Turbostratic Carbon Research Articles

Regeneration of spent graphite via graphite-like turbostratic carbon coating for advanced Li ion battery anode

Recycling spent graphite (SG) from lithium-ion batteries is an effective approach to reduce resource waste and address environmental issues. The main reasons for the capacity degradation of graphite anode are the structural destruction and changes in surface composition during the cycling process. However, repairing the graphite with satisfactory electrochemical properties remains a significant challenge due to the lack of efficient recycling methods. Herein, a low-temperature magnesium catalytic method is developed to reconstruct turbostratic carbon coating and repair defects in SG at 900 °C. The dense turbostratic carbon not only effectively repairs the surface damage of the SG and mitigates the occurrence of side reactions but also improves the Li+ and electron transfer kinetics of SG. The regenerated graphite anode exhibits high initial Coulombic efficiency (ICE) of 86.2 %, a high capacity of 350 mAh g−1 after 500 cycles at 0.5 C with a capacity retention of 96.5 %, which reaches the requirements of commercial applications. Furthermore, a techno-economic analysis shows that this strategy has higher environmental and economic benefits compared to conventional recycling methods.

Evolutionary Zn ion storage mechanism of hierarchical nanotubular spinel FeV2O4 for Zinc–Metal full cells

A fundamental understanding about the evolution of energy storage mechanism by the structure reconstruction during initial cycling is crucial in establishing their correlation with the unprecedented electrochemical performance of electrodes. Herein, we demonstrate evolutionary zinc (Zn) ion storage mechanism and kinetics of the hierarchical nanotubular FeV2O4 (FeV2O4@NT) coated by turbostratic carbon layers through the anodic hydration-induced crystal reconstruction, where the smaller nanocrystalline FeV2O4 spinel phase was embedded into the newly-formed amorphous V-O-Fe phase at the heterointerface. These FeV2O4@NT cathodes achieved the synergistically combined energy storage mechanism of intercalation and pseudocapacitance for the greatly improved electrochemical performance of pouch full cells, which was not achieved by existing spinel oxides. With the polyoxometalate modified Zn metal anode at the optimized condition of 3.0 M Zn(OTf)2/(ACN/H2O-0.15) in the voltage range of [0.3–1.6 V (vs. Zn/Zn2+)], the POM-Zn||FeV2O4@NT full cells achieved a high capacity of 456.8 mAh g–1 at 200 mA g–1, high rate capacity of 222.0 mAh g−1 even at 10,000 mA g–1, and a large energy density of 337.5 Wh kg–1. Furthermore, the chemical pillar and Fe vacancies in the amorphous V-O-Fe phase allowed FeV2O4@NT electrode to achieve a low capacity decay rate of 0.0152 % per each cycle over 1,000 cycles.

Turbostratic carbon nanofibers produced from C2HCl3 over self-dispersing Ni-catalyst doped with W and Mo

In this research, a self-dispersing 92Ni-4Mo-4W catalyst showing high productivity towards the H2-assisted synthesis of turbostratic carbon nanofibers was proposed. The effect of reaction temperature on the efficiency of 92Ni-4Mo-4W alloy in the decomposition of trichloroethylene was studied. It was found that in the temperature range of 580–620 °C, the most rapid destruction of the initial alloy followed by the growth of carbon material is realized. This is confirmed by the minimum induction period (9–11 min) and the maximum carbon yield (95–107 g/gcat). As revealed, the catalytically active particles of submicron size contain uniformly distributed Ni, Mo, and W. It is demonstrated that the decomposition of trichloroethylene over the 92Ni-4Mo-4W catalyst results in the formation of a turbostratic carbon material with a segmented structure, containing a minimum quantity of amorphous carbon and possessing high textural characteristics (specific surface area of 330–410 m2/g; pore volume of 0.48–0.58 cm3/g).

