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Carbon is a fundamental element in nature and is the basis for many materials, including graphite. Among them, graphene, a two-dimensional (2D) material consisting of a single layer of sp2-bonded carbon atoms arranged in a hexagonal lattice, has attracted attention for its unique electrical, mechanical, optical, thermal and sensing properties. These excellent properties have brought graphene to the forefront of research in various technological fields.
Conventional methods for producing graphene, such as mechanical exfoliation, chemical reduction and chemical vapor deposition (CVD), have been widely used. However, these technologies often face challenges in terms of economic viability and environmental sustainability. Mechanical exfoliation methods, while capable of producing high quality graphene, are labor-intensive and limited in yield. Chemical reduction methods involve hazardous chemicals and raise environmental concerns. Chemical vapor deposition, while capable of producing large areas of graphene, requires high temperatures and expensive equipment, limiting its scalability.
The main point of this paper
1. Flash Joule Heating (FJH): As an emerging technology for graphene synthesis, FJH converts carbon-containing materials into graphene through a rapid high-temperature process, which solves the limitations of traditional methods and helps to deal with the global solid waste problem.
2. Characteristics of FJH: The process is simple and easy to operate, but requires a large amount of energy to instantly reach high temperatures.
3. Applications of FJH: Studies have shown that FJH can convert plastic waste, household coal and biomass waste into graphene, with environmental and energy consumption advantages.
4. Scientific Machine Learning Framework: Integration of this framework enhances the understanding of the FJH process and improves graphene yield prediction.
5. Influence of feedstock: The quality and yield of graphene produced by FJH is influenced by the carbon and impurity content of the feedstock, which requires optimization of graphene production from different precursor materials.
6. Aims of the study: To explore the potential of pencil core as a precursor for the synthesis of graphene by FJH, to optimize the FJH process parameters to improve the yield and quality, and to compare the structural and electrochemical properties of graphene samples synthesized under different conditions.
7.Characterization of pencil core: As a composite of graphite and clay, pencil core is an abundant and low-cost carbon source with high electrical conductivity and layered structure, which makes it suitable as a candidate material for graphene production.
Experimental study on the synthesis of graphene by flash joule heating (FJH) process using ordinary pencil core
EXPERIMENTAL DESIGN:
The response of three pencil grades with different graphite to clay ratios, 6H, 4B, and 14B, at different voltages of 0 V, 200 V, and 400 V was investigated.
The samples were characterized using Raman spectroscopy, electrical resistance measurements and microanalysis.
All samples showed a decrease in resistance after FJH treatment, Showing a grade-specific response to the applied voltage.
Revealed structural changes, especially in the ID/IG and I2D/IG ratios, providing insight into defect density and layer stacking.
A significant decrease in the ID/IG ratio and an increase in the crystallite size at 400 V, suggesting that in-situ annealing effects may have occurred.
6H and 4B show higher defect densities at higher voltages.
Contributes to the development of more efficient and environmentally friendly methods of graphene production and opens up new avenues for sustainable and scalable graphene synthesis.
Our study reveals significant structural changes in the pencil core material induced by voltage, and the response of different grades of lead cores to voltage varies. The results show that different grades of lead cores respond differently to the applied voltage, and all samples show a decrease in resistance after FJH treatment. Raman spectroscopy showed significant structural changes, especially in the ID/IG and I2D/IG ratios, providing insight into defect density and layer stacking. In particular, 14B pencils show a unique behavior at 400 V, with a decrease in the ID/IG ratio from 0.135 to 0.031 and an increase in the crystallite size from 143 nm to 612 nm, suggesting a possible in-situ annealing effect. On the other hand, the harder grades (6H and 4B) show a higher defect density at higher voltages. The ultra-high conversion rates and improved structural features observed in 14B pencil leads at 400 V suggest that leads enriched with more graphite may be particularly promising for voltage-based production of high-quality graphene-like materials. These findings open new avenues for the development of simple, cost-effective methods to produce graphene-like materials using existing resources. Further studies are warranted to optimize the voltage application parameters and to explore the potential of other graphite-based materials for similar conversions.
