Phase and microstructural evolution in polymer-derived composite systems and coatings

Abstract

Polymer-derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as environmental barrier coatings. Composite coatings have been developed as oxidation and carburization barriers on steel using poly(hydridomethylsiloxane) matrix and titanium disilicide as reactive fillers. A systematic study of the phase transformations and microstructural changes in the coatings and their components during pyrolysis in air is presented here. The system evolves from an amorphous polymer filled with a binary metal at room temperature to an inorganic amorphous network of oxidized silicon and titanium at the target temperature of 800 °C. Crystallization of the composite occurs at higher temperatures to reach cristobalite and rutile by 1600 °C. The polymer-to-ceramic conversion occurs between 200 and 600 °C. The oxidation of the expansion agent and the densification of the composite take place between 300 and 800 °C.

Mechanical properties of polymer-derived ceramic composite coatings on steel

“…9 The volume fraction of porosity after pyrolysis to 800 • C was estimated to be 0.10. The coating consists of TiSi 2 , anatase, and amorphous Si-O-C, with <3% residual carbon.…”

“…Previous work has identified a suitable polymer-expansion agent system, optimized processing parameters, and characterized the compositional and microstructural evolution of the coatings as a function of pyrolysis temperature. [7][8][9] This paper will focus on the mechanical characterization of these coatings including hardness, elastic modulus, ultimate tensile strength, and interfacial shear strength.…”

Ceramics for Sustainable Energy Technologies with a Focus on Polymer-Derived Ceramics

“…Another significant advantage of preceramic polymers is that they have relatively low pyrolysis temperatures compared with traditional ceramic processing methods, often forming dense, amorphous ceramics at temperatures as low as 600-800°C (Torrey and Bordia 2007). While traditional ceramic processing methods such as powder compaction can be used, there are also many polymer processing techniques that can be employed when forming polymer-derived ceramics.…”

“…In order to make thick coatings, the polymeric systems have been filled with reactive fillers that expand during the polymer-to-ceramic conversion (Torrey et al 2006;Torrey and Bordia 2007;Wang et al 2011Wang et al , 2014. These coatings have been shown to demonstrably improve the oxidation resistance of both Fe-based and Ni-based superalloys.…”

Computer Aided Multi-scale Design of SiC-Si3N4 Nanoceramic Composites for High-Temperature Structural Applications

“…The Si-C-O ceramic coatings were made using polymer-precursor processing. This method is a novel way to process low dimensional ceramics such as fibers and coatings, sometimes collectively referred to as the polymer-derived ceramics (PDCs The Si-C-O ceramic coatings investigated in this research were made using processing methods based on polymer-precursors by Prof. Raj Bordia's group at the University of Washington, Seattle-WA, [152][153][154][155]. The coating thickness is approximately 15 µm.…”