In a novel approach, a nickel‐doped carbon rich preceramic polymer is converted into a carbon nanotubes (CNT) bearing polymer derived ceramic (PDC). Milling and field‐assisted sintering demonstrate that the CNTs remained stable during processing, and the CNTs are found to be embedded in the PDC matrix.
A major challenge in the processing of compact polymer derived ceramics is the removal of pores. Even after field‐assisted sintering (FAST) under pressure, a certain level of porosity remains within samples and parts. In order to reduce the porosity, a novel route is developed making use of the addition of trimethyl borate to a polysilsesquioxane‐type preceramic polymer system; trimethyl borate is a molecular boron oxide precursor. It is found that boron‐oxide free samples show a high compression rate during field‐assisted sintering between 1400 and 1600 °C, boron oxide and boron oxide/alumina containing samples show this effect already between 1350 and 1500 °C. In a tentative reaction mechanism, this effect is assigned to the formation of a borosilicate glass by chemical reactions of boron oxide with the silica component of the polysiloxane‐derived ceramic; this glassy phase assists the densification process by viscous flow. The porosity in boron oxide‐containing samples is found to be between 0.3% and 1.4% while boron oxide‐free samples show a total porosity of ≈38% after processing under identical conditions.
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