Using tungsten trioxide, magnesium powder and diluents as raw materials, tungsten powder was prepared by self-propagating high temperature synthesis method.The influence of diluent types on the properties of tungsten powder in different raw material states was studied, and the determination of the best reaction diluent and process improvement for the preparation of tungsten powder by self-propagating high temperature synthesis were further explored.The experimental results show that elemental tungsten powder can be obtained regardless of whether the reactants are in powder state or pressed state, and the particle size of tungsten powder prepared in powder state is smaller.Different types of diluents have a significant effect on the morphology of the product tungsten powder.Using MgO as the diluent, the particles of the product tungsten powder is relatively larger and the distribution is relatively uneven.Using K₂CO₃,Na₂CO₃and Li₂CO₃as the diluent, the particle size of the obtained tungsten powder is un-even and increases in turn.NaCl is the best diluent for the preparation of tungsten powder by self-propagating high temperature synthesis method, the morphology of the obtained tungsten powder is the best, and the overall particle size of tungsten powder is less than 200 nm.

The NiMoO₄@NiMn₂O₄ composite electrode material based on nickel foam was successfully prepared by two-step hydrothermal method.The phase composition and microstructure of the electrode material were studied by X-ray diffractometer(XRD)and scanning electron microscope(SEM).The electrochemical performance of the electrode material was tested by cyclic voltammetry(CV),galvanostatic charge-discharge(GCD)and electrochemical impedance spectroscopy(EIS).The results show that the velvet-like NiMn₂O₄is attached to the nanowire-like NiMoO₄,which increases the specific surface area and the specific capacitance of the electrode material.At the current density of 1 mA/cm²,the specific capacitances of NiMoO₄ and NiMoO₄@NiMn₂O₄ are 240 mF/cm²and 2120 mF/cm²,respectively.Compared with the single NiMoO;electrode material,the NiMoO₄@NiMn₂O₄composite electrode material exhibits more excellent electrochemical performance due to the dual optimization of composition and structure.

Bayan Obo bastnaesite was selected as the research object,and according to its Ce/La mass ratio,(Ce,La)CO₃F crystal grains were synthesized by hydrothermal method to study their NH₃-SCR denitration performance.The results show that(Ce,La)CO₃F synthesized by adding excess NaHCO₃has better catalytic effect.After roasted at 500℃,the(Ce,La)CO₃F grains have the best denitration effect,and the NO_x conversion rate is 34%at the catalytic reaction temperature of 200℃.The combined action of Mn-Fe loading and sulfuric acid acidification can excite the active components of(Ce,La)CO₃F catalyst.After the catalyst with the combined action is roasted at 400℃,the NO_x conversion rate of 93%is obtained at the catalytic reaction temperature of 250℃.The reaction mechanism of(Ce,La)CO₃F catalyst was explored by in-situ infrared technology.The results show that the surface reaction of Mn-Fe loaded and sulfuric acid acidified(Ce,La)CO₃F catalyst mainly follows the E-R mechanism.The reactive species are NH⁺₄/NH₃(a)generated by NH₃(g)adsorption on the catalyst surface and NO,which undergo a series of intermediate reactions to produce N₂ and H₂O.This study can provide theoretical guidance for the use of rare earth concentrates as denitration catalysts.

The chemical reforming hydrogen production method has the advantages of easy availability of raw materials,low energy consumption,and high cost-effectiveness.However,its stable and efficient catalytic system is not yet perfect,and using rare earths to modify reforming hydrogen production catalysts has a good effect.From the perspectives of chemistry and energy,the research progress of reforming hydrogen production catalytic systems modified by rare earths at home and abroad is reviewed and commented.The effects of modification of reforming hydrogen production catalysts and their carriers respectively by La,Ce and Pr three commonly used rare earths on improvement of hydrogen production performance are emphatically expounded,and the mechanism of rare earth modification is analyzed.Combined with the current research trend that catalyst modification focuses on composite carrier modification,promoter modification and synthesis process optimization,the in-depth research direction of rare earth modified reforming hydrogen production catalysts in the future is proposed.

Ta-2.5 W alloy was subjected to room temperature compression and annealing, and the influence of deformation degree and annealing process on the microstructure and mechanical properties of the alloy was investigated by scanning electron microscope and microhardness tester.The experimental results show that when the annealing process is the same(1 350 ℃× 60 min),with alloy deformation degree increa-sing, the recrystallization degree increases, and the grains gradually become more uniform and finer.When the cold deformation degree of Ta-2.5 W alloy is 70%,in the temperature range of 1 200~1 350 ℃ for the holding time of 5~60 min, both increasing the temperature and prolonging the holding time are beneficial to obtain fine grains, and the average grain size of Ta-2.5 W alloy can be finally refined from the original 90 μm to 32 μm.

