Hf metal powder synthesis via a chemically activated combustion-reduction process

The present study demonstrates the synthesis of fine hafnium (Hf) metal powders via a chemically activated combustion synthesis (CS) approach, which develops temperatures in the range of 1000–1600 °C. The current CS approach can be employed to obtain Hf powders with a single-crystalline hexagonal close-packed (hcp) structure in addition to high compositional uniformity and average particle sizes ranging from 0.05 to 2.0 μm. The mechanism of Hf particle formation can be understood by analyzing the process thermodynamics, including adiabatic temperatures and equilibrium reaction phases. In addition, analytical methods, including X-ray diffraction, SEM/TEM BET, FTIR, and oxygen analysis, were employed to characterize the synthesized Hf powders. Theoretical analysis was also conducted to predict the oxygen content according to Hf particle size. To the author's best knowledge, this work is the first known report demonstrating the preparation of hafnium micro- and nanopowders by the combustion synthesis method.