In an atomic force microscope (AFM), the cantilever probe, probe tip and sample surface form a micro system in which micro contact, elastic deformation, relative sliding and friction occur during scanning with the con...In an atomic force microscope (AFM), the cantilever probe, probe tip and sample surface form a micro system in which micro contact, elastic deformation, relative sliding and friction occur during scanning with the contact mode. In this paper, the energy conversion and dissipation during scanning process in the micro system is investigated based on the Mauges-Daules contact model. A dimensionless stick-slip number $\eta = \sqrt {{{8U_1 h^2 } \mathord{\left/ {\vphantom {{8U_1 h^2 } {\left( {k_\theta R_s^2 } \right)}}} \right. \kern-0em} {\left( {k_\theta R_s^2 } \right)}}} $ is defined to describe the micro stick-slip behavior under AFM. Through numerical simulation of the dynamics of the probe tip, it is shown that AFM lateral force is dependent on the defined stick-slip number. If η<1, lateral force is weak and stick-slip phenomenon disappears. When η=1, the probe tip jumps between the asperities on sample surface, showing stick-slip behavior but without energy dissipation. In the case of η>1, the tip moves off the sticking points with an adhesion hysteresis, resulting in an energy dissipation. Therefore, the stick-slip number can serve as a characteristic parameter. Numerical simulation of AFM lateral force with different stick-slip numbers is in agreement with experimental results. Finally a method to extract frictional force from the AFM lateral force signal is proposed.展开更多
The sticking coefficients of ozone on ice surface and solid solution of sulfate and sulfide were measured over a temperature range from 200K to 260K. Experiments were performed in a horizontal flow tube. Results indi...The sticking coefficients of ozone on ice surface and solid solution of sulfate and sulfide were measured over a temperature range from 200K to 260K. Experiments were performed in a horizontal flow tube. Results indicate that the sticking coefficients of ozone on ice are in the range from 1 3×10 -7 to 2 7×10 -6 , and it will become larger as temperature increases; the sticking coefficients of ozone on eight kinds of 0.1mol/L sulfate doped ice are in the range from 1 8×10 -7 to 6 9×10 -6 ; the sticking coefficients of ozone on four kinds of 0 1 mol/L sulfide doped ice are in the range from 3 2×10 -7 to 2 1×10 -5 . Ozone loss on these particles was evaluated.展开更多
文摘In an atomic force microscope (AFM), the cantilever probe, probe tip and sample surface form a micro system in which micro contact, elastic deformation, relative sliding and friction occur during scanning with the contact mode. In this paper, the energy conversion and dissipation during scanning process in the micro system is investigated based on the Mauges-Daules contact model. A dimensionless stick-slip number $\eta = \sqrt {{{8U_1 h^2 } \mathord{\left/ {\vphantom {{8U_1 h^2 } {\left( {k_\theta R_s^2 } \right)}}} \right. \kern-0em} {\left( {k_\theta R_s^2 } \right)}}} $ is defined to describe the micro stick-slip behavior under AFM. Through numerical simulation of the dynamics of the probe tip, it is shown that AFM lateral force is dependent on the defined stick-slip number. If η<1, lateral force is weak and stick-slip phenomenon disappears. When η=1, the probe tip jumps between the asperities on sample surface, showing stick-slip behavior but without energy dissipation. In the case of η>1, the tip moves off the sticking points with an adhesion hysteresis, resulting in an energy dissipation. Therefore, the stick-slip number can serve as a characteristic parameter. Numerical simulation of AFM lateral force with different stick-slip numbers is in agreement with experimental results. Finally a method to extract frictional force from the AFM lateral force signal is proposed.
文摘The sticking coefficients of ozone on ice surface and solid solution of sulfate and sulfide were measured over a temperature range from 200K to 260K. Experiments were performed in a horizontal flow tube. Results indicate that the sticking coefficients of ozone on ice are in the range from 1 3×10 -7 to 2 7×10 -6 , and it will become larger as temperature increases; the sticking coefficients of ozone on eight kinds of 0.1mol/L sulfate doped ice are in the range from 1 8×10 -7 to 6 9×10 -6 ; the sticking coefficients of ozone on four kinds of 0 1 mol/L sulfide doped ice are in the range from 3 2×10 -7 to 2 1×10 -5 . Ozone loss on these particles was evaluated.
