Gd thin films with different thickness （about 10 nm and 0.5 nm） were deposited on Si（100） by laser molecular beam epitaxy （LMBE）. Thickness dependence of the initial oxidation behaviors of Gd films was studied b...Gd thin films with different thickness （about 10 nm and 0.5 nm） were deposited on Si（100） by laser molecular beam epitaxy （LMBE）. Thickness dependence of the initial oxidation behaviors of Gd films was studied based on the in situ X-ray photoelectron spectroscopy （XPS） and ultraviolet photoelectron spectroscopy （UPS） analysis under ultra-high vacuum （UHV） condition. When the thin film is around 10 urn, the XPS results show that Gd is extremely reactive with oxygen forming Gd oxides and the oxides of Gd are easily hygroscopic. The UPS results show that the Gd 4fhas a double-peak structure and the double-peak structure of Gd 4fevolves into a single-peak feature after exposing to air. When the thickness of the Gd film decreases to about 0.5 urn, the reactivity of Gd film with oxygen is decreased by the diffusion of Si component into Gd layers based on the XPS and UPS results. It is suggested that the silicon atoms segregate at the grain boundaries of Gd film to form a barrier, which block the further diffusion of oxygen and water vapor into the Gd layers.展开更多
Kinetics of oxygen adsorption on single crystal Mn<sub>5</sub>Si<sub>3</sub> （111） surface and initial surface oxidation were investigated. Oxygen chemisorbs dissociatively at room temperatur...Kinetics of oxygen adsorption on single crystal Mn<sub>5</sub>Si<sub>3</sub> （111） surface and initial surface oxidation were investigated. Oxygen chemisorbs dissociatively at room temperature on Mn and Si atoms. A fast oxidation of Si atoms occurs followed by oxidation of Mn atoms at RT. The MnO<sub>2</sub> was reduced by Si atoms and the SiO was oxidized further to SiO<sub>2</sub> during the sample heating.展开更多
The degradation of mechanical properties in superalloys due to high temperature oxidation is unavoidable.In this paper,the initial oxidation(oxidation time less than 3600 s)mechanism of GH4169 superalloy was studied.T...The degradation of mechanical properties in superalloys due to high temperature oxidation is unavoidable.In this paper,the initial oxidation(oxidation time less than 3600 s)mechanism of GH4169 superalloy was studied.The results indicate that the superalloy oxide layer consists of three distinct layers.The outer layer is composed of Cr_(2)O_(3)and Fe_(2)O_(3),the middle layer is a mixture of Nb_(2)O_(5)and MoO_(3),and the inner layer is enriched with Al_(2)O_(3)and Ti_(2)O_(3).Initial oxidation starts preferentially at grain boundaries(GBs).Additionally,the oxide layer of the double aging(DA)alloy is denser.The effects ofγ′andγ″precipitates on the initial oxidation behavior of GH4169 superalloy were studied.The results show thatγ′andγ″precipitates can improve the oxidation resistance of GH4169 superalloy.It provides a research direction for how to improve the oxidation resistance of GH4169 superalloy.展开更多
In the early stage of plasma electrolytic oxidation(PEO),the quick formation of the initial oxide film on the surface of the aluminum substrate is necessary for the subsequent discharge spark process.Furthermore,the c...In the early stage of plasma electrolytic oxidation(PEO),the quick formation of the initial oxide film on the surface of the aluminum substrate is necessary for the subsequent discharge spark process.Furthermore,the compactness of the initial oxide film greatly affects the quality of the PEO coating,but the related mechanisms are not investigated in detail.In this paper,the status of the initial oxide film was adjusted by adding the(NaPO)into the based electrolyte,and then the effect of initial oxide film on the formation of the PEO coating was compared.Microstructure and chemical composition were analyzed by scanning electron microscope,transmission electron microscopy and X-ray photoelectron spectrometer.The compactness of the initial oxide film was characterized by Mott-Schottky plots.The corrosion resistance was measured by electrochemical impedance spectroscopy.The results show that the addition of(NaPO)can promote the co-deposition of phosphide compound into the initial oxide film and improve the film compactness,which is beneficial for the more uniform spark discharge in the later stage.As a result,the addition of(NaPO)is helpful to obtain PEO coating with better performance.展开更多
