Characterization of Carbon/Carbon Composites by Kinetic Deconvolution Analysis for a Thermal Oxidation Process: An Examination Using a Series of Mechanical Pencil Leads

Abstract

The thermal behaviors of carbon/carbon (C/C) composites in flowing air were investigated on the basis of mechanical pencil leads with different hardness values and diameters as a model system. Two separated mass-loss processes were observed during heating the mechanical pencil leads in air, which are attributed to the evaporation–decomposition of an impregnation agent and the subsequent thermal oxidation of the residual C/C composite. The thermal behaviors were invariant among the mechanical pencil leads with different diameters, but they systematically changed with hardness. Variations in the thermal behaviors can be quantified by the mass-loss value during the evaporation–decomposition of the impregnation agent, in addition to the kinetic deconvolution analysis that was applied to the multistep thermal oxidation process of carbon components with different reactivities. These results correlate the thermal behavior with the compositional and structural characteristics of C/C composites, which can be useful for characterization and product control.

Physico-geometrical kinetics of the thermal dehydration of sodium carbonate monohydrate as a compacted composite of inorganic hydrate comprising crystalline particles and matrix

“…Composites of multiple materials with the same compositional and crystallographic properties, but different morphological properties and reactivities are interesting as alternative compacted agglomerates. One example is the carbon-carbon composite used in mechanical pencil lead, 30,31 which is composed of graphite crystalline particles and a graphite matrix produced by calcinating a graphite-polymer mixture in an inert gas atmosphere. The thermally induced oxidative decomposition of carbon-carbon composites exhibits a partially overlapping multistep mass loss process owing to the reactions of different carbon components with different reactivities.…”

“…The thermally induced oxidative decomposition of carbon-carbon composites exhibits a partially overlapping multistep mass loss process owing to the reactions of different carbon components with different reactivities. [30][31][32][33][34][35][36] Because CO 2 is the only product of the oxidative decomposition under air flow, the multistep mass loss process is described based on a cumulative kinetic equation determining the contributions and kinetic parameters of each component mass loss step. 30,31 However, when a composite of crystalline particles and a matrix with the same composition but different reactivities decomposes to produce solid and gaseous products, the solid product layer and gaseous products of the starting reaction may impact the kinetics of the subsequent reaction step, increasing the complexity of the overall kinetic behavior.…”

“…[30][31][32][33][34][35][36] Because CO 2 is the only product of the oxidative decomposition under air flow, the multistep mass loss process is described based on a cumulative kinetic equation determining the contributions and kinetic parameters of each component mass loss step. 30,31 However, when a composite of crystalline particles and a matrix with the same composition but different reactivities decomposes to produce solid and gaseous products, the solid product layer and gaseous products of the starting reaction may impact the kinetics of the subsequent reaction step, increasing the complexity of the overall kinetic behavior. Such a compacted composite of crystalline particles and matrix was identified through careful literature review.…”

Thermal Decomposition of Maya Blue: Extraction of Indigo Thermal Decomposition Steps from a Multistep Heterogeneous Reaction Using a Kinetic Deconvolution Analysis

“…Using the results of KDA, the overall reaction process, under a specific heating condition, can be reproduced or simulated. By comparing the results of KDA among a series of samples and under different reaction conditions, characteristics of multistep kinetic behavior can be correlated to different components of a composite sample [23,24,25,26] and specific reaction conditions [27,28]. KDA is also used to extract kinetic information about a selected reaction step from the overall process [29,30].…”