CeO2-Fe2O3ultrafine powder catalyst was prepared by synergy of microwave,ultrasonic and highenergy ball milling.The catalyst was characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR)and denitration activity test.The best experimental conditions were concluded,and NH3-SCR denitration mechanism of the catalyst at low temperature was investigated.The results show that the microwave-ultrasonic synergy is beneficial to the dispersion of CeO2-Fe2O3ultrafine powder,and high-energy ball milling increases the specific surface area of the powder.When Fe/Ce molar ratio is 4∶1,CeO2-Fe2O3ultrafine powder has the best surface properties and catalytic activity.After loaded on activated alumina,the optimum denitration temperature of CeO2-Fe2O3ultrafine powder moves to the low temperature window,and its denitration activity increases by 14.4%.The NH3-SCR reaction process occurring on catalyst surface mainly follows the Eley-Rideal(E-R)mechanism.NH3is the main surface adsorbed species,and NO directly participates in the reaction in gaseous form,to finally generate N2and H2O and achieve the removal of nitrogen oxides.

Al-Sc alloy(Al-20%Sc)target material was prepared,and the influence of different annealing processes on microstructure and microhardness of the alloy target material was investigated.The results show that after the target sample is annealed,its grain shape changes from angular to rounded,grain size becomes larger,and grain boundaries are smooth.Microhardness of the sample before annealing is 70.37 HV0.1.With the increase of annealing temperature and time,alloy microhardness significantly decreases at first and then stabilizes.The optimal annealing conditions are 620℃and 60min.The target sampleannealed under the above conditions has the decreased microhardness of 55.03HV0.1,but its plasticity is improved,which is conducive to subsequent machining.

The boronization experiment was carried out on the surface of high vanadium wear resistant steel by solid powder boronization.The influence of boriding temperature on the microstructure and performance of boronized layer was studied by X-ray diffraction,scanning electron microscopy,microhardness tester and other detection methods.The results show that the boronized layer with a certain thickness and dense microstructure can be obtained after solid boronization of high vanadium wear resistant steel.The phase of boronized layer is single phase of FeB,which wedges into the matrix in the form of needle teeth,and is firmly bonded with the matrix.When boriding temperature increases from 850℃to 1000℃,the thickness of boronized layer increases from 36μm to 75μm,and the surface hardness of boronized layer increases at first and then decreases.When the boriding temperature is 950℃,the surface hardness of boronized layer reaches the maximum value of 1822HV,and its compressive strength is higher than that of 45steel and high vanadium wear resistant steel without boronization treatment.

HVAF and HVAF-laser remelting technology were applied to prepare NiCr-Cr3C2cemented carbide coatings,respectively.The phase composition,microstructure and microhardness of coatings were characterized by XRD,SEM,EDS and Vickers hardness tester,and the wear resistance and wear mechanism of the two kinds of coatings were studied respectively under the dry sliding frictional wear condition and slurry erosion wear condition.It is found that the main phases of NiCr-Cr3C2coating prepared by HVAF-laser remelting areγ-(Fe,Ni),Cr2Ni3and M7C3(M=Cr,Fe),and the metallurgical bonding is formed between coating and substrate.The microhardness of NiCr-Cr3C2coating prepared by HVAF-laser remelting increases with the decreasing laser power,and its average microhardness reaches 1092HV0.2at 1.5kW.Under dry sliding frictional wear condition,the wear mechanism of HVAF coating is abrasive wear and fatigue spalling of carbide particles,and that of HVAF-laser remelting coating is cutting and shearing.Under slurry erosion wear condition,the wear mechanism of HVAF coating is fatigue spalling,and that of HVAF-laser remelting coating is micro-cutting and local fatigue fracture.The slurry erosion resistance of HVAF-laser remelting coating is more than 3times of that of HVAF coating.Laser remelting can effectively improve the metallurgical bonding and slurry erosion resistance of NiCr-Cr3C2cemented carbide coating prepared by HVAF,but the problem of high cracking sensitivity needs further study.

The tail slag from TiCl4 refining by vanadium removal with copper powder is of complex composition,easy to hydrolyze and generate corrosive gas,which seriously pollutes the environment,and the valuable elements are difficult to recover.A new method for recovering copper and other valuable elements was studied according to the characteristics of the compounds contained in the tail slag of TiCl4 refining by vanadium removal with copper powder.It consists of chlorination in NaCl-KCl molten salt,oxidation leaching of CuCl2 with NaOCl,alkaline dechlorination with NaOH,acid leaching with H2SO4,and preparation of CuSO4 by cooling crystallization.CuSO4·5 H2O product with the quality meeting the national and industrial requirements was obtained by washing,filtering and drying of CuSO4·5 H2O crystal.The recovery rate of copper reaches 94.5%.After chlorination process,titanium and vanadium can be separated and recovered by fractional distillation from the distilled mixture of TiCl4 and VOCl3.The waste NaCl-KCl molten salt and NaOCl,which are by-products in the production of titanium sponge,are used as raw materials to reduce the production cost.The filter residue and washing water produced by this process can be reused in the process and titanium sponge production.Therefore,there is no waste generated in this process.

