Asymmetric polysilazane-derived ceramic structures with multiscalar porosity for membrane applications

Konegger, Thomas; Tsai, Chen Chih; Peterlik, Herwig; Creager, Stephen E.; Bordia, Rajendra K.

doi:10.1016/j.micromeso.2016.06.027

Cited by 23 publications

(18 citation statements)

References 50 publications

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“…A very convenient precursor route to produce nonoxide ceramics is the polymer‐derived‐ceramic (PDC) route . This method is based on the design of a suitable and high‐purity synthetic precursor that provides a uniform chemical composition at the molecular scale.…”

Section: Introductionmentioning

confidence: 99%

Molecular Chemistry and Engineering of Boron‐Modified Polyorganosilazanes as New Processable and Functional SiBCN Precursors

Viard

Fonblanc

Schmidt

et al. 2017

Chemistry A European J

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A series of boron-modified polyorganosilazanes was synthesized from a poly(vinylmethyl-co-methyl)silazane and controlled amounts of borane dimethyl sulfide. The role of the chemistry behind their synthesis has been studied in detail by using solid-state NMR spectroscopy, FTIR spectroscopy, and elemental analysis. The intimate relationship between the chemistry and the processability of these polymers is discussed. Polymers with low boron contents displayed appropriate requirements for facile processing in solution, such as impregnation of host carbon materials, which resulted in the design of mesoporous monoliths with a high specific surface area after pyrolysis. Polymers with high boron content are more appropriate for solid-state processing to design mechanically robust monolith-type macroporous and dense structures after pyrolysis. Boron acts as a crosslinking element, which offers the possibility to extend the processability of polyorganosilazanes and suppress the distillation of oligomeric fragments in the low-temperature region of their thermal decomposition (i.e., pyrolysis) at 1000 °C under nitrogen. Polymers with controlled and high ceramic yields were generated. We provide a comprehensive mechanistic study of the two-step thermal decomposition based on a combination of thermogravimetric experiments coupled with elemental analysis, solid-state NMR spectroscopy, and FTIR spectroscopy. Selected characterization tools allowed the investigation of specific properties of the monolith-type SiBCN materials.

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Section: Introductionmentioning

confidence: 99%

Molecular Chemistry and Engineering of Boron‐Modified Polyorganosilazanes as New Processable and Functional SiBCN Precursors

Viard

Fonblanc

Schmidt

et al. 2017

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…A convenient precursor‐based approach is the polymer‐derived ceramics (PDCs) route . This method is based on the synthesis of a polymer that provides a uniform chemical composition to the material at the molecular scale.…”

Section: Introductionmentioning

confidence: 99%

Molecular‐Level Processing of Si‐(B)‐C Materials with Tailored Nano/Microstructures

Schmidt

Durif

Acosta

et al. 2017

Chemistry A European J

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The design of Si-(B)-C materials is investigated, with detailed insight into the precursor chemistry and processing, the precursor-to-ceramic transformation, and the ceramic microstructural evolution at high temperatures. In the early stage of the process, the reaction between allylhydridopolycarbosilane (AHPCS) and borane dimethyl sulfide is achieved. This is investigated in detail through solid-state NMR and FTIR spectroscopy and elemental analyses for Si/B ratios ranging from 200 to 30. Boron-based bridges linking AHPCS monomeric fragments act as crosslinking units, extending the processability range of AHPCS and suppressing the distillation of oligomeric fragments during the low-temperature pyrolysis regime. Polymers with low boron contents display appropriate requirements for facile processing in solution, leading to the design of monoliths with hierarchical porosity, significant pore volume, and high specific surface area after pyrolysis. Polymers with high boron contents are more appropriate for the preparation of dense ceramics through direct solid shaping and pyrolysis. We provide a comprehensive study of the thermal decomposition mechanisms, and a subsequent detailed study of the high-temperature behavior of the ceramics produced at 1000 °C. The nanostructure and microstructure of the final SiC-based ceramics are intimately linked to the boron content of the polymers. B C/C/SiC nanocomposites can be obtained from the polymer with the highest boron content.

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“…In membranes with micropores (<2 nm), such as amorphous silica, smaller gas molecules move more easily through the pores. The challenge with such membranes is to prevent the collapse of the micropores at high temperatures (>450 °C); polysilazane-derived silicon carbonitrides have been reported to satisfy this requirement [9,10], and a further improvement in thermal stability of microporous structures by the addition of Ni has also been reported [11]. In these membranes, the selectivity of hydrogen gas is sufficiently high; however, a high flux of hydrogen gas is achieved only under a high pressure of a supplied gas.…”

Section: Introductionmentioning

confidence: 99%

Separation of Hydrogen from Carbon Dioxide through Porous Ceramics

et al. 2016

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The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ), and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above a critical pressure gradient, which was smaller for H2 gas than for CO2 gas. When the Knudsen number (λ/r ratio, λ: molecular mean free path, r: pore radius) of a single gas was larger than unity, Knudsen flow became the dominant gas transportation process. The H2 fraction for the mixed gas of (20%–80%) H2–(80%–20%) CO2 through porous Al2O3, YSZ, and SiC approached unity with decreasing pressure gradient. The high fraction of H2 gas was closely related to the difference in the critical pressure gradient values of H2 and CO2 single gas, the inlet mixed gas composition, and the gas flow mechanism of the mixed gas. Moisture in the atmosphere adsorbed easily on the porous ceramics and affected the critical pressure gradient, leading to the increased selectivity of H2 gas.

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Asymmetric polysilazane-derived ceramic structures with multiscalar porosity for membrane applications

Cited by 23 publications

References 50 publications

Molecular Chemistry and Engineering of Boron‐Modified Polyorganosilazanes as New Processable and Functional SiBCN Precursors

Molecular Chemistry and Engineering of Boron‐Modified Polyorganosilazanes as New Processable and Functional SiBCN Precursors

Molecular‐Level Processing of Si‐(B)‐C Materials with Tailored Nano/Microstructures

Separation of Hydrogen from Carbon Dioxide through Porous Ceramics

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