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Publication Title | Chemical Engineering Journal 173 (2011) 846–854 Contents lists available at ScienceDirect Chemical Engineering Journal

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Chemical Engineering Journal 173 (2011) 846–854

Contents lists available at ScienceDirect Chemical Engineering Journal

journal homepage: www.elsevier.com/locate/cej

Large scale synthesis of hydroxyapatite nanospheres by high gravity method A. Joseph Nathanaela,b, Sun Ig Hongb,∗, D. Mangalarajc,∗∗, Pao Chi Chend

a Department of Physics, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India

b Department of Nanomaterials Engineering, Chungnam National University, Daejeon 305-764, South Korea

c Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India

d Department of Chemical and Materials Engineering, Lunghwa University of Science and Technology, Taoyuan, Taiwan, ROC

article info

Article history:

Received 31 March 2011

Received in revised form 15 July 2011 Accepted 21 July 2011

Keywords:

Hydroxyapatite Nanoparticles

High gravity method TEM

Particle size

1. Introduction

Nano dimensional particles have attracted active attention in recent years due to their potential applications in various fields because of their unique properties. Since the properties of a certain material are dependent on the size and morphology, nanoparticles are expected to have properties that are different from those of the bulk states. A colloid-based wet chemical process has been widely used for synthesizing nanoparticles. Morphological modification of nanoparticles in solution by various methods is one of the recent advancement in the field of chemical synthesis. In order to obtain and exploit novel properties and high performances of nanoparti- cles, not only the small size, but also the uniform size distribution of nanoparticles should be achieved [1]. It is imperative to develop a reliable large scale fabrication method of nanoparticles with a high product quality for more wide-spread and general applications of high performance nanoparticles for human benefits.

Hydroxyapatite with the chemical formula Ca10(PO4)6(OH)2 is the major inorganic element of teeth and bone. Synthetic HAp is

∗ Corresponding author. Tel.: +82 42 821 6595; fax: +82 42 822 5850. ∗∗ Corresponding author. Tel.: +91 422 2425458; fax: +91 422 2425706. E-mail addresses: sihong@cnu.ac.kr (S.I. Hong), dmraj800@yahoo.com

(D. Mangalaraj).

1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2011.07.053

abstract

Hydroxyapatite (HAp) nanospheres were synthesized in large scale using high gravity method. The effects of flow rates (300, 500 and 700 mL/min) and rotating speeds (1000, 2000 and 3000 rpm) on the size, distribution and morphology of nanoparticles were studied. The liquid flow rate and rotation speed was found to have a great influence on the formation of nanoparticles and uniform size distribution. The particle size decreased with an increase in the rotation speed of the RPB. The particle size was observed to be smaller at a lower liquid flow rate compared to that of the high liquid flow rate. TEM images of the granular HAp nanoparticles clearly displayed the spherical shape of nanoparticles. Densely assembled arranged nanospheres with diameters of 20–40 nm were observed at various rpm values. The obtained nanospheres appeared to be single crystalline from the image and SAED pattern analyses. In vitro cellular analysis showed very good improvement in the cell adhesion. For mechanical analysis, HAp/HMWPE composite was fabricated. The smaller size of HAp particles provided a relatively homogenous mixture of HAp and HMWPE which ensured the good mechanical strength.

© 2011 Elsevier B.V. All rights reserved.

biocompatible with the human body and is widely used as a bio- material for bone tissue regeneration in medicine [2,3]. It is also a promising material for reinforcing filler for bio-composites [4]. Despite their favorable biological properties, the poor mechan- ical properties of HAp bioceramics have hindered their clinical applications. Hence a number of studies have been focused on the improvement of the mechanical properties of HAp [5]. It is shown that, mechanical properties of the ceramic materials could be improved remarkably by the formation of one dimensional (1-D) nanoscale building blocks such as nanorods, nanofibers and nan- otubes [6–8]. It has been reported that these nanostructured-HAp has unique properties such as enhanced biocompatibility, bioac- tivity and flexibility [9,10], which are essential to improve their applicability in biomedicine and biomaterials.

Different morphologies of HAp particles like nanorods [11], nanoparticles [12], plate-like crystals [13] have been synthesized by various synthesis method such as wet chemical process [14], sol–gel process [15], emulsion process [15], chemical precipita- tion approach [16], hydrothermal reaction [17], sol–gel synthesis [18–20] and mechano-chemical synthesis [21]. Among these pro- cesses, wet chemical process has been extensively used since it is simple and the morphology of the nanoparticles can be modified by controlling reaction parameters [14,22,23].

Due to its tendency of agglomeration, synthesis of HAp nanopar- ticles in large scale is a challenging task. In this work we report the

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