Equimolar quinary diboride powders,with nominal composition of(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2,were synthesized by boro/carbothermal reduction(BCTR)of oxide mixtures(MOx,M=Ti,Hf,Zr,Nb and Ta)using B4 C as source of B...Equimolar quinary diboride powders,with nominal composition of(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2,were synthesized by boro/carbothermal reduction(BCTR)of oxide mixtures(MOx,M=Ti,Hf,Zr,Nb and Ta)using B4 C as source of B and C in vacuum.By adjusting the B4 C/MOxratios,diboride mixtures without detectable MOxwere obtained at 1600℃,while high-entropy diboride(HEB)powders with particle size of<1μm was obtained at 1800℃.The phase,morphology and solid solution evolution process of the HEB powders during the BCTR process were comprehensively investigated.Although X-ray diffraction pattern indicated the powders synthesized at 1800℃ were in a single-phase Al B2 structure,elemental mappings showed that(Ta,Ti)-rich and(Zr,Nb)-rich solid solution coexisted in the HEB powders.The distribution of niobium and zirconium atoms in HEB was unable to reach uniform until the HEB powders were spark plasma sintered at 2000°C.(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2 ceramics with a relative density of 97.9%were obtained after spark plasma sintering the HEB powders at 2050℃ under 50 MPa.Rapid grain growth was found in this composition when the sintering temperature was increased from 2000 to 2050℃,and the averaged grain size increased from 6.67 to 41.2μm.HEB ceramics sintered at 2000℃ had a Vickers hardness of 22.44±0.56 GPa(under a load of 1 kg),a Young’s modulus of^500 GPa and a fracture toughness of 2.83±0.15 MPa m1/2.This is the first report for obtaining high density HEB ceramics without residual oxide phase,benefiting from the high quality HEB powders obtained.展开更多
Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensiv...Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensive atomic radius difference δ, the mixing enthalpy AH and the mixing entropy AS） of phase composition of the alloys were calculated, and the microstructure and phase compositions of alloys were analyzed by using SEM and XRD. The result shows that only the systems with δ≤2.77 and △H≥-8.8 kJ/mol will form high entropy alloy with simple solid solution. Otherwise, intermetallic compounds will exist in the alloys. So, selection of the type of element has important effects on microstructure and properties of high entropy alloys.展开更多
Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12―200 h. One is ...Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12―200 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12 h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12―200 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12 h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.展开更多
Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of exp...Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of explicit and implicit is preferred to predict the springback. This simulation strategy includes several numerical parameters, such as element type, number of elements through thickness （NEL）, element size, etc. However, the influences of these parameters on spring- back prediction accuracy are not fully understood. Thus, taking the geometrical specification 9.525 mm × 0.508 mm ofa HSTT as the objective, the effects of numerical parameters on prediction accuracy and computation efficiency of springback simulation of HSTT RDB are investigated. The simulated springback results are compared with experimental ones. The main results are： （1） solid and continuum-shell elements predict the experimental results well; （2） for C3DSR elements, NEL of at least 3 is required to obtain reliable results and a relative error of 29% can occur as NEL is varied in the range of 1-3; （3） specifying damping factor typically works well in Abaqus/Emplicit simulation of springback and the springback results are sensitive to the magnitude of damping factor. In addition, the explanations of the effect rules are given and a guideline is added.展开更多
A high-entropy ceramic oxide is used as the cathode for the first time for proton-conducting solid oxide fuel cells(H-SOFCs).The Fe_(0.6)Mn_(0.6)Co_(0.6)Ni_(0.6)Cr_(0.6)O_(4)(FMCNC)high-entropy spinel oxide has been s...A high-entropy ceramic oxide is used as the cathode for the first time for proton-conducting solid oxide fuel cells(H-SOFCs).The Fe_(0.6)Mn_(0.6)Co_(0.6)Ni_(0.6)Cr_(0.6)O_(4)(FMCNC)high-entropy spinel oxide has been successfully prepared,and the in situ chemical stability test demonstrates that the FMCNC material has good stability against CO_(2).The first-principles calculation indicates that the high-entropy structure enhances the properties of the FMCNC material that surpasses their individual components,leading to lower O_(2)adsorption energy for FMCNC than that for the individual components.The HSOFC using the FMCNC cathode reaches an encouraging peak power density(PPD)of 1052 mW·cm^(-2)at 700℃,which is higher than those of the H-SOFCs reported recently.Additional comparison was made between the high-entropy FMCNC cathode and the traditional Mn_(1.6)Cu_(1.4)O_(4)(MCO)spinel cathode without the high-entropy structure,revealing that the formation of the high-entropy material allows the enhanced protonation ability as well as the movement of the O p-band center closer to the Fermi level,thus improving the cathode catalytic activity.As a result,the high-entropy FMCNC has a much-decreased polarization resistance of 0.057Ω·cm^(2)at 700℃,which is half of that for the traditional MCO spinel cathode without the high-entropy design.The excellent performance of the FMCNC cell indicates that the high-entropy design makes a new life for the spinel oxide as the cathode for HSOFCs,offering a novel and promising route for the development of high-performance materials for H-SOFCs.展开更多
