A study of hydroxyapatite fibers prepared via sol–gel route Sutapa Roy Ramanan * , Ramanan Venkatesh School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Pulau Pinang, Malaysia Received 14 May 2004; received in revised form 16 June 2004; accepted 30 June 2004 Available online 25 July 2004 Abstract Hydroxyapatite (HAP) fibers were prepared by spinning sols prepared from a 2-butanol solution of phosphorous pentoxide and calcium acetate solution in distill water. Lactic acid was added as a spinning aid. The Ca/P ratio was maintained at 1.67. The fibers obtained were dried and calcined at different temperatures up to 1000 8C. X-ray diffraction studies showed the presence of pure HAP phases up to a calcinations temperature of 1000 8C. The fibers showed the presence of the FTIR signature peaks of HAP and had uniform diameter and dense microstructure. D 2004 Elsevier B.V. All rights reserved. Keywords: Sol–Gel; HAP; Fibers 1. Introduction The bioceramic hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , com- monly referred to as HAP, is one of the calcium phosphate based bioceramic material that has attracted widespread interest from both orthopaedic and dental fields due to its excellent biocompatibility and bioactivity coming from the analogy to the mineral components of natural bones [1–5]. There are several calcium phosphate ceramics that are considered biocompatible. Of these, most are resorbable and will dissolve when exposed to physiological environments. Some of these materials include, in order of solubility: Tetracalcium Phosphate (Ca 4 P 2 O 9 )NAmorphous calcium PhosphateNalpha-Tricalcium Phosphate (Ca 3 (PO 4 ) 2 )Nbeta- Tricalcium Phosphate (Ca 3 (PO 4 ) 2)NNHydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ). Unlike the other calcium phosphates, hydroxyapatite does not break down under physiological conditions. In fact, it is thermodynamically stable at physiological pH and actively takes part in bone bonding, forming strong chemical bonds with surrounding bone. This property has been exploited for rapid bone repair after major trauma or surgery. Because the bone and soft tissue growth into the pores of the implant occurs quickly after the implantation, the implant is held in place. Over time the implant is partially resorbed and replaced by natural bone. Tremendous amount of research has been focused on HAP and related materials, as it is the most appropriate ceramic material for artificial bones [6–11]. Extensive researches have been carried out to prepare HAP in powder form [12–19], thin films [1,20–23] and by using gel-casting techniques to obtain pieces with complex shapes [24–26]. While its mechanical properties have been found to be unsuitable for load-bearing applications such as orthopae- dics, it is used as a coating on materials such as titanium and titanium alloys, where it can contribute its dbioactiveT properties, while the metallic component bears the load. Such coatings are applied by plasma spraying. However, careful control of processing parameters is necessary to prevent thermal decomposition of hydroxyapatite into other soluble calcium phosphates due to the high processing temperatures. The wet chemical methods of preparation also often result in low thermal stability leading to partial decomposition into a- and h-tricalcium phosphate phase, which is highly bioresorbable. h-TCP existing in HAP material in low content is helpful for the rapid bonding of the artificial bones to natural ones via rapid dissolution. 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2004.06.030 * Corresponding author. Tel.: +60 125566584; fax: +60 45941011. E-mail address: sutapa@eng.usm.my (S.R. Ramanan). Materials Letters 58 (2004) 3320 – 3323 www.elsevier.com/locate/matlet