Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Bruna...Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.展开更多
The ca.1.5 Ga mafic intrusions in the Zhuqing area,predominantly composed of alkaline gabbroic rocks in the Kangdian region of SW China,occur as dykes or irregular small intrusions hosting Fe–Ti–V mineralization.All...The ca.1.5 Ga mafic intrusions in the Zhuqing area,predominantly composed of alkaline gabbroic rocks in the Kangdian region of SW China,occur as dykes or irregular small intrusions hosting Fe–Ti–V mineralization.All of the intrusions that intrude the dolomite or shales of the Mesoproterozoic Heishan Formation of the Huili Group are composed of three cyclic units from the base upward:a marginal cyclic unit,a lower cyclic unit and an upper cyclic unit.The Fe–Ti–V oxide ore bodies are hosted in the lower and upper cyclic units.The textural relationships between minerals in the intrusions suggest that titanomagnetite formed earlier than silicate grains because euhedral magnetite and ilmenite grains were enclosed in clinopyroxene and plagioclase.Both the magnetitess–ilmenitess intergrowths due to subsolidus oxidation–exsolutions and the relative higher V distribution coefficient between magnetite and silicate melts in the gabbros from the Zhuqing area are different from those of other typical Fe–Ti bearing mafic rocks,suggesting that the oxygen fugacity was low in the gabbric rocks from the Zhuqing area.This finding was further confirmed by calculations based on the compositions of magnetite and ilmenite pairs.The clinopyroxene,magnetite and ilmenite in the intrusions from the Zhuqing area had considerably lower Mg O than those of other typical Fe–Ti oxide-rich complexes,suggesting that the titanomagnetite from the intrusion may have crystallized at a relatively late stage of evolution from a more evolved magma.Titanomagnetite first fractionally crystallized and subsequently settled in the lower parts of the magma chamber,where it concentrated and formed Fe–Ti–V oxide ore layers at the bases of the lower and upper cycles.Moreover,the occurrence of multiple Fe-Ti oxide layers alternating with Fe-Ti oxide-bearing silicate layers suggests that multiple pulses of magma were involved in the formation of the intrusions and related Fe-Ti-V oxide deposits in the Zhuqing area.展开更多
The effect of inclusion-induced nucleation on hot-rolled steel base metal was evaluated in comparison with welding heataffected zone(HAZ).Microstructure and mechanical properties of hot-rolled low-carbon steel contain...The effect of inclusion-induced nucleation on hot-rolled steel base metal was evaluated in comparison with welding heataffected zone(HAZ).Microstructure and mechanical properties of hot-rolled low-carbon steel containing Ti–Ca oxide particles were studied.The results showed that inclusions in Ti–Ca deoxidized steel distributed dispersely and were effective for intragranular acicular ferrite nucleation.Under hot rolling and controlled cooling conditions,microstructure in steel base metal was significantly refined and mainly consisted of acicular ferrite and intragranular bainite,which exhibited higher strength and excellent toughness.The microstructural evolution behavior followed the process that acicular ferrite plates divided the austenite grain,intragranular bainite packets formed between interlocking acicular ferrite plates,and the remaining austenite decomposed into fine polygonal ferrite grains.The resultant complex microstructure improved the impact toughness significantly.By comparison,in HAZ microstructure,laminar grain boundary ferrite having similar crystallography orientation showed adverse effect on toughness.展开更多
The Ti base PbO 2 electrode prepared by electrodeposition of PbO 2 on the surface of titanium was used for electro catalytic oxidation of phenol in waste water. The experimental results show that the electrodeposition...The Ti base PbO 2 electrode prepared by electrodeposition of PbO 2 on the surface of titanium was used for electro catalytic oxidation of phenol in waste water. The experimental results show that the electrodeposition of PbO 2 at a higher current density for a short time, then followed by a lower current density can get a compact and combinative PbO 2 layer. The properties of a Ti/PbO 2 electrode with an interlayer of oxide are the best. When this kind of electrode is used to treat phenol containing waste water, the phenol removal rate is higher and the slot voltage is lower. In addition, by using the phenol removal rate as an index, the influences of electrolysis current density, mass transfer condition and pH were studied and the optimal condition was confirmed.展开更多
A thermodynamic model has been built up for the interactions between molten Ti alloys and oxide molding materials in the way of decomposition and solution of molding materials, then the influences on the reaction free...A thermodynamic model has been built up for the interactions between molten Ti alloys and oxide molding materials in the way of decomposition and solution of molding materials, then the influences on the reaction free energy changes have been calculated and discussed.展开更多
