Abstract
Porous, silicon carbonitride‐based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh‐molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross‐linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open‐pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10−14 m². The materials were further exposed to long‐term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science.
Highlights
P OROUS ceramics have a wide range of applications due to their exceptional properties, including their mechanical strength and their stability in corrosive and high-temperature environments
We report on the fabrication of planar, macroporous ceramic support structures by combining a polysilazane precursor with ultra-high molecular weight polyethylene (UHMW-PE) microbeads as sacrificial templates
After cross-linking, heat treatment was used for both UHMW-PE removal as well as for thermal conversion of the preceramic polymer into the Polymer-derived ceramics (PDCs)
Summary
P OROUS ceramics have a wide range of applications due to their exceptional properties, including their mechanical strength and their stability in corrosive and high-temperature environments. The application of the sacrificial porogen technique in combination with PDCs has been shown to be very versatile as a result of the tailorability of both open- and closed-cell structures, and the high reproducibility of the pore structures generated In this technique, the preceramic polymer is mixed with sacrificial templates which are extracted during a later step, either by burn-off, thermal decomposition, etching, or leaching. In contrast to the majority of previous works employing this combination of materials, the preceramic polymer is used in its initial, liquid state, allowing a more versatile shaping through a casting process with subsequent curing We reported on this processing approach recently, and showed its general feasibility for the preparation of porous, free-standing structures in the Si–C and Si–C–N systems.[42]. A core objective of this present work is an in-depth correlation between a number of processing parameters and the resulting materials’ performance in terms of permeability and strength, as well as the evaluation of its long-term stability in oxidizing, neutral, and reducing atmospheres at high temperatures, leading to the development of a material system well suited for potential membrane or catalysis applications
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