Among pharmaceuticals and personal care products released into the aquatic environment, antibiotics are of particular concern, because of their ubiquity and health effects. Although scientists have recently paid more ...Among pharmaceuticals and personal care products released into the aquatic environment, antibiotics are of particular concern, because of their ubiquity and health effects. Although scientists have recently paid more attention to the threat of antibiotics to coastal ecosystems, researchers have often focused on relatively few antibiotics, because of the absence of suitable analytical methods. We have therefore developed a method for the rapid detection of 36 antibiotic residues in coastal waters, including tetracyclines （TCs）, sulfanilamides （SAs）, and quinolones （QLs）. The method consists of solid-phase extraction （SPE） and liquid chromatography-tandem mass spectrometry （LC-MS/MS） analysis, using electrospray ionization （ESI） in positive mode. The SPE was performed with Oasis HLB and Oasis MCX cartridges. Chromatographic separation on a Cr8 column was achieved using a binary eluent containing methanol and water with 0.1% formic acid. Typical recoveries of the analytes ranged from 67.4% to 109.3% at a fortification level of 100 ng/L. The precision of the method, calculated as relative standard deviation （RSD）, was below 14.6% for all the compounds. The limits of detection （LODs） varied from 0.45 pg to 7.97 pg. The method was applied to detemaine the target analytes in coastal waters of the Yellow Sea in Liaoning, China. Among the tested antibiotics, 31 were found in coastal ＇waters, with their concentrations between the LOD and 212.5 ng/L. These data indicate that this method is valid for analysis of antibiotics in coastal waters. The study first reports such a large number of antibiotics along the Yellow Sea coast of Liaoning, and should facilitate future comprehensive evaluation of antibiotics in coastal ecosystems展开更多
基金financially supported by the National Natural Science Foundation of China (51521001 and 51832003)the Fundamental Research Funds for the Central Universities
文摘Equimolar quinary diboride powders,with nominal composition of(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2,were synthesized by boro/carbothermal reduction(BCTR)of oxide mixtures(MOx,M=Ti,Hf,Zr,Nb and Ta)using B4 C as source of B and C in vacuum.By adjusting the B4 C/MOxratios,diboride mixtures without detectable MOxwere obtained at 1600℃,while high-entropy diboride(HEB)powders with particle size of<1μm was obtained at 1800℃.The phase,morphology and solid solution evolution process of the HEB powders during the BCTR process were comprehensively investigated.Although X-ray diffraction pattern indicated the powders synthesized at 1800℃ were in a single-phase Al B2 structure,elemental mappings showed that(Ta,Ti)-rich and(Zr,Nb)-rich solid solution coexisted in the HEB powders.The distribution of niobium and zirconium atoms in HEB was unable to reach uniform until the HEB powders were spark plasma sintered at 2000°C.(Ti0.2 Hf0.2 Zr0.2 Nb0.2 Ta0.2)B2 ceramics with a relative density of 97.9%were obtained after spark plasma sintering the HEB powders at 2050℃ under 50 MPa.Rapid grain growth was found in this composition when the sintering temperature was increased from 2000 to 2050℃,and the averaged grain size increased from 6.67 to 41.2μm.HEB ceramics sintered at 2000℃ had a Vickers hardness of 22.44±0.56 GPa(under a load of 1 kg),a Young’s modulus of^500 GPa and a fracture toughness of 2.83±0.15 MPa m1/2.This is the first report for obtaining high density HEB ceramics without residual oxide phase,benefiting from the high quality HEB powders obtained.
基金Project(HIT.NSRIF.2009090) supported by Natural Scientific Research Innovation Foundation in Harbin Institute of Technology,China
文摘Formation condition of high-entropy alloys with solid solution structure was investigated. Seventeen kinds of the high-entropy alloys with different components were prepared, the influencing factors （the comprehensive atomic radius difference δ, the mixing enthalpy AH and the mixing entropy AS） of phase composition of the alloys were calculated, and the microstructure and phase compositions of alloys were analyzed by using SEM and XRD. The result shows that only the systems with δ≤2.77 and △H≥-8.8 kJ/mol will form high entropy alloy with simple solid solution. Otherwise, intermetallic compounds will exist in the alloys. So, selection of the type of element has important effects on microstructure and properties of high entropy alloys.
基金the National Natural Science Foumndation of China(Grant Nos.10299040 , 40103 003) the Knowleige Innovation Program of the Chinese Acacemy of Sciences(Gant No.RJCX2-SW-No.3).
文摘Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12―200 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12 h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12―200 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12 h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.
