Reactive and Inelastic Scattering Dynamics of Hyperthermal O and O2 from a Carbon Fiber Network

The reactive and inelastic scattering dynamics of ground-state atomic and molecular oxygen from a carbon fiber network at 1023-1823 K was investigated with a molecular beam-surface scattering technique. A molecular beam containing hyperthermal O and O₂ with a mole ratio of 0.92:0.08 and nominal velocity of 8 km s^-1 was directed at the network, and time-of-flight distributions of the scattered products were collected at various angles with the use of a rotatable mass spectrometer detector. O atoms exhibited both impulsive scattering (IS) and thermal desorption (TD) dynamics, where the TD O-atom flux increased with surface temperature and the IS O-atom flux remained relatively constant. While the majority of the TD O atoms desorbed promptly after the beam pulse struck the network, signatures of thermal processes occurring over long residence times were also observed. Evidence of O₂ reactions was not observed, and the behavior of the inelastically scattered O₂ was invariant to the temperature of the network and showed both IS and TD dynamics. The dominant reactive product was CO, whereas CO₂ was a minor product. Both these products showed only TD dynamics. The observed flux of CO initially increased with temperature and then reached a plateau above which the flux no longer increased with temperature, over the temperature range studied. Thermally desorbed CO products exited the network promptly or after relatively long residence times, and two populations of CO with long residence times were distinguished. Hysteresis was observed in the temperature-dependent flux of thermally desorbed O and CO, with opposing trends for the two products. This work follows similar studies in our laboratory where the target materials were vitreous carbon and highly oriented pyrolytic graphite. The data suggest that the chemical reactivity of the three forms of <i>sp</i>² carbon surfaces is similar and that the differences arise from the variations of the morphology. <br>

Reactive and Inelastic Scattering Dynamics of Hyperthermal O and O2 from a Carbon Fiber Network

The reactive and inelastic scattering dynamics of ground-state atomic and molecular oxygen from a carbon fiber network at 1023-1823 K was investigated with a molecular beam-surface scattering technique. A molecular beam containing hyperthermal O and O₂ with a mole ratio of 0.92:0.08 and nominal velocity of 8 km s^-1 was directed at the network, and time-of-flight distributions of the scattered products were collected at various angles with the use of a rotatable mass spectrometer detector. O atoms exhibited both impulsive scattering (IS) and thermal desorption (TD) dynamics, where the TD O-atom flux increased with surface temperature and the IS O-atom flux remained relatively constant. While the majority of the TD O atoms desorbed promptly after the beam pulse struck the network, signatures of thermal processes occurring over long residence times were also observed. Evidence of O₂ reactions was not observed, and the behavior of the inelastically scattered O₂ was invariant to the temperature of the network and showed both IS and TD dynamics. The dominant reactive product was CO, whereas CO₂ was a minor product. Both these products showed only TD dynamics. The observed flux of CO initially increased with temperature and then reached a plateau above which the flux no longer increased with temperature, over the temperature range studied. Thermally desorbed CO products exited the network promptly or after relatively long residence times, and two populations of CO with long residence times were distinguished. Hysteresis was observed in the temperature-dependent flux of thermally desorbed O and CO, with opposing trends for the two products. This work follows similar studies in our laboratory where the target materials were vitreous carbon and highly oriented pyrolytic graphite. The data suggest that the chemical reactivity of the three forms of <i>sp</i>² carbon surfaces is similar and that the differences arise from the variations of the morphology. <br>

Reactive and Inelastic Scattering Dynamics of Hyperthermal O and O2 from a Carbon Fiber Network

The reactive and inelastic scattering dynamics of ground-state atomic and molecular oxygen from a carbon fiber network at 1023-1823 K was investigated with a molecular beam-surface scattering technique. A molecular beam containing hyperthermal O and O₂ with a mole ratio of 0.92:0.08 and nominal velocity of 8 km s^-1 was directed at the network, and time-of-flight distributions of the scattered products were collected at various angles with the use of a rotatable mass spectrometer detector. O atoms exhibited both impulsive scattering (IS) and thermal desorption (TD) dynamics, where the TD O-atom flux increased with surface temperature and the IS O-atom flux remained relatively constant. While the majority of the TD O atoms desorbed promptly after the beam pulse struck the network, signatures of thermal processes occurring over long residence times were also observed. Evidence of O₂ reactions was not observed, and the behavior of the inelastically scattered O₂ was invariant to the temperature of the network and showed both IS and TD dynamics. The dominant reactive product was CO, whereas CO₂ was a minor product. Both these products showed only TD dynamics. The observed flux of CO initially increased with temperature and then reached a plateau above which the flux no longer increased with temperature, over the temperature range studied. Thermally desorbed CO products exited the network promptly or after relatively long residence times, and two populations of CO with long residence times were distinguished. Hysteresis was observed in the temperature-dependent flux of thermally desorbed O and CO, with opposing trends for the two products. This work follows similar studies in our laboratory where the target materials were vitreous carbon and highly oriented pyrolytic graphite. The data suggest that the chemical reactivity of the three forms of <i>sp</i>² carbon surfaces is similar and that the differences arise from the variations of the morphology. <br>

Stability analysis of a nanopatterned bimaterial interface

In the article it is shown that the nanopatterned interface of bimaterial is unstable due to the diffusion atom flux along the interface. The main goal of the research is to analyze the conditions of interface stability. The authors developed a model coupling thermodynamics and solid mechanics frameworks. In accordance with the Gurtin—Murdoch theory of surface/interface elasticity, the interphase between two materials is considered as a negligibly thin layer with the elastic properties differing from those of the bulk materials. The growth rate of interface roughness depends on the variation of the chemical potential at the curved interface, which is a function of interface and bulk stresses. The stress distribution along the interface is found from the solution of plane elasticity problem taking into account plane strain conditions. Following this, the linearized evolution equation is derived, which describes the amplitude change of interface perturbation with time.