Authors:Linping Zhang, Xianlei Song, Yanyan Song, Zhanbo Sun, Qian Li, Xiaoping Song, and Liqun Wang
According to thermodynamic theories, the state of alloys can be divided into equilibrium and non-equilibrium. Non-equilibrium alloys generally exhibit some special mechanical and physical properties which are not
An adiabatic calorimetry was used for some investigations of equilibrium and non-equilibrium phase transitions. For one of
the substances studied (4,4′-di-n-heptyloxyazoxybenzene) it was possible to determine temperature dependence of an order parameter and number of clusters of
high temperature phase in a region of a phase transition. For another substance (liquid 3,4 dimethylpiridine) an anomaly on
the specific heat curves was interpreted as being responsible for a decay of molecules’ clusters.
Non-equilibrium phase transitions were investigated for some liquid crystal substances. The process of transformation between
metastable and stable phases was described quantitatively. The conclusions obtained concern the stability of metastable phases.
It is well-known that eutectics do not necessarily grow at the eutectic temperature, or with the eutectic composition. Thus,
the eutectic point can be shifted due to nonequilibrium conditions in the system. This fact was observed in many experiments.
We try to explain this behaviour on base of the study of phase transformation kinetics. We construct the kinetic phase diagrams
of PbCl2−AgCl within the framework as of the nucleation theory as of the theory of growth on the phase interface. Our models are based
on the molecular model of the difference of chemical potential of components for the liquid and solid phases. The proposed
model describes the position of the eutectic point very well and is practically applied for the study of nonequilibrium directional
growth in the PbCl2−AgCl system.
A new type of the isotope exchange method of analysis is proposed. The method can be applied to the exchange system in which
the rate of the exchange reaction is rather slow but measurable, before the exchange equilibrium is attained. The validity
of the principle of the method is verified experimentally with several exchange systems of RyI+KI*⇌RyI*+KI (RyI stands for alkyl, alkylene or benzyl iodide) type. The iodine content of the organic iodine compounds can be determined
with an error of ±4%.
Authors:N. Smirnov, Yu. Shirokov, A. Artamonov, and M. Nikeshina
The analysis of structural state and energetic properties of active catalyst component in oxide copper-containing catalytic system has been performed on the basis of comparing the data of thermochemical, X-ray diffraction and catalytic activity determinations. The analysis of thermochemical data obtained makes it possible to evaluate changes in lattice energy and the nearest coordination sphere energetic parameters of copper cations during the formation of solid solutions. The high degree of correlation of catalytic properties and the formation enthalpy of solid solutions can be explained by the fact that alongside with the factors influencing the catalytic activity it is the strength of cation—cation interaction that is the most important.
Six discrete formulas are used to estimate the equilibrium constant of the first hydrolysis reaction of tetravalent plutonium.
They apply the pH, the oxidation number, one equilibrium constant, and fractions of two of the plutonium oxidation states.
The new formulas are not restricted to the equilibrium condition.
Some water-soluble organic iodine compounds (aqueous solution) can be analyzed for iodine by isotopically exchanging with labelled elementary iodine (organic solution). The method is applicable to exchange systems in which the rate of the exchange is rather small but measurable, before the exchange equilibrium is attained. The iodine content of iodoaromatic amino acids such as 5-iodouracil and 3,5-diiodotyrosine can be determined within an error of ±4%.
Calorimetry deals with the energetics of atoms, molecules, and phases and can be used to gather experimental details about
one of the two roots of our knowledge about matter. The other root is structural science. Both are understood from the microscopic
to the macroscopic scale, but the effort to learn about calorimetry has lagged behind structural science. Although equilibrium
thermodynamics is well known, one has learned in the past little about metastable and unstable states. Similarly, Dalton made
early progress to describe phases as aggregates of molecules. The existence of macromolecules that consist of as many atoms
as are needed to establish a phase have led, however, to confusion between colloids (collections of microphases) and macromolecules
which may participate in several micro- or nanophases. This fact that macromolecules can be as large or larger than phases
was first established by Staudinger as late as 1920. Both fields, calorimetry and macromolecular science, found many solutions
for the understanding of metastable and unstable states. The learning of modern solutions to the problems of materials characterization
by calorimetry is the topic of this paper.