Kinetic of decomposition of some complexes under non-isothermal conditions

Kinetics and Thermodynamics of the Formation of MnFeP4O12

“…The latter usually represents the limiting stage of the reactionthe chemical reactions; random nucleation and nuclei growth; phase boundary reaction or diffusion. Algebraic expressions of functions of the most common reaction mechanisms operating in solid-state reactions are presented in the literature. − …”

“…Several authors − have suggested different ways to solve the right-hand side integral. The integral methods of the Coats−Redfern (CR), the Madhysudanan−Krishnan−Ninan (MKN), and the Tang et al (TL) have been predominantly and successfully used for studying the kinetics of dehydration and decomposition of different solid substances. − For the present study, calculation procedures were based on the CR, MKN, and TL equations. Data from the TG curves in the decomposition range 0.1 < α < 0.9 were used to determine the kinetic parameters of the process in all used calculation procedures.…”

“…These equations were used to estimate the most correct mechanism, i.e., g (α) and f (α) functions. The activation energy, pre-exponential factor, and the correlation coefficient can be calculated from the CR (eq ), MKN (eq ), and TL (eq ) equations combined with 24 conversion functions (Table ). − Equations to imply that there are differences in the calculated values of the activation energy and pre-exponential factor A in the Arrhenius equation, even with the same g (α) function. The value of the coefficient of determination in the linear regression R 2 for eqs to was used as a criterion for the estimation of the three calculating procedures aiming to find the most suitable one.…”

“…They are formed by the calcination of dihydrogenphosphates of bivalent metals or by the calcination of a mixture containing phosphorus and bivalent metal components in the corresponding ratio. − A number of papers have dealt with the use of thermal analysis (TA) under quasi-isothermal, quasi-isobaric conditions to follow the dehydration reactions of some binary metal dihydrogenphosphate hydrates. − So far, however, no report has appeared on the application of kinetic and thermodynamic methods to the investigation of the important condensation products, cyclotetraphosphates. The presence of water molecules of binary dihydrogenphosphate hydrates influences the intermolecular interactions (affecting the internal energy and enthalpy) as well as the crystalline disorder (entropy) and, hence, influences the free energy, thermodynamic activity, solubility, stability, and electrochemical and catalytic activity. − Studies on the thermodynamics, mechanisms, and kinetics of solid-state reactions are a challenging and difficult task with complexity resulting from a great variety of factors with diverse effects such as reconstruction of solid state crystal lattices, formation and growth of new crystallization nuclei, diffusion of gaseous reagents or reaction products, materials heat conductance, and static or dynamic character of the environment, physical state of the reagentsdispersity, layer thickness, specific area and porosity, type, amount, and distribution of the active centers on solid state surface, etc. − The results obtained from such studies can be directly applied in materials science for the preparation of various metals and alloys, cements, ceramics, glasses, enamels, glazes, polymers, and composite materials. − …”

“…The presence of water molecules of binary dihydrogenphosphate hydrates influences the intermolecular interactions (affecting the internal energy and enthalpy) as well as the crystalline disorder (entropy) and, hence, influences the free energy, thermodynamic activity, solubility, stability, and electrochemical and catalytic activity. [16][17][18][19][20] Studies on the thermodynamics, mechanisms, and kinetics of solid-state reactions are a challenging and difficult task with complexity resulting from a great variety of factors with diverse effects such as reconstruction of solid state crystal lattices, formation and growth of new crystallization nuclei, diffusion of gaseous reagents or reaction products, materials heat conductance, and static or dynamic character of the environment, physical state of the reagentssdispersity, layer thickness, specific area and porosity, type, amount, and distribution of the active centers on solid state surface, etc. [19][20][21][22] The results obtained from such studies can be directly applied in materials science for the preparation of various metals and alloys, cements, ceramics, glasses, enamels, glazes, polymers, and composite materials.…”