Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals

Yihuai Zhang*, Maxim Lebedev, Gregory Smith, Yu Jing, Andreas Busch, Stefan Iglauer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)
88 Downloads (Pure)


Characterization of coal micro-structure and the associated rock mechanical properties are of key importance for coal seam exploration, coal bed methane development, enhanced coal bed methane production and CO2 storage in deep coal seams. Considerable knowledge exists about coal chemical properties, but less is known about the nanoscale to the micro-scale structure of coals and how they change with coal strength across coal ranks. Thus, in this study, 3D X-ray micro-computed tomography (with a voxel size of 3.43 µm) and nano-indentation tests were conducted on coal samples of different ranks from peat to anthracite. The micro-structure of peats showed a well-developed pore system with meso- and micro-pores. The meso-pores essentially disappear with increasing rank, whereas the micro-pores persist and then increase past the bituminous rank. The micro-fracture system develops past the peat stage and by sub-bituminous ranks and changes into larger and mature fracture systems at higher ranks. The nano-indentation modulus showed the increasing trend from low- to high-rank coal with a perfect linear relationship with vitrinite reflectance and is highly correlated with carbon content as expected.

Original languageEnglish
Pages (from-to)1787–1800
Number of pages14
JournalNatural Resources Research
Early online date18 Oct 2019
Publication statusPublished - Jun 2020


  • Coal rank
  • ECBM
  • Micro-CT
  • Micro-structure
  • Nano-indentation test

ASJC Scopus subject areas

  • General Environmental Science


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