LaB6 powders were synthesized in large scale by salt-assisted combustion synthesis(CS) with different NaCl diluent contents. The variety of phases, particle size and purity of the powders were investigated using X-ray...LaB6 powders were synthesized in large scale by salt-assisted combustion synthesis(CS) with different NaCl diluent contents. The variety of phases, particle size and purity of the powders were investigated using X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), and transmission electron microscope(TEM). With increase of NaCl content, the adiabatic combustion temperature of the reaction system linearly declines, the average particle size of leached products decreases, the impurity phases are easier to remove, and the products purity enhances obviously. When NaCl content is 40 wt%, the purity of the superfine powders of LaBis more than 98 wt%, and the average particle size is 380 nm.展开更多
Currently,iodine-compatible cathodes for iodine propulsion systems that can provide ampere-level electron currents with a reasonable power consumption are lacking.In this study,a conventional LaB_(6)hollow cathode mad...Currently,iodine-compatible cathodes for iodine propulsion systems that can provide ampere-level electron currents with a reasonable power consumption are lacking.In this study,a conventional LaB_(6)hollow cathode made with iodine-resistant materials was designed and tested in an iodine-compatible vacuum facility.The ignition characteristics,the V-I(Volt-Ampere characteristic)curve,and long steady-state discharge sequence of the iodine hollow cathode were analyzed and compared with those using a krypton propellant.After the experiment,the composition of the cathode emitter was studied by scanning electron microscope and energy-dispersive X-ray spectroscopy(EDS).The results show that ignition takes>10 s to reach a steady state,and the discharge voltage of the iodine was 25-95 V higher than that of krypton.According to the EDS results,this was mainly caused by emitter contamination with iron from the stainless-steel components of the cathode and oxygen from the iodine feed system.The iodine hollow cathode achieved a cumulative 12.5 h stable discharge,with the longest single discharge of 5 h and a 3%change in the inner diameter of the emitter.展开更多
Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding tempera...Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB_(6).Results indicate that the surface oxide layer(with a thickness of(13.4±0.5)nm)of Ti_(6)Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775℃.O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB6powder.As a result of reduced dissolved O content,the slips of mixedanddislocations are effectively accelerated,leading to improved ductility.Moreover,grain refinement,along with the in situ formation of Ti B whiskers and second-phase La_(2)O_(3)particles,enhances the strength of the material.The fabricated MIM Ti6Al4V sample exhibits excellent mechanical properties,achieving an ultimate tensile strength of(967±5)MPa,a yield strength of(866±8)MPa,and an elongation of 21.4%±0.7%.These tensile properties represent some of the best results reported in the literature for MIM Ti_(6)Al4V alloys.This study offers valuable insights into the development of high-performance MIM Ti alloys and other metal materials.展开更多
The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(L...The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(LaB_(6))was introduced to enhance both the forming quality and bio-tribological properties of Ti6Al4V alloy.The results show that adding an appropriate amount of LaB_(6)can reduce defects(pores).The micro structure is obviously refined due to pinning and heterogeneous nucleation effects,and the La_(2)O_(3)and TiB are formed through the in-situ reactions.The sample with 4 wt%LaB_(6)addition exhibits excellent microhardness and bio-tribological properties.Grain refinement,dispersion strengthening and solution strengthening can significantly improve the microhardness,and the bio-tribological properties are further improved when combined with the in-situ network-structured hard TiB whisker(TiBw).This work is expected to provide reference suggestions for the development of additive manufactured titanium alloys and its application in implants.展开更多
基金supported by the National Natural Science Foundation of China(51561020)
文摘LaB6 powders were synthesized in large scale by salt-assisted combustion synthesis(CS) with different NaCl diluent contents. The variety of phases, particle size and purity of the powders were investigated using X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), and transmission electron microscope(TEM). With increase of NaCl content, the adiabatic combustion temperature of the reaction system linearly declines, the average particle size of leached products decreases, the impurity phases are easier to remove, and the products purity enhances obviously. When NaCl content is 40 wt%, the purity of the superfine powders of LaBis more than 98 wt%, and the average particle size is 380 nm.
