In-situ preparation of nitrogen-doped porous hydroxyapatite bioceramic with high carbonate content using nitrocellulose self-propagating sintering

Abstract

Nitrocellulose (NC) has important applications in both military and civilian fields. However, due to expiration dates, declining quality, etc., more than 100,000 tons of NC are disposed of per year, mostly by incineration, which is a great waste of resources. In this paper, using NC's characteristics of self-sustaining combustion, high gas yield and no residue, a nitrogen-doped porous hydroxyapatite bioceramic with high carbonate content (NPC-HA) was prepared in situ by a self-propagating sintering method. The C content of NPC-HA reaches 6%, and the N content is 0.34%. After treatment at the optimal temperature of 1000 °C, NPC-HA maintains the basic morphology of hydroxyapatite (HA) needle-like particles. Moreover, these particles are fused, forming a nest-like pore structure that disperses stress, producing a significant increase in compressivestrength. CCK-8 results show that NPC-HA has excellent biocompatibility due to nitrogen doping, high carbonate content and abundant pore structures. The method not only effectively utilizes NC industrial waste but also significantly reduces the sintering temperature of HA ceramics from the usual 1200 °C to 1000 °C. Therefore, it is a green preparation technology for porous HA bioceramics with considerable promise for wide industrial use.