Growth of One‐Dimensional Nanostructures in Porous Polymer‐Derived Ceramics by Catalyst‐Assisted Pyrolysis. Part II: Cobalt Catalyst

Abstract

Via catalyst-assisted pyrolysis, Si3N4 and SiC nanowires were produced on the cell walls of polymer-derived ceramic foams. The pyrolysis atmosphere and temperature were the main parameters affecting their development: silicon nitride singlecrystal nanowires formed under nitrogen, while silicon carbide ones were produced under argon, and their amount increased with the increasing pyrolysis temperature. Brunauer–Emmett– Teller analysis showed that the presence of the nanowires afforded high specific surface area (SSA) values to the macroporous ceramic foams, ranging from 10 to 110 m2/g. Co-containing samples developed higher SSA values, especially after pyrolysis at 14001C in N2, than samples containing Fe as a catalyst. The differences were explained in terms of morphology (diameter and assemblage), which depended on the processing conditions and the catalyst type (Co or Fe)

A Novel Oxidation Resistant SiC/B4C/C Nanocomposite Derived from a Carborane‐Containing Conjugated Polycarbosilane

“…(1) for CB-PSEPE-1450 is 12.5 nm, which is much larger than that for PSEPE-1450 (4.5 nm). 16 The second-order Raman spectra show weaker G′ (~2700 cm À1 ) and D″ (~2950 cm À1 ) band, which may be associated with the overtone of the D band and the D + G combination mode, respectively. Meanwhile, the L c of the nanocrystalline graphite for CB-PSEPE-1450 is 3.09 nm, slightly higher as compared with that for PSEPE-1450 (2.80 nm).…”

“…14 The position of G band at around 1600 cm À1 suggests the presence of nanocrystalline graphite, rather than complete amorphous carbon. 16 The second-order Raman spectra show weaker G′ (~2700 cm À1 ) and D″ (~2950 cm À1 ) band, which may be associated with the overtone of the D band and the D + G combination mode, respectively. The profiles of these bands support the presence of nanocrystalline graphite.…”

SiC Foams Decorated with SnO2 Nanostructures for Room Temperature Gas Sensing

“…Another promising way is the use of preceramic polymers due to the great tailorability of their structures on a molecular scale and ease of processing . While the presence of 1‐D nanostructures does not add a “real” porosity to a dense material, it has been demonstrated that their presence may increase the specific surface area (SSA) and/or functionalize previously “inert” surface of the component . Therefore, it can be possible to alter the final properties such as catalytic, sorption, magnetic or electrical of the formed material .…”

Decoration of Ceramic Foams by Ceramic Nanowires via Catalyst‐Assisted Pyrolysis of Preceramic Polymers

“…By using a ceramic foam (or a honeycomb) decorated with nanowires (NWs), it should be possible to improve the performance of a filter with respect to the trapping of nano‐sized particulate. Such a hierarchically porous ceramic component contains the 3D interconnected macroporosity of the host substrate and the micro‐ and mesoporosity deriving from the NWs directly formed on wall surfaces of cells . In a filter application, when a gas stream containing dust is continuously passed through the macropores decorated with NWs, the particulate can be collected by the bundled NWs, which posses a high specific surface area.…”

“…The use of preceramic polymer can lead to the simple and cost‐effective development of 1D nanostructures via catalyst‐assisted pyrolysis (CAP), as it does not involve expensive raw materials or equipment to be carried out . The length and diameter of obtained NWs on the wall of macroporous ceramic were reported to be 5–20 nm in diameter and ~2–3 μm in length, for porous SiC prepared by β‐SiC powder and polycarbosilane (PCS), 60 nm in diameter and several tens of micrometers in length for porous SiC by freeze casting of SiC/camphene slurries, and 129 nm in diameter and <300 μm in the length for silicon oxycarbide foam by physical blowing and catalyst‐assisted pyrolysis (CAP) of a polysilsesquioxane . However, to the best of our knowledge, there have been no studies investigating the coating of preceramic polymer on a commercially available macroporous ceramic and the formation of 1D nanostructures by its CAP.…”