Medical implants are being used in every organ of the human body. The system and product specifications for these devices included the user requirements in terms of functionality, location and physical constraints. They all require biocompatible coating material(s) that must remain stable for the lifetime of the implant, which in many cases can be the lifetime of a person. Currently so-called biomaterials are chosen because they are reasonably successful at hiding from the body's immune system, and are consequently not rejected. All the same, within a month of implanting them, the body isolates implants by wrapping them in a collagenous, avascular sac. Materials are considered to be 'biocompatible' if this sac is not too thick and are made with specifically sized pores that encourage small blood vessels to actively grow through the implant, or implants coated with DNA that specifically prevents formation of the collagenous capsule.Both of these allow the implant and the body actively work together, rather than simply try to prevent them fighting against each other. Current medical implants, such as orthopaedic implants and heart valves, are made of titanium and stainless steel alloys, primarily because they are biocompatible The implant material market has evolved over the years starting from vanadium steel and PTFE to the usage of shape memory alloys and resorbabales. Unfortunately, in some cases these metal alloys may wear out within the lifetime of the patient. At present there is no material which can be categorized as above but continuous research is done to improve the properties of the materials. Metallic Materials, Polymeric Materials and Ceramic Materials are used.Nanocrystalline zirconium oxide (zirconia) is hard, wearresistant, bio-corrosion resistant and bio-compatible. It therefore presents an attractive alternative material for implants. This and other nanoceramics can also be made as strong, light aerogels by sol–gel techniques. Nanocrystalline silicon carbide is another candidate material for artificial heart valves primarily because of its low weight, high strength and inertness.