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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. [ABSTRACT FROM AUTHOR]

We present a free software script operating in GNU Octave for the refinement of wide-angle X-ray and neutron scattering (WAXS/WANS) data of non-graphitic carbons (NGCs). The refinement script (OctCarb) is based on the evaluation approach of Ruland and Smarsly (2002). As result, up to 14 physically meaningful parameters such as the layer extension La, the stack height Lc, as well as the degree of disorder of the graphenes and their stacking are obtained through a well-established fitting routine. In addition, background scattering based on specific physical phenomena and different correction parameters such as polarization and absorption can be considered. Since the complex mathematical calculations are implemented and performed in the background, with only a few settings to be made, the software was designed to be usable by inexperienced users. As another key feature, Octave and thus OctCarb run on all common operating systems (Windows, MacOS and Linux), and can even be used on high-performance computing clusters (HPCs) to perform multiple calculations at once. In addition to this, the whole refinement can be performed within minutes, and it is possible to tweak and optimize it for special purposes and measuring geometries. These features make OctCarb useful for all scientists dealing with the characterization of NGCs by X-ray or neutron scattering techniques. [ABSTRACT FROM AUTHOR]

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.

We present a free software script operating in GNU Octave for the refinement of wide-angle X-ray and neutron scattering (WAXS/WANS) data of non-graphitic carbons (NGCs). The refinement script (OctCarb) is based on the evaluation approach of Ruland and Smarsly (2002). As result, up to 14 physically meaningful parameters such as the layer extension La, the stack height Lc, as well as the degree of disorder of the graphenes and their stacking are obtained through a well-established fitting routine. In addition, background scattering based on specific physical phenomena and different correction parameters such as polarization and absorption can be considered. Since the complex mathematical calculations are implemented and performed in the background, with only a few settings to be made, the software was designed to be usable by inexperienced users. As another key feature, Octave and thus OctCarb run on all common operating systems (Windows, MacOS and Linux), and can even be used on high-performance computing clusters (HPCs) to perform multiple calculations at once. In addition to this, the whole refinement can be performed within minutes, and it is possible to tweak and optimize it for special purposes and measuring geometries. These features make OctCarb useful for all scientists dealing with the characterization of NGCs by X-ray or neutron scattering techniques.

Polycarbonate (PC) is a material that is used in many areas: automotive, aerospace engineering and data storage industries. Its hardness is of particular importance, but some applications are affected by its low wettability or scratch susceptibility. This can be changed either by blending with other polymers, or by surface modifications, such as the application of an amorphous hydrogenated carbon layer (a-C:H). In this study, individual a-C:H layers of different thicknesses (10-2000 nm) were deposited on PC by RF PECVD. Both the layer morphology with AFM and SEM and the bonding states of the carbon on the surface with synchrotron-assisted XPS and NEXAFS were studied. The aim was to investigate the coatability of PC and the stability of the a-C:H. Special attention was paid to the interlayer region from 0 to 100 nm, since this is responsible for the layer to base material bonding, and to the zone of dehydrogenation (from about 1000 nm), since this changes the surface composition considerably. For PC, the interlayer was relatively small with a thickness of only 20 nm. Additionally, a correlation was found between the evolving grain structure and the development of the C-H peak according to NEXAFS C K-edge measurements. [ABSTRACT FROM AUTHOR]

We study the transformation from molecular to crystalline of (non-)graphitic carbons synthesized from organic precursors by heat-treatment. Easy assessment of structural properties resulting from heat-treatment protocols is mandatory for industrial process monitoring. We demonstrate that Raman spectroscopy, in particular, the Raman lineshape analysis of G and D mode, offers quick assessment of the average sheet size of such carbons. We validate this method by performing Raman, WAXS and EPR measurements of series of resin and pitch-based carbons synthesized. The crystallite sizes of the WAXS analysis for the individual samples are related to corresponding positions and linewidths of G and D Raman modes and show excellent agreement between experiment and modelling from large sizes down to 4 nm. The theoretical master curves are independent of the precursor used in the synthesis, in contrast to models for the intensity ratio of D and G band versus size. We show that the latter are not universally valid and differ for each class of precursors. For sizes below 4 nm, our lineshape model fails as it is based on the bandstructure and phonon dispersions of ideal graphene. Thus, 4 nm corresponds to the fundamental transition from molecular to crystalline character for non-graphitic carbons. Image 1 [ABSTRACT FROM AUTHOR]

