Reverse Monte Carlo studies of nanoporous carbon from TiC

Abstract

The structures of nanoporous carbon prepared by chlorination of TiC at five different temperatures (700–1100 °C) have been studied by means of reverse Monte Carlo modelling of neutron diffraction data S(q), 0.3<q<10.5 Å−1, using an atomic configuration (8000 atoms) with a density corresponding to 0.62 of graphite. Four different starting models were tested: (i) random atom configuration, (ii) separated graphite sheets and (iii) two defect models created by removing atoms in a graphite structure to obtain the wanted density. To increase the feasibility of the resulting atom configurations, a number of hard and soft constraints were introduced into the software. The hard constraints were (i) a minimum C–C distance of 1.0 Å, (ii) a co-ordination constraint for nearest-neighbour distances of up to 1.6 Å to avoid zero- or single- co-ordinated atoms and (iii) no atoms between 1.7 and 2.1 Å to avoid small unphysical peaks in the radial distribution function. A soft constraint was centred C–C–C angles around 120° with a variance of 6°. The best fit between observed and calculated S(q) was obtained for the defect models. An evaluation of the porosity and surface area corresponding to the atomic configuration showed a significant difference between the 700 and 1000 °C samples and the one prepared at 1100 °C in agreement with HREM and sorption studies.

New Perspectives on the Structure of Graphitic Carbons

“…[40][41][42][43][44]. However, the interpretation of diffraction data from these highly disordered materials is not straightforward.…”

High selectivity of TiC-CDC for CO2/N2 separation

“…The pore structure can be further analyzed by small-angle scattering techniques like X-ray scattering (SAXS) or neutron scattering (SANS), which allows also probing closed pores. For titanium carbide-derived carbon (TiC-CDC), which is subject of this study, sorption isotherm analysis [16][17][18][19][20][21][22] and scattering [16,[23][24][25] results are discussed in literature, showing that TiC-CDC synthesized below 900 °C shows pore sizes in the range of carbon molecular sieves. Equilibrium CO 2 adsorption isotherms demonstrated that with TiC-CDC high CO 2 uptakes can be realized [26].…”

A molecular model for carbon black primary particles with internal nanoporosity

“…Based on the knowledge gained from experiments, simulation methods have been widely developed to model and characterize the nanostructures of carbon [33][34][35][36][37][38][39][40][41]. There are mainly two types of modeling approaches to build structures of nanoporous carbon materials, namely reconstruction methods and mimetic methods.…”

“…By using build units of carbon at various scales, detailed information of carbon structures can be gained from atomic to mesoscopic level. For instance, Reverse Monte Carlo (RMC) methods were extensively employed to retrace the atomic structures of carbon by comparison with several experimental measurements [34][35][36][37]. Beside the basic material properties, e.g.…”