Using La(NO3)3 and Co(NO3)2 as raw materials,rare earth perovskite LaCoO3 powder was prepared by citric acid complexation and ammonium carbonate precipitation,respectively.Products were characterized by SEM,XRD,specific surface area analyzer and laser particle size analyzer.The results show that the rare earth perovskite LaCoO3 powder can be prepared by calcination above 600℃,and the surface structure is the flocculent structure of honeycomb foam.With the increase of calcination temperature,the surface will be sintered at different degrees.The sample prepared by citric acid complexation has high purity,stronger sintering resistance and smaller particle size,the efficiency of catalytic denitrification is over 90%.

The oxide layer thickness and oxidation products during the forging process of TaW12 alloy were characterized by optical microscopy and XRD technology,and the macro-oxidation behavior were investigated.The results show that during unprotected forging,the surface of the alloy absorbs a lot of oxygen,resulting in seriously powdered surface and harden sub-surface,with the oxidation depth of about 300~400μm,and the oxidation product is Ta2O5.The oxidation of the alloy could be greatly reduced by the ladle sheath or coating protection in the forging process,which has the best coating effect and the oxidation loss is reduced within 3%.

Using Ni-6 B-53.3 Mo as basic materials,Mo2NiB2-based cermets with different La2O3 doping concentration(0%,0.3%,0.6%,0.9%,1.2%)were prepared by vacuum hot-pressed sintering at 970℃.The effects of La2O3 doping concentration on the microstructure and friction and wear properties of Mo2NiB2-based cermets were investigated by high temperature vacuum friction and wear tester,surface profiler,laser confocal microscopy and X-ray diffraction.The results show that with the increase of La2O3 content,the wear rate and friction coeffiction of Mo2NiB2-based cermets are increased first and then decreased under the same load at room temperature.The wear rate and friction coefficient of Mo2NiB2-based cermets doped with 0.3%La2O3 are the highest and doped with 1.2%La2O3 are the lowest.The effects of load on wear resistance of Mo2NiB2-based cermets is obvious,the wear rate and friction coeffiction decrease with the increase of load.As temperature increases,the wear rate of La2O3 doped Mo2NiB2-based cermets decreases first and then stabilizes gradually,and the friction coefficient decreases first and then increases.

To study the effect of annealing treatment on microstructures and hardness of Al1.5CrCuFeMnTi high entropy alloy,the as-cast alloy was prepared by vacuum arc melting,and the morphology,crystal structure,composition distribution and hardness of the alloy obtained under isothermal annealing treatment at different temperatures were characterized by using methods of X-ray diffraction,scanning electron microscope and Vickers hardness tester.The results show that the as-cast Al1.5CrCuFeMnTi alloy is composed of an ordered and a disordered solid solution with a body-centered cubic structures,which forms a typical dendritic structure,and the characteristic of modulated structure is also observed in as-cast alloy.After annealing at 945℃,a Laves phase rich in Al,Cr and Mn with complex structure is formed.After annealing at 980℃,the Laves phase is transformed into FCC solid solution with Cr as matrix.Annealing treatment is conducive to the release of residual internal stress in as-cast alloys,which reduces the hardness of the alloys to about HV450.

C/C-ZrC-SiC composites were prepared by precursor infiltration and pyrolysis using poly-meric organic zirconium precursor(POZ)and polycarbosilane(PCS)as precursor.Thermogravimetric behavior,phase conversion and microstructure of Zr-Si mixed precursors during pyrolysis were studied by thermal gravimetric analyzer,X-ray diffraction and scanning electron microscope,and the microstructure and ablation behavior of the composites were analyzed in detail.The results indicate that when Zr-Si mixed precursors is heated from room temperature to 1 200℃,ZrC precursor transforms to inorganic ZrO2.When the pyrolysis temperature rises to 1 600℃,ZrO2 can be reduced to ZrC ceramics by carbothermal reduction reaction.The transition temperature of the SiC crystal is 1 200~2 000℃.The microstructure of the C/C-ZrC-SiC composites after ablation shows that the prepared composites exhibit good ablation resistance.

Biomass-derived carbon materials are widely applied for energy storage due to their excellent properties such as renewability,low cost,good conductivity and stability.The common preparation methods of biomass-derived carbon materials(pyrolysis,activation,hydrothermal method)and the latest progress of modified biomass-derived carbon(heteroatom doping,noble metal loading)in lithium-air batteries,sodium-ion batteries and lithium-sulfur batteries were reviewed.The challenges and future development directions of biomass-derived carbon in next generation batteries were discussed.

The characteristics were introduced of three kinds of nitriding processes for preparing alloy ribbon by melt bottom blowing nitrogen,top blowing nitrogen at high pressure and non-equilibrium solidification of rare earth alloy melt,and the factors affecting nitriding effect were discussed.The problems existing in the nitriding process of rare earth alloys and the research direction in the future were prospected.

The effect of rare earth magnesium modification concentration on the structure,hardness and wear resistance of Cr26 high chromium cast iron was studied by metallographic microscope,scanning electron microscopy,Rockwell hardness tester and dynamic abrasive wear tester,and the wear mechanism was discussed through the relationship between wear amount and wear trace morphology.The results show that the addition of rare earth magnesium changes the formation and growth environment of carbides,the morphology of carbides changes from long sheet and strip distribution to lump and nearly spherical distribution,and reduces the degree of matrix splitting.When the addition amount of rare earth magnesium reaches 0.6%,the microstructure and the distribution of carbides reaches its optimal state.The main role of rare earth is to purify the alloy liquid,refine the as-cast structure of the alloy,and the main role of magnesium is to deoxidize,desulfurize,purify the molten iron and reduce inclusions.The morphology of wear marks is mainly plough grooves,curls,pits and a small number of microcracks.The main wear mechanisms are cutting wear,multiple plastic deformation and chisel wear.

Sr2MgSi2O7∶Eu2+,Dy3+,Yb3+long afterglow phosphors were prepared via high-temperature solid state reaction.Microstructure and optical properties of Sr2MgSi2O7∶Eu2+,Dy3+,Yb3+long afterglow phosphors were characterized through XRD,SEM,excitation spectrum,emission spectrum and decay curves.The results show that the crystal structure and microstructure of Sr2MgSi2O7∶Eu2+,Dy3+,Yb3+have not changed significantly.The addition of Yb3+ions shows a remarkable change in fluorescent properties and afterglow performance.The introduction of Yb3+makes Sr2MgSi2O7∶Eu2+,Dy3+,Yb3+have better fluorescence performance and afterglow properties.Different Yb3+doping amounts have a significant effect on the trap depth and electron transport rate of the long afterglow phosphors.When the doping amount of Yb3+equals to 0.03,experiments show that the Sr2MgSi2O7∶Eu2+,Dy3+,Yb3+has the strongest fluorescence intensity and the best afterglow attenuation performance.

Lithium-oxygen batteries,as a new type of battery system with ultra-high theoretical specific energy density,have good application prospects in the field of electric vehicles.Reduced graphene oxide was prepared by modified Hummers method and thermal expansion method,and different noble metals Ru,Ir,Au and Ag were loaded by impregnation reduction method,and the effect of graphene catalysts with different noble metals on the performance of lithium-oxygen batteries were studied.The results show that the reversibility and charge-discharge cycle stability of lithium-oxygen batteries with Ru/RGO and Ir/RGO catalysts with high catalytic activity for oxygen precipitation are better than those of lithium-oxygen batteries with Ag/RGO and Au/RGO catalysts.