Structure–property relations of silicon oxycarbides studied using a machine learning interatomic potential

AbstractSilicon oxycarbides show outstanding versatility due to their highly tunable composition and microstructure. Consequently, a key challenge is a thorough knowledge of structure–property relations in the system. In this work, we fit an atomic cluster expansion potential to a set of actively learned density‐functional theory training data spanning a wide configurational space. We demonstrate the ability of the potential to produce realistic amorphous structures and rationalize the formation of different morphologies of the turbostratic free carbon phase. Finally, we relate the materials stiffness to its composition and microstructure, finding a delicate dependence on Si‐C bonds that contradicts commonly assumed relations to the free carbon phase.

A new perspective for potassium intercalation chemistry in graphitic carbon materials

Potassium intercalation mechanism in graphitic carbon materials is known to be a staging reaction similar to that of lithium, despite their antithetic intercalation trend in turbostratic carbon (TBC) materials. This study clarified the distinctive potassium intercalation behavior of graphitic carbon materials with different local microstructures through a systematic comparative investigation. In contrast to the monotonic stacking sequence of lithium-intercalated graphitic carbon materials, multiple potassium-intercalated graphitic configurations can be formed by potassiation at an energy level similar to the theoretical KC8 formation. Accordingly, potassium intercalation in TBC materials can result in a theoretical low-voltage plateau capacity without long-range ordering. In contrast, the high energy cost for the threshold number of initial potassium insertions significantly hinders two-phase potassium intercalation in well-ordered graphite-like carbon materials, leading to a poor plateau capacity. Hence, potassium intercalation is more favorable in a turbostratic microstructure that includes intrinsic defects, whereas the presence of too many intrinsic defects reduces the polyhexagonal carbon plane for turbostratic intercalation, leading mainly to solid-solution potassium intercalation. Based on these results, the potassium intercalation mechanism in graphitic carbon materials can be classified into three different types such as 1) solid-solution intercalation, 2) turbostratic intercalation, and 3) two-phase intercalation.

Effects of in situ formed nanostructures on the structure and properties of C/SiOC composites

AbstractIn this paper, Ni was introduced into the matrix of carbon fiber reinforced SiOC (C/SiOC) composites by the precursor infiltration and pyrolysis method to catalyze the generation of in situ formed nanostructures including carbon nanotubes (CNTs), turbostratic carbon, and SiC. The effect of in situ formed nanostructures catalyzed by Ni on the properties of the C/SiOC composites was investigated. The results demonstrated that the presence of in situ formed nanostructures in the matrix improved the densification and mechanical properties of C/SiOC composites. In addition, the incorporation of in situ formed nanostructures facilitated the formation of thermal conductivity pathways within the composites, thereby enhancing the thermal conductivity of C/SiOC composites. Furthermore, in situ formed nanostructures‐containing C/SiOC composites developed a carbon friction layer comprising CNTs and turbostratic carbon, which significantly enhanced the abrasion resistance, endowing C/SiOC composites stable friction coefficients, and lower levels of wear.

Analysis of the turbostratic structures in PAN-based carbon fibers with wide-angle x-ray diffraction

Carbon fiber (CF) is a versatile material renowned for its excellent mechanical, thermal, and electrical properties. Polyacrylonitrile (PAN)-based CFs dominate the market in part due to their high tensile strength, rendering them suitable for structural applications in a wide variety of applications ranging from sporting goods to aerospace. Over five decades of commercial development of PAN-based CF has resulted in a range of varieties with different tensile moduli and tensile strengths. The microstructures, nanostructures, and crystal structures of PAN-based CF all play pivotal roles in the macroscale properties of this material. In particular, the crystal structure and crystallite orientation in CF is closely related to the mechanical properties. The crystal structure of PAN-based CF generally consists of turbostratic carbon, a disordered form of graphite, the characteristics of which can be effectively characterized in a bulk format through wide-angle x-ray diffraction (WAXD). In this work, we employed a three-part approach to the analysis of WAXD patterns collected from four intermediate modulus PAN-based CFs. The approach incorporates a Scherrer analysis, a Debye analysis, and an orientational analysis to provide precise estimates of crystallite sizes, crystallite distributions, and crystallite orientations with the fiber axis. The results presented here suggest that intermediate modulus PAN-based CF mostly consists of small turbostratic crystallites (<4 nm), with larger crystallites having increased orientation with the fiber axis. The results here imply the presence of curvature and/or wrinkling of the turbostratic layers within the CF structure.

