Oxidation of tantalum metal by lead peroxide and red lead

Abstract

The kinetics of oxidation of metallic fuels by metal oxides involve some of the most important parameters determining the utility of any metal oxide system in pyrotechnic applications. An attempt has been made to study the oxidation of Ta metal by strong oxidizers such as PbO~ and Pb30,l, employing differential thermal analysis and infrared spectroscopy. The rate of oxidation of Ta increases with increasing oxidizer content in both Ta--PbO2 and Ta--Pb304, systems. A tentative mechanism for the observed phenomenon is proposed.A metal oxidant composition is used as the main part of a pyrotechnic delay column in fuses. The delays required in the fuses may range from a few seconds to a few milliseconds. The kinetics of oxidation of the metal fuel, which are determined predominantly by the oxidizer employed, control the delay timings. Though any metal -oxidizer system is potentially an effective delay composition, metals such as Si, Zr, Ni, Mo, Ti, B and W in conjunction with oxidizers such as chromate, chlorate, nitrate, perchlorate, Fe203 and Pb~O4 have been suggested for use. Many of the above metals yield oxides of varying stoichiometry and the kinetics will therefore be highly susceptible to changes in the oxidizer and the oxidizer content. Hogan and Gordan [1] were among the first to apply thermal methods to a systematic study of a pyrotechnic delay system. Charsley et al. [2,3] have described the kinetics of oxidation of B and W by oxidizers such as K2Cr207 and MoQ, employing thermal analysis and temperature profile measurements Nagaishi et al, [4] found during their studies on the combustion of W by KC104 in the presence of an auxiliary oxidizer BaCrO4 that different conditions of energy supply can cause apparent inconsistencies in the ignition time recorded in the different thermal methods.Ta on the other hand always yields TarO5 in an oxidizing atmosphere, the oxidation reaction being reported to be highly exothermic. Since no information is available in the literature on the system Ta + strong oxidizers, we have investigated the systems Ta + PbO2 and Ta + Pb30~, employing DTA and infrared spectroscopy, the results of which are described in this communication.