“…The biggest changes in spectra occur in a 1000 to 1500 cm −1 range after heating at 373-473 K. They result from removal of organic solvents residue from the bulk (isopropyl alcohol, acetic acid, and the corresponding ester). Fainting of bands d-h is correlated with decomposition of Pt complex