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Non-graphitic carbons (NGCs) represent the most abundant class of sp 2 -hybridized carbon, materials (coal char coal, activated carbon, etc.). These carbons consist of small graphene layer stacks possessing significant structural disorder in both the single graphene sheets and the stacking. In this study an advanced evaluation approach for wide-angle neutron scattering (WANS) was developed, based on the method introduced by Ruland and Smarsly in 2002. In particular, we elucidated if and how the enhanced WANS data quality and larger values of the modulus of the scattering vector s-range affect the accuracy and the values of the size and disorder parametersbeing fitting parameters by themselvesin comparison to wide-angle X-ray scattering (WAXS), which is usually performed by laboratory equipment. We find a reasonable agreement for the parameters L a and L c , that is, the lateral dimension and stack height, within the error bars, whereas for the disorder parameters different results for WAXS and WANS were found, the origin of which is discussed. Thus, this study addresses the general issue of how reliably microstructural parameters can be determined from WAXS/WANS by fitting simulated WAXS and WANS curves, which are quality-impaired by added Gaussian noise at different levels and cut-off at different s-values. From this analysis, we estimated the minimal data quality required for a reliable NGC microstructural analysis based on WAXS/WANS. As an important finding, these simulations show that typical, standard WAXS laboratory setups are sufficient to provide reliable values for the most relevant structural parameters. Furthermore, pairdistribution function (PDF) analyses were performed on WAXS data obtained from a synchrotron facility. Comparing PDF and WAXS/WANS fitting analysis suggests the presence of small highly ordered oligoaromatic domains embedded in the larger graphene sheets, questioning the classical view on the NGC microstructure.

No abstract

Non-graphitic carbons (NGCs), such as glass-like carbons, pitch cokes, and activated carbon consist of small graphene layer building stacks arranged in a turbostratic order. Both structure features, including the single graphene sheets as well as the stacks, possess structural disorder, which can be determined using wide-angle X-ray or neutron scattering (WAXS/WANS). Even if WANS data of NGCs have already been extensively reported and evaluated in different studies, there are still open questions with regard to their validation with WAXS, which is usually used for routine characterization. In particular, using WAXS for the damping of the atomic form factor and the limited measured range prevent the analysis of higher-ordered reflections, which are crucial for determining the stack/layer size (La, Lc) and disorder (σ1, σ3) based on the reflection widths. Therefore, in this study, powder WANS was performed on three types of carbon materials (glass-like carbon made out of a phenol-formaldehyde resin (PF-R), a mesophase pitch (MP), and a low softening-point pitch (LSPP)) using a beamline at ILL in Grenoble, providing a small wavelength and thus generating WANS data covering a large range of scattering vectors (0.052 Å−1 < s < 3.76 Å−1). Merging these WANS data with WANS data from previous studies, possessing high resolution in the small s range, on the same materials allowed us to determine both the interlayer and the interlayer structure as accurately as possible. As a main conclusion, we found that the structural disorder of the graphene layers themselves was significantly smaller than previously assumed.

CarbX is an open‐source program designed for the analysis of wide‐angle X‐ray scattering (WAXS) data of non‐graphitic carbons (NGCs). As knowledge of their microstructure is crucial for tuning desired properties, an `easy‐to‐use' analysis tool is essential for effective research in this field. Using CarbX one can retrieve up to 14 microstructural parameters from a single WAXS pattern without having to master the associated complicated mathematics. CarbX was developed to serve as a convenient graphical user interface, translating a complex evaluation algorithm introduced by Ruland & Smarsly [J. Appl. Cryst. (2002), 35, 624–633] into software which can be operated by non‐experts. Besides the core functionality of displaying data and manually fitting WAXS curves by user‐editable parameters, CarbX offers additional features such as visualization of the deviation between data and fit, the possibility to choose the wavelength used in the measurement, and automatic fitting (using Wolfram Mathematica). One of the key features of the comfortable usability is the functionality to display templates. This allows the user to visually compare measurement data with typical types of NGC WAXS curves which are presented graphically around the measurement data. The authors believe that this program will provide a useful tool for scientists dealing with the characterization of NGCs.