Ceramic Refractory Compositions with Biosolubility Characteristics
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Ceramic Refractory Compositions with Biosolubility Characteristics Ma.G. Joaquín-Morales, G. Vargas-Gutiérrez*, J.L. Rodríguez-Galicia, G.I. VazquezCarbajal, J. López-Cuevas CINVESTAV-IPN, Unidad Saltillo, Ave. Industria Metalúrgica No. 1062, Parque Industrial Saltillo-Ramos Arizpe, Ramos Arizpe, Coahuila, CP 25900, México. *e-mail: [email protected] ABSTRACT In this work, we studied the dissolution of three different refractory compositions belonging to the ternary system SiO2-CaO-MgO into two Simulated Lung Fluids (SLF). The initial powder mixtures were uniaxially pressed and then sintered at 1300-1400 °C. The sintered samples were immersed for times from 1 to 21 days into a given SLF at 37 °C. The samples were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The dissolution of Ca2+, Mg2+ and Si4+ into the SLF was quantified by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The in vitro studies suggested that all the considered materials had a potential to show a diminished biopersistence in vivo, due to reasons that depended on their chemical and phase composition. INTRODUCTION Refractory materials are widely employed in different industrial processes that require high temperatures. Their installation and use may produce tiny airborne fibers that could be inhaled by humans. The continuous contact with these fibers could be associated with adverse biologically effects, such as lung cancer [1]. Because of this, new alternatives must be found for the manufacturing of safer refractory materials. Nowadays there exist some refractory materials with the capacity to show a diminished biopersistence (length of time that an intact fiber remains in the lung and pleura; the longer the biopersistence, the greater the health risk). However, this is usually associated with a reduced service temperature for them. Therefore, the main aim of this work was to develop different refractory compositions with the capacity to be biosoluble, while keeping other technical properties unaltered. For the determination of the biosolubility properties of the studied compositions, two Simulated Lung Fluids (SLF) were used to carry out the in vitro studies required by the International Agency of Research on Cancer in order to disqualify a material as hazardous. In this work, only the results obtained from the latter studies are reported. The evaluation of the technical properties of the synthesized refractory materials is intended to be reported separately in a future publication. EXPERIMENTAL DETAILS Sample preparation SiO2, MgO and CaCO3 powders with a minimum purity of 97 wt.% and with a particle size of ~20 Pm were mixed in suitable proportions in order to prepare the three refractory
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compositions shown in Table I. The mixtures were uniaxially pressed at 5 MPa into cylinders with a diameter of 2.5 cm and a height of ~ 0.5 cm. Then, the pressed samples of a particular composition were sintered for 1h at a temperature ~100 °C below the invariant point of the compatibility
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