• Low-cost semi-coke was converted to high-performance sodium-ion battery anodes. • Synergetic effect of pre-carbonization and NaOH etching bring an enhanced capacity. • An effective method to convert graphite-like to pseudo-graphitic carbon is proposed. • The sample delivers a reversible capacity of 326.8 mAh/g with an ICE of 84.7 %. • The increased plateau capacity of ∼ 47 mAh/g for non-graphitic carbon was obtained. The practical application of sodium-ion batteries is mainly hindered by relatively low energy density, which can be effectively overcome by increasing the pseudo-graphitic content in non-graphitic carbon (NGC) anodes. Herein, a simple and efficient strategy was reported to promote the growth of pseudo-graphitic domains in NGC thanks to the synergistic effect of pre-carbonization and NaOH etching using semi-coke as precursor. Based on pre-carbonization at 800 °C and NaOH etching with NaOH/carbon ratio of 0.5 at 600 °C, the resultant NGC (FC-800–0.5–600) exhibits a 13 % increase in percentage of pseudo-graphitic structure meanwhile 14 % decrease for graphite-like structure, but similar content of highly disordered structure compared with its counterpart. Notably, although similar in sloping capacity, FC-800–0.5–600 possesses much higher plateau capacity (<0.1 V) of 218.6 mAh g−1 than its counterpart (174.9 mAh g−1), which is attributed to the enhanced "interlayer intercalation" effect related with pseudo-graphitic structure. Thus, FC-800–0.5–600 can deliver an impressive reversible capacity of 326.8 mAh g−1 at 20 mA g−1, together with a considerable ICE of 84.7 %. This work proposed an effective strategy to increase pseudo-graphitic structure content in NGC, providing a rational guide for designing high-performance anodes in SIBs for practical use. [ABSTRACT FROM AUTHOR]

A non-graphitic carbon anode was successfully developed, demonstrating superior K-storage of 250 mAh/g at 50 mA/g after 500 cycles and 170 mAh/g at 1000 mA/g after 400 cycles along with 0.0078% and 0.014% capacity loss for per cycle after 20 cycles, respectively, which performance is credited to the rapid reaction kinetics ensured by the robust inorganic-rich SEI in the optimized 3M KFSI/EC+DEC electrolyte with AGGs-dominated solvation structure. [Display omitted] • A non-graphitic carbon anode has been successfully developed. • A reversible capacity of 250 mAh/g with 0.0078% per cycle decline is obtained. • Enhanced K-storage reaction kinetics in optimized electrolyte was revealed. • An inorganic-rich SEI was derived from AGGs-dominated solvation structure. Effectiveness of non-graphitic carbon materials with disordered structures in potassium storage has promote it as high-performance K-storage anodes of potassium-ion batteries (PIBs). However, there are defects that have not been adequately addressed, in which unstable K-storage performance along with sluggish reaction kinetics usually result from the severe interfacial side reactions and large K+ radius. Herein, rational electrolyte regulation has been treated as a promising strategy to achieve superior K-storage performance for the developed non-graphitic carbon from covalent-organic-frameworks (COFs). Specifically, it give rise to excellent cycle stability of 250 mAh/g after 500 cycles at 50 mA/g and high rate performance of 170 mAh/g after 400 cycles at 1000 mA/g, respectively. The boosted K-storage performance is ascribed to the fast interfacial reaction kinetics dependent on inorganic-rich and stable solid electrolyte interphase (SEI) that derived from the aggregates-dominated solvation structures in the optimized concentrated electrolyte. These findings suggest opens up an effective strategy from electrolyte chemistry that significantly affected SEI for advancing high-performance PIBs. [ABSTRACT FROM AUTHOR]

