Effects of foaming temperature on the preparation and microstructure of alumina foams

Huang, Keke; Li, Yuanbing; Zhao, Yi; Li, Shujing; Li, Yawei; Sang, Shaobai

doi:10.1016/j.matlet.2015.11.097

Cited by 17 publications

(6 citation statements)

References 10 publications

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“…As a result, these materials find an increasing demand for use in relevant applications where such a combination of properties is mandatory or more efficient than other alternatives. Examples include high-temperature insulation, molten metal and hot corrosive gas and liquid filtration, catalyst supports, biomaterials, metal and polymer matrix composites, absorbents, chemical sensors, electrodes for fuel cells, lightweight structural materials, and gas combustion burners [1][2][3][4][5]. Several routes for the creation of pores inside ceramics can be found in the literature.…”

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of porous alumina ceramics using sunflower seed shells as fugitive material

Alzukaimi

Jabrah

2020

Cerâmica

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Porous alumina ceramics were prepared through the space holder technique, using ground sunflower seed shells as a fugitive material and uniaxial pressing for forming the green ceramics. Influences of the sunflower seed shell content on the shrinkage of the green bodies and porosity of sintered products were evaluated. The prepared ceramics were characterized for mechanical properties using the Brazilian disk test, and the porosity effect on the measured strength was determined. The microstructure was characterized by SEM. The sunflower seed shell content was varied from 0 to 60 wt%. Porosities within 29.9-71.0 vol% were achieved, and the strength of the obtained alumina ceramics decreased accordingly from 59.7 to 4.0 MPa. Additional samples, prepared with different compaction pressure, were characterized for electrical properties and showed high electrical insulation capability, which increased with porosity. Mechanical and electrical data were discussed based on theoretical models, namely the Gibson-Ashby model and/or the minimum solid area model.

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Section: Introductionmentioning

confidence: 99%

Preparation and characterization of porous alumina ceramics using sunflower seed shells as fugitive material

Alzukaimi

Jabrah

2020

Cerâmica

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“…8,9 Numerous experimental and analytical results have demonstrated that to reduce the thermal conductivity, closure and spheroidization of pore shape, randomization of pore distribution as well as miniaturization of pore size are the optimal methods to achieve balance between thermal conductivity and strength when the porosity is constant (range of increase in porosity is limited). [9][10][11] Thus far, compared with freeze casting 12 or direct foaming, 2,8 slurry gelation and foaming, 13 and other foaming methods, 14 the use of pore-forming agents which can dominate the shape, size, and amount of pores in porous materials by choosing suitable pore-forming agents type, size, and incorporation content 15 is still the most common used method to produce porous ceramics with porosity not more than 70%. 16 A wide variety of pore-forming agents such as coffee grounds, bioactive yeast, polystyrene sphere (PS), poppy seed, corn cob, and activated carbon 4,[17][18][19][20][21] had been employed for preparing porous ceramics.…”

Section: Introductionmentioning

confidence: 99%

“…Thus far, compared with freeze casting 12 or direct foaming, 2,8 slurry gelation and foaming, 13 and other foaming methods, 14 the use of pore‐forming agents which can dominate the shape, size, and amount of pores in porous materials by choosing suitable pore‐forming agents type, size, and incorporation content 15 is still the most common used method to produce porous ceramics with porosity not more than 70% 16 . A wide variety of pore‐forming agents such as coffee grounds, bioactive yeast, polystyrene sphere (PS), poppy seed, corn cob, and activated carbon 4,17‐21 had been employed for preparing porous ceramics.…”

Section: Introductionmentioning

confidence: 99%

Preparation of high‐strength lightweight alumina with plant‐derived pore using corn stalk as pore‐forming agent

et al. 2020

Int J Applied Ceramic Tech

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To improve the mechanical and thermal insulation properties of lightweight alumina, which was prepared by using pore‐forming agent from biological sources, the silica sol‐infiltrated corn stalk was utilized. Spring back and hygroscopicity of corn stalk powder as well as cold compressive strength, thermal conductivity, microstructure, and pore size distribution of lightweight alumina were characterized. The results indicate that impregnation of silica sol leads to different degrees of decrease in spring back height due to achieving better mesh by silica gel between the corn stalk powders, and then improves the formability, although at the same time the large number of hydrophilic groups results in an increase in hygroscopicity. Furthermore, sol impregnated pore‐forming agent optimizes the microstructure of the lightweight alumina pores. Lightweight alumina with a cold compressive strength up to 48.64 MPa was produced, and with the silica sol concentration of 3 wt%, lower thermal conductivity values at all test temperatures were obtained. Hence, the use of corn stalk impregnated with the appropriate concentration of silica sol as pore‐forming agent could enhance the mechanical and thermal insulation properties of lightweight alumina for the spheroidization of pore shape, randomization of pore distribution as well as miniaturization of pore size.

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“…In direct foaming methods, foam structures are created in situ by the formation of gas during a chemical reaction, accompanied by a liquid–solid transformation process, e.g., a polymerization . Burnout of sacrificial filler materials can also create foamed structures in originally dense solids .…”

Section: Introductionmentioning

confidence: 99%

Reticulated Alumina Replica Foams with Additional Sub‐Micrometer Strut Porosity

et al. 2019

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Ceramic alumina foams are suitable catalyst supports with high temperature stability used, for example, in catalytic cracking processes or combined heat and power units. Herein, such replica foams are generated from macroporous α‐Al2O3 powder synthesized by a sol–gel process. The foam windows, constituting intrinsic (macroscopic) foam porosity, are supplemented by an additional porosity within the struts of the foams. These pores, originating from the sol–gel process, are preserved during sintering at 1350 °C. This results in less dense foams compared with foams from conventional alumina powders. Foams sintered at 1350 °C exhibit an increased strut porosity of ≈62%, of which ≈84% are open, with pore diameters in the range of 200–500 nm and a compressive strength of 0.2 MPa. Foams sintered at 1600 °C or higher possess an almost tenfold compressive strength but no additional strut porosity. Due to the use of carboxylic acids as porogenes in the sol–gel process, all samples generated from sol–gel‐derived alumina powder exhibit significantly higher porosity values than the respective reference foams made from commercial alumina powder. Although specific surface areas of ≈3 m2 g−1 are still small, this value is significantly improved by additional strut porosity.

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Effects of foaming temperature on the preparation and microstructure of alumina foams

Cited by 17 publications

References 10 publications

Preparation and characterization of porous alumina ceramics using sunflower seed shells as fugitive material

Preparation and characterization of porous alumina ceramics using sunflower seed shells as fugitive material

Preparation of high‐strength lightweight alumina with plant‐derived pore using corn stalk as pore‐forming agent

Reticulated Alumina Replica Foams with Additional Sub‐Micrometer Strut Porosity

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