Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerization of ethylene and propylene were prepared. The effects of reaction tempe...Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerization of ethylene and propylene were prepared. The effects of reaction temperature, ethylene/propylene molar ratio, aluminium/vanadium （Al/V） molar ratio and titanium/vanadium molar ratio on the catalytic activity were investigated. The molecular weight, molecular weight distribution, sequence composition and crystallinity of the products were measured by gel permeation chromatography, ^13C-NMR and differential scanning calorimetry analysis, respectively. In comparison to the vanadium and titanium catalysts, the bimetallic catalyst showed higher catalytic activity and better copolymerization performance. The obtained ethylene/propylene copolymers have high molecular weight （105）, broad molecular weight distribution, high propylene content with random or short blocked sequence structures （rErp = 1.919）, low melting temperatures and low crystallinities （Xc 〈 20%）.展开更多
An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio...An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio of 1.2꞉1,and pre-oxidation temperature of 900℃,the iron metallization degree is 97.8%.Ultimately,magnetic separation yields an iron concentrate with an Fe content of 76.78 wt.%and efficiency of 93.41%,while the magnetic separation slag has a Ti grade and recovery of 9.36 wt.%and 87.07%,respectively,with a titanium loss of 12.93%.This new strategy eliminates the beneficiation process of VTM raw ore,effectively reduces the Ti content in the iron concentrate,and improves the comprehensive utilization of valuable metals.展开更多
Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive n...Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive nature of titanium,metallic titanium production involves extensive procedures and high costs.Considering its advantages and limitations,the European Union has classified titanium metal as a critical raw material(CRM)of low category.The Kroll process is predominantly used to produce titanium;however,molten salt electrolysis(MSE)is currently being explored for producing metallic titanium at a low cost.Since 2000,electrolytic titanium production has undergone a wave of technological advancements.However,because of the intermediate and disproportionation reactions in the electrolytic titanium production process,the process efficiency and titanium purity according to industrial standards could not be achieved.Consequently,metallic titanium production has gradually diversified into employing technologies such as thermal reduction,MSE,and titanium alloy preparation.This study provides a comprehensive review of research advances in titanium metal preparation technologies over the past two decades,highlighting the challenges faced by the existing methods and proposing potential solutions.It offers useful insights into the development of low-cost titanium preparation technologies.展开更多
Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.T...Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.The microstructure of as-cast Ti-5552-xNb alloy is consisted of a singleβphase,and theβgrain size increases slightly with the increase of Nb content.The thermal effect in the process of high temperature drawing leads to the precipitation ofαphase.The addition of Nb in Ti-5552 titanium alloys reduces theα/βphase transformation temperature,which causes a decrease in the volume fraction ofαphase.Reducing theαphase content reduces incompatibility,but too low a proportion ofαphase will lead to premature fracture,so tensile strength and plasticity firstly increase and then decrease.The results show that Ti-5552-9Nb titanium alloy shows the best tensile strength(307.2 MPa)and superplasticity(106%).The superplastic mechanism of Ti-5552-9Nb alloy is mainly caused by relative sliding ofβgrain boundaries and dislocation movement.展开更多
During electrochemical machining(ECM),the passivation film formed on the surface of titanium alloy can lead to uneven dissolution and pitting.Solid particle erosion can effectively remove this passivation film.In this...During electrochemical machining(ECM),the passivation film formed on the surface of titanium alloy can lead to uneven dissolution and pitting.Solid particle erosion can effectively remove this passivation film.In this paper,the electrochemical dissolution behavior of Ti-6.5Al-2Zr-1Mo-1V(TA15)titanium alloy at without particle impact,low(15°)and high(90°)angle particle impact was investigated,and the influence of Al_(2)O_(3)particles on ECM was systematically expounded.It was found that under the condition of no particle erosion,the surface of electrochemically processed titanium alloy had serious pitting corrosion due to the influence of the passivation film,and the surface roughness(Sa)of the local area reached 10.088μm.Under the condition of a high-impact angle(90°),due to the existence of strain hardening and particle embedding,only the edge of the surface is dissolved,while the central area is almost insoluble,with the surface roughness(S_(a))reaching 16.086μm.On the contrary,under the condition of a low-impact angle(15°),the machining efficiency and surface quality of the material were significantly improved due to the ploughing effect and galvanic corrosion,and the surface roughness(S_(a))reached 2.823μm.Based on these findings,the electrochemical dissolution model of TA15 titanium alloy under different particle erosion conditions was established.展开更多
Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding str...Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.展开更多
To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures rangi...To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.展开更多
By means of isothermal oxidation and chemical analysis, great importance was attached to the parameters that made effects on the oxidation degree of vanadium, titanium-bearing magnetite pellet in high-temperature proc...By means of isothermal oxidation and chemical analysis, great importance was attached to the parameters that made effects on the oxidation degree of vanadium, titanium-bearing magnetite pellet in high-temperature processing （1 073- 1 323 K）. Based on the experimental data, oxidation kinetics of pellet was analyzed according to shrinking unreacted-core model subsequently. Experiment results display that the oxidation degree of pellet increases with increasing of oxidation time, oxidation temperature and oxygen content, as well as shrinking of pellet diameter. Under the condition of oxidation time 20 min, oxidation temperature 1223 K, oxygen content 15%, and pellet diameter 12 mm, oxidation degree of pellet reaches 92.92%. The analysis of oxidation kinetics indicates that oxidation process of pellet is controlled by chemical reaction with activation energy 68.64 kJ/mol at a relatively lower temperature （1073-1 173 K）. Oxidation process of pellet is mixed-controlled by chemistry reaction and diffusion with activation energy 39.66 kJ/mol in the temperature range of 1 173-1 273 K. When oxidation temperature is higher than 1 273 K, the limited link of oxidation reaction is the diffusion control with the activation energy 20.85 kJ/mol. These results can serve as a reference to the production of vanadium, titanium-hearing magnetite pellet.展开更多
To achieve high efficiency utilization of high-chromium vanadium-titanium magnetite （V-Ti-Cr） fines, an investigation of V Ti42r fines was conducted using a sinter pot. The chemical composition, particle parameters,...To achieve high efficiency utilization of high-chromium vanadium-titanium magnetite （V-Ti-Cr） fines, an investigation of V Ti42r fines was conducted using a sinter pot. The chemical composition, particle parameters, and granulation of V-Ti-Cr mixtures were analyzed, and the effects of sintering parameters on the sintering behaviors were investigated. The results indicated that the optimum quicklime dosage, mixture moisture, wetting time, and granulation time for V-Ti-Cr fines are 5wt%, 7.5wt%, 10 min, and 5-8 min, respectively. Meanwhile, the vertical sintering speed, yield, tumbler strength, and productivity gains were shown to be 21.28 mm/min, 60.50wt% , 58.26wt%, and 1.36 t·m^-2·h^-1, respectively. Furthermore, the consolidation mechanism of V-Ti-Cr fines was clarified, revealing that the consolidation of a V-Ti-Cr sinter requires an approximately 14vo1% calcium ferrite liquid-state, an approximately 15vo1% silicate liq- uid-state, a solid-state reaction, and the recrystallization of magnetite. Compared to an ordinary sinter, calcium ferrite content in a V-Ti-Cr sinter is lower, while the perovskite content is higher, possibly resulting in unsatisfactory sinter outcomes.展开更多
The effect of diboron trioxide(B_2O_3) on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets was investigated in this work. The main characterization methods were X-ray ...The effect of diboron trioxide(B_2O_3) on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets was investigated in this work. The main characterization methods were X-ray fluorescence, inductively coupled plasma–atomic emission spectroscopy, mercury injection porosimetry, X-ray diffraction, metallographic microscopy, and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the crushing strength increased greatly with increasing B_2O_3 content and that the increase in crushing strength was strongly correlated with a decrease in porosity, the formation of liquid phases, and the growth and recrystallization consolidation of hematite crystalline grains. The smelting properties were measured under simulated blast furnace conditions; the results showed that the smelting properties within a certain B_2O_3 content range were improved and optimized except in the softening stage. The valuable element B was easily transformed to the slag, and this phenomenon became increasingly evident with increasing B_2O_3 content. The formation of Ti(C,N) was mostly avoided, and the slag and melted iron were separated well during smelting with the addition of B_2O_3. The size increase of the melted iron was consistent with the gradual optimization of the dripping characteristics with increasing B_2O_3 content.展开更多