Zr-1 Nb-0.1 Fe-0.1 Cu plate samples with a thickness of 1.4 mm were prepared with sponge zirconium by electrode pressing,vacuum consumable arc melting,forging,homogenization treatment,quenching,hot rolling,multi-pass cold rolling and annealing.The metallographic microstructure of Zr-1 Nb-0.1 Fe-0.1 Cu alloy and the composition,size,structure and distribution of the second phase were analyzed by OM,SEM and TEM.The test results show that the metallographic microstructure of Zr-1 Nb-0.1 Fe-0.1 Cu alloy annealed at 580℃for 2 h is basically recrystallized equiaxed crystal,the grain size grade is 13,and the average grain size is less than 6μm.Elliptical second-phase particles are precipitated and dispersed in the grains and grain boundary of the alloy.More than 95%of the second-phase particles have smaller size than 200 nm.There are three kinds of second-phase particles in Zr-1 Nb-0.1 Fe-0.1 Cu alloy,includingβ-Nb precipitate with a large content,a grain size of less than 100 nm,and bcc structure,(Zr,Nb)₂Fe precipitate with a less content,a grain size of less than 200 nm,and hcp structure,and Zr;Cu precipitate with the least content,a greater grain size than 200 nm,and tetragonal structure.

Ti-bearing blast furnace slag contains TiO₂ and can be used to prepare photocatalysts to realize comprehensive utilization of Ti-bearing blast furnace slag without titanium extraction.Ni-doped photocatalysts were prepared with Ti-bearing blast furnace slag as raw material via a liquid-phase method followed by calcination.The catalysts were characterized by SEM and XRD.The influences of calcination temperature, Ni doping amount and calcination time of the catalysts on the degradation rate of methylene blue solution(the simulated pollutant) were investigated by ultraviolet light irradiation.Under the optimized conditions of calcination temperature of 500 ℃,Ni doping amount of 2% Ti mass, and calcination time of 2 h, the degradation rate of methylene blue caused by the prepared Ni-doped photocatalyst reaches 80.0%,which is 26.0% higher than that caused by the undoped blast furnace slag.

Be-16%Ti,Be-24%Ti and Be-30.8%Ti alloys were prepared by arc melting and suction casting.The phase composition,microstructure and microhardness of the alloys were analyzed.The results show that Be-16%Ti and Be-24%Ti alloys are composed of Be phase and Be₁₂Ti phase,and Be-30.8%Ti alloy contains Be₁₂Ti phase in addition to Be phase and Be₁₂Ti phase.With the increase of solidification rate du-ring suction casting,the grain size of Be-30.8%Ti alloy casting gradually decreases.The primary dendrite spacing ofφ8 mm Be-30.8%Ti alloy casting is up to 40μm,while the primary dendrite spacing ofφ4 mm casting is about 10μm.With the increase of Ti content,the hardness of Be-Ti alloys obviously increases,and the microhardness of Be-30.8%Ti alloy can reach 950 HV.

Using cobalt sulfate as raw material and sodium borohydride as nucleating agent,cobalt powder was prepared by high-pressure hydrogen reduction at 200℃.The results show that the prepared cobalt powder is spherical with uniform particle size distribution and excellent dispersibility.High-pressure hydrogen reduction can prepare cobalt powder with a single particle size of 0.2~3.5μm,and its composition meets the requirements of a foreign company for the composition of cobalt powder.

Industrial cobalt carbonate was used as raw material and calcined to form cobalt tetroxide with different carbon contents in a muffle furnace.Then the cobalt oxide was reduced to cobalt powder through a single-tube test furnace.The powders were characterized by Fisher particle size analyzer, laser particle size analyzer, oxygen content meter, carbon and sulfur meter, scanning electron microscope and other equipments.The results show that cobalt tetroxide with carbon content of 0.033%~0.195% can be obtained by adjusting the calcination process.As the carbon content of cobalt tetroxide increases, the particle size of cobalt powder gradually increases.When the carbon content of cobalt tetroxide is 0.033%,Fsss particle size of the cobalt powder is 0.94 μm, and when the carbon content of cobalt tetroxide is 0.195%,Fsss particle size of the cobalt powder is 1.13 μm, increased by 20%.With the increase of carbon content of cobalt tetroxide, the porosity of cobalt powder slightly increases, the bulk density has an increasing trend, the oxygen content is small, and the carbon content has no significant fluctuation.The gas flow classification process of cobalt tetroxide can reduce the particle size of the reduced cobalt powder.The surface of the cobalt powder reduced from high-carbon cobalt tetroxide is smoother and the sphericity is slightly worse.