Insights into the physicochemical aspects from natural halloysite to silica nanotubes

Properties and applications of halloysite nanotubes: recent research advances and future prospects

“…After treatment with 1 M NaOH for 84 days, the average internal diameter increased to 22.8 nm, the average wall thickness decreased to 11.4 nm, and the average external diameter remained unchanged. A similar increase in SSA and V pore with treatment time, as well as the destruction of the AlO 6 octahedral layer structures and the formation of amorphous silica nanoparticles were observed by Zhang et al (2012a) and Abdullayev et al (2012). However, to test the stability of Hal over a relatively short time (b60 h), an acid was used with a higher concentration, i.e.…”

Physicochemical characterization of organosilylated halloysite clay nanotubes

“…The mass loss profiles of all materials are very similar and show a very small mass loss in the range of 25-150 ºC and two main mass losses from 200-340 and 365-616 ºC. The first very small mass loss is due to the removal of physically adsorbed water from the HNTs surface and is not significant neither in the pristine HNTs (0.5%) nor in the silylated HNTs (0.2-0.3%); 33 nevertheless, in the functionalized materialsthis mass loss decreases compared to that of the pristine material, which is due to the fact that some residual water present is consumed during the silylation reaction 4,22,33,34. For the pristine HNTs, the first substantial loss in the range of 220-310 ºC(Table 4) is attributed to the gradual loss of the residual interlayer water35 and the second substantial loss at approximately 405-570 ºC is ascribed to the dehydroxylation of the structural aluminol groups (Al-OH).…”

“…4,9,22,34 For 27 Al spectra, Table 5 and Signals T 3 and T 2 corresponds to, respectively, 3-and 2-fold covalent grafting of the organosilanes to HNTs, through reaction between three or two methoxy/ethoxy groups and the OH groups from the HNTs structure. For materials HNTs_APTES (Figure 4(b)), HNTs_AEAPTMS and HNTs_PhTES it was possible to identify silicon T 3 and T 2 signals, but…”

Synthesis of nano-sized silicon from natural halloysite clay and its high performance as anode for lithium-ion batteries

“…In addition, some holes appeared on the surface of the wall, which hints the structural damages during the dealumination process and the porous structure of HeSiO 2 . In addition, a study on acid etching of halloysite reported similar results [40,41].…”