The Bayan Obo rare earth concentrate was used as the active components of the catalyst. The elements in the ore are extracted by nitric acid with hydrothermal method, and then loaded on the activated carbon treated with nitric acid. High-temperature calcination was followed to obtain rare earth-based com- posite catalyst for selective catalytic reduction of NO with NHa as the reductant at 100-350 ℃. The effects of hydrothermal temperature and nitric acid concentration on acid leaching of rare earth concentrate were investigated as well as the effects of nitric acid concentration and calcination temperature on denitra- tion performance of the prepared catalyst. The phase, morphology and composition of the catalyst were also characterized. The results show that the optimal hydrothermal reaction temperature is 180 ℃. The higher the concentration of nitric acid, the higher the digestion rate of rare earth concentrate. The catalyst pre- pared by 15 mol/L nitric acid digestion and 600 ℃ calcination has the best denitration performance with de- nitration rate of more than 90% at 250-300 ℃. Due to the presence of amorphous active material and the formation of composite metal oxide,the catalyst has a high denitration activity.

Ultraprecise rare earth polishing powder was prepared by low temperature decomposition of waste rare earth polishing powder with commercially available inorganic acid. The effects were investigated of type and dosage of inorganic acids, reaction temperature and time, and leaching times on rare earth leac- hing. The particle size and chemical composition of the prepared rare earth polishing powder were deter- mined, and the reaction mechanism during the preparation process was analyzed. The results indicate that the rare earth leaching rate is up to 99.23 % after two-stage leaching of waste rare earth polishing powder with hydrochloric acid under the following conditions, hydrochloric acid concentration of 37% ,acid/mate- rial mass ratio of 3.5 ,reaction temperature 98-103 ℃,primary leaching for 8 h,and secondary leaching for 7 h. Ultraprecise rare earth polishing powder containing 67.64% CeO2,24.39% La2 03 and 6.00% F can be prepared,and its particle size distribution is uniform with average particle size of 0.39 μm.

The dehydration process of LaCl3 · 7H2 O at different heating rates in different atmospheres was studied by thermal analyzer. The results show that the dehydration process at 10 ℃/min heating rate in air atmosphere is divided into three stages：42.0-119.2 ℃ ,119.2-174.7 ℃ and 174.7-218.4 ℃ with crys- tal water loss of 2 molecules,4 molecules and 1 molecule,respectively. The dehydration process at 10 ℃/ min heating rate in CO2 atmosphere is also divided into three stages：38.3-109.9 ℃ ,109.9-161.2 ℃ and 161.2-196.2 ℃ with crystal water loss of 3 molecules,3 molecules and 1 molecule,respectively. Both rap- id temperature rise and increased oxidation of the reaction atmosphere are beneficial to the dehydration process of LaCl3 · 7H2O.

The effects of finishing annealing temperature on microstructure and texture of Zr-Nb alloy bars were studied by observation of metallographie microstrueture and the second phase particles and texture analysis. The results show that with the increased finishing annealing temperature, the grain size of the metallographic microstructure of Zr-Nb alloy bars gradually increases, and both the average size and size distribution range of the second phase particles gradually increase. There is {0002} basal texture in all the Zr-Nb bars annealed at various temperatures,but their texture intensity difference is relatively obvious.

Ni-Co/ZrO2 composite coatings were prepared by co-deposition technology in acid sulfamate solu-tion. The effects of nanopartieles in Ni-Co/ZrO2 composite system on its electrochemical reaction process were studied by cathode linear scan test. The surface morphology and mierostructure of the composite coat-ings were analyzed by SEM and XRD. The corrosion resistance of the composite coatings was tested by Tafel curves and their thermal stability was characterized by microhardness test after annealing. The exper-imental results show that Ni-Co/ZrO2 co-deposition potential is about --0.90 V. Compared with Ni-Co al-loy,Ni-Co/ZrO2 composite coating surface is more uniform and compact,the grains are smaller,and its cor- rosion resistance and thermal stability are better.

Using Ag-SnO2-In2O3 electrical contact materials prepared with and without ball milling as the research object,the effects were systematically studied of different high-energy ball milling parameters on the properties of Ag-SnO2-In2O3 by comparative study of macroscopic performance and mierostructure and means of XRD, OA, SEM and EDS. The results show that Ag-SnO2-In2O3 powder has broken surface oxide film due to impact, friction, shearing and compression during ball milling, and its surface with high Ag con- tent is exposed, resulting in increased Ag-Ag contact area during sintering and significantly improved densi- fieation degree,bending strength and other mechanical properties of the sintered billet. The optimized ball milling parameters are as follows： ball milling speed of 300 r/min,ball milling time of 30 min and ball to powder weight ratio of 10 ： 1.

The corrosion behavior was investigated in simulated coastal industrial atmosphere of Al-Mg al- loy,Al-Mg-Mn alloy. Al-Cu-Mg-Mn alloy and Ag-plated Al alloy used in substation equipment. The corro- sion behavior of the alloys was analyzed with weightlessness method,SEM, EDS and electrochemical analy- sis. The results show that pitting corrosion is the main corrosion method of experimental alloys in the ini- tial stage of corrosion, and the corrosion process will be slowed down with the accumulation of corrosion products. Al-Mg alloy has the best corrosion resistance, and Al-Cu-Mg-Mn alloy has the worst corrosion re- sistance. After Ag plating, the corrosion rate of Al-Cu-Mg-Mn alloy significantly decreases, and its corro- sion resistance is greatly improved. Ag coating is a cathode coating with respect to Al substrate,and the corrosion rate of the alloy is rapidly increased when the coating is damaged by corrosion.

Mixing Uniformity of tungsten powders and carbon black after carbon blending for tungsten pow- ders with different particle morphology in the same equipment was studied as well as the quality of subse- quent tungsten carbide powders. The results show that the particle morphology of tungsten powders has a great effect on the uniformity of the W＋C mixture after carbon blending. The tungsten powder with dis- perse particles is more uniformly mixed with carbon black,and the produced tungsten carbide powder has a lower content of free carbon and W2C.

Using rod-shaped and needle-shaped violet tungsten oxides as raw materials, ultra-fine tungsten powders and ultra-fine tungsten carbide powders were prepared. The effects of rod-shaped and needle- shaped violet tungsten oxides on particle size of ultra-fine tungsten carbide powders were studied by using scanning electron microscope,specific surface meter,laser particle size distribution analyzer and X-ray dif- fractometer. The results show that high-quality ultra-fine tungsten carbide powder with finer particle size can be prepared by using needle-shaped violet tungsten oxide as the raw material.

The forming processes of molding, cold isostatic pressing and molding ＋ cold isostatic pressing were adopted for the preparation of WC-6Ni cemented carbides. The effects of different forming processes on the phase composition,physical properties and microstructure of WC-6Ni cemented carbides were main- ly discussed. The results show that the WC-6Ni fine grained cemented carbide with density of 98 % arid HV hardness of 1 457 can be obtained by sintering at 1 410 ℃ for 1 h of the WC-6Ni compact from molding ＋ cold isostatic pressing. The above cemented carbide has uniformly distributed microstructure,and there are no voids and defects such as Ni pools on its surface.