The Mechanism of Porcelain Toughened by Activated Kaolinite in a Lower Sintering Temperature

Abstract

A high sintering temperature is usually required to acquire excellent performance in the ceramic industry, but it results in high fuel consumption and high pollution. To reduce the sintering temperature and to toughen the porcelain, a self-produced sintering additive of citric acid activated kaolinite was added to the raw material; X-ray powder diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and thermal gravity analysis and differential scanning calorimetry (TG-DSC) were used to characterize the samples, and the toughening mechanism was discussed. The citric acid activated kaolinite obtained high activity and a large specific surface area. After introducing the activated kaolinite, the bending strength of porcelain at 1270 °C increased from 100.08 MPa to 124.04 Mpa, which was 11.45% higher than that of porcelain without activated kaolinite at 1350 °C. The results of XRD revealed that the content of mullite increased and the quartz decreased at 1270 °C, and the well-distributed needle-like mullite was observed in the images of SEM with the addition of citric acid activated kaolinite. The TG-DSC results indicated adding activated kaolinite to porcelain raw materials reduced the formation of mullite to 994.6 °C. The formation of mullite in a lower temperature served as mullite seeds in a green body during firing, and it enhanced the growth of mullite. These contributed to the appropriate phase composition and the excellent microstructure of porcelain. Thus, the distinguished mechanical performance of porcelain was obtained. Moreover, the sintering additive had no adverse effect on the porcelain body as citric acid-activated kaolinite was one of the main components of the porcelain raw material.

Preparation of Anorthite/Mullite In Situ and Phase Transformation in Porcelain

“…Five samples from each group were measured to obtain reliable water absorption, bulk density, and bending strength values [ 5 , 22 ]. The weight (g) of samples was measured using a precision electronic balance (FA3204B, Tianmei, Shanghai, China) with a density determination device (MD, Tianmei, Shanghai, China).…”

“…The most significant development in the history of ceramics to date is the production of vitrified and translucent porcelain in ancient China [ 1 ]. The three-component system of clay–feldspar–quartz is widely used in the ceramic industry [ 2 , 3 , 4 , 5 ]. The main components of the sintered product are quartz (11 × 10 −6 K −1 ), mullite (5.7 × 10 −6 K −1 ), and feldspar glass (4.8 × 10 −6 K −1 ).…”

Conditioning Influence of Kaolinite Matrices on Flexural Strength of Raw Pressed Slurry Collected from Ceramic Tile Production Wastewater

“…When kaolinite particles are under intensive movement, admixture with other, harder, mineral particles like quartz might act as milling bodies generating very small fractions. Such a mechanism was observed in the quartz-kaolinite interaction in environmental street dust [11,12], but it is currently used in raw material preparation in the ceramic industry for porcelain pottery [13,14] and ceramic tiles [15,16]. The mineral admixture is milled under a wet condition at a very well-controlled humidity level to obtain ceramic paste, which is further molded into dies.…”