Polarity of the transformation processes in thermal measuring systems

Abstract

The temporal relativistic principle, recently established for calorimetric systems in the framework of the theory of the topoenergetic behaviour of composite systems, is extended to general thermal measuring systems. A thermal measuring system is defined as a measuring system in which the conversion of a response function is measured as a result of a stepwise perturbation in temperature. The process of crystallization revealed by different thermal measuring systems is considered for a series of compounds for which the processes are identical in nature, but differ in amplitude, so that an external affine relation E = n K q-m is verified between the activation energy E and the amplitude term K. It results that the polarity of a transformation process is a characteristic proper to the temporal reference system of the considered measuring system and can be expressed by the signs of the parameters E and/or n. Review of topoenergetic conceptsOn the basis of the recently established topoenergetic principles [1,2], it has been concluded that the behaviour of a composite system in a thermal measuring system is univocally defined by the nature and the amplitude of the revealed transformation process [3]. The two characteristics can be quantitatively determined from the parameters (E, K) which generally define the kinetic equations proper to the direct or single measuring system (SMS) and the differential measuring system (DMS), respectively [4], namely:These equations were established by modelling the eqivalent energetic principles, and both impose as the transformation temperature T, to be applied by the stepwise boundary condition [2], starting from an initial value at which the process occurs slowly or is completely inhibited. Thus a thermal measuring system can be defined as any kind of energetic circuit in which the time conversion for a physical value can be measured as a result of the stepwise variation of the external temperature. DTA systems represent a particular case recently considered in topoenergetic terms [1 -6], with a view to determining the behaviour of the processes of crystallization [5], thermooxidation [4,6], curing-polymerization [7] and degradation by molec-

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“…is included as an apparatus constant, and both K terms 8 N Ci, same sign express the process amplitude by Ci,. The sign of E is a function of process polarity [ 1) For these cases, the (E, n) values have inversed algebraic signs in reference [6], taking into account that the transformation (E, n, ru) +. ( -E , -n , -m) keeps unchanged the process polarity.…”

“…(d) By considering a series of standard composite systems having tho same nature but different amplitude of the transformation process, the parameters E and K furthermore linearly correlate, E = nK + m, where parameters n and n define the group behaviourthe phylogenyof the considered series of composite systems [l, 6, 7-11]. (e) The relative algebraic signs of the first ontogenic and phylogenic parameters define the so-called polarity of the energy flow associated to the transforming component in respect to the laboratory reference frame of the measuring system [6].…”

“…The most suggestive measuring systems for which the newly introduced notions can be defined are the calorimetric systems [2-71. On the other hand these systems represent "a variation on a string" among the analytical and testing techniques, because any kind of transformation process is associated with a heat release and can be revealed by a calorimetric system [12]. The notion of polarity, basically introduced for calorimetric systems [6], has a t the moment the greatest importance for the transformation processes revealed by any other measuring system. I n calorimetric systems the two constitutive components directly reveal the energy (heat) flows which can be of the same or opposite directions corresponding to positive or negative polarity of the transformation process, respectively.…”

“…The data on crystallization by annealing of CrzWl-z quenched alloys [30] were previously represented according to the Arrhenius law and by considering three measuring systems and their associated eigenvalues[6]. We may consider now the initial growth rate of the grain diameter, z (SMS) = (dD/dt)c\ -Ci,, as eigenvalue for different annealing temperatures and different alloy compositions…”