热变煤所处地质条件明显异于正常变质作用煤,由于受到直接接触的岩浆侵入体影响,热 变煤一方面经受了快速升温缓慢冷却的受热过程,另一方面也受到侵入体接触挤压带来的额外应 力作用,这使得热变煤的碳纳米结构变化明显异于正常变质作用煤。 为揭示热变煤中碳纳米结构 的特殊性,基于 X 射线衍射(XRD)与高分辨率透射电镜(HRTEM)分析手段,研究热变煤的微晶结 构参数演化,同时对热变煤中碳纳米结构类型及其成因进行系统分析。 结果表明:与深成变质作用 煤相比,热变煤的微晶层间距更接近石墨微晶。 在镜质体反射率小于 10%时,热变煤的层间距 和 La / Lc 均呈现三阶段变化。 在热变煤中,识别出 4 种碳纳米结构,即无序芳香簇结构、芳香同心环 状结构、涡层结构和类石墨状结构。 其中,类石墨状结构主要出现在颗粒边缘、显微组分相互挤压 面上以及孔隙裂隙边缘处,其成因与颗粒内部应力有关。 相比于其他 3 种碳纳米结构,类石墨状结 构的定向性更好,同时其芳香层片的长度也更长。 与正常变质煤受热形成的类石墨结构不同,热变 煤颗粒边缘类石墨结构的层间距更小而延展度更大。 基于此,通过改进的 Hummers 法可从热变煤 中制备得到石墨烯,但缺陷特征明显,因此亟需进一步深入研究。

The geological conditions of thermally altered coal are obviously different from those of normal metamorphic coal. Due to the influence of direct contacted intrusion, the thermally altered coal has undergone a process with rapid heating and slow cooling, on the other hand, it is also affected by additional stress caused by the contact extrusion of the intrusion, which also makes the thermally altered coal significantly different from the normal metamorphic coal in terms of carbon nanostructure changes. In order to reveal the particularity of car- bon nanostructures in the thermally altered coals, the carbon nanostructures in the thermally altered coals were system- atically analyzed based on the previous studies by our research group and other researchers. The evolution of micro- crystalline structure parameters for the thermally altered coal was studied, and the types and its genesis of car- bon nanostructures in the thermally altered coal were analyzed with the XRD and HRTEM methods. The results show that compared with the metamorphic coal, the interlayer spacing of the thermally altered coal is closer to that of the graphite crystallites. When the vitrinite reflectance is less than 10%, the interlayer spacing and La / Lc of the thermally altered coal show three-stage changes. In addition, four carbon nanostructures were identified in the thermally altered coal, including disordered aromatic cluster structure, aromatic concentric ring structure, turbos- tratic carbon structure, and graphitic-like structure. Among them, the graphitic-like structures in the thermally altered coal mainly appear at the edges of particles, on the extruded surfaces of micro-components, and at the edges of pores and fissures, which is related to the internal stress of the particles. Compared with the other three carbon nano- structures, the graphite-like structures have better orientation and longer lattice fringe length. Different from the graph- ite-like structure formed by the heating of normal metamorphic coal, the graphite-like structure at the edge of thermally altered coal particles has smaller interlayer spacing and greater La. Based on this, graphene can be prepared from the thermally altered coal by the improved Hummers method with obviously defects, so a further in-depth and de- tailed research is urgently needed.