Acute pancreatitis is an inflammation initially localized in the pancreas,which may be accompanied with severe complications such as multi-organ failure,gastrointestinal hemorrhage and malnutrition.One in ten severe c...Acute pancreatitis is an inflammation initially localized in the pancreas,which may be accompanied with severe complications such as multi-organ failure,gastrointestinal hemorrhage and malnutrition.One in ten severe cases of acute pancreatitis develops systemic inflammatory response syndrome.Despite treatment,acute pancreatitis can be a life-threatening disease as its mortality rate amounts to 5%-10%in general,and up to 35%in cases of severe course.[1]Over the years,the role of oxidative stress展开更多
Polyurethane elastomers derived from 4,4 ' -methylene bis(phenyl isocyanate), butylene glycol and the low oxyethylene moiety content copolyether of tetrahydrofuran and ethylene oxide, obtained by copolymerization ...Polyurethane elastomers derived from 4,4 ' -methylene bis(phenyl isocyanate), butylene glycol and the low oxyethylene moiety content copolyether of tetrahydrofuran and ethylene oxide, obtained by copolymerization using heteropolyacid-ethylene oxide initiator system, were prepared. The polyurethanes exhibited an increased water absorption and much better low temperature resilience, which remained high even at a temperature of -3 degreesC, while that of polyurethane based upon poly(tetramethylene ether) glycol of the 'same molecular weight, i.e. being 2000, and molecular weight distribution, i.e, in the range of 1.4-1.5, starts to decrease dramatically at 5 degreesC.展开更多
Sodium perfluoroalkanesulfinates [Cl(CF_2)n SO_2 Na (1), a, n=4; b, n=6; c, n=8] with the reduction potentials about 0.95-1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)_3·2H_2O, Ce...Sodium perfluoroalkanesulfinates [Cl(CF_2)n SO_2 Na (1), a, n=4; b, n=6; c, n=8] with the reduction potentials about 0.95-1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)_3·2H_2O, Ce(SO_4)_2, HgSO_4 and Co_2O_3 to generate perfluoroalkyl radicals which added to the olefins RCH=CHR′to give two kinds of adducts, namely RCH (R_f) CHXR′(3, X=H; 4, X=OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.展开更多
基金Funded by the Key Laboratory of National Defense Science and Technology(No.9140c6806080c68)
文摘Gd thin films with different thickness （about 10 nm and 0.5 nm） were deposited on Si（100） by laser molecular beam epitaxy （LMBE）. Thickness dependence of the initial oxidation behaviors of Gd films was studied based on the in situ X-ray photoelectron spectroscopy （XPS） and ultraviolet photoelectron spectroscopy （UPS） analysis under ultra-high vacuum （UHV） condition. When the thin film is around 10 urn, the XPS results show that Gd is extremely reactive with oxygen forming Gd oxides and the oxides of Gd are easily hygroscopic. The UPS results show that the Gd 4fhas a double-peak structure and the double-peak structure of Gd 4fevolves into a single-peak feature after exposing to air. When the thickness of the Gd film decreases to about 0.5 urn, the reactivity of Gd film with oxygen is decreased by the diffusion of Si component into Gd layers based on the XPS and UPS results. It is suggested that the silicon atoms segregate at the grain boundaries of Gd film to form a barrier, which block the further diffusion of oxygen and water vapor into the Gd layers.
文摘Kinetics of oxygen adsorption on single crystal Mn<sub>5</sub>Si<sub>3</sub> （111） surface and initial surface oxidation were investigated. Oxygen chemisorbs dissociatively at room temperature on Mn and Si atoms. A fast oxidation of Si atoms occurs followed by oxidation of Mn atoms at RT. The MnO<sub>2</sub> was reduced by Si atoms and the SiO was oxidized further to SiO<sub>2</sub> during the sample heating.
