Sol–gel auto-combustion synthesis of totally immiscible NiAg alloy

Immiscible crystalline NiAg alloy was successfully synthesized by the newly developed sol–gel auto-combustion method. The structure and composition were examined by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). All evidence supports that homogeneous NiAg alloy with FCC structure was synthesized. The differential thermal analysis and thermogravimetry (DTA–TG) measurement shows that the alloy has a good thermal stability until 315 °C. Unusually some extinction planes are observed in the XRD pattern and HRTEM images. The random distribution of atoms and the large difference between Ni and Ag atom form factors should be regarded as the main reasons for the observation of the extinction planes. The quenching like nonequilibrium thermal process in the combustion is taken as the key factor in the synthesis of immiscible alloy. And the addition of ethylene glycol in the precursors is found to benefit the formation of NiAg alloy.

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► Chemically synthesized immiscible NiAg alloy nanoparticles without protecting matrix.
► A chemical method providing both a nonequilibrium thermal process and a good mixing of precursors.
► Observation of extinction planes in NiAg alloy.