Development of an oscillating cup viscometer for viscosity measurement of liquid metals at very high temperatures

On Crossover Temperatures of Viscous Flow Related to Structural Rearrangements in Liquids

“…There is, however, an additional crossover temperature at extremely high temperatures when viscosity attains its minimum possible value; here, the flow becomes non-activated and starts to increase with temperature. The equations proposed for assessing the minimum viscosity (7) and the new crossover temperature (8) are shown to provide reasonable data that are close to those observed experimentally in [ 23 , 24 ].…”

“…The viscosity of several molten metals was recently measured over a wide temperature range up to 2100 K using an oscillating cup viscometer [ 24 ]. The viscosities of both Sn and Pb were successfully measured over the temperature range 506–2135 K for liquid tin and 710–1770 K for liquid lead, providing unpublished data and explicitly revealing the presence of the minimal viscosity of Sn at about 1600 °C ( Figure 4 ).…”

“…The available data on the viscosity of liquid Sn at high temper atures, such as [61][62][63], did not reveal the viscosity minimum, only enabling a rough ap preciation of the asymptote of viscosity by typically taking the highest-temperature ex perimental data for metals as an approximate measure of the minimum viscosity [22] Figure 3 shows the predicted minimal viscosity of liquid Sn based on the available data a the publication time of [37]. The viscosity of several molten metals was recently measured over a wide tempera ture range up to 2100 K using an oscillating cup viscometer [24]. The viscosities of both Sn and Pb were successfully measured over the temperature range 506-2135 K for liquid tin and 710-1770 K for liquid lead, providing unpublished data and explicitly revealin the presence of the minimal viscosity of Sn at about 1600 °C (Figure 4).…”

“… 1 Data on activation energies and viscosities at the indicated temperatures were taken from [ 24 , 64 ] for Sn and Pb; from [ 1 , 64 ] for Na, Pb, and Bi; from [ 64 , 65 ] for Hg; from [ 66 ] for Ga; and from [ 22 ] for Zr 57 Nb 5 Cu 15.4 Ni 12.6 Al 10 , with E a assessed from Figure 1 of [ 22 ]. 2 The temperature T is the temperature at which viscosity (in column 3) is used for calculations in Equation (7).…”

“…Moreover, since the liquid’s viscosity decreases with increasing temperatures and the gas’s viscosity increases with increasing temperatures, at sufficiently high temperatures, the viscosity must encounter a minimum value [ 19 , 20 , 21 , 22 ]. It is notable that viscosity minima were experimentally observed in many non-metallic systems [ 19 , 23 ] and in liquid tin (Sn) [ 24 ]. The minimum arises from the crossover between two different viscous flow regimes within condensed and gaseous phases at some crossover temperature, denoted here as T vm .…”