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Victor C. Pandolfelli - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolution of magnesia-based castables containing Microsilica
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract The higher performance of refractory materials applied in steelmaking vessels is mainly associated with the development of high-magnesia bricks. However, the same success has not yet been attained for the production of high-quality magnesia-based castables, due to the well-known magnesia hydration trend. In order to overcome this drawback, Microsilica addition was tested as an anti-hydration additive in the present work. As it also leads to liquid formation at high temperatures in high-alumina CAC-containing castable compositions, the microstructural development of Microsilica-containing magnesia-based castables was also analyzed by scanning electron microscopy, thermodynamics simulations and sintering assisted tests. According to the results, Microsilica hindered the magnesia hydration and provided an additional bonding mechanism due to the reaction with MgO and water. Moreover, it helped to control the material's volumetric change by reducing the expansion associated with the spinel formation and also the shrinkage level afterwards.

  • The corrosion resistance of Microsilica-containing Al2O3–MgO and Al2O3–spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

  • the corrosion resistance of Microsilica containing al2o3 mgo and al2o3 spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

  • Microsilica or MgO grain size: Which one mostly affects the in situ spinel refractory castable expansion?
    Ceramics International, 2009
    Co-Authors: Mariana A. L. Braulio, P O Brant, L R M Bittencourt, Victor C. Pandolfelli
    Abstract:

    Microsilica is commonly added to alumina-magnesia castables to counterbalance the in situ spinel expansion. This effect is attained by the generation of a low-melting temperature phase, which also affects the expansive reaction kinetics. Additionally, the MgAl 2 O 4 formation depends on the grain size of the reactants. The use of coarse magnesia grains results in lower Mg 2+ dissolution and could lead, at 1500 °C, to forsterite development (Mg 2 SiO 4 ). For finer MgO, silica was detected at the edge of the spinel grains. Considering these aspects, this work evaluated the effect of Microsilica content for different magnesia grain sizes (

  • Kaolin, metakaolin and Microsilica as fillers for high-alumina refractory castables
    American Ceramic Society Bulletin, 2002
    Co-Authors: M. V. Gerotto, Victor C. Pandolfelli, André R. Studart, Murilo D. M. Innocentini, S. S. Cabo
    Abstract:

    Although the total replacement of Microsilica by kaolin or metakaolin degrades the high-temperature behavior of high-alumina castables, a partial substitution can be attractive when Microsilica is expensive, because this substitution can significantly decrease the refractory cost yet maintain on acceptable mechanical strength.

Lei Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Microstructures and mechanical properties of Al2O3–ZrO2–C refractories using silicon, Microsilica or their combination as additive
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012
    Co-Authors: Haibing Fan, Yupeng Huang, Shaobai Sang, Lei Zhao
    Abstract:

    Abstract Silicon, Microsilica and their combination were used as additive in carbon containing refractories, respectively. The effects of such additive on microstructures and mechanical properties of Al 2 O 3 –ZrO 2 –C refractories were investigated. The results show that in refractories of this kind, silicon is responsible for the formation of SiC whiskers; Microsilica mainly dominates the formation of mullite; while their combination (silicon plus Microsilica) brings high partial pressure of SiO(g) and leads to the co-existence of finer SiC whiskers and needle-like mullite. The various microstructures unquestionably cause differences in mechanical properties of Al 2 O 3 –ZrO 2 –C refractories. The use of silicon mainly results in an enhanced mechanical strength, while the addition of Microsilica primarily triggers the improvement in toughness. When the combination of silicon and Microsilica is used as additive, excellent strength and toughness can be obtained simultaneously in Al 2 O 3 –ZrO 2 –C refractories, which is mainly attributed to the synergistic effects of SiC whiskers formed from silicon additive and needle-like mullite formed from Microsilica additive.

  • microstructures and mechanical properties of al2o3 zro2 c refractories using silicon Microsilica or their combination as additive
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012
    Co-Authors: Haibing Fan, Yupeng Huang, Shaobai Sang, Lei Zhao
    Abstract:

    Abstract Silicon, Microsilica and their combination were used as additive in carbon containing refractories, respectively. The effects of such additive on microstructures and mechanical properties of Al 2 O 3 –ZrO 2 –C refractories were investigated. The results show that in refractories of this kind, silicon is responsible for the formation of SiC whiskers; Microsilica mainly dominates the formation of mullite; while their combination (silicon plus Microsilica) brings high partial pressure of SiO(g) and leads to the co-existence of finer SiC whiskers and needle-like mullite. The various microstructures unquestionably cause differences in mechanical properties of Al 2 O 3 –ZrO 2 –C refractories. The use of silicon mainly results in an enhanced mechanical strength, while the addition of Microsilica primarily triggers the improvement in toughness. When the combination of silicon and Microsilica is used as additive, excellent strength and toughness can be obtained simultaneously in Al 2 O 3 –ZrO 2 –C refractories, which is mainly attributed to the synergistic effects of SiC whiskers formed from silicon additive and needle-like mullite formed from Microsilica additive.