Balancing microcrystalline domains in hard carbon with robust kinetics for a 46.7 Wh kg−1 practical lithium-ion capacitor

As a promising electrochemical energy storage system, lithium-ion capacitors (LICs) exhibit alluring theoretical merits of high energy density, high power density and long cycle life. However, most of the LIC cells can hardly surpass the practical energy density threshold of 30 Wh kg−1, which greatly hinders their employments in various energy-oriented fields. Anthracite shows great prospect as low-cost and abundant carbon precursor to prepare anode material with plentiful Li-ion anchoring sites for high performance LICs. In this work, a scalable low-temperature hydrothermal disordering strategy is proposed to achieve balanced structural modification of anthracite into short-ranged turbostratic carbon precursor, which further transforms into microcrystalline hard carbon (MHC) with high electrical conductivity (13065 S m−1) and substantially improved energy storage kinetics. A practical large-capacity LIC pouch cell is fabricated using MHC anode and activated carbon cathode to deliver a maximum gravimetric and volumetric energy density of 46.7 Wh kg−1 and 66.8 Wh/L based on the total weight of cell, outperforming the commercially available LIC products from relevant enterprises. Moreover, the cell reveals an exceptional capacity retention of 94.7 % after 10,000 cycles at high current density. The work herein would emerge as a universal and feasible protocol to fabricate high-end carbon electrode for practical LICs in numerous energy-intensive occasions.

Synthesis and characterization of aluminum-doped graphitic carbon

AbstractHeteroatom doping of graphitic carbon is of high interest for tuning its physicochemical properties. Aluminum is commonly reported as a high-interest dopant, but few synthetic strategies have been reported owing to the low equilibrium solubility of Al within graphite. Herein we report several strategies to achieve metastable aluminum-substituted turbostratic graphitic carbon materials with aluminum contents up to ~ 0.5 at%, via co-pyrolysis of two molecular precursors between 800 and 1100°C. The resulting materials exhibit turbostratic graphitic structure and a previously unreported aluminum environment detectable by X-ray absorption spectroscopy (XAS), a likely signature of trigonal planar or puckered AlC3-type sites. Graphical abstract

Shellular SiCN ceramics with integrated structure and function realizing full electromagnetic wave absorption in the X-band

In this paper, the electromagnetic wave (EMW) absorption properties of SiCN ceramics with a shellular structure prepared by 3D printing technology (DLP) at different pyrolysis temperatures were investigated. The research shows that polarization loss and multiple reflections are the principal reasons for the improvement in sample absorption performance. The shellular structure is favorable for the multiple reflections and scattering of electromagnetic wave inside the material. The turbostratic carbon, graphitic carbon and SiC generated by pyrolysis are conducive to improving the dielectric loss of the sample, adjusting its impedance matching performance and improving its absorption performance. The RLmin of SiCN-1200 reaches − 21.12 dB (3.22 mm), and the effective band width is 4.20 GHz, covering the whole X-band. The excellent EMW absorption performance of DLP-SiCN ceramics, together with additive manufacturing, enable the integration of material, structure and function within a single component.

