Characterisation and properties of low-conductivity microporous magnesia based aggregates with in-situ intergranular spinel phases

Zou, Yongshun; Gu, Huazhi; Huang, Ao; Huo, Yanzhu; Fu, Lvping; Li, Yawei

doi:10.1016/j.ceramint.2020.12.229

Cited by 32 publications

(9 citation statements)

References 36 publications

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“…Compared with these methods, the in-situ decomposition synthesis method is suitable for the large-scale manufacture of microporous MgO-Al 2 O 3 refractory aggregates with a simple process and environment-friendly. [33][34][35][36][37] For example, microporous spinel aggregates were prepared with magnesite and Al(OH) 3 , which gained a bulk density of 1.40-1.48 g/cm 3 , an apparent porosity of 58.2%-60.4% and a median pore size of 6.8-10.0 μm. 38 However, due to the impurity of raw material magnesite, a small amount of liquid phase promoted the merging and growth of nanopores in the magnesite pseudomorph particles.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Yan,

Wang

et al. 2023

Int J Applied Ceramic Tech

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In this work, microporous MgO–Al2O3 refractory aggregates were prepared with Mg(OH)2 and Al(OH)3 via the in situ decomposition synthesis method. The effect of Al(OH)3 addition on the microstructure and properties of microporous MgO–Al2O3 refractory aggregates was investigated with scanning electron microscope and mercury intrusion porosimetry. The results indicated that the improved green density of the samples and the reaction sintering accelerated the mass transport rate with adding Al(OH)3 from 0 to 4.0 wt%. Besides, a small amount of Al3+ diffused into porous MgO particles, accelerating the merging and growth of nanopores in the porous MgO particles. The intra‐particle pore size and the densification degree of microparticles were increased, and thus the strength of the samples was improved. Due to the formation of Kirkendall voids by interdiffusion of Mg2+ and Al3+, the inter‐particle pore size increased. Adding Al(OH)3 from 4.0 to 17.6 wt%, the Kirkendall voids weakened the mass transport rate and improved the inter‐particle pore size. The merging and growth of nanopores in the MgO particles were limited, resulting in the reduced intra‐particle pore size and increased intra‐particle pore number. The densification degree of microparticles was reduced, and thus the strength of the samples decreased. At the Al(OH)3 addition of 4.0 wt%, microporous MgO–Al2O3 refractory aggregates had the best comprehensive properties, a bulk density of 2.48 g/cm3, an apparent porosity of 29.4%, a median pore size of 1.6 μm with 42.2 vol% nanopores and the thermal conductivity of 4.0 W/(m K).

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Section: Introductionmentioning

confidence: 99%

Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Yan,

Wang

et al. 2023

Int J Applied Ceramic Tech

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“…Currently, lightweight refractories for working lining have been widely studied. [20][21][22][23][24][25] Generally, microporous aggregates can be obtained by crushing and screening porous ceramics. [26][27][28][29][30][31][32] At present, porous MgO-Al 2 O 3 ceramics can be produced not only by the template method, 33 but also by direct foam gelcasting, 34 in situ decomposition synthesis.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, the design of lightweight and low conductivity working linings with refractories containing microporous aggregates 15–19 was proposed to reduce their thermal conductivity. Currently, lightweight refractories for working lining have been widely studied 20–25 …”

Section: Introductionmentioning

confidence: 99%

Microstructures and strengths of microporous MgO–Al₂O₃ ceramics from Al(OH)₃ and calcined magnesite

Chen

Yan

et al. 2022

J Am Ceram Soc.