基金supported by the National Key R&D Program of China(No.2022YFE0204100)the Key Program of University-Enterprise Joint Project of National Natural Science Foundation of China(No.U22B20120).
文摘Currently,iodine-compatible cathodes for iodine propulsion systems that can provide ampere-level electron currents with a reasonable power consumption are lacking.In this study,a conventional LaB_(6)hollow cathode made with iodine-resistant materials was designed and tested in an iodine-compatible vacuum facility.The ignition characteristics,the V-I(Volt-Ampere characteristic)curve,and long steady-state discharge sequence of the iodine hollow cathode were analyzed and compared with those using a krypton propellant.After the experiment,the composition of the cathode emitter was studied by scanning electron microscope and energy-dispersive X-ray spectroscopy(EDS).The results show that ignition takes>10 s to reach a steady state,and the discharge voltage of the iodine was 25-95 V higher than that of krypton.According to the EDS results,this was mainly caused by emitter contamination with iron from the stainless-steel components of the cathode and oxygen from the iodine feed system.The iodine hollow cathode achieved a cumulative 12.5 h stable discharge,with the longest single discharge of 5 h and a 3%change in the inner diameter of the emitter.
基金financially supported by the National Natural Science Foundation of China(Nos.52274359 and 52304379)Beijing Natural Science Foundation,China(No.L212021)+4 种基金China National Postdoctoral Program for Innovative Talents(No.BX20220034)China Postdoctoral Science Foundation(No.2022M720403)Fundamental Research Funds for the Central Universities,China(Nos.FRFTP-19005C1Z and 00007718)AECC University Research Cooperation Project,China(No.HFZL2021CXY021)State Key Lab of Advanced Metals and Materials,University of Science and Technology Beijing,China(Nos.2021Z-03 and 2022Z-14)。
文摘Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB_(6).Results indicate that the surface oxide layer(with a thickness of(13.4±0.5)nm)of Ti_(6)Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775℃.O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB6powder.As a result of reduced dissolved O content,the slips of mixedanddislocations are effectively accelerated,leading to improved ductility.Moreover,grain refinement,along with the in situ formation of Ti B whiskers and second-phase La_(2)O_(3)particles,enhances the strength of the material.The fabricated MIM Ti6Al4V sample exhibits excellent mechanical properties,achieving an ultimate tensile strength of(967±5)MPa,a yield strength of(866±8)MPa,and an elongation of 21.4%±0.7%.These tensile properties represent some of the best results reported in the literature for MIM Ti_(6)Al4V alloys.This study offers valuable insights into the development of high-performance MIM Ti alloys and other metal materials.
基金Project supported by the National Natural Science Foundation of China(52405176)the Guangdong Province Natural Science Foundation(2023A1515011558)+2 种基金the State Key Laboratory of Solid Lubrication Fund(LSL-2204)the Fundamental Research Funds for the Central Universities(N2403019)the Tribology Science Fund of the State Key Laboratory of Tribology in Advanced Equipment(SKLTKF24B15)。
文摘The poor wear resistance limits the applications of Ti6Al4V alloy.The additive manufactured Ti6Al4V alloy,particularly produced in the air,has issues with the poor forming quality.In this study,a rare earth compound(LaB_(6))was introduced to enhance both the forming quality and bio-tribological properties of Ti6Al4V alloy.The results show that adding an appropriate amount of LaB_(6)can reduce defects(pores).The micro structure is obviously refined due to pinning and heterogeneous nucleation effects,and the La_(2)O_(3)and TiB are formed through the in-situ reactions.The sample with 4 wt%LaB_(6)addition exhibits excellent microhardness and bio-tribological properties.Grain refinement,dispersion strengthening and solution strengthening can significantly improve the microhardness,and the bio-tribological properties are further improved when combined with the in-situ network-structured hard TiB whisker(TiBw).This work is expected to provide reference suggestions for the development of additive manufactured titanium alloys and its application in implants.
