Non-isothermal reaction mechanism and kinetic analysis for the synthesis of monoclinic lithium zirconate (m-Li2ZrO3) during solid-state reaction

Non-isothermal reaction mechanism and kinetic analysis for the synthesis of monoclinic lithium zirconate (m-Li2ZrO3) were investigated by processing of TG-DTA, along with XRD, DLS, and HRTEM. For this purpose, the solid-state reaction of Li2CO3 with ZrO2 was carried out by TG-DTA at different heating rates (10, 20, and 30 °C/min) from room temperature to 1100 °C. The thermal data was used to calculate the kinetic parameters by two types of isoconversional methods: Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The reaction mechanism was determined by the model-fitting method, applying the Coats-Redfern (CR) approximation to the different solid-state reaction models. The results confirmed the formation of pure m-Li2ZrO3, consists of semispherical particles of about 490 nm, using a very short reaction time. The average activation energy obtained by FWO and KAS methods were 274.73 and 272.50 kJ/mol, respectively. It was found that the formation of m-Li2ZrO3 from Li2CO3 with ZrO2 is governed by the three-dimensional diffusion mechanism. Based on these results, a microscopic reaction model of the formation of m-Li2ZrO3 was proposed.

On the p(x) approximation in the non-isothermal reaction kinetics by a generalized exponential integral the concept

A non-Arrhenius model based on the Mittag-Leffler function has been conceived as a basic concept. This approach allows modelling both sub-Arrhenius and super-Arrhenius behaviours and giving rise to modified temperature integrals.

COMPARISON OF MAGNETIC NANOPARTICLES AND MICROPLATES AS CARRIERS IN HETEROGENEOUS CHEMILUMINESCENT ASSAY OF MICRORNA-141 USING CATALYTIC HAIRPIN ASSEMBLY

Comparison of two types of carriers (magnetic nanoparticles and microplate) for the detection of oligonucleotides is carried out. It was shown that the value of analytical parameters in chemiluminescent heterogeneous assay of microRNA-141 using an isothermal reaction of catalytic hairpin assembly did not depend on the choice of the carrier.

Qualitative Study of a Well-Stirred Isothermal Reaction Model

We consider a two-dimensional system which is a mathematical model for a temporal evolution of a well-stirred isothermal reaction system. We give sufficient conditions for the existence of purely imaginary eigenvalues of the Jacobian matrix of the system at its fixed points. Moreover, we show that the system admits a supercritical Hopf bifurcation.

Thermodynamic Analysis of the Reaction of High Modulus Sodium Silicate

The thermodynamic method is based on the study and analysis of the formation of high-modulus sodium silicate. It is determined by the thermodynamic method of the isobaric-isothermal reaction potential using the equation of the second law of thermodynamics, the Kirchhoff law and the Gibbs equation. To conduct a thermodynamic analysis for all in the reaction of the compounds, the necessary tabular data were used, and a thermodynamic analysis was performed for four chemical reactions. Equations of changes in the isobaric-isothermal potential as a function of temperature are compiled for all reactions. Based on the results obtained, it was concluded that the first reaction is practically the most acceptable for the production of silicate energy.

Improvement of Methane Combustion Activity for Pd/ZrO2 Catalyst by Simple Reduction/Reoxidation Treatment

The improvement of methane combustion activity was observed in cyclic temperature-programed and isothermal reactions over Pd/ZrO2 catalysts by simple reduction/reoxidation treatment. The catalytic activity increased during the initial stages of isothermal reaction, and the light-off temperature was lowered as the number of cycles increased in the cyclic temperature-programed reaction. To reveal the origin of activation, variations in the reduction properties after the activation period were carefully investigated through CH4 temperature-programed reduction (TPR) measurements. From the CH4-TPR results, it was confirmed that the reduction temperature decreased significantly after activation. The observation of the CH4-TPR peak at relatively low temperatures is directly proportional to the catalytic activity of CH4 combustion. It was therefore concluded that repeated reduction/reoxidation occurred in the reactant stream, and this phenomenon allowed the combustion reaction to proceed more easily at lower temperatures.