高煤级煤石墨化轨迹阶段性的XRD和Raman光谱表征

为了研究石墨化过程中煤的分子结构有序化轨迹,选取湖南、陕西19个不同变形-变质程度高煤级煤为研究对象,采用工业分析、元素分析、X射线衍射分析(XRD)和拉曼光谱分析(Raman)等手段,结合分峰拟合的数学方法,对系列样品分子结构参数(XRD结构参数,如石墨化度、延展度La、堆砌度Lc及面网间距d002等;Raman参数...

XRD and Raman Spectroscopy Characterization of Graphitization Trajectories of High-Rank Coal

In order to the interpretation of ordering and crystallinity of natural graphitized coal, nineteen kinds of different deformation-metamorphism degree high-rank coal from Hunan Province and Shaanxi Province were studied with proximate and ultimate analysis, X-ray diffraction (XRD), Raman spectrum and curve-fitting analysis. The graphitization, crystal size (L_a and L_c), interplanar spacing (d₀₀₂) were calculated with XRD. The parameters of P_G (G band position), P₁ (G and D1 band separation), R₁=I_D1/I_G, the peak height ratio, R₂=A_D1/(A_G+A_D1), peak area ratio were calculated with Raman. The results showed that the H/C decreases gradually with the increase of metamorphic degree during the coalification stage, but during the graphitization stage, the change was primarily physical, and the trend was slow or not significant. The parameters of d₀₀₂, L_a, L_c, N and L_a/L_c had shown that the crystalline structure of natural graphitized coal presented nonlinear continuous (step) change with metamorphism degree. The inflection point corresponds roughly to R_m=7.0% and d₀₀₂=0.338 nm. Before the inflection point, L_a, L_c and N changed little (or increase steadily), and the graphite crystal structure formed rapidly after the inflection point, the stacking effect begins and gradually increases, as the crystallite size increases. L_a/L_c variation reflected that the graphitization process changed from condensation to overlap. The graphitization trajectory of high-rank coal can be given in a three-stage model of orderly increase. During the stage from amorphous carbon (anthracite) to meta-anthracite, the parameters of P_G and P₁ changed significantly, and I_D1/I_G did not obey the TK relation when expressing the degree of disorder. During the stage from meta-anthracite to semi-graphitization showed different directions, R₁ presented an opposite trajectory with the increase of order, the evolution of some graphite components followed the TK relation, and R₂ showed a completely contradictory trajectory when the graphitization degree was 45%. The temperature and pressure in the graphite stage led to a sharp increase in crystal size (step evolution), and the decrease of I_D1/I_G obeying the TK relation. As neogenesis-associated components in different graphitized coals, d₀₀₂ cannot reflect the largest metamorphic degree of graphitized coal. However, it was still a superior choice to consider d₀₀₂ as an average scaling of the graphitized coals in the process of graphitization. Moreover, full width at half maximum of the (002) and (γ) band are reliable indicators for distinguishing and classifying of metamorphism type of nature graphitized coals. H/C, and I_D1/I_G also evolved over d₀₀₂ trajectory was altered, needed to use d₀₀₂＜0.344 nm, R₁＜2.0, H/C＜0.12 and other comprehensive indicators to identify the beginning of graphitization. From this, it could be seen that XRD and Raman spectral analysis techniques could be used to characterize the graphitization track stages and structural differences of high rank coal.