Electron beam welding experiments of titanium alloys with different vanadium content to stainless steel,as well as alpha titanium to stainless steel using vanadium sheets as filler metal and transition portion were ca...Electron beam welding experiments of titanium alloys with different vanadium content to stainless steel,as well as alpha titanium to stainless steel using vanadium sheets as filler metal and transition portion were carried out.Microstructures of the joints were examined by scanning electron microscope.The properties were evaluated by microhardness and tensile strength.It was shown that electron beam welding is not feasible due to the brittle Ti-Fe intermetallics with high hardness.Increase of vanadium content in base metal can restrain but can't avoid the formation of cracks.When vanadium content was too large,the joint was embrittled by FeTi compound with supersaturated V and also cracked after welding.Crack free joint was achieved by using vanadium transition portion which can prevent the contact of Ti and Fe elements.However,the formation of brittle σ intermetallics reduced the tensile strength of the joint,only up to 134MPa.展开更多
The process of pressure leaching the converter vanadium slag with waste titanium dioxide without roasting was studied. Mineralogy analysis indicates that the con- verter vanadium slag contains mainly three mineral pha...The process of pressure leaching the converter vanadium slag with waste titanium dioxide without roasting was studied. Mineralogy analysis indicates that the con- verter vanadium slag contains mainly three mineral phases： magnetite, titanium magnetite, and silicate phase. Vana- dium is in combination with iron, titanium, manganese, aluminum, and silicon. The impacts of leaching tempera- ture, leaching time, stirring speed, liquid-to-solid ratio, and initial leaching agent concentration were investigated on the waste titanium dioxide leaching process. The results indi- cate that under the optimal conditions, the vanadium and the iron leaching rates are 96.85 % and 93.50 %, respectively, and the content of titanium is 12.6 % in the residue. The main mineral phases for the residues under the optimal operation conditions are quartz, ilmenite, anatase, and sili- cate phase, and the residues can be reused as the extraction of titanium raw materials for titanium dioxide production technology by the sulfate method.展开更多
In order to clarify the slag system of high Cr2O3 vanadium-titanium magnetite smelting in BF （blast furnace）, the melting properties of slag samples prepared by analytically pure reagents were measured. By means of ...In order to clarify the slag system of high Cr2O3 vanadium-titanium magnetite smelting in BF （blast furnace）, the melting properties of slag samples prepared by analytically pure reagents were measured. By means of orthogonal test synthetic weighted score method, the optimal slag for high Cr2O3 vanadium-titanium magnetite was obtained, which contained 10% MgO, 8% TiO2 and 15% Al2O3, with the binary basicity being 1.15. In addition, the effects of basicity, MgO, TiO2 and A12 03 on slag melting properties were investigated by single factor test, and the results showed that, with increasing the basicity or TiO2 content, melting temperature （Tin） increased, whereas initial vis- cosity （r/0） and high temperature viscosity （r/h） decreased. With increasing the MgO content, Tm decreased firstly and then increased. With increasing the Al2 O3 content, Tm increased, and η0 and r/h decreased firstly and then increased.展开更多
The oxidation kinetics, structural changes, and elements migration during the oxidation process of the va- nadium-titanium magnetite （VTM） ore were analyzed. Kinetics analysis indicated that the oxidation process wa...The oxidation kinetics, structural changes, and elements migration during the oxidation process of the va- nadium-titanium magnetite （VTM） ore were analyzed. Kinetics analysis indicated that the oxidation process was con- trolled by diffusion control and could be divided into interface diffusion and lattice diffusion with apparent activation energy of 99.69 kJ/mol and 144.08 kJ/mol in the range of 800--1000℃, respectively. The surface structure changed with the oxidization temperature as follows： dense surface→nano sized sheets→submicron particles→molten particles. The compact structure changed into porous one because of the elements migration and enrichment. Both Fe and Ti elements migrated in the opposite direction during the oxidation process. The V etement in the raw ore stably existed in the form of V^5＋ state, some vanadium migrated and occupied the tetrahedral sites of the hematite during the oxidation process.展开更多
Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, ins...Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.展开更多
