Preparation of the Ferromagnetic Intermetallic Compound Ni3Fe by Solution Combustion Synthesis

The intermetallic compound Ni₃Fe was obtained using the solution combustion synthesis (SCS) method, based on heating an aqueous solution containing nitrates of the corresponding metals and hexamethylenetetramine (HMTA) in a nitrogen atmosphere. The limits for the implementation of a self-propagating reaction in the metal nitrates-HMTA system were determined depending on the amount of HMTA in the reacting mixture (n). It has been established that by changing the value of n it is possible to control phase composition and microstructure of the obtained SCS products. The X-ray examinations have shown that at n = 6, a single-phase target product Ni₃Fe is obtained, and electron microscopic studies indicated that the product is characterized by a pronounced porous structure because of abundant gas evolution during the SCS process. Based on thermogravimetric analyses of the individual compounds and the mixture of reagents (iron and nickel nitrates with HMTA), a possible mechanism for forming the target Ni₃Fe intermetallic compound is discussed. The magnetic characteristics of the synthesized substance have been studied.