Why Even Difficult to Avoid Nanostructures in Chemically Bonded Bioceramics?

This question can be returned by a bold statement: It is even difficult to avoid nanostructures in chemically bonded bioceramics (CBBCs). It is very interesting that Professor Powers [1] as early as 1946 proposed ordinary Portland cement (OPC) (mainly a Ca-silicate system) to have a nanostructure. On the basis of Brunauer-EmmettTeller (BET) (specific surface area measurement of dried, fully hydrated cement) Powers estimated the crystals to have an average diameter of approximately 14 nm. He was sorry the resolution of microscopes at that time was too low to see nanocrystals. Approximately 50 years later the nanocrystal size of hydrated Casilicates was confirmed by high-resolution transmission electron microscopy (HRTEM) [2].