CHEMICAL VAPOR DEPOSITION FABRICATION AND CHARACTERIZATION OF SILICA-COATED CARBON FIBER ULTRAMICROELECTRODES

摘要

Carbon fiber disk ultramicroelectrodes (UMEs) with well-defined geometries were prepared by chemical vapor deposition techniques. Transparent silica films with thicknesses from 1 to 600 mu m were deposited on the cylindrical length of 5 and 10 mu m carbon fibers from a SiCl4, H-2, and O-2 ternary precursor system at 850-1150 degrees C or sequential deposition from Si(OEt)(4) as a single source precursor at 700 degrees C followed by the SiCL(4), H-2, and O-2 precursor system. Film thickness, film adhesion to the fiber substrate, and the overall dimensions of the silica-coated carbon fiber were studied and found to be a function of the precursor system, precursor concentrations, fiber diameter, deposition time, and fiber temperature. The silica films were found to be free of microcracks and characterized by a quality seal between the carbon fiber and the coating. As a result, the silica-coated disk UME exhibits an excellent electrochemical response without the need to use an epoxy sealant at the electrode tip. Furthermore, the deposition of hard and inert ceramic materials imparts durability to fragile carbon fibers and facilitates the handling of UMEs in microenviromnents, Finally, the advantage of concentric deposition about the fibers to produce a disk UME in the center of an insulating plane was used to examine the effect of the thickness of the insulating coating on the limiting current response. [References: 65]