Microstructure and mechanical properties of cold sintered porous alumina ceramics

Suleiman, B.; Zhang, Hongtao; Ding, Yulong; Li, Yongliang

doi:10.1016/j.ceramint.2022.01.232

Cited by 15 publications

(3 citation statements)

References 51 publications

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“…Kang et al [28] performed CSP of mixed γ-and α-Al2O3 in a medium of glacial acetic acid at 300 °C and 300 MPa for 1 h. The PHT above 1250 °C led to highly dense α-Al2O3 ceramics. Suleiman et al [29] applied CSP for the compaction of Al2O3-NaCl composites which transformed into porous alumina ceramics on PHT at 1200-1500 °C for 30 min. Later, Gao et al [30] demonstrated a direct preparation of γ-Al2O3 translucent ceramics by the CSP in 10 M NaOH at 350 °C and 500 MPa without a need of PHT.…”

Section: Preprintsmentioning

confidence: 99%

Direct Cold Sintering of α-Al2O3 Ceramics in a Pure Water Medium

Kholodkova,

Kornyushin,

Khrustalev

et al. 2024

Preprint

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Porous α-Al2O3 ceramics is a highly demanded material for multitude applications such as filters, substrates, biomedicine materials, etc. Despite the availability of the raw materials, a challenge of their technology is in a high energy budget caused by the sintering above 1500 °C. For a cold sintering processing (CSP) of ceramics, the lowering of α-Al2O3 sintering temperature is one of the most urgent challenges at the background of its rapid development. The current paper for the first time demonstrates the solution of the mentioned problem by the CSP of α-alumina ceramics in a presence of pure water as a transient liquid. The manufactured materials were examined by XRD analysis; the evolution of their microstructures during the CSP was revealed by SEM, and the porosity evaluated by the Archimedes method. The ceramics with an open porosity up to 36 % was produced at 380-450 °C, 220 MPa in 30 min. An increase in the pressure was found to impede α-Al2O3 formation from γ-AlOOH. The development of the microstructure was discussed within the frameworks of the dissolution-precipitation model and the homogenous nucleation. The results of the SEM study pointed to the coalescence of γ-AlOOH grains during the CSP.

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Section: Preprintsmentioning

confidence: 99%

Direct Cold Sintering of α-Al2O3 Ceramics in a Pure Water Medium

Kholodkova,

Kornyushin,

Khrustalev

et al. 2024

Preprint

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“…Recently, the cold sintering process (CSP), featuring energy-saving and low CO 2 emission properties [ 19 ], was utilized to prepare porous ceramic materials. For instance, porous alumina ceramics with uniform structures were fabricated with NaCl as the pore-forming agent [ 20 ] using CSP and the post-annealing technique. Microporous TiO 2 materials were prepared through CSP associated with the post-annealing technique [ 21 ], using thermoplastic polymer beads as sacrificial templates.…”

Section: Introductionmentioning

confidence: 99%

Porous Lithium Disilicate Glass–Ceramics Prepared by Cold Sintering Process Associated with Post-Annealing Technique

Lyu,

Seo,

Han

et al. 2024

Materials

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Using melt-derived LD glass powders and 5–20 M NaOH solutions, porous lithium disilicate (Li2Si2O5, LD) glass–ceramics were prepared by the cold sintering process (CSP) associated with the post-annealing technique. In this novel technique, H2O vapor originating from condensation reactions between residual Si–OH groups in cold-sintered LD glasses played the role of a foaming agent. With the increasing concentration of NaOH solutions, many more residual Si–OH groups appeared, and then rising trends in number as well as size were found for spherical pores formed in the resultant porous LD glass–ceramics. Correspondingly, the total porosities and average pore sizes varied from 25.6 ± 1.3% to 48.6 ± 1.9% and from 1.89 ± 0.68 μm to 13.40 ± 10.27 μm, respectively. Meanwhile, both the volume fractions and average aspect ratios of precipitated LD crystals within their pore walls presented progressively increasing tendencies, ranging from 55.75% to 76.85% and from 4.18 to 6.53, respectively. Young’s modulus and the hardness of pore walls for resultant porous LD glass–ceramics presented remarkable enhancement from 56.9 ± 2.5 GPa to 79.1 ± 2.1 GPa and from 4.6 ± 0.9 GPa to 8.1 ± 0.8 GPa, whereas their biaxial flexural strengths dropped from 152.0 ± 6.8 MPa to 77.4 ± 5.4 MPa. Using H2O vapor as a foaming agent, this work reveals that CSP associated with the post-annealing technique is a feasible and eco-friendly methodology by which to prepare porous glass–ceramics.

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“…The specific processing methods used in the fabrication of porous ceramics ultimately dictate the final physical attributes and microstructure of the material, which includes factors, such as the size, shape, and percentage of open versus closed cells, as well as the size and distribution of interconnections between cells, the density of struts connecting cells, and the percentage of total porosity (TP). 11 Typically, the fabrication of porous ceramic involves a direct sacrificial template method, 12,13 polymeric replication technique, 14 foaming method, 15 reaction sintering, 16 and so forth. Recently, the freeze casting method, 17 sol-gel method, 18,19 and additive manufacturing 20 technique also emerged as easy fabrication routes for the development of porous ceramic.…”

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confidence: 99%

Alumina dissolution process to fabricate bimodal pore architecture alumina with superior green and sintered properties

2023

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Herein, a straightforward, adaptable, and cost‐effective approach has been proposed to realize the concept of dissolution of alumina in acidic aqueous media to fabricate porous alumina showing exceptional green machining properties and exhibiting good thermomechanical properties through in situ generated blowing agents and thermo‐foaming process. The process involves dissolving alumina in concentrated sulfuric acid to generate aluminum hydroxide and aluminum sulfate, which act as blowing agents to produce pores in the final structure through a decomposition process at elevated temperatures. By varying the concentration of deionized water and acidification using sulfuric acid, different alumina slurries are prepared. Sintering shrinkage is well countered through simultaneous consolidation and decomposition process during the heat treatment, and a minimum shrinkage of 0.88% is achieved. In addition to its pore‐forming properties, aluminum sulfate also provides strong binding effects to green bodies, contributing to their exceptional green machining properties. The resulting porous alumina exhibits a green flexural strength of up to 17 MPa, making it capable of bearing loads and forces during green machining. The sintered porous alumina fabricated in the study has a porosity range of 34.43%–59.24% and a flexural strength of 27.84–53.21 MPa. The prepared porous alumina also exhibits satisfactory thermal resistivity, with a minimum thermal conductivity of 1.23 W/m K, and has intra/intergranular space in the nano range. The coexistence of a combination of bimodal pores in a single monolithic matrix makes it exceptionally porous and suitable for an extensive spectrum of applications.

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Microstructure and mechanical properties of cold sintered porous alumina ceramics

Cited by 15 publications

References 51 publications

Direct Cold Sintering of α-Al<sub>2</sub>O<sub>3</sub> Ceramics in a Pure Water Medium

Direct Cold Sintering of α-Al<sub>2</sub>O<sub>3</sub> Ceramics in a Pure Water Medium

Porous Lithium Disilicate Glass–Ceramics Prepared by Cold Sintering Process Associated with Post-Annealing Technique

Alumina dissolution process to fabricate bimodal pore architecture alumina with superior green and sintered properties

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