Abstract
Understanding of the decisive role of non-isothermal treatment on the interaction mechanism and kinetics of the MoO3-CuO-Mg-C system is highly relevant for the elaboration of optimal conditions at obtaining Mo-Cu composite powder in the combustion processes. The reduction pathway of copper and molybdenum oxides with combined Mg + C reducing agents at high heating rates from 100 to 5200 K min−1 was delivered. In particular the sequence of the reactions in all the studied binary, ternary and quaternary systems contemporaneously demonstrating the effect of the heating rate on products’ phase composition and microstructure was elucidated. The combination of two highly exothermic and speedy reactions (MoO3 + 3Mg and CuO + Mg vs. MoO3 + CuO + 4Mg) led to a slow interaction with weak self-heating (dysynergistic effect) due to a change in the reaction mechanism. Furthermore, it has been shown that upon the simultaneous utilization of the Mg and C reducing agents, the process initiates exclusively with carbothermic reduction, and at relatively high temperatures it continues with magnesiothermic reaction. The effective activation energy values of the magnesiothermic stages of the studied reactions were determined by Kissinger isoconversional method.
Highlights
W, Mo and their multicomponent alloys are nominated as potential candidates for plasma facing materials (PFMs) simultaneously possessing high melting temperature, high thermal conductivity, thermal fatigue, low vapor pressure and low sputtering erosion yield [1,2,3]
We report the results of study of the reaction mechanism in CuO-MoO3-Mg-C powder mixtures under conditions of high heating rates up to temperature 1573 K through revealing reactions’ sequences and the phase- and microstructure formation patterns by high-speed temperature scanner (HSTS)-1 setup
The study of a separate and joint reduction mechanism of copper and molybdenum oxides with combined reducers (Mg + C) under the fast-heating conditions revealed that, in all the studied systems (CuO-Mg-C, MoO3-Mg-C, CuO-MoO3-Mg-C), the reduction process of copper oxide starts at a lower temperature compared to molybdenum oxide
Summary
W, Mo and their multicomponent alloys are nominated as potential candidates for plasma facing materials (PFMs) simultaneously possessing high melting temperature, high thermal conductivity, thermal fatigue, low vapor pressure and low sputtering erosion yield [1,2,3]. The modeling of the combustion process at controllable conditions (e.g., with programmed heating rates and tuning the process within the time at conditions closer to heating rates and temperatures in the combustion wave) will tackle the examination of the reaction pathway The latter was studied so far by means of X-ray diffraction, electron microscopy and thermal analysis techniques without consideration the influence of high heating rates on the interaction dynamics. Motivated by the open questions and technical difficulties of combustion kinetics exploration, our current study is aimed to disclose the interaction pathway at high heating rates in the MoO3-CuO-Mg-C system by a novel thermal analysis technique, called high-speed temperature scanner (HSTS) [15,16,17,18]
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