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  1. Free, publicly-accessible full text available July 10, 2024
  2. Abstract

    Responsible disposal of vehicles at the end of life is a pressing environmental concern. In particular, waste plastic forms the largest proportion of non-recycled waste material from light-duty vehicles, and often ends up in a landfill. Here we report the upcycling of depolluted, dismantled and shredded end-of-life waste plastic into flash graphene using flash Joule heating. The synthetic process requires no separation or sorting of plastics and uses no solvents or water. We demonstrate the practical value of the graphene as a re-inforcing agent in automotive polyurethane foam composite, where its introduction leads to improved tensile strength and low frequency noise absorption properties. We demonstrate process continuity by upcycling the resulting foam composite back into equal-quality flash graphene. A prospective cradle-to-gate life cycle assessment suggests that our method may afford lower cumulative energy demand and water use, and a decrease in global warming potential compared to traditional graphene synthesis methods.

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  3. Abstract

    In the past 17 years, the larger‐scale production of graphene and graphene family materials has proven difficult and costly, thus slowing wider‐scale commercial applications. The quality of the graphene that is prepared on larger scales has often been poor, demonstrating a need for improved quality controls. Here, current industrial graphene synthetic and analytical methods, as well as recent academic advancements in larger‐scale or sustainable synthesis of graphene, defined here as weights more than 200 mg or films larger than 200 cm2, are compiled and reviewed. There is a specific emphasis on recent research in the use of flash Joule heating as a rapid, efficient, and scalable method to produce graphene and other 2D nanomaterials. Reactor design, synthetic strategies, safety considerations, feedstock selection, Raman spectroscopy, and future outlooks for flash Joule heating syntheses are presented. To conclude, the remaining challenges and opportunities in the larger‐scale synthesis of graphene and a perspective on the broader use of flash Joule heating for larger‐scale 2D materials synthesis are discussed.

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  4. Abstract

    Hydrogen sulfide (H2S) is a noxious, potentially poisonous, but necessary gas produced from sulfur metabolism in humans. In Down Syndrome (DS), the production of H2S is elevated and associated with degraded mitochondrial function. Therefore, removing H2S from the body as a stable oxide could be an approach to reducing the deleterious effects of H2S in DS. In this report we describe the catalytic oxidation of hydrogen sulfide (H2S) to polysulfides (HS2+n) and thiosulfate (S2O32−) by poly(ethylene glycol) hydrophilic carbon clusters (PEG‐HCCs) and poly(ethylene glycol) oxidized activated charcoal (PEG‐OACs), examples of oxidized carbon nanozymes (OCNs). We show that OCNs oxidize H2S to polysulfides and S2O32−in a dose‐dependent manner. The reaction is dependent on O2and the presence of quinone groups on the OCNs. In DS donor lymphocytes we found that OCNs increased polysulfide production, proliferation, and afforded protection against additional toxic levels of H2S compared to untreated DS lymphocytes. Finally, in Dp16 and Ts65DN murine models of DS, we found that OCNs restored osteoclast differentiation. This new action suggests potential facile translation into the clinic for conditions involving excess H2S exemplified by DS.

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  5. Abstract

    Advances in nanoscience have enabled the synthesis of nanomaterials, such as graphene, from low‐value or waste materials through flash Joule heating. Though this capability is promising, the complex and entangled variables that govern nanocrystal formation in the Joule heating process remain poorly understood. In this work, machine learning (ML) models are constructed to explore the factors that drive the transformation of amorphous carbon into graphene nanocrystals during flash Joule heating. An XGBoost regression model of crystallinity achieves anr2score of 0.8051 ± 0.054. Feature importance assays and decision trees extracted from these models reveal key considerations in the selection of starting materials and the role of stochastic current fluctuations in flash Joule heating synthesis. Furthermore, partial dependence analyses demonstrate the importance of charge and current density as predictors of crystallinity, implying a progression from reaction‐limited to diffusion‐limited kinetics as flash Joule heating parameters change. Finally, a practical application of the ML models is shown by using Bayesian meta‐learning algorithms to automatically improve bulk crystallinity over many Joule heating reactions. These results illustrate the power of ML as a tool to analyze complex nanomanufacturing processes and enable the synthesis of 2D crystals with desirable properties by flash Joule heating.

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  6. Abstract

    Graphene has proved to be an exceptional reinforcing additive for composites, but the high cost of its synthesis has largely prevented its addition on industrial scales. Flash Joule heating provides a rapid, bulk‐scale method for graphene synthesis from coal materials, such as metallurgical coke (MC), into metallurgical coke‐derived flash graphene (MCFG). Here, this work investigates the properties of graphene‐epoxy composites in a higher nanofiller content regime than has previously been reported in literature. Composites with 20 to 50 wt% loading of MCFG are prepared by combining MCFG with diglycidyl ether bisphenol A epoxy precursor (DGEBA) and 1,5‐diamino‐2‐methylpentane. With a 1:2 ratio of MCFG:DGEBA, the Young's modulus increases by 92% and with a 1:3 ratio, hardness increases by 140%. At a 1:4 ratio of MCFG:DGEBA, compressive strength and maximum strain increase by 145% and 61%, respectively. At a 1:3 ratio of MCFG:DGEBA, toughness increases by 496%. Finally, at a 1:1 ratio of MCFG:DGEBA, GHG emissions, water consumption, and energy consumption are reduced by 33%, 47%, and 34%, respectively. As the cost of FG plummets, since it can be produced from very low cost materials like MC, in milliseconds with no solvent or water, the prospects are promising for its high‐loading use in composites.

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