Synthesis and mechanical properties of lightweight hybrid geopolymer foams reinforced with carbon nanotubes

Abstract

A lightweight hybrid geopolymer foams reinforced with carbon nanotubes (CNTs) was exploited by adding the CNTs into geopolymeric matrix through hydrogen peroxide method. The synergistic effects of nanotubes and foaming agent on the phase evolution, microstructure, and mechanical properties were investigated. After introduction of nanotubes, the geopolymer foams reinforced with CNTs (CNTs/KGP) still showed amorphous structure. Porosity of the foams increased with the H2O2 content and decreased with the increase in CNTs content. The addition of CNTs (1‐9 wt%) in foams refined the distribution of pore size from 523 to 352 μm. Compression strength of the CNTs/KGP samples elevated with the increasing content of CNTs, which was contributed to the crack propagation and bridging of CNTs in foams. The CNTs/KGP foams with considerable porosity show potential applications in adsorption, filtration, membrane supports, other industries, etc

In situ growth of SiC wires on CVI densification of SiC foam

“…The higher rate of oxidation of SiC in SiC (PIP) foam can be attributed to the more diffusion of oxygen through the voids and cracks in the struts. 11 In SiC foam (PIP/CVI), the presence of in-situ formed crystalline SiC nanowires restricted the diffusion of oxygen within the struts of SiC foam. 31 Hence, the SiC conversion to silica in SiC (PIP/CVI) was limited.…”

“…However, higher weight gain was obtained for SiC foam (PIP) (weight gain of 19.5%) compared to the weight gain of SiC foam (PIP/CVI) (weight gain of 3.3%). The higher rate of oxidation of SiC in SiC (PIP) foam can be attributed to the more diffusion of oxygen through the voids and cracks in the struts 11 . In SiC foam (PIP/CVI), the presence of in‐situ formed crystalline SiC nanowires restricted the diffusion of oxygen within the struts of SiC foam 31 .…”

“…4,5 In general, the low cost of raw materials and the simplicity of the process is highly encouraging and hence proposed for the preparation of open-cell SiC foam for many applications such as filters for molten metal, hot gas and ion exchange filtration, thermal protection systems, heat exchangers, solar receivers, catalyst support, and refractory linings. [6][7][8][9][10][11] However, the low strength of the foams produced from phenolic resin-based precursor slurry/suspension is a major constraint for the above applications. 12 Moreover, the foams have to be further densified by repeated PIP cycles to achieve the required handling strength.…”

“…Phenolic resin‐based precursor slurry/suspension is extensively used for the preparation of open‐cell SiC foam by polymer infiltration and pyrolysis (PIP) route using polyurethane (PU) foam as the replica substrate 4,5 . In general, the low cost of raw materials and the simplicity of the process is highly encouraging and hence proposed for the preparation of open‐cell SiC foam for many applications such as filters for molten metal, hot gas and ion exchange filtration, thermal protection systems, heat exchangers, solar receivers, catalyst support, and refractory linings 6–11 . However, the low strength of the foams produced from phenolic resin‐based precursor slurry/suspension is a major constraint for the above applications 12 .…”