On the Highly Ordered Graphene Structure of Non-Graphitic Carbons (NGCs)—A Wide-Angle Neutron Scattering (WANS) Study

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.

Lignin-Derived Mesoporous Carbon for Sodium-Ion Batteries: Block Copolymer Soft Templating and Carbon Microstructure Analysis

“…It is worth mentioning that wide-angle neutron scattering (WANS) and the results applied by Osswald et al 16 provide a higher accuracy compared to WAXS analysis (Schuepfer et al 17 17 and this study) and WANS (Osswald et al 16 ) of lignin-derived carbons (this study) and comparable PF-R carbons (Schuepfer et al 17 confined scattering range of s in typical Cu-Kα-WAXS laboratory instruments. 16 Typically, L a is overestimated, and σ 1 shifted to higher values for such typical XRD setups. 16,54 Pfaff et al 54 specified a maximum deviation of approximately 25% as the error range, determining L a with standard laboratory WAXS setups.…”

“…Yet, valid structure parameters depending on the signal width are only obtained by the applied evaluation technique if at least two reflections of the same lattice plane family caused by intralayer, respectively interlayer, scattering can be fitted precisely, i.e., for instance, the ( 10) and ( 20) reflections. 16 Considering the (00l) reflections, this is not the case, as noted for the (004) reflection. Together with the finite measurement range of standard WAXS laboratory setups limiting the number of recorded reflections, this shows the limitations of possible microstructure evaluation within this study, causing the stacking height L c only to be determined in terms of order of magnitude.…”

“…17,44,46 Next to comparing templated and nontemplated lignin-derived carbon, an appealing comparison can be made with nontemplated lignin-phloroglucinol-based carbon (this study) and phenol-formaldehyde resin-based carbons (PF-R) reported by Schuepfer et al 17 templated carbons. 16,17 Hence, it can be stated already that introducing templates causes restriction in graphene layer (re)organization during thermal treatment. Also, all different polymers seem to affect and hinder graphitization to the same extent.…”

“…Therein, the dependency of the G band position on the average layer extension L a was discussed with empirical and theoretical relationships. As the G band position is nondispersive, comparing the Raman and WAXS analysis results in this study with the universal master curves of the abovementioned literature 16,17 (Figure 8) allows further assessment of the validity of microstructure analysis of lignin-based carbons.…”

Insights of the ultralow wear and low friction of carbon fiber reinforced PTFE in inert trace trace moisture environment

“…Moreover, the friction between the graphite samples and the transferred graphite is evidently high in the tested trace moisture environment. Due to the similar structure of graphite and non-graphitic (turbostratic) carbon [12,13,57,58] and their similar tribological behavior [22,27,59], it is highly plausible that the poor adhesion between iron uoride and carbon is key to the low friction in the analyzed CF/PTFE -steel tribosystem.…”