Fabrication of Functional Ceramic Nanostructures and Hybrids from Preceramic Polymer Route

Abstract

Advanced functional applications of materials often require unique microstructures and morphologies embedded in single or multi-phase nanostructures. For examples, lithium ion batteries (LIB) and supercapacitors, by far, the most promising energy storage devices that find application in numerous equipment of varying utility and dimension, require electrode materials with special microstructures for enhanced energy and power density. Hence, attention has shifted to the design of novel materials chemistry, morphology, and nanostructures, from among oxides, alloys, and hybrid materials.

Preceramic polymer derived silicon oxycarbide (SiOC) materials have evolved to be an important candidate for next generation electrodes. Polymer derived ceramics (PDC) are known for their exceptional heat resistance, zero creep strain rate, piezoresistivity, photoluminescence, and Li ion intercalablity. The ability of PDC materials to be processed from a liquid precursor state offers distinct advantages for the fabrication of materials of different form factors. The unique nanostructure of the SiOC materials comprising of SiO2 nanodomains and graphene type carbon layers, and regions of mixed bond tetrahedra, provide excellent opportunities for the processing of functional materials. A few approaches will be discussed in the presentation. First, following a generic and straightforward method a ceramic hybrid has been prepared by using a nanodimensional coating of the SiOC ceramics around a nanostructured ceramic template (eg. C/TiO2). The synthesized hybrid materials exhibit extreme rate capability with symmetric cycling up to current rate of 20,000 mA g-1. Second, in a similar approach with the help of nanocarbon and SiOC, and by subsequent etching of the SiOC matrix, a highly porous carbon hybrid with specific surface area of 1800 m2 g-1 with micropore volume as high as 0.9 cc g-1 has been prepared. These carbon hybrids exhibited classical supercapacitive behavior from cyclic voltammetry and show specific capacitance of 333 F g-1. Further, a metal-doped polymer derived ceramic has been explored to fabricate a hybrid of nanostructured metal oxide/carbide phase dispersed in an amorphous SiCO matrix for potential application in supercapacitor electrodes. These examples will be used to explore the processing of more kinds of nanostructures of various other chemistries, yet with the use of preceramic polymers.