Structural Characterization of Nanocrystalline Ni_(50-x)Ti₅₀Cu_x(X = 5, 9 wt%) Alloys Produced by Mechanical Alloying

Nanocrystalline Ni(50-x)Ti50Cux(X = 5, 9 wt%) alloys were successfully produced by mechanical alloying. Mechanical activation was performed at different milling times under a high purity argon (99.998 vol%) atmosphere. Phase analysis and structural features of the samples were examined by X-ray diffraction (XRD). Results revealed that NiTiCu (B2) phase was achieved after 600 min of milling. The formation of this phase was mostly related to the critical factors in determining the site replacement of elements in Ni-Ti-Cu ternary system. After 600 min of milling, the average crystallite size and lattice strain of the samples were about 5 - 10 nm and 1.057% - 1.967%, respectively. Evaluation of the full width at half maximum (FWHM) values for all the samples indicated the occurrence of anisotropic line broadening. The determined amounts of crystallinity revealed that the fraction of crystalline phase decreased with increasing weight percentage of copper up to 9% and reached a minimum value after 600 min of milling. The lattice parameters and the unit cell volume of the milled samples were always larger than the standard values. In addition, lattice parameter deviation influenced by the weight percentage of copper. Based on the obtained data, mechanical alloying process can be used for production of nanocrystalline NiTiCu alloys with different structural features.

Structural insights of mechanically induced aluminum-doped hydroxyapatite nanoparticles by Rietveld refinement

Aluminum doped hydroxyapatite （HA：AI3 ＋） nanopowders were successfully prepared via a simple and efficient one-pot mechanochemical route. The effects of dopant loading on phase compositions and structural features were assessed by Rietveld analysis. The XRD-Rietveld refinement revealed the stabilization of HA in hexagonal structure for all the samples. The sharpness and intensity of the apatite-derived XRD peaks decreased as the dopant content increased to 10% due to the increase in lattice imperfections and mechanically induced amorphization. The incorpo- ration of A13 ＋ into the HA lattice decreased the unit cell parameters. From the FfiR measurements, the representing bands of apatite were identified in all cases. The mechanosynthesized nanopowders consisted of nanospheroids with an average size of 44 - 20 nm and therefore are promising for bone tissue regeneration.

Structural characterization and strengthening mechanism of forsterite nanostructured scaffolds synthesized by multistep sintering method

In this study, highly porous forsterite scaffolds with interconnected porosities were synthesized using multi-step sintering(MSS) method. The starting powder was nanosized forsterite, which was synthesized from talc and magnesium carbonate powders. The phase composition, average particle size and morphology of the produced forsterite powder were characterized by X-ray diffraction technique(XRD) and transition electron microscopy(TEM). Forsterite scaffolds were produced by foamy method using polymeric sponges. MSS process including three steps was used to efficiently sinter the forsterite nanopowders without destroying the initial porous structure of polymeric sponges. The results showed that MSS technique is an efficient and appropriate procedure to produce highly porous forsterite scaffolds with pore size in the range of 100-300 μm. The compressive strength, compressive modulus and porosity of C12 specimen(sintered at 1650℃ for 1 h with subsequent annealing at 1000℃ for 1000 min) was 1.88 MPa, 29.2 MPa, and 72.4%, respectively, which is very close to that of cancellous bone. The approach studied in this research can be developed for other nanostructure ceramics to produce highly porous scaffolds with interconnected porosities for load bearing applications.

Characterization of mechanothermal-synthesized hydroxyapatite-magnesium titanate composite nanopowders

Hydroxyapatite-magnesium titanate composite nanopowders have been developed using a mechanothermal process.Thermal treatment of the milled powders at 700℃resulted in the formation of HAp/MgTiO_(3)-MgO nanocomposite.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and energy dispersive X-ray spectroscopy(EDX)techniques were utilized to characterize the synthesized powders.The results revealed that the dominant phases after mechanical activation were hydroxyapatite,anatase(TiO_(2))and periclase(MgO);while after thermal annealing process at 700℃,hydroxyapatite along with geikielite(MgTiO_(3))and periclase(MgO)were the major phases.Based on the XRD analysis,the evaluation of structural features of the samples indicated that the average crystallite sizes of hydroxyapatite after 10 h of milling and subsequent thermal treatment at 700℃were about 21 nm and 34 nm,respectively.Microscopic observations illustrated that the synthesized powders contained large agglomerates which consisted of significantly finer particles with spheroidal morphology.It is concluded that the mechanothermal method can be used to produce hydroxyapatite-based nanocomposite with appropriate structural and morphological features.