SAXS studies of morphology and microstructure of three-dimensionally ordered micromesoporous carbon

M. Dopita1, M. Vorokhta2, V. Holý1

1Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague 2, Czech Republic

2Department of Geochemistry, Institute of Rock Structure and Mechanics, Czech Academy of Sciences, V Holešovičkách 94/41, 18209 Prague 8, Czech Republic

milan.dopita@matfyz.cuni.cz

The three-dimensionally ordered micro-mesoporous (3DOmm) carbon with ordered spherical mesopores and micropores in the walls was synthesised and activated by treating it at high temperatures between 973-1173 K under CO2 flow. The evolution of morphology and microstructure of 3DOmm material was studied as a function of activation temperature using the SAXS. A relevant physical model was developed for the 3DOmm material: we assumed the spherical clusters of 3DOmm carbon having a mean size Rc and root mean square deviation of clusters radii sRc. The clusters are filled with an ensemble of spherical bubbles arranged in face centered cubic (fcc) lattice with centers of bubbles displaced by distance D and root mean square deviation sD. Individual bubbles having an internal core-shell structure with diameter R, root mean square deviation sR and shell thickness d. The SAXS intensity is assumed as a weighted sum of intensities calculated using the decoupling (DA) and local monodisperse (LMA) approximations. In studied samples the mean cluster radius Rc lies around 280 nm. The mean distance of the bubbles centers D is around 28 nm, which represents the lattice parameter of the fcc structure, around 40 nm. The mean bubble radius decreases from 9 nm in 3DOmm sample to about 4.8 nm in sample 3DOmm-1173 K.

Figure. 1. Measured (open blue circles) and fitted (red lines) SAXS profiles of the 3DOmm carbon materials (a). HRTEM micrographs of the 3DOmm sample (b).

1. M. Dopita, M. Emmel, A. Salomon, M. Rudolph, Z. Matěj, C.G. Aneziris, D. Rafaja, Carbon, 81 (1), (2015), 272-283.

2. M. Vorokhta, J. Morávková, M. Dopita, A. Zhigunov, M. Šlouf, R. Pilař, P. Sazama, Adsorption, 27, (2021), 1221-1236.

3. M. Vorokhta, J. Nováková, M. Dopita, I. Khalakhan, V. Kopecký, M. Švábová, Materials Today Sustainability, 24, (2023), 100509.