Ti6Al4V substrates were anodized in a 0.5 mol/L H_2SO_4 solution at applied voltages of 90-140 V.A hydroxyapatite-titanium oxide（HA-TiO2）coating was then deposited on the anodized Ti6Al4 V substrates via a hydrother...Ti6Al4V substrates were anodized in a 0.5 mol/L H_2SO_4 solution at applied voltages of 90-140 V.A hydroxyapatite-titanium oxide（HA-TiO2）coating was then deposited on the anodized Ti6Al4 V substrates via a hydrothermal-electrochemicalmethod at a constant current.The obtained films and coatings were characterized by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fourier-transform infrared spectrometry.The microstructures of the porous films on the Ti6Al4 V substrates were studied to investigate the effect of the anodizing voltage on the phase and morphology of the HATiO_2 coating.The results indicated that both the phase composition and the morphology of the coatings were significantly influenced by changes in the anodizing voltage.HA-TiO_2 was directly precipitated onto the surface of the substrate when the applied voltage was between 110 and 140 V.The coatings had a gradient structure and the HA exhibited both needle-like and cotton-like structures.The amount of cotton-like HA structures decreased with an increase in voltage from 90 to 120 V,and then increased slightly when the voltage was higher than 120 V.The orientation index of the（002）plane of the coating was at a minimum when the Ti6Al4 V substrate was pretreated at 120 V.展开更多
Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effe...Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.展开更多
The morphology and structure of the oxide films of Ti in H3PO4 were investigated by galvanos tatic anodization, SEM and XRD. The oxide film grew from some pores in the grooves to layered microdomains as increasing ano...The morphology and structure of the oxide films of Ti in H3PO4 were investigated by galvanos tatic anodization, SEM and XRD. The oxide film grew from some pores in the grooves to layered microdomains as increasing anodizing voltage. The crystallinity of the oxide films decreased with the increase of the concentration of the electrolyte. The model has been proposed for the growth of the oxide films by two steps, i.e. by uniform thickening and by local deposition.展开更多
Economic concentrations of Fe–Ti oxides occurring as massive layers in the middle and upper parts of the Hongge intrusion are different from other layered intrusions(Panzhihua and Baima) in the Emeishan large igneous...Economic concentrations of Fe–Ti oxides occurring as massive layers in the middle and upper parts of the Hongge intrusion are different from other layered intrusions(Panzhihua and Baima) in the Emeishan large igneous province, SW China. This paper reports on the new mineral compositions of magnetite and ilmenite for selected cumulate rocks and clinopyroxene and plagioclase for basalts. We use these data to estimate the oxidation state of parental magmas and during ore formation to constrain the factors leading to the abundant accumulation of Fe–Ti oxides involved with the Hongge layered intrusion. The results show that the oxygen fugacities of parental magma are in the range of FMQ-1.56 to FMQ+0.14, and the oxygen fugacities during the ore formation of the Fe–Ti oxides located in the lower olivine clinopyroxenite zone(LOZ) and the middle clinopyroxenite zone(MCZ) of the Hongge intrusion are in the range of FMQ-1.29 to FMQ-0.2 and FMQ-0.49 to FMQ+0.82, respectively.The MELTS model demonstrates that, as the oxygen fugacity increases from the FMQ-1 to FMQ+1, the proportion of crystallization magnetite increases from 11 % to 16 % and the crystallization temperature of the Fe–Ti oxides advances from 1134 to 1164 °C. The moderate oxygen fugacities for the Hongge MCZ indicate that the oxygen fugacity was not the only factor affecting the crystallization of Fe–Ti oxides. We speculated that theinitial anhydrous magma that arrived at the Hongge shallow magma chamber became hydrous by attracting the H_2O of the strata. In combination with increasing oxygen fugacities from the LOZ(FMQ-1.29 to FMQ-0.2) to the MCZ(FMQ-0.49 to FMQ+0.82), these two factors probably account for the large-scale Fe–Ti oxide ore layers in the MCZ of the Hongge intrusion.展开更多
A promising duplex coating was prepared by microarc oxidation（MAO） and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling...A promising duplex coating was prepared by microarc oxidation（MAO） and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature（80 ℃）. Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.展开更多
