Fig. 5

a Transmission electron microscope (TEM) image of mineral particle aggregates (scale bars 200 nm) and (b) the corresponding SAED patterns: (b1) particles enclosed in the circle indicate amorphous scattering of the diffusion ring. (b2) the marked rectangular area has poor crystalline diffraction, and (b3) the particles in the area shown in the interpolated image produced a clear crystalline diffraction pattern [(002) and second order (004) showing well defined reflections of apatite planes.] (b4) the encircled area taken after being stored at room temperature for a week. The appearance of diffraction spots with (002) plane (arrowheads) spacing suggests a transition to the crystalline HAp phase [85]. c Cryogenic-scanning electron microscope (Cryo-SEM) image of the same area (scale bar 100 nm). d The amorphous (encircled area) and crystalline (rectangular area) portions of the electron selective backscatter (ESB) image shows no significant difference in signal strength (scale bar 100 nm)