Monolithic silicon carbide with interconnected and hierarchical pores fabricated by reaction‐induced phase separation

Abstract

Hierarchically porous silicon carbide (SiC) monoliths were fabricated based on polycarbosilane (PCS), divinyl benzene (DVB), and decalin, by a sequence of procedures including catalyst-free hydrosilylation reaction-induced phase separation, ambient-pressure drying, calcination, and HF etching. The influences of ratios of each component on the phase separation were systematically studied. It was found that isotactic polypropylene added as a nonreactive additive could effectively tailor the microstructure and improve the mechanical properties of SiC monoliths. The resultant SiC monoliths mainly consisted of β-SiC nanocrystals, and possessed low bulk density (0.7 g/cm 3 ), high porosity (78%), large specific area (100.6 m 2 /g), high compressive strength (13.5 ± 1.6 MPa), and hierarchical pores (macropores around 350 nm, mesopores around 4 and 20 nm). These properties make SiC monoliths promising materials for catalyst/catalyst support, gas separator, and the reinforcement of high-temperature composites. K E Y W O R D Sambient pressure drying, and nanocrystal, hierarchical pore, reaction-induced phase separation, SiC monolith

Fabricating porous ceramic materials via phase separations in blends of cellulose acetate and ceramic nanoparticles

“…Moreover, when the ratio deviates from the value of 1:1.5, either sticky (the ratio >1:1.5) or crispy (the ratio <1:1.5) samples are exhibited after setting in 24 h, which indicates that the ratio has evident influences on the phase separation process. According to observations in our previous work 11 and this study, incomplete phase separation results in sticky appearance, whereas the nucleation-growth mechanism is responsible for the crispy phenomenon. Therefore, in the following discussions, the ratio of DMF to n-hexanol will be fixed at 1:1.5.…”

“…In our previous work, porous SiC materials were prepared by a reaction‐induced phase separation method 11 . Here, the mechanism behind the preparation is different, and it is thermally impacted and non‐solvent‐induced phase separation.…”

“…In our previous work, porous SiC materials were prepared by a reaction-induced phase separation method. 11 Here, the mechanism behind the preparation is different, and it is thermally impacted and non-solvent-induced phase separation. Yet, both of them can be explained via the perspective of Gibbs free energy of mixing (ΔG m ), which is expressed as follows 29 :…”

“…Porous ceramic materials have wide applications in catalysts, filters, absorbers, thermal insulating materials, electrodes, and others, attributed to their unique advantages in the perspectives of catalytic activity, thermal and chemical stability, and thermal conductivity. 1,2 To date, several approaches have been developed for the fabrication of porous ceramic materials, including powder sintering, 3 direct foaming, 4 templating, [5][6][7][8] phase separation, [9][10][11] freeze-drying, 12 and supercritical drying. 13,14 Within these approaches, the phase separa-Hongli Hu and Hangyu Zhong equally contributed to this work.…”

Electrically conductive and thermally stable SiC‐TiC containing nanocomposites via flash pyrolysis

“…Recently, a polymer derived ceramic (PDC) route has demonstrated highly desirable capabilities to refine the compositions and microstructures in SiOC, SiCN, and SiC 18‐20 by tunable starting precursors and pyrolysis conditions. For instance, Ti‐containing SiOC composites exhibit high electrical conductivity and improved thermal stability 21,22 .…”