Natural graphite is a critical raw material and its substitution in some applications will contribute to reduce its supply risk. Coal ash, which is still produced in high amounts, contains a carbonaceous solid residue (char) that may be a substitute of natural graphite. For this purpose, char may be graphitized and used in electrocatalysis reactions, however char properties depend on coal rank, composition and combustion conditions that affect the graphitization process. Research on industrial coal char graphitization is limited, resulting in restricted comprehension of the contributing factors. In order to provide novel insights, industrial residual chars (derived from Poland, Portugal, Romania and South Africa) subjected to high-temperature treatments (carbonization at 1000 °C followed by treatment at 2600 °C under environmental pressure) were examined regarding their microstructural and microtextural transformations. The samples were studied by focussing on its heterogeneity, namely its specific properties and interactions, including elemental composition, optical character, and structure. Furthermore, the evolution of structural order of selected char morphotypes in samples derived from coal of similar rank was assessed using Raman microspectroscopy.

中文翻译：

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石墨化：国际燃煤灰中残炭的微观结构和微观结构转变

天然石墨是一种重要的原材料，其在某些应用中的替代将有助于降低其供应风险。仍然大量产生的煤灰含有碳质固体残渣（焦炭），可以替代天然石墨。为此，可以将炭石墨化并用于电催化反应，但是炭的性质取决于影响石墨化过程的煤等级、成分和燃烧条件。对工业煤焦石墨化的研究有限，导致对其影响因素的认识有限。为了提供新颖的见解，对经过高温处理（1000°C 碳化，然后在环境压力下 2600°C 处理）的工业残留炭（来自波兰、葡萄牙、罗马尼亚和南非）的微观结构进行了检查。和微观结构的转变。研究样品的重点是其异质性，即其特定性质和相互作用，包括元素组成、光学特性和结构。此外，使用拉曼显微光谱法评估了来自相似等级煤炭的样品中选定的炭形态类型的结构顺序的演变。