Effect of metal dopant in silica sol-gel reaction
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Date
2019-06
Authors
Aziatul Atika Binti Roslan
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Abstract
Silica membrane becomes one of the important ceramic product due to its properties that
suitable in gas separation processes. The sol-gel method is used to synthesis the
microporous silica material due to its simplicity and the high degree of nanoscale
homogeneity which vital for good separation. Therefore, the aim of this study is to
investigate the effect of metal dopant on the silica structure via sol-gel method. In this
study, the silica xerogel (powder) is prepared via the sol-gel method instead of the silica
membrane as it is easier to optimise material characteristic in material form. There are
various types of metals being doped into the silica solution to investigate their effect on
silica structure such as Nickel (II) Chloride Hexahydrate (NiCl2.6H2O), Cobalt (II)
Chloride Hexahydrate (CoCl2.6H2O), Copper (II) Chloride dihydrate (CuCl2.2H2O).
However, only the effect of nickel is further studied at different molar ratio of Ni/Si (0.02,
0.03, 0.04 and 0.05) and calcination temperature (430°C, 530°C, 630°C and 730°C).
Besides, different ratio of alkoxide/water, Rw is studied to investigate the effect of Rw on
silica structure. The UV-Vis spectrophotometer and FTIR spectra are used to analyse the
effect on silica structure. The result shows that Si-O-Me formed in metal-doped silica
structure lead to lower formation of siloxane bond. This results in small pore size of
metal-doped silica structure compared to pure silica structure. Next, the higher the
concentration of NiCl2.6H2O, the smaller the pore size of silica due to the higher
formation of Si-O-Ni bond. Besides, silica structure is less hydro-stable at lower the
alkoxide/water ratio, Rw due to the higher formation of silanol which leads to the lower
formation of siloxane bond. Lastly, the optimum calcination temperature to synthesis
silica nanoparticle is 630°C