Conductive coatings with low carbon-black content by adding carbon nanofibers

Conductive coatings based on low carbon-black content by adding carbon nanofibers are obtained in a silica matrix obtained by the sol-gel process. The carbon nanofibers incorporation allows reducing the percolation threshold down to 20 wt.% of carbon black into the silica matrix obtaining good electrical properties. Coatings are deposited by air-spray deposition onto tile substrates and sintered in the temperature range of 300-500 degrees C in air atmosphere. The coatings achieve resistivities as low as 2 x 10(-3) Omega m due to the percolation between the carbon black nanoparticles and carbon nanofibers which improves the conductive paths. The samples are microstructural characterized by Scanning Electron Microscopy and Confocal Raman Spectroscopy. The electrical properties are measured by impedance spectroscopy. The thermal properties derived of the Joule effect are measured using DC intensity-voltage curves and thermal infrared camera, and it is observed a nearly linear relationship between electric power and temperature increasing in the measured range. Thereby, a wide range of application is opened by means of tailoring the electrical response of the coatings: higher resistivity coatings produce thermal heating above 90 degrees C, appropriated for electric heaters, and conductive coatings are suitable for electronic devices, electrodes and EMI/RFI shielding. (C) 2014 Elsevier Ltd. All rights reserved.