TITLE:
Cocoa Cortex Ashes as Fluxing Additive for Vitrified Ceramic Making from Alluvial Clay
AUTHORS:
E. J. A. Ndzana, D. Njoya, A. Elimbi, G. V. Ranaivoarivo, G. Lecomte-Nana, A. N. Nzeukou, D. Njopwouo
KEYWORDS:
Poorly Fluxing Clay, Cocoa Cortex Ash, Flux, Stoneware
JOURNAL NAME:
Journal of Materials Science and Chemical Engineering,
Vol.7 No.10,
October
22,
2019
ABSTRACT: The aim of this study is to use Cocoa Cortex Ash (CCA) as alternative fluxing agent to manufacture vitrified ceramics at low temperatures from alluvial clay. Specimens of mixtures including clay and CCA (0%, 10%, 20% and 30% by mass) were used and fired respectively at 1050°C and 1100°C. X-ray diffraction and scanning electron microscopy were carried out. γ-alumine, mullite, akermanite, anorthite and grossular are new crystalline phases formed. Also, technological properties were determined on fired specimens as a function of CCA mass percentage. The results showed that firing shrinkage increased up to 8.5% for specimens with 10% by mass of CCA, then lessened up to 2% for specimens with 30% by mass of CCA. When fired at 1100°C, the specimens that initially contained 10% by mass of CCA allowed the formation of compact bodies with water absorption of 2% and flexural strength of 32 MPa. Hence, mixed at low percentage with poorly fluxing kaolinite clay, CCA can be used successfully as flux for the production of vitrified ceramics such as stoneware at low temperatures. The mixture of CCA with kaolinitic clay also promotes the formation of mullite and anorthite at low temperature.