基金supported by the Fundamental Research Program of Shanxi Province in China (20210302124659)the National Natural Science Foundation of China (52204349)
文摘The degradation of mechanical properties in superalloys due to high temperature oxidation is unavoidable.In this paper,the initial oxidation(oxidation time less than 3600 s)mechanism of GH4169 superalloy was studied.The results indicate that the superalloy oxide layer consists of three distinct layers.The outer layer is composed of Cr_(2)O_(3)and Fe_(2)O_(3),the middle layer is a mixture of Nb_(2)O_(5)and MoO_(3),and the inner layer is enriched with Al_(2)O_(3)and Ti_(2)O_(3).Initial oxidation starts preferentially at grain boundaries(GBs).Additionally,the oxide layer of the double aging(DA)alloy is denser.The effects ofγ′andγ″precipitates on the initial oxidation behavior of GH4169 superalloy were studied.The results show thatγ′andγ″precipitates can improve the oxidation resistance of GH4169 superalloy.It provides a research direction for how to improve the oxidation resistance of GH4169 superalloy.
基金supported by the LingChuang Research Project of China National Nuclear Corporation。
文摘In the early stage of plasma electrolytic oxidation(PEO),the quick formation of the initial oxide film on the surface of the aluminum substrate is necessary for the subsequent discharge spark process.Furthermore,the compactness of the initial oxide film greatly affects the quality of the PEO coating,but the related mechanisms are not investigated in detail.In this paper,the status of the initial oxide film was adjusted by adding the(NaPO)into the based electrolyte,and then the effect of initial oxide film on the formation of the PEO coating was compared.Microstructure and chemical composition were analyzed by scanning electron microscope,transmission electron microscopy and X-ray photoelectron spectrometer.The compactness of the initial oxide film was characterized by Mott-Schottky plots.The corrosion resistance was measured by electrochemical impedance spectroscopy.The results show that the addition of(NaPO)can promote the co-deposition of phosphide compound into the initial oxide film and improve the film compactness,which is beneficial for the more uniform spark discharge in the later stage.As a result,the addition of(NaPO)is helpful to obtain PEO coating with better performance.
文摘Acute pancreatitis is an inflammation initially localized in the pancreas,which may be accompanied with severe complications such as multi-organ failure,gastrointestinal hemorrhage and malnutrition.One in ten severe cases of acute pancreatitis develops systemic inflammatory response syndrome.Despite treatment,acute pancreatitis can be a life-threatening disease as its mortality rate amounts to 5%-10%in general,and up to 35%in cases of severe course.[1]Over the years,the role of oxidative stress
基金This work was financially supported by the Doctoral Program Foundation of Institution of High Education.
文摘Polyurethane elastomers derived from 4,4 ' -methylene bis(phenyl isocyanate), butylene glycol and the low oxyethylene moiety content copolyether of tetrahydrofuran and ethylene oxide, obtained by copolymerization using heteropolyacid-ethylene oxide initiator system, were prepared. The polyurethanes exhibited an increased water absorption and much better low temperature resilience, which remained high even at a temperature of -3 degreesC, while that of polyurethane based upon poly(tetramethylene ether) glycol of the 'same molecular weight, i.e. being 2000, and molecular weight distribution, i.e, in the range of 1.4-1.5, starts to decrease dramatically at 5 degreesC.
文摘Sodium perfluoroalkanesulfinates [Cl(CF_2)n SO_2 Na (1), a, n=4; b, n=6; c, n=8] with the reduction potentials about 0.95-1.00V could be oxidized readily with various oxidizing agents such as Mn (OAc)_3·2H_2O, Ce(SO_4)_2, HgSO_4 and Co_2O_3 to generate perfluoroalkyl radicals which added to the olefins RCH=CHR′to give two kinds of adducts, namely RCH (R_f) CHXR′(3, X=H; 4, X=OAc), with good yields depending upon the solvent system used. Different oxidizing agents showed slight variation on the yields of the adducts. The reaction time could be greatly shortened at higher temperature. Thus, this reaction provides a new way for introducing a perfluoroalkyl group into olefinic compounds.
