The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydroth...The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydrothermal stripping with water from iron-loaded organic phase of naphthenic acidisooctyl alcoholkerosene, such as initial concentrations of iron and naphthenic acid, concentration of Fe2O3 搒eed, temperature and time, were investigated. Based on the experimental results, the rate equation was established. Nano-ferric oxide powders were obtained by the technique of hydrothermal stripping from the iron-loaded organic phase. The results suggest that the heterogeneous hydrothermal stripping proceeds in 3 steps: adsorption of naphthenic acid dimers and naphthenic complex of iron onto the surface of seed? hydrolysis of adsorbed complex of iron, and condensation of hydrolyzed complex. The process activation energy is 115 kJ/mol and the heterogeneous hydrothermal stripping is controlled by a chemical reaction (the hydrolysis of naphthenic complex of iron).展开更多
The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the sur...The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces＇ micro-hardness profiles. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were used to observe the wom surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20℃, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20℃ is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity （TRIP） phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.展开更多
Laser cladding technique has been applied to renovate some partially-damaged (or worn) components with Fe, Ni, Co-base alloys, hence to improve their hardness values and wear resistance successfully in previous report...Laser cladding technique has been applied to renovate some partially-damaged (or worn) components with Fe, Ni, Co-base alloys, hence to improve their hardness values and wear resistance successfully in previous reports. But for some punching or shearing cast iron dies damaged or worn in automobile manufacture, the renovated surfaces also bear some impact loading. Therefore, a small-energy and multi-impact (SEMI) test was designed to investigate the fracture behaviour of renovated cast iron dies achieved by laser cladding of Fe and Ni-base alloys under SEMI loading to meet above requirement. observations show that the fracture took place in the substrate near to the substrate/coating interface rather than at the interface. The tempering temperature has a great influence on the cycles to fracture of laser-clad samples under SEMl loading, i.e. the low tempering temperature of 300℃ gives a maximum cycle to fracture, while a higher tempering temperature of 400℃ has a minimum. Furthermore, the fracture mechanism has also been discussed in present study展开更多
Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron bicrystals.In this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3 [110] asymmetry ti...Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron bicrystals.In this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3 [110] asymmetry tilt grain boundary(ATGB) under shock-loading is performed. We find that the shock response of asymmetric grain boundaries is quite different from that of symmetric grain boundaries. Especially, our simulation proves that shock can induce migration of asymmetric grain boundary in iron. We also find that the shape and local structure of grain boundary(GB) would not be changed during shock-induced migration of Σ3 [110] ATGB, while the phase transformation near the GB could affect migration of GB. The most important discovery is that the shock-induced shear stress difference between two sides of GB is the key factor leading to GB migration. Our simulation involves a variety of piston velocities, and the migration of GB seems to be less sensitive to the piston velocity. Finally, the kinetics of GB migration at lattice level is discussed. Our work firstly reports the simulation of shock-induced grain boundary migration in iron. It is of great significance to the theory of GB migration and material engineering.展开更多
A retrospective analysis on the assessment of the level of p65 component of the transcription factor Nuclear Factor Kappa B (NF-kB p65) in the nuclear extract of lipopolysaccharide stimulated peripheral blood mon-onuc...A retrospective analysis on the assessment of the level of p65 component of the transcription factor Nuclear Factor Kappa B (NF-kB p65) in the nuclear extract of lipopolysaccharide stimulated peripheral blood mon-onuclear cells (PBMCs) of remunerated blood donors with HIV-1 infection revealed NF-kB p65 to be significantly higher in the subgroup with history of oral iron intake compared to the HIV-1 infected subgroup without such history. The level of NF-kB p65 in iron consuming subgroup of HIV-1 positive donors showed positive correlation with the serum ferritin level and with the rate of increase in viral load. The NF-kB p65 level also showed positive correlation with the level of superoxide produced by cultured Monocyte derived macrophages (MDMs) as well as with the levels of the immune activation markers viz. Tumour necrosis factor alpha (TNF-α) and two of its soluble markers i.e. Tumour necrosis factor receptor types one and two (TNFRI and TNFRII) reported in earlier studies in the same subgroup. The opposing roles of NF-kB in situation of iron overload in HIV-1 infection i.e. disease enhancement on one hand and facilitation of effective antiretroviral therapy through activation of HIV-1 in the latently infected cells on other hand suggest the need for further research to weigh benefits and risks of iron therapy in situations where iron deficiency in HIV-1 infection may be a serious consideration.展开更多
基金Supported by the National Natural Science Foundation of China (No.: 59934080)
文摘The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydrothermal stripping with water from iron-loaded organic phase of naphthenic acidisooctyl alcoholkerosene, such as initial concentrations of iron and naphthenic acid, concentration of Fe2O3 搒eed, temperature and time, were investigated. Based on the experimental results, the rate equation was established. Nano-ferric oxide powders were obtained by the technique of hydrothermal stripping from the iron-loaded organic phase. The results suggest that the heterogeneous hydrothermal stripping proceeds in 3 steps: adsorption of naphthenic acid dimers and naphthenic complex of iron onto the surface of seed? hydrolysis of adsorbed complex of iron, and condensation of hydrolyzed complex. The process activation energy is 115 kJ/mol and the heterogeneous hydrothermal stripping is controlled by a chemical reaction (the hydrolysis of naphthenic complex of iron).
