Microstructure and technological properties of porcelain stoneware tiles moulded at different pressures and thicknesses

Abstract

Moulding pressure and thickness are pre-fixed variables in the porcelain stoneware tile industry. This paper examines the effect of both parameters on technological and microstructure properties of unfired and fired porcelain stoneware bodies. The moulding pressure in unfired tiles has a noticeable effect on bending strength and load borne. Common technological properties such as water absorption, porosity, bulk density and bending strength were obtained from the fired tiles. The results indicate that the variation in properties is independent of the thicknesses of the tiles. Moulding pressure affects at lower values, whereas higher moulding pressure produces tiles with similar technological properties. The microstructure exhibits a constant amount of mullite and quartz in all pieces after the firing process. Observations from scanning electron microscopy show that mullite crystals enlarge as moulding pressure increases, but the shape of the crystals are unaffected by the individual thicknesses. Furthermore, the aspect ratio of the mullite needles increases with the moulding pressure, which is invariable to the thicknesses of the tiles. Although the total porosity remains constant, the number of pores is influenced by the thickness. The moulding pressure also influences pore size. The results show a strong relationship between the number of closed pores and the thickness of the ceramic tile.

Relation between the microstructure and technological properties of porcelain stoneware. A review

“…Similar findings on the effect of the aspect ratio of mullite needles on the mechanical strength of porcelain stoneware were reported by Pérez et al (66,67). The authors studied the influence of thickness and moulding pressure on the technological properties and microstructure of porcelain stoneware tiles.…”

“…Pérez et al (66,67) addressed that open porosity generally decreases as moulding pressure increases; this reduction is more noticeable at lower thicknesses. Higher moulding pressure leads to highly compact unfired bodies with a lower volume of voids; therefore, the elimination of open pores by the liquid phase formed during firing is favoured.…”

Optimization of the technological properties of porcelain tile bodies containing rice straw ash using the design of experiments methodology

“…a CTE value  9.0 x 10 -6 °C -1 at temperatures < 100 °C, matching the findings of Biffi and Prado [50,61] and the results reported in ISO standard 13006 [1]. Figure 10a shows that the MOR of the fired test pieces exhibited a similar trend to that shown by fired bulk density, coinciding with reports in the literature suggesting that mechanical strength (and also Young's modulus) are strongly affected by densification, so that the greater the fired bulk density, the higher is the MOR [59][60][61][62]. Consequently, the MOR became lower as the RSA content in the mixtures increased; however, the MOR values of all mixtures lay above the minimum value laid down in ISO standard 13006 ( 35 MPa) for the classification of Group BI a dry-pressed ceramic tiles with low water absorption [1].…”

Microstructural Characterization and Thermal Properties of Aluminium Titanate/Porcelain Ceramic Matrix Composites

“…The uxing agent is feldspar and the ller is quartz, which most likely leads to higher strengths of the unred tiles. Firing bodies containing these three components exhibit a grain and bond microstructure, which consists of coarse quartz grains joined by a ner bond or matrix that contains mullite crystals and a glassy phase [1].…”