Mechanical properties, microstructure and histocompatibility of MWCNTs/HAp biocomposites

doi:10.1016/j.matlet.2006.07.159

Materials Letters

Volume 61, Issues 8–9, April 2007, Pages 1839-1844

https://doi.org/10.1016/j.matlet.2006.07.159 Get rights and content

Abstract

In this paper, the authors mainly investigated the mechanical properties, microstructure and histocompatibility of multi-wall carbon nanotubes/hydroxyapatite (MWCNTs/HAp) composite prepared by two techniques. Compared with pure hydroxyapatite, the bending strength and fracture toughness of the composite are all improved, especially the latter whose increment exceeded 200%. XRD shows that the primary crystal phase of the composite is HAp together with the diffraction peaks of carbon nanotube. By SEM we found that there are more carbon nanotubes in the composite sintered in Ar, but there are much pores in it and the interface between the carbon nanotube and hydroxyapatite is not very strong. In vacuum, the diameter of carbon nanotube became larger (reported before) than that in Ar, but the interface between MWCNTs and HAp is very strong and there are less pores in the composite. From a pathologic micrograph we can draw conclusions as follows. When MWCNTs/HAp composite was embedded into the striated muscle of a big white mouse it produced a little stimulation to the tissue around it and there was no serious inflammation reaction, implying better histocompatibility. Both MWCNTs/HAp and ZrO₂/HAp composites can satisfy the condition of biomaterials but the histocompatibility of the former is much better than the latter.

Introduction

Carbon nanotubes (CNTs) are new-style materials which were developed for the last ten years. Carbon nanotubes were studied widely from the first radix carbon nanotube produced in 1991 [1], [2], [3], [4]. The mechanical property of CNTs is very high. Its tensile strength is one hundred times higher than that of steel and its density is six to seven times lower as that of steel [5]. It can resist the erosion of strong acid and alkali and it cannot be oxided by oxygen when the temperature is lower than 973 K in air. It has a high aspect ratio, better electric property, definite magnetism and nanometer effect which belong to a one-dimensional nanostructure [6], [7], [8]. Thus, if we prepare the composite with CNTs and other engineering materials CNTs can strengthen and toughen the matrix. If the special nanometer of CNTs effect was utilized some functional material can be obtained. The theoretical study has shown that it is viable to fabricate composite with superhigh mechanical property by CNTs. The study of CNTs composite has become one of the most interesting research topics. The composite with CNTs such as CNTs/metal [9], CNTs/ceramic [10] and CNTs/polymer [11], [12], [13] has been prepared, but a few studies about CNTs/ceramic composite and its security have been reported. Hydroxyapatite (HAp) is one of the bioceramics with higher bioactivity, but it has lower mechanical property than human load-bearing bone and its low dependability needs to be strengthened and toughened. If CNTs and HAp were compounded we may obtain a composite with higher mechanical property, better biocompatibility and even definite magnetism and wave-absorbing properties. Thus, it is of importance and of application value to fabricate the composite and study its mechanical property, microstructure and biocompatibility. For comparison, a parallel study of ZrO₂/HAp composite was carried out at the same time in order to determine the histocompatibility of both composites.

Section snippets

Raw materials

We adopt the chemical precipitation method to prepare HAp powder, and the materials and preparation method were discussed in detail before [14]. Multi-wall carbon nanotube: Shenzhen Nanotech Port Company, Limited, and its parameters are as follows: diameter: 40–60 nm; length: 0.5–500 μm; purity: 95%; agraphitic carbon: < 3%; ash: ≤ 0.2 wt.%.

Preparation and dispersion of the composite powder, molding, sintering and post processing of the composites

Firstly, we used the chemical precipitation method to prepare the HAp powder. Secondly, we use the method of ultrasonic vibration to prepare the composite

The mechanical properties of MWCNTs/HAp biocomposite

Table 1 shows the mechanical properties of MWCNTs/HAp composites. From the table we can see that the bending strength and fracture toughness of MWCNTs/HAp composites are all higher than pure hydroxyapatite and the increased quantum all exceeded 100%. The fracture toughness of MWCNTs/HAp composite sintered in Ar increases by 100% and in vacuum increases by 200% compared with pure hydroxyapatite. This expressed that CNTs can strengthen and toughen hydroxyapatite. At the same time, the atmosphere

Histocompatibility of MWCNTs/HAp biocomposite

Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 are the histological pictures of MWCNTs/HAp and ZrO₂/HAp composite after the composites were embedded into the striped muscle for one, three, five, seven and fourteen days.

Fig. 3 is the histological pictures of MWCNTs/HAp and ZrO₂/HAp composites when they were embedded into the striped muscle for one day. Fig. 3(a) illustrates that there is little inflammatory cell and lymphocyte infiltration in the tissue around the sample and mesenchymal mild dilation

Conclusions

The bending strength and fracture toughness of MWCNTs/HAp composite sintered in vacuum or Ar together with heat treatment are both higher than those of pure hydroxyapatite. The increment of the fracture toughness is most obvious and its maximum value reaches up to 2.4 MPa m^1/2, which is about eight times higher than pure HAp. MWCNTs can be preserved integrally in their original shape in Ar, but the interface junction between MWCNTs and HAp is loose and there are large numbers of pores in the

Acknowledgments

This work was supported by the Natural Science Council (30540061) and “863” plan (2003AA302232) Republic of China.

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Citation Excerpt :
Several papers reported that mechanical strength and fracture toughness of the bioceramics can be enhanced by the addition of CNTs in last the decade [9–14]. Zhao et al. reported that 2 wt% addition of CNTs to HA matrix, improved compressive strength 62% [36] and Li et al. found that 2 wt% addition of CNTs enhanced fracture toughness and flexural strength 226% and 46%, respectively [37]. But, Kealey et al. indicated that 2 wt% addition of CNTs decreased hardness of HA/CNTs composite and fracture did not change [38].
Porous hydroxyapatite (HA)/carbon nanotubes (CNTs) composites were produced by using polymeric sponge route through double firing method (500 °C for 0.5 h and 1000 °C for 1 h). HA nano crystals were synthesized by the hydrothermal method at 200 °C for 2 h and mixed with aqueous CNTs suspension. For the functionalization of CNTs, acidic treatment was used. Polyvinyl Alcohol (PVA) was used as a binder for the formation process of HA/CNTs composite ceramics. Addition of CNTs can enhance its mechanical, biological and filtration performance of the porous HA/CNTs composite ceramics. The novelty of this paper relies on the fabrication of the HA/CNTs composites have been accomplished with tailored pore structure. The research shows that developed new technique is able to design and control pore structure of ceramic/CNTs composite for potential use in biomedical and environmental applications.

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Mechanical properties, microstructure and histocompatibility of MWCNTs/HAp biocomposites

Abstract

Introduction

Section snippets

Raw materials

Preparation and dispersion of the composite powder, molding, sintering and post processing of the composites

The mechanical properties of MWCNTs/HAp biocomposite

Histocompatibility of MWCNTs/HAp biocomposite

Conclusions

Acknowledgments

Physica, B

Chemical Physics

Journal of the European Ceramic Society

Ceramics International

Polymer

Journal of Shaoyang College

New Carbon Material