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Light and Color Production
Published in John A. Conkling, Christopher J. Mocella, Chemistry of Pyrotechnics, 2019
John A. Conkling, Christopher J. Mocella
Strontium nitrate, Sr(NO3)2, is often used as a combination oxidizer/color source in red flame mixtures. A “hotter” oxidizer, such as potassium perchlorate, is frequently used in addition to help achieve higher temperatures and faster burning rates, as well as introduce chlorine to the system. Strontium nitrate, notably, is rather hygroscopic, and therefore water should not be used to moisten a binder for mixtures using this oxidizer. Strontium carbonate is much less hygroscopic and can give a beautiful red flame under suitable conditions. However, it contains an, essentially, pyrotechnically-inert anion, the carbonate ion CO32−. Low percentages of this chemical should be used to avoid burning difficulties.
Study of Combustion Characteristics of Magnesium/Strontium Nitrate and Magnesium/Sodium Nitrate Pyrotechnics Under Low Pressure Environment
Published in Combustion Science and Technology, 2023
Zefeng Guo, Hua Guan, Chengkuan Shi, Bohuai Zhou
Magnesium/nitrate mixtures are the most common pyrotechnics and are widely used in military and civilian applications, such as illuminators, signaling agents, decoys, and propellants (Bagherpour, Mahdavi, and Abedini 2019; Johnston 2002; Sadek et al. 2017; Singh, Somayajulu, and Bhaskara Rao 1989). So far, many scholars have studied the reaction mechanism, combustion performance and luminescence of magnesium/nitrate system pyrotechnics at atmospheric pressure. It is generally considered that magnesium, which acts as a combustible agent, is oxidized and releases a large amount of heat during the combustion process, providing sufficient energy to maintain the stable combustion of pyrotechnics. Magnesium oxide is a typical incandescent emitter, producing an intense white light in a high temperature flame (Conkling and Mocella 2019; Tuukkanen et al. 2006; Wada 1995). As an oxidizer, nitrate decomposes during combustion to provide oxygen for the combustion of pyrotechnics. At the same time, the colorful light emitters produced by nitrate decomposition will give the flame a light signal of different colors. Sodium nitrate and strontium nitrate, as common nitrates, provide yellow and red characteristic emitters during burning process, respectively. Magnesium/nitrate pyrotechnic mixtures undergo two main reaction phases during combustion: Firstly, magnesium and molten nitrate react in the condensed phase to produce magnesium oxide, nitrogen gas and colored light emitters; then, the residual magnesium undergoes secondary combustion with oxygen of air in the gas phase flame. The reaction equations for the whole process are shown below (Pouretedal and Ebadpour 2014; Pouretedal and Mousavi 2018; Pouretedal and Ravanbod 2015; Tuukkanen et al. 2004).