| Composite material Ag/Al2O3 synthesized by chemical reaction was observed its microstructure morphology, Determine the crystal structure of the intermediate compound alloys and the phase relationship of the matrix and the precipitates phase through SEM and XRD Expatiated on the processes of alloy compounds transforming to the enrichment region, searching the transition state and at last resulting to a stable phase during the reaction, from the standpoint of electron-atom-level and do the theoretical calculation of the new metastable phase which would generate in the process of the entire reaction and the new phase which was observed during the experiment from the standpoint of energy and the thermodynamic stability. It turns out that the activation capability of Al is better than that of Ag; the participation of oxygen supply was playing a leading role in the reaction process. Search for the characterization of the interface microstructure, such as matrix and the reinforced phase, the new and the reinforced phase. And explain the decomposing free O from the initial reaction mixture is another important way to make the oxidation reaction continually and completely. At last speculate the complete reaction path.From the electron-atom-level analysis, in the tin-rich region of reaction process, it demonstrated the specific location of O in the unit cells of Ag and Sn, the factors of instability of the degree of solute composition in Al(Ag)-sosoloid and Ag(Al)- sosoloid, in the energy system.The analysis of the reaction mechanism about matrix-Ag, doped metal-Al and O pointed that the bonding capacity between Al-O is significantly higher than that between Ag-O, Sn integrates with O will reduce system energy, it explains why O atoms combine with Al atoms but not Ag atoms through a proliferation of long-range. The absolute value of binding energy in transition phase during reaction process is: Al2O3>A1O>Ag3O4>Al2O> Ag2O2> Ag2O3> Ag2O> Ag6O2> AgO, The stability of AgxOY-phase is the worst. Enthalpy of formation followed by the size of Al2O>3> AlO> Al2O> Ag6O2> Ag2O2> Ag2O> Ag3O4> Ag2O3> AgO. The formation of Al oxides can be formed easily during the reaction, and more stable than oxide Ag, The most important reason is Al and O and the role of pro-big Resting on the transition state oxide throughout the reaction process may occur in, Summarized a detailed reaction path in order.The reaction may occur during the transition phase AlxOy and AgxOy, AgxOy relatively poor stability of the transition phase with increasing temperature decomposition of the O as the source of the oxidation process; reaction is a diffusion time of the first highly O, followed by higher levels of active Al, the last for the inert Ag; in the cooling process, O and Al O greater than the affinity with Ag, O and Al in elemental Ag precipitates around. And simulation using the method of milling Al-Ag solid solution Ago.gAlo.2, Ag0.65Al0.35, Ag0.75Al0.25, Ag0.667Al0.333, Ag0.842Al0.158 oxidizing atmosphere in the diffusion and transformation of the formation of Ag process was studied, when the Al-Ag solid solution, oxidation, the powder surface AlxOy structure, precipitation of elemental Ag, for the oxidation of elemental Ag precipitates to power, the internal powder form AgxAly unstable structure, system precipitation in the oxidation process, the existence of Ag precipitation and Al2O3 oxide film formation rate of the two processes conflict with each other, resulting in the precipitation amount subject to the control Ag, with the calculated binding energy of each phase are basically the same. By controlling the Al-Ag solid solution, the oxidation reaction rate, Ag diffusion and the short path to the formation of Al2O3 compact oxide film prepared by high-temperature stable performance Ag/AlO3 powder composites are feasible. |
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