E. Y. Sako - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolution of magnesia-based castables containing Microsilica
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract The higher performance of refractory materials applied in steelmaking vessels is mainly associated with the development of high-magnesia bricks. However, the same success has not yet been attained for the production of high-quality magnesia-based castables, due to the well-known magnesia hydration trend. In order to overcome this drawback, Microsilica addition was tested as an anti-hydration additive in the present work. As it also leads to liquid formation at high temperatures in high-alumina CAC-containing castable compositions, the microstructural development of Microsilica-containing magnesia-based castables was also analyzed by scanning electron microscopy, thermodynamics simulations and sintering assisted tests. According to the results, Microsilica hindered the magnesia hydration and provided an additional bonding mechanism due to the reaction with MgO and water. Moreover, it helped to control the material's volumetric change by reducing the expansion associated with the spinel formation and also the shrinkage level afterwards.

  • The corrosion resistance of Microsilica-containing Al2O3–MgO and Al2O3–spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

  • the corrosion resistance of Microsilica containing al2o3 mgo and al2o3 spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

Mariana A. L. Braulio - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolution of magnesia-based castables containing Microsilica
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract The higher performance of refractory materials applied in steelmaking vessels is mainly associated with the development of high-magnesia bricks. However, the same success has not yet been attained for the production of high-quality magnesia-based castables, due to the well-known magnesia hydration trend. In order to overcome this drawback, Microsilica addition was tested as an anti-hydration additive in the present work. As it also leads to liquid formation at high temperatures in high-alumina CAC-containing castable compositions, the microstructural development of Microsilica-containing magnesia-based castables was also analyzed by scanning electron microscopy, thermodynamics simulations and sintering assisted tests. According to the results, Microsilica hindered the magnesia hydration and provided an additional bonding mechanism due to the reaction with MgO and water. Moreover, it helped to control the material's volumetric change by reducing the expansion associated with the spinel formation and also the shrinkage level afterwards.

  • The corrosion resistance of Microsilica-containing Al2O3–MgO and Al2O3–spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

  • the corrosion resistance of Microsilica containing al2o3 mgo and al2o3 spinel castables
    Ceramics International, 2012
    Co-Authors: E. Y. Sako, Mariana A. L. Braulio, Victor C. Pandolfelli
    Abstract:

    Abstract Microsilica addition in Al2O3–MgO and Al2O3–spinel castables helps to improve their flowability and partially accommodate their residual expansion after firing. Nevertheless, there is a lack of conclusive statements in the literature regarding the effects of Microsilica on one of the main requisites for steel ladle refractories: corrosion resistance. In the present work, the performance of alumina–magnesia and alumina–spinel with or without Microsilica when in contact with a steel ladle slag was evaluated based on three aspects: the material's physical properties, its chemical composition and the microstructural features before the slag attack. According to the attained results, Microsilica induced liquid formation and pore growth during sintering, favoring the physical slag infiltration. Moreover, due to this liquid, CA6 was formed in the matrix, mainly for the Al2O3–spinel composition, which also favored the castable dissolution into the molten slag.

  • Microsilica or MgO grain size: Which one mostly affects the in situ spinel refractory castable expansion?
    Ceramics International, 2009
    Co-Authors: Mariana A. L. Braulio, P O Brant, L R M Bittencourt, Victor C. Pandolfelli
    Abstract:

    Microsilica is commonly added to alumina-magnesia castables to counterbalance the in situ spinel expansion. This effect is attained by the generation of a low-melting temperature phase, which also affects the expansive reaction kinetics. Additionally, the MgAl 2 O 4 formation depends on the grain size of the reactants. The use of coarse magnesia grains results in lower Mg 2+ dissolution and could lead, at 1500 °C, to forsterite development (Mg 2 SiO 4 ). For finer MgO, silica was detected at the edge of the spinel grains. Considering these aspects, this work evaluated the effect of Microsilica content for different magnesia grain sizes (

V C Pandolfelli - One of the best experts on this subject based on the ideXlab platform.

  • Microsilica or mgo grain size which one mostly affects the in situ spinel refractory castable expansion
    Ceramics International, 2009
    Co-Authors: M A L Braulio, P O Brant, L R M Bittencourt, V C Pandolfelli
    Abstract:

    Microsilica is commonly added to alumina-magnesia castables to counterbalance the in situ spinel expansion. This effect is attained by the generation of a low-melting temperature phase, which also affects the expansive reaction kinetics. Additionally, the MgAl 2 O 4 formation depends on the grain size of the reactants. The use of coarse magnesia grains results in lower Mg 2+ dissolution and could lead, at 1500 °C, to forsterite development (Mg 2 SiO 4 ). For finer MgO, silica was detected at the edge of the spinel grains. Considering these aspects, this work evaluated the effect of Microsilica content for different magnesia grain sizes (<45 or < 100 μm). Due to a faster spinel formation for the fine MgO source, Microsilica counterbalanced the MgA1 2 0 4 expansion. Conversely, for the coarser MgO, silica increased the Mg 2+ dissolution, speeding up the spinel formation and expansion. Therefore, Microsilica presented opposite roles, pointing out that it does not always counterbalance the spinel expansion. This work also indicated the need for a systemic approach for the expanding design of alumina―magnesia refractory castables.