Effects of Titania Content and Sintering Temperature on Structural, Mechanical and Bioactive Behaviors of Titania Reinforced Hydroxyapatite Nanocomposites

Abstract

Hydroxyapatite (HA) is an attractive bioactive ceramic, which is a good candidate as implant material in clinical applications including bone spacers and fillers due to its biological and chemical similarity to the mineral composition of natural bone. [1][2][3][4][5][6] However, mechanical properties of low strength and high brittleness, which can lead to instability and unsatisfactory duration of the implant in the presence of body fluids and local loading, limit its application severely. Leading to the development of the biomaterial from monoliths to composites by controlling the volume fraction and distribution of the second phase in the composites, thus the properties of the composites can be tailored to meet the necessary mechanical and physiological requirements as an implant. One attractive way is to use bioactive HA as ceramic/ metal composites so as to achieve the necessary mechanical strength and bioactive properties at the same time, [7,8] which includes the addition of biocompatible glass into HA matrix. [9][10][11] Recently, researchers have proved that adhesive and cohesive strengths of the implants can be increased significantly by combining HA and TiO 2 as reinforcing additives, [12][13][14] and the addition of TiO 2 into HA has a major effect on the HA structure and a positive effect on the improvement of HA mechanical properties. Therefore, much attention has been given to the processing-microstructure-property relation of HA/TiO 2 composite biomaterials, but it is obvious that the addition of the different TiO 2 contents, different processing conditions and different preparing technique for the HA/TiO 2 composites can correspond to remarkably different microstructure, and hence, different properties and reinforcing mechanism.There are a variety of processing routes for preparing the HA/TiO 2 composite, such as sol-gel process, [15,16] electrochemical method, [17,18] thermal spray techniques, [19,20] etc. However, it is difficult to achieve a nanocomposite by abovementioned these methods. Considering that the use of nanoparticulate materials can attain more superior mechanical properties, [21] and nano-crystallized HA can promote osteoblast adhesion and proliferation as compared with conventionally crystallized HA, [22] as well as nano-sized HA can improve the sintering kinetics due to higher surface area. [23] The aim of the present study is to evaluate the effect of TiO 2 nanocrystal molar content and sintering temperature on the phase composition, microstructure, mechanical properties, and bioactive behaviors of the HA/TiO 2 nanocomposites obtained by a homogeneous mixing of nano-sized HA powders and nano-crystallized TiO 2 powders based on high-energy ball milling and spark plasma sintering (SPS) processes.Experimental HA powders were prepared by a wet chemical precipitation approach as reported in Refs. [24,25] and the powders with a particle size less than 20 lm, which are compose of nanoparticles in a needle-shape with a length of about 80-120 nm and a width of 20-30 nm, were used as HA m...

Effect of silica on porosity, strength, and toughness of pressureless sintered calcium phosphate–zirconia bioceramics

“…Furthermore, we observed the formation of Ca 2 ZrSi 4 O 12 for high silica content of 10 wt% and 20 wt% and both weight ratios of HAp:ZrO 2 . A possible reaction could be in accordance with equation (6).…”

“…To overcome this limitation, HAp can be combined with a reinforcing material to enable the fabrication of dense HAp scaffolds with oustanding properties. A number of oxide ceramics, including alumina [5], titania [6], zinc oxide [7], and zirconia [8][9][10], have been used as reinforcements for HAp. Among them, zirconia (ZrO 2 ) is particularly interesting due to its good chemical and dimensional stability, biocompatibility, and remarkable strength and fracture toughness [11].…”

Bioceramic-based composites reinforced with carbonaceous nanomaterials

“…However, binders are usually employed in these processes and need to be removed by an extra sintering step [120]. [131][132][133], titania [134,135], and zirconia [54,59,136,137]. Nanostructured reinforcements such as CNT and graphene particularly have been extensively used to reinforce HA by virtue of their prominent mechanical properties [49,138].…”