Effect Of Water Molecules On Wear Behavior Of Phosphate Laser Glass At Nanoscale

Phosphate laser glass has been widely applied for hig h-peak-power laser system as an energy gain medium all over the world,because of its excellent optical property.However,the surface quality of the glass is a critical factor affecting laser energy output.In addition,owing to surface processing of phosphate laser glass carried out in the moist atmosphere,the water molecules will inevitably affect the material removal on the glass surface.Therefore,it is necessary to investigate the effect of the water molecules in humid air on the material removal and wear mechanism of phosphate laser glass.In the paper,based on the pair of phosphate laser glass and silicon dioxide,the effect of water molecules on nanowear regularity and mechanisms was studied by an atomic force microscope(AFM)equipped with an environment chamber.Firrstly,the wear of phosphate glass at nanoscale was investigated under vacuum,dry air,and humid air,respectively,to reveal the material removal and wear mechanisms of the glass under different ambient conditions.Secondly,in order to make a contrast for the above research at nanoscale,the wear of glass at macroscale was accomplished with a reciprocating sliding tribometer.Eventually,the influence of absorbed water induced mechanochemical wear mechanism of phosphate laser glass was further analyzed by comparison with the friction coefficient,wear depth,and surface damage of the glass in two environment conditions at nanoscale and macroscale.Based on the above research,the main conclusions in the paper can be summarized as follows:(1)Under the same normal load conditions at nanowear,the adhesion and friction coefficient in humid air were much higher than those in vacuum and dry air.Capillary water bridge caused by absorbed water greatly contribute s to the high adhesion and friction in humid air.In addition,the chemical bond force between glass and particle is one of the reasons for the high friction in humid air.(2)The more serious material removal of PL glass in humid air is related to the combined contribution of static corrosion and stress corrosion induced by water meniscus at the contact interface.In vacuum and dry environment,the wear behaviors at phosphate glass interface were dominated by mechanical wear,but the wear characteristics of the glass surface were m ainly determined by mechanochemical wear.Also,countersurface chemistry also plays an important role in the friction and wear of phosphate laser glass at the nanoscale surface.(3)In the nanowear and macrowear experiments,surface wear of phosphate glass in humid air was more serious than that in dry air.However,owing to the various contact mode as well as stress corrosion rate between the glass and countersurface at nanoscale and macroscale,the material removal and surface damage were different in the two scales.