The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,inte...The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.展开更多
Paper documents experience severe acidification and embrittlement.Nanocellulose is an excellent reinforcement material for paper documents owing to its compatibility and excellent mechanical strength.However,little re...Paper documents experience severe acidification and embrittlement.Nanocellulose is an excellent reinforcement material for paper documents owing to its compatibility and excellent mechanical strength.However,little research has been conducted on the aging resistance of nanocellulose-reinforced paper.In this study,six types of nanocelluloses were used to reinforce aged paper.The reinforcement and anti-aging performances were evaluated,and the anti-aging mechanism was further clarified.Nanocellulose with a high degree of polymerization can better enhance aged paper,and non-chemical nanocellulose also shows better anti-aging performance,such as nanocellulose prepared by mechanical or biological methods.However,nanocellulose prepared using chemical methods exhibits poor reinforcement and anti-aging performance.This is because it has a small particle size that is not beneficial for physical crosslinking with paper fibers.More importantly,the introduction of acidic or oxidizing groups on nanocellulose accelerates the acid hydrolysis and oxidation rate of paper fibers,especially nanocellulose prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation,which should not be used to protect paper documents.展开更多
Regular physical activity(PA)promotes healthy aging,and activities aiming to increase muscular strength(i.e.,resistance exercise(RE))are important PA modalities for achieving health benefits.Previous meta-analyses dem...Regular physical activity(PA)promotes healthy aging,and activities aiming to increase muscular strength(i.e.,resistance exercise(RE))are important PA modalities for achieving health benefits.Previous meta-analyses demonstrated that both RE^(1) and muscular strength^(2) were associated with mortality benefits,even when RE was performed above the PA targets recommended by current guidelines^(1,3).展开更多
In order to develop economically anti-ultraviolet(UV) aging additives to bitumen and extend the comprehensive utilization of lignin materials, lignosulfonate(LS) was selected to intercalate into layered double hydroxi...In order to develop economically anti-ultraviolet(UV) aging additives to bitumen and extend the comprehensive utilization of lignin materials, lignosulfonate(LS) was selected to intercalate into layered double hydroxides(LDHs), then the LS intercalated LDHs(LS-LDHs) were applied to improve UV aging resistance of bitumen. With the characterization of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, chemical analysis and scanning electron microscopy(SEM), LS was successfully intercalated into the galleries of LDHs. The ultraviolet and visible(UV-vis) absorbance curves showed LS-LDHs had excellent UV absorptive ability from 200 to 400 nm. Thermogravimetry and differential scanning calorimetry(TG-DSC) indicated LS-LDHs could have a good thermal stability during the processing of bitumen. Compared with the LDHs, the LS-LDHs exhibited better performance in UV aging resistance of bitumen.展开更多
By metalloscopy,scanning electron microscope,X-ray diffraction,electron probe,salt water erosion and hot steam erosion,the microstructures and the aging resistance of zinc alloy ZA-27 with different contents of yttriu...By metalloscopy,scanning electron microscope,X-ray diffraction,electron probe,salt water erosion and hot steam erosion,the microstructures and the aging resistance of zinc alloy ZA-27 with different contents of yttrium were studied. The results show that with optimum addition of yttrium in the alloy ZA-27 the fine YAl_3 phase forms. The fine YAl_3 granules can act as the condensation nuclei of α phase and the number of the α phase′s nuclei increases greatly and the growth of the nuclei comes in for restrict during the crystallization and the alloy′s grains become fine and the segregation reduces. In addition,yttrium also combines with zinc and the fine dispersion Y-Zn phase forms which improves grain boundary conditions and the alloy′s aging resistance. But when the content of yttrium is overmuch some YAl_3 granules grow to be lumpy,so the fine and close texture of the alloy′s boundaries is damaged and the proportion of the interface among the phases increase which brings a decline in the alloy′s resistance to corrosion.展开更多
The AlMgSi wires with and without Ce were aged at temperatures 18, 30, 40, 50, 70, 100, 120 and 140 degrees C respectively after quenching from solid solution states, and their resistivity was measured in situ during ...The AlMgSi wires with and without Ce were aged at temperatures 18, 30, 40, 50, 70, 100, 120 and 140 degrees C respectively after quenching from solid solution states, and their resistivity was measured in situ during aging. The results showed that the resistance of the samples aged at the temperatures given above except the one at 140 degrees C was increasing with aging time. The rate of increase was large initially and then reduced gradually. The relative resistance increases Delta R/R(0) of the samples with Ce were smaller than that without Ce under similar conditions. The result assumed to be due to reduction of the dispersion of G. P. zone by Ce.展开更多
