Acceleration of decomposition of CL-20 explosive under nanoconfinement
- PDF / 1,677,730 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 48 Downloads / 160 Views
Acceleration of decomposition of CL‑20 explosive under nanoconfinement Rozana Bari1 · Aric A. Denton1 · Zachary T. Fondren1 · Gregory B. McKenna1 · Sindee L. Simon1 Received: 18 May 2019 / Accepted: 5 November 2019 © Akadémiai Kiadó, Budapest, Hungary 2019
Abstract The thermal properties of CL-20 explosive in the bulk and confined in controlled pore glass matrices to nanoscale dimensions were studied using dynamic differential scanning calorimetry. The decomposition reaction of the CL-20 was found to be accelerated in 12-nm-diameter pores compared to the bulk CL-20 with the onset of the decomposition occurring 16–24 °C lower and a fourfold to sevenfold larger reaction rate constant. The total heat of decomposition was found to be independent of pore size and heating rate, and the average activation energy for all samples was found to be 160 ± 7 kJ mol−1. Keywords CL-20 · Nanoconfinement · Decomposition kinetics
Introduction The effects of nanoconfinement on the thermal properties of several small-molecule organics in controlled pore glasses (CPGs) were first explored by Jackson and McKenna, who reported depressions of both the melting point [1] and the glass transition temperature [2]. A size-dependent melting point depression has also been observed for explosives such as trinitrotoluene (TNT) [3] and pentaerythritol tetranitrate (PETN) [4] confined in CPGs. Nanoconfinement is also known to influence reactions. For example, polymerizations can be accelerated under nanoconfinement [5–10]. In contrast, Abudakka et al. [11] found that the onset of degradation shifted to a higher temperature for poly(ethylene oxide) under confinement in anodic aluminum oxide (AAO). Similarly, work by Cheng and McKenna [12] on the pharmaceutical material nifedipine showed an increase in the decomposition temperature upon confinement in a CPG having 12-nm-diameter pores. Hexanitrohexaazaisowurtzitane (C6H6N12O12), also known as CL-20 or HNIW, is a nitramine-based explosive. The decomposition of CL-20 has been studied using isothermal * Gregory B. McKenna [email protected] * Sindee L. Simon [email protected] 1
Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA
and dynamic calorimetry by several groups [13–26], and comparison of the decomposition kinetics among the α, ε, and γ polymorphs shows that the γ polymorph decomposes with the fastest kinetics [14]. However, the effects of nanoconfinement on the decomposition of CL-20 have not been previously investigated. The present work presents results from a study of the characterization of the kinetics of decomposition of CL-20 in the bulk and confined in CPGs with 12-nm-diameter and 50-nm-diameter pores. Thermal properties were investigated using differential scanning calorimetry (DSC), and the onset of decomposition, total heat of decomposition, activation energy, and reaction rate constants were determined, and finally the parameters were compared with literature values for the bulk material.
Methodology Materials CL-20 (purity = 99% by high-
Data Loading...
