Using a new and simple etching method to investigate the tablets of nacre, it is possible to observe a great deal of tablets in a large range. We found that most tablets have the same formal orientations after citric acid treatment. This phenomenon occurred not only in the same lamina but also along the direction perpendicular to nacreous plane. Based on the additional selected area diffraction patterns of transmission electron microscope, it is proposed that the formal orientations could indicate the crystal orientations of aragonite tablets.Statistical analyze shows that there is a main (type I tablets) and a secondary (type II tablets) preferred orientation with an angle of around 60 between them. Two possible modes of structural correspondence between protein sheets and aragonite lattice are assumed to interpret the orientation preference. On the other hand, the cluster character of type II tablets strongly supports that mineral bridges of the organic matrix have significant function in the crystal growth.At last, the mechanisms of structural correspondence and mineral bridges are combined to explain the formation process of nacreous layer in mussel.

The structure and crystallographic orientation of mineral phase in the oblique prismatic layer of Mytilus edulisshell were studied by SEM, XRD and TEM with selected area electron diffraction (SAED). A crystallographic orientation regulation, i.e. the adjacent 1-5 calcite prisms with the same three-dimensional orientation in the oblique prismatic layer, was found for the first time. It is observed that the calcite prisms in the oblique prismatic layer were grown with their (104) parallel to the shell surface.

The present paper demonstrated a biomimetic method to coat calcium phosphate (Ca-P) on the surface of titanium induced by NaOH-treatment from a simple supersaturated hydroxyapatite solution (SHS). The in#uence of pH value and calcium ions concentration on the precipitation process was investigated. It is necessary for the solution to be supersaturated than the critical concentration of octacalcium phosphate (OCP) to get Ca-P coatings on titanium surface. In the precipitating process, it seems that amorphous calcium phosphate (ACP) precipitated first, then OCP, and finally hydroxyapatite (HA). The system was in continuous evolution and the phase transitions occurred in sequence.

A biomimetic calcium phosphate coating is expected to enhance the bioactivity and bone inductivity of human implants. This study presents a very simple, highly effective biomimetic method to obtain a calcium phosphate coating on a titanium substrate. Using NaH2PO4, a stable solution was prepared with high calcium and phosphate ion concentrations. This solution turned to a supersaturated calcification solution (SCS) when NaHCO3 was added. The addition of NaHCO3 elevated the pH value of the solution gradually and steadily. A uniform coating approximately 40 mm thick was found on the substrates after 24 h immersion. The compositions of the coatings were adjustable from hydroxyapatite (HA) to HAydicalcium phosphate dihydrate (DCPD). The calcium phosphate deposits were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared (FT-IR) spectroscopy.

Ion-beam assisted deposition (IBAD) was carried out to deposit hydroxyapatite (HAp) on alumina substrate. The amorphous coating layer on alumina substrate is crystallized to the dense HAp after a post. treatment process of annealing at 500℃ for 2 h and immersion in deionized water for 72 h at room temperature. The homogeneous and dense HAp coating is observed by scanning electron microscopy and the thickness of the coating is measured to be about 638 um. The hardness of the coating 1ayer in the as-deposited and post-treated samples is 475 and 508, respectively. The adhesive strength between HAp and α-alumina substrate was measured by a scratch test. The ion-beam sputtered coatings were used as control samples, the adhesion was found to be worse for ion-beam sputtering deposition (IBSD) than for IBAD.