The sintering of chromium-containing vanadium-titanium magnetite using different coke contents was studied through the sintering pot tests, X-ray diffraction analysis and mineralogical phase analysis. Results showed t...The sintering of chromium-containing vanadium-titanium magnetite using different coke contents was studied through the sintering pot tests, X-ray diffraction analysis and mineralogical phase analysis. Results showed that, as the coke content increased from 3.2% to 4.4%, the liquid phase and combustion zone thickness increased while the vertical sintering rate and ratio of sintered product decreased. In addition, the combustion ratio of exhaust gas also increased with increasing the coke content, indicating that combustion zone temperature also increased, and the excessive the coke content in the sintering process of vanadiumtitanium magnetite is harmful. As the coke content increased, the magnetite, silicates, and perovskite contents of the sintered ore increased while the contents of hematite and calcium ferrite of sintered ore decreased; drum strength decreased, and reduction degradation properties increased while reduction ability decreased. We found that the appropriate coke content for the sintering process is 3.6 wt%.展开更多
The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis.According to the t...The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis.According to the thermodynamic results,low-melting-point regions and MgTi2O5primary phase area in the phase diagrams,the suggested titanium slag composition for the present vanadium titanomagnetite metallized pellets should consist of50%TiO2,8%-12%MgO and13%Al2O3(mass fraction)with a binary basicity of0.8-1.2.Finally,the verified smelting experiments were conducted and successful separation of the molten iron from the titanium slag is obtained.The obtained vanadium-containing molten iron contains0.681%V and0.267%Ti,and the obtained titanium slag contains52.21%TiO2(mass fraction),in which MgTi2O5is the primary phase.The titanium resource in the final titanium slag production could be used to produce TiO2pigment by acid leaching methods.展开更多
Titanium mineral was prepared from vanadium titanomagnetite concentrates by hydrogen reduction and acid leaching.The leaching behaviors of elements like Fe,V,Mn,Al,Mg,Ca,and Si were highly related to the reduction deg...Titanium mineral was prepared from vanadium titanomagnetite concentrates by hydrogen reduction and acid leaching.The leaching behaviors of elements like Fe,V,Mn,Al,Mg,Ca,and Si were highly related to the reduction degree.The phase compositions of the reduced materials and the leached residues were analyzed by XRD to identify the effect of reduction degree on the leaching mechanisms.The results showed that the concentrates were reduced to iron metal and titanomagnetite at 800-1000°C for 0.5 h,and the above elements of Fe and impurities were easily leached.Deeper reduction led to the formation of ilmenite and Mg-Al spinel,which hindered leaching.Mg-bearing anosovite appeared in the further reduced materials,and the leaching rates of impurities became much lower.An upgraded titanium mineral with a normalized TiO_(2) grade of 70.3%was achieved by H_(2) reduction at 850°C for 0.5 h and acid leaching,which is a satisfactory Ti resource for the preparation of titanium oxide by sulfate process.展开更多
To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,t...To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.展开更多
基金supported by the Program for New Century Excellent Talents in Universities(NCET-07-0142)the Program for New Century Excellent Talents in Heilongjiang Provincial Universities(NCET-06-010)+1 种基金the National Natural Science Foundation of China(No.20972025)the Science Foundation of Tianjin University of Science & Technology(No.20090420)
文摘Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerization of ethylene and propylene were prepared. The effects of reaction temperature, ethylene/propylene molar ratio, aluminium/vanadium （Al/V） molar ratio and titanium/vanadium molar ratio on the catalytic activity were investigated. The molecular weight, molecular weight distribution, sequence composition and crystallinity of the products were measured by gel permeation chromatography, ^13C-NMR and differential scanning calorimetry analysis, respectively. In comparison to the vanadium and titanium catalysts, the bimetallic catalyst showed higher catalytic activity and better copolymerization performance. The obtained ethylene/propylene copolymers have high molecular weight （105）, broad molecular weight distribution, high propylene content with random or short blocked sequence structures （rErp = 1.919）, low melting temperatures and low crystallinities （Xc 〈 20%）.
基金funded by the National Natural Science Foundation of China(Nos.U20A20145,51774205)the Open Project from Engineering Research Center of the Ministry of Education,Sichuan University,China.
文摘An approach for coal-based direct reduction of vanadium−titanium magnetite(VTM)raw ore was proposed.Under the optimal reduction conditions with reduction temperature of 1140℃,reduction time of 3 h,C-to-Fe molar ratio of 1.2꞉1,and pre-oxidation temperature of 900℃,the iron metallization degree is 97.8%.Ultimately,magnetic separation yields an iron concentrate with an Fe content of 76.78 wt.%and efficiency of 93.41%,while the magnetic separation slag has a Ti grade and recovery of 9.36 wt.%and 87.07%,respectively,with a titanium loss of 12.93%.This new strategy eliminates the beneficiation process of VTM raw ore,effectively reduces the Ti content in the iron concentrate,and improves the comprehensive utilization of valuable metals.