The effect of thermal modification of turbostratic carbon on its fractal structure

Fractal structure of porous carbon materials (PCMs) obtained by thermal modification under different regimes was investigated using the method of low-temperature porometry. It was established that at modification temperatures of 300 and 600°C, materials with a developed microporous structure are formed, the surface fractal dimension of which is 2.6. At modification temperatures of 400 and 500°C, the value of the fractal dimension of the surface decreases to a value of 2.22, which indicates the formation of an almost smooth surface due to the intensive removal of carbon atoms from the near-surface layers of the material particles, a decrease in the number of micropores with their transition into mesopores, unification of small carbon clusters into larger ones and the formation of microparticles of non-porous carbon material.

Graphene nanowalls formation investigated by Electron Energy Loss Spectroscopy

The properties of layered materials are significantly dependent on their lattice orientations. Thus, the growth of graphene nanowalls (GNWs) on Cu through PECVD has been increasingly studied, yet the underlying mechanisms remain unclear. In this study, we examined the GNWs/Cu interface and investigated the evolution of their microstructure using advanced Scanning transmission electron microscopy and Electron Energy Loss Spectroscopy (STEM-EELS). GNWs interface and initial root layers of comprise graphitic carbon with horizontal basal graphene (BG) planes that conform well to the catalyst surface. In the vertical section, the walls show a mix of graphitic and turbostratic carbon, while the latter becomes more noticeable close to the top edges of the GMWs film. Importantly, we identified growth process began with catalysis at Cu interface forming BG, followed by defect induction and bending at ‘coalescence points’ of neighboring BG, which act as nucleation sites for vertical growth. We reported that although classical thermal CVD mechanism initially dominates, growth of graphene later deviates a few nanometers from the interface to form GNWs. Nascent walls are no longer subjected to the catalytic action of Cu, and their development is dominated by the stitching of charged carbon species originating in the plasma with basal plane edges.

Turbostratic Carbon Nano Onion Electrode for High Power Density Vanadium Redox Flow Battery

The redox flow battery (RFB) is one of the most promising technologies for stationary energy storage. It consists of a voltaic cell whose electrolytes are stored in tanks outside the system. Whilst the chemistries of the anodic and cathodic electrolytes define the energy density of a RFB system, its power density is determined primarily by its electrodes. These are typically porous carbon media on the surface of which the redox reactions occur. They are a critical component since they require a detailed engineering of electrocatalytically active surface area and mass transport. Still today, they remain the main cause of RFB low power density. In this work, we are showing a novel deposition method to improve the performance of commercially available carbon paper already used in RFB.The gain is thanks to the deposition of turbostratic carbon nano-onion (TCNO) nanoparticles on the carbon fibers of the paper. This process is performed with a proprietary technology called NanoJeD: a CVD in supersonic flow, which promises easy industrial scalability and a fine tunability of the nanoparticle properties. Moreover, with this system is possible to deposit over any substrate.NanoJeD consists in two chambers separated by a high aspect ratio slit. A precursor gas is injected through a porous plug from the top and a vacuum system is connected from the bottom. The slit allows the establishment of a high-pressure ratio between the two chambers and hence the formation of a supersonic jet. The precursor gas, a mixture of Argon (98.4%) and Acetylene (1.6%) flows between two electrodes where a radio frequency (RF) signal is fed (13.56 MHz). The RF ignites a non-thermal plasma in which the precursor molecules are ionized and dissociated into radicals, which polymerize forming hydrogenated carbon clusters and nanoparticles (NPs) of different sizes. Once formed, NPs are dragged through the slit by the gas stream and finally impact on the substrate. Therefore, it is possible to achieve a high throughput (500 mg h-1) and to deposit on a large area of 100 cm2 while precisely controlling the properties of the film. The resulting film has hundreds of squared meters per gram of surface area. For TCNO formation, the NP film is further annealed in vacuum at 1000°C for 2 hours. Using in situ transmission electron microscopy (TEM) and energy electron loss spectroscopy (EELS), we were able to visualize the progression of graphitization and changes in structural properties during annealing. The graphitization process starts in the outer layer and proceeds into the interior of the particle. The geometrical constrains of the NP (average diameter of 20nm) and shrinkage of the NP, allow the formation of curved, turbostratic, defective graphitic sheets. UV photoelectron spectroscopy (UPS) and Raman spectroscopy performed ex-situ allow the analysis of valence bands and structural defects. The high presence of defects and general disorder structure are accompanied with a remarkable increase in catalytic activity. Moreover, the annealing process leads to the sintering of the nanoparticles and the formation of an interface between the carbon fibre and the nanoparticles, as demonstrated by the increased thermal stability tested by. Both phenomena improve the adhesion between nanoparticles and with the surface, making the electrode suitable to be adopted in fluxed systems.The TCNO deposited on a carbon paper was tested as electrode in a Vanadium RFB. The kinetic activity and electrochemical properties were tested via in-situ Raman and in a three-electrode cell set-up. The results reveal an increased kinetic activity with respect to the untreated paper. Using in situ Raman we were able to show differences in redox mechanism between TCNO and bare carbon paper. A chronoamperometry test was used to obtain the transfer coefficient from a Tafel plot. These studies allow the correlation of the catalytic activity with the defectiveness of the TCNO nanoparticle. Vanadium RFB full cell measurements of the TCNO electrode show a drastic increase in performance, reaching an energy efficiency of 70.8% and 86.2% at current densities of 600 mA cm-2 and 200 mA cm-2, respectively. The electrolyte utilisation for these current densities is 59% for the former and 80% for the latter. To investigate the chemical and mechanical stability a stability test was performed. Results showed a low degradation rate of 0.004% EE per cycle. Moreover, TCNO can be used for other electrochemical applications only by adjusting the deposition and annealing parameters.

