Synthesis of high-specific volume carbon nanotube structures for gas-phase applications

Abstract

A novel and efficient gas-phase method has been developed for synthesizing carbon nanotube (CNT) structures with very high specific volume, high surface area and high porosity. The resulting material has potential application as a catalyst and adsorbent support for gas-phase chemical processes and has several advantages over the conventional liquid-phase approach that involves multiple steps and takes many hours to days resulting in a dense mat of CNTs. Multi-walled CNTs were initially nucleated and grown on alumina nanoparticles using a liquid precursor of ferrocene dissolved in xylene. The CNT seeds were extended using ethylene as the gas precursor. Forces generated by CNT growth separated the alumina support clusters to result in a porous entangled structure with a 60 times gain in weight and a 1300 times gain in volume, compared to the original alumina particles. Effects of ferrocene injection rate, alumina particle sizes, and CNT growth parameters on the volume of the structure were analyzed and it was determined that high ferrocene input, moderate temperatures, and small alumina particles all favor the synthesis of high-volume CNT structures.