Available online at www.sciencedirect.com Journal of the European Ceramic Society 33 (2013) 2767–2774 MgAl 2 O 4 spinel as an effective ceramic bonding in a MgO–CaZrO 3 refractory Edén A. Rodríguez a,∗ , G.-Alan Castillo a , Tushar K. Das a , R. Puente-Ornelas a , Yadira González a , Ana-María Arato a , J.A. Aguilar-Martínez b a Universidad Autónoma de Nuevo León, Av. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza, Nuevo León, C.P. 66451, Mexico b Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Alianza Norte No. 202, Parque de Investigación e Innovación Tecnológica (PIIT), Nueva carr. Aeropuerto Km. 10, Apodaca N.L. 66600, Mexico Received 13 December 2012; received in revised form 22 April 2013; accepted 25 April 2013 Available online 7 June 2013 Abstract The influence of MgAl 2 O 4 spinel addition as a ceramic bonding in the MgO–CaZrO 3 refractory was established by the evaluation of physical and microstructural characteristics in terms of density, porosity, crystalline phases, phase distribution and morphology. X-ray diffraction analyses and scanning electron microscopy with microanalysis have been used. The mechanical behavior has been evaluated in terms of cold crushing strength at room temperature and modulus of rupture at 25 and 1260 ◦ C. Static and dynamic resistances tested by chemical attack of clinker raw constituents have been carried out at 1450 ◦ C. Results showed that thermo-mechanical properties significantly improved with increasing the content of spinel. Microstructural analysis revealed that spinel phase aided to develop a strong bond between MgO and CaZrO 3 refractory aggregates. Finally, the refractory bodies exhibited a good thermal stability and an excellent chemical resistance against the clinker raw material. © 2013 Elsevier Ltd. All rights reserved. Keywords: MgO–CaZrO 3 matrix; Spinel; Refractory; Bonding; Rotary cement kiln 1. Introduction Magnesia based refractories have been widely used in cement rotary kilns and steel ladles due to their high melting point, no toxicity and good resistance to basic slags and clinker phases. However, they have some disadvantages, such as high ther- mal conductivity, poor thermal shock resistance and infiltration resistance against chemical attack. 1–3 In order to improve these properties, some metal oxides and compounds such as SiO 2 , CaO, Al 2 O 3 , MgAl 2 O 4 , Cr 2 O 3 , ZrO 2 , CaZrO 3 and FeAl 2 O 4 have been used as doping agent. These oxides may react with MgO to form a second phase which improves the process of sintering. In recent years, the burning zone of rotary cement kilns has been exposed to alkali salts and waste by-products such as rubber or other organic products from animal sources; these materials ∗ Corresponding author. Tel.: +52 81 83294020x1619; fax: +52 8183294020. E-mail addresses: earc22@hotmail.com, eden amaral rdz c@hotmail.com (E.A. Rodríguez). enhance the corrosion process of refractory bricks. Thus, under the severe service operating conditions present in the rotary cement kilns, industry has demanded the development of new refractory products for increasing the lining life. 3–12 Many stud- ies conducted by the refractory industry responds to the need for the development and implementation of new chrome-free basic bricks that meet the requirements presented in the kilns. In other hand, calcium zirconate is one of the most promis- ing high refractory compounds used in the steel and cement industry. 13 Particularly in the sintering zone, calcium zirconate (CaZrO 3 ), as a second phase of magnesia refractories works effectively improving the resistance against both clinker phase melting and alkali attack. 13 Specially, CaZrO 3 presents a high melting point (∼2340 ◦ C) and it is compatible with the MgO since does not react at any temperature and does not form a liquid phase up to temperatures higher than 2060 ◦ C. 14–16 Besides, it is compatible (does not react) with the main phases of Portland cement clinker in the solid state (C 2 S, C 4 AF and C 3 S). 17 Moreover, the solid–solid bonding between the com- patible MgO and CaZrO 3 phases is highly resistant to the infiltration of fluxes from the clinker. Previously, Obregón 0955-2219/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2013.04.027