Online monitoring and mass transfer modelling of the growth of Ni‐B nanoparticles in a reverse micelle system

Abstract

AbstractThe growth of Ni‐B nanoparticles by chemical reduction of nickel acetate tetrahydrate (0.3M) using sodium borohydride (B/Ni = 2.5 molar ratio) in CTAB/n‐hexanol/water ternary reverse micelles was investigated. SEM studies showed that the synthesized nanoparticles within the reverse micelle range are more favourable in terms of microstructure and morphology. Nanoparticle growth has been controlled in the range of 0.83–5.59 nm · h−1 by the precise adjustment of mass fraction of surfactant in the oil phase (0.22–0.47 wt%) and the overall mass fraction of the aqueous phase (0.1–0.3 wt%) values. Particle growth was measured in situ using time resolved UV‐vis absorbance spectroscopy. In addition, a new correlation based on characteristic absorbance peaks of Ni‐B nanoparticles at wavelengths of 285 and 230 nm has been derived for this purpose. An accuracy of about 9 % on the nanoparticle average sizes with respect to sizes measured by dynamic light scattering (DLS) was found (R2 = 0.98). A diffusion controlled growth model involving effective diffusivity of reverse micelles (Deff − RM = 9.60 × 10−11 − 1.17 × 10−8 m2 · s−1) andripening parameter (K = 4.57 × 10−21 − 1.54 × 10−20 m2 · s−1) was developed to describe the growth behaviour of the nanoparticles. The experimental results were very close to the experimental results with slight errors (7–10 %). Finally, TEM micrographs of Ni‐B nanoparticles showed that particle growth as well as agglomeration can be effectively controlled by precise adjustment of each component in the reverse micelle technique.