Characterizing Mechanical Heterogeneity of Coal at Nano-to-Micro Scale Using Combined Nanoindentation and FESEM-EDS

Details

• Personal Author:
  Liu A ; Liu B ; Liu S ; Liu T ; Liu Y
• Description:
  The variations of mechanical properties of coals in nano-to-micro scale play vital roles in defining the coal deformative and failure behaviors with a wide range of engineering applications, including coal stimulation for gas recovery and/or CO2 sequestration in coal seams. Based on the assumption that the heterogeneity in the mechanical properties of coals is combinedly determined by the mineralogical/carbon compositions and microstructures, three coals were experimentally measured through combing nanoindentation test, X-ray diffraction (XRD) analysis and field emission scanning electron microscopy - energy dispersive spectroscopy (FESEM-EDS) imaging. Two sub-bituminous coals from Illinois basin and one bituminous coal from Pittsburgh No.8 seam from Pennsylvania were collected and prepared. The moduli, hardness, and energy dissipations were all analyzed for three coals. The mean Young's moduli and hardness of two sub-bituminous and bituminous coals are approx. 4.13 GPa, approx. 4.79 GPa, and approx. 5.56 GPa respectively and the mean hardness of which are approx. 0.38 GPa, approx.0.49 GPa and approx. 0.58 GPa respectively. The results confirmed that the nanoscale mechanical properties are compositional and microstructural dependent. It was also observed that the heterogeneity of sub-bituminous coals is more apparent than the bituminous coal. Also, the bituminous coal is more harder and brittle than sub-bituminous coal, which can better withhold the mechanical response, but the deformations are relatively permanent due to brittle failure. The energy dissipation data showed that the irreversible work decreases with the increase in hardness, which confirmed that the plastic deformation is much more easily to be inducted. The mechanism-based phenomenon pop-in event on the load-displacement curve was also analyzed by linking with the characteristics of the morphology and composition beneath a pointed indenter or cracks formation due to the localized indent. [Description provided by NIOSH]
• Subjects:
  Occupational Health Safety
• Keywords:
  Author Keywords: FESEM-EDS Coal Mines Failure Analysis Geotechnical Engineering Heterogeneity Mechanical Properties Testing Nanoindentation Nanoscale Proppant Embedment Scanning Electron Microscopy X-ray Diffraction

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• ISSN:
  0166-5162
• Document Type:
  Text
• Funding:
  Contract
• Genre:
  Journal Article
• Place as Subject:
  Illinois ; OSHA Region 3 ; OSHA Region 5 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  261
• NIOSHTIC Number:
  nn:20067871
• Citation:
  Int J Coal Geol 2022 Sep; 261:104081
• Contact Point Address:
  Shimin Liu, Department of Energy and Mineral Engineering, G3 Center and Energy Institute, The Pennsylvania State University, University Park, PA 16802, USA
• Email:
  szl3@psu.edu
• Federal Fiscal Year:
  2022
• Performing Organization:
  Pennsylvania State University
• Peer Reviewed:
  True
• Start Date:
  20190827
• Source Full Name:
  International Journal of Coal Geology
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:4e157066355f76003043e8a8b555d59d1af2107b3535efe9c3d16bf3337a5b6dc0c3e5066a4114d005220c3719857d810eae6550c517deda0187cf1ff4901252
• Download URL:
  https://stacks.cdc.gov/view/cdc/230110/cdc_230110_DS1.pdf
• File Type:
  [PDF - 10.98 MB ]