Cold spray of agglomerated submicronic hydroxyapatite powders for biomedical applications

摘要

Hydroxyapatite (HA) ceramic coatings are used for orthopaedic implants to favour bone growth. The main conventional process is plasma spray of pure HA powder. A solid state deposition process like cold spray of HA powder might have a great potential to achieve fully crystalline HA coatings. Moreover, HA by cold spray could also be envisaged favourably in case of thermosensitive polymeric biomaterials, which would otherwise be degraded by plasma spray. In this work, two agglomerated hydroxyapatite powders, respectively with and without heat treatment after agglomeration, were cold sprayed for various spraying parameters. The cold spray process of pure HA coatings has been implemented through single track on two different biocompatible substrates: a metallic substrate (Ti-6Al-4V) and a polymeric substrate (poly (vinyl alcohol) (PVA)). The structure of the agglomerated HA powders and the corresponding features of the HA coatings were observed by SEM. For both types of substrates, it was shown that the agglomerated submicronic hydroxyapatite powders could lead to a homogenous layers of submicronic HA grains. In the case of particles without heat treatment, thick layers could be obtained due to the binding action of residual by-products of the chemical synthesis of HA particles. It was also shown that one HA layer remained adherent after immersion in water, thus enabling the fabrication of ceramic coated hydrogels.