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The thermal insulating performance of expanded vermiculite is closely related to expansibility. A novel method of Mg2+ modification was proposed to improve the vermiculite expansion ratio. The modification process was characterised by energy dispersive X-Ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric-differential scanning calorimeter and scanning electron microscopy. Moreover, the thermal expansion experiment was performed to investigate the expansion behaviours of Raw-V and Mg–V samples at various temperatures. The result indicated that the introduction of Mg2+ could increase the vermiculite interlayer water content through hydration interaction, and the expansion ratio increased 13.7% under the heating temperature of 900 °C after modification. To explain the interaction of magnesium ion and water molecules, a molecular dynamics model was developed, and the simulation results were validated using the binding energy calculation. The results of this study can provide a new perspective and theoretical guidance for the commercial process of vermiculite expansion.

Aimed at improving vermiculite's thermal expansibility, a novel method of Na+ modification has been proposed. The modification effects were characterized via X-ray fluorescence spectroscopy, X-ray diffraction, and thermogravimetric-differential thermal analysis. The result indicated that sodium ions entered vermiculite interlayers through the exchange of interlamellar calcium ions. The effects of the heating time on the expansion ratio of Raw-V and Na-V samples were investigated at the temperature range of 400–700 °C. The result indicated that the maximum increment in the expansion ratio could reach up to 26.5% after Na+ modification. The influencing mechanism of Na+ modification on the thermal expansibility of vermiculite was explored via molecular dynamics simulation and the binding energy and dehydration enthalpy change calculation. The simulation and calculation results showed a good agreement with the expansion experiment result. This study provides a novel method for the preparation of high-performance expanded vermiculite.

In this study, a sugarcane bagasse biochar/nano-iron oxide composite was prepared via a one-pot pyrolysis method by using the sugarcane bagasse-based solid waste and microwave as the raw material and energy source, respectively. The developed composite was characterized by BET, XRD, FT-IR and TEM and was applied for the removal of Cr (VI) from water. The composite was observed to be mainly composed of amorphous carbon, Fe3O4 and Fe2O3. The iron oxides were uniformly embedded on the surface of the carbon layer by van der Waals force. The sugarcane bagasse-based biochar/nano-iron oxide composite material exhibited an optimal Cr (VI) adsorption capacity of 55 mg/g under the experimental conditions specified in this study. The Cr (VI) adsorption mechanism of the Fe2O3/Fe3O4/WBC composite was explained through FTIR, XPS, charge transfer analyses, and density functional theory calculations (DFT). The deposition of Cr (VI) on the surface of the composite was attributed to electrostatic interaction, redox reactions and complexation between the Fe2O3/Fe3O4/WBC composite and Cr (VI) contained in the solution.

This work investigated thermal stability of fumed silica based thermal insulating composites prepared by dry molding technology. The results showed that the composites could keep excellent thermal stability at the temperatures below 800 °C. However, when the samples were used at higher temperatures (>800 °C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed alumina could significantly improve thermal stability of the composites. When 5 wt.% fumed alumina was added, the volume shrinkage decreased from 10.49% to 3.47% at 1000 °C. The desirable results would be achieved by adjusting the amount of fumed alumina according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures.