Sublimation and Diffusion Kinetics of 2,4,6-Trinitrotoluene (TNT) Single Crystals by Atomic Force Microscopy (AFM)

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Understanding the sublimation behavior of energetic materials like 2,4,6-trinitrotoluene (TNT) is crucial for safety and handling.
• Previous studies on TNT sublimation often relied on indirect measurement techniques.

Purpose of the Study:

• To experimentally determine the in-situ nanoscale sublimation rates, activation energy, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals.
• To investigate the mechanism of TNT sublimation at the nanoscale.

Main Methods:

• Utilized atomic force microscopy (AFM) for in-situ nanoscale measurements.
• Prepared TNT single crystals via slow evaporation of acetone-dissolved TNT at 5 °C.
• Monitored surface area shrinkage of layered islands during isothermal heating to calculate mass loss due to sublimation.

Main Results:

• Sublimation rates were found to be one order of magnitude lower than previously reported values.
• Calculated activation energy for sublimation (112.15 ± 3.2 kJ/mol) aligns with existing literature for TNT thin films and microcrystals.
• Average diffusion coefficient was determined to be (4.35 × 10^-6 m²/s), consistent with theoretical values.

Conclusions:

• The sublimation process of TNT crystals appears to occur via two-dimensional molecular detachment from non-prominent facets.
• The experimental findings provide a more accurate understanding of TNT sublimation kinetics and diffusion at the nanoscale.
• AFM offers a valuable tool for precise characterization of energetic material sublimation properties.