The oxidation tests of Ti_3AlC_2 were conducted at 1100 and 1200？C in air for 48 and 360 h, respectively,and the effects of high temperature oxidation on the flexural strength and hardness of Ti_3AlC_2 were investiga...The oxidation tests of Ti_3AlC_2 were conducted at 1100 and 1200？C in air for 48 and 360 h, respectively,and the effects of high temperature oxidation on the flexural strength and hardness of Ti_3AlC_2 were investigated. The microstructure, grain size and phase compositions of Ti_3AlC_2 substrate didn＇t change after oxidation, hence the oxide removed Ti_3AlC_2 substrate maintained its initial flexural strength and hardness. However, the flexural strength of oxide retained Ti_3AlC_2 decreased by about 5%. Acoustic emission monitoring indicated that during the process of three-point bending test, the formed Al_2O_3 scale on Ti_3AlC_2 surface fractured firstly in a cleavage manner, then the substrate/oxide interface cracked,and finally the Ti_3AlC_2 substrate fractured. The mechanical degradation was caused by the preferential formation of cracks in brittle Al_2O_3 scale as well as at defective and lacunose grain boundaries of the substrate where stress concentration generated. The mechanical degradation was insensitive to oxidation temperature and time in the present conditions. In addition, the surface hardness increased significantly after oxidation due to the formed hard Al_2O_3 scale on the surface of Ti_3AlC_2 substrate.展开更多
Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) ...Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the morphology and composition of the films fabricated in the electrolytes with and without addition of Si C nanoparticles. Results show that Si C particles can be successfully incorporated into the oxide film during the anodizing process and preferentially concentrate within internal cavities and micro-cracks. The ball-on-disk sliding tests indicate that Si C-containing oxide films register much lower wear rate than the oxide films without Si C under dry sliding condition. Si C particles are likely to melt and then are oxidized by frictional heat during sliding tests. Potentiodynamic polarization behavior reveals that the anodized alloy with Si C nanoparticles results in a reduction in passive current density to about 1.54×10-8 A/cm2, which is more than two times lower than that of the Ti O2 film(3.73×10-8 A/cm2). The synthesized composite film has good anti-wear and anti-corrosion properties and the growth mechanism of nanocomposite film is also discussed.展开更多
基金Project supported by the National Key R&D Program of China(2018YFB0605002)。
文摘Alkali metal K in exhaust gas has a deactivation effect on NH_(3)-SCR catalysts.In this work,it is discovered that the addition of Ho on CeTi catalyst can remarkably strengthen its K tolerance.The conclusions of Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),NH_(3) temperature programmed desorption(NH_(3)-TPD)and H_(2)temperature programmed reduction(H_(2)-TPR)analyses demonstrate that the enhancement of K resistance mainly originates from its stronger surface acidity and redox capability,the higher concentration of Ce^(3+)species and surface chemisorbed oxygen.In situ DRIFT analysis reveals that the introduction of Ho on CeTi can remarkably improve the adsorption of NH_(3) and NO_(x) species on catalyst surface,accompanied by the intensified reactivity of ad-NH_(3) species,which should also administer to improve the K resistance.
基金supported by the National Natural Science Foundation of China(Grants 41403044,41273049,41572074)
文摘The ca.1.5 Ga mafic intrusions in the Zhuqing area,predominantly composed of alkaline gabbroic rocks in the Kangdian region of SW China,occur as dykes or irregular small intrusions hosting Fe–Ti–V mineralization.All of the intrusions that intrude the dolomite or shales of the Mesoproterozoic Heishan Formation of the Huili Group are composed of three cyclic units from the base upward:a marginal cyclic unit,a lower cyclic unit and an upper cyclic unit.The Fe–Ti–V oxide ore bodies are hosted in the lower and upper cyclic units.The textural relationships between minerals in the intrusions suggest that titanomagnetite formed earlier than silicate grains because euhedral magnetite and ilmenite grains were enclosed in clinopyroxene and plagioclase.Both the magnetitess–ilmenitess intergrowths due to subsolidus oxidation–exsolutions and the relative higher V distribution coefficient between magnetite and silicate melts in the gabbros from the Zhuqing area are different from those of other typical Fe–Ti bearing mafic rocks,suggesting that the oxygen fugacity was low in the gabbric rocks from the Zhuqing area.This finding was further confirmed by calculations based on the compositions of magnetite and ilmenite pairs.The clinopyroxene,magnetite and ilmenite in the intrusions from the Zhuqing area had considerably lower Mg O than those of other typical Fe–Ti oxide-rich complexes,suggesting that the titanomagnetite from the intrusion may have crystallized at a relatively late stage of evolution from a more evolved magma.Titanomagnetite first fractionally crystallized and subsequently settled in the lower parts of the magma chamber,where it concentrated and formed Fe–Ti–V oxide ore layers at the bases of the lower and upper cycles.Moreover,the occurrence of multiple Fe-Ti oxide layers alternating with Fe-Ti oxide-bearing silicate layers suggests that multiple pulses of magma were involved in the formation of the intrusions and related Fe-Ti-V oxide deposits in the Zhuqing area.
