Water‐based freeze casting: Adjusting hydrophobic polymethylsiloxane for obtaining hierarchically ordered porous SiOC

Zhang, Huixing; Fidelis, Clara Lana; Serva, Ana Luiza Teixeira; Wilhelm, Michaela; Rezwan, Kurosch

doi:10.1111/jace.14782

Cited by 21 publications

(16 citation statements)

References 47 publications

(97 reference statements)

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“…This suggests the presence of graphene at the surface . Overall, this leads to the conclusion that during pyrolysis, the carbon‐rich C x SiO y oxidizes further, even forming energetically favorable silica, while the carbon partially segregates to the surface to form grapheme …”

Section: Resultsmentioning

confidence: 97%

“…The vapor adsorption was recalculated based on the SSA values and given in mmol/m 2 . The surface characteristic was reflected by the ratio of water/ heptane adsorption, instead of the absolute value of the water or vapor adsorption . All the samples (except samples pyrolyzed at 1000°C) have a higher n‐heptane adsorption than water vapor adsorption, displaying hydrophobic surface characteristics.…”

Section: Resultsmentioning

confidence: 99%

“…22 Overall, this leads to the conclusion that during pyrolysis, the carbon-rich C x SiO y oxidizes further, even forming energetically favorable silica, while the carbon partially segregates to the surface to form grapheme. 23 The XPS results clearly shows the presence of an oxygencontaining (SiOxCy) surface layer on the SiC(O) surface might affect the surface properties of the formed silicon carbide. Therefore, hydrophilicity and hydrophobicity of the pyrolyzed samples are determined using water and n-heptane vapor adsorption at 22°C ( Figure 6).…”

Section: Nomentioning

confidence: 98%

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High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

et al. 2019

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In the present work, a high surface area SiC(O)‐based ceramic powder was synthesized upon thermal transformation of a polymer‐derived macromolecular precursor, which was obtained by the chemical modification of a allylhyldrido polycarbosilane with poly(ethylene glycol) methaacrylate under argon environment. The pyrolysis of developed precursor led to the formation of amorphous and high surface area SiC(O)‐based ceramic powder with in situ generated micro/meso‐porosity. The specific surface area of the obtained powders depends on the processing temperature. It decreases from 363 to 122 m2/g as the pyrolysis temperature increases from 600 to 1200°C, respectively. Furthermore the promising samples were fabricated using pressing technique, which led to crack‐free SiC(O) monoliths on subsquent heat treatment. The present study also emphasizes the potential of produced SiC(O) ceramic powder to support NiO catalyst. The impregnation method were used to produce high surface area NiO@SiC(O) ceramic powder (NiO as a catalyst; SiC(O) as a catalyst support) for further catalytic applications. Interestingly, the distribution of the NiO was shown to strongly depend on the oxygen content present in the SiC(O) matrix. Thus, larger oxygen contents induce homogeneously distributed flower‐like NiO catalyst onto SiC(O).

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Nomentioning

confidence: 98%

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High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

et al. 2019

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“…It is known that the metal‐free preceramic polymer MK pyrolyzed at 600°C itself is hydrophobic . Since, the amine groups of the CLA are almost completely decomposed at 600°C Si‐containing CLAs mainly add additional hydrophilic SiO units to the pyrolyzed structure . The samples NiA2APD/600 and NiA2AP/600 exhibit one Si atom per complexing amine group.…”

Section: Resultsmentioning

confidence: 99%

“…25 Since, the amine groups of the CLA are almost completely decomposed at 600°C Si-containing CLAs mainly add additional hydrophilic SiO units to the pyrolyzed structure. 26,27 The samples NiA2APD/600 and NiA2AP/600 exhibit one Si atom per complexing amine group. In contrast, NiA2AE/600 includes only 0.5 Si atoms per amine group and NiA2TEMDA/600 has no Si atoms at all.…”

Section: Ssa and Surface Characteristicmentioning

confidence: 99%

Porous SiOC monoliths with catalytic activity by in situ formation of Ni nanoparticles in solution‐based freeze casting

2020

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Micro‐ and macroporous monoliths with in situ formed nickel nanoparticles were prepared for the first time by the combination of solution‐based freeze casting and preceramic polymers (methyl polysiloxane). This one‐step process results in macroporous monoliths composed of microporous and catalytic active nickel‐containing polymer‐derived ceramic. Four different complexing and cross‐linking siloxanes with amino functionality were screened for their ability to create small nickel particles. TEM analysis confirmed 3‐aminopropyltriethoxysilane being most efficient. High BET‐specific surface areas of 344‐461 m2 g−1 were achieved. Increased ratio of complexing groups to nickel improves the dispersion of nickel to (3.61 ± 1.49) nm. The nickel size dependence of conversion (maximum 0.49) and CH4 selectivity (maximum 0.74) in CO2 methanation emphasizes the importance of controlling the nickel size. The hydrophobic surface characteristic is hypothesized to be the main reason polymer‐derived catalysts having better catalytic activity compared with nickel‐impregnated silica. The promising catalytic activity combined with the versatile freeze casting process can prospectively address heat‐ and mass‐transfer considerations in heterogeneous monolith catalysis.

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Roll‐Pressed Silicon Anodes with High Reversible Volumetric Capacity Achieved by Interfacial Stabilization and Mechanical Strengthening of a Silicon/Graphene Hybrid Assembly

Kim

Choi

Chung

et al. 2023

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Application of Si anodes is hindered by severe capacity fading due to pulverization of Si particles during the large volume changes of Si during charge/discharge and repeated formation of the solid‐electrolyte interphase. To address these issues, considerable efforts have been devoted to the development of Si composites with conductive carbons (Si/C composites). However, Si/C composites with high C content inevitably show low volumetric capacity because of low electrode density. For practical applications, the volumetric capacity of a Si/C composite electrode is more important than gravimetric capacity, but volumetric capacity in pressed electrodes is rarely reported. Herein, a novel synthesis strategy is demonstrate for a compact Si nanoparticle/graphene microspherical assembly with interfacial stability and mechanical strength achieved by consecutively formed chemical bonds using 3‐aminopropyltriethoxysilane and sucrose. The unpressed electrode (density: 0.71 g cm−3) shows a reversible specific capacity of 1470 mAh g−1 with a high initial coulombic efficiency of 83.7% at a current density of 1 C‐rate. The corresponding pressed electrode (density: 1.32 g cm−3) exhibits high reversible volumetric capacity of 1405 mAh cm−3 and gravimetric capacity of 1520 mAh g−1 with a high initial coulombic efficiency of 80.4% and excellent cycling stability of 83% over 100 cycles at 1 C‐rate.

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Water‐based freeze casting: Adjusting hydrophobic polymethylsiloxane for obtaining hierarchically ordered porous SiOC

Cited by 21 publications

References 47 publications

High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

Porous SiOC monoliths with catalytic activity by in situ formation of Ni nanoparticles in solution‐based freeze casting

Roll‐Pressed Silicon Anodes with High Reversible Volumetric Capacity Achieved by Interfacial Stabilization and Mechanical Strengthening of a Silicon/Graphene Hybrid Assembly

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