Kinetics of the crystallization of icosahedral phase in ultra thin deposits of Al₆₂Cu_25.5Fe_12.5alloy

Abstract

Made at room temperature, the deposition of the three elements Al, Cu, Fe in the atomic proportion 62/25.5/12.5 allows amorphous deposits to be obtained. The mixture becomes crystalline when subjected to heat treatment. Several deposits made on transmission electron microscopy (TEM) grids were heated up to different temperature thresholds. Only during annealing above 723 K were nucleation and growth of i-AlCuFe observed. A Mehl-Johnson-Avrami model is proposed to describe this crystallization. This model fits the experimental data very well and allows mean activation energies for volume diffusion to be calculated. Assuming the time of the total transformation, a TTT curve is plotted. Nucleation density values and activation energy of the i-Al 62 Cu 25.5 Fe 12.5 phase nucleation are estimated.

Chirality-selective synthesis of carbon nanotubes by catalytic-chemical vapor deposition using quasicrystal alloys as catalysts

“…Al (2.1 nm)/Cu (0.6 nm)/Fe (0.3 nm) three-layered films were deposited on Si/SiO 2 substrates by sequential electron beam evaporation with an accuracy of $10 pm. Then, the samples were annealed at 723 K for 30 min in a CVD reactor to form nanoclusters in a perfect icosahedral composition, i.e., Al 62 Cu 25.5 Fe 12.5 [9,10], followed by synthesizing CNTs at 973 K for 5 min by alcohol CCVD (hereafter, this sample is referred as sample #1). For comparison, conventional Al (2 nm)/Co (1 nm) two-layered films were deposited on Si/SiO 2 substrates by sequential magnetron sputtering.…”

“…Al/Cu/Fe three-layered ultrathin films were deposited on Si/SiO 2 substrates by sequential electron beam evaporation with a thickness of subnanometric accuracy, followed by annealing in a CVD reactor to form nanoclusters in an icosahedral phase [9,10]. Then, CNTs were synthesized by alcohol CCVD [8].…”