Physico-chemical characterization of feldspars for application as fluxing agents: Experimental and ab initio computational approaches

Abstract

Feldspars are tectosilicates with unique composition and structural features employed to help develop the glassy phase while firing ceramic raw materials. This promotes vitrification by lowering sintering temperatures thereby making it more energy efficient and sustainable. This study examined the physico-chemical parameters of feldspars found in Marimanti, Tharaka Nithi county in Kenya with the aim of determining their fluxing capabilities. This was achieved through the use of ab-initio theoretical computations and experimental investigation into phases, morphology and thermal stability. Experimental results showed albite and anorthite mineral phases with dominant alumina and silica content, classifying it as a plagioclase type. Further experimental results revealed four predominant phases viz: Ca-feldspar, K-feldspar, Na-feldspar and quartz with mesoporous morphology and average particle sizes of 5 μm. Thermal stability studies showed a significant derived weight loss per °C in the 400–700 °C range with a peak at 497.67 °C. Three-dimensional atomistic simulations conducted on albite, anorthite and feldspar mineral phases were computed using the Cambridge Serial Total Energy Package (CASTEP) module of Material Studio software, using generalized gradient approximation (GGA) with Perde-Burke-Ernzerhof (-PBE) correction function. Accordingly, ab initio studies showed the minerals had a 3D triclinic lattice structure with predicted bulk moduli of 45.91 GPa and 88.86 GPa for albite and anorthite, respectively. In furtherance, the computed band gap energies were 2.644 eV for albite and 2.661 eV for anorthite, indicating high insulation capacity for both mineral phases. Overall, the experimental and computational results obtained were in agreement with literature on fluxing properties. Further, the outstanding properties reported indicated high quality feldspars which can be exploited sustainably for application as fluxing agents . • Physico-chemical parameters of feldspars determine their fluxing capabilities. • Significant derived weight loss per °C peaked at 497.67 °C. • Via ab initio studies, the feldspar minerals have 3D triclinic lattice structures. • Band gap energies indicate high insulation capacities for feldspars studied.