基金financial support from the Yunnan Province Key Industries Science and Technology Special Project for Colleges and UniversitiesChina(No.FWCY-QYCT2024006)+6 种基金National Natural Science Foundation of China(Nos.52104351 and 52364051)Science and Technology Major Project of Yunnan Province,China(No.202202AG050007)the Yunnan Fundamental Research ProjectsChina(No.202401AT070314)the Key Technology Research and Development Program of Shandong Province,China(No.2023CXGC010903)Central Guidance Local Scientific and Technological Development Funds,China(No.202407AB110022)Yunnan Province Xingdian Talent Support Plan Project,China。
文摘Titanium exhibits outstanding properties,particularly,high specific strength and resistance to both high and low temperatures,earning it a reputation as the metal of the future.However,because of the highly reactive nature of titanium,metallic titanium production involves extensive procedures and high costs.Considering its advantages and limitations,the European Union has classified titanium metal as a critical raw material(CRM)of low category.The Kroll process is predominantly used to produce titanium;however,molten salt electrolysis(MSE)is currently being explored for producing metallic titanium at a low cost.Since 2000,electrolytic titanium production has undergone a wave of technological advancements.However,because of the intermediate and disproportionation reactions in the electrolytic titanium production process,the process efficiency and titanium purity according to industrial standards could not be achieved.Consequently,metallic titanium production has gradually diversified into employing technologies such as thermal reduction,MSE,and titanium alloy preparation.This study provides a comprehensive review of research advances in titanium metal preparation technologies over the past two decades,highlighting the challenges faced by the existing methods and proposing potential solutions.It offers useful insights into the development of low-cost titanium preparation technologies.
基金the financial support by the Major Science and Technology Achievement Transformation Project in Heilongjiang Province(ZC2023SH0075)the National Natural Science Foundation of China(52425401,U2441255,52474377,and 52371015)+1 种基金the Young Elite Scientists Sponsorship Program by·CAST(2021QNRC001)the Henan Provincial Key Research and Development&Promotion Special Program(251111231400)。
文摘Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb(abbreviated as Ti-5552-xNb,x=3,6,9,12,wt.%)contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature.The microstructure of as-cast Ti-5552-xNb alloy is consisted of a singleβphase,and theβgrain size increases slightly with the increase of Nb content.The thermal effect in the process of high temperature drawing leads to the precipitation ofαphase.The addition of Nb in Ti-5552 titanium alloys reduces theα/βphase transformation temperature,which causes a decrease in the volume fraction ofαphase.Reducing theαphase content reduces incompatibility,but too low a proportion ofαphase will lead to premature fracture,so tensile strength and plasticity firstly increase and then decrease.The results show that Ti-5552-9Nb titanium alloy shows the best tensile strength(307.2 MPa)and superplasticity(106%).The superplastic mechanism of Ti-5552-9Nb alloy is mainly caused by relative sliding ofβgrain boundaries and dislocation movement.
基金supported by the National Natural Science Foundation of China(No.52175414)the Natural Science Foundation of Jiangsu Province of China(No.BK20220134)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.NE2023002)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0559)。
文摘During electrochemical machining(ECM),the passivation film formed on the surface of titanium alloy can lead to uneven dissolution and pitting.Solid particle erosion can effectively remove this passivation film.In this paper,the electrochemical dissolution behavior of Ti-6.5Al-2Zr-1Mo-1V(TA15)titanium alloy at without particle impact,low(15°)and high(90°)angle particle impact was investigated,and the influence of Al_(2)O_(3)particles on ECM was systematically expounded.It was found that under the condition of no particle erosion,the surface of electrochemically processed titanium alloy had serious pitting corrosion due to the influence of the passivation film,and the surface roughness(Sa)of the local area reached 10.088μm.Under the condition of a high-impact angle(90°),due to the existence of strain hardening and particle embedding,only the edge of the surface is dissolved,while the central area is almost insoluble,with the surface roughness(S_(a))reaching 16.086μm.On the contrary,under the condition of a low-impact angle(15°),the machining efficiency and surface quality of the material were significantly improved due to the ploughing effect and galvanic corrosion,and the surface roughness(S_(a))reached 2.823μm.Based on these findings,the electrochemical dissolution model of TA15 titanium alloy under different particle erosion conditions was established.
