Order-disorder transition of an argon adsorbate in graphitic wedge pores

Formation of amorphous and quasi-two-dimensional microcrystalline structures of CO2 in activated carbon pores at low temperatures

“…Gases and fluid molecules confined in nanoporous materials can present unusual behavior in comparison to their common bulk state behavior, having changes in properties like 1) orientation of the molecules, 2) formation of ordered structure and/or crystalline structure, and 3) phase transition occurring at different temperatures and pressures [1,2]. Those properties above can be affected by the shape and size of the pore, the concentration of adsorbate, experimental temperature, and filling fraction, among others, and the understanding of it can provide valuable information about the storage of molecules, leading to a better understanding of it and, consequently, an enhancement of the current technologies that can be applied in different fields, like solid characterization, molecular separation, capture and storage and catalysis [1,[3][4][5], and, at the present chapter, the CCS [7,53].…”

“…">Research BackgroundFluid molecules confined in small spaces, like nanoporous materials, can present unusual behavior in comparison to their common in bulk state behavior, having changes in properties like i) orientation of the molecules, ii) formation of ordered structure, iii) phase transition occurring on different temperature and pressure [1,2]. The understanding of such properties and how they are affected by the shape and size of the pore, the concentration of adsorbate, temperature, the polarity of both adsorbent and adsorbate, molecular shape of adsorbate, among others, can provide valuable information about the storage of these molecules, leading to a better understanding of it and, consequently, an enhancement of the current technologies that can be applied in different fields, like solid characterization, molecular separation, capture and storage, catalysis [1,[3][4][5].An adsorbent solid containing micropores are receiving great attention in the research and industrial field, once it`s been shown to be promising solids to use as gas storage, since storage of H2 and methane, used as reactants in fuel cells, and CO2 capture and storage (CCS) [6]. By the IUPAC definition, microporous solids are those with have porous with widths smaller than 2 nm [7], and because of the small pore size, the potential energy from both walls interact with each other, enhancing the interaction between adsorbent-adsorbate in most of the cases [8].Activated carbons fibers (ACF) well established commercial nanoporous materials constitute slit-shaped microporous [8] with great surface area [9] and low production cost, which makes such materials attractive for being used on an industrial scale [6].…”

Low temperature adsorption of CO2 in carbonaceous wedge pores: a Monte Carlo simulation study

“…However, according to the X-ray analysis, the geometric structures of AC are rather complex and composed of crystallites that are stacked randomly and the confined spaces between the carbon stacks tend to be wedge shaped [22]. Thus, wedge pore is considered as a more realistic pore representation for the AC, which has non-uniform cross section [23][24][25][26]. The typical isotherm for a wedge pore possesses a Type C (in the de Boer classification) hysteresis loop, where its detailed shape depends on specific geometric configurations, including the range of pore widths, pore length and tilt angle.…”

“…This Type C hysteresis is not commonly observed experimentally because the wedge configuration tends to be masked by other effects, such as closed ends and ink-bottle structures. A stepwise character of desorption branch can be realized on the isotherm of argon in a wedge pore at 70 K or 77 K [24,25]. The hysteresis loop is stepped at the desorption boundary due to a transition between commensurate and incommensurate packing [25].…”

“…A stepwise character of desorption branch can be realized on the isotherm of argon in a wedge pore at 70 K or 77 K [24,25]. The hysteresis loop is stepped at the desorption boundary due to a transition between commensurate and incommensurate packing [25]. However, this feature is Xiu Liu and Allan Hua Heng Sim have contributed equally in this work.…”