Mathematical models developed by Siberian scientists will predict the occurrence of complex thermal processes in the powder mixture of nickel and aluminum
An article titled "High-temperature synthesis in activated powder mixtures under conditions of linear heating: Ni-Al system" prepared by Vadim Prokofiev, Lead Researcher (Department for Structural Macrokinetics TSC SB RAS, professor (TSU), and Valery Filimonov, Lead Researcher (Institute for Water and Environmental Problems SB RAS), professor (Altai State Technical University, Barnaul) will be published in the scientific journal Combustion and Flame (Q1) in early 2021.
Using the methods of mathematical modeling, the Siberian scientists were able to show the process of high-temperature synthesis in a mechanically activated powder mixture of nickel and aluminum subjected to heating from an external source, confirming the experimental data. One of the most significant results was that the researchers were the first to propose criteria for the dependence of the ignition temperature of the mixture on the time taken to activate the mechanical mixture.
As the authors explain, obtaining intermetallic compounds (materials composed of two or more types of metals) for creating composite materials with unique properties is among the most important tasks of materials science. Therefore, powder metallurgy technologies, including those using high-temperature synthesis methods, are being actively developed. That is why it is very important to deeply understand this process and describe its optimal conditions.
“At the first stage the mixture is ground in planetary mills, which helps form the needed structure of the powder, purify it from oxides and impurities", Vadim Gennadyevich says. “Then the sample is formed from the powder and subjected to high-temperature synthesis. Preliminary grinding of particles simplifies the chemical reaction process and reduces its activation barrier.
Earlier, several groups of researchers from Russia and the United States examined these processes and reported experimental results for the nickel-aluminum mixture, which is one of the most common. But it is always important to supplement the experimental data with calculations obtained by mathematical modeling methods. V.G. Prokofiev and V.Yu. Filimonov, whose collaboration has been successfully developing for ten years, began to solve this task.
An important step was the solution of an interesting nonlinear problem that took about half a year: a serious difficulty was the fact that the number of described parameters was constantly changing by several orders of magnitude. The more significant were the calculations obtained: they confirmed the experimental data obtained earlier. In the article, the scientists presented a description of the dynamic thermal explosion process. One of the interesting points described in the article was the obtaining of criteria establishing the dependence of the ignition temperature on the optimal time of mechanical activation of the mixture, which will make it possible to predict the optimal conditions for controlling the combustion process. The obtained mathematical models can be applied to other mixtures in the future and will certainly be useful to experimentalists.