The present work reports the effect of carbonate addition to iron rich kaolinite on the phase transformation during firing. Mineralogical, thermal (including DTA-TGA and dilatometric) and physico-mechanical analyses w...The present work reports the effect of carbonate addition to iron rich kaolinite on the phase transformation during firing. Mineralogical, thermal (including DTA-TGA and dilatometric) and physico-mechanical analyses were performed on fired product made from a mixture of kaolinite and 8% by mass of dolomite. The firing temperatures used are 920°C, 1050°C, 1150°C, 1200°C and 1250°C. The major mineral phases formed during firing are mullite, cristobalite and hematite associated to gehlenite and anorthite at temperature >1150°C. Their presence induces increased densification of the product that results in an increased in the flexural strength up to 1150°C. Beyond this temperature, increase glassy phase formation together with hematite development, induce a decrease of the flexural strength as well as the porosity and water adsorption. The SEM observations show that primary mullite is formed as from 1150°C. The EDS analysis from SEM is coherent with the chemical and the mineralogical analyses from XRD. The overall analyses indicate that the addition of dolomite at 8% by mass is favorable to vitreous ceramic formation as from 1050°C.展开更多
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% ...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.展开更多
文摘The present work reports the effect of carbonate addition to iron rich kaolinite on the phase transformation during firing. Mineralogical, thermal (including DTA-TGA and dilatometric) and physico-mechanical analyses were performed on fired product made from a mixture of kaolinite and 8% by mass of dolomite. The firing temperatures used are 920°C, 1050°C, 1150°C, 1200°C and 1250°C. The major mineral phases formed during firing are mullite, cristobalite and hematite associated to gehlenite and anorthite at temperature >1150°C. Their presence induces increased densification of the product that results in an increased in the flexural strength up to 1150°C. Beyond this temperature, increase glassy phase formation together with hematite development, induce a decrease of the flexural strength as well as the porosity and water adsorption. The SEM observations show that primary mullite is formed as from 1150°C. The EDS analysis from SEM is coherent with the chemical and the mineralogical analyses from XRD. The overall analyses indicate that the addition of dolomite at 8% by mass is favorable to vitreous ceramic formation as from 1050°C.
文摘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.