Graphene nanowalls grown on copper mesh

Graphene nanowalls (GNWs) can be described as extended nanosheets of graphitic carbon where the basal planes are perpendicular to a substrate. Generally, existing techniques to grow films of GNWs are based on plasma-enhanced chemical vapor deposition (PECVD) and the use of diverse substrate materials (Cu, Ni, C, etc) shaped as foils or filaments. Usually, patterned films rely on substrates priorly modified by costly cleanroom procedures. Hence, we report here the characterization, transfer and application of wafer-scale patterned GNWs films that were grown on Cu meshes using low-power direct-current PECVD. Reaching wall heights of ∼300 nm, mats of vertically-aligned carbon nanosheets covered square centimeter wire meshes substrates, replicating well the thread dimensions and the tens of micrometer-wide openings of the meshes. Contrastingly, the same growth conditions applied to Cu foils resulted in limited carbon deposition, mostly confined to the substrate edges. Based on the wet transfer procedure turbostratic and graphitic carbon domains co-exist in the GNWs microstructure. Interestingly, these nanoscaled patterned films were quite hydrophobic, being able to reverse the wetting behavior of SiO2 surfaces. Finally, we show that the GNWs can also be used as the active material for C-on-Cu anodes of Li-ion battery systems.

High temperature oxidation of additively manufactured silicon carbide/carbon fiber nanocomposites

An additive manufacturing process and subsequent pyrolysis cycle were used to fabricate SiC matrix/carbon fiber hybrid composites. The matrix was fabricated using a mixture of preceramic polymer and acrylate monomers, while polyacrylonitrile (PAN) precursor was used to fabricate fibers via electrospinning. The precursor matrix and reinforcing fibers at 0, 2, 5, or 10 wt% were printed using digital light processing, and both were simultaneously pyrolyzed to yield the final ceramic matrix composite structure. After pyrolysis, XRD and SEAD analysis proved the existence of SiC nanocrystals and turbostratic carbon structure in the matrix, while the reinforcement phase was shown to have a turbostratic carbon structure similar to commercial carbon fibers. Thermogravimetric analysis (TGA) in air up to 1400 °C was used to evaluate the oxidation resistance of this material. TGA results showed some weight loss due to oxidation of SiC and/or carbon up to about 900 °C, followed by weight gain to about 1200 °C due to the formation of a protective SiO2 layer. Although increasing carbon fiber content negatively impacted the total mass loss for the first heating cycle, exposure of the composite to second-run air revealed negligible weight loss. This is explained by SiO2 layer formation which acts as a protective film that prevents oxygen diffusion. Oxidation of SiC and the formation of a glassy layer has been proven to protect the sample from further oxidation, as well as provide healing of surface cracks and defects as revealed by SEM analysis.

