TITLE:
In-Situ Hydroelectrothermal Deposition of Silicate Layers on Stainless Steel Surfaces
AUTHORS:
Jaybalan Tamahrajah, Axel Brehm
KEYWORDS:
Hydroelectrothermal Deposition, Silica, Stainless Steel, Silicates, Linear Sweep
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.5 No.9,
September
8,
2015
ABSTRACT: The deposition of
zeolites on solid support materials is possible by means of electrochemical
methods, impregnation processes, as well as in-situ syntheses. Electrochemical deposition of zeolites has been reported as well,
however with readily synthesized zeolite structures. Adhesive deposition of
zeolites on stainless steel (S316) has been reported. This report investigates
the feasibility of the deposition of silicates by in-situ hydroelectrothermal means. The
investigation was done in aqueous solutions of pH = 7 to 13 at different
temperatures (25°C to 70°C) by linear sweep method. Deposition was done at a
saturated H2 atmosphere to ensure prior deposition of thin iron
oxide film on the surface and formation of Fe-O-Si-linkages. This was proven by
Raman measurement of the samples. Further linear sweep experiments in the
presence of silica show monodentate and bidentate Fe-O-Si linkages on the
surface, proven by IR-measurements. Presence of dissolved silica was done by
UV-Vis with the molybdate yellow method. The best results are achieved at 70°C
at pH 13 and ﹣4 mV (vs Ag/AgCl) or 200 mV (vs SHE). Discontinuous homogeneous
layers are found on the stainless steel surface observed by SEM, EDX measurements
and electrochemical measurements. Layer discontinuties are caused due to low
silica concentration at equilibrium hydrothermal conditions, especially in the
absence of silicic acid. All results shown are for the best results achieved
except for linear sweep measurements and solubility constants of dissolved silica.