摘要:
煤是一种特殊的有机岩石,其主体组成物质为大分子聚合物。准确刻画并定量表征煤大分子的结构特征,能够为探讨煤结构演化机理提供重要信息。拉曼光谱是近年来迅速发展的一种快速无损的碳材料表征技术,被广泛应用于煤大分子结构的表征研究。通过对国内外有关拉曼光谱技术在煤大分子表征中的研究进展进行系统的调研分析和总结,得到:(1)对于煤的拉曼光谱测试,对样品进行煮胶和抛光打磨、选用不同激光光源和激光能量以及信号收集时间,都会对拉曼光谱产生影响,并且对拉曼光谱进行分峰拟合时要充分考虑样品煤级以及谱峰所蕴含的结构信息。(2)温度对煤中有机质结构演化的影响分为石墨化前拉曼光谱无规律性变化和高温石墨化过程中拉曼无序性参数逐渐降低两阶段特征。常温加压条件下拉曼光谱的特征峰会向高峰位出现线性移动,这与拉曼光谱对应力的响应变化规律一致,并且构造应力产生的结构缺陷会降低煤系石墨的结构有序度。(3)拉曼光谱无序性参数与煤化程度之间并无严格对应关系,综合前人研究成果认为,这可能与煤大分子结构有序性的演化和化学结构的演化并不完全同步以及构造应力通过引入结构缺陷造成结构无序性增加等因素密切相关。(4)拉曼光谱在煤结构表征中的其他应用包括计算芳香层片的大小、特殊峰的指示意义以及二阶拉曼光谱表征煤结构信息等,但在实际使用过程中还需谨慎。
Abstract:
Coals are a special kind of organic rocks, which are mainly composed of macromolecule polymer. Accurate description and quantitative characterization on the structural characteristics of coal macromolecules can provide important information for understanding the evolution mechanism of coal structure. Raman spectroscopy is a fast and non-destruction approach to characterize carbonaceous materials, which has been widely used in the characterization of coal macromolecular structures. The research progress of Raman spectroscopy in the characterization of coal macromolecules both in China and abroad was systematically analyzed and summarized.(1) For the Raman spectrum test of coals, some sample processing methods including the epoxy resin molding and polishing, the selection of different laser light sources, laser energy and signal collection time will affect Raman results. In addition, the coal rank and the structural information contained in the peak of the Raman spectrum should be fully considered in peak fitting.(2) The effect of temperature on the structural evolution of organic in coals can be divided into two stages: the Raman spectrum changes irregularly before graphitization and the Raman disorder parameters gradually decrease during high-temperature graphitization. Under high-pressure and normal temperature, the Raman characteristic peaks linearly shift to higher frequencies, which is consistent with the change of Raman spectrum response to stress, and the structural defects caused by tectonic stress will reduce the structural order degree of coal-based graphite.(3) There is no strict corresponding relation between Raman disorder parameters and coalification, which are suggested to be closely related to many factors, including the asynchronous evolution between coal macromolecular structure and chemical structure, and the effect of stress on structure ordering by inducing structure defects.(4) Other applications include the calculation of aromatic layer size, the indication of special peaks and the use of second-order Raman spectroscopy in the characterization of coal structure. However, these parameters need to be used carefully in practice.
百度学术
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