Figure 3. SEM micrographs of as-received and heat-treated cortical bones from distal to proximal parts of a bovine femur.

More polymers present in as-received and low temperature samples and more porosity observed at high temperature proximal part. For A–U, each row consists of same heat-treatment and same colour and three different columns from left to right represent distal, middle and proximal parts of a femur. [A, B, C] as-received: Blue accent. Heat-treated at [D, E, F] 120°C: Olive green; [G, H, I] 350°C: Sepia gray; [J, K, L] 500°C: Red accent; [M, N, O] 750°C: Aqua accent; [P, Q, R] 900°C: Purple; [S, T, U] D1000°C: Orange accent. Yellow arrow indicates inorganic matrix or particles, White arrow indicates collagen fibrils, and Green arrow indicates impression left in the sample after removing the polymeric fibrils or fibers. [V] A schematic change in morphology of as-received and heat-treated FBCBs at different temperatures from 120°C to 1000°C – with temperatures, the fibrous polymers gradually decrease and tiny equiaxed inorganic particles convert into hexagonal HA and become large round shaped grains. Three equivalent parts (distal, middle and proximal) of the diaphysis shaft in a bovine femur are also schematically indicated. Growth mechanisms or steps for HA formation and diffusion phenomena of the bovine-apatite are different at different temperatures.