Nitrogen and sulfur functionalized microporous carbon nanomaterial derived from waste coconut husk for the efficient detection and removal of ofloxacin

This study uses waste coconut husk to synthesize carbon quantum dots decorated graphene-like structure for sustainable detection and removal of ofloxacin. The XRD spectrum shows the carbon nanomaterial's layered structure with turbostratic carbon stacking on its surface. The FESEM and HRTEM studies claim the successful development of quantum dots decorated 2D layered structure of carbon nanomaterial. The functionalization of sulfur and nitrogen is well observed and studied through XPS, while Raman spectra have provided insight into the surface topology of the as-synthesized nanostructure. The BET surface area was found to be 1437.12 m2/g with a microporous structure (pore width 2.0 nm) which interestingly outcompete many reported carbon-based nanomaterials such as graphene oxide, reduced graphene oxide and quantum dots. The detection and removal processes are monitored through UV–visible spectroscopy and the obtained detection limit and adsorption capacity were 2.7 nM and 393.94 mg/L respectively. Additionally, 1 mg carbon nanomaterial has removed 49 % ofloxacin from water in just 1 h. In this way, this study has successfully managed the coconut husk waste after its utilization for environmental remediation purposes.

Effect of annealing temperature on the microstructure, dielectric, and microwave absorption performance of precursor blends derived ZrSiOCN ceramics

The ZrOC ceramic derived from polyzirconoxane (PZC) precursor, usually composed of ZrO2 and ZrC, is a high temperature ceramic material possessing great potentialities to be applied in harsh environments. However, the relatively high electrical conductivity of ZrC usually results in the limited electromagnetic wave absorption performance, and it's an effective way to adjust the relative complex permittivity of ZrOC ceramics by introducing SiCN ceramics with low dielectric properties. In this work, polyzirconoxane (PZC) and polysilazane (PSN) precursors were blended at the weight ratio of 1:1 firstly, then the blends were cured and pyrolyzed to prepare the ceramics composed of Zr compounds and Si-containing amorphous ceramics. As the annealing temperature rises, t-ZrO2, turbostratic carbon, and ZrC0.347N0.653 grains appear, and the real and imaginary parts of the permittivity gradually increase. It can be found that ZrC0.347N0.653 and free carbon form a typical core-shell structure when the annealing temperature is 1500 °C, and the as-obtained ceramic possesses remarkable microwave absorption ability. The minimum reflection loss is −22.7 dB at 12.02 GHz, and the value of effective absorption bandwidth is 1.65 GHz with a sample thickness of 2.0 mm.

Microporous carbon prepared by microwave pyrolysis of scrap tyres and the effect of K+ in its structure on xylene adsorption

This work brings novel information about microwave-assisted pyrolysis of scrap tyres, the industrial realization of which is still an engineering challenge due to both missing fundamental processing issues as well as how to enhance the engineering quality of pyrolytic products, mainly of solid carbon black. One-step microwave pyrolysis of scrap tyres for 50 min at power of 440 W with KOH activation in the mass ratio of 1:3 (scrap tyres:KOH) is successfully applied for the first time to yield micropores-containing carbon black which application potential was verified for xylene adsorption from waste gas. Compared to conventional high-temperature pyrolysis, the microwave pyrolysis requires shorter time and thus significantly reduces input energy. Two-step microwave pyrolysis of scrap tyres at 440 W does not result in more organized graphene-based carbon, but turbostratic carbon is more perturbed. The higher microwave power of 950 W within one-step microwave pyrolysis does not enhance the graphitization of carbon black, but shorten the microwave pyrolysis time to 20 min. The two main physicochemical properties of the novel micro-macroporous carbon black determining its adsorption performance for xylene are the microporosity/large volume of micropores and K+ present in the carbon structure. Micropores <0.52 nm with/without K+ and cavities <0.82 nm with K+ within carbon structure are proved by molecular modeling to be the sites with the highest affinity for xylene adsorption. Higher adsorption capacity of activated carbon blacks compared to non-activated ones correlates with molecular modeling results. More perturbed carbon structure does not affect the xylene adsorption.

