Mechanical property and gas filtration behavior of porous reaction bonded Si₃N₄ with monodispersed PMMA as pore former

Abstract

Porous Si 3 N 4 ceramics were prepared by gel casting combined with a reaction bonding route using monodispersed PMMA as the pore former, and Isobam was used as a gel agent. With the PMMA addition varying from 0 to 20 wt.%, the bending strength was degraded from 94.0 to 39.1 MPa owing to the increased porosity and decreased bulk density. The β-Si 3 N 4 prismatic grains and round pores introduced by the monodispersed PMMA micro balls would endow the samples with high strength, and the permeability of the resulting samples was increased obviously with the increase of PMMA addition. Flue gas filtration test exhibited that the filtration efficiency of the porous ceramics filter was not degraded with introducing of the PMMA pore former, even though the permeability was increased obviously. The block type of the sample with 20-wt.% PMMA additions during filtration was cake filtration, which indicates that the sample has the characteristic of being reusable after back-blowing in flue gas filtration applications. Porous Si 3 N 4 with high strength and permeability fabricated via the reaction bonding route exhibits great potential for low-cost high-performance ceramics filters.

Permeability and corrosion resistance of porous SiOC‐bonded SiC ceramics prepared by the preceramic polymer

“…Furthermore, the pore sizes detected by mercury injection were inconsistent with those observed by SEM 27 . This was because the mercury intrusion test can only detect the so‐called pore‐channel or pore‐neck 31 …”

“…Furthermore, the pore sizes detected by mercury injection were inconsistent with those observed by SEM. 27 This was because the mercury intrusion test can only detect the so-called pore-channel or pore-neck 31 Figure 9A shows apparent porosity and bulk density of porous SiC ceramics with different contents of PMMA. It can be seen that with the increase of PMMA content from 0 to 20 wt%, apparent porosity increased from 22.4% to 57.7%, whereas bulk density decreased from 2.18 to 1.29 g/cm 3 .…”

“…where 𝑑𝑃 𝑑𝐿 is pressure gradient, L is the sample thickness, P i is the pressure of the inlet gas, P o is the pressure of the outlet gas. 31 Permeability of the samples was determined by Darcy's Law (Equation ( 3)). 32…”

“…Gas permeability of airflow was evaluated using a laboratory‐made air‐permeator described elsewhere 29,30 . The pressure gradient in the sample was calculated using Equation (2) because of the compressibility of the air $$$$\begin{equation}{\rm{\;}}\frac{{dP}}{{dL}} = \frac{{P_i^2 - P_o^2}}{{2{P_o}L}},\end{equation}$$$$where $$\frac{{dP}}{{dL}}$$ is pressure gradient, L is the sample thickness, P i is the pressure of the inlet gas, P o is the pressure of the outlet gas 31 . Permeability of the samples was determined by Darcy's Law (Equation (3)) 32 …”