With the development of new energy vehicles and various electronic products,the recycling of power lithium batteries as the core component has been paid more and more attention.According to the currently adopted treatment technologies,the recovery processes of power lithium batteries are divided into dry recovery and wet recovery,and the specific used methods are summarized.The recycling value,current recycling strategy and main recycling technologies of waste lithium batteries are reviewed.At the same time,the problems to be considered in the future lithium battery recycling are further analyzed according to the market recycling system,and the potential problems in the current recycling process are analyzed and summarized.Finally,the feasibility suggestions on improving the future lithium battery industry and the market recycling system are given to expect a better development of the recycling industry.

Cr3C2-30 WC composite powders were prepared by carbothermal reduction method at 1 400 ℃ for 1 h.The phase composition and microstructure of the composite powders were characterized by XRD and SEM,and then the Cr3C2-based cermets were prepared with self-made Cr3C2-10 WC composite powders.The results show that the phase transition during synthesis reaction of Cr3C2-30 WC composite powders is mainly WO3 → WO2.9 → WO2.72 →W(W2C),Cr2O3 → Cr7C3 → Cr3C2 and W solution into Cr3C2 to form(Cr,W) C solid solution.With the carbothermal reduction temperature increases,the grain size of compo-site powders increases,and about 3~5 μm small particles agglomerate and melt to form 10~20 μm large particles at 1 400 ℃.Cr3C2-10 WC composite powders can significantly inhibit growth of the hard phase in traditional Cr3C2-20 Ni cermets.The bending strength of cermets increases from 850 N/mm2 to 1 240 N/mm2,with an increase of 45.9%.At the same time,the HV30 hardness increases from 930 MPa to 1 030 MPa,with an increase of about 10.8%.

Based on the preparation of WC/MgO cemented carbides by vacuum hot pressing sintering,WC/MgO/CeO2 composites were obtained by adding appropriate amount of rare earth additive CeO2 and changing sintering parameters,and the phase composition,microstructure densification process and mechanical properties of the composites were studied.The results show that with the increase of sintering temperature,the grains gradually grow.At 1 650 ℃,the WC average grain size is 1.674 μm,the grain edge is round,the relative density is 96.979%,Vickers hardness is 16.251 GPa and fracture toughness is 10.326 MPa·m1/2.When the temperature rises to 1 720 ℃,part of WC grains abnormally grow,the edges are more angular,and the relative density is still slightly increasing,but the mechanical properties significantly decrease.According to the average grain size data of WC at different sintering temperature for different durations,the molar activation energy required for grain growth of WC/MgO/CeO2 composites during hot pressing sintering is calculated to be 459.13 kJ/mol.Compared with WC/MgO composites,the activation energy for grain growth of WC/MgO/CeO2 composites increases,which can be attributed to the fact that CeO2 reduces the surface energy or interfacial energy of WC grains.

WC-Co composite powder prepared by spray conversion was used to prepare WC-Co wear-resis-tant coating by HVOF spraying,and then heat treatment of the coating was performed at 550 ℃,750 ℃ and 950 ℃ in N2 and vacuum atmosphere,respectively.The effects of heat treatment conditions on phase,microstructure,hardness and wear resistance of the coating were studied.The results show that the coating heat-treated in vacuum atmosphere has lower decarburization degree and porosity than the coating heat-treated in N2 atmosphere.The hardness and the wear resistance of the coating can be significantly improve through heat treatment in vacuum atmosphere.The wear rate of the coating heat-treated in vacuum at 750 ℃ can be reduced to 47% of that of the sprayed coating,and its HV0.3 hardness reaches 1 550.

Mo2NiB2 based cermets doped with different molar contents(0,0.05%,0.1%,0.15%,0.2%) of Nb were prepared by spark plasma hot pressing sintering.The microstructure and mechanical properties of the cermets were studied by scanning electron microscope and electronic universal testing machine.The results show that Mo2NiB2 based cermets are mainly composed of Mo2NiB2 hard phase and Ni based binder phase.With the addition of Nb,the hardness of the cermets increases at first and then decreases,and reaches the maximum value of 1 203.4 HV at 0.05% Nb dosage.Nb replaces part of Mo to form a replacement solid solution,resulting in solid solution strengthening effect and increased hardness value.When Nb content is 0.05%,the Mo2NiB2 based cermet has the highest bending strength of 854.93 MPa.The main fracture mode is brittle cleavage fracture,and the fracture toughness decreases with the addition of Nb.