Coal Interface Modified by the Nanofluid: Insights from Dynamic Adsorption Wetting to Structural Weakening

Area of Science:

• Geotechnical Engineering
• Materials Science
• Fluid Dynamics

Background:

• Silica (SiO2) nanofluids show promise for modifying coal properties.
• Prewetting time is a critical factor influencing nanofluid effectiveness in coal seams.

Purpose of the Study:

• To investigate the impact of SiO2 nanofluid prewetting time on coal's mechanical behavior.
• To understand the effects on energy dissipation and fracture propagation.
• To elucidate the underlying fluid dynamic mechanisms.

Main Methods:

• Systematic investigation of prewetting times.
• Measurement of coal mechanical properties (elastic modulus, peak stress).
• Analysis of energy dissipation using ring-down counts.
• Application of Langmuir adsorption theory and Young's equation.

Main Results:

• SiO2 nanofluid prewetting reduces dynamic contact angles and enhances coal hydrophilicity.
• Optimal prewetting (2 hours) significantly weakens coal, reducing elastic modulus and peak stress.
• Internal crack propagation and fracture development intensify at 2 hours, shifting failure mode.
• Prolonged prewetting leads to nanoparticle aggregation, limiting further enhancement.

Conclusions:

• Prewetting time critically controls SiO2 nanofluid efficacy in coal modification.
• Optimal prewetting enhances water absorption and structural weakening, influencing failure modes.
• Findings provide a basis for optimizing prewetting duration in coal seam water injection.