Fabrication and analysis of lightweight magnesia based aggregates containing nano-sized intracrystalline pores

Zou, Yongshun; Gu, Huazhi; Huang, Ao; Fu, Lvping; Li, Guangqiang

doi:10.1016/j.matdes.2019.108326

Cited by 39 publications

(10 citation statements)

References 21 publications

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“…It should be pointed out that the sintering profile was determined from our previous study on firing the green body of magnesite. [20] At the sintered temperature 1780°C, the sintered magnesia could obtain the relatively low apparent porosity while high closed porosity.…”

Section: B Sample Preparationmentioning

confidence: 96%

“…The measured physical properties and grain sizes indicate that the addition of nano-sized ZrO 2 also promoted the sintering of S2, S3, and S4. In our previous publications, [20] the promoting effect on sintering was considered in the following three aspects:…”

Section: The Effect Of Intergranular Phases On Physical Propertiesmentioning

confidence: 99%

“…It should be mentioned that ZrO 2 is also one of the most commonly used additives in the fabrication of magnesia aggregates. [18][19][20][21] Many previous works have proposed that the addition of ZrO 2 not only improves the sintering of magnesia aggregates by intensifying secondary liquid phase formation and promoting diffusion through vacancy creation, [18][19][20] but also enhances their mechanical strength and thermal shock resistance by adjusting their microstructure. [21,22] For instance, Ghosh et al [19] demonstrated that a 3 wt pct-addition of ZrO 2 utilized the CaO in magnesite for tetragonal stabilization, which reduced the formation of the CMS phase and improved its strength.…”

Section: Introductionmentioning

confidence: 99%

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Formation Mechanism of In Situ Intergranular CaZrO3 Phases in Sintered Magnesia Refractories

Zou

Huang

et al. 2020

Metall Mater Trans A

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Sintered magnesia refractories combined by in situ intergranular CaZrO 3 phases were synthesized using natural MgO-containing natural minerals with CaO and SiO 2 impurities and nano-sized ZrO 2 additive. A homogenous distribution of intergranular CaZrO 3 , independent from the intergranular CaO-MgO-SiO 2 phases, was formed in situ within the sintered magnesia aggregates by introducing 0.75 wt pct nano-sized ZrO 2 into the magnesite. The formation mechanism of the in situ intergranular CaZrO 3 phases was determined. The nano-sized ZrO 2 was introduced and uniformly distributed at grain boundaries of the magnesia due to the micron-nano-sized particles composite system and wetting grinding process. Then the CaO in impurities were prior to SiO 2 to react with the ZrO 2 for generating CaZrO 3 at the grain boundaries by increasing sintering temperature. Nevertheless, the nano-sized ZrO 2 particles were encapsulated in the MgO crystallites with similar particle size decomposed from brucite and prevented from reacting with CaO impurities in magnesite. The mixing homogeneity of magnesite particles and ZrO 2 particles and the direct contact between ZrO 2 and CaO impurities in magnesite has a crucial effect on the formation of intergranular CaZrO 3 phases. Furthermore, the intergranular CaZrO 3 phases could enhance the bonding of magnesia grains and have great potential for improving the service performance of magnesia.

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Section: B Sample Preparationmentioning

confidence: 96%

Section: The Effect Of Intergranular Phases On Physical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation Mechanism of In Situ Intergranular CaZrO3 Phases in Sintered Magnesia Refractories

Zou

Huang

et al. 2020

Metall Mater Trans A

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“…Therefore, numerous researches focused on more accurate control to the size and the distribution of the pores in the lightweight refractory, and the lightweight refractory containing micropores was obtained. [ 7–9 ] The micropore size in this type of lightweight refractory is from tens of nanometers to several microns, and most of micropores locate inside the grain. In addition to the excellent thermal insulation and the lower density, the lightweight refractory containing micropores also possesses other superiorities even better than dense refractory, such as the higher mechanical strength, [ 10 ] the better thermal resistance, and the stronger slag resistance.…”

Section: Introductionmentioning

confidence: 99%

Corrosion Behavior of Lightweight MgO in High Basicity Tundish Slag

Tan

Liu

et al. 2021

steel research int.

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Demand for energy saving in steelmaking process, lightweight refractories have attracted great attentions for the excellent thermal insulation. Herein, the corrosion behavior of the lightweight magnesia in the high basicity tundish slag is explored, and compared with that of fused magnesia. The results show that the impurities in the fused magnesia cause more dissolution of magnesia into slag after 60 min. Different from fused magnesia, the penetration layer is found in the lightweight magnesia, where the intercrystalline CaZrO3–ZrO2 phases are dissolved by the slag. The micropores in the lightweight magnesia provide passages for slag infiltration, but also accelerate the supersaturation of slag in refractory and impede the mass transfer. Furthermore, the residual CaZrO3–ZrO2 phases in transition layer hinder the further slag infiltration. After 60 min holding, the MgO content in molten slag contacted with lightweight magnesia is lower, implying that the lightweight magnesia is the promising refractory for tundish lining.

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“…Du et al developed a high-porosity silicon nitride ceramic by the direct foaming method. Its porosity reached 92%-97%, but its compression strength was only 0.85-5.38 MPa [9]; Zou et al added nanometer aluminium oxide and zirconium oxide to prepare a nanoaperture magnesium oxide aggregate with a bulk density of 3.37 g/ cm 3 and a closed porosity of 4.3% [10]; Wu et al used magnesia lightweight aggregate to produce insulation materials, and the apparent porosity of the sample was 27.8% after sintering, and the compression strength was 68.4 MPa [11]; Obada et al prepared a ceramic membrane with enlarged pore by using ceramic clay and foaming agent PHDPE and found that the porosity reached 62% and the compression strength did not exceed 18 MPa [12]. e pore structure and the distribution in the material will directly affect the performance of the material.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Magnesia Insulation Materials by Calcination of Walnut Shell Powder by Silica Sol Impregnation

Kang

Han

et al. 2021

Advances in Materials Science and Engineering

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In this paper, magnesia porous aggregate was prepared by the foaming method with potassium oleate as the foaming agent. Secondly, the walnut shell powder was impregnated with the silica sol as the pore forming agent, and then, a new magnesia insulation material was prepared by 1300°C sintering. By changing the amount of the walnut shell powder added, the mechanical properties and thermal properties of the materials after sintering were studied. The results show that the sample with 10% walnut shell powder impregnated without the silica sol has a compression strength of 12 MPa. A sample with 10% walnut shell powder treated with the silica sol has a compression strength of 18 MPa. With the increase in the amount of the walnut shell powder added after impregnation, the bulk density, compression strength, and thermal conductivity of the sample all showed a decreasing trend, and the apparent porosity showed an increasing trend. When the additive amount is 20%, the bulk density of the sample is 1.029 g/cm3, and the thermal conductivity is 0.382 W/m K (1050°C).

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Fabrication and analysis of lightweight magnesia based aggregates containing nano-sized intracrystalline pores

Cited by 39 publications

References 21 publications

Formation Mechanism of In Situ Intergranular CaZrO3 Phases in Sintered Magnesia Refractories

Formation Mechanism of In Situ Intergranular CaZrO3 Phases in Sintered Magnesia Refractories

Corrosion Behavior of Lightweight MgO in High Basicity Tundish Slag

Preparation of Magnesia Insulation Materials by Calcination of Walnut Shell Powder by Silica Sol Impregnation

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