基金This work was supported by the National Natural Science Foundation of China(U1860201 and 51904070)China Postdoctoral Science Foundation(2018M631804)the Fundamental Research Funds for the Central Universities(N170703005).
文摘The effect of inclusion-induced nucleation on hot-rolled steel base metal was evaluated in comparison with welding heataffected zone(HAZ).Microstructure and mechanical properties of hot-rolled low-carbon steel containing Ti–Ca oxide particles were studied.The results showed that inclusions in Ti–Ca deoxidized steel distributed dispersely and were effective for intragranular acicular ferrite nucleation.Under hot rolling and controlled cooling conditions,microstructure in steel base metal was significantly refined and mainly consisted of acicular ferrite and intragranular bainite,which exhibited higher strength and excellent toughness.The microstructural evolution behavior followed the process that acicular ferrite plates divided the austenite grain,intragranular bainite packets formed between interlocking acicular ferrite plates,and the remaining austenite decomposed into fine polygonal ferrite grains.The resultant complex microstructure improved the impact toughness significantly.By comparison,in HAZ microstructure,laminar grain boundary ferrite having similar crystallography orientation showed adverse effect on toughness.
文摘The Ti base PbO 2 electrode prepared by electrodeposition of PbO 2 on the surface of titanium was used for electro catalytic oxidation of phenol in waste water. The experimental results show that the electrodeposition of PbO 2 at a higher current density for a short time, then followed by a lower current density can get a compact and combinative PbO 2 layer. The properties of a Ti/PbO 2 electrode with an interlayer of oxide are the best. When this kind of electrode is used to treat phenol containing waste water, the phenol removal rate is higher and the slot voltage is lower. In addition, by using the phenol removal rate as an index, the influences of electrolysis current density, mass transfer condition and pH were studied and the optimal condition was confirmed.
基金This work was supported by Postdoctoral Foundation of Northwestern Polytechnical University and Science Research FOundation o
文摘A thermodynamic model has been built up for the interactions between molten Ti alloys and oxide molding materials in the way of decomposition and solution of molding materials, then the influences on the reaction free energy changes have been calculated and discussed.
基金Funded in part by the Key Laboratory of Inorginic Coating MaterialsChinese Academy of Sciences(No.KLICM-2014-11)the Shanghai Municipal Natural Science Foundation Sponsored by Shanghai Municipal Science and Technology Commissions(No.15ZR1428300)
文摘Ti6Al4V substrates were anodized in a 0.5 mol/L H_2SO_4 solution at applied voltages of 90-140 V.A hydroxyapatite-titanium oxide（HA-TiO2）coating was then deposited on the anodized Ti6Al4 V substrates via a hydrothermal-electrochemicalmethod at a constant current.The obtained films and coatings were characterized by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fourier-transform infrared spectrometry.The microstructures of the porous films on the Ti6Al4 V substrates were studied to investigate the effect of the anodizing voltage on the phase and morphology of the HATiO_2 coating.The results indicated that both the phase composition and the morphology of the coatings were significantly influenced by changes in the anodizing voltage.HA-TiO_2 was directly precipitated onto the surface of the substrate when the applied voltage was between 110 and 140 V.The coatings had a gradient structure and the HA exhibited both needle-like and cotton-like structures.The amount of cotton-like HA structures decreased with an increase in voltage from 90 to 120 V,and then increased slightly when the voltage was higher than 120 V.The orientation index of the（002）plane of the coating was at a minimum when the Ti6Al4 V substrate was pretreated at 120 V.
文摘Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.
基金This work was supported by. tile grant uf Post-Doc.Program, Kylingpook National tjllivcrsity (if)IN)
文摘The morphology and structure of the oxide films of Ti in H3PO4 were investigated by galvanos tatic anodization, SEM and XRD. The oxide film grew from some pores in the grooves to layered microdomains as increasing anodizing voltage. The crystallinity of the oxide films decreased with the increase of the concentration of the electrolyte. The model has been proposed for the growth of the oxide films by two steps, i.e. by uniform thickening and by local deposition.