A composite of Fe/Fe 3 C and N-doped graphitic carbon (Fe/Fe 3 C@NG) was prepared and used as a catalyst for the activation of peroxymonosulfate (PMS) toward the oxidative degradation of Norfloxacin (NOF). It was observed that Fe/Fe 3 C@NG behaved as a bifunctional material, showing both good adsorption ability and catalytic activity. The maximum adsorption capacity of Fe/Fe 3 C@NG for NOF was evaluated as 0.13 mmol g −1 . Under given conditions (NOF concentration 0.1 mmol L −1 , catalyst load 0.1 g L −1 and PMS addition 1 mmol L −1 ), the degradation of NOF was almost completely achieved in 20 min with a degradation rate constant of 0.22 min −1 . A non-radical mechanism was proposed for the activation of PMS by Fe/Fe 3 C@NG by the scavenging test, EPR and chronoamperometry analysis. The fast and complete degradation of NOF was achieved via a rapid electron transform, in which both PMS and NOF molecular were adsorbed on the surface of Fe/Fe 3 C@NG and PMS was activated by obtaining electrons from NOF to oxidize NOF. The present study provides a green bifunctional catalyst for the oxidative removal of organic pollutants in various environmental media. [ABSTRACT FROM AUTHOR]

This study investigates the effects of inserting amorphous carbon (a-C) layers between the Al electrode layer and the ZnO insulator layer in Al/ZnO/Al heterostructures on resistive switching (RS) therein. The inserted a-C layers can play an important role to stabilize RS behavior for random access memory performance. The complex impedance spectra of Al/ZnO/Al devices with and without a-C inserted layers examined to probe the characteristics of their conducting mechanism. The formation of meta-stable a-CO x after forming process caused repeatable redox reaction at interfaces, critically affecting RS behaviors. [ABSTRACT FROM AUTHOR]

The analysis of the wide-angle X-ray scattering (WAXS) data of non-graphitic carbons is challenging due to the broad and overlapped ( hk)- and (00 l)-reflections. A recently developed advanced analysis method developed by Ruland and Smarsly allows for the fitting of the WAXS data by a continuous model function, providing a detailed insight into the sp2-carbon microstructure. Obtaining parameters like the graphene layer extent La, the average stack height Lc and disorder effects permits the quantification of microstructural features. Firstly, this publication gives a brief review over historical und recent developments regarding the evaluation of the WAXS of disordered carbons. Secondly, the applicability of this algorithm to carbon samples possessing a substantial degree of disorder is tested by investigating activated carbons, heat treated coal tar pitch and furfuryl alcohol. It is seen that several structural parameters are determined with reasonable accuracy and thereby the influence of the precursor and the temperature on the resulting carbon microstructure is identified. The decrease in disorder within the 2D graphene lattice and in the stacking of the layers at higher synthesis temperatures is quantified. Moreover, this study reveals that the graphene layer extent La is only about a few nanometers in size, showing that typical non-graphitic carbons used for diverse applications possess quite small dimensions of graphene stacks. [ABSTRACT FROM AUTHOR]

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. Multi-walled carbon-nanotubes (MWCNTs) as cathode-catalyst support are found to enhance long-term stability of platinum catalyst (Pt) in relation to non-graphitic carbon. In addition, highly graphitic MWCNTs (G-MWCNTs) are found to be electrochemically more stable than pristine MWCNTs. This is because graphitic-carbon-supported-Pt (Pt/MWCNTs) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported-Pt (Pt/C) cathodes in PEFCs during accelerated stress-test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance, and charge-transfer resistance are monitored through cyclic voltammetry, cell polarization, and impedance measurements, respectively. The extent of crystallinity, namely amorphous or graphitic nature of the three supports, is examined by Raman spectroscopy. X-ray diffraction and transmission electron microscopy studies both prior and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/G-MWCNTs and Pt/MWCNTs cathodes in relation to Pt/C cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt particles. It is also found that with increasing degree of graphitization, the electrochemical stability for MWCNTs increases due to the lesser surface defects. [ABSTRACT FROM AUTHOR]

Abstract: The properties of LiCoPO4-non-graphitic carbon foams (LCP-NGCF) composites are reported. The composites are treated at 300°C for different times (t, from 0 to 12h) in air, then at 730°C for 12h in nitrogen. The diffraction analysis revealed LiCoPO4 as major crystalline phase, Li4P2O7 and Co2P (t =0h), Co2P (t >0h) as secondary phases. The morphology consists of crystalline “islands” with spongy-like features on the surface (for t =0h) and with acicular crystallites of different dimensions (2–20μm) for t≥0.1h. The voltammetric curves show reduction potential values between 4.40V and 4.60V. The LCP-NGCF composites deliver a discharge specific capacity of 100mAhg−1 (t =0h, discharge rate of C/25 and RT) and of 65mAhg−1 (t >0h). The ac-impedance analysis reveal the formation of SEI-layer after high annealing times, which disfavors the kinetics of the Li-(de)intercalation processes. [Copyright &y& Elsevier]

