Study of Laser Ablation and Mechanical Properties of Silicone ...

Proc. ESA Annual Meeting on Electrostatics 2008, Paper B3 635020%m+% nfs20% m+ % nfs+ 14 pph T20% m + % nfs+ 28 pphT300Eroded mass (mg)2502001501.25% 2.5% 3.75% 5%% of nano fumed silicaFigure 3: Average eroded mass of three samples with 20 % microsilica filler (m) for various additions of nanofumed silica (nfs) and Triton (expressed in parts per hundred, pph, of nanofiller by weight).The eroded mass observed in laser ablation tests using calcinated fillers is shown inFigure 4 for several fillers and as a function of Triton content. It appears that calcinationdoes not have as much influence on the eroded mass as the addition of Triton, and all theresults tend to converge when adding 28 pph of Triton.In these tests it was noticed that for the 2.5% nfs content treated at 900°C, a whitelayer developed in the sample during the test. As shown in Figure 5, this is likely to be alayer of silica formation; and such a protective mechanism decreasing sample erosion hasbeen reported previously [11].The decomposition of SiR in air is known to produce white silica particles [12]. Thewhite layer is therefore attributed to filler residues and to the decomposition of the SiRmatrix in air. For this reason, samples with 2.5% nfs thermally treated at 900°C were notevaluated by the laser technique, because the laser beam is likely reflected by the whitelayer, biasing the erosion level determined by laser ablation. It appears likely that thissilica layer also forms a heat-resistant shield hindering further heat ablation of the underlyingSiR matrix.