کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1474101 | 991076 | 2015 | 7 صفحه PDF | دانلود رایگان |

The evolution of the environment of Hf sites in a hafnium-alkoxide-modified polysilsesquioxane upon polymer-to-ceramic transformation was investigated via the perturbed angular correlation (PAC) method. The results of the PAC measurements on samples thermally treated at temperatures from 400 to 1300 °C indicate that Hf is surrounded only by oxygen at all studied temperatures. This finding is in agreement with the evolution pathway of polymer-derived SiHfOC ceramics, which were reported to be generated as single-phase amorphous materials upon pyrolysis of alkoxide-modified polysiloxanes and subsequently to phase separate and crystallize towards HfO2/SiOC nanocomposites. Thus, the results presented here support our previous statement that there is a thermodynamic control on the phase separation and crystallization behavior of SiMOC (M = metal) ceramics (Ionescu et al. 96;2013:1899–1903), which in the case of Hf leads to the precipitation and crystallization of hafnia nanoparticles within a SiOC matrix.
Journal: Journal of the European Ceramic Society - Volume 35, Issue 1, January 2015, Pages 29–35