Which of the following is an example of a porous ceramic?

Calcium Hydroxyapatite is an example of a porous ceramic due to its composition and structure. Hydroxyapatite is a naturally occurring mineral form of calcium apatite with the chemical formula Ca10(PO4)6(OH)2 and is closely associated with bone structure. When processed to create a porous form, it retains its biocompatibility and osteoconductive properties, making it ideal for applications in bone tissue engineering. The porosity enables better cell infiltration and nutrient exchange, crucial for promoting bone growth and integration in biomedical implants.

In contrast, while alumina and zirconia can be utilized in biomedical contexts due to their mechanical properties and biocompatibility, they typically do not exhibit the same level of porosity as Hydroxyapatite when used in applications aimed at mimicking natural bone. Pyrolytic carbon, primarily known for its use in cardiovascular devices and scaffolding, does not fall under the category of porous ceramics and is instead a form of carbon with distinct properties that differentiate it from ceramic materials. Thus, Calcium Hydroxyapatite stands out as the most suitable example of a porous ceramic in this context.