Removing calcium and magnesium by fluorine precipitation is the most common method to prepare high-purity manganese sulfate solution.However,the introduced fluorine needs a further removal.In this paper,a new technology is proposed to separate and recover fluorine from fluorine-containing manganese sulfate solution,mainly including the two processes of solvent extraction for fluorine and cyclic stripping of fluorine with manganese oxide.Under such conditions,including initial pH of 1.9 for manganese sulfate solution,organic phase composition of 60%TBP+40%sulfonated kerosene,O/A ratio of 2∶1,and extraction time of 3 min,the concentration of fluorine in manganese sulfate solution can be reduced to below 35 mg/L after a five-stage countercurrent extraction at room temperature.And under the optimal stripping conditions of manganese oxide addition of 1.0 times the theoretical amount,O/A ratio of 5∶1,stripping time of 1 h,and temperature of 298 K,the cyclic stripping efficiency of manganese oxide reaches above 98.08%,and the manganese fluoride precipitated in the stripping process can be used for the removal of calcium and magnesium in manganese sulfate solution in return.Compared with the existing fluorine stripping process,this new technology can realize the recycling of fluorine while removing fluorine in depth.

Ni60/WC composite coatings with different Y₂O₃contents were prepared on the surface of H13 steel by laser cladding in-situ generation method,and the macrostructure,microstructure,and microhardness of the coatings were analyzed to find the optimal Y₂O₃addition.And the phase composition,microstructure,microhardness,and wear mechanism of the WC/Ni60 gradient composite coatings with the optimal Y₂O₃addition were also investigated.The results show that the microhardness of the composite coatings presents a trend of increasing at first and then decreasing with the increase of Y₂O₃content.When the Y₂O₃content is 1.5%,the macroscopic quality of the coatings reaches the best with refined grains and the largest microhardness.And when the Y₂O₃content continues to increase,the WC particles in the coatings become larger again while the microhardness decreases.Compared with gradient composite coatings without the addition of rare earth,the thickness of the gradient composite coatings doped with rare earth is reduced,and the morphology and distribution of the microstructure undergo some changes.And the internal enhancement phase particles become finer and more uniform with the angles being blunted,and the microhardness of each layer from top to bottom increases by 49.2 HV_0.5,75.78 HV_0.5,and 72.78 HV_0.5,respectively.The wear loss receives a decrease for different time,and the wear mechanism still consists of adhesive wear,brittle spalling,and abrasive wear.

Using TiO₂,MoO₃,Nb₂O₅,Ta₂O₅,ZrO₂,B₄C and carbon black as raw materials,(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder was prepared by high-energy ball milling and boro/carbothermal reduction method,with the phase composition and microstructure of the reaction products being characte-rized by XRD and SEM.The results show that ball milling time,reduction temperature,and holding time are important factors for the preparation of high-quality(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder.The high-quality(Ti,Mo,Nb,Ta,Zr)B₂ high-entropy ceramic powder can be prepared with particle size of 1~2μm,uniform distribution of elements,and single phase composition under the conditions of ball milling time of 2 h,vacuum carbothermal reduction temperature of 1700℃,and holding time of 2 h.

Ag-Ni-Sc series alloys were prepared by vacuum induction smelting furnace.The corrosion beha-vior of these series of alloys in 0.1 mol/L Na₂S solution and H₂S atmosphere was studied by immersion corrosion and electrochemical tests.And the effects of Sc addition on the corrosion morphology,components of the corrosion products,microstructure,and mechanical properties of Ag-Ni alloys were investigated by SEM,EDS,OM,and hardness tests.The results show that the moderate addition of Sc can reduce the corrosion current of the alloy,improve the sulfuration resistance of the alloy,refine the grains of the alloy,and thus enhance the hardness of the alloy.However,excessive Sc content will lead to excess amount of intermetallic compounds and grain boundary segregation in the alloy microstructure,deteriorating the hardness and sulfuration resistance of the alloy.Taking all factors into consideration,the optimum addition of Sc in Ag-Ni alloys is 0.15%.

Five Mg-xLa alloys with different La contents were prepared by casting method.The effects of La content on the microstructure and corrosion resistance of Mg-xLa alloys were systematically investigated by optical microscope,scanning electron microscope,X-ray diffractometer,microhardness tester and electrochemical workstation.The results show that Mg₁₂La is the only second phase in the Mg-xLa alloys.With the increase of La content,the magnesium alloy grains are gradually refined at first,and the subsequent grain size difference is small.The grain size of Mg-3La alloy is the finest,and its size distribution is also more uniform compared with other alloys.As the content of La increases,the microhardness of the Ma-xLa alloys increases firstly and then decreases slightly,and reaches the maximum value when the La content is 3%.In a 3.5%NaCl solution at 25℃,the corrosion rate of the Mg-La alloy with high La con-tent is significantly lower than that of the Mg-La alloy with low La content.And the corrosion potential of Mg-3La alloy in the 3.5%NaCl solution negatively moves in general with the increase of solution temperature,and its corrosion resistance is the best in the 30℃solution.

