The effects of adding the refiner Na2SO4 in the stirring sodium reduction process during capacitor tantalum powder preparation on the particle size of the intermediate product washed powder and the particle size and electrical properties of the final product FTB-48 tantalum powder were studied.The experimental results indicate that the particle sizes of the washed powder and FTB-48 tantalum powder prepared by adding the refiner Na2SO4 were reduced,and the sintering shrinkage and weight specific capacitance of FTB-48 tantalum powder were improved to some extent.The intermediate product washed powder will agglomerate and sinter during the high-temperature heat treatment,which causes the particle size of FTB-48 tantalum powder product to increase.

X-ray fluorescence spectrometer(XRF),X-ray diffractometer(XRD) and scanning electron microscopy(SEM) were used to characterize the rare earth tailings.It is found that there are many elements in the tailings,and the relationship among minerals is complex.According to the characteristics of rare earth tailings,the catalytic denitrification performance of rare earth tailings was tested in a vertical tube furnace.The results show that NO conversion rate increases with the increase of reaction temperature and gas residence time,and NO conversion rate in fixed bed reactor is higher than that in bubbling bed reactor.When the reaction temperature is 800 ℃,NO conversion rate reaches 98.7%.The denitration catalyst was prepared by grinding and roasting with pseudo-boehmite and rare earth tailings as raw materials.When the total amount of rare earth tailings remains unchanged,the NO conversion rate increases with the increase of pseudo-boehmite mass.When the reaction temperature is 600 ℃,the NO conversion rate of the catalyst with the mass ratio of pseudo-boehmite to rare earth tailings of 1∶2 is 15% higher than that of the pure rare earth tailings.The thermodynamic calculation proves that the rare earth tailings with high iron content is feasible for CO reduction denitrification.

In order to study the effect of annealing time on structure and gaseous hydrogen absorption and desorption properties of LaMgNi3.9Mn0.2 alloy,the phase and microstructure of the alloy were tested by XRD and SEM,and the hydrogen absorption and desorption kinetics plot was tested by semi-automatic Siever′s method.The experimental results show that with the increase of annealing time,the content of main phase LaMg(NiMn)4 decreases,while the content of(La,Mg)(NiMn)5 increases.The surface of as-cast and annealed alloys is mainly composed of columnar crystals with different sizes,which has obvious structural heredity.With the increase of annealing time,the content differences of La,Mg and Ni in the columnar crystal region of the alloy decrease,which makes the element distribution more uniform.Mn element disappears in the columnar crystal intergranular region of the alloy annealed for 15 h and 20 h.After the first hydrogen absorption of as-cast and annealed alloys,the corresponding maximum hydrogen absorption is reached.Therefore,the annealing time has no effect on the activation performance of the alloy,but has a significant effect on the maximum hydrogen absorption and the saturated hydrogen absorption and desorption of the alloy.With the increase of annealing time,the maximum hydrogen absorption and saturated hydrogen absorption and desorption of the alloy decrease,but the hydrogen absorption and desorption saturation increases firstly and then decreases,and that of the alloy annealed for 15 h is relatively high.

Sm-Fe alloy was prepared by induction smelting.The effects of smelting pressure and times on Sm volatilization during smelting and the Sm content,phase composition and microstructure evolution of Sm-Fe alloy at smelting end were studied by XRD,SEM and XRF.The optimum raw material state and Sm compensation amount were determined.The results show that the phase distribution of Sm-Fe alloy is more uniform and stable after multiple smelting.However,Sm-Fe alloy should not be smelted for too many times to avoid excessive volatilization of Sm,and three smelting times are enough.The higher the smelting pressure,the lower the Sm volatilization.Higher melting pressure can also inhibit the growth of the internal structure of the alloy.Using uniform and stable Sm-Fe alloy as the raw material of smelting is more conducive to suppressing the evaporation of Sm in the smelting process.Excessive Sm compensation cannot stabilize the Sm content of Sm-Fe alloy at smelting end.Generally,4% pure samarium compensation amount can be selected for induction smelting.

