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Eutectic Structures Competition in the Stripes Strengthening the (Zn) – Single Crystal

Wołczyński W., Kjelstrup S., Bedeaux D., Szajnar J., Billia B.

Archives of Foundry Engineering

2014

Vol. 14, iss. 4

95--102

Some eutectic stripes have been generated in a hexagonal (Zn) - single crystal. The stripes are situated periodically with the constant inter stripes spacing. The eutectic structure in the stripes consists of strengthening inter-metallic compound, Zn16Ti, and (Zn) – solid solution. The rod-like irregular eutectic structure (with branches) appears at low growth rates. The regular lamellar eutectic structure is observed at middle growth rates. The regular rod-like eutectic structure exists exclusively in the stripes at some elevated growth rates. A new thermodynamic criterion is recommended. It suggests that this eutectic regular structure is the winner in a morphological competition for which the minimum entropy production is lower. A competition between the regular rod-like and the regular lamellar eutectic growth is described by means of the proposed criterion. The formation of branches within irregular eutectic structure is referred to the state of marginal stability. A continuous transitions from the marginal stability to the stationary state are confirmed by the continuous transformations of the irregular eutectic structure into the regular one.

Reactor design by the principle of equipartition of forces and its extensions

Kjelstrup S., Sauar E., Bedeaux D., Kooi H.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

1998

Z. 66

133-145

We have previously proven that chemical reactors with a given output of product, have minimum entropy production when the force of the reaction rate is constant over the reactor. This applies to cases where the reaction rate, r, is proportional to the force, A/T, where A is the affinity and T is the temperature. We have called this result the principle of equipartition of forces. This paper presents excerpts from a more extensive paper submitted for publication. We present the proof on a continuous form, and we discuss how the constant force can be determined and maintained, using an isoforce operating path. In general, minimum entropy production is obtained when A/T+rd(A/T)/dr is constant. We show how operating paths with minimum entropy production, can be constructed for reactions far from equilibrium when reaction kinetics are known.