To realize the high value-added resource utilization of blast furnace slag,photocatalytic permeable bricks were prepared by green body molding and sintering with the slag as the main material,kaolin and potassium feldspar as binder and fluxing agent,and ammonium metavanadate was used as the doping vanadium source to improve the photocatalytic performance of the prepared material.The phase and morphology of the permeable bricks sintered at different temperatures were analyzed by XRD and SEM.The effects of sintering temperature and holding time on the properties of permeable bricks were studied.The results show that when the mass ratio of blast furnace slag,kaolin and potassium feldspar is 75∶10∶15,the doping amount of ammonium metavanadate is 45%TiO₂mass,the molding pressure is 10 MPa,the particle size of blast furnace slag is 630~850μm,the sintering temperature is 1120℃,and the holding time is 3 h,the permeability coefficient,flexural strength,appearance size deviation and frost resistance of the prepared permeable bricks meet the national standards,and they have good photocatalytic performance,with a permeability coefficient of 0.049 cm/s,a flexural strength of 10 MPa,and a photocatalytic degradation rate of 75%.

The effects of the particle size and composition of cobalt powder on the physical and mechanical properties of submicron-grained WC-10Co cemented carbide were investigated.The results show that for the same sintering process,the finer the cobalt powder,the higher the surface energy,the lower the melting temperature,the longer the alloy densification time,and the cobalt vapor volatilization time also increases correspondingly.As the particle size of cobalt powder decreases,the density of the alloy increases,while the hardness and magnetic coercive force decrease,and the bending strength increases at first and then decreases,reaching its maximum when the particle size of cobalt powder is 0.73μm.The content of Cl in cobalt powder is also one of the important factors affecting the pores of cemented carbides.When the Cl content reaches 550×10^-6,a large number of pores appear inside the alloy.To obtain submicron-grained cemented carbides with excellent properties,it is necessary to strictly control the composition of raw materials,and adjust the production process,shorten the ball milling time,and reduce the sintering temperature.The submicron-grained WC-10Co cemented carbide,prepared using cobalt powder with a FSSS particle size of 0.73μm and Cl content of 171×10^-6,has a bending strength of 4231 N/mm~2,a hardness of 91.8 HRA,a density of 14.45 g/cm~3 and a magnetic coercive force of 19.1 kA/m.

WC-AlCoCrFeNiTi_0.8cemented carbide was prepared by vacuum sintering method using mechanically alloyed AlCoCrFeNiTi_0.8high-entropy alloy powder as binder phase,and the effects of sintering temperature and binder phase content on the microstructure and mechanical properties of the cemented carbide were investigated.The results show that the grain size of WC-AlCoCrFeNiTi_0.8cemented carbide increases with the increase of sintering temperature and decreases with the increase of binder phase content.And a new phase known as the FCC phase appears.As the sintering temperature increases,the hardness and toughness of the cemented carbide increase initially before declining,and the hardness decreases with the increase of binder phase content,with toughness being the opposite.Compared with WC-Co,the binder phase AlCoCrFeNiTi_0.8can inhibit the growth of WC grains due to its slow diffusion effect,and the average WC grain size of WC-AlCoCrFeNiTi_0.8cemented carbide is reduced by 54.36%while the hardness is increased by 23.98%.At the sintering temperature of 1450℃,WC-10AlCoCrFeNiTi_0.8has better comprehensive mechanical properties with a hardness of 1923 HV₃₀and fracture toughness of 9.13 MPa·m^1/2,which are higher than those of commercial WC-Co cemented carbide.

CVD diamond-coated cemented carbide tool is ideal for the machining of composite materials,including non-ferrous metals,alloys,graphite,ceramic,and carbon fiber reinforced plastic(CFRP).However,the pretreatment process of WC-Co cemented carbide substrate before diamond coating reduces the strength of the substrate while eliminating Co on the surface to improve the adhesion of the coating.The influence mechanism of pretreatment on the substrate strength of WC-6Co cemented carbides with two WC grain sizes was studied through orthogonal experiments.The surface morphology and Co content of the sample were analyzed by SEM and EDS,and the phase composition of the sample surface was analyzed by XRD.The results show that both acid and alkali pretreatment significantly decrease the strength of the substrate,while heat treatment can eliminate the unfavorable influence of acid and alkali treatment on the strength.The influence of pretreatment on the strength of cemented carbide substrate with different WC grain sizes is obviously different.In general,the decrease in transverse rupture strength(TRS)after pretreatment is greater for coarse-grained cemented carbides,and the Weibull modulus of TRS also decreases more significantly.Comparatively speaking,the TRS of coarse-grained cemented carbide is more sensitive to acid corrosion time,t_C,while that of fine-grained cemented carbide is more affected by alkali corrosion time,t_M.Therefore,an appropriate pretreatment system should be matched to the composition and microstructure of different cemented carbide substrates before diamond coating.

Steel-bonded cemented carbide is widely used in new tool materials and molds due to its high hardness and good wear resistance.The influence of the composition design of hard phase and binder phase of TiC steel-bonded cemented carbide on the microstructure and performance of the material is outlined,and preparation methods of TiC steel-bonded cemented carbide are also introduced.Among these methods,powder metallurgy process is still the mainstream method,and the optimization of ball milling,pressing,and sintering process in the powder metallurgy method is elaborated.In addition,in-situ synthesis method,hydraulic infiltration method,and surface coating of steel-bonded cemented carbide show great development potentials due to their low cost and excellent performance.Finally,the current shortcomings of TiC steel-bonded cemented carbide are analyzed and its future development trend is prospected.