The light-aging test method commonly used in the automotive industry is utilized to carry out light- aging research on automotive instrument panel （IP） materials and bumper materials. On one hand, the impacts of com...The light-aging test method commonly used in the automotive industry is utilized to carry out light- aging research on automotive instrument panel （IP） materials and bumper materials. On one hand, the impacts of common light-aging test methods on aging degree of automotive component materials are reviewed; on the other hand, the light-aging resistances of different component materials are compared. The results show that, for light-aging behavior of IP materials, the aging degree of the third test method is not severer than that of the second method, but it is severer than that of the first method. The light-aging resistance of IP material A is al- most the same as that of IP material B. With reference to light-aging behavior of bumper materials, the aging de- gree of three common test methods indicates that the aging degree of the sixth test method is not severer than that of the fourth method, but it is severer than that of the fifth method. The light-aging resistance of bumper material D is superior to that of bumper material C.展开更多
The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. Th...The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. The precipitates of the peak aged alloy include both β＂ and if, but the amount ratio of β＂ to β＂ varies with the aging temperature and time increasing. The precipitates during aging at 175 ℃ are dominated by needle-like β＂ phases （including pre-β＂ phase）, the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 ℃, the ratio of β＂ to β＇ becomes the main factor to influence relative resistivity （Ap） value. The higher the temperature is, the smaller the ratio is, and the faster the Ap value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.展开更多
This study focuses on the effect of oils on rheology and oxidation aging of Styrene-Butadiene-Styrene modified asphalt(SBSMA)in the long term,after reducing one low-temperature Performance Grade(PG)of SBSMA by incorpo...This study focuses on the effect of oils on rheology and oxidation aging of Styrene-Butadiene-Styrene modified asphalt(SBSMA)in the long term,after reducing one low-temperature Performance Grade(PG)of SBSMA by incorporating oils.Two oils,including corn-based bio-oil and re-refined engine oil bottom(REOB),were selected to enhance the low-temperature performance of SBSMA.All samples were subjected to Rolling Thin Film Oven(RTFO)aging and 20-h as well as 40-h Pressure Aging Vessel(PAV20 and PAV40)aging,prior to multiple stress creep recovery(MSCR),frequency sweep and Flourier transform infrared spectroscopy(FTIR)scanning.A good high-temperature performance of oil/SBS modified asphalt blends was reflected in MSCR and PG results,meanwhile non-recoverable creep compliance(Jnr)and recovery(R)were found to share a highly correlated relationship during aging progress.In addition,Glover–Rowe(G–R)parameter and phase angle master curves suggest that the improvement of cracking property mainly came from the softening effect of oils.Adding oils into SBSMA was observed to increase oxidation kinetics,but the blends with oils still exhibited better anti-oxidation aging than the base binder,mainly due to the SBS addition.Bio-oil exhibited an effect of relieving age hardening susceptibility of SBSMA.展开更多
To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructure...To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.展开更多
In this work, the growth kinetics of MX （M - metal, X - C/N） nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitr...In this work, the growth kinetics of MX （M - metal, X - C/N） nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitrides during long-term aging, experiments were performed at 700, 800, 850, and 900℃ for different periods （1, 24, 70, and 100 h）. The precipitation behavior of carbonitrides in specimens subjected to various aging conditions was explored using carbon replicas and transmission electron microscopy （TEM） observations. The corresponding sizes ofMX carbonitrides were measured. The results demonstrates that MX carbonitrides precipitate in type 347H austenitic steel as Nb（C,N）. The coarsening rate constant is time-independent; however, an increase in aging temperature results in an increase in coarsening rate of Nb（C,N）. The coarsening process was analyzed according to the calculated diffusion activation energy of Nb（C,N）. When the aging temperature was 800-900℃, the mean activation energy was 294 kJ·mol -1, and the coarsening behavior was controlled primarily by the diffusion of Nb atoms.展开更多
The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercr...The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.展开更多
The observations of dislocations, substructures and other microstructural details were conducted mainly by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) for 12CrlMoV pearlitic ...The observations of dislocations, substructures and other microstructural details were conducted mainly by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) for 12CrlMoV pearlitic heat-resistant steel. It is shown that during the high temperature long-term aging, the disordered and jumbled phase-transformed dislocations caused by normalized cooling are recovered and rearranged into cell substructures, and then the dislocation density is reduced gradually. Finally a low density linear dislocation configuration and a stabler dislocation network are formed and ferritic grains grow considerably.展开更多
