Formation of Vertically Aligned Stalagmite-Like Carbon Rod Arrays by the Electrostatic Spray Deposition

We present a new method to form vertically aligned stalagmite-like carbon rod arrays by using electrostatic spray deposition (ESD). The precursor solution, composed of thermosetting phenol-formaldehyde resol resin and ethanol, was sprayed on heated substrates under different conditions. The carbonization of the specimens occurred at 900 degrees C in vacuum. As a result, vertically aligned carbon rods were formed by the interplay of the preferential landing phenomenon in the ESD process and viscosity changes during the curing of the thermosetting resin. The morphological features of the carbon rod array, such as height and diameter of the rods and mean distance between the rods, were controlled by adjusting the processing parameters, including flow rate of the feed solutions, substrate temperature, and duration of the continuous spraying. Furthermore, the uniform rod array could be formed not only on the top surface of the substrate, but also at the edges. Therefore, the ESD method provides a valuable approach to deposit one-dimensional layers on complex-shaped surfaces in a relatively short processing time.