The class of particles stabilized o/w emulsion type has been extended to emulsions made immiscible liquid metals /alloys. Mixing immiscible liquid metals causes metal droplets appear homogeneously in the other liquid metal.
Liquid metallic emulsions not stabilized by solid particles are unstable both due to the gravity and due to the effect of interfacial gradient force. Alternatively, they can be partially stabilized by fast cooling or solidification. Slow cooling of the molten metal mixture results in two separated layers situated one above another driven by the difference between their densities.
In this work, a third inert solid phase was introduced in order to stabilize metal droplets in the matrix and thus to avoid phase separation. Bi of purity 99% and SiC particles reinforced aluminium alloy matrix composites have been used in these experiments. In this system, the contact angle appears to be in the interval of optimum values, and thus the SiC particles accumulated at the phase boundary to prevent the coalescence of Bi droplets in Al matrix. The volume fraction of the stabilizing SiC particles were kept at a nearly constant value, while the volume fraction of the Bi rich phase was shifted from the lower value of 0.31 to the higher value of 0.61.
Finally SEM evaluation demonstrates that Bi-rich droplets are stabilized in Al-rich matrix by the solid SiC particles at low Bi volume fraction of 0.31. On the other hand, Al-rich droplets are stabilized in Bi-rich matrix by solid SiC particles at high Bi volume fraction of 0.61. Thus, we have experimental evidence for the first time that metallic emulsions stabilized by solid particles can be inverted by shifting the phase ratio of the two immiscible liquid alloys.
References:
[1] I.Budai, G.Kaptay: A new class of engineering materials: particles stabilized metallic emulsions and monotectic alloys. Metall Mater Trans A, 2009, vol.40A, pp.1524-8.
[2] I. Budai, G. Kaptay, Wettability of SiC and alumina particles by liquid Bi under liquid Al, J. Mater. Sci.45 (2010) 2090-2098.
[3] I.Budai, O.Z.Nagy, G.Kaptay: Inversion of a liquid Bi/Al metallic emulsion stabilized by solid SiC particles, Coll Surf A, 2011, vol.377, pp.325-329