CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 9677–9681 Phase evolution and dynamics of cerium-doped mullite whiskers synthesized by sol–gel process Xiang Wang, Jin-hong Li n , Ling-xin Tong, Wu-wei Feng National Laboratory of Mineral Materials, China University of Geosciences, 100083 Beijing, China Received 16 April 2013; received in revised form 25 April 2013; accepted 23 May 2013 Available online 31 May 2013 Abstract The effects of CeO 2 doping of aluminosilicate on mullite formation and the morphology of mullite whiskers are evaluated herein. CeO 2 -doped mullite precursors were generated by a sol–gel process. The introduction of CeO 2 into the aluminosilicate precursor (3Al 2 O 3 Á 2SiO 2 ) not only lowered the mullite formation temperature, but also promoted the crystallization of mullite grains. The mullitization activation energies calculated based on non-isothermal differential scanning calorimetry (DSC) were 473 and 722 kJ mol -1 for the 2 mol% CeO 2 -doped and undoped samples, respectively. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: B. Whiskers; D. Mullite; D. CeO 2 ; Activity energy 1. Introduction Mullite is a non-stoichiometric compound with good mechanical strength, excellent thermal shock and high creep resistance, low thermal conductivity, and high temperature stability, features that have been exploited in a variety of applications and prompted intensive investigations over the last few decades [1,2]. The mullite grain exhibits a strong tendency towards anisotropic growth due to the anisotropic mullite structure. Mullite whiskers may be used to reinforce mullite ceramics, thus, techniques for fabrication of these whiskers are highly desired [3]. Thus far, sol–gel, co-precipitation, and spray pyrolysis have been utilized to synthesize mullite whiskers. Okada and Otsuka [4] synthesized mullite whiskers by firing a mixture of xerogel, silica gel, and aluminum fluoride in an airtight crucible at 900–1600 1C. Mullite whiskers grown from erbia-doped aluminum hydroxide-silica gel have been studied by Souza et al. [5] by firing 3 mol% erbia-doped pellets isostatically pressed at 1600 1C for 1–8 h. A high surface concentration of mullite whiskers was obtained, according to their report, with a maximum whisker length of 50 μm, and a maximum aspect ratio of 23. Investigation of the nucleation and growth of mullite whiskers from lanthanum-doped alumi- nosilicate melts by Regiani et al. [6] demonstrated that the mullitization temperature decreased from 1350 1C to 1240 1C in response to the rare earth dopant. However, the growth of mullite whiskers doped with rare earth oxide has been reported in several studies, with a consistently positive effect on the mullitization behavior, the phase evolution, and morphology of mullite whiskers after doping has been analyzed in only a few studies. Mechnich and co-workers [7] demonstrated the efficacy of the dopant CeO 2 for lowering the reaction temperature in a study of CeO 2 - doped reaction-bonded mullite. It was postulated that the formation of transient, low-viscosity Ce–Al–Si–O liquids accelerated Si oxidation and mullite formation. The present study aims to further illuminate the phase evolution and morphology of mullite whiskers formed from the CeO 2 -doped aluminosilicate precursor via the sol–gel process. 2. Materials and methods CeO 2 -doped mullite whiskers were prepared according to the synthesis scheme illustrated in Fig. 1. Aluminum nitrate www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.05.093 n Corresponding author. Tel.: +86 010 82323201; fax: +86 010 82322974. E-mail address: jinhong@cugb.edu.cn (J.-h. Li).