Abstract Small angle X-ray scattering (SAXS) has been widely employed to characterize the pore structure of coal and other geomaterials. However, in the many previous experimental investigations by SAXS, the probed samples were not standardized in terms of shape and particle size, even for the same geomaterial. The influence of pulverization on the pore structure of coal is generally ignored by the researchers using SAXS for structure characterization. In this study, SAXS is used to investigate the effect of pulverizing on pore modification of virgin coal. Two kinds of coal with different ranks were selected and pulverized for SAXS measurements. Both powder samples (five particle size fractions) obtained by grinding and slice samples were investigated. The results show that the nano-pore structure of coal has been significantly modified due to pulverization. The sample pore volume per unit mass increases with the decrease of sample particle size. Pulverizing the slice sample into the minimum particle sample particle size of 0.075–0.125 mm leads to an increase in the pore volume per unit mass of coal by 39.53% and 18.29% for tested medium volatile bituminous coal and anthracite, respectively. Pulverization can reduce the volume of smaller pores ( 20 nm). After grinding the original sample into the minimum particle size of 0.075–0.125 mm, the fractal dimension of the tested medium volatile bituminous coal and anthracite decreased by 0.266 and 0.179, respectively. Surface fractal dimension of pore decreases with the reduction in coal particle size. In the case of the powder coal sample, the increase in pore volume (especially for pore greater than 20 nm) and the reduction of fractal dimension are beneficial to the diffusion of gas in coal and promoting the desorption of residual gas. This study may provide a quantitative insight into the effect of pulverization on pore structure of coal sample. Moreover, it is of great significance for understanding the mechanism of coalbed methane storage and migration and is helpful for the selection of the sample size in SAXS experiments.

中文翻译：

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使用同步加速器小角 X 射线散射量化煤粉化导致的孔隙改性

摘要 小角 X 射线散射 (SAXS) 已被广泛用于表征煤和其他地质材料的孔隙结构。然而，在 SAXS 之前的许多实验研究中，即使对于相同的地质材料，探测的样品在形状和粒度方面也没有标准化。使用 SAXS 进行结构表征的研究人员通常忽略粉化对煤孔隙结构的影响。在本研究中，SAXS 用于研究粉碎对原始煤孔隙改性的影响。选择两种不同等级的煤粉进行 SAXS 测量。研究了通过研磨和切片样品获得的粉末样品（五种粒度级分）。结果表明，煤的纳米孔结构由于粉化而发生了显着的改变。单位质量的样品孔体积随着样品粒径的减小而增加。将切片样品粉碎成最小颗粒样品粒径为 0.075-0.125 mm，对于测试的中挥发性烟煤和无烟煤，单位质量煤的孔隙体积分别增加了 39.53% 和 18.29%。粉碎可以减少较小孔（20 nm）的体积。将原样研磨至最小粒径0.075～0.125 mm后，被测介质挥发性烟煤和无烟煤的分形维数分别降低了0.266和0.179。孔隙的表面分形维数随着煤粒径的减小而减小。在粉煤样品的情况下，孔隙体积的增加（尤其是大于 20 nm 的孔隙）和分形维数的降低有利于瓦斯在煤中的扩散，促进残余瓦斯的解吸。该研究可以定量了解粉化对煤样孔隙结构的影响。此外，它对于理解煤层气储存和运移的机制具有重要意义，有助于SAXS实验中样本量的选择。