During the post-antibiotic golden age, it has seen a massive antibiotic/antibacterial production and an increase in irrational use of these few existing drugs in the medical and veterinary practice, food industries, t...During the post-antibiotic golden age, it has seen a massive antibiotic/antibacterial production and an increase in irrational use of these few existing drugs in the medical and veterinary practice, food industries, tissue cultures, agriculture and commercial ethanol production globally. The irrational drug use has been further exacerbated by the increased marketing and promotion of these drugs by the pharmaceutical companies thus increasing their accessibility in the public and hence their improper use. The lack of production and introduction of the newer and effective antibiotic/antibacterial drugs in clinical practice in the post-antibiotic golden age has seen an increase in the emergence of the resistant pathogenic bacterial infections creating a significant problem in the global health of humankind. The massive productions of the antibiotic/antibacterial drugs have contributed to the poor disposal of these drugs and hence many of them are discharged in various water bodies contributing to the environmental antibiotic/antibacterial drug pollution. In the environment, these drugs exert pressure on the environmental bacteria by destroying useful bacteria that are responsible for the recycling of the organic matter and as well as promoting the selection of the resistant pathogenic bacteria that can spread in human and animal population thus causing an increase in the observed bacterial disease burden and hence a significant global public health problem. The resistant bacterial diseases lead to the high cost, increased occurrence of adverse drug reactions, prolonged hospitalization, the exposure to the second- and third-line drugs like in MDR-TB and XDR-TB that leads to toxicity and deaths as well as the increased poor production in agriculture and animal industry and commercial ethanol production.展开更多
基金Project(202302AB080024)supported by the Department of Science and Technology of Yunnan Province,China。
文摘The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.
基金supported by the Fundamental Research Funds for the Central Universities of South China University of Technology(SCUT),China(No.2022ZYGXZR106)Science and Technology Plan Special Project of Guangzhou,China(No.GZDD201808).
文摘Paper documents experience severe acidification and embrittlement.Nanocellulose is an excellent reinforcement material for paper documents owing to its compatibility and excellent mechanical strength.However,little research has been conducted on the aging resistance of nanocellulose-reinforced paper.In this study,six types of nanocelluloses were used to reinforce aged paper.The reinforcement and anti-aging performances were evaluated,and the anti-aging mechanism was further clarified.Nanocellulose with a high degree of polymerization can better enhance aged paper,and non-chemical nanocellulose also shows better anti-aging performance,such as nanocellulose prepared by mechanical or biological methods.However,nanocellulose prepared using chemical methods exhibits poor reinforcement and anti-aging performance.This is because it has a small particle size that is not beneficial for physical crosslinking with paper fibers.More importantly,the introduction of acidic or oxidizing groups on nanocellulose accelerates the acid hydrolysis and oxidation rate of paper fibers,especially nanocellulose prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation,which should not be used to protect paper documents.
文摘Regular physical activity(PA)promotes healthy aging,and activities aiming to increase muscular strength(i.e.,resistance exercise(RE))are important PA modalities for achieving health benefits.Previous meta-analyses demonstrated that both RE^(1) and muscular strength^(2) were associated with mortality benefits,even when RE was performed above the PA targets recommended by current guidelines^(1,3).
基金Funded by the National Basic Research Program of China(973 Program)(2014CB932104)the Fundamental Research Funds for the Central Universities(2017-YB-007)
文摘In order to develop economically anti-ultraviolet(UV) aging additives to bitumen and extend the comprehensive utilization of lignin materials, lignosulfonate(LS) was selected to intercalate into layered double hydroxides(LDHs), then the LS intercalated LDHs(LS-LDHs) were applied to improve UV aging resistance of bitumen. With the characterization of X-ray diffraction(XRD), Fourier transform infrared(FTIR) spectroscopy, chemical analysis and scanning electron microscopy(SEM), LS was successfully intercalated into the galleries of LDHs. The ultraviolet and visible(UV-vis) absorbance curves showed LS-LDHs had excellent UV absorptive ability from 200 to 400 nm. Thermogravimetry and differential scanning calorimetry(TG-DSC) indicated LS-LDHs could have a good thermal stability during the processing of bitumen. Compared with the LDHs, the LS-LDHs exhibited better performance in UV aging resistance of bitumen.