IR spectroscopy and X-ray diffraction study of insoluble organic matter (IOM) showed that the structural characteristics of its carbonic component depend on the composition of original organic matter and degree of its catagenesis. [ABSTRACT FROM AUTHOR]

Abstract: We report on the structure of a set of diesel exhaust samples that were obtained from reference diesel fuel and diesel fuel mixed with ferrocene. Characterization was carried out with X-ray absorption spectroscopy (C(1s) NEXAFS) and wide-angle X-ray scattering (WAXS). The reference diesel soot shows a pronounced graphite-like microstructure and molecular structure, with a strong (002) graphite Bragg reflex and a strong aromatic Cce at 285eV. The mineral matter in the reference soot could be identified as Fe2O3 hematite. The soot specimen from the diesel mixed with ferrocene has an entirely different structure and lacks significantly in graphite-like characteristics. NEXAFS spectra of such soot barely show aromatics but pronounced contributions from aliphatic structures. WAXS patterns show almost no intensity at the Bragg (002) reflection of graphite, but a strong aliphatic γ-side band. The iron from the ferrocene transforms to Fe2O3 maghemite. [Copyright &y& Elsevier]

Abstract: The electron spin resonance (ESR) spectral change of Li-doped polyacenic semiconductive (PAS) materials has been examined before and after heat treatment to elucidate the decrease in the discharging amount of the heat-treated Li-doped PAS electrodes. Decrease in the peak-to-peak line width of the ESR lineshape has been observed for all the Li-doped PAS electrodes, indicating partial degradation of Li-dopants. These results strongly suggest the existence of two kinds of Li-dopants in the highly Li-doped PAS electrodes: heat-resistant and heat-labile ones. [Copyright &y& Elsevier]

To elucidate the lithium-ion kinetics at a non-graphitizable carbon electrode, lithium-ion transfer at the interface between a non-graphitizable carbon electrode and a liquid electrolyte was studied by AC impedance spectroscopy. Non-graphitizable carbon prepared at 2273K was used as a working electrode. After potential cycling between 3.0 and 0V, Nyquist plots gave a semi-circle at 3.0V vs. Li/Li+. At this potential, no lithium-ion insertion and extraction occurred, and therefore the semi-circle is due to surface film resistance. At potentials below 0.9V, impedance spectra gave two semi-circles. The semi-circle in the middle to lower frequency region can be assigned to the charge transfer resistance due to lithium-ion transfer at the non-graphitizable carbon electrode/electrolyte interface. The temperature-dependence of the resistance showed Arrhenius-type behavior and gave an activation energy of about 70kJmol−1 regardless of the electrolyte used, indicating that a high activation barrier exists at the non-graphitizable carbon electrode/electrolyte interface for lithium-ion transfer. Non-graphitizable carbon treated by hot isostatic pressing (HIP) gives a smaller activation energy of about 60kJmol−1. Therefore, the structure of non-graphitizable carbon significantly affects lithium-ion transfer kinetics at a non-graphitizable carbon electrode/electrolyte interface. [Copyright &y& Elsevier]

Using semi-empirical molecular orbital calculations, Li ion storage states in heteroatom-substituted carbon materials were studied. Heteroatom-substituted polycyclic hydrocarbon molecules XC53H18 (X&z.dbnd6;B, N, Si, P) were adopted as models of heteroatom-substituted graphene sheets. Electronic structures of the XC53H18 sheets and the interactions between Li ions and the sheets were investigated. Various storage states of Li ions between two XC53H18 sheets were examined. Results indicate that double Li ion layer storage states were stabilized by Si, B, and P substitution, a fact which seems advantageous to achieve large storage capacity. Moreover, we found a single Li ion layer storage state that had a larger capacity than the theoretical maximum for graphitic carbons (372 mAh/g), between two SiC53H18 sheets. For the single layer storage state, the interlayer distance between two SiC53H18 sheets should be small enough to prevent intercalation of electrolyte species. Such storage state is advantageous to reduce irreversible capacity. Mulliken charges of Li ions were almost 1, a fact which is expected to cause hysteresis reduction in charge–discharge cycling. The Si-substituted carbon material seems promising to use as carbon anodes. [Copyright &y& Elsevier]

