Correlation between the electrical conductivity of oxides and their adhesion to an OZZhR ferrous melt

Abstract

A comparison between the adhesion and electrophysical characteristics of oxides may be useful in predicting the interaction between the latter and a metal.The experimental and calculated data for these characteristices taken both from our own studies and from the published literature [i] are given in Table i. The values of the limiting wetting angle and the electrical conductivity of oxides are given for temperatures of 1700-1800~ at which the region of intrinsic conductivity is reached.The published data which is lacking for the electrical conductivity of oxides at this temperature were obtained by extrapolation using the activation energy [I]. Table 1 also gives the calculated values of log electrical conductivity; the experimental values [I] and the values we calculated using the method in [2] involving the band gap and assuming that the oxides have a semiconducting conduction mechanism.The limiting wetting angle between specimens of several oxides and a liquid metal was measured at 1823~ by the resting drop method developed at the M. I. Kalinin Polytechnic Institute.From the results of the measurements we calculated the adhesion energy.As the liquid metal we used OZZhR-grade iron whose chemical compositions in the initial state and after fining in an ISB-001-PI vacuum furnace are given in Table 2. A comparison of the parameters indicates the absence of any correlation between the adhesion energy and the band gap but the existence of a correlation between the former and the log electrical conductivity. Figure 1 shows the dependence of the adhesion energy on the log conductivity of the oxide.Disregarding the data for oxides of rare-earth elements, we can see that there is a linear relationship with an acceptable spread.The dependence of the electrical conductivity on the reciprocal temperature has the same form; there is an exponential dependence in the activation model for the formation of current carriers, i.e., a ~ aoe~Ea/kT or c = enH, where o 0 is the electrical conductivity extrapolated to I/T = 0; e, charge on an electron; k, Boltzmann's constant; T, absolute temperature; n, concentration of current carriers; n--Noe-Ea/kT; No, concentration of electrically active centers; and H, their mobility. T(O~ / ZOO0