AFM Nanoscratch Behaviors of Three Optical Glasses Used in ICF

The nanoscratch behaviors of the phosphate laser glass, K9 optical glass and fused silica glass, used in the inertial confinement fusion system, against a spherical diamond tip were quantitatively studied by an atomic force microscopy in atmospheric environment. Results show that the friction coefficient of the three glasses kept constant first and then increased sharply with increase in normal load. It was because of the transition of friction mechanism from interfacial friction to the combined contribution of interfacial and ploughing friction. Under a same normal load, the friction coefficient of phosphate glass was largest, followed by K9 and fused silica glass. It was verified that the friction coefficient mainly depended on the mechanical properties and surface hydrophilcity of these glasses. Moreover, obvious grooves accompanied by material pile-up were observed on phosphate glass and K9 glass. However, only groove was observed on fused silica glass. Furthermore, the nanoscratch residual depth of the fused silica glass was a little larger than that of phosphate glass for all the load conditions. For the K9 glass, the residual depth of nanoscratch was deepest in the three glasses under low load but lowest under high load conditions. It can be deduced that the scratch residual depth of optical glasses was closely associated with surface mechanical properties, plastic flow and densification.