Microwave antenna focusing for spatially resolved modulation of burn rate

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-07, Vol.492, p.152192, Article 152192
• Main Authors: Shi, Keren, Wang, Yujie, Zachariah, Michael R.
• Format: Article
• Language: English
• Subjects: Combustion modulation; Microwave stimulation; Nanothermites
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.152192

•Localized hotspots of different temperatures were remotely generated by embedding a MW receiving antenna.•Local burn rates augmentation tracks the spatial distribution of the hotspot profiles, with a peak burn rate increase of ∼6x at ∼200 °C.•A measured effective activation energy of 18 kJ/mol implies a transport limit during propagation under MW stimulation. This study explores the ability to dynamically modulate the burn rate of nanothermites through microwave generated heat zones. These heat zones were generated by embedding a microwave receiving antenna in 3D printed Al/CuO samples. These thermal hot spots in the nanothermites are generated by the induced high electric fields at the terminus of an embedded receiving antenna and are monitored by an IR camera. The burn rates were investigated for different MW induced hot spot temperatures, geometries and receiving antenna materials. The local burn rate increase closely tracks the hot spot spatial distribution, and for our experimental condition enabled an amplification of burn rate of ∼6×. An effective burn rate activation energy was calculated to be ∼18 kJ/mol from the Arrhenius plot of local burn rate and initial temperature. Three color pyrometry confirms that the main mechanism of the local burn rate increase is related to the initial temperature profile in the sample. This study demonstrates the sensitivity of the local burn rate of nanothermites to initial temperature and provides a new approach to modulate the burn rate by localizing MW energy.