Spectroscopic Study of Metal Vapor Kinetics

The purpose of this project was the formulation and evaluation of pyrotechnic mixtures for release of aluminum and iron vapors. In the program which is the subject of the present report, WO3, Zr, Al, Fe, and Fe2O3 powders were mixed in different proportions, pressed into strands with masses of 15 to 25 gm, and burned mostly at subatmospheric pressure. This type of release is based on the fact that metallic Al (or Fe) is the most volatile component among the flame products of any given formulation, so the product gas will consist predominantly of Al (or Fe) vapor; the detailed thermodynamics is discussed. The performance of the mixtures was judged by (a) qualitative observation of the plumes recorded by a movie camera; (b) burning-time, hence average linear burning-rate, measurement; and (c) quantitative absorption spectroscopy of Al and Fe vapors. Details of the two absorption-spectroscopy methods used are presented.