The influence of Fe2O3 doping on the pore structure and mechanical strength of TiO2-containing alumina obtained by freeze-casting

Silva, Alysson M.A.; Nunes, Eduardo H.M.; Souza, Douglas F.; Martens, Dana L.; Costa, João C. Diniz da; Houmard, Manuel; Vasconcelos, Wander L.

doi:10.1016/j.ceramint.2015.07.021

Cited by 21 publications

(4 citation statements)

References 56 publications

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“…In this process, the particles spread out, binding to each other, reducing the curvature or filling material internal pores, leading to a reduction in its open porosity. However, reduction of surface free energy of the system can occur through the increase in grain size by the coarsening mechanism, in which both pores and particles become larger 37–39 . Regarding longer sintering times, as appears to have occurred with the sample NC_Hypo_3 h, sintering results in significant growth of α‐Al 2 O 3 grains and decreased open pores.…”

Section: Resultsmentioning

confidence: 95%

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Role of solvent composition and sintering time on the porosity of α‐alumina monoliths produced by freeze casting

da Silva,

de Faria,

dos Santos

et al. 2024

J Am Ceram Soc.

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The present study reports the investigation of the influence of naphthalene–camphor binary solvent and the densification process on the pore structure formation of α‐alumina monoliths using the freeze‐casting technique with a freezing temperature control mechanism. Freeze‐casting technique allowed a controlled production of monoliths with high porosity (65%–70%) and distinct pore morphologies based on the adjustment of solvent composition (hypoeutectic, eutectic, and hypereutectic) and sintering time. In general, the longer the sintering time, the greater the average pore diameter (8–10 µm), the larger the grain size (∼319–596 nm), the higher the material density (∼1450–1650 kg/m3), the lower the open porosity (∼60%–49%), the higher the closed porosity (5%–18%), and the greater the compressive strength of the monoliths (hypoeutectic: 23.56 MPa; eutectic: 4.81 MPa; hypereutectic: 23.49 MPa). The study also reveals that the solvent composition directly influenced the alignment of the pore structure, as the pores of the final monolith resemble frozen solvent crystals. Hydraulic tortuosity varied from 1.30 to 1.53 for selected samples. Finally, solvent composition and sintering time proved to be important parameters that should be considered in the manufacturing process of porous ceramic structures via freeze casting.

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Section: Resultsmentioning

confidence: 95%

“…However, reduction of surface free energy of the system can occur through the increase in grain size by the coarsening mechanism, in which both pores and particles become larger. [37][38][39] within the material. 34 The result is a further increase in the material porosity as seen in Figure 9.…”

Section: F I G U R Ementioning

confidence: 99%

Role of solvent composition and sintering time on the porosity of α‐alumina monoliths produced by freeze casting

da Silva,

de Faria,

dos Santos

et al. 2024

J Am Ceram Soc.

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“…1,11,12 To control the material parameters, various dopants have been introduced, including Cr 2 O 3 , 9 MnO 2 , 10 TiO 2 , 13 MgO, 14 SiO 2 , 15 and Fe 2 O 3 . 16 Among them, Cr 2 O 3 and MgO are known to be effective in promoting densification and are believed to be effective in freeze-cast porous systems with sufficiently thick layer thicknesses according to previous studies. 5 The indicator of densification is the density, which directly influences the mechanical strength according to a well-known equation.…”

Section: Introductionmentioning

confidence: 96%

“…To achieve these benefits, both a general treatment such as the introduction of dopants, and optimization of the sintering parameters can be utilized in bulk systems 1,11,12 . To control the material parameters, various dopants have been introduced, including Cr 2 O 3 , 9 MnO 2 , 10 TiO 2 , 13 MgO, 14 SiO 2 , 15 and Fe 2 O 3 16 . Among them, Cr 2 O 3 and MgO are known to be effective in promoting densification and are believed to be effective in freeze‐cast porous systems with sufficiently thick layer thicknesses according to previous studies 5 .…”

Section: Introductionmentioning

confidence: 99%

Enhanced compressive strength of porous alumina realized by synergy between La‐doping and two‐step sintering

Kim,

Woo,

Hong

et al. 2024

J Am Ceram Soc.

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Sintering phenomena, densification, and grain growth are crucial for proper control of the microstructure for good mechanical strength. Here, materials and processing parameters, the addition of La2O3, and two‐step sintering (TSS) were combined to lead to higher strength in the porous alumina prepared by freeze‐casting. Based on grain growth and densification behaviors with the La2O3 doping, a beneficial thermal profile was designed for the TSS. As a result, higher relative density levels and smaller grain size were obtained compared with the results with conventional sintering (CS): 38.56% and 0.82 µm at 1500°C by CS; 40.78% and 1.78 µm at 1600°C by CS; 41.43% and 0.87 µm by TSS. The microstructural benefits provided ∼1.4 times higher compressive strength (5.46 MPa) from TSS than from the CS sample (3.92 MPa), highlighting the synergetic effect of La2O3 doping and the TSS strategy.

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Multifunctional Electromagnetic Responsive Porous Materials Synthesized by Freeze Casting: Principles, Progress, and Prospects

Ning,

Zeng,

Huang

et al. 2024

Adv Funct Materials

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Freeze casting is a solidification technique utilized in the fabrication of porous materials. However, the freeze casting process is quite complex, and significant challenges remain in precisely controlling the pore size and shape of porous structures. This study aims to investigate the customization of multifunctional electromagnetic wave (EMW) absorbers with 3D porous structures via freeze casting. This review initially presents the fundamental principles underlying the freeze casting technique and examines the correlation between internal and external factors during the preparation process and porosity. The emerging trends in constructing novel and intricate macroscopic structures through freeze casting are subsequently outlined. Furthermore, this review focuses on the fabrication of composites with various porous microstructures through freeze casting of low‐dimensional building blocks, and their EMW response and multifunctional properties. By regulating the internal and external influencing mechanisms of freeze casting, porous EMW absorption materials exhibit outstanding advantages such as electromagnetic property manipulation, controllable structure, high porosity, high specific surface area, lightweight, and flexibility. These features broaden their applications in electromagnetic shielding, mechanical property, radar stealth, thermal insulation and fire prevention, flexible sensors, antifreeze ability, etc. In addition, we discuss the challenges and prospects of high‐performance EMW absorbers using freeze casting techniques.

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The influence of Fe2O3 doping on the pore structure and mechanical strength of TiO2-containing alumina obtained by freeze-casting

Cited by 21 publications

References 56 publications

Role of solvent composition and sintering time on the porosity of α‐alumina monoliths produced by freeze casting

Role of solvent composition and sintering time on the porosity of α‐alumina monoliths produced by freeze casting

Enhanced compressive strength of porous alumina realized by synergy between La‐doping and two‐step sintering

Multifunctional Electromagnetic Responsive Porous Materials Synthesized by Freeze Casting: Principles, Progress, and Prospects

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