The combustion performance of nanosilicon based energetic materials
Abstract
The reactive properties of energetic composite materials change dramatically within the nanoscale domain, below 100 nm. Nanoenergetic composites, or nanoenergetics, have high surface areas, small diffusion scales, and consequently dramatically faster reaction rates. This thesis reports work done to characterize the combustion performance of silicon-based nanoenergetic composites in order to give us a better understanding of their properties so that they can be tailored to specific applications. Specifically, the combustion properties of silicon nanopowder(nSi) energetic composites and nanoporous silicon (nPSi) energetic composites are studied. This thesis contains a thorough review the current state of silicon-based reactives, focusing on fabrication and combustion of nPSi-based energetic composites and also on the combustion of nSi-based energetic composite. The Combustion properties of nSi composites were studied by performing equilibrium calculations, “flame tests”, instrumented burn tube experiments and micro capillary tube burns. Equilibrium calculations show that the maximum predicted flame temperature for many Si/oxidizer systems is about 3000 K, with some exceptions. Specifically, the calculated flame temperatures for Si/metal oxides systems ranged from 2282 to 2978 K. Theoretical maximum gas production of the Si composites ranged from 350-6500 cm3/g, with Si/NH4ClO4 producing the most gas and Si/Fe2O3 producing the least. Composites consisting of nSi/NH4ClO4, nSi/KMnO 4, and nSi/NaClO4 x H2O were tested in instrumented burn tubes. The composite nSi/NH4ClO4 showed the fastest burning rates which approached 530 m/s. Micro-capillary tubes were loaded with nSi/CuO and nSi/Bi2O 3 composites. Successful combustion propagation of these systems was achieved in capillary tubes with inner diameters of 150 and 250 μm . The combustion performance of oxidizer filled nanoporous silicon (nPSi) was also studied. nPSi samples with diameters of 2.54 cm were fabricated by electrochemical etching. The porosity of the samples ranged from 50% to 82%. The samples were cut into 3-5 mm strips and filled with an oxidizer. The nPSi samples were filled with the oxidizers NaClO4 x 1H2O, Ca(ClO4)2 x 4H2O, sulfur and perfluoropolyether (PFPE). The loaded nPSi was then burned by igniting the sample with a hot Nichrome™ wire. The experiments were recorded using high speed photography from which burning rates were calculated. The burning rates did showed a strong dependency on quality of the oxidizer loading. The nPSi loaded with NaClO4 x 1H2O produced burning rates that ranged from 115-550 cm/s. nPSi loaded with Ca(ClO 4)2 x 4H2O had burning rates of 145-285 cm/s. A sulfur filled nPSi sample burned a rate of 16 to 290 cm/s, and perfluoropolyether loaded PSi burned at a rate of 1.4 cm/s.
Degree
M.S.M.E.
Advisors
Son, Purdue University.
Subject Area
Mechanical engineering
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