Chrome-free qandilite (Mg2TiO4) refractory aggregates: Role of titania source and evaluation of thermal expansion coefficient

Somnath Mandal; James G. Hemrick; Manoj K. Mahapatra

doi:10.1016/j.jeurceramsoc.2022.08.012

Chrome-free qandilite (Mg₂TiO₄) refractory aggregates: Role of titania source and evaluation of thermal expansion coefficient

Somnath Mandal, James G. Hemrick, Manoj K. Mahapatra

Mechanical Properties and Mechanics

Research output: Contribution to journal › Article › peer-review

14 Scopus citations

Abstract

As used chrome-based refractories may contain toxic Cr⁶⁺, the chrome-free Mg₂TiO₄ phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg₂TiO₄ formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1 % versus 7.2 %) and the reaction occurred earlier (965 ℃ compared to 1120 ℃). After sintering at 1,600 ℃, rutile produced an aggregate with 3.8 % open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24 g/cm³ with a thermal expansion coefficient (70–1,600 ℃) of 13.5 × 10⁻⁶ K⁻¹. Moreover, replacing rutile by anatase eliminates the undesirable MgTiO₃ phase. The anatase-based aggregate consisted of a Mg₂TiO₄ matrix with residual unreacted MgO and an intergranular, refractory CaTiO₃ phase. The rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO₃.

Original language	English
Pages (from-to)	7343-7351
Number of pages	9
Journal	Journal of the European Ceramic Society
Volume	42
Issue number	15
DOIs	https://doi.org/10.1016/j.jeurceramsoc.2022.08.012
State	Published - Dec 2022

Funding

The US Department of Energy ( Advanced Manufacturing Office , AMO) funded this work (grant number: DE-EE0001761 ). The authors are grateful to Mr. Glenn McIntyre (HarbisonWalker International) and Mr. Tony Free (Tronox) for generously providing raw materials along with chemical composition and particle size analysis report. The authors appreciate the helpful suggestions from Dr. Gregory Kubacki (University of Alabama at Tuscaloosa), and are thankful to Dr. David Mitchell, Dr. Hong Wang, Dr. Michael Lance, and Dr. Bruce Pint at Oak Ridge National Laboratory for meticulously reviewing the manuscript. The US Department of Energy (Advanced Manufacturing Office, AMO) funded this work (grant number: DE-EE0001761). The authors are grateful to Mr. Glenn McIntyre (HarbisonWalker International) and Mr. Tony Free (Tronox) for generously providing raw materials along with chemical composition and particle size analysis report. The authors appreciate the helpful suggestions from Dr. Gregory Kubacki (University of Alabama at Tuscaloosa), and are thankful to Dr. David Mitchell, Dr. Hong Wang, Dr. Michael Lance, and Dr. Bruce Pint at Oak Ridge National Laboratory for meticulously reviewing the manuscript.

Funders	Funder number
U.S. Department of Energy	DE-EE0001761
University of Alabama

Keywords

Qandilite
Refractories
Sintering
Thermal expansion
Titania

Access to Document

10.1016/j.jeurceramsoc.2022.08.012

Cite this

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title = "Chrome-free qandilite (Mg2TiO4) refractory aggregates: Role of titania source and evaluation of thermal expansion coefficient",

abstract = "As used chrome-based refractories may contain toxic Cr6+, the chrome-free Mg2TiO4 phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg2TiO4 formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1 % versus 7.2 %) and the reaction occurred earlier (965 ℃ compared to 1120 ℃). After sintering at 1,600 ℃, rutile produced an aggregate with 3.8 % open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24 g/cm3 with a thermal expansion coefficient (70–1,600 ℃) of 13.5 × 10−6 K−1. Moreover, replacing rutile by anatase eliminates the undesirable MgTiO3 phase. The anatase-based aggregate consisted of a Mg2TiO4 matrix with residual unreacted MgO and an intergranular, refractory CaTiO3 phase. The rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO3.",

keywords = "Qandilite, Refractories, Sintering, Thermal expansion, Titania",

author = "Somnath Mandal and Hemrick, {James G.} and Mahapatra, {Manoj K.}",

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AU - Hemrick, James G.

AU - Mahapatra, Manoj K.

PY - 2022/12

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N2 - As used chrome-based refractories may contain toxic Cr6+, the chrome-free Mg2TiO4 phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg2TiO4 formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1 % versus 7.2 %) and the reaction occurred earlier (965 ℃ compared to 1120 ℃). After sintering at 1,600 ℃, rutile produced an aggregate with 3.8 % open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24 g/cm3 with a thermal expansion coefficient (70–1,600 ℃) of 13.5 × 10−6 K−1. Moreover, replacing rutile by anatase eliminates the undesirable MgTiO3 phase. The anatase-based aggregate consisted of a Mg2TiO4 matrix with residual unreacted MgO and an intergranular, refractory CaTiO3 phase. The rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO3.

AB - As used chrome-based refractories may contain toxic Cr6+, the chrome-free Mg2TiO4 phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg2TiO4 formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1 % versus 7.2 %) and the reaction occurred earlier (965 ℃ compared to 1120 ℃). After sintering at 1,600 ℃, rutile produced an aggregate with 3.8 % open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24 g/cm3 with a thermal expansion coefficient (70–1,600 ℃) of 13.5 × 10−6 K−1. Moreover, replacing rutile by anatase eliminates the undesirable MgTiO3 phase. The anatase-based aggregate consisted of a Mg2TiO4 matrix with residual unreacted MgO and an intergranular, refractory CaTiO3 phase. The rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO3.

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