Polysilsesquioxane derived ceramic foams with gradient porosity

Zeschky, Jürgen; Höfner, Thomas; Arnold, Claudia; Weißmann, R.; Hourlier, D.; Scheffler, Michael; Greil, Peter

doi:10.1016/j.actamat.2004.10.039

Cited by 150 publications

(110 citation statements)

References 47 publications

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“…[1] A variety of methods have been developed for the fabrication of cellular ceramics, for example, direct foaming techniques based on particle stabilized emulsions, [2][3][4] or preceramic polymer melts. [5][6][7] Nevertheless, ceramic foams for the above mentioned applications are manufactured on an industrial scale by the polymer sponge replication process established by Schwartzwalder and Somers in 1961. [8] This results in a macrocellular foam-like structure similar to that of the polymeric sponge used as template in the process.…”

Section: Introductionmentioning

confidence: 99%

Impact of Slurry Composition on Properties of Cellular Alumina: A Computed Tomographic Study

et al. 2017

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Fine-pored, 45 ppi (pores per linear inch) alumina foams are prepared from ceramic slurries with varying contents of additives (deflocculant, binder) and solid loading following a standardized procedure. Rheological key parameters (yield stress, high-shear viscosity) of the respective slurries are determined by approximation of the experimental flow curves with appropriate rheological models. The resulting ceramic foams are characterized by computed tomography (CT) followed by a morphometric analysis of the reconstruction volume data. The main scope of the work involves the development of a procedure to reliably define the binarization threshold during these morphometric calculations, which is based on the analysis of the differential course of the total porosity results from calculations performed at varying binarization threshold values ("differential thresholding"). A very good match of the CT porosity results with experimental data is achieved, despite the unfavorable CT voxel resolution to foam structure fineness relation. The CT evaluation results are finally correlated to the rheological properties of the respective slurries used in foam manufacturing. The dominant slurry composition parameters are the weight fraction of the ceramic powder and the binder concentration. Increasing binder and solid content result in an increased yield stress and viscosity of the respective dispersion and consequently in a decreased porosity and cell size of the finally manufactured cellular ceramic.

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Section: Introductionmentioning

confidence: 99%

Impact of Slurry Composition on Properties of Cellular Alumina: A Computed Tomographic Study

et al. 2017

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“…3 X-ray diffractograms of the as-thermolysed and heat-treated SiOC samples. self-blowing of poly(phenylmethylsilsesquioxane) at 300 ℃ due to release of water and ethanol was reported in the literatures by Gambaryan-Roisman et al [25] and Zeschky et al [26][27][28]. This method of producing SiOC foams is promising, since the removal of sacrificial phase during pyrolysis is not required.…”

Section: Ceramic Foamsmentioning

confidence: 84%

Processing and characterization of polymer precursor derived silicon oxycarbide ceramic foams and compacts

2013

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This work focused on the fabrication of silicon oxycarbide ceramic (SiOC) foams as well as dense compacts using poly(hydridomethylsiloxane) (PHMS) as a polymer precursor. The room-temperature cross-linking of PHMS was achieved by the addition of 1,4-diazabicyclo [2.2.2] octane (DABCO) with the release of hydrogen gas as a by-product. This resulted in self-blowing of the polymer precursor at room temperature and thereby offered the possibility of producing SiOC foams without the need of any external blowing agents. We also reported the fabrication of crack-free silicon oxycarbide compacts by cold compaction and pyrolysis route using polyvinyl alcohol (PVA) as a processing additive. Cylindrical-shaped pellets were pyrolysed at 1300 ℃ in argon atmosphere with a ceramic yield of approximately 85%. Increased resistance to phase separation and crystallization up to 1400 ℃ was attributed to the presence of large volume fraction of free carbon in the material which was confirmed by Raman spectroscopy.

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“…Th e burn-out is intended to leave behind additional porosity in the struts. [12,13]. Th e polymer is solid at room temperature, has a melting interval at around 60 °C and exhibits a density of ~1 g/cm 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Novel developments are dedicated to the manufacturing of high-transparent glass foams for optical applications such as biological cell support or support for photocatalysts [6,7]. Th e most relevant processing routes for the fabrication of porous ceramics are (i) replica techniques [8][9][10], (ii) direct-foaming techniques [11][12][13][14][15][16] and (iii) sacrifi cial template methods [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Polymer derived ceramic foams with additional strut porosity

Reschke¹,

Laskowsky²,

Kappa³

et al. 2011

Epitoanyag-JSBCM

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Ceramic foams with additional strut porosity were prepared by a self-foaming process of a polysilsesquioxane. The strut porosity was generated by adding sacrificial pore formers comprising of polymethylmethacrylate or of polyethylene to the self-foaming silicone. The polymer-inherent shrinkage was reduced by adding SiC particulate fillers to the silicone/pore-former mixture. Foaming was carried out on a preheated furnace at 270 °C, and subsequent pyrolysis was performed in argon atmosphere in the temperature range from 800 °C to 1200 °C in order to trigger the polymer-to-ceramic transformation of the polysilsesquioxane. The materials were characterized with respect to the pore size and the total porosity, the microstructure and the mechanical strength. The volumetric mean pore diameter of the strut ranged from 25 μm to 100 μm and the porosity was found to be 40% to 94%. The maximum compression strength exceeded 16 MPa.

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Polysilsesquioxane derived ceramic foams with gradient porosity

Cited by 150 publications

References 47 publications

Impact of Slurry Composition on Properties of Cellular Alumina: A Computed Tomographic Study

Impact of Slurry Composition on Properties of Cellular Alumina: A Computed Tomographic Study

Processing and characterization of polymer precursor derived silicon oxycarbide ceramic foams and compacts

Polymer derived ceramic foams with additional strut porosity

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