基金supported by the National Key R&D Program of China (No. 2018YFA0707300)the National Natural Science Foundation of China (No. 52374376)the Introduction Plan for High end Foreign Experts, China (No. G2023105001L)。
文摘Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates.The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated.Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa.During the cold roll-bonding process,the hardened layer fractures,leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill.This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface,consequently weakening the interfacial bonding strength.In metals with high work hardening rates,the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.
基金Project(2007CB613504)supported by the National Key Basic Research Program of ChinaProjects(51004033,50974035,51074047)supported by the National Natural Science Foundation of ChinaProject(2008BAB34B01)supported by National Science and Technology Support Plan of China during the 11th Five-Year Plan
文摘To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.
基金Item Sponsored by National Science Fund for Distinguished Young Scholars of China(50725416)National Natural Science Foundation of China(50804059)+1 种基金National Key Programof Science and Technology of China(2008BAB32B06)Graduate Degree Thesis Innovation Foundation of Hunan Province and Central South University of China(1960-71131100053)
文摘By means of isothermal oxidation and chemical analysis, great importance was attached to the parameters that made effects on the oxidation degree of vanadium, titanium-bearing magnetite pellet in high-temperature processing （1 073- 1 323 K）. Based on the experimental data, oxidation kinetics of pellet was analyzed according to shrinking unreacted-core model subsequently. Experiment results display that the oxidation degree of pellet increases with increasing of oxidation time, oxidation temperature and oxygen content, as well as shrinking of pellet diameter. Under the condition of oxidation time 20 min, oxidation temperature 1223 K, oxygen content 15%, and pellet diameter 12 mm, oxidation degree of pellet reaches 92.92%. The analysis of oxidation kinetics indicates that oxidation process of pellet is controlled by chemical reaction with activation energy 68.64 kJ/mol at a relatively lower temperature （1073-1 173 K）. Oxidation process of pellet is mixed-controlled by chemistry reaction and diffusion with activation energy 39.66 kJ/mol in the temperature range of 1 173-1 273 K. When oxidation temperature is higher than 1 273 K, the limited link of oxidation reaction is the diffusion control with the activation energy 20.85 kJ/mol. These results can serve as a reference to the production of vanadium, titanium-hearing magnetite pellet.
基金financially supported by the National Basic Research Program of China(Nos.2013CB632601 and 2013CB632604)the National Science Foundation for Distinguished Young Scholars of China(Nos.51125018 and 51504230)+2 种基金the Key Research Program of Chinese Academy of Sciences(No.KGZD-EW-201-2)the National Natural Science Foundation of China(Nos.51374191 and 2110616751104139)China Postdoctoral Science Foundation(Nos.2012M510552 and 2013T60175)
基金the National High Technology Research and Development Program of China (Nos. 2012AA062302 and 2012AA062304)the Program of the National Natural Science Foundation of China (Nos. 51090384 and 51174051)The International Cooperation of the Ministry of Science and Technology of China (No. 2012DFR60210)
文摘To achieve high efficiency utilization of high-chromium vanadium-titanium magnetite （V-Ti-Cr） fines, an investigation of V Ti42r fines was conducted using a sinter pot. The chemical composition, particle parameters, and granulation of V-Ti-Cr mixtures were analyzed, and the effects of sintering parameters on the sintering behaviors were investigated. The results indicated that the optimum quicklime dosage, mixture moisture, wetting time, and granulation time for V-Ti-Cr fines are 5wt%, 7.5wt%, 10 min, and 5-8 min, respectively. Meanwhile, the vertical sintering speed, yield, tumbler strength, and productivity gains were shown to be 21.28 mm/min, 60.50wt% , 58.26wt%, and 1.36 t·m^-2·h^-1, respectively. Furthermore, the consolidation mechanism of V-Ti-Cr fines was clarified, revealing that the consolidation of a V-Ti-Cr sinter requires an approximately 14vo1% calcium ferrite liquid-state, an approximately 15vo1% silicate liq- uid-state, a solid-state reaction, and the recrystallization of magnetite. Compared to an ordinary sinter, calcium ferrite content in a V-Ti-Cr sinter is lower, while the perovskite content is higher, possibly resulting in unsatisfactory sinter outcomes.
