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16XV International Symposium on Self-Propagating High-Temperature Synthesis
TEMPERATURE MEASUREMENTS OF THE COMBUSTION WAVE BY DYNAMIC SPECTROMETRY
V. G. Salamatov*", A. I. KirdyashkinA, and V. D. KitlerA
aMerzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of
Sciences, Chernogolovka, Moscow, 142432 Russia
bTomsk Scientific Center, Siberian Branch, Russian Academy of Sciences,
Tomsk, 634055 Russia
*e-mail: Salamvit@yandex.ru
DOI: 10.24411/9999-0014A-2019-10143
Temperature measurements are of importance to understand the kinetics of chemical conversions in a reaction wave of rapid high-temperature combustion [1]. Optical pyrometry methods are the most promising for solving this problem. Spectral pyrometry (thermal spectrum thermometry) [2, 3] of heated materials is a method that does not require, in contrast to brightness and color pyrometry, experimental and model concepts of the emissivity factor for the object under study. The latter is achieved by observing the distribution of the radiation intensity of a heated body in a wide range of wavelengths to identify the interval where the profile of the thermal spectrum is described by the Planck function. This work provides the temperature measurements of the SHS reaction wave for mixtures with a composition (1 - x)(Ni + 30 wt % Al) + xCaCo3, where x is the mass of the gasifying additive using dynamic spectrometry [3]. The processes were monitored using high speed video recording (Motion ProX-3), the frame frequency was up to 10.000 s-1, and by dynamic monitoring of emission spectra (HR 4000-Ocean Optics spectrometer, range of wavelengths is 200 ^ 1100 nm, optical resolution is 0.2 nm).The gasifying additive is shown to form a porous drop structure of the reaction product. Here, according to the analysis of the high-speed video data and the dynamic spectrometry of combustion, the formation of drops is accompanied by bright flashes, the temperature of which is 200^400 K higher than the relatively homogeneous temperature in the zone of the reaction wave. The addition of CaCO3 to the initial mixture destructs oxide films on the surface of the particles, which, in turn, decreases the surface tension of melts and creates conditions for the formation of drops in the heating zone. During the formation of drops, a gap is formed between them and the initial mixture. The gap prevents the transfer of heat from the heated drop of the initial mixture, which leads to its overheating and decrease in melt viscosity. The movement of drops on the surface is accompanied by their merging or sticking to each other. The latter leads to the formation of chains of drops stuck together. Increasing the initial density of the samples leads to the formation of a foamed structure of the product. The structure is formed in a narrow zone adjacent to the combustion front. As in the first case, reaction sources (drops) are formed in the front, move within the voids formed by the merging of the initial particles into drops and combine into small agglomerates. The high initial density explains the homogeneous, along the entire length of the front, temperature of the sample, and also the restriction of the free movement and growth of drops. This work was supported by RFBR (project no. 19-03-00081 A).
1. E.A. Levashov, A.S. Mukasyan, et. al., Self-propagating high-temperature synthesis of advanced materials and coatings, Int. Mater. Rev., 2017, vol. 62, no. 4, pp. 203-239.
2. A.N. Magunov, Spectral pyrometry (review), J. Instrum. Exp. Tech., 2009, vol. 52, no 4, pp.451-472.
3. V.G. Salamatov, A.I. Kirdyashkin, et. al., Combustion of composite Ni-Al fibers, J. Phys.: Conf. Ser, 2018, vol. 1115, 042033.
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