An investigation into the effect of polyvinylpyrrolidone on the size and distribution of nickel catalyst particles for controlling CNTs’ morphology and growth mechanisms in fabricated hybrid CF-CNT nanocomposite

Despite the considerable research efforts devoted in recent years to the use of carbon nanotube (CNTs) composites, the main challenge still to be addressed is obtaining the appropriate catalyst particle size and distribution to control composite morphology and properties. In order to fabricate carbon felt–carbon nanotube nanocomposites via the chemical vapor infiltration (CVI) method, use was made for the first time in this study of the polyvinylpyrrolidone (PVP) polymer to achieve the reduced size and more uniform distribution of nickel catalyst particles. The results obtained from morphological analyses (SEM, FESEM, TEM, and HRTEM images), phase and chemical structure investigations (FTIR, Raman spectroscopy, XRD, and XPS tests), and specific surface area determinations (BET test) conducted on samples produced with and without the polymer were compared to evaluate the effects of using PVP. It was found that the polymer was able to reduce nickel particle size, improve their distribution on fibers, and provide more nucleation sites for CNTs by preventing their agglomeration. Moreover, this phenomenon leads to dramatic enhancements in the chemical activity of catalytic particles that would ultimately give rise to the following three significant results: (1) surface destruction and carbon infiltration from the felt fibers’ surface to help form CNTs, (2) CNT growth model changing from a “tip-growth” to a “base-growth” one, and (3) a reduction of 57% in CNTs’ diameter and wall thickness. These morphological changes in the nanocomposite samples will, in turn, lead to a fivefold increase in the specific surface area of the nanocomposites produced using PVP to 262.45 m2/g after 10 h of the CVI process. Graphical Abstract