Amorphous carbon materials for lithium ion battery anodes which contain a small amount of Li2CO3 were prepared by three methods. The obtained materials were characterized using X-ray diffraction (XRD) analysis, Raman spectroscopy and CO2 adsorption experiments. Although the XRD profiles and Raman spectra of these materials were similar to those of carbon materials synthesized with no addition, the amount of CO2 adsorbed was largely decreased by Li2CO3 addition. These results suggest that the micropores in these materials were plugged and/or filled with Li2 CO3. Galvanostatic lithium charging and discharging experiments showed that the irreversible capacity of the material can be significantly decreased by Li2CO3 addition, which is thought to be due to the plugging of the pore inlets by Li2CO3. Moreover, it was also found that the reversible capacities of the materials can be increased by adjusting both the amount of Li2CO3 addition and carbonization temperature. [Copyright &y& Elsevier]

A novel carbon with vesicular, hierarchical structure was synthesized via a direct, micelle templating strategy. This vesicular carbon exhibits a wormlike morphology, very thin shells (5–30 nm) and mesopores of 2–4 nm within the shell that are perpendicular to the walls of the carbon vesicles. The structure of this novel vesicular carbon was verified by X-ray diffraction and electron microscopy. [Copyright &y& Elsevier]

The chemical behavior of phenanthrene during a reaction triggered by shock waves, and its influence on the physical property of phenanthrene were studied over the pressure range of 7.9–32.0 GPa. Chemical analyses showed that shocked phenanthrene included insoluble carbonaceous material containing amorphous carbon, polycyclic aromatic hydrocarbons (PAHs) with molecular weights ranging from 128 to 356, and unreacted phenanthrene. No diamond and fullerenes were detected in the shocked phenanthrene. The results indicate that reactions triggered by shock wave are dehydrogenation, which causes carbonization and radical addition reactions, and ring cross-linking. Carbonization is the most dominant and rapidly proceeded above 20.0 GPa. Thus, an abrupt increase of compressibility of phenanthrene above 20.1 GPa previously reported is caused by the drastic carbonization. [Copyright &y& Elsevier]

Three-dimensional polyphenylene dendrimers (PDs) can be prepared in ways that enable control of their shape. Their structures may be used as scaffolds with a wide variety of functionality, enabling them to be used as functional nanoparticles with a large range of possible applications, ranging from light emitting devices to biological sensors or drug delivery tools. As PDs have been synthesized only recently, their structural and chemico-physical characterization is still in its infancy. Accordingly, in this paper the shape and internal organization of three PD families based on three different cores were probed by accurate, atomistic molecular dynamics simulations (MD). Particular care was taken to ensure complete structural equilibration by implementing an MD simulated annealing protocol prior to evaluation of the molecular structure and dynamics. All dendrimer families were found to be characterized by molecular dimensions in the nano-range, and by a shape-persistent, non-spherical structure, of molecular fractal dimension around 2.5–2.6, and of surface fractal dimension practically constant and almost equal to 2 with increasing generations in all cases. The MD analysis revealed also that, for this type of dendrimers, the starburst limited generation is presumably located in correspondence of the third generation. [Copyright &y& Elsevier]

Semi-empirical molecular orbital calculations were carried out to clarify storage states of Li ions in amorphous carbon anodes of Li ion batteries. Storage states of Li ions between two graphene sheets were investigated and a favorable structure for a carbon anode to produce large reversible and small irreversible capacities is discussed. A polycyclic hydrocarbon molecule, C54H18, was used as a model of a graphene sheet. Relations between the interlayer distance of two graphene sheets and the storage state of Li ions were investigated, and preferable interlayer distances for specific numbers of Li ions were estimated. In particular, storage states with all Li ions on the basal area were treated, because the amount of basal carbons should be larger than that of edge carbons. The charge distribution of Li ions was also investigated. Calculated results suggested that a storage state in which a double Li ion layer was formed was preferable to achieve a larger capacity than the theoretical maximum capacity of graphitic carbons (372 mAh/g) and to reduce hysteresis in the charge–discharge process. Moreover, suitable distance between edges of graphene sheets to prevent the intercalation of electrolyte species was discussed. A recommended structure of carbon anodes suitable for the double Li ion layer storage and prevention of the intercalation of electrolyte species is proposed. [Copyright &y& Elsevier]