Optimisation of physical properties of γ-alumina coating microreactors used for the growth of a carbon nanofiber layer

This work addresses the challenging task of preparing a well-adhered and uniform coating of γ-alumina over microreactors made out of stainless steel whose composition is devoid of aluminium. The microreactors have been coated by a sol–gel method. The variation of the preparation conditions, i.e. aging time of the gel and optional step of flushing with pressurized air, rendered microreactors coated with several alumina loadings. A severe test, i.e. ultrasonic maltreatment, has been used to check the adherence of alumina layer. The optimised coating exhibited a 5–6 μm thickness, good adherence and complete coverage after ultrasound treatment. The dispersion of nickel over alumina-coated microreactor enabled to grow a layer of entangled carbon nanofibers with a thickness of 1.5–2.5 μm.