Rapid Preparation And Electrochemical Energy Storage Applications Of Silicon Carbide And Silicon Oxycarbide Ceramic/Carbon Nanocomposites Derived Via Flash Photothermal Pyrolysis Of Organosilicon Preceramic Polymers

Silicon carbide (SiC) and silicon oxycarbide (SiOC) ceramic/carbon (C) nanocomposites are prepared via photothermal pyrolysis of cross-linked polycarbosilanes and polysiloxanes using a high-intensity pulsed xenon flash lamp in air at room temperature to yield crystalline and amorphous phases of SiC and SiOC ceramics, graphitic, and amorphous carbon phases. The millisecond duration of the radiation pulse is shorter than the thermal equilibrium time of the preceramic polymers (PCPs), enabling pyrolysis of the precursor phase and crystallization of the product before significant energy transfer to the substrate, making this process uniquely amenable to ceramic processing on or adjacent to thermally sensitive materials. Rapid precursor pyrolysis and product crystallization during flash lamp processing, even in air, limit oxidation of the resulting ceramics. To prepare the nanocomposites, PCPs are coated onto woven carbon fiber fabrics, thermally cross-linked, and then flash-lamp-pyrolyzed. The resulting nanocomposites are thermally and oxidatively stable at extremely high temperatures. The nanocomposites exhibit excellent performance as supercapacitor electrodes with capacitance as high as 27.2 mF/cm(2) at a 10 mV/s scan rate at room temperature, excellent stability over 1000 cycles, and Coulombic efficiency of 80%. Patterned nanocomposites are prepared via nanoimprint lithography, followed by photothermal processing of precursor films. These nanocomposites have potential applications in energy storage, catalysis, and separations.