Nanocrystalline HfN produced by mechanical milling: Kinetic aspects

• Published in: Acta materialia Vol. 49; no. 20; pp. 4205 - 4213
• Main Authors: Bab, M.A, Mendoza-Zélis, L, Damonte, L.C
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 03-12-2001; Elsevier Science
• Subjects: Ceramics; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Kinetics; Materials science; Mechanical alloying; Nanoscale materials and structures: fabrication and characterization; Physics; Probe methods; X-Ray diffraction (XRD); X-Ray diffraction (XRD); Ceramics; Kinetics; Probe methods; Mechanical alloying; Hafnium nitrides; Pressure effects; Gas solid reaction; Nitridation; Powder grinding; XRD; Nanostructures; Experimental study; Nanostructured materials
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(01)00309-3

Nanocrystalline HfN powders were obtained by mechanically assisted gas–solid reaction. An analysis of the reaction kinetics under different milling frequencies and gas pressure is presented. The results shown the formation of an interstitial solid solution
α-Hf, prior to its transformation to cubic HfN. Rietveld refinements of the X-ray diffraction data were done in order to analyze the progress of the structural change. The short range order was characterized by perturbed angular correlations, which indicated a random distribution of N around Hf. The reaction kinetics were obtained from the measured value of absorbed nitrogen per Hf (
n). Two main features were evident: the reaction advance dependence on the dose of mechanical energy and a slowing down in the reaction kinetics for
n∼0.5 associated with the saturation of surface sites. These findings are discussed taking into account the structural change and the role of surface adsorption and volume diffusion.