Preparation of Nano-Hydroxyapatite Coated Carbon Nanotube Reinforced Hydroxyapatite Composites

Xueni Zhao,Li Zhang,Yao Wang,Jiamei Zheng,Qingyao Liu,Xueyan Chen,Weigang Zhang

doi:10.3390/coatings8100357

Abstract

Uniform and dense nano-hydroxyapatite (nHA) coating with nanorod-shaped structure was fabricated on carbon nanotubes (CNTs) by combining electrodeposition with biomineralization. The CNTs with nHA coating (nHA–CNTs) were used as reinforcement to improve the mechanical properties of HA. Firstly, a mixed acid solution of nitric acid and sulfuric acid was used to treat CNTs (NS–CNTs). The dispersion of NS–CNTs was obviously improved, and O-containing functional groups were grafted on the surfaces of NS–CNTs by treatment. Then, calcium phosphate (CaP) was deposited on NS–CNTs by electrodeposition, and NS–CNTs were provided with numerous active nucleation sites for the next coating preparation process. Then nanorod-shaped HA crystals were obtained on the surfaces of NS–CNTs by biomineralization. Using the CNTs with nHA coating (nHA–CNTs) as reinforcement, HA-based composites reinforced with CNTs and nHA–CNTs (nHA–CNTs/HA) were fabricated by pressure-less process. Bending strength and fracture toughness of 1.0 wt % nHA–CNTs reinforced HA composites (HAnC1) reaches a maximum (30.77 MPa and 2.59 MPa), which increased by 26.94% and 7.02% compared with 1.0 wt % CNTs reinforced HA composites, respectively. Importantly, the fracture toughness of HAnC1 is within the range of that to compact bone. This work provides theoretical and practical guidance for preparing nHA coating on nanomaterials. It also contributes to the potential application of nHA–CNTs/HA composites for artificial bone implants.

Highlights

Hydroxyapatite (Ca10 (PO4)6 (OH)2, abbreviated as HA) is one of the bioceramics, that has received considerable attention over the past decades, due to its outstanding osteoconductivity and biocompatibility [1,2]
The application of pure HA is restricted in weight-bearing bones replacement materials, due to its low fracture toughness and poor bending strength [3,4]
The way to increase the mechanical properties of pure HA is to incorporate some reinforcement materials, such as zirconia [5], carbon fiber [6] and carbon nanotubes (CNTs) [7] etc

Summary

Introduction

Hydroxyapatite (Ca10 (PO4) (OH) , abbreviated as HA) is one of the bioceramics, that has received considerable attention over the past decades, due to its outstanding osteoconductivity and biocompatibility [1,2]. The application of pure HA is restricted in weight-bearing bones replacement materials, due to its low fracture toughness and poor bending strength [3,4]. The way to increase the mechanical properties of pure HA is to incorporate some reinforcement materials, such as zirconia [5], carbon fiber [6] and carbon nanotubes (CNTs) [7] etc. Among these reinforcing materials, CNTs have aroused intense interests in their potential biomedical applications owing to their outstanding mechanical properties and chemical stability [2,8,9,10]. The drawbacks of CNTs as reinforcing fillers are Coatings 2018, 8, 357; doi:10.3390/coatings8100357 www.mdpi.com/journal/coatings

Methods

Results

Conclusion