Porous Silicon Carbide Sintered Substrates for High-Temperature Membranes

Abstract

Silicon carbide (SiC) porous substrates are prepared by pressureless sintering of SiC powders under an inert atmosphere of argon. The porous SiC substrates were characterized by measuring their porosity, pore size distribution, surface characteristics, and structure. Their transport characteristics were investigated using N 2 and He as the test gases. Three different starting powders and four different sintering aids, Al 2 O 3 , B 4 C, carbon black, and phenolic resin, either by themselves or in combination, were investigated in terms of their ability to prepare good quality substrates. It was found that the porosity, pore size distribution, and transport characteristics of the resulting SiC-sintered bodies depend on the nature of the original powder, the particle size in the green SiC samples, and the type and molar ratio of the sintering aid utilized. Depending on the preparation technique, both mesoporous and macroporous materials could be prepared. These supports are currently utilized for the preparation of microporous membranes.

Sic-Based Hydrogen Selective Membranes for Water-Gas-Shift Reaction

“…These substrates are prepared as follows. [11] A silicon carbide fine powder (Sumitomo Osaka Cements, Japan) with an average particle size of 0.03µ is mixed with a more course silicon carbide powder (Superior Graphite Co.,) with an average particle size of 0.6µ in the ratio of 1:2. Boron carbide (in the amount of 0.1 wt %) and phenolic resin (in the amount 4 wt %) are used as the sintering aids.…”

“…Boron carbide (in the amount of 0.1 wt %) and phenolic resin (in the amount 4 wt %) are used as the sintering aids. The mixture of powders and various sintering aids are pressed into disks, which are then calcined at 1950 o C to obtain the macroporous SiC membrane substrates (more details about the preparation of such substrates can be found in our prior publication) [11]. These SiC substrates are then used for further surface modification via the sol-gel technique.…”

“…Phenolic resin is utilized as the carbon source. The SiC sol precursors are then coated on the SiC substrates, which are prepared by our group [30] using dry-pressing techniques, and sintering at 1950 o C. The SiC sol precursors undergo carbothermal reduction at high temperatures to produce the final SiC thin films. The sol-gel step is an important intermediate stage in the preparation of asymmetric microporous SiC membranes (the final stage can be a CVD/CVI or a polymeric precursor pyrolysis step), which are capable of withstanding high service temperatures and are thermally stable to the presence of steam.…”

“…The absolute values of permeance and the separation factor are both important in terms of determining the usefulness of the membrane for further applications and processing. The permeance of each species is measured using a laboratory permeation apparatus, which has been described elsewhere [11]. Briefly the membrane disk is placed in between the two halfcells of the apparatus, one chamber is pressurized at the required pressure, while the other is maintained at atmospheric pressures.…”

Funky inorganic fibers

“…The fabrication of silicon carbide hollow fibers is useful for extreme environments such as high temperature gas separation or liquid permeation where there is an increased risk of fouling [100,101]. Metallic fibers are produced sporadically and are limited to stainless steel/iron [66][67][68], nickel [6,70] and titanium [72].…”