Thermal Decomposition of Silver Carbonate: Phenomenology and Physicogeometrical Kinetics

Abstract

Thermal decomposition of Ag2CO3 to Ag2O was investigated to identify the physicochemical events that occur during the reaction and to reveal the interactions that cause the complex kinetic behavior of the reaction. Based on comparative investigation of thermal decomposition behavior of six different commercially available Ag2CO3, a physicogeometrical reaction model of two partially overlapping reaction stages is proposed. The reaction stages involve the formation of a surface product layer and an internal reaction in the as-produced core–shell structure of the reacting particles. Immediately after the formation of the surface product layer, the structural phase transitions of Ag2CO3 to two different high-temperature phases occur. Under these conditions, the thermal decomposition behavior is controlled by the diffusional removal of CO2 through the surface product layer and/or the increase in internal partial pressure of CO2. The growth of Ag2O particles in the surface product layer produces possible channels for the diffusion of CO2. The relative rates of the formation of the diffusion channels in the surface product layer and the increase in the internal partial pressure determine whether the internal reaction advances at a steady rate or arrests until thermal decomposition of Ag2O of the surface product layer occurs at higher temperatures. The sample and reaction conditions influence the kinetic behavior of different component processes, resulting in the complex thermal decomposition behavior.

Phase Transformation Synthesis of Novel Ag2O/Ag2CO3 Heterostructures with High Visible Light Efficiency in Photocatalytic Degradation of Pollutants

“…Ag 2 CO 3 , which is a thermally unstable semiconductor, has been intensively investigated in thermal decomposition kinetics . More recently, it was reported that Ag 2 CO 3 showed the obvious visible light activity but very poor stability owing to the photocorrosion which caused the serious deactivation .…”

“…The grain size of the reactant substrate decreases gradually due to the transition of Ag 2 CO 3 , as revealed by TEM. The as‐produced grain boundary is a reactive site for thermal decomposition, in addition to the reaction interface between the surface product phase and the internal reactant . Because of the reaction occurring at the grain boundary, the grains of the internal Ag 2 CO 3 are coated by Ag 2 O.…”

Kinetic characterization of multistep thermal oxidation of carbon/carbon composite in flowing air

“…When the mutual interactions of the component reaction steps are negligible, the overall rate behavior of the oxidation reaction is expressed by the cumulative kinetic equation of the two reaction steps [35][36][37][38][39][40][41][42].…”

“…As A i is the constant for the single-step reaction, the f i (a i ) versus a i plot drawn using SB(m i , n i , p i ) determined by kinetic deconvolution analysis can be recognized as the experimental master plot, which illustrates the change in the rate behavior as the reaction advances at infinite temperature [39,42]. The experimental master plots are shown in Fig.…”

“…The aim of this study is to establish a test method for characterizing the compositional and structural properties of a carbon/carbon composite through kinetic analysis of its thermal oxidation process. Kinetic deconvolution analysis of the thermoanalytical data recently used to gain a detailed understanding of the various types of multistep solid-state and solid-gas reactions [35][36][37][38][39][40][41][42] was applied as the most suitable approach to describe the kinetic phenomena of the thermal oxidation process with the aid of the results of fundamental kinetic calculations and morphological observations of the samples during the reaction. This article reports a detailed comparison of the kinetic characteristics of the thermal oxidation processes of two different mechanical pencil leads manufactured by different companies as the first part of our study, which is expected to provide the necessary information to establish the methodology of kinetic analysis as a test method that is generally applicable to various carbon/carbon composites.…”