Burning velocities in catalytically assisted self-propagating high-temperature combustion synthesis systems

Abstract

The current work presents an experimental study of catalytically assisted self-propagating high-temperature synthesis (SHS) of the tantalum/carbon material system. The effects of controlled amounts of two gas-phase transport agents (carbon dioxide and vaporized iodine) were examined. The gas-phase transport agents resulted in burning velocities 2 to 4 times faster than burning velocities observed in comparable catalytically assisted and unassisted Ta/C SHS systems. The gas-phase transport agents clearly augment the combustion synthesis process. The burning velocities of the catalytically assisted, non-melting SHS systems were found to be strong functions of particle size, pressure and the amount of gas-transport agent present. The results are compared with previous studies of both catalytically assisted and unassisted Ta/C SHS, and discussed in the context of proposed transport mechanisms.

WITHDRAWN: Effects of different factors on the heat conduction properties of micro-structured homogeneous combustion systems

“…The ratio of fuel to air in the admixture introduced into the combustion zone is ultimately determined by the desired operating temperature of the combustion zone. The operating temperature is determined by the theoretical adiabatic ame temperature of the fuel-air admixture passed to the combustor and thus is dependent on the initial temperature of the air as well as the amount of fuel contained therein [21,22]. In certain turbine applications, for example, automobiles, increases or decreases in turbine power often result in an increase or decrease in compressor speed and respectively an increase or decrease in the compression and temperature of the air supplied to the system by the compressor.…”

In-situ measurements of the onset of bulk exothermicity in shock initiation of reactive powder mixtures

“…Unlike molecular explosives, which have a pressure-dependent burning speed r $ p n (n of order 1 or 2), 10,65 the SHS, thermite, and intermetallic compositions that have been studied appear to have burning speeds that are relatively independent of pressure due to the low fraction of gas-phase products. 11,12 The pressure-independence of the burning speed also results in bulk reaction times that are independent of initiating shock strength in contrast to the strong pressure dependence of explosive shock-to-detonation transition times (see Ref. 66 for instance).…”

Nanoenergetics as pressure generator for nontoxic impact primers: Comparison of Al/Bi2O3, Al/CuO, Al/MoO3 nanothermites and Al/PTFE

“…During the two last decades, major progresses have been made in developing highly-exothermic reactive mixtures, especially by reducing the size of reactants below 500 nm. These nanostructured reactive mixtures, called nanoenergetic materials (nEMs), nanothermites or metastable intermolecular composites (MICs) can release energy much faster than conventional energetic material due to the enhanced reactants proximity and higher surface area to volume ratio [2][3][4][5][6][7]. The majority of research on nanoenergetics uses aluminum as fuel mixed with MoO 3 , CuO, Fe 2 O 3 , Bi 2 O 3 , but other oxidizers such as nitrates, iodates or fluoropolymers have also been tested [8,9].…”