Abstract
The shear viscosity and the glass-vapor surface tension at high temperature are crucial to understand the viscous flow sintering kinetics of porcelain stoneware. Moreover, the pyroplastic deformation depends on the viscosity of the whole body, which is made up of a suspension of crystals dispersed in the melt. The existing fundamental theoretical background, along with semi-empirical constitutive laws for viscous flow sintering and glass densification, can be exploited through different approaches to estimate the physical properties at high temperatures starting from amount and chemical composition of the melt. In this work, a comprehensive attempt to predict the properties of the liquid phase is proposed by means of a detailed overview of existing models for viscosity and surface tension of glasses and melts at high temperature. The chemical composition of the vitreous phase and its physical properties at high temperature are estimated through an experimental approach based on the qualitative and quantitative chemical and phase analyses (by Rietveld refinement of X-ray powder diffraction patterns) of different porcelain-like materials. Repercussions on the firing behavior of ceramic bodies, are discussed. Comparative examples are provided for porcelain stoneware tiles, vitreous china and porcelain bodies, disclosing differences in composition and properties but a common sintering mechanism.
Highlights
Vitrified ceramic tiles—complying the requirements for the Group BIa of ISO 13007—are manufactured essentially with porcelain stoneware bodies
The bodies can can be be inferred inferred through through aa methodological methodological approach approach which which entails entails aa normalized normalized difference difference bodies between chemistry of the bulk and their phase composition. Such a quantitative estimation gives back between chemistry of the bulk and their phase composition. Such a quantitative estimation gives back both the shear viscosity and the glass-vapor surface tension and it takes place by applying models from literature based on the chemical composition of the liquid phase
In this contribution it has been both the shear viscosity and the glass-vapor surface tension and it takes place by applying models from literature based on the chemical composition of the liquid phase
Summary
Vitrified ceramic tiles—complying the requirements for the Group BIa of ISO 13007—are manufactured essentially with porcelain stoneware bodies Their chemical composition differs considerably from both porcelain and red stoneware [1,2,3]. The interest on composition and technological behavior of porcelain stoneware bodies has been revitalized by an outstanding innovation process to manufacture gigantic slabs that can exceed 5 square meters [4,5]. In this framework, the physical properties at high temperature of porcelain stoneware tiles are important parameters in monitoring and controlling the different stages of industrial firing. The kinetics of the viscous flow sintering, which is expected to follow the Frenkel’s and Mackenzie-Shuttleworth’s models, where the densification rate is defined by the glass-vapor surface tension to shear viscosity ratio of the liquid phase [6,7,8].
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