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Structural evolution during the synthesis of B2-NiAl intermetallic compound by mechanical alloying of equiatomic elemental mixtures was studied by Rietveld analysis, DSC and HTXRD. The lattice parameter, crystallite size, microstrain, amount of phase and ordering of the B2 phase were monitored as a function of milling time. Formation of the B2-NiAl phase shows a sigmoidal behavior, which suggests that Johnson-Mehl-Avrami nucleation and interface-controlled growth are the responsible mechanisms in the transformation. Almost complete transformation (~ 97 mol%) was obtained after 25 h of milling. A specific phase transformation sequence during milling was not absolutely determined, however, the sequence Ni + Al → NiAl → NiAl → B2-NiAl was identified by HTXRD. This sequence was confirmed by DSC. The transformation temperature of the B2-NiAl phase and the presence of additional intermetallic compounds show a direct dependence on the Ni-Al layer spacing. Using a production-scale Simoloyer horizontal Attritor Mill, the presence of NiAl phase was observed prior to the full synthesis of B2-NiAl. [ABSTRACT FROM AUTHOR]

This work presents silicon-substituted hydroxyapatite preparation through planetary ball milling using biogenic hydroxyapatite and different wt% of S53P4 bioactive glass (5, 10, 15, and 20 wt%) sources for the first time. The prepared mixtures showed a BHAp lattice contraction with SiO 4 4− incorporation; rich- and poor-Si phases were subsequently identified. Furthermore, two types of interaction among the functional groups in the S53P4 and BHAp mixtures are proposed. First, the 95-5 (wt.%) sample displayed a BHAp lattice with SiO 4 4−, CO 3 2−, and OH− ions substitution. In samples with S53P4 BG content higher than 95-5, the lattice substitution was related to SiO 4 4−, PO 4 3−, and CO 3 2− ions, and a dehydroxylation process occurred in the BHAp. Finally, the bioactive behavior of the samples was studied by immersion in Hank's solution for 7, 14, and 28 days. The results showed that the mixtures formed a bone-like apatite layer with a dune-like morphology that increased in size and quantity with increasing S53P4 content in the mixtures. [Display omitted] • S53P4/BHAp mixtures preparation through high energy milling. • Si-substituted HAp preparation through a mechanical process. • SiO 4 4− occupying PO 4 3− and CO 3 2− sites within the BHAp lattice by milling process. • Substitution of SiO 4 4− for PO 4 3− and CO 3 2− in the BHAp lattice by mechanical energy. • Enhanced bioactive behavior with increasing S53P4 content in BHAp/BG mixtures. [ABSTRACT FROM AUTHOR]