Intermetallic compounds (IMCs) is an important category of materials that have been used in magnetic materials, superconducting materials, hydrogen storage, shape-memory materials, and heterogeneous catalysis. Superior selectivities from catalysts based on IMCs have been observed in hydrogenation, oxidation, steam reforming, and hydroformylation reactions. In heterogeneous catalysis, it is generally desired to synthesize IMC nanoparticles (NPs) with small size, high mono-dispersity, and a single-phase nature. However, this remains challenging despite numerous efforts on engineering the synthesis routes of IMCs. In this talk, I will discuss our study on the formation of ordered IMC at the nanoscale. With the assistance of quantitative PXRD analysis, we find that the transformation to intermetallic is initiated by a surface-specific intermixing stage. The activation barrier for this stage determined from tailored modeling of the experimental kinetics is consistent with DFT analysis of the effective barrier for vacancy-mediated diffusion of metals. A bulk diffusion stage generally follows this stage. Our work develops a detailed picture and characterization of the kinetics of IMC formation at the nanoscale. The key aspects of this work can likely be generalized to benefit the synthesis route for the designing of intermetallic systems, being useful in a broad spectrum of fields.

Quantitative studying the formation kinetics and energetics of intermetallic nanoparticles

2019 Spring National Meeting

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