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Seven microporous MgO-Al 2 O 3 ceramics with an Al 2 O 3 content of 15-90 wt% were prepared using Al(OH) 3 and calcined magnesite as raw materials. A wet mixing process was employed during sample preparation to transform the calcined magnesite with a larger particle size to smaller Mg(OH) 2 particles. The in situ decomposition synthesis method and the Kirkendall effect were utilized to produce and control the pore structure of the microporous MgO-Al 2 O 3 ceramics. There were two kinds of pores in the microporous MgO-Al 2 O 3 ceramics. The first one resulted from the in situ decomposition of Al(OH) 3 and Mg(OH) 2 particles, which were small and equally distributed. Another one originated from the position of the Mg(OH) 2 particles due to the Kirkendall effect caused by MgO diffusion. They were similar in size to the Mg(OH) 2 pseudomorph particles. Simultaneously, the Al 2 O 3 content affected the packing behavior and the spinel formation, which changed the characteristics of the pores and necks among the particles. These mechanisms also affected the strengths of the microporous MgO-Al 2 O 3 ceramics. Thus, when the Al 2 O 3 content was 45-90 wt%, the microporous MgO-Al 2 O 3 ceramics had a high compressive strength (10.0-18.3 MPa) and apparent porosity (52.2%-58.4%).

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“…[11][12][13] In order to make a trade-off between thermal conductivity and slag resistance, much effort has been put into the optimization and development of lightweight aggregates, such as the increase of closed porosity and the homogenization and nanocrystallization of pore size. [14][15][16][17] At the same time, the preparation of lightweight refractory bricks possessing gradient density provides the academic world and the industrial world another path to realize the lightweight refractory. [18][19][20] In our previous studies, the refractory with density-gradient structure has been proved that it has guaranteed mechanical and slag resistance compared to dense one.…”

Section: Introductionmentioning

confidence: 99%

Effect of CaCO₃ addition on the performance of lightweight Al₂O₃‐MgAl₂O₄ refractories with gradient density

Gao

Yin

Xin

et al. 2022

Int J Applied Ceramic Tech

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In this study, to improve the comprehensive performance of lightweight Al 2 O 3 -MgAl 2 O 4 refractories with gradient density, CaCO 3 was added in the matrix to develop platelet structures by adding different amounts (1, 2, 3, and 4 wt%).The effect of CaCO 3 addition on the phase composition, microstructure, and properties of lightweight refractories was investigated. The results showed that CaO⋅6Al 2 O 3 and Ca 2 Mg 2 Al 28 O 46 formed. Meanwhile, platelet structure is distributed at the junction between aggregate and matrix. With the increase of CaCO 3 content, although there were no apparent changes in apparent porosity and bulk density, both the compressive strength and refractoriness under load improved significantly. Furthermore, the results of three-point bending tests showed thermal shock resistance was improved in terms of the value of residual strength ratio from 14.2% to 22.5% for specimens before and after 4 wt% CaCO 3 addition. The findings showed that the introduction of CaCO 3 is feasible and effective for performance improvements of lightweight refractories.

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Characterisation and properties of low-conductivity microporous magnesia based aggregates with in-situ intergranular spinel phases

Cited by 32 publications

References 36 publications

Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Microstructures and strengths of microporous MgO–Al₂O₃ ceramics from Al(OH)₃ and calcined magnesite

Effect of CaCO₃ addition on the performance of lightweight Al₂O₃‐MgAl₂O₄ refractories with gradient density

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Characterisation and properties of low-conductivity microporous magnesia based aggregates with in-situ intergranular spinel phases

Cited by 32 publications

References 36 publications

Microstructure and properties of microporous MgO–Al2O3 refractory aggregates from Mg(OH)2 and Al(OH)3

Microstructure and properties of microporous MgO–Al2O3 refractory aggregates from Mg(OH)2 and Al(OH)3

Microstructures and strengths of microporous MgO–Al2O3 ceramics from Al(OH)3 and calcined magnesite

Effect of CaCO3 addition on the performance of lightweight Al2O3‐MgAl2O4 refractories with gradient density

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Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Microstructure and properties of microporous MgO–Al₂O₃ refractory aggregates from Mg(OH)₂ and Al(OH)₃

Microstructures and strengths of microporous MgO–Al₂O₃ ceramics from Al(OH)₃ and calcined magnesite

Effect of CaCO₃ addition on the performance of lightweight Al₂O₃‐MgAl₂O₄ refractories with gradient density