Synthesis and characterization of nanocrystalline merwinite (Ca 3 Mg(SiO 4 ) 2 ) via sol–gel method Masoud Hafezi-Ardakani a , Fatollah Moztarzadeh a, * , Mohammad Rabiee a , Ali Reza Talebi b a Biomaterials Group, Faculty of Biomedical Engineering (Centerof Excellence), Amirkabir University of Technology, Tehran, Iran b Research and Clinical Center for Infertility, Department of Anatomy, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Received 7 May 2010; received in revised form 18 May 2010; accepted 10 August 2010 Available online 25 September 2010 Abstract In this research, the synthesis of nanocrystalline merwinite (2SiO 2 –3CaO–MgO) bioactive ceramic was carried out by the sol–gel method. After crushing, obtained sol–gel derived bioceramic powder pressed uniaxially to produce cylindrical-like pellets, followed by sintering at 1300 8C. Via immersion in simulated body fluid (SBF) for various time intervals, the formation of apatite was characterized. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FT-IR) studies were conducted both before and after immersion in SBF. The crystallization temperature of the merwinite was determined by thermal analysis. Attained results confirmed formation of apatite layer within the first day of soaking. Accordingly it can be concluded that merwinite is bioactive and might be used for preparation of implantable biomaterials. # 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Merwinite; Synthesis; Sol–gel; Bioactivity; Hydroxyapatite 1. Introduction Bone defects are among the most significant worldwide health problem [1,2]. Reconstructions of impaired and defective bone tissue are the part of modern medical practice [3]. Due to several reasons (e.g. immune rejection and limited blood supply) the success rate of traditional repair strategies is low [3]. Following by bioglass introduced by Hench [4,5], numerous bioactive materials showing good surface hydroxyapatite (HA) formation ability have been synthesized [6]. To create nucleation site for HA formation, the simultaneous dissolution of silicates and ensuing formation of Si–OH groups is necessary [7–15]. Most common bioactive materials comprising CaO and SiO 2 follow this mechanism for HA formation on their surfaces. Amorphous phase materials release more Ca ions than crystalline materials which makes them more capable of HA formation [16,17]. Researches have reported excellent bioactivity of some calcium silicate ceramics, such as wollastonite (low temperature, triclinic CaSiO 3 ) [18,19], pseudowollastonite (high temperature, mono- clinic CaSiO 3 ) [20–24], diopside (CaMgSi 2 O 6 ) [25–27], tricalcium silicate (Ca 3 SiO 5 ) [28], combeite (Na 2 Ca 2 Si 3 O 9 ) [29] and akermanite (Ca 2 MgSi 2 O 7 ) [30–32]. Merwinite, (Ca 3 MgSi 2 O 8 ), an orthosilicate, known as a blast furnace slag in cement industries was first described by Larsen and Foshag [33]. The use of merwinite ceramics, which has melting temperature about 1450 8C, as a biomaterial has not been reported until recently [34]. In 2008 merwinite was suggested as a bioceramic with suitable mechanical properties which hold the potential for use as bioactive material for bone repair [34]. The purpose of the present study is to explore the formation of nanocrystalline merwinite via sol–gel method. Subsequently, the effect of temperature on the formation of merwinite was evaluated by XRD analysis. Finally, the ability of merwinite ceramic to deposit apatite on its surface in SBF solution was assessed by XRD, FTIR and SEM techniques. 2. Experimental 2.1. Materials and methods Nanocrystalline merwinite powders were synthesized using the sol–gel method. For this purpose, Ca(NO 3 ) 2 4H 2 O (Merck), www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 37 (2011) 175–180 * Corresponding author. Tel.: +98 21 64542393; fax: +98 21 64542387. E-mail addresses: moztarzadeh@aut.ac.ir (F. Moztarzadeh), mrabiee@aut.ac.ir (M. Rabiee). 0272-8842/$36.00 # 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2010.08.034