Thermal decomposition of silylated layered double hydroxides

Anionic surfactant and silane modified layered double hydroxides (LDHs) were synthesized through an in situ coprecipitation method. The structure and morphology were characterized by XRD and TEM techniques, and their thermal decomposition processes were investigated using infrared emission spectroscopy (IES) combined with thermogravimetry (TG). The surfactant modified LDHs (H-DS) shows three diffractions located at 1-7A degrees (2 theta), while there is only one broad reflection for silane grafted LDHs (H-Si) in this region. The morphologies of the H-DS and H-Si show fibrous exfoliated layers and curved sheets, respectively. The IES spectra and TG curves indicate that alkyl chain combustion and dehydroxylation are overlapped with each other during heating from 373 to 723 K in H-DS and to 873 K in H-Si. Sulfate anion transformation process occurs at 473 K in H-DS and 523 K in H-Si. The derivant of sulfate can exist even above 1073 K. After further decomposition, the metal oxides and the new type of Si-O compounds are formed beginning at around 923 K in silane modified sample.