Arrays of well-aligned, ca 4.7 mm long carbon nanotubes (CNTs) are grown in a simple, safe, and cost-effective manner using an efficient Al2O3/Fe catalyst prepared by an ion-beam assisted deposition technique (see figure). Importantly, the as-synthesized CNT arrays with lengths ranging from 500 mu m to 1.5 mm are conducive to spinning, and CNT fibers spun from such long CNT arrays show remarkably improved tensile strength.