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.

V-Mo/Ti and V-Mo-Nb/Ti denitration catalysts were prepared,and the denitration activity and resistance to Na poisoning of the two catalysts were investigated and compared.XRD,BET,NH3-TPD,H2-TPR and XPS were used to characterize the catalysts.The results show that the addition of Nb can effectively inhibit the decrease in acidity and reducibility of the catalyst caused by Na poisoning,and the decrease of chemisorbed oxygen on surface of the Na-poisoned catalyst.Thus,V-Mo-Nb/Ti-Na catalyst exhibits better denitration activity than V-Mo/Ti-Na catalyst.

La0.5Sr0.5CoO3 samples were prepared by solid-state reaction.The structure of the samples was analyzed by X-ray diffractometer and Raman spectrometer.XRD results indicate that La0.5Sr0.5CoO3 samples are of single-phase cubic perovskite structure.In the Raman spectrum,the peak caused by the rotation of oxygen octahedron and the secondary Raman peak formed by the vibration of Co—O bond angle and length can be observed.The energy band,density of states and partial density of states of La0.5Sr0.5CoO3 are calculated by the first-principles method.The results show that the conductivity of non-conductive pe-rovskite oxide LaCoO3 can be changed by doping Sr2+,which has guiding significance for the study of conductivity of perovskite oxide LaCoO3.

Single-host white-emitting Gd3PO7∶Dy^3+ phosphor was synthesized by wet chemical method.The phase structure,morphologies and optical properties of the as-prepared samples were characterized by X-ray powder diffraction(XRD),scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FT-IR),and fluorescence spectroscopy.The XRD results show that the samples are Dy^3+ doped Gd3PO7 crystals with monoclinic structure and slight impurity.The fluorescence spectra show that under the excitation with the characteristic excitation band of Gd^3+ ions at 276 nm,Gd3PO7∶Dy^3+ samples emit the characteristic emission bands of Dy^3+ ions in yellow light region(4F9/2→6H13/2) and blue light region(4F9/2→6H15/2),which indicates that the energy transfer from Gd^3+ to Dy^3+ occurs in the Gd3PO7∶Dy^3+matrix.The luminescence intensity of the samples depends on pH values and Dy^3+ dosage.When the pH value is 6.00 and the Dy^3+ dosage is 0.5%,the sample exhibits a relatively high luminescence intensity.The Dy^3+ dosage directly affects the luminescence color of Gd3PO7∶Dy^3+ samples,and the as-synthesized Gd3PO7∶Dy^3+ sample with 3% Dy^3+ can emit white light with the coordinate of(0.335,0.345),which indicates that Gd3PO7∶Dy^3+ is a potential single-host white-emitting phosphor.

Bastnaesite was synthesized with hydrothermal method using cerium nitrate,sodium bicarbonate and sodium fluoride as raw materials.The effects of reaction time on the surface properties and denitration activity of the synthetic bastnaesite were investigated,and the reasons for the different synthetic products caused by different sodium bicarbonate dosages were analyzed.The crystal structure,particle size and surface morphology of the bastnaesite were characterized by SEM and XRD.The denitration performance of the obtained bastnaesite was investigated by H2-TPR and simulated flue gas denitration experiment.The results show that the longer the reaction time,the larger the main particles of the synthesized bastnaesite,the higher the crystal growth degree and the easier the particle polymerization.The concentration of bicarbonate ions in the initial reactant determines the product composition.When bicarbonate ions are excessive,the synthesized product is relatively pure bastnaesite.When bicarbonate ions are insufficient,there is cerium fluoride in the product.The optimal conditions for preparing high-grade bastnaesite determined by experiments are reaction time of 2 h and molar ratio of sodium bicarbonate to cerium nitrate of 3∶1.