Simultaneous effects of rice husk silica and silicon carbide whiskers on the mechanical properties and morphology of sodium geopolymer

The current research is focused on developing a geopolymer binder using rice husk ash–derived silica nanoparticles. Four types of rice husks were collected directly from various rice fields of Bangladesh in order to evaluate the pozzolanic activity and compatibility of the derived rice husk ashes with precursors of sodium-based geopolymers. Silicon carbide whiskers were introduced into sodium-based geopolymers in order to evaluate the response of silicon carbide whiskers to the interfacial bonding and strength of sodium-based geopolymers along with rice husk ashes. Compression, flexural and short beam shear tests were performed to investigate the synergistic effect of rice husk ashes–derived silica and commercially available silicon carbide whiskers. Results show that rice husk ashes–derived spherical silica nanoparticles reduced nano-porosity of the geopolymers by ∼20% and doubled the compressive strength. The simultaneous additions of rice husk ashes and silicon carbide whiskers resulted in flexural strength improvement by ∼27% and ∼97%, respectively. The increase in compressive strength due to the inclusion of silica nanoparticles is related to the reduction in porosity. The increase in flexural strength due to simultaneous inclusion of silica and silicon carbide whiskers suggest that silica particles are compatible with the metakaolin-based geopolymers, which is effective in consolidation. Finally, microscopy suggest that silicon carbide whiskers are effective in increasing bridged network and crack resistance.

Synergy Effects in Electromagnetic Properties of Phosphate Ceramics with Silicon Carbide Whiskers and Carbon Nanotubes

Hybrid composite materials based on an aluminium phosphate matrix with silicon carbide whiskers and multi-walled carbon nanotubes were studied in a wide frequency range (20 Hz to 36 GHz). It was demonstrated, that the addition of the silicon carbide whiskers enhances the dielectric permittivity and conductivity. This was explained by the difference in tunnelling parameters. Hybrid ceramics with nanotubes and whiskers also exhibits substantially improved electromagnetic shielding properties. The hybrid ceramics with 10 wt. % silicon carbide whiskers and a 1 mm thick 1.5 wt. % carbon nanotube layer, show higher than 50% absorption of electromagnetic radiation.

Preparation and characterizations of SiCw/SEBS-g-MAH composite film

Silicon carbide whiskers (SiCws) were modified with silane coupling reagent with the aid of ultrasonic agitation, and SiCw/SEBS (styrene-ethylene-butadiene-styrene) grafted with maleic anhydride(SEBS- g-MAH) composites were prepared by a solution method. The effects of modification on the SiCw and the structure morphology, mechanical property, thermal stability, and hydrophobicity of composites were studied. The results show that the tensile strength of composites increased gradually with increasing filler contents, ranging from 19.05 to 24.91 MPa. The pyrolysis temperature of composites to begin to lose mass increased gradually. Comparing with the pure SEBS- g-MAH film beginning to lose mass at 365°C, the composite with 2.5% modified SiCw lost mass at 402°C, which had improved by 37°C. With increasing content of SiCw, the hydrophobicity of composite was enhanced. Compared with the pure SEBS- g-MAH film, the water contact angle of composite with 2.5% SiCw had been enlarged by 40%, from 65.56° to 91.57°.