Porous microspheres of Mg–Al layered double hydroxide (LDH) were fabricated in large scale through a simple sonication-assisted method in the mixed solvent of ethylene glycol and water. Contrast experiments showed that sonication and ethylene glycol both played important roles for the formation of the porous nanostructures of Mg–Al-LDHs. A series of techniques of XRD (X-ray Diffraction), FTIR (Fourier Transmission Infrared Spectroscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), BET (Brunauer-Emmett-Teller surface analysis) and TG–DTA (Thermalgravimetric–Differential Thermal Analysis) were used to characterize the product. Laboratory-scale fire extinguishment tests showed that thus-prepared porous LDHs showed much superior performance to that of the solid particulate counterpart for relatively shorter extinguishing time and smaller amount of agents required. Such an improvement could be reasonably ascribed to the special porous structure and nanosize of as-prepared Mg–Al-LDHs microspheres.
Keywords: Layered double hydroxide; Porous; Synthesis; Fire suppression
Fig. 1. XRD patterns of as-prepared Mg–Al-LDHs, inset was the corresponding FTIR spectra: (a) sample A, (b) sample B.
Fig. 2. (a) Panoramic SEM images of as-prepared Mg–Al-LDHs spheres, (b) magnified SEM image of the spheres, (c) TEM image of the sphere, (d) and (e): SEM images of the sample prepared without sonication, (f) SEM image of the sample prepared in aqueous solution, (g) SEM image of the sample prepared in pure EG.
Fig. 3. N2 adsorption–desorption isotherms and pore size distribution (inset) of two samples: (a) sample A, (b) sample B.
Fig. 5. SEM images of the samples prepared under different sonication conditions: (a) 40 kHz, 4 h; (b) 40 kHz, 12 h; (c) 20 kHz, 8 h, (d) 60 kHz, 8 h.
Fig. 6. Images of the flame during the fire suppression process by the two samples: (a) sample A, (b) sample B.
Fig. 7. Variations of the flame temperatures with time during the fire suppression process by the two samples: (a) sample A, (b) sample B.
The extinguishing time (tE) and the weights (mE) of the powder consumed in different fire extinguishing experiments.
Corresponding author. State Key Lab of Fire Science, University of Science and technology of China, Hefei, Anhui 230036, PR China. Tel.: +86 551 3607276; fax: +86 551 3601669.