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煤炭微观结构特征对其力学性能、破碎倾向和微尘形成的影响

2024-11-20

原文链接:

https://link.springer.com/article/10.1007/s40789-023-00578-5或点击文末“阅读原文



摘 要

本文揭示了无烟煤、变质无烟煤和石墨等不同等级煤炭的结构特征,这些特征决定了它们的破碎倾向和形成微尘的能力。为此,综合使用各种纳米压痕技术和拉曼光谱方法,通过增加峰值载荷和准静态载荷进行循环纳米压痕,研究了所选煤炭的力学性能。通过分析弹性模量和损伤指数,得到煤样力学性能的变化。在循环纳米压痕过程中,确定了三组煤样的破碎倾向。第一组和第二组的特点是在与压头的接触区域出现局部破坏,并形成破碎材料的核心。第三组的特点是整体破坏(在与压头接触区域之外)。一般来说,在变质岩中,由于矾土物质的微观压实,煤炭在力学载荷作用下的断裂能力会降低。在无烟煤、变质无烟煤和石墨中,可以确定无烟煤和变质无烟煤发生了物理压实,而石墨由于其结构的突然变化而表现出相当不同的行为。通过对煤的拉曼光谱进行解卷积,确定了碳的非晶相和晶体相之间的比例S。煤炭的破碎倾向随着S的增加而增加。对于所研究的煤种和变质无烟煤,可以确定的是,在与压头的接触区域外的破坏倾向取决于S是否达到1或更高。当S小于1时,煤炭仅在与压头接触的区域被压碎。



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Abstract The work is dedicated to revealing the structural features of coals with different ranks, such as anthracites, metaanthracite and graphite, that determine their ability to crush and form fine dust. For this purpose, a combination of various nanoindentation techniques and Raman spectroscopy was used. The mechanical behavior of the selected coals was investigated by cyclic nanoindentation with increasing peak load and quasi-static loading. The alteration of the mechanical properties was studied by analysis of elastic moduli and damage indices Rw. Three groups of coals were identified based on their propensity to crushing during cyclic nanoindentation. Coals assigned to the first and second groups are characterized by local destruction in the contact zone with the indenter and the formation of a core of crushed material. Coals assigned to the third group are characterized by bulk destruction (outside the zone of contact with the indenter). In general, the ability of coals to fracture under mechanical loading decreases in the series of metamorphism due to microscale compaction of vitrinite matter. In the series of anthracite, metaanthracite and graphite, it is established that the coal matter compaction takes place for the anthracite and metaanthracite, whereas graphite reveals rather different behavior due to abrupt change of its structure. The ratios between the amorphous and crystalline phases of carbon (S) were determined by deconvolution of coals Raman spectra. The propensity of coals to crushing (a damage index Rw) increases with growth of the proportion of amorphous carbon in the coal matter. For the considered coals and metaanthracite, it is established that the proneness to destruction outside the contact zone with the indenter is determined by the ratio of amorphous and crystalline carbon of 1 and higher. When S parameter is lower than 1, the coals are being crushed only in the zone of contact with the indenter.


文章部分图片

Fig. 1 a Loading mode for the cyclic nanoindentation b Example of P-h curve for cyclic nanoindentation (coal No. 2)

Fig. 3 Changes in a Elastic moduli and b Damage index for coals at cyclic nanoindentation: a division into groups


Fig. 4 An example of the image of the surface topology of coals a Before and b After cyclic nanoindentation. After mechanical impacts, a pronounced change (imprints, cracks outside the indentation zone, as well as destruction near the imprints are visible; pieces of a detached coal substance are found)



引用格式:

Kossovich, E., Epshtein, S., Krasilova, V. et al. Effects of coals microscale structural features on their mechanical properties, propensity to crushing and fine dust formation. Int J Coal Sci Technol 10, 20 (2023). https://doi.org/10.1007/s40789-023-00578-5

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