Note that the identification of Al2O3 using XRD is evidential from the previous study [51]. In addition to those solid products, gaseous species such as O2 was also possibly formed. It is interesting to reveal the production of AlNi from the Al/NiO check details MIC. As a comparison, the formation of Ni was shown with lower and fewer XRD peaks, while Al still existed as a relatively large amount. Based on these observations, the following reaction was responsible: (7) Figure 5 XRD patterns measured from the reaction product of sample D, 33 wt.% NiO. Note that in this study, MIC Φ = 3.5 contained abundant
Al nanoparticles and thus made the reaction R7 feasible. The propagation of R7 does not necessarily require the completeness of R2 since the decomposition of NiO may occur first and be followed by the reaction between Al and Ni. A further study on elementary reactions related to R2 and R7 is needed in order to gain more insights on this issue. To further characterize these microstructures of the products, the SEM and EDAX analyses were performed on the same product examined
by XRD. Figure 6 shows two typical structures observed from MIC Φ = 3.5: (Figure 6a,c) a sphere which was rich in Ni and Al, and (Figure 6b,d) a bunch of Al2O3 crystalline structures. The coexistence of Ni AC220 purchase and Al in the sphere is possibly in the form of AlNi. Figure 6 SEM images (a, b) and respective EDX patterns (c, d). They were obtained from the reaction products of sample D, 33 wt.% NiO. In order to further examine the possible formation pathway of the AlNi phase,
ab initio MD simulation filipin was conducted for scoping the reaction time scale and identifying the selleck kinase inhibitor equilibrium product of the thermite reaction of the Al/NiO MIC. For this simulation, the initial temperature was set to 0 K. At this temperature, the thermodynamic equilibrium structure of an Al crystalline nanoparticle and a NiO nanowire was obtained, as shown in Figure 7a. The system temperature was then increased to 1,000 K (or 726°C) to ignite the reaction. After ignition, the simulation was done under adiabatic condition. It was found that after 5 ps, as shown in Figure 7b, Al atoms diffused through the Al-NiO interface and met with O atoms (while the diffusion of O atoms into the Al nanoparticle was possible but with a much smaller chance, as observed from the image where only one O atom was found in the Al nanoparticle). Meanwhile, Ni atoms were grouped together and were intended to form the pure Ni phase. It was also observed that the AlNi phase exists at the interface between the Al nanoparticle and the NiO nanowire. Accompanying this fast thermite process, the system temperature was increased up to 3,500 K within 5 ps. This MD simulation confirmed the possibility of forming the AlNi phase from the Al-NiO thermite reaction and revealed the diffusion paths of Al and Ni atoms during the thermite reaction.