Synthesis of carbon nanofibers over lanthanum supported on radially aligned nanorutile: A parametric study

• Published in: Diamond and related materials 2019-11, Vol.99, p.107519, Article 107519
• Main Authors: Dziike, Farai, Franklyn, Paul J., Hlekelele, Lerato, Durbach, Shane H.
• Format: Article
• Language: English
• Subjects: Acetylene; Carbon fibers; Catalysts; Chemical synthesis; Chemical vapor deposition; Flow velocity; Gas flow; Lanthanum; Morphology; Nanofibers; Nanoparticles; Nanorods; Organic chemistry; Parametric statistics; Reaction time; Thermal stability; Thermodynamic properties
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2019.107519

Radially aligned nano-rutile (RANR) was synthesized using the hydrothermal technique. This material was used as catalyst support for Lanthanum (La) nanoparticles which were loaded onto the RANR support by a deposition-precipitation method using urea (DPU) to form La/RANR catalysts. It was observed from TEM images that the width of the nanorods making up the RANR support is ca. 9 nm and the actual RANR is heterogeneously sized, with spherical microstructures that have radii ranging between 1.2 and 1.6 μm. The La nanoparticles were loaded onto RANR at weight percentages ranging from 0.5 to 10 wt%. The as-synthesized La/RANR catalyst was used to catalyze the synthesis of carbon nanofibers (CNFs) by chemical vapor deposition (CVD), using acetylene as a carbon source and hydrogen as a reducing gas. A parametric study was conducted to investigate how gas flow rate, synthesis temperature, reaction time, and La loading on La/RANR affected the growth of CNFs by monitoring the morphology, graphicity and thermal properties of the products. It was observed that 5 wt% La/RANR yielded CNFs with the lowest width and highest graphicity and thermal stability, particularly for the ones synthesized at 700 °C. These CNFs were used as an adsorbent and were observed to have adsorbed over 90% of methyl red within 5 min. [Display omitted] •Radially aligned nano-rutile (RANR) afforded homogeneous deposition of La catalyst using DPU method that enabled loading of nanoparticles of smallest La particle sizes ranging from 3–6 nm around the tips of the nanorods support network.•The La/RANR catalyst supported tip growth of CNFs with La particles being dislodged from the support material and consequently plugging the internal tips of the CNFs at one end or in the middle of the fibre.•Percentage metal loading determined the quality and quantity of CNFs synthesis among other parameters that affect the synthesis of CNFs.•Different conditions of synthesis affected the inherent properties and characteristics of the synthesised CNFs, including degree of crystallinity as measured by Raman.•The CNFs rapidly adsorbed organic contaminants up to their saturation limit above which no more dye was adsorbed from the solution.