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Here we report on a single-step, eco-friendly, and facile approach to combustion-assisted reprocessing of oily copper waste into copper powder without preliminary cleaning. Complete reduction of copper from oily copper waste in the combustion wave was reached in the presence of ammonium nitrate and without introducing any reducing agent. The optimal conditions for obtaining >99 % copper powder were reached for green [Cu2O + m(oil)] + xNt mixtures with m = 7–11 wt % and x = 0.35–0.55, were m stands in wt % and x in mole fractions, both in relation to 1 g-mol of Cu2O. In scale-up experiments (up to 10 kg of green mixture), the copper powder with oxygen content below 0.5 wt % and free carbon content below 0.25 wt % was successfully produced. Our approach was also successfully applied to combustion-assisted reduction of copper oxide oily waste mixed with nickel oxide to yield composite powders and Cu–Ni alloys.

Kinetic studies were performed utilizing high-speed temperature scanner in the Ni-Al system including those with and without mechanical activation (MA) of different duration in a planetary ball mill, with and without using carbon nanoadditives (NA). The temperature profiles were taken and treated at different heating rates from 100 up to 2600 °C/min considering the influence of activation duration and the role of nanoadditive on the characteristic points of thermograms. Kissinger method allowed to evaluate activation energy (Ea) for non-activated, activated (1, 2, 3, 5 min), nanoadditive (1 wt.%) containing and nanoadditive (1 wt.%) containing mechanoactivated (1, 3, 5 min) mixtures. The beneficial influence of NA on the interaction between Ni and Al in the non-activated and moderately mechanoactivated mixtures was demonstrated. The influence of MA and NA on the microstructure features and phase formation sequence at various heating rates were revealed. For all the mixtures under study, T* characteristic temperatures (the temperature, where the maximum exothermic effect was observed) were found to increase with increasing heating rates. It was unravelled that mechanical treatment leads to significant changes in the reaction kinetics and phase formation laws. Particularly, in an activated mixture, the formation of Ni3Al is followed by NiAl intermetallic, in contrast to non-activated mixture, where the reaction proceeds only with the NiAl formation. The both MA in 1 min and addition of 1 wt.% NA decreased the activation energy of the Ni-Al reaction, exhibiting commensurate impact on the effective activation energy value of the Ni-Al system. However, > 3 min MA in the presence of 1 wt.% NA have prohibitive effect on the reaction in the Ni-Al system.

The combustion synthesis process activated by organic polymers (Teflon and polystyrene) in the SiO2/Al/C system is investigated under the counter-current and co-current degassing conditions. It is found that the combustion parameters, i.e. wave velocity and temperature, and final product microstructure are influenced by the degassing mode considered as well as the type and amount of promoters added to the starting mixture. In particular, the combustion wave results to accelerate during its propagation when adopting the forward infiltration configuration and in absence of polystyrene. In addition, under the same degassing condition, the produced gases are found to provide a specific orientation on the growth direction of thread-like SiC crystals during final product formation.

The synthesis of alumina/silicon carbide composites by self-propagating reactions activated by Teflon is investigated. It is shown that small amounts of this material (i.e. 0.20–0.25 wt.%) guarantee the occurrence of self-propagation reactions leading to the formation of a composite. In particular, under argon atmosphere, it consists of well-formed crystals of alumina, fine grained silicon carbide and whiskers-shaped crystallites of SiC. On the other hand, aluminium nitride, silicon carbonitride/silicon cyanide, aluminum oxynitrisilicides and mullite are also found under nitrogen atmosphere. The content of SiC whiskers in the final product increases when powdered polymers (polystyrene, polyethylene, polypropylene) are added to the initial mixture together with Teflon.

The mechanism of initiation and combustion of the 3SiO2-4Al-3C system is studied under conditions of activation of the combustion reaction by a high-energy additive of Al+αKNO3. It is shown that combustion of this system is possible only when a certain quantity of the additive is introduced into the starting mixture. The mechanism of activation of the reaction is established, and the processes involved in the reduction stage of the combustion are shown to play a leading role in the reaction. Optimal conditions for synthesis of a SiC/Al2O3 composite powder containing SiC fibers are determined.