Microstructure and gas permeation performance of porous silicon nitride ceramics with unidirectionally aligned channels

Abstract

Porous Si3N4 ceramics with unidirectionally aligned channels were prepared via freezing ceramics suspension with distinct solid contents under different freezing temperatures. The samples obtained using lower solid content in ceramic suspension at higher freezing temperature exhibit larger Darcian and non‐Darcian constants due to their higher open porosity, larger pore size and lower tortuosity. Moreover the investigation on individual contributions of viscous energy losses and inertial energy losses on the total pressure drop during permeation process indicates that with decreasing the solid content or the freezing temperature the viscous energy losses increase but the inertial energy losses decrease for samples owing to the differences in their pore structures. It is worth mentioning that porous Si3N4 ceramics with unidirectionally aligned channels exhibit larger Darcian and non‐Darcian constants than those with similar pore size distributions and open porosity owing to their lower tortuosity, thus rendering them appropriate for filters and membrane supports.

Research progress and applications of silica-based aerogels – a bibliometric analysis

“…Additionally, additives can change the morphology by regulating the growth of ice crystals. [111][112][113][114][115] For example, Xian et al 114 prepared aerogels with 30 mm pore size, adding 20 wt% glycerol, while the pore size of aerogels without glycerol was 20-50 mm. It is worth noting that different solvents have been used to produce different types of pore morphologies during the freeze casting of scaffolds and porous ceramics.…”

Increased microwave absorption property of porous Si3N4 ceramics by loading polymer-derived SiCN for a multifunctional design

“…Porous silicon nitride (Si 3 N 4 ) ceramic, a new structurefunction integrated ceramic material developed from Si 3 N 4 ceramic and a porous ceramic, possesses low density, high mechanical strength, and excellent thermal-chemical corrosion resistance, which can be advantageous in extreme environments, such as high temperatures, high speed, and strong corrosive conditions. [8][9][10] Furthermore, owing to the excellent thermal shock resistance, low dielectric constant, and low dielectric loss, as well as good electromagnetic wave (EMW) transmission performance, porous Si 3 N 4 ceramic is a candidate material for the construction of radomes or antenna windows. 10,11 However, with the increasing complexity of the electromagnetic confrontation environment, constructing a radome with wave-transparent in-band and stealth out-offband characteristics is rather urgent; therefore, adding EMW absorption ability in the porous Si 3 N 4 ceramic is very meaningful.…”

The capillary and thermal performance of the porous silicon nitride ceramics with nearly spherical pore structure

“…In addition, we have studied the relationships between pore structures of porous Si 3 N 4 ceramics and their permeation performance in previous works. [12][13][14] The capillary performance is associated with the driving force that propels liquid through small gaps in a porous medium in the absence of external forces. 15 The driving force is derived from the cohesive forces between the fluid's molecules and adhesive forces between the fluid's molecules and the molecules of the fluid's container.…”

“…investigated the effects of pore size distribution of porous Si 3 N 4 ceramics on their permeability. In addition, we have studied the relationships between pore structures of porous Si 3 N 4 ceramics and their permeation performance in previous works 12–14 …”