By selecting flexible polycrystalline Ag as the metallic substrates, highly c axis (001) textured YBCO thin films were fabricated by using a modified magnetron sputtering equipment which can accomplish dynamic de...By selecting flexible polycrystalline Ag as the metallic substrates, highly c axis (001) textured YBCO thin films were fabricated by using a modified magnetron sputtering equipment which can accomplish dynamic deposition and in-situ anneal treatment. The textures of Ag substrates have important effects on forming YBCO films with high critical current densities. Research on the textures of cold rolling Ag at different deformation degrees and recrystallization textures of Ag at different temperatures shows that in plane alignment of YBCO films is difficult to be obtained directly on cold rolling Ag substrates, because of the texture change of Ag during deposition heating of substrates and the strong dependence of J c of YBCO films on grain boundary misorientation angle of substrates. The recrystallization textures with cube (001) and rotated cube (001) in Ag were obtained. Experiments offer a possible prospect for the further research of fabricating sharp biaxially texture in Ag and the following deposition of high J c YBCO films directly on it.展开更多
To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio （PO2/PTiCl4 〉 1）. However, this may lead to the formation of powder instead of fil...To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio （PO2/PTiCl4 〉 1）. However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge （volume-DBD） at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 （PO2/PTiC14 = 2.6） by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.展开更多
The inlet film thickness directly affects film and stress distribution of rolling interfaces. Unsteady factors, such as unsteady back tension, may disturb the inlet film thickness. However, the current models of unste...The inlet film thickness directly affects film and stress distribution of rolling interfaces. Unsteady factors, such as unsteady back tension, may disturb the inlet film thickness. However, the current models of unsteady inlet film thickness lack unsteady disturbance factors and do not take surface topography into consideration. In this paper, based on the hydrodynamic analysis of inlet zone an unsteady rolling film model which concerns the direction of surface topography is built up. Considering the small fluctuation of inlet angle, absolute reduction, reduction ratio, inlet strip thickness and roll radius as the input variables and the fluctuation of inlet film thickness as the output variable, the non-linear relationship between the input and output is discussed. The discussion results show that there is 180° phase difference between the inlet film thickness and the input variables, such as the fluctuant absolute reduction, the fluctuant reduction ratio and non-uniform inlet strip thickness, but there is no phase difference between unsteady roll radius and the output. The inlet angle, the steady roll radius and the direction of surface topography have significant influence on the fluctuant amplitude of unsteady inlet film thickness. This study proposes an analysis method for unsteady inlet film thickness which takes surface topography and new disturbance factors into consideration.展开更多
Carbon nitride thin films were prepared by electron-beam evaporation assisted with nitrogen ion bombardment and TiN/CNx composite films were by unbalanced dc magnetron sputtering, respectively. It was found that the s...Carbon nitride thin films were prepared by electron-beam evaporation assisted with nitrogen ion bombardment and TiN/CNx composite films were by unbalanced dc magnetron sputtering, respectively. It was found that the sputtered films were better than the evaporated films in hardness and adhesion. The experiments of atomic oxygen action, cold welding, friction and wearing were emphasized, and the results proved that the sputtered TiN/CNx composite films were suitable for space application.展开更多
An analytical model for metal rolling in the mixed lubrication regime was developed based on Wilson and Chang’s asperity flattening model and Von Mises homogenous deformation model. A more rigorous average Reynolds e...An analytical model for metal rolling in the mixed lubrication regime was developed based on Wilson and Chang’s asperity flattening model and Von Mises homogenous deformation model. A more rigorous average Reynolds equation was used to calculate the hydrodynamic pressure. The variations of the yield stress with strain were considered in the model. An efficient iteration procedure was developed to solve the contact area, film thickness and hydrodynamic pressure. The model is more practical with fewer assumption and converges quickly. It is applicable to a wider range of rolling regimes. The calculation results using the model agree well with the literature as well as with measured data from a rolling mill.展开更多
Bi2Se3 thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi（NO3）3·5H2O and SeO2 as starting materials in diluted HNO3 solut...Bi2Se3 thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi（NO3）3·5H2O and SeO2 as starting materials in diluted HNO3 solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi2Se3, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi2Se3.展开更多
Lubrication in cold rolling process is used not only to control friction,but also to control surface quality and thermal chamber.Successful cold rolling of strip at high speeds requires an optimum presence of lubrican...Lubrication in cold rolling process is used not only to control friction,but also to control surface quality and thermal chamber.Successful cold rolling of strip at high speeds requires an optimum presence of lubricant film thickness at the contact.In order to have a better control on rolling process the awareness for the prediction and maintenance of desired minimum film thickness.On the basis of learning and summarizing the theories early founded by experts around the world,this paper constructed the mixed lubrication model. This paper investigated the lubrication state variation caused by oil and rolling condition differences by cold rolling experiments.The experiments indicated that oil has a big influence to rolling process,and rolling speed directly influence the lubrication state.展开更多
In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product quality.Macroscopic instability behavior is closely related to interfaci...In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product quality.Macroscopic instability behavior is closely related to interfacial friction-lubrication con-dition which is generally characterized by the friction coefficient.However,with higher and higher speed requirements,the commonly used model of friction coefficient is no longer applicable and accurate.A novel approach is suggested to calculate the speed-dependent friction coefficient,in which the viscosity-pressure-temperature effects of the lubricant,surface roughness states of work rolls and rolled piece are comprehensively involved and the mixed flm lubrication theory is applied.Subsequently,the influences of friction coefficient on the instability of slip and chatter are investigated for a five-stand cold tandem rolling mill.On one side,the critical friction coefficient for each stand is determined by calculating the corresponding slip factor;on the other hand,the friction coefficient varying with rolling speed is combined with the model of theoretical critical rolling speed presented under constant friction coefficient,so that the speed threshold is determined.Furthermore,the stable and unstable regions corresponding to the rear three stands are individually discussed,and the technical strategies are proposed to suppress both slip and chatter frequently occurring in the actual rolling process.展开更多
文摘By selecting flexible polycrystalline Ag as the metallic substrates, highly c axis (001) textured YBCO thin films were fabricated by using a modified magnetron sputtering equipment which can accomplish dynamic deposition and in-situ anneal treatment. The textures of Ag substrates have important effects on forming YBCO films with high critical current densities. Research on the textures of cold rolling Ag at different deformation degrees and recrystallization textures of Ag at different temperatures shows that in plane alignment of YBCO films is difficult to be obtained directly on cold rolling Ag substrates, because of the texture change of Ag during deposition heating of substrates and the strong dependence of J c of YBCO films on grain boundary misorientation angle of substrates. The recrystallization textures with cube (001) and rotated cube (001) in Ag were obtained. Experiments offer a possible prospect for the further research of fabricating sharp biaxially texture in Ag and the following deposition of high J c YBCO films directly on it.
