Renlong Xin

Characterization and structural analysis of zinc-substituted hydroxyapatites

The substitution of Zn in hydroxyapatite (HA) crystals was examined via comprehensive characterization techniques. Nanosized HA crystals were synthesized by the wet chemical method in aqueous solutions including various amounts of Zn ions. X-ray fluorescent spectroscopy was used to examine the amount of Zn in the HA precipitates. Scanning electron microscopy and high-resolution transmission electron microscopy were employed to examine the effects of Zn on the morphology and crystal size of the precipitates. Conventional powder X-ray diffraction and the Rietveld refinement method revealed the apatite lattice parameters and phase changes with the inclusion of Zn. The results indicated that Zn ions partially substituted for Ca ions in the apatite structure. They were not simply adsorbed on the apatite surface or in the amorphous phase. The precipitates maintained the apatite phase up to a Zn:(Zn+Ca) ratio of 15-20 mol.% in the solution. Pure HA was well crystallized and the crystals had regular shapes, whereas the Zn-substituted apatite crystals became irregular and formed agglomerates. The lattice parameters, a and c, decreased at a Zn:(Zn+Ca) ratio of 10 mol.%.

Synthesis, characterization and ab initio simulation of magnesium-substituted hydroxyapatite

The substitution of magnesium in hydroxyapatite (HA) was examined in HA nano-crystals synthesized by the wet-chemical precipitation method at 90 degrees C. Comprehensive characterization techniques, including X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis and Rietveld refinement, provided experimental evidence of the effects of Mg substitution on the phase, crystallinity, chemical composition, crystal size, morphology, thermal stability and crystal lattice structure of HA. A computational study using ab initio generalized gradient approximation density functional theory was performed to reveal changes in lattice parameters and preferential calcium sites for Mg substitution in HA. The experimental results showed that a limited amount of Mg (Mg/(Mg+Ca) between 5 and 7 mol.%) could successfully substitute for Ca in HA. HA crystallites became smaller and more irregular, and they formed greater agglomerates with Mg substitution. Mg substitution resulted in decreases in the crystallinity and thermal stability of HA. The lattice constants, a and c, decreased with increasing Mg substitution. The simulation results revealed that the Ca(1) sites in HA lattices were energetically favored sites for Mg substitution.

Correlation Between Texture Variation and Transverse Tensile Behavior of Friction-Stir-Processed AZ31 Mg Alloy

The microstructure and especially the texture of a friction-stir-processed AZ31 Mg alloy were comprehensively characterized by the electron backscatter diffraction (EBSD) technique. Local texture changed significantly from the base material (BM) to the stir zone (SZ) center. The SZ center exhibited strong basal texture with the

Surface functionalized mesoporous silica nanoparticles with natural proteins for reduced immunotoxicity.

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Chemical Stability of ZnO Nanostructures in Simulated Physiological Environments and Its Application in Determining Polar Directions

direction parallel to the processing direction (PD), while the

Bioactive films on metallic surfaces for osteoconduction

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