Highly Porous Silicon Nitride Foam Prepared Using a Route Similar to the Making of Aerated Food

Abstract

A new foaming route, which was imitated from the foaming of aerated foods, was used by the protein foaming method in preparing highly porous silicon nitride (Si 3 N 4 ) foams. Effects of air fraction on the structure and property of the products were investigated. It was indicated that the porosity increased with the air fraction exponentially, whereas the air fraction had little effect on the average pore sizes of Si 3 N 4 foams. Thermal conductivity of the product measured using the laser flash method decreased from 4.07 to 2.29 W/(mÁK) when the porosity increased from 80.00% to 87.61%.

Anisotropic, biomorphic cellular Si3N4 ceramics with directional well-aligned nanowhisker arrays based on wood-mimetic architectures

“…We compared the TC of the bio-Si 3 N 4 ceramics with other porous silicon nitride ceramics prepared by other methods, such as freeze-drying method [39] and foaming method [40,41]. Although the porosity is similar (60%-80%), the TC of bio-Si 3 N 4 is considerably higher than that of porous Si 3 N 4 ceramics (0.08-0.1 W•m −1 •K −1 ) by sol-gel and freeze drying [39].…”

Formation mechanism of porous reaction-bonded silicon nitride with interconnected pores in the presence of MgO

“…In production of cellular Si3N4, there have been several successful manufacturing techniques, e.g. aqueous gel-casting [11], spray-dried method [12], protein foaming [13], sacrificial template [7,14], emulsions, and replication of polymer foams [2]. However, the significant disadvantages of these processes are high cost of the starting silicon nitride powder and difficulty with machining of the final components which have limited their widespread usage.…”

Extrusion of highly porous silicon nitride ceramics with bimodal pore structure and improved gas permeability

“…To date, highly porous Si 3 N 4 ceramics have been fabricated by various processing routes including addition of fugitive inclusions, replica, direct foaming, and ice‐templating method . Indeed, different routes have their respective advantages.…”

“…When used as DPF, porous Si 3 N 4 should be designed to possess as high as porosity, while maintaining enough mechanical strength and filtration efficiency, because high porosity can improve exhaust permeability and lower the pressure loss of DPF, thus improving fuel economy. 7,8 To date, highly porous Si 3 N 4 ceramics have been fabricated by various processing routes including addition of fugitive inclusions, 9 replica, 10 direct foaming, 11 and icetemplating method. 1,12 Indeed, different routes have their respective advantages.…”