earth La is 23% higher than that without La addition, and its oxidation rate constant is also lower. The adhesion of the oxide film on the high carbon alloy tool steel with rare earth La is stronger,and its oxide layer is more solid. The addition of rare earth La refines oxide film grains on high carbon alloy tool steel surface, and reduces the interspace among oxide film grains, resulting in the oxide films not easy to peel off.

Li-rich manganese-based material Li1.2[Mn0.54Ni0.13Co0.13]O2, was synthesized with co-precipitati- on and high temperature solid state method,and then coated with PrPO4 by simple wet chemical precipita- tion and PVP-assisted wet chemical deposition. The results show that with PVP-assisted coating,the coat- ing layer is more uniform,and the electrochemical properties are obviously improved. The 3 %-PVP coated sample shows an initial discharge capacity of 286.7 mA·h/g with Coulombie efficiency of 89.60~, and more excellent cycling stability with discharge specific capacity of 254 mA·h/g after 50 cycles at 0.1C discharge rate, and the capacity retention increases from 88.5% of the blank sample to 95%. Thus,it turns out that the uniform PrPO4 coating layer can effectively improve the comprehensive electrochemical performance of Li-rieh manganese-based cathode material.

Based on the general rule of gas-liquid two-phase flow,the floating and mass transfer of bottom- blown nitrogen bubbles in the Sm-Fe melt were studied. The relationship between the radius of nitrogen bubbles in liquid Sm-Fe alloy and time in the process of floatation was discussed, and the mass transfer rate was also analyzed. The results show that the radius of nitrogen bubbles in the Sm-Fe melt increases with the increase of time at atmospheric pressure, and the air pressure has a significant inhibition effect on the growth of nitrogen bubbles. At atmospheric pressure, the mass transfer rate of bubbles increases at first and then decreases with time increasing in the floating process of nitrogen bubbles. When the floating time equals to 7.8 s,the mass transfer rate reaches the maximum value of 6.2×10^-11mol/（m^3·s）. When the floating time is less than 7.8 s, the bubble radius plays a leading role in the mass transfer of bubbles. When the floating time is more than 7.8 s,the concentration of bubbles plays a leading role. Meanwhile,with the increase of air pressure the maximum mass transfer rate is reduced and the time to achieve the maximum mass transfer rate is increased.

The preparation process of Al-Sc alloy with sinking cathode in KF-AlF3-Sc2O3 molten salt system was studied. The phase composition, microstructure and micro area composition of AI-Sc alloy were analyzed by XRD and SEM. The effects were investigated of electrolysis temperature,cathode current density and molten salt proportion on electrolysis current efficiency. The experimental results show that Al-Sc alloy is composed of Al phase, Sc phase and Al3 Sc phase, and the alloy is mixed with a small amount of mol- ten salt. The distribution and morphology of Al3 Sc phase are irregular in the alloy. The optimal electrolysis process conditions are as follows：in KF-AlF3-Sc2O3 molten salt, liquid aluminum is the sinking cathode, and Sc203 is the electrolyte, with KF/AlF3 molar ratio in the molten salt of 1.3,electrolysis temperature of 800 ℃ ,electrolysis time of 25 min,and current density of 1. 592 A/cm^2. Under the above conditions,Sc content in the Al-Sc alloy is up to 6. 710% and the average current efficiency reaches 57.28%.

The effect of low-speed wire cut electrical discharge machining （WEDM-LS） on the bending strength of Ti（C,N）-based cermet of Ti（C,N）-7%WC -20%Ni-7%Mo was studied by hydraulic universal testing machine. The morphology and chemical composition of the machining surface, and the microstruc- ture of the deterioration layer were observed and analyzed by SEM and EDS. The results show that WEDM -LS causes obvious electrical erosion deterioration layer, significantly reducing the bending strength and increasing the intensity dispersion of the sample. There are a large number of microscopic defects such as micro-cracks,holes and grain shedding in microstructure of the deterioration layer.

The study was carried out on the effect of extrusion temperature on microstructure and properties of beryllium material and its texture evolution during extrusion. The results show that the crystal grains of beryllium ingot are refined after extrusion, and its tensile strength, yield strength and fracture elongation are improved in different degrees. With extrusion temperature increasing, beryllium grain size increases and （1010） fiber texture is enhanced, both affecting the mechanical properties of beryllium rods. In order to ana- lyze the relationship between mechanical properties, crystal structure and texture of extruded beryllium rods, mechanical testing was carried out with the samples obtained according to a certain slope angle along the extrusion direction. It is found that the tensile strength and yield strength significantly decrease, while the fracture elongation greatly increases. Therefore, the plasticity of beryllium material can be improved by controlling texture direction via equal channel extrusion.