Figure 4. Micro-Raman spectroscopy on substrates cut perpendicular to the extrusion axis: (a) as polished; (b) after immersion in CaP-sol containing 0.4 mg/mL rH174; and (c) after immersion in CaP-sol containing 1.6 mg/mL rH174, revealing a sharp peak at 963 cm^–1, and smaller peaks at 705 and 1340 cm^–1 (small arrows) and around 1450 and 1670 cm^–1 (large arrows).