文摘By metalloscopy,scanning electron microscope,X-ray diffraction,electron probe,salt water erosion and hot steam erosion,the microstructures and the aging resistance of zinc alloy ZA-27 with different contents of yttrium were studied. The results show that with optimum addition of yttrium in the alloy ZA-27 the fine YAl_3 phase forms. The fine YAl_3 granules can act as the condensation nuclei of α phase and the number of the α phase′s nuclei increases greatly and the growth of the nuclei comes in for restrict during the crystallization and the alloy′s grains become fine and the segregation reduces. In addition,yttrium also combines with zinc and the fine dispersion Y-Zn phase forms which improves grain boundary conditions and the alloy′s aging resistance. But when the content of yttrium is overmuch some YAl_3 granules grow to be lumpy,so the fine and close texture of the alloy′s boundaries is damaged and the proportion of the interface among the phases increase which brings a decline in the alloy′s resistance to corrosion.
文摘The AlMgSi wires with and without Ce were aged at temperatures 18, 30, 40, 50, 70, 100, 120 and 140 degrees C respectively after quenching from solid solution states, and their resistivity was measured in situ during aging. The results showed that the resistance of the samples aged at the temperatures given above except the one at 140 degrees C was increasing with aging time. The rate of increase was large initially and then reduced gradually. The relative resistance increases Delta R/R(0) of the samples with Ce were smaller than that without Ce under similar conditions. The result assumed to be due to reduction of the dispersion of G. P. zone by Ce.
文摘The light-aging test method commonly used in the automotive industry is utilized to carry out light- aging research on automotive instrument panel （IP） materials and bumper materials. On one hand, the impacts of common light-aging test methods on aging degree of automotive component materials are reviewed; on the other hand, the light-aging resistances of different component materials are compared. The results show that, for light-aging behavior of IP materials, the aging degree of the third test method is not severer than that of the second method, but it is severer than that of the first method. The light-aging resistance of IP material A is al- most the same as that of IP material B. With reference to light-aging behavior of bumper materials, the aging de- gree of three common test methods indicates that the aging degree of the sixth test method is not severer than that of the fourth method, but it is severer than that of the fifth method. The light-aging resistance of bumper material D is superior to that of bumper material C.
基金Project(51105139)supported by the National Natural Science Foundation of ChinaProject(2010CB731706)supported by the National Basic Research Program of China
文摘The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy （TEM）. The precipitates of the peak aged alloy include both β＂ and if, but the amount ratio of β＂ to β＂ varies with the aging temperature and time increasing. The precipitates during aging at 175 ℃ are dominated by needle-like β＂ phases （including pre-β＂ phase）, the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 ℃, the ratio of β＂ to β＇ becomes the main factor to influence relative resistivity （Ap） value. The higher the temperature is, the smaller the ratio is, and the faster the Ap value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.
基金found by Science and Technology Research Project of Jiangxi Provincial Department of Education(Grant Nos.GJJ210645,GJJ210623)Key R&D Projects of Xinjiang Uygur Autonomous Region(Grant No.2021B01005)and Science and Technology Project of Jiangxi Provincial Department of Transportation(Grant Nos.2020Z0002,2018Q0030)the financial support from China Scholarship Council and Chang’an University.The special thanks would go to Dr.Yuan Zhang and Dr.Hui Chen,both of who provide the professional training and help.