Insights of the Ultralow Wear and Low Friction of Carbon Fiber Reinforced PTFE in Inert Trace Moisture Environment

Ultralow wear rates and low friction have been observed for carbon fiber reinforced PTFE (CF/PTFE) when sliding against steel or cast iron in dry gas environments. Although the strong environmental sensitivity of this tribosystem is well known, the origin of the outstanding tribological performance in dry gas remains unanswered. Some researchers attribute the low friction and wear to the formation of carbon-rich surfaces in the absence of oxygen and moisture in the environment. However, low friction between carbon surfaces is generally dependent on moisture. In this paper, extensive analyzes are conducted on the tribofilms formed on the CF/PTFE surface and the steel counterface after sliding in a high-purity nitrogen environment. TEM analysis of a cross-section of the tribofilm on the steel surface reveals that the sliding surface consists mainly of iron (II) fluoride and not carbon, even though a significant amount of carbon was observed near the surface. XPS and TEM analysis further revealed that the tribofilm formed on the worn composite surface consisted of nanoparticle agglomerates, anchored to the PTFE matrix and to each other by carbon with turbostratic structure. Turbostratic carbon also formed an ultrathin and surface-oriented superficial layer on top of the agglomerates. Governing mechanisms of the low friction and wear of the CF/PTFE—steel tribosystem were investigated by complementary tribotests with pure graphite samples and MD simulations of the identified surfaces. These indicated that the low friction between the carbon and iron fluoride in the tribofilms is due to poor adhesion between the distinctly different surfaces.Graphical

Deposition of graphenic nanomaterials from elevated temperature premixed stagnation flames

The work examines the unique nanostructure of carbon nanoparticles deposited from sooting premixed flames with flame temperatures exceeding 2200 K. This flame temperature regime has previously been shown to transition from typical soot formation conditions to a regime whereby the flame-form carbon adopts a nanostructure considerably more ordered than soot. Graphenic carbon deposits observed by High-resolution TEM (HRTEM) are reported here corroborating previous Raman spectroscopy evidence. The use of premixed stretch-stabilized flames enables particle production in the high-temperature regime under a flow field amenable to low-dimensional flame modeling. Although the flame flow configuration is relatively simple, three sample preparation methods are used to assess the representation of true carbon properties as they exist in the flame. HRTEM imaging is carried out on carbon particle samples prepared by rapid-insertion deposition, aerosol dilution probe deposition and carbon particle film deposition. Images from rapid-insertion samples show amorphous particles in the lightly sooting flame and turbostratic particles in the heavy sooting flame. There is trace evidence of graphenic structure in rapid-insertion samples but the most striking particles on the TEM grid are graphite nanocrystals presumably formed by a new artificial crystallization process. HRTEM images of particles collected over time by diluted aerosol deposition and film deposition show clear graphenic structures. Overall, the carbon nanostructure observed by HRTEM is a mixture of amorphous, turbostratic and graphenic carbon lattices depending on the flame condition and sampling method. The current work highlights potential impacts of higher flame temperatures and higher equivalence ratio on deposited flame-formed carbon. Namely, graphenic particle structure is observed in rapid-insertion deposition samples but graphene portions are most abundant in aerosol dilution and carbon particle film deposition samples. This may indicate that graphene structures grow on the deposition surface over time.