Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA.
Department of Mathematics, Australian College of Kuwait, Safat 13015, Kuwait.
Molecules. 2019 Mar 23;24(6):1163. doi: 10.3390/molecules24061163.
Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn⁻Wall, and Kissinger models were 105.9 ± 1.4 kJ mol, 102.1 ± 2.7 kJ mol, and 105.8 ± 1.6 kJ mol, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.
当时间是需要考虑的关键因素时，低挥发性物质的非等温热升华动力学比等温热升华数据更有利，特别是在探测爆炸物的领域。在本文中，我们报告了使用升温紫外-可见吸收光谱法在不同加热速率下原位测量空气中 2,4,6-三硝基甲苯（TNT）连续纳米薄膜升华活化能的实验结果。TNT 薄膜是通过旋涂沉积技术制备的。首次使用热重分析（TGA）和差示扫描量热法（DSC）中最广泛使用的程序来确定升华率，在这项工作中使用了紫外-可见吸收光谱法。使用三种成熟的计算技术分析了升华动力学。基于 Ozawa、Flynn-Wall 和 Kissinger 模型的非等温热力学活化能值分别为 105.9 ± 1.4 kJ/mol、102.1 ± 2.7 kJ/mol 和 105.8 ± 1.6 kJ/mol。计算出的活化能与我们之前使用紫外-可见吸收光谱法报告的 TNT 纳米薄膜等温热升华动力学的测量值吻合良好。结果表明，成熟的非等温热分析技术可以成功地应用于纳米尺度，使用吸收光谱法来确定升华动力学。