文摘The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces＇ micro-hardness profiles. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were used to observe the wom surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20℃, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20℃ is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity （TRIP） phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.
文摘Laser cladding technique has been applied to renovate some partially-damaged (or worn) components with Fe, Ni, Co-base alloys, hence to improve their hardness values and wear resistance successfully in previous reports. But for some punching or shearing cast iron dies damaged or worn in automobile manufacture, the renovated surfaces also bear some impact loading. Therefore, a small-energy and multi-impact (SEMI) test was designed to investigate the fracture behaviour of renovated cast iron dies achieved by laser cladding of Fe and Ni-base alloys under SEMI loading to meet above requirement. observations show that the fracture took place in the substrate near to the substrate/coating interface rather than at the interface. The tempering temperature has a great influence on the cycles to fracture of laser-clad samples under SEMl loading, i.e. the low tempering temperature of 300℃ gives a maximum cycle to fracture, while a higher tempering temperature of 400℃ has a minimum. Furthermore, the fracture mechanism has also been discussed in present study
基金Project supported by the Fundamental Research for the Central Universities of Chinathe National Key Laboratory Project of Shock Wave and Detonation Physics of China+4 种基金the Science and Technology Foundation of National Key Laboratory of Shock Wave and Detonation Physics of Chinathe National Key R&D Program of China(Grant No.2017YFB0202303)the National Natural Science Foundation of China(Grant Nos.51871094,51871095,51571088,NSFC-NSAF U1530151,and U1830138)the Natural Science Foundation of Hunan Province of China(Grant No.2018JJ2036)the Science Challenge Project of China(Grant No.TZ2016001)
文摘Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron bicrystals.In this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3 [110] asymmetry tilt grain boundary(ATGB) under shock-loading is performed. We find that the shock response of asymmetric grain boundaries is quite different from that of symmetric grain boundaries. Especially, our simulation proves that shock can induce migration of asymmetric grain boundary in iron. We also find that the shape and local structure of grain boundary(GB) would not be changed during shock-induced migration of Σ3 [110] ATGB, while the phase transformation near the GB could affect migration of GB. The most important discovery is that the shock-induced shear stress difference between two sides of GB is the key factor leading to GB migration. Our simulation involves a variety of piston velocities, and the migration of GB seems to be less sensitive to the piston velocity. Finally, the kinetics of GB migration at lattice level is discussed. Our work firstly reports the simulation of shock-induced grain boundary migration in iron. It is of great significance to the theory of GB migration and material engineering.
文摘A retrospective analysis on the assessment of the level of p65 component of the transcription factor Nuclear Factor Kappa B (NF-kB p65) in the nuclear extract of lipopolysaccharide stimulated peripheral blood mon-onuclear cells (PBMCs) of remunerated blood donors with HIV-1 infection revealed NF-kB p65 to be significantly higher in the subgroup with history of oral iron intake compared to the HIV-1 infected subgroup without such history. The level of NF-kB p65 in iron consuming subgroup of HIV-1 positive donors showed positive correlation with the serum ferritin level and with the rate of increase in viral load. The NF-kB p65 level also showed positive correlation with the level of superoxide produced by cultured Monocyte derived macrophages (MDMs) as well as with the levels of the immune activation markers viz. Tumour necrosis factor alpha (TNF-α) and two of its soluble markers i.e. Tumour necrosis factor receptor types one and two (TNFRI and TNFRII) reported in earlier studies in the same subgroup. The opposing roles of NF-kB in situation of iron overload in HIV-1 infection i.e. disease enhancement on one hand and facilitation of effective antiretroviral therapy through activation of HIV-1 in the latently infected cells on other hand suggest the need for further research to weigh benefits and risks of iron therapy in situations where iron deficiency in HIV-1 infection may be a serious consideration.