文摘This study focuses on the effect of oils on rheology and oxidation aging of Styrene-Butadiene-Styrene modified asphalt(SBSMA)in the long term,after reducing one low-temperature Performance Grade(PG)of SBSMA by incorporating oils.Two oils,including corn-based bio-oil and re-refined engine oil bottom(REOB),were selected to enhance the low-temperature performance of SBSMA.All samples were subjected to Rolling Thin Film Oven(RTFO)aging and 20-h as well as 40-h Pressure Aging Vessel(PAV20 and PAV40)aging,prior to multiple stress creep recovery(MSCR),frequency sweep and Flourier transform infrared spectroscopy(FTIR)scanning.A good high-temperature performance of oil/SBS modified asphalt blends was reflected in MSCR and PG results,meanwhile non-recoverable creep compliance(Jnr)and recovery(R)were found to share a highly correlated relationship during aging progress.In addition,Glover–Rowe(G–R)parameter and phase angle master curves suggest that the improvement of cracking property mainly came from the softening effect of oils.Adding oils into SBSMA was observed to increase oxidation kinetics,but the blends with oils still exhibited better anti-oxidation aging than the base binder,mainly due to the SBS addition.Bio-oil exhibited an effect of relieving age hardening susceptibility of SBSMA.
基金financially supported by the Program for National Key Research and Development Plan(No.2017YFB1104000)the National Natural Science Foundation of China(No.51574167)+1 种基金the Liaoning Natural Science Foundation(No.2021-MS-235)the Science and Technology Program of Liaoning Provincial Department of Education(No.LJGD2020010)。
文摘To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.
基金the China National Funds for Distinguished Young Scientists (No.51325401)the National High Technology Research and Development Program of China (No.2015AA042504)the National Natural Science Foundation of China (No.51474156) for financial support
文摘In this work, the growth kinetics of MX （M - metal, X - C/N） nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitrides during long-term aging, experiments were performed at 700, 800, 850, and 900℃ for different periods （1, 24, 70, and 100 h）. The precipitation behavior of carbonitrides in specimens subjected to various aging conditions was explored using carbon replicas and transmission electron microscopy （TEM） observations. The corresponding sizes ofMX carbonitrides were measured. The results demonstrates that MX carbonitrides precipitate in type 347H austenitic steel as Nb（C,N）. The coarsening rate constant is time-independent; however, an increase in aging temperature results in an increase in coarsening rate of Nb（C,N）. The coarsening process was analyzed according to the calculated diffusion activation energy of Nb（C,N）. When the aging temperature was 800-900℃, the mean activation energy was 294 kJ·mol -1, and the coarsening behavior was controlled primarily by the diffusion of Nb atoms.
基金supported by the Science and Technology Program of Sichuan Province,China(No.2013GZX0146)
文摘The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.
基金supported by the Natural Science Foundation of Gansu Province(No.ZS001-A22-046-C).
文摘The observations of dislocations, substructures and other microstructural details were conducted mainly by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) for 12CrlMoV pearlitic heat-resistant steel. It is shown that during the high temperature long-term aging, the disordered and jumbled phase-transformed dislocations caused by normalized cooling are recovered and rearranged into cell substructures, and then the dislocation density is reduced gradually. Finally a low density linear dislocation configuration and a stabler dislocation network are formed and ferritic grains grow considerably.
文摘During the post-antibiotic golden age, it has seen a massive antibiotic/antibacterial production and an increase in irrational use of these few existing drugs in the medical and veterinary practice, food industries, tissue cultures, agriculture and commercial ethanol production globally. The irrational drug use has been further exacerbated by the increased marketing and promotion of these drugs by the pharmaceutical companies thus increasing their accessibility in the public and hence their improper use. The lack of production and introduction of the newer and effective antibiotic/antibacterial drugs in clinical practice in the post-antibiotic golden age has seen an increase in the emergence of the resistant pathogenic bacterial infections creating a significant problem in the global health of humankind. The massive productions of the antibiotic/antibacterial drugs have contributed to the poor disposal of these drugs and hence many of them are discharged in various water bodies contributing to the environmental antibiotic/antibacterial drug pollution. In the environment, these drugs exert pressure on the environmental bacteria by destroying useful bacteria that are responsible for the recycling of the organic matter and as well as promoting the selection of the resistant pathogenic bacteria that can spread in human and animal population thus causing an increase in the observed bacterial disease burden and hence a significant global public health problem. The resistant bacterial diseases lead to the high cost, increased occurrence of adverse drug reactions, prolonged hospitalization, the exposure to the second- and third-line drugs like in MDR-TB and XDR-TB that leads to toxicity and deaths as well as the increased poor production in agriculture and animal industry and commercial ethanol production.