基金supported by National Natural Science Foundation of China(Nos.10835004,51077009)the Fundamental Research Funds for the Central Universities
文摘To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TIC14 should be greater than the stoichiometric ratio （PO2/PTiCl4 〉 1）. However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge （volume-DBD） at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 （PO2/PTiC14 = 2.6） by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.
基金Supported by National Natural Science Foundation of China(Grant No.51175035)PhD Program Foundation of Ministry of Education of China(Grant No.20100006110024)Beijing Higher Education Young Elite Teacher Project of China(Grant No.YETP0367)
文摘The inlet film thickness directly affects film and stress distribution of rolling interfaces. Unsteady factors, such as unsteady back tension, may disturb the inlet film thickness. However, the current models of unsteady inlet film thickness lack unsteady disturbance factors and do not take surface topography into consideration. In this paper, based on the hydrodynamic analysis of inlet zone an unsteady rolling film model which concerns the direction of surface topography is built up. Considering the small fluctuation of inlet angle, absolute reduction, reduction ratio, inlet strip thickness and roll radius as the input variables and the fluctuation of inlet film thickness as the output variable, the non-linear relationship between the input and output is discussed. The discussion results show that there is 180° phase difference between the inlet film thickness and the input variables, such as the fluctuant absolute reduction, the fluctuant reduction ratio and non-uniform inlet strip thickness, but there is no phase difference between unsteady roll radius and the output. The inlet angle, the steady roll radius and the direction of surface topography have significant influence on the fluctuant amplitude of unsteady inlet film thickness. This study proposes an analysis method for unsteady inlet film thickness which takes surface topography and new disturbance factors into consideration.
文摘Carbon nitride thin films were prepared by electron-beam evaporation assisted with nitrogen ion bombardment and TiN/CNx composite films were by unbalanced dc magnetron sputtering, respectively. It was found that the sputtered films were better than the evaporated films in hardness and adhesion. The experiments of atomic oxygen action, cold welding, friction and wearing were emphasized, and the results proved that the sputtered TiN/CNx composite films were suitable for space application.
文摘An analytical model for metal rolling in the mixed lubrication regime was developed based on Wilson and Chang’s asperity flattening model and Von Mises homogenous deformation model. A more rigorous average Reynolds equation was used to calculate the hydrodynamic pressure. The variations of the yield stress with strain were considered in the model. An efficient iteration procedure was developed to solve the contact area, film thickness and hydrodynamic pressure. The model is more practical with fewer assumption and converges quickly. It is applicable to a wider range of rolling regimes. The calculation results using the model agree well with the literature as well as with measured data from a rolling mill.
基金supported by the Major State Basic Research Development Program of China (No.2007CB607500.)
文摘Bi2Se3 thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi（NO3）3·5H2O and SeO2 as starting materials in diluted HNO3 solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi2Se3, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi2Se3.
文摘Lubrication in cold rolling process is used not only to control friction,but also to control surface quality and thermal chamber.Successful cold rolling of strip at high speeds requires an optimum presence of lubricant film thickness at the contact.In order to have a better control on rolling process the awareness for the prediction and maintenance of desired minimum film thickness.On the basis of learning and summarizing the theories early founded by experts around the world,this paper constructed the mixed lubrication model. This paper investigated the lubrication state variation caused by oil and rolling condition differences by cold rolling experiments.The experiments indicated that oil has a big influence to rolling process,and rolling speed directly influence the lubrication state.
基金supported by the National Natural Science Foundation of China(Grant No.51775038).
文摘In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product quality.Macroscopic instability behavior is closely related to interfacial friction-lubrication con-dition which is generally characterized by the friction coefficient.However,with higher and higher speed requirements,the commonly used model of friction coefficient is no longer applicable and accurate.A novel approach is suggested to calculate the speed-dependent friction coefficient,in which the viscosity-pressure-temperature effects of the lubricant,surface roughness states of work rolls and rolled piece are comprehensively involved and the mixed flm lubrication theory is applied.Subsequently,the influences of friction coefficient on the instability of slip and chatter are investigated for a five-stand cold tandem rolling mill.On one side,the critical friction coefficient for each stand is determined by calculating the corresponding slip factor;on the other hand,the friction coefficient varying with rolling speed is combined with the model of theoretical critical rolling speed presented under constant friction coefficient,so that the speed threshold is determined.Furthermore,the stable and unstable regions corresponding to the rear three stands are individually discussed,and the technical strategies are proposed to suppress both slip and chatter frequently occurring in the actual rolling process.