Lattice structure and intrinsic magnetic property principle of Sm2Fe17N3 interstitial compound are briefly analyzed.The current preparation methods of Sm2Fe17N3 permanent magnetic material and the influence of element addition on its magnetic properties are mainly introduced.Besides,the preparation status of Sm2Fe17N3/α-Fe dual-phase nanocomposites is reviewed.Finally,the existing problems in preparation process and development tendency of Sm2Fe17N3 permanent magnetic material are summarized and prospected.

TiO2 flexible electrode materials were prepared by hydrothermal adjustment of NaOH concentration,hydrothermal reaction time and reaction temperature.The optimal conditions of hydrothermal synthesis are NaOH solution concentration of 0.5 mol/L,reaction temperature of 200 ℃,and reaction time of 16 h.TiO2 prepared under the conditions has a porous network structure,which can enhance the electrolyte infiltration,shorten the Li+ diffusion path,and accelerate the transport of lithium ions and electrons.Constant current charging performance test results show that TiO2 with porous network structure has good cycle stability.The reversible capacity is 112 mA·h/g and the capacity retention rate is 67.8% after 50 cycles at the current density of 800 mA/g.The TiO2 also has an excellent rate performance.When the current density is as high as 1 600 mA/g,the reversible capacity can still be maintained at 103.4 mA·h/g.

Ti(C5N5),Mo2C,Ru and Ni powders were mixed,and then Ti(C,N)-based cermets were prepared by powder metallurgy.The effects of Ru on microstructure and properties of Ti(C,N)-based cermets were studied as well as the mechanism.The results show that the Ti(C,N)-based cermets doped with Ru exhibit a core-ring structure.With the increase of Ru content,the main grains are refined,and the binder phase tends to be uniform.The change in Ru content has an effect on the concentration gradient of the binder phase in Ti(C,N)-based cermets.The thickness of the gradient layer increases at first and then decreases as the Ru content increases.Ti(C,N)-based cermet with 1.5% Ru has fracture toughness of 9.9 MPa·m1/2 and Vickers hardness of 1 500 HV10.Ru doping greatly improves the comprehensive mechanical properties of Ti(C,N)-based cermets,due to strengthening of the binder phase.

The recent research progress of the methods such as self-toughening,particle toughening and whisker toughening adopted to improve the toughness of Ti(C,N)-based cermets and their comprehensive properties is reviewed.The related toughening mechanism is expounded,and the problems existing in toughening technologies of cermet materials and their future development directions are briefly described.

Ag-10 SnO2-Bi2O3 Contact materials with different Bi2O3 content were prepared by repressing and resintering process.The microstructure,density,hardness,electrical resistivity,electrochemical and arc erosion resistance were tested and analyzed.The results show that with the increase of Bi2O3 content,the hardness and chemical erosion resistance of Ag-10 SnO2-Bi2O3 contact materials increase and the conductivity decreases.The arc erosion area of the contact is closely related to the number of erosion holes.The increase of the number of holes will lead to the decrease of contact strength,expand the contact area between the matched contacts,and then expand the arc erosion area.When 1% Bi2O3 is added,arc erosion area and splashing area of the contact is the smallest,the number of holes is the least,and the contact performance is excellent.

Using WC-Co powder recycled by zinc melting method as raw material,the regenerated YG8 cemented carbides with different content of Y2O3 and Nd2O3were prepared through conventional cemented carbide production process,and their density,hardness,bending strength and fracture morphology were detected and analyzed to investigate the strengthening mechanism of rare earth oxide for cemented carbides.The results show that the cobalt magnetization value of the cemented carbide added with Y2O3 increases,while that of the cemented carbide added with Nd2O3 decreases.The effect of Y2O3 and Nd2O3 on the density and hardness of cemented carbides is not significant.When the amount of Y2O3 and Nd2O3 is 0.5%,the hardness reaches the maximum,which is 89.5 HRA and 89.3 HRA,respectively.The bending strength is improved significantly with the increase of rare earth oxide content.The bending strength of the cemented carbides with 0.7% Y2O3 and 0.7% Nd2O3 is 2 200 MPa and 2 102.8 MPa,increased by 22.2% and 16.8% compared with the regenerated YG8 cemented carbide without rare earth oxide.The proportion of fine grains in the cemented carbide added with Y2O3 is larger,the coarse WC grains are refined to a greater degree and the distribution is more uniform,and the dimple morphology is more obvious and more concentrated.