Preparation and characterization of microporous mullite-corundum refractory aggregates with high strength and closed porosity

Qi, Jiangtao; Yan, Weiping; Chen, Zhe; Schafföner, Stefan; Zhou, Wenying; Li, Guangqiang; Wang, Qiang

doi:10.1016/j.ceramint.2019.12.056

Cited by 28 publications

(12 citation statements)

References 32 publications

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“…By decomposing carbonate, hydroxide, and silicate minerals in raw materials, generating gas, and removing water at high temperatures, in situ decomposition is one of the most prevalent methods of pore formation, 15 producing pores with small sizes and uniform distribution. For instance, Yan et al 16 used Al(OH) 3 and kaolin as raw materials to prepare microporous mullite-corundum refractory by in situ decomposition; the total porosity and median pore size were 40.5% and .74 μm, and the cold compressive strength (CCS) was as high as 103.2 MPa. Zhu et al 17 used bauxite and kaolin as the main raw materials, and using in situ decomposition of minerals such as diaspore and kaolinite to form micropores, microporous mullite materials with an average pore size of less than 1 μm and a flexural strength of 90-110 MPa could be prepared.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Preparation of microporous mullite refractories with high strength based on low‐grade bauxite and coal gangue

Chen,

Sang,

et al. 2023

Int J Applied Ceramic Tech

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For the energy‐saving and safe utilization of industrial furnaces, it is essential to develop refractories with low thermal conductivity and high strength. In this study, low‐grade bauxite and coal gangue were used as the main raw materials to prepare microporous mullite refractories with low thermal conductivity and high strength by the in situ decomposition method. The effect of coal gangue content and sintering temperature on the structure and properties of mullite refractories was also investigated. The results show that the average pore size of mullite refractories containing coal gangue is between 1.3 and 4.4 μm; with the addition of coal gangue, the apparent porosity of mullite refractories increases and their thermal conductivity decreases. Coal gangue reduces the number of pores larger than 14 μm, improves the microstructure uniformity of mullite refractories, and increases their cold compressive strength. The strength of microporous refractory treated at 1500°C containing 36.2% coal gangue as raw material is up to (105.6 ± 1.7 MPa); and its thermal conductivity tested at 1000°C is only .442 W/(m K)).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preparation of microporous mullite refractories with high strength based on low‐grade bauxite and coal gangue

Chen,

Sang,

et al. 2023

Int J Applied Ceramic Tech

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“…However, on the one hand, the porous mullite ceramics obtained in the previous work were mainly with open pores; on the other hand, the introduction of MgCO 3 and CaCO 3 additives promoted the production of more liquid phase at high temperature, which would affect the high‐temperature service performance. To avoid introducing more high‐temperature liquid phases, in the further study, 27 the effect of forming pressure on the microstructures and properties of porous mullite ceramics were studied without the introduction of additives. It was found that mullite‐corundum ceramics with total porosity of 40.5%, closed porosity of 16.2%, median pore diameter of .74 μm, and compressive strength of 103.2 MPa was obtained using 150 MPa pressure condition, which was suitable for lightweight mullite refractory aggregates.…”

Section: Introductionmentioning

confidence: 99%

Microstructures and properties of microporous mullite‐corundum aggregates for lightweight refractories

Wang

Yan

et al. 2022

Int J Applied Ceramic Tech

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Five microporous mullite-corundum refractory aggregates were prepared from Al(OH) 3 and kaolinite gangue through in situ decomposition synthesis technique. The effects of the sintering temperature (1400-1600 • C) and the particle sizes of raw materials (20.6-94.5 μm) on the microstructures and strengths of the aggregates were investigated through X-ray diffractometer, scanning electron microscopy, and energy-dispersive spectrometer etc., to find out the technological conditions to be controlled in industrial production. The higher sintering temperature promoted the reaction between Al(OH) 3 and kaolinite gangue, leading to the development of primary-mullite as well as the generation of secondary-mullite, which promoted the formation of the neck and improved the strength. Meanwhile, the dense mullite layers were formed continuously on the surface of Al(OH) 3 pseudomorphs, making the micropores inside the pseudomorphs become closed pores, which increased the closed porosity of the aggregates. The reduction of the particle sizes of raw materials changed the particle packing behavior, accelerated the rearrangement of the Al(OH) 3 pseudomorph particles during the process of reactive sintering, and then reduced the closed porosity. To realize the industrial production of microporous mullitecorundum refractory aggregate with high strength (103 MPa) and high closed porosity (16.1%), the sintering temperature should be at about 1600 • C, and the median diameter of raw materials should be at 94.5 μm.

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“…Concern about environmental issues around the world has grown in recent decades, especially in the academic community and research has strongly focused on the development of sustainable methods aimed at recycling inorganic waste [14][15][16][17][18][19][20][21][22][23][24] . Many studies have emphasized interest in the development of compositions suitable for the production of refractories coatings used in ovens.…”

Section: Introductionmentioning

confidence: 99%

Refractory Ceramics of Clay and Alumina Waste

et al. 2021

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Refractory ceramics were produced from clays and alumina waste. Specimens were shaped by uniaxial pressing, subjected to thermal analysis by dilatometry and heat-treated in a conventional furnace at 1300 and 1400ºC, applying a heating rate of 5ºC/min and a dwell time of 2 and 3 hours at the maximum temperature. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and physicomechanical properties. The dilatometric analysis before heat treatment indicated that the formulation containing the largest amount of fluxing oxides presented the highest linear shrinkage. The XRD analysis revealed that mullite was the major phase and needle shaped crystals typical of mullite obtained from clay minerals were observed by SEM. The increase in firing temperature and dwell time at the maximum temperature improved the physicomechanical properties of the specimens. The thermal expansion coefficient (TEC) in the range of 25 to 1000ºC varied from 6.2 to 6.9 x 10 -6°C-1 .

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Preparation and characterization of microporous mullite-corundum refractory aggregates with high strength and closed porosity

Cited by 28 publications

References 32 publications

Preparation of microporous mullite refractories with high strength based on low‐grade bauxite and coal gangue

Preparation of microporous mullite refractories with high strength based on low‐grade bauxite and coal gangue

Microstructures and properties of microporous mullite‐corundum aggregates for lightweight refractories

Refractory Ceramics of Clay and Alumina Waste

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