Negative thermal expansion in porous glass-ceramics based on Mg 2 Al 2 B 2 Si 5 O 18 prepared from Saudi raw materials
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DOI 10.1007/s12206-020-1017-3
Journal of Mechanical Science and Technology 34 (11) 2020 Original Article DOI 10.1007/s12206-020-1017-3 Keywords: · Crystallization · Glass-ceramics · Porous cordierite · Negative thermal expansion
Correspondence to: Samah S. Eldera [email protected]
Citation: Eldera, S. S., Al-wafi, R., Al Harbi, O. A., Rüssel, C., Hamzawy, E. M. A. (2020). Negative thermal expansion in porous glass-ceramics based on Mg2Al2B2Si5O18 prepared from Saudi raw materials. Journal of Mechanical Science and Technology 34 (11) (2020) 4597~4604. http://doi.org/10.1007/s12206-020-1017-3
Received February 3rd, 2020 Revised
July 12th, 2020
Accepted August 25th, 2020 † Recommended by Editor Chongdu Cho
Negative thermal expansion in porous glass-ceramics based on Mg2Al2B2Si5O18 prepared from Saudi raw materials Samah S. Eldera1,2, Reem Al-wafi1, Omar A. Al Harbi3, Christian Rüssel4 and Esmat M. A. Hamzawy5 1
2
Physics Dep., Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia, Physics Depart3 ment, Faculty of Science, Al-Azhar University, Cairo, Egypt, King Abdulaziz City for Science and Tech4 nology, PO Box 6086, Riyadh 11442, Saudi Arabia, Otto-Schott-Institut, Fraunhoferstrasse 6, 07743 5 Jena, Germany, Glass Research Dep., National Research Centre, Dokki, Cairo P.C. 12622, Egypt
Abstract
A porous glass-ceramic enjoyed very low and negative thermal expansion was prepared. A glass of the base molar composition, 2 MgO·2 Al2O3·2 B2O3·5 SiO2 with the addition of 1.61 ma% TiO2, was melted from kaolin, magnesite, silica sand and boric acid. The composition is based on cordierite where 50 % Al2O3 were replaced by an equimolar concentration of B2O3. The glass was crashed and powdered, subsequently plastified, uniaxially pressed and finally sintered at temperatures in the range from 1100 to 1300 °C. X-ray diffraction of sintered samples gave evidence of a cordierite like crystalline phase. Scanning electron microscopy and electron dispersive microanalysis of samples prepared at 1300 °C showed crystals with hexagonal shape doped by TiO2, B2O3 and Fe2O3 embedded in a glassy matrix. With increasing crystallization temperature, the porosity of the glass-ceramics increased from 8.99 % (at 1200 °C for 3 min) to 56.42 % (at 1300 °C for 3 min). This led to a decrease of the specimen density from 1.9880 to 1.1278 g/cm3 whereas the skeletal density increased from 2.1303 g/cm3 to 2.5878 g/cm3. The microhardnesses were in the 5.60 and 6.00 GPa range. The coefficient of thermal expansion was between -3.26 and -2.27x10-6 K-1 from room temperature up to 300 oC and -0.45 and 1.89x10-6 K-1 from room temperature up to 500 °C. For the first time, to the best of our knowledge, a porous cordierite glass-ceramic with negative thermal expansion is reported. The partial replacement of Al2O3 by B2O3 enables to apply lower melting temperature which is advantageous for the production process.
1. Introduction
© The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2020
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