Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics
The effective utilization of fly ash (FA) as a raw material for ceramics production is performed on the FA-kaolin mixtures containing kaolins 10% by mass. The mixtures in comparison with FA and three raw kaolins were annealed to mullite ceramics at temperatures of 1000, 1100, 1200 and 1300 °C. The m...
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| Format: | Article |
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MDPI AG
2021-08-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/8/887 |
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| author | Marta Valášková Veronika Blahůšková Jozef Vlček |
| author_facet | Marta Valášková Veronika Blahůšková Jozef Vlček |
| author_sort | Marta Valášková |
| collection | DOAJ |
| description | The effective utilization of fly ash (FA) as a raw material for ceramics production is performed on the FA-kaolin mixtures containing kaolins 10% by mass. The mixtures in comparison with FA and three raw kaolins were annealed to mullite ceramics at temperatures of 1000, 1100, 1200 and 1300 °C. The main aims were to contribute to the discussion on the effect of impurity of Na,K-feldspars in kaolins and Fe<sub>2</sub>O<sub>3</sub> in FA on sintering procedure, porous ceramics properties and mullite structural properties. The phases were characterized using X-ray diffraction and thermogravimetry DTA/TGA methods. Mercury intrusion porosimetry was used for characterization of porosity of ceramic samples. Results evidenced the influence of feldspars in kaolins and Fe<sub>2</sub>O<sub>3</sub> in FA on the sintering temperatures and properties of mullite ceramics. The fully FA-based ceramic sintered at 1100 °C exhibited post-sintering properties of bulk density 2.1 g/cm<sup>3</sup>; compressive strength 77.5 MPa; and porosity, 2% in comparison with the FA/kaolin-based ceramics properties of bulk density 2.2 g/cm<sup>3</sup>; compressive strength, 60–65 MPa; and porosity from 9.3 to 16.4% influenced by Na,K-feldspars. The best structural and mechanical characteristics were found for the FAK3 sample, supported by the high content of kaolinite and orthoclase in the kaolin K3 additive. The FAK3 annealed at 1100 °C exhibited good compressive strength of 87.6 MPa at a porosity of 10.6% and density of 2.24 g/cm<sup>3</sup> and annealed at 1300 °C the compressive strength of 41.3 MPa at a porosity of 19.2% and density of 1.93 g/cm<sup>3</sup>. |
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| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T08:34:33Z |
| publishDate | 2021-08-01 |
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| record_format | Article |
| series | Minerals |
| spelling | doaj.art-cc4a703b57834e88a4adf9f02376f4072023-11-22T08:50:25ZengMDPI AGMinerals2075-163X2021-08-0111888710.3390/min11080887Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite CeramicsMarta Valášková0Veronika Blahůšková1Jozef Vlček2Institute of Environmental Technology, CEET, VŠB-Technical University of Ostrava, 17. Listopadu 2172/15, 708 00 Ostrava–Poruba, Czech RepublicInstitute of Environmental Technology, CEET, VŠB-Technical University of Ostrava, 17. Listopadu 2172/15, 708 00 Ostrava–Poruba, Czech RepublicInstitute of Environmental Technology, CEET, VŠB-Technical University of Ostrava, 17. Listopadu 2172/15, 708 00 Ostrava–Poruba, Czech RepublicThe effective utilization of fly ash (FA) as a raw material for ceramics production is performed on the FA-kaolin mixtures containing kaolins 10% by mass. The mixtures in comparison with FA and three raw kaolins were annealed to mullite ceramics at temperatures of 1000, 1100, 1200 and 1300 °C. The main aims were to contribute to the discussion on the effect of impurity of Na,K-feldspars in kaolins and Fe<sub>2</sub>O<sub>3</sub> in FA on sintering procedure, porous ceramics properties and mullite structural properties. The phases were characterized using X-ray diffraction and thermogravimetry DTA/TGA methods. Mercury intrusion porosimetry was used for characterization of porosity of ceramic samples. Results evidenced the influence of feldspars in kaolins and Fe<sub>2</sub>O<sub>3</sub> in FA on the sintering temperatures and properties of mullite ceramics. The fully FA-based ceramic sintered at 1100 °C exhibited post-sintering properties of bulk density 2.1 g/cm<sup>3</sup>; compressive strength 77.5 MPa; and porosity, 2% in comparison with the FA/kaolin-based ceramics properties of bulk density 2.2 g/cm<sup>3</sup>; compressive strength, 60–65 MPa; and porosity from 9.3 to 16.4% influenced by Na,K-feldspars. The best structural and mechanical characteristics were found for the FAK3 sample, supported by the high content of kaolinite and orthoclase in the kaolin K3 additive. The FAK3 annealed at 1100 °C exhibited good compressive strength of 87.6 MPa at a porosity of 10.6% and density of 2.24 g/cm<sup>3</sup> and annealed at 1300 °C the compressive strength of 41.3 MPa at a porosity of 19.2% and density of 1.93 g/cm<sup>3</sup>.https://www.mdpi.com/2075-163X/11/8/887fly ashkaolinsmullitemicrostructureporosity |
| spellingShingle | Marta Valášková Veronika Blahůšková Jozef Vlček Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics Minerals fly ash kaolins mullite microstructure porosity |
| title | Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics |
| title_full | Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics |
| title_fullStr | Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics |
| title_full_unstemmed | Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics |
| title_short | Effects of Kaolin Additives in Fly Ash on Sintering and Properties of Mullite Ceramics |
| title_sort | effects of kaolin additives in fly ash on sintering and properties of mullite ceramics |
| topic | fly ash kaolins mullite microstructure porosity |
| url | https://www.mdpi.com/2075-163X/11/8/887 |
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