Kinetic analysis of thermite reaction in Al–Ti–Fe2O3 system to produce (Fe,Ti)3Al–Al2O3 nanocomposite

Quo Vadis, Nanothermite? A Review of Recent Progress

One of the groups of pyrotechnic compositions is thermite compositions, so-called thermites, which consist of an oxidant, usually in the form of a metal oxide or salt, and a free metal, which is the fuel. A characteristic feature of termite combustion reactions, apart from their extremely high exothermicity, is that they proceed, for the most part, in liquid and solid phases. Nanothermites are compositions, which include at least one component whose particles size is on the order of nanometers. The properties of nanothermites, such as high linear burning velocities, high reaction heats, high sensitivity to stimuli, low ignition temperature, ability to create hybrid compositions with other high-energy materials allow for a wide range of applications. Among the applications of nanothermites, one should mention igniters, detonators, microdetonators, micromotors, detectors, elements of detonation chain or elements allowing self-destruction of systems (e.g., microchips). The aim of this work is to discuss the preparation methods, research methods, direction of the future development, eventual challenges or problems and to highlight the applications and emerging novel avenues of use of these compositions.

Combustion Synthesis of FeAl-based Composites from Thermitic and Intermetallic Reactions

Combustion syntheses involving intermetallic and thermitic reactions were conducted to fabricate FeAl–TiB2–Al2O3 composites. Two combustion systems consisting of Fe, Al, Ti, Fe2O3 and B2O3 were studied for formation of xFeAl–yTiB2–Al2O3 composites with x = 1.5–3.5 and y = 0.5–0.8. In the reaction series, thermitic reduction of Fe2O3 and B2O3 by Al thermally activated the reaction between Fe and Al. As a result, the combustion wave of the synthesis reaction was sufficiently exothermic to propagate in a self-sustaining manner. With an increase in TiB2 and FeAl of the composites, the decrease of reaction exothermicity resulted in a decline of the combustion wave velocity and reaction temperature. The activation energy Ea = 88.92 kJ/mol was deduced for the synergetic combustion reaction. Based on XRD analysis, a thorough phase conversion was achieved and composites composed of FeAl, TiB2, and Al2O3 with different contents were obtained. The SEM micrograph showed the FeAl-based composite with a dense and connecting morphology.

EBSD investigation of Al/(Al13 Fe4 +Al2 O3 ) nanocomposites fabricated by mechanical milling and friction stir processing

The application of ball-milling for reactant powders (Fe₂ O₃ +Al) to form in situ nanosized reaction products in the stir zone of 1050 aluminium alloy was examined and the evolution of microstructure, grain boundaries and microtexture of the fabricated Al/(Al₁₃ Fe₄ +Al₂ O₃ ) nanocomposite was investigated. The mean matrix grain size of the fabricated nanocomposites by the combination of ball milling and friction stir processing were found to be ∼3.2, 3.1 and 2.1 μm for 1, 2 and 3 h milled powder mixtures, respectively. The fraction of high-angle grain boundaries increased markedly in the stir zone indicating the occurrence of dynamic restoration of the aluminium matrix. This was also associated with increasing of the fraction of low ∑CSL boundaries. In addition, the fraction of high-angle grain boundaries increased as the reaction product increased. The developed textures were compared with the most important deformation and recrystallisation texture components of cubic close packed structure. Some of the main texture components formed due to the restoration of aluminium in the stir zone of the material with no powder addition were Cube_ND {001}<310>, BR {236}<385> and R (or retained S{123} <634>); these are usually found in the rolled materials. However, the presence of nanosized reaction products in the fabricated nanocomposite changed the texture components to the dominant Goss {011}<100>, P {011}<122> and R{124}<211> textures.