Abstract This study aims at understanding the structural changes occurring in the carbonaceous matrix of wood-based chars during their thermal conversion. Although chars are routinely characterized by porosity measurements or scanning electron microscopy, the composition and structure of the carbonaceous matrix is often not investigated. Here, advanced characterization using X-ray synchrotron microtomography, transmission electron microscopy, Raman spectroscopy and X-ray diffraction provided a precise description of the char properties, allowing for an accurate discussion of their catalytic properties. Two chars were produced by slow pyrolysis of wood waste (400 and 700 °C) and a third one was fabricated by activation under steam at 850 °C of the char obtained at 700 °C. The results show that the pyrolysis temperature and the activation performed did not affect the macrostructure of the chars and that the pores were interconnected at the macroscopic scale. However, at 700 °C, the micro- and nanostructures were modified: short-range organized graphene fringes were observed. The activated char showed a homogeneous microstructure similar to that of its precursor. Besides, the ratio of graphene-like structures, the local organization of graphene sheets, and the imperfections in graphene-like sheets were clearly improved by the post-treatment. To our knowledge, this is the first time that such an approach, combining various tools, is applied for the study of pyrolysis chars.

中文翻译：

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高级表征揭示了木基炭的结构和反应性

摘要 本研究旨在了解木炭在热转化过程中碳质基质发生的结构变化。尽管炭通常通过孔隙度测量或扫描电子显微镜进行表征，但通常不研究碳质基质的组成和结构。在这里，使用 X 射线同步加速器显微断层扫描、透射电子显微镜、拉曼光谱和 X 射线衍射的高级表征提供了对炭特性的精确描述，允许对其催化特性进行准确讨论。两种炭是通过木材废料（400 和 700 °C）的缓慢热解产生的，第三种是通过在 850 °C 下将在 700 °C 下获得的炭在蒸汽下活化来制造的。结果表明，热解温度和所进行的活化不影响炭的宏观结构，并且孔隙在宏观尺度上是相互连接的。然而，在 700 °C 时，微米和纳米结构被修改：观察到短程有组织的石墨烯条纹。活性炭显示出与其前体相似的均匀微观结构。此外，石墨烯类结构的比例、石墨烯片的局部组织以及类石墨烯片中的缺陷都通过后处理得到了明显改善。据我们所知，这是第一次将这种结合各种工具的方法应用于热解炭的研究。微米和纳米结构被修改：观察到短程有组织的石墨烯条纹。活性炭显示出与其前体相似的均匀微观结构。此外，石墨烯类结构的比例、石墨烯片的局部组织以及类石墨烯片中的缺陷都通过后处理得到了明显改善。据我们所知，这是第一次将这种结合各种工具的方法应用于热解炭的研究。微米和纳米结构被修改：观察到短程有组织的石墨烯条纹。活性炭显示出与其前体相似的均匀微观结构。此外，石墨烯类结构的比例、石墨烯片的局部组织以及类石墨烯片中的缺陷都通过后处理得到了明显改善。据我们所知，这是第一次将这种结合各种工具的方法应用于热解炭的研究。