Influence of Glassy Additives on the Formation of Crystalline Phases in Sintered Red Ceramic Bodies
- PDF / 415,731 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 14 Downloads / 199 Views
Influence of Glassy Additives on the Formation of Crystalline Phases in Sintered Red Ceramic Bodies A.F. Chávez-Villanueva1, G. Vargas-Gutiérrez1, J. López-Cuevas1 and C.M. López-Badillo2 1 CINVESTAV Unidad Saltillo, Avenida Industria Metalúrgica No. 1062, Parque Industrial Saltillo-Ramos Arizpe, Ramos Arizpe, Coahuila, México, CP 25900. 2 Universidad Autónoma de Coahuila, Facultad de Ciencias Químicas, Blvd. V. Carranza s/n, Col. República Oriente, Coahuila, México, CP 25280. ABSTRACT The main objective of this research work was to study the influence of glassy additives on the formation of crystalline phases in sintered red ceramic bodies used for the fabrication of ceramic floor tiles, whose composition is a mixture of quartz (SiO2), kaolinite [Al2Si2O5(OH)4], albite (NaAlSi3O8), muscovite [KAl2(Si3Al)O10(OH)2] and calcite (CaCO3). The additives used were: fly ash, soda-lime glass, borosilicate glass, glass frit, Na2P3O10 and cryolite (Na3AlF6). These were added in variable proportions to the nominal composition of the red ceramic bodies, either as single or as combined additions, aiming to accelerate the densification of the materials during their sintering process. For all the additive types used, the crystalline phases formed in the samples sintered using a peak temperature ranging from 950 to 1030 ºC were: quartz (SiO2), anorthite (CaAl2Si2O8), and hematite (Fe2O3). It is known that the presence of anorthite is particularly beneficial for the mechanical properties, chemical stability and densification of the sintered red ceramic bodies. However, some of the considered additions tended to be detrimental for the formation of this phase in the studied materials, especially at the lowest peak sintering temperature employed. This was verified by means of XRD and SEM analysis. INTRODUCTION The addition of glassy additives to the red ceramic bodies used for the fabrication of ceramic floor tiles can accelerate their densification during the sintering process [1-3]. However, the employment of these additives could affect the nature and microstructural characteristics of the crystalline phases that are formed in the sintered ceramic bodies, with a likely detrimental effect on their mechanical, physical and chemical properties. Crystallization of anorthite [CaAl2Si2O8, calcium aluminosilicate belonging to the family of feldspars (plagioclase)] is particularly desired in the microstructure of the red ceramic bodies, since it significantly increases their mechanical properties, chemical stability and density. Thus, it is of practical importance to verify that the formation of this phase is not significantly affected by the addition of glassy fluxing agents to the initial mixture of raw materials employed for the production of the red ceramic bodies.
77
EXPERIMENTAL DETAILS The nominal composition of the red ceramic bodies was (in wt.%): 50-60 % SiO2, 17-19% Al2O3, 5-7% Fe2O3, 2-3% CaO and 2-3% K2O. This was formulated from a mixture of stoichiometric proportions of quartz (SiO2), kaolinite [Al2Si2O5(OH)4], albite (NaA
Data Loading...
