Low‐Density Open Cellular Silicon Carbide Foams from Sucrose and Silicon Powder

Abstract

Open cellular SiC foams with low densities were prepared by thermo‐foaming and setting (130°C–150°C) of silicon powder dispersions in molten sucrose followed by pyrolysis and reaction sintering at 1500°C. The bubbles generated in the dispersion by water vapor produced by the –OH condensation was stabilized by the adsorption of silicon particles on the air‐molten sucrose interface. The composition of a sucrose‐silicon powder mixture for producing SiC foam without considerable unreacted carbon was optimized. The sucrose in the thermo‐foamed silicon powder dispersion leaves 24 wt% carbon during the pyrolysis. The sintering additives such as alumina and yttria promoted the silicon‐carbon reaction. SiC nanowires with diameters in the range of 35–55 nm and length >10 μm observed on the cell walls as well as in the fractured strut region were grown by both vapor–liquid–solid and vapor–solid mechanisms. Large SiC foam bodies without crack could be prepared as the total shrinkage during pyrolysis and reaction sintering was only ~30 vol%. The relatively low compressive strength (0.06–0.41 MPa) and Young's modulus (14.9–24.2 MPa) observed was due to the large cell size (1.1–1.6 mm) and high porosity (93%–96%).

Bio-inspired modification of silicon carbide foams for oil/water separation and rapid power-free absorption towards highly viscous oils

“…3a. Benchmarked against the light weight existing foams with density values of ρ = 0.391 ~ 0.514 g/cm 3 , we found that our foams possess higher compression strengths when compared to the values reported in the literatures (Table 1) [30][31][32][33]. The composition of slurry is an important factor affecting the mechanical properties of silicon carbide foams.…”

Nanowire‐decorated SiC foam from tissue paper and silicon powder by filter‐pressing

“…The XRD spectrum of the sample heat‐treated at 1600°C shows no peak corresponding to silicon. On the other hand, all well‐defined peaks corresponding to β‐SiC are observed . This indicates the complete conversion of silicon present in the body to SiC.…”

“…The in situ growth of SiC nanowires on the cell wall surfaces is observed during the pyrolysis and subsequent high‐temperature heat treatment of preceramic polymer foams . The formation of SiC nanowires is also reported during the reaction between silicon and carbon in silicon‐carbon composite foam to form SiC foam . Alternatively, SiC nanowires are incorporated on the cell walls of SiC foams by a chemical infiltration method .…”

“…The SiC foams with a wide range of porosity and pore architecture are prepared either from SiC powder suspensions or preceramic polymers. Polymer foam replication, direct foaming, freeze‐casting and emulsion templating methods are used for the preparation of SiC foams from both SiC powder suspensions and preceramic polymers . In addition, SiC foams with unidirectional cellular pore structure are prepared by infiltrating pyrolyzed wood template with silicon in the molten or vapor phase .…”

“…In addition, SiC foams with unidirectional cellular pore structure are prepared by infiltrating pyrolyzed wood template with silicon in the molten or vapor phase . Recently, cellular SiC foams were produced by high‐temperature heat treatment of carbon‐silicon composite foams prepared by thermo‐foaming of silicon powder dispersions in molten sucrose followed by pyrolysis . Liang et al reported a preparation of SiC foam from dough by carbonization followed by carbothermal reduction.…”