基金supported by the National 973 Program of China (2012CB416804 and 2014CB440906)CAS/SAFEA International Partnership Program for Creative Research Teams (KZZD-EW-TZ-20)National Natural Sciences Foundations of China (41473051) to Tao yan
文摘Economic concentrations of Fe–Ti oxides occurring as massive layers in the middle and upper parts of the Hongge intrusion are different from other layered intrusions(Panzhihua and Baima) in the Emeishan large igneous province, SW China. This paper reports on the new mineral compositions of magnetite and ilmenite for selected cumulate rocks and clinopyroxene and plagioclase for basalts. We use these data to estimate the oxidation state of parental magmas and during ore formation to constrain the factors leading to the abundant accumulation of Fe–Ti oxides involved with the Hongge layered intrusion. The results show that the oxygen fugacities of parental magma are in the range of FMQ-1.56 to FMQ+0.14, and the oxygen fugacities during the ore formation of the Fe–Ti oxides located in the lower olivine clinopyroxenite zone(LOZ) and the middle clinopyroxenite zone(MCZ) of the Hongge intrusion are in the range of FMQ-1.29 to FMQ-0.2 and FMQ-0.49 to FMQ+0.82, respectively.The MELTS model demonstrates that, as the oxygen fugacity increases from the FMQ-1 to FMQ+1, the proportion of crystallization magnetite increases from 11 % to 16 % and the crystallization temperature of the Fe–Ti oxides advances from 1134 to 1164 °C. The moderate oxygen fugacities for the Hongge MCZ indicate that the oxygen fugacity was not the only factor affecting the crystallization of Fe–Ti oxides. We speculated that theinitial anhydrous magma that arrived at the Hongge shallow magma chamber became hydrous by attracting the H_2O of the strata. In combination with increasing oxygen fugacities from the LOZ(FMQ-1.29 to FMQ-0.2) to the MCZ(FMQ-0.49 to FMQ+0.82), these two factors probably account for the large-scale Fe–Ti oxide ore layers in the MCZ of the Hongge intrusion.
基金financially supported by the Zhejiang Province Science and Technology Program (No. 2014C31126)
文摘A promising duplex coating was prepared by microarc oxidation（MAO） and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature（80 ℃）. Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.
基金financial support of the project from the National Natural Science Foundation of China (Nos. 51571205 and 51271191)
文摘The oxidation tests of Ti_3AlC_2 were conducted at 1100 and 1200？C in air for 48 and 360 h, respectively,and the effects of high temperature oxidation on the flexural strength and hardness of Ti_3AlC_2 were investigated. The microstructure, grain size and phase compositions of Ti_3AlC_2 substrate didn＇t change after oxidation, hence the oxide removed Ti_3AlC_2 substrate maintained its initial flexural strength and hardness. However, the flexural strength of oxide retained Ti_3AlC_2 decreased by about 5%. Acoustic emission monitoring indicated that during the process of three-point bending test, the formed Al_2O_3 scale on Ti_3AlC_2 surface fractured firstly in a cleavage manner, then the substrate/oxide interface cracked,and finally the Ti_3AlC_2 substrate fractured. The mechanical degradation was caused by the preferential formation of cracks in brittle Al_2O_3 scale as well as at defective and lacunose grain boundaries of the substrate where stress concentration generated. The mechanical degradation was insensitive to oxidation temperature and time in the present conditions. In addition, the surface hardness increased significantly after oxidation due to the formed hard Al_2O_3 scale on the surface of Ti_3AlC_2 substrate.
基金Project(51271012)supported by the National Natural Science Foundation of China
文摘Anodized composite films containing Si C nanoparticles were synthesized on Ti6Al4 V alloy by anodic oxidation procedure in C4O6H4Na2 electrolyte. Scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS) were employed to characterize the morphology and composition of the films fabricated in the electrolytes with and without addition of Si C nanoparticles. Results show that Si C particles can be successfully incorporated into the oxide film during the anodizing process and preferentially concentrate within internal cavities and micro-cracks. The ball-on-disk sliding tests indicate that Si C-containing oxide films register much lower wear rate than the oxide films without Si C under dry sliding condition. Si C particles are likely to melt and then are oxidized by frictional heat during sliding tests. Potentiodynamic polarization behavior reveals that the anodized alloy with Si C nanoparticles results in a reduction in passive current density to about 1.54×10-8 A/cm2, which is more than two times lower than that of the Ti O2 film(3.73×10-8 A/cm2). The synthesized composite film has good anti-wear and anti-corrosion properties and the growth mechanism of nanocomposite film is also discussed.
