Nanoscale mechanical properties of polymer composites: Changes in elastic modulus and measurement of ion penetration depth due to alpha-radiation

The local mechanical properties of silica-reinforced silicone composites we re investigated using a modified atomic force microscopy technique. Elastic modulus measurements (1.5 +/- 0.1 MPa) are consistent with bulk measuremen ts (1.9 MPa), and changes in the modulus at the surface of the composite sa mples (E = 1.5 to 3.5 MPa) were observed as a result of alpha-irradiation ( dose = 1.7 x 10(10) to 2.0 x 10(12) alpha/cm(2)). The sensitivity of the te chnique was demonstrated by a detectable change in modulus at even the smal l dose of 1.7 x 10(10) alpha/cm(2). The penetration depth of the alpha-part icles into the material, estimated to be 22 +/- 2 mu m from the sample edge , was determined by cross-section depth profiling; and modeling of the ion penetration depth using transport of ions in matter codes (24.4 +/- 0.4 mu m) closely matched experimental observations.