Kinetic analysis of the multistep thermal decomposition of Maya Blue-type pigments to evaluate thermal stability
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Kinetic analysis of the multistep thermal decomposition of Maya Blue‑type pigments to evaluate thermal stability Yui Yamamoto1 · Takahiro Okazaki1 · Yasuhiro Sakai1 · Shun Iwasaki1 · Nobuyoshi Koga1 Received: 7 October 2019 / Accepted: 2 January 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This study aimed to evaluate the practical usefulness of kinetic deconvolution analysis (kDa) as a means to obtain the kinetic information on specific reaction steps that characterize the thermal properties of materials for various purposes. The partially overlapping multistep thermal decomposition of Maya Blue (MB)-type pigments was used as an example reaction. Red and yellow MB-type pigment materials, composed of a fibrous clay mineral and an organic dye, were synthesized using palygorskite and sepiolite as the clay minerals and Methyl Red and Alizarin as red and yellow dyes, respectively. The multistep thermal decompositions of the MB-type pigments were investigated using thermogravimetry. The thermoanalytical data were deconvoluted into individual component reaction steps using an empirical kDa technique based on a cumulative kinetic equation that considers the contribution of each reaction step to the overall thermal decomposition. By comparing the kDa results for the thermal decomposition of the composites with those for the decomposition of pure palygorskite and sepiolite, the thermal decomposition steps for the incorporated organic dyes were extracted from the multistep thermal decompositions of the MB-type pigments. Finally, the thermal stabilities of MB-type pigments comprising different clay minerals and organic dyes were compared using the kinetic results extracted for the reaction step associated with the decomposition of the organic dyes. Keywords Thermogravimetry · Thermal decomposition · Maya Blue-type pigment · Kinetic deconvolution analysis · Thermal stability
Introduction Fibrous clay minerals such as palygorskite and sepiolite are potential candidates for the preparation of composite materials comprising both inorganic compounds and organic molecules, where the micropores in the clay mineral allow the incorporation of guest molecules that exhibit specific functionality as catalysts [1–12], heat storage materials [13–21], and pigments [22–24]. The guest molecules in clay mineral-based composite materials of this type exhibit higher chemical and thermal stabilities than the guest compound Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10973-020-09278-7) contains supplementary material, which is available to authorized users. * Nobuyoshi Koga nkoga@hiroshima‑u.ac.jp 1
Department of Science Education, Graduate School of Education, Hiroshima University, 1‑1‑1 Kagamiyama, Higashi‑Hiroshima 739‑8524, Japan
alone because of its incorporation into the micropores of the host. The quantitative evaluation of the thermal stabilities of such composite materials is necessary for their practical application, and thermal analysis is one of the most useful
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