Preparation of stainless steel microreactors coated with carbon nanofiber layer: Impact of hydrocarbon and temperature

We have coated stainless steel microreactors with a well-adhered layer of carbon nanofibers (CNFs). The CNFs have been grown by decomposition of a hydrocarbon over microreactors previously coated with Ni dispersed on alumina. As hydrocarbon we used both methane and ethane. Other parameters varied herein are the hydrocarbon:H2 gas composition and the CNF growth temperature. For the same growth temperature, the carbon productivity is higher for ethane than for methane. Remarkably, using ethane as carbon source, the carbon yield increased abruptly for temperatures exceeding 898 K. This is coupled with a less defined morphology and size of nanocarbon materials when temperature increases. Some thicker CNFs with diameters up to 200 nm and some non-fibrous carbonaceous protrusions are present at the highest temperatures. Thus, the microreactor channels resulted plugged and with an uneven surface at growth temperatures higher than 898 K. With ethane at the lowest temperatures (853 and 873 K), the only carbon product present was CNF of diameter smaller than 50 nm. The characterisation of the carbon nanomaterials and growth catalyst shed some light about the relationship between the morphology of carbon species and growth temperature.