Surface tension and viscosity of NiAl catalytic precursor alloys from microgravity experiments

Abstract

Abstract The surface tension and the viscosity of the catalytic precursor alloys Ni-68.5 at.% Al, Ni-75 at.% Al and Ni-75 at.% Al-1.5 at.%. Cr were measured over a temperature range of about 400 K using the oscillating drop technique in an electromagnetic levitation device under reduced gravity conditions. The experiments were performed on board parabolic flights and on a TEXUS sounding rocket flight. At the liquidus temperatures of 1 604 K and 1398 K the viscosities of Ni-68.5 at.% Al and Ni-75 at.% Al were obtained as ν(Tliq) = 4.31 mPa · s and ν(Tliq) = 4.53 mPa · s, respectively. In the investigated temperature range the viscosity exhibited a linear temperature dependence. The surface tension as a function of temperature can be represented as ω(T) = 1.01 N m−1 – 2.8 · 10−4 (T – 1 603 K) N m−1 and ω(T) = 0.92 N m−1 – 1.40 · 10−4 (T – 1 398 K) N m−1 for Ni-68.5 at.% Al and Ni-75 at.% Al, respectively. Comparison of the experimental viscosities with predictions from different semi-empirical models showed that the latter underestimate the experimental values by between 25 and 40%.