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Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
The MgO–Al2O3–SiO2 system is of considerable importance to the ceramic industry. Many of the compositions including SiO2, Al2O3, forsterite, mullite, and spinel are used in refractories for high-temperature furnace linings. Forsterite, Al2O3, MgO · SiO2, and cordierite are good electrical insulators and are used in the electronics industry. Cordierite has low thermal expansion and has excellent thermal shock resistance.
General Information About Electrical Heating Elements
Published in Thor Hesborn, Integrating Electrical Heating Elements in Appliance Design, 2017
Cordierite (2MgO, 2Al2O3, 5SiO2) contains 60% SiO2, 30%Al2O3, and 8.6% MgO. It is porous and takes up 3 to 13% water. Cordierite is used as support for resistance material, for instance, for open cartridge elements (see Section 5.3.5). in the system SiO2-Al2O3-MgO it has the lowest thermal expansion and also the highest thermal shock resistance, but the melting point is as low as 1350°C.
Crystalline and Two-Phase Materials
Published in Solomon Musikant, Optical Materials, 2020
For example, mullite is shown as 0 wt% MgO, 73 wt% Al2O3, and 27 wt% SiO2. Cordierite (2MgO·Al2O3·5SiO2) is plotted at 14 wt% MgO, 35 wt% Al2O3, and 51 wt% SiO2.
Investigation of low-temperature performances of hybrid catalysts with different chain length OHC reductants
Published in Environmental Technology, 2022
Zeycan Keskin, Mustafa Atakan Akar
Different types of catalysts are used for the NOx reduction. A catalyst consists of catalytically active components and a ceramic or metallic substrate material [20]. Cordierite (2Al2O3.5SiO2.2MgO) monolith is the most commonly used substrate [21]. Cordierite material has many advantages such as low thermal expansion coefficient, economical and hydrothermal stability [10,19,22]. TiO2, Al2O3, SiO2, CeO2, zeolite and carbon are often used in the catalysts as carriers to increase surface area [21,23,24].
Processing of electric ceramic insulators from slate rocks and MgO
Published in Materials and Manufacturing Processes, 2020
S. M. Naga, M. Sayed, M. M. El-Omla, Ahmed R. Wassel, N. El-Mehalawy
Cordierite (Mg2Al4Si5O18) is considered a promising structural material that is used in several applications due to its specific unique characteristics. It is used in kiln furniture as a thermal coat for metals for gas turbine engines in the manufacture of gas exchangers for automobile mufflers because of its low thermal expansion coefficient, premium resistance to thermal shock and high refractoriness and for solar thermal storage.[1–3] In addition, cordierite possesses a low dielectric constant with an adequate electrical resistivity, which makes it a candidate for use as an integrated circuit substrate[4–6] and in millimeter wave dielectrics.[7] Moreover, the combination of the electrical, electromechanical and thermal properties of cordierite enable it to be used in internal combustion components[8] and for thermal insulation purposes.[9] Freer and Owate (1990)[10] found that the breakdown strength for cordierite glass ceramics (SiO2–MgO–Al2O3–TiO2) is highly affected by homogeneity and crystal size and shape. On the other hand, the dielectric constant and dielectric loss of dense cordierite are reduced upon increasing both the densification temperature and the test frequency.[11] The main factors that control the development of the cordierite phase are the starting material type, composition and purity and the fabrication methods. Several attempts have been made to develop cordierite as the main phase from natural resources. Cordierite has been conventionally synthesized from natural raw materials such as magnesite, talc and kaolin.[12,13] Talc, calcined bauxite and quartz were used to prepare cordierite via solid-state reaction at temperatures ranging from 1300 °C to 1420 °C.[14] Talc carbonate rocks, kaolin, and alumina have also been used to prepare cordierite bodies.[15] The addition of 2.5 mass% B2O3 to a cordierite batch prohibited the formation of µ-cordierite and lessened the probability of any silicate phase formation except α-cordierite.[15] Piresde et al.[16] showed that the factors that affect cordierite formation are the firing temperature and the median particle size. They claimed that cordierite begins to crystallize at 1250°C, while the produced bodies are sintered at 1350°C. They also stated that batches composed of kaolin waste, MgO, and talc are suitable for the synthesis of cordierite.
Sustainable ceramics derived from solid wastes: a review
Published in Journal of Asian Ceramic Societies, 2020
Cordierite (Mg2Al4Si5O18) is a famed oxide ceramics for its exciting properties such as very low thermal coefficient ((1–2)×10−6°C−1 between 20°C and 800°C), elevated thermal stability, excellent insulator, low dielectric constant and good chemical durability. This makes it a promising candidate to fabricate components for the support of several applications like thermal insulators, furnace refractories, membranes, filters, integrated circuit boards, and catalysts [155–157]. The synthesis of pure cordierite by the advanced techniques is limited due to its expensive raw materials. Recently, researchers have focused their investigation on preparing low-cost cordierite using waste materials. Table 6 illustrates some examples of waste-derived cordierite with different parameters. Hajjou et al. (2017) [158] have developed cordierite ceramics using FA along with magnesium chloride and silica gel to maintain the stoichiometry of cordierite (2MgO·2Al2O3·5SiO2). They have concluded that cordierite is started to form at 1200°C and the pure phase is obtained at 1300°C with a small amount of spinel. Dong et al. (2006) [159], Liu et al. (2015) [160] and Długosz et al. (2016) [161] have also used FA to fabricate the cordierite ceramics. Zhu et al. (2012) [162] have prepared cordierite by solid-state reactions with three different types of raw materials, i.e., waste kaolin mine tailing as the source of SiO2 and Al2O3, waste serpentine mine tailing as the source of SiO2 and MgO, and alumina powder. Single-phase cordierite is achieved after sintering the pressed mixture mass at 1350°C for 3 h. Ramezani et al. (2017) [163] and Zhou et al. (2011) [164] have fabricated cordierite using waste serpentine and sepiolite (after heat treatment its transform into serpentine), respectively. Some studies also have found to investigate with RHA as an alternate of conventional silica sources for the preparation of cordierite [165–167]. Another author Xiang et al. (2016) [168] have used waste foundry sand (solid waste from metal casting industries) as a source of silica and alumina to prepared cordierite. Liu et al. (2016) [169] have prepared the porous cordierite ceramics using ferrochromium slag along with commercial silica and alumina powder without any pore-forming ingredients. They have found that 87 wt.% of the cordierite phase is developed in the system at 1350°C along with open porosity around 32.8% and flexural strength about 47.26 MPa. Xingrong et al. (2013) [170] have utilized blast furnace slag for synthesizing cordierite powder. Cordierite phases are formed in the range of calcination temperature at 1200–1300°C. Almeida et al. (2018) [171] have investigated the cordierite synthesis from kaolin waste, magnesia, and talc powder. They have revealed that the beginning of the cordierite phase formation is at around 1250°C and more peaks are found at 1350°C.