Effects of particle size distribution and starting phase composition in Na-feldspar/kaolinite system at high temperature. Issue 4 (April 2015)

• Record Type: Journal Article
• Authors: Diella, Valeria; Adamo, Ilaria; Pagliari, Lucia; Pavese, Alessandro; Francescon, Fernando
• Is Part Of: Journal of the European Ceramic Society. Volume 35:Issue 4(2015:Apr.)
• Page Start: 1327
• Page End: 1335
• Publication Date: 2015-04
• Subjects: Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2014.10.035
• Languages: English
• ISSNs: 0955-2219

Abstract

<abstract abstract-type="author" id="abs0005"> <title id="sect0005">Abstract</title> <sec> <p id="spar0005">Mullite-glass Gibbs energy of formation (Δ<italic>G</italic><sub>eff</sub>), micro-texture and phase composition evolution are investigated in the Na-feldspar (<italic>F</italic>) and kaolinite (<italic>K</italic>) system, over the 1240–1320 °C interval, as a function of the starting <italic>F</italic>/<italic>K</italic> ratio by weight and particle size distribution of <italic>F</italic> (<<italic>s</italic>>), using scanning electron microscopy, X-ray diffraction and thermodynamic modeling. Electron microscopy images show that size and aspect ratio of primary and secondary mullite have their largest figures for the smallest <<italic>s</italic>> and, in general, monotonically increase upon firing temperature. Δ<italic>G</italic><sub>eff</sub> has been modeled by <italic>α</italic>(<<italic>s</italic>>) × (<italic>F</italic>/<italic>K</italic>)<sup>2</sup> + <italic>β</italic>(<<italic>s</italic>>) × <italic>F</italic>/<italic>K</italic> + <italic>γ</italic>(<<italic>s</italic>>) (<italic>α</italic>, <italic>β</italic> and <italic>γ</italic> are linear functions of <<italic>s</italic>>). The parameters of such a function have been determined by fitting it to the experimental Δ<italic>G</italic><sub>eff</sub>s, inferred from quantitative phase analysis of X-ray diffraction patterns. Note that we used average Δ<italic>G</italic><sub>eff</sub>-values over the <italic>T</italic>-range explored because of the modest dependence on temperature shown. We have gathered that (i) <italic>F</italic>/<italic>K</italic> affects energetics and mullite content more markedly than <<italic>s</italic>> does, and (ii) the mullite formation is energetically favored by decreasing <italic>F</italic>/<italic>K</italic> and increasing <<italic>s</italic>>.</p> </sec> </abstract>