Laser-assisted growth of molybdenum rods

In this paper, we report for the first time the laser-assisted growth of molybdenum rods via the H-2 reduction of MoF6 with a focused Ar+ laser beam as the heat source. By varying the gas composition, total pressure, and laser power rods with different morphologies were deposited on a tungsten wire. At low H-2/MoF6 molar ratios crystal-like rods were obtained and at higher molar ratios the rods became dendrite-like. The activation energy for the process was determined to be 77 +/- 7 kJ mol(-1) in the temperature range 705-840 K. The reaction order showed to be nearly 3 with respect to the hydrogen partial pressure and zero order with respect to the molybdenum hexafluoride partial pressure. Compositional and morphological characterisation were performed with scanning electron microscopy, energy dispersed X-ray spectroscopy and Auger electron spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.