基金the National Natural Science Foundation of China (No.51275415)Program for New Century Excellent Talents in University+1 种基金the fund of the State Key Laboratory of Solidifcation Processing in NWPUNatural Science Basic Research Plan in Shaanxi Province (No.2011JQ6004),and the 111 Project (No.B08040) for the support
文摘Significant springback occurs after tube rotary-draw-bending （RDB）, especially for a high-strength Ti-3A1-2.5V tube （HSTT） due to its high ratio of yield strength to Young＇s modulus. The combination scheme of explicit and implicit is preferred to predict the springback. This simulation strategy includes several numerical parameters, such as element type, number of elements through thickness （NEL）, element size, etc. However, the influences of these parameters on spring- back prediction accuracy are not fully understood. Thus, taking the geometrical specification 9.525 mm × 0.508 mm ofa HSTT as the objective, the effects of numerical parameters on prediction accuracy and computation efficiency of springback simulation of HSTT RDB are investigated. The simulated springback results are compared with experimental ones. The main results are： （1） solid and continuum-shell elements predict the experimental results well; （2） for C3DSR elements, NEL of at least 3 is required to obtain reliable results and a relative error of 29% can occur as NEL is varied in the range of 1-3; （3） specifying damping factor typically works well in Abaqus/Emplicit simulation of springback and the springback results are sensitive to the magnitude of damping factor. In addition, the explanations of the effect rules are given and a guideline is added.
基金supported by the National Natural Science Foundation of China(Grant No.51972183)Hundred Youth Talents Program of Hunan and the Startup Funding for Talents at University of South China。
文摘A high-entropy ceramic oxide is used as the cathode for the first time for proton-conducting solid oxide fuel cells(H-SOFCs).The Fe_(0.6)Mn_(0.6)Co_(0.6)Ni_(0.6)Cr_(0.6)O_(4)(FMCNC)high-entropy spinel oxide has been successfully prepared,and the in situ chemical stability test demonstrates that the FMCNC material has good stability against CO_(2).The first-principles calculation indicates that the high-entropy structure enhances the properties of the FMCNC material that surpasses their individual components,leading to lower O_(2)adsorption energy for FMCNC than that for the individual components.The HSOFC using the FMCNC cathode reaches an encouraging peak power density(PPD)of 1052 mW·cm^(-2)at 700℃,which is higher than those of the H-SOFCs reported recently.Additional comparison was made between the high-entropy FMCNC cathode and the traditional Mn_(1.6)Cu_(1.4)O_(4)(MCO)spinel cathode without the high-entropy structure,revealing that the formation of the high-entropy material allows the enhanced protonation ability as well as the movement of the O p-band center closer to the Fermi level,thus improving the cathode catalytic activity.As a result,the high-entropy FMCNC has a much-decreased polarization resistance of 0.057Ω·cm^(2)at 700℃,which is half of that for the traditional MCO spinel cathode without the high-entropy design.The excellent performance of the FMCNC cell indicates that the high-entropy design makes a new life for the spinel oxide as the cathode for HSOFCs,offering a novel and promising route for the development of high-performance materials for H-SOFCs.
基金Supported by Young Scientists Research Program (No. 2009507)the Key Laboratory of Marine Bioactive Substances and Modern Analytical Techniques (No. MBSMAT-2010-04),SOA of China
文摘Among pharmaceuticals and personal care products released into the aquatic environment, antibiotics are of particular concern, because of their ubiquity and health effects. Although scientists have recently paid more attention to the threat of antibiotics to coastal ecosystems, researchers have often focused on relatively few antibiotics, because of the absence of suitable analytical methods. We have therefore developed a method for the rapid detection of 36 antibiotic residues in coastal waters, including tetracyclines （TCs）, sulfanilamides （SAs）, and quinolones （QLs）. The method consists of solid-phase extraction （SPE） and liquid chromatography-tandem mass spectrometry （LC-MS/MS） analysis, using electrospray ionization （ESI） in positive mode. The SPE was performed with Oasis HLB and Oasis MCX cartridges. Chromatographic separation on a Cr8 column was achieved using a binary eluent containing methanol and water with 0.1% formic acid. Typical recoveries of the analytes ranged from 67.4% to 109.3% at a fortification level of 100 ng/L. The precision of the method, calculated as relative standard deviation （RSD）, was below 14.6% for all the compounds. The limits of detection （LODs） varied from 0.45 pg to 7.97 pg. The method was applied to detemaine the target analytes in coastal waters of the Yellow Sea in Liaoning, China. Among the tested antibiotics, 31 were found in coastal ＇waters, with their concentrations between the LOD and 212.5 ng/L. These data indicate that this method is valid for analysis of antibiotics in coastal waters. The study first reports such a large number of antibiotics along the Yellow Sea coast of Liaoning, and should facilitate future comprehensive evaluation of antibiotics in coastal ecosystems
