Conductive Ceramic Foams from Preceramic Polymers

Colombo, Paolo; Gambaryan‐Roisman, Tatiana; Scheffler, Michael; Buhler, P.; Greil, Peter

doi:10.1111/j.1151-2916.2001.tb01000.x

Cited by 96 publications

(57 citation statements)

References 7 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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“…The electrical conductivity of polymer-derived porous ceramics depends on the type and amount of fillers and the type of precursor polymers used [85]. A combination of proper selection of the foaming and pyrolysis processes with appropriate fillers is believed to produce porous ceramic structures with a large degree of variation in functionality and properties [6,85,86]. It was also reported that a phenyl methyl poly (silsesquioxane) melt containing small amounts of ethoxy and hydroxyl groups can be foamed by an in situ blowing technique above 200…”

Section: Direct Foamingmentioning

confidence: 99%

“…For example, completely open-celled, interconnected (cell walls containing holes), and closed-cell foams can be obtained using flexible, semi-rigid and rigid PU precursors, respectively [74,75]. On the other hand, the residual carbon content (from PU) can be removed by direct foaming of the preceramic polymer with liquid blowing agent like pentane or Freon, thereby improving high-temperature properties of the foams [6,85]. Microcellular ceramics with a cell size of about 8 µm were fabricated using PMMA microbeads as sacrificial templates [82].…”

Section: Direct Foamingmentioning

confidence: 99%

“…Direct foaming method produces foams of high green strength and enables easy machining after drying. The electrical conductivity of polymer-derived porous ceramics depends on the type and amount of fillers and the type of precursor polymers used [85]. A combination of proper selection of the foaming and pyrolysis processes with appropriate fillers is believed to produce porous ceramic structures with a large degree of variation in functionality and properties [6,85,86].…”

Section: Direct Foamingmentioning

confidence: 99%

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Processing of polysiloxane-derived porous ceramics: a review

Kumar

Kim

2010

Science and Technology of Advanced Materials

112

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Because of the unique combination of their attractive properties, porous ceramics are considered as candidate materials for several engineering applications. The production of porous ceramics from polysiloxane precursors offers advantages in terms of simple processing methodology, low processing cost, and easy control over porosity and other properties of the resultant ceramics. Therefore, considerable research has been conducted to produce various Si(O)C-based ceramics from polysiloxane precursors by employing different processing strategies. The complete potential of these materials can only be achieved when properties are tailored for a specific application, whereas the control over these properties is highly dependent on the processing route. This review deals with processing strategies of polysiloxane-derived porous ceramics. The essential features of processing strategies-replica, sacrificial template, direct foaming and reaction techniques-are explained and the available literature reports are thoroughly reviewed with particular regard to the critical issues that affect pore characteristics. A short note on the cross-linking methods of polysiloxanes is also provided. The potential of each processing strategy on porosity and strength of the resultant SiC or SiOC ceramics is outlined.

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“…[3][4][5][6][7] Depending on the requirements of a given application, microcellular ceramics must exhibit specific cell sizes, cell size distributions, cell morphologies, and different mechanical properties. Obviously, the processing techniques used to develop microcellular ceramics must result in well-controlled microstructures and yield mechanical properties that render the material serviceable for a specific application.…”

Section: 2mentioning

confidence: 99%