基金financially supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (No. 2015BAB19B02)the National Program on Key Basic Research Project of China (No. 2013CB632603)
文摘The effect of diboron trioxide(B_2O_3) on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets was investigated in this work. The main characterization methods were X-ray fluorescence, inductively coupled plasma–atomic emission spectroscopy, mercury injection porosimetry, X-ray diffraction, metallographic microscopy, and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the crushing strength increased greatly with increasing B_2O_3 content and that the increase in crushing strength was strongly correlated with a decrease in porosity, the formation of liquid phases, and the growth and recrystallization consolidation of hematite crystalline grains. The smelting properties were measured under simulated blast furnace conditions; the results showed that the smelting properties within a certain B_2O_3 content range were improved and optimized except in the softening stage. The valuable element B was easily transformed to the slag, and this phenomenon became increasingly evident with increasing B_2O_3 content. The formation of Ti(C,N) was mostly avoided, and the slag and melted iron were separated well during smelting with the addition of B_2O_3. The size increase of the melted iron was consistent with the gradual optimization of the dripping characteristics with increasing B_2O_3 content.
文摘Electron beam welding experiments of titanium alloys with different vanadium content to stainless steel,as well as alpha titanium to stainless steel using vanadium sheets as filler metal and transition portion were carried out.Microstructures of the joints were examined by scanning electron microscope.The properties were evaluated by microhardness and tensile strength.It was shown that electron beam welding is not feasible due to the brittle Ti-Fe intermetallics with high hardness.Increase of vanadium content in base metal can restrain but can't avoid the formation of cracks.When vanadium content was too large,the joint was embrittled by FeTi compound with supersaturated V and also cracked after welding.Crack free joint was achieved by using vanadium transition portion which can prevent the contact of Ti and Fe elements.However,the formation of brittle σ intermetallics reduced the tensile strength of the joint,only up to 134MPa.
基金financially supported by the Chinese National Programs for High Technology Research and Development(Nos.2010AA03A405 and 2012AA062303)the National Natural Science Foundation of China(Nos.U1202274,51004033,51204040,and 50974035)+2 种基金the National Science and Technology Support Program(No.2012BAE01B02)the Fundamental Research Funds for the Central Universities(No.N100302005)the Doctoral Fund Project(No.20120042110011)
文摘The process of pressure leaching the converter vanadium slag with waste titanium dioxide without roasting was studied. Mineralogy analysis indicates that the con- verter vanadium slag contains mainly three mineral phases： magnetite, titanium magnetite, and silicate phase. Vana- dium is in combination with iron, titanium, manganese, aluminum, and silicon. The impacts of leaching tempera- ture, leaching time, stirring speed, liquid-to-solid ratio, and initial leaching agent concentration were investigated on the waste titanium dioxide leaching process. The results indi- cate that under the optimal conditions, the vanadium and the iron leaching rates are 96.85 % and 93.50 %, respectively, and the content of titanium is 12.6 % in the residue. The main mineral phases for the residues under the optimal operation conditions are quartz, ilmenite, anatase, and sili- cate phase, and the residues can be reused as the extraction of titanium raw materials for titanium dioxide production technology by the sulfate method.
基金Item Sponsored by National Natural Science Foundation of China(51090384)National High Technology Research and Development Program(863 Program)of China(2012AA062302,2012AA062304)Fundamental Research Funds for the Central Universities of China(N110202001)
文摘In order to clarify the slag system of high Cr2O3 vanadium-titanium magnetite smelting in BF （blast furnace）, the melting properties of slag samples prepared by analytically pure reagents were measured. By means of orthogonal test synthetic weighted score method, the optimal slag for high Cr2O3 vanadium-titanium magnetite was obtained, which contained 10% MgO, 8% TiO2 and 15% Al2O3, with the binary basicity being 1.15. In addition, the effects of basicity, MgO, TiO2 and A12 03 on slag melting properties were investigated by single factor test, and the results showed that, with increasing the basicity or TiO2 content, melting temperature （Tin） increased, whereas initial vis- cosity （r/0） and high temperature viscosity （r/h） decreased. With increasing the MgO content, Tm decreased firstly and then increased. With increasing the Al2 O3 content, Tm increased, and η0 and r/h decreased firstly and then increased.
