Processing, microstructure and elastic properties of mullite-based ceramic foams prepared by direct foaming with wheat flour

Gregorová, Eva; Pabst, Willi; Uhlířová, Tereza; Nečina, Vojtěch; Veselý, Martin; Sedlářová, Ivona

doi:10.1016/j.jeurceramsoc.2015.09.028

Cited by 45 publications

(16 citation statements)

References 24 publications

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“…It was experimentally observed that with decreasing density, the Poisson’s ratio of aluminium foams decreases from the value of 0.34 down to 0.21. This result is similar to the porosity dependence of Poisson’s ratio observed previously in porous solids and ceramics [ 28 , 29 ].…”

Section: Resultssupporting

confidence: 91%

“…Most models created for porous solids which are based on Equation(5) lead to the conclusion that with increasing porosity, there is a tendency for the Poisson’s ratio of porous ceramic to approach the constant value [ 28 , 29 ] of 0.2, as this value seems to be an “attractor“ for the effective Poisson’s ratio. However, when the Poisson’s ratio of the solid phase ν 0 is below 0.2 ( ν 0 < 0.2), the effective Poisson’s ratio tends to increase with increasing porosity to this value.…”

Section: Resultsmentioning

confidence: 99%

“…In another approach, the Poisson’s ratio can be in the simplest way modelled by a linear approximation [ 29 ]:

where ν is the effective Poisson’s ratio, ν 0 is the Poisson’s ratio of the corresponding bulk material, and φ is the porosity. However, this approach has the typical shortcomings of mixture-based theories.…”

Section: Resultsmentioning

confidence: 99%

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Poisson’s Ratio of Closed-Cell Aluminium Foams

2018

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A nondestructive impulse excitation technique was used to investigate Poisson’s ratio of powder metallurgical pure closed-cell aluminium foams according to ASTM E 1876 within the foam density range of 0.430–1.390 g·cm−3. Instead of a constant value of 0.34, as according to Gibson and Ashby’s assumption for the Poisson’s ratio of metallic foams, the decrease of the Poisson’s ratio with decreasing foam density was observed. Observed Poisson’s ratio data were in the range of 0.21–0.34. To check the validity of the results, the Young’s modulus was calculated using Poisson’s ratio and its dependence on relative density was successfully modelled using the usual power law function with characteristic exponent of 1.72 ± 0.1. This confirms that the obtained experimental results for Poisson’s ratio are valid. Finally, rule of mixture and percolation theory were used to model the observed decrease of Poisson’s ratio with increasing porosity.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

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Poisson’s Ratio of Closed-Cell Aluminium Foams

2018

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“…Ceramic foams have been prepared using several methods such as direct foaming [2][3][4][5][6][7], sacrificial template or fugitives [8][9][10][11][12], replica methods [1,[13][14][15][16] and partial sintering [17,18]. Ceramic foam derived using the abovementioned methods is chemo-thermo-mechanically suitable for further processing.…”

Section: Introductionmentioning

confidence: 99%

Titania-Coated Alumina Foam Photocatalyst for Memantine Degradation Derived by Replica Method and Sol-Gel Reaction

et al. 2020

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In the present work, alumina (Al2O3) foam was prepared by the replica method where a polyurethane (PU) foam (30 pores per inch (ppi)) template was impregnated with a 60 wt.% Al2O3 suspension. Sintered Al2O3 foam was used as substrate for the deposition of sol-gel derived titania (TiO2) film using dip coating. For the preparation of TiO2 sol, titanium(IV) isopropoxide (Ti-iPrOH) was used as the precursor. The common problem of qualification and quantification of a crystalline coating on a highly porous 3D substrate with an uneven surface was addressed using a combination of different structural characterization methods. Using Powder X-ray Diffraction (PXRD) and synchrotron Grazing Incidence X-ray Diffraction (GIXRD) on bulk and powdered Al2O3 foam and TiO2-coated Al2O3 foam samples, it was determined Al2O3 foam crystallizes to corundum and coating to anatase, which was also confirmed by Fourier Transformed Infrared Spectroscopy (FTIR). Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) revealed the structural and microstructural properties of the substrate and coating. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) were used to clarify the evolution of the porous microstructure. The Al2O3-TiO2 composite was evaluated as a photocatalyst candidate for the degradation of the micropollutant medication memantine. The degradation rate was monitored using a light-emitting diode (LED) lamp operating at electromagnetic (EM) wavelength of 365 nm. The photocatalytic activity of sol-gel-derived TiO2 film immobilized on the Al2O3 foam was compared with commercially available TiO2 nanoparticles, P25-Degussa, in the form of a suspension. The levels of memantine were monitored by High-Performance Liquid Chromatography–Tandem Mass Spectrometry (HPLC–MS/MS). The efficiency and rate of the memantine photodegradation by suspended TiO2 nanoparticles is higher than the TiO2-coated Al2O3 foam. But, from the practical point of view, TiO2-coated Al2O3 foam is more appropriate as a valuable photocatalytic composite material.

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“…Porous mullite materials (PMMs) have attracted significant research attention owing to their low thermal expansion coefficient and TC, high‐temperature creep resistance, high thermal shock resistance, excellent high temperature mechanical properties, and large specific surface area. The preparation methods of PMMs have been continuously developed using different types of pore‐forming agents and molding methods, 10‐13 including direct foaming, 14‐15 vacuum molding, 16 gel freezing, 17‐19 starch coagulation, 20‐21 epoxy gelation, 22 and the use of foam gel 23‐25 …”

Section: Introductionmentioning

confidence: 99%

Microscopic regulation of plant morphological pores on mechanical properties of porous mullite materials

et al. 2020

Int J Applied Ceramic Tech

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Generally, a multilayer structure is present inside a walnut shell, and the residual structure of the walnut shell is retained after impregnation and firing. When the walnut shell is used as a pore‐forming agent, this structure helps in improving the mechanical and thermal insulation properties of the lightweight porous materials. In this study, porous mullite materials (PMMs) with plant morphological structure pores were prepared using a‐Al2O3 and silica powder as the raw materials with addition of sol‐impregnated walnut shell powder (WSP). The influence of sol type and firing temperature on the pore structure of the PMMs was analyzed, which affected the compressive strength and thermal conductivity. The plant morphological porous structure was observed in the samples after sol impregnation. After firing at different temperatures, the porous structure gradually contracted and supported the pores, improving the mechanical properties, while the complex porous structure increased the heat conduction path, thereby improving the insulation performance. Using WSP impregnated with silica‐sol and zirconia‐sol as pore‐forming agents, PMMs with higher compressive strength and relatively low thermal conductivity (TC) were prepared.

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Processing, microstructure and elastic properties of mullite-based ceramic foams prepared by direct foaming with wheat flour

Cited by 45 publications

References 24 publications

Poisson’s Ratio of Closed-Cell Aluminium Foams

Poisson’s Ratio of Closed-Cell Aluminium Foams

Titania-Coated Alumina Foam Photocatalyst for Memantine Degradation Derived by Replica Method and Sol-Gel Reaction

Microscopic regulation of plant morphological pores on mechanical properties of porous mullite materials

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