Thermal behavior of biogenic apatite crystals in bone: An X-ray diffraction study

Abstract

The thermal behavior of the bovine bone mineral and synthetic stoichiometric hydroxyapatite was investigated by X-ray diffraction. The bone samples in solid (planar oriented pieces) and in powder form were examined to elucidate how the microstructural and textural properties of bone mineral are modified under heating. As could be expected, the thermal behavior of the bone mineral depends not only on the structural distortions, but also on the crystal habit, texture and ordering of biocrystals in tissue. The temperature growth of biogenic apatite crystals, unlike synthetic hydroxyapatite, is seen to be nonmonotonic and multi-staged. At 600 to 700°C the biomineral crystallites grow rapidly due to disappearance of the mosaic structure as the lattice imperfections are annealed. After heating between 700°C and 900°C the bone mineral appears to be composed of roughly equidimensional ≥200 nm crystals. The further growth of the crystals in the range from 900 to 1300°C occurs by the mass transport mechanism, supporting the idea that the bone mineral is not a discrete aggregation of crystals, but rather a continuous mineral phase with direct crystal-crystal bonding. Estimates are presented to show the important role of the surface mass transport mechanism in the growth of apatite crystals. The material obtained by heating a cortical bone fragment between 900°C and 1300°C turns out to be composed of two crystal types: crystals oriented along the bone axis (major morphology) and those of differing shape and orientation (minor morphology). The heating-induced variations in the longitudinal and transverse dimensions of differing-morphology crystals are found to be coherent. Small amounts of CaO, MgO and other crystalline phases are seen to be formed in the bone mineral under heating.

Rapid biomimetic mineralization of chitosan scaffolds with a precursor sacrificed method in ethanol/water mixed solution

“…The Bragg peaks observed approximately at 26, 28, 29, 30-35, 39, 46, 49, and 50º (2!) correspond to the pure phase HAP [20], as the bar graph shows in the bottom of Figure 1. Figure 1a demonstrates that the apatite formed in the suspension was HAP but with poor crystallinity.…”

Some features of thermo‐activated structural transformation of biogenic and synthetic Mg‐containing apatite with β‐tricalcium‐magnesium phosphate formation

“…The details of the apparatus are described in earlier publications [18,19]. The specimens were first scanned in continuous mode over the range of diffraction angles (2ϑ) from 10 to 60 ° and then in stepwise mode (step size of 0.01°…”

Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure, hardness, and elemental composition

“…Upon the transition of nitride coatings to the nanostructured state there is a significant improvement in their physicomechanical and tribological properties [5], an increase in resistance to thermal impacts [6][7][8][9], improvement of corrosion resistance [10][11][12][13][14], etc. One method to realize the transition of coatings to the nanostructured state is the deposition of multilayer composite materials [15][16][17], in which the alternation of layers from different components [14,18] serves as a good diffusion barrier [19] and provides an increase in stability under external influences [20].…”