基金Item Sponsored by State Key Development Program for Basic Research of China(2013CB632603)National Natural Science Foundation of China(51404228)
文摘The oxidation kinetics, structural changes, and elements migration during the oxidation process of the va- nadium-titanium magnetite （VTM） ore were analyzed. Kinetics analysis indicated that the oxidation process was con- trolled by diffusion control and could be divided into interface diffusion and lattice diffusion with apparent activation energy of 99.69 kJ/mol and 144.08 kJ/mol in the range of 800--1000℃, respectively. The surface structure changed with the oxidization temperature as follows： dense surface→nano sized sheets→submicron particles→molten particles. The compact structure changed into porous one because of the elements migration and enrichment. Both Fe and Ti elements migrated in the opposite direction during the oxidation process. The V etement in the raw ore stably existed in the form of V^5＋ state, some vanadium migrated and occupied the tetrahedral sites of the hematite during the oxidation process.
基金supported by the Science and Technology Plan Project of Hebei Province of China(16273703D)the Fundamental Research Funds for the Central Universities(2015ZD24,2017XS123)~~
文摘Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.
基金Funded by the National Natural Science Foundation of China(Nos.51604065,51674084)the Fundamental Funds for the Program of the Science Foundation of Liaoning Province(No.20170540316)
文摘The sintering of chromium-containing vanadium-titanium magnetite using different coke contents was studied through the sintering pot tests, X-ray diffraction analysis and mineralogical phase analysis. Results showed that, as the coke content increased from 3.2% to 4.4%, the liquid phase and combustion zone thickness increased while the vertical sintering rate and ratio of sintered product decreased. In addition, the combustion ratio of exhaust gas also increased with increasing the coke content, indicating that combustion zone temperature also increased, and the excessive the coke content in the sintering process of vanadiumtitanium magnetite is harmful. As the coke content increased, the magnetite, silicates, and perovskite contents of the sintered ore increased while the contents of hematite and calcium ferrite of sintered ore decreased; drum strength decreased, and reduction degradation properties increased while reduction ability decreased. We found that the appropriate coke content for the sintering process is 3.6 wt%.
文摘The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis.According to the thermodynamic results,low-melting-point regions and MgTi2O5primary phase area in the phase diagrams,the suggested titanium slag composition for the present vanadium titanomagnetite metallized pellets should consist of50%TiO2,8%-12%MgO and13%Al2O3(mass fraction)with a binary basicity of0.8-1.2.Finally,the verified smelting experiments were conducted and successful separation of the molten iron from the titanium slag is obtained.The obtained vanadium-containing molten iron contains0.681%V and0.267%Ti,and the obtained titanium slag contains52.21%TiO2(mass fraction),in which MgTi2O5is the primary phase.The titanium resource in the final titanium slag production could be used to produce TiO2pigment by acid leaching methods.
基金financially supported by the Beijing Natural Science Foundation, China (No. 2192056)the National Natural Science Foundation of China (No. 51771179)+1 种基金the National Key R&D Program of China (No. 2018YFC1900505)The financial supports from the Youth Innovation Promotion Association CAS and the CAS Interdisciplinary Innovation Team
文摘Titanium mineral was prepared from vanadium titanomagnetite concentrates by hydrogen reduction and acid leaching.The leaching behaviors of elements like Fe,V,Mn,Al,Mg,Ca,and Si were highly related to the reduction degree.The phase compositions of the reduced materials and the leached residues were analyzed by XRD to identify the effect of reduction degree on the leaching mechanisms.The results showed that the concentrates were reduced to iron metal and titanomagnetite at 800-1000°C for 0.5 h,and the above elements of Fe and impurities were easily leached.Deeper reduction led to the formation of ilmenite and Mg-Al spinel,which hindered leaching.Mg-bearing anosovite appeared in the further reduced materials,and the leaching rates of impurities became much lower.An upgraded titanium mineral with a normalized TiO_(2) grade of 70.3%was achieved by H_(2) reduction at 850°C for 0.5 h and acid leaching,which is a satisfactory Ti resource for the preparation of titanium oxide by sulfate process.
基金Item Sponsored by National High-tech Research and Development Project of China(2012AA062302)Major Program of National Natural Science Foundation of China(51090384)Fundamental Research Funds for the Central Universities of China(N130602003)
文摘To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.
