Investigation of structure of a thin SiO₂ layer as an antifouling and corrosion-resistant coating

Abstract

The structures of a SiO 2 layers synthesized using perhydropolysilazane [PHPS, labeled as SiO 2 (PHPS)] on both Si and Fe/Si substrates were studied using Fourier transform infrared spectroscopy (FT-IR) and neutron reflectivity (NR) analysis. The FT-IR results revealed that no unreacted PHPS remained and that the primary component of the SiO 2 (PHPS) layer could be considered to be SiO 2 . The NR analysis suggested that a uniform SiO 2 (PHPS) layer was synthesized on the Si and Fe/Si substrate and that the density of this SiO 2 (PHPS)layer was lower than that of natural SiO 2 . In addition, the density of the SiO 2 (PHPS) layer was altered by varying both the thickness and the type of substrate used. These results indicated that the variation in the density of the SiO 2 (PHPS) layer depended on the efficiency of cross-linking reaction between the silazane oligomers in the PHPS coating.

Structural Study of Silica Coating Thin Layers Prepared from Perhydropolysilazane: Substrate Dependence and Water Penetration Structure

“…Table 1 shows the structural parameters obtained from this analysis. The structural parameters of the PDS/Fe/Si sample, that is the results of our previous work [5], are also shown in Table 1 to highlight the influence of the substrate on PDS nano-structure. The thickness (t) and scattering length density (SLD, ρ) values of the PDS thin layers were estimated to be 461 Å and 2.10 × 10 −6 Å −2 for PDS/Si, 436 Å and 1.86 × 10 −6 Å −2 for PDS/Al 2 O 3 , 1809 Å and 1.00 × 10 −6 Å −2 for PDS/MgO, and 430 Å and 1.99 × 10 −6 Å −2 for PDS/PVA/Si samples, respectively.…”

“…The Motofit program [16] was used to fit the NR profiles using the least-squares approach to minimize deviations in the fit; the thickness, scattering length density (SLD) [5], and Gaussian roughness were evaluated by the program.…”

“…Inorganic precursors, sush as perhydropolysilazane (PHPS, Figure 1), are one of the more promising materials for protection of these materials because inorganic precursors can be easily used to synthesize high-quality thin SiO 2 layers by hydrolysis or oxidation [1,2]. In fact, PHPS was applied in transparent gas barrier materials [3], thin-film light addressable potentiometric sensors [4], and waterproofing layer of metal magnetic material [5]. The major concern with using silicon-based materials is that the formation behavior of SiO 2 layers may change depending on the nature of the surface or condition of the PHPS-protected material.…”

“…Their studies revealed that the curing reaction relies mainly on the activation of Si-H and Si-N bonds by OH group containing substances such as water, which promotes subsequent cross-linking of intermediate silanols via condensation reactions. Akutsu et al [5] studied the effect of synthesized SiO 2 layer thickness on the density of SiO 2 layers, and their studies showed that the density of SiO 2 layers depends on the efficiency efficiency of cross-linking reaction between silazane oligomers in coated PHPS layers. Nevertheless, further research on the nano-structure and detailed synthesis mechanisms for the preparation of SiO2 layers is important for the development of silicon-based coating materials.…”

“…Nevertheless, further research on the nano-structure and detailed synthesis mechanisms for the preparation of SiO2 layers is important for the development of silicon-based coating materials. A variety of techniques, such as Fourier-transform infrared spectroscopy (FT-IR) [8,11], X-ray photoelectron spectroscopy (XPS) [8,11], and neutron reflectivity (NR) [5], have been used to study the structure of PHPS-derived silica (PDS) thin layers. Since the thickness, density, and roughness of the thin layer samples can be determined by NR techniques [12,13], here we use NR techniques to elucidate the nano-structure of PDS thin layers.…”