This work investigates the tribological behavior of bilayer surfaces formed by vertically aligned carbon nanotube(VACNT)films grown on top of cementite(Fe_(3)C)layers.Four Fe_(3)C–VACNT surfaces with different morpho...This work investigates the tribological behavior of bilayer surfaces formed by vertically aligned carbon nanotube(VACNT)films grown on top of cementite(Fe_(3)C)layers.Four Fe_(3)C–VACNT surfaces with different morphological and structural aspects were developed using plasma carburizing associated with the metal dusting phenomenon.Their tribological performance was assessed by reciprocating dry sliding tests using a ball-on-flat configuration.The combined analysis of the wear tracks through optical and scanning electron microscopy,energy-dispersive Xray spectroscopy,and Raman spectroscopy indicates that the catalyst particles of the carbon nanotubes are an essential factor controlling the tribosystem.Lubrication and wear depend on the ratio between the nanotubes and their catalyst particle lengths(LN/LP).VACNT films with LN/LP>20 promoted friction coefficient(COF)of~0.08 and reduced the wear rate of the ferrous substrate up to 70%.Wear rates showed an exponential reduction by increasing LN/LP.However,the VACNT film with LN/LP<10 induced severe abrasive wear since the beginning of the tribotests,leading to worse tribological performance than a reference surface composed of a single Fe_(3)C layer.Furthermore,the initial crystallinity of the VACNT films did not affect the solid lubrication or wear resistance of the surfaces.展开更多
We report on the temporal contrast performance of the PHELIX facility in view of the requirements imposed by solidtarget interaction experiments. The requirement analysis for the nanosecond and picosecond temporal con...We report on the temporal contrast performance of the PHELIX facility in view of the requirements imposed by solidtarget interaction experiments. The requirement analysis for the nanosecond and picosecond temporal contrast is derived from empirical data and simple theoretical modeling, while the realization shows that using an ultrafast optical parametric amplifier and plasma mirrors enables meeting this specification.展开更多
We describe predictions for top quark pair differential distributions at hadron colliders,by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak correc...We describe predictions for top quark pair differential distributions at hadron colliders,by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak corrections with double resummation at the next-to-next-to-leading logarithmic accuracy of threshold logarithms and small-mass logarithms.To the best of our knowledge,this is the first study to present such a combination,which incorporates all known perturbative information.Numerical results are presented for the invariant-mass distribution,transverse-momentum distribution,and rapidity distributions.展开更多
基金from the Luxembourg National Research Fund(FNR)under the HI3M project(BRIDGES2020/MS/15381200).
文摘This work investigates the tribological behavior of bilayer surfaces formed by vertically aligned carbon nanotube(VACNT)films grown on top of cementite(Fe_(3)C)layers.Four Fe_(3)C–VACNT surfaces with different morphological and structural aspects were developed using plasma carburizing associated with the metal dusting phenomenon.Their tribological performance was assessed by reciprocating dry sliding tests using a ball-on-flat configuration.The combined analysis of the wear tracks through optical and scanning electron microscopy,energy-dispersive Xray spectroscopy,and Raman spectroscopy indicates that the catalyst particles of the carbon nanotubes are an essential factor controlling the tribosystem.Lubrication and wear depend on the ratio between the nanotubes and their catalyst particle lengths(LN/LP).VACNT films with LN/LP>20 promoted friction coefficient(COF)of~0.08 and reduced the wear rate of the ferrous substrate up to 70%.Wear rates showed an exponential reduction by increasing LN/LP.However,the VACNT film with LN/LP<10 induced severe abrasive wear since the beginning of the tribotests,leading to worse tribological performance than a reference surface composed of a single Fe_(3)C layer.Furthermore,the initial crystallinity of the VACNT films did not affect the solid lubrication or wear resistance of the surfaces.
文摘We report on the temporal contrast performance of the PHELIX facility in view of the requirements imposed by solidtarget interaction experiments. The requirement analysis for the nanosecond and picosecond temporal contrast is derived from empirical data and simple theoretical modeling, while the realization shows that using an ultrafast optical parametric amplifier and plasma mirrors enables meeting this specification.
文摘We describe predictions for top quark pair differential distributions at hadron colliders,by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak corrections with double resummation at the next-to-next-to-leading logarithmic accuracy of threshold logarithms and small-mass logarithms.To the best of our knowledge,this is the first study to present such a combination,which incorporates all known perturbative information.Numerical results are presented for the invariant-mass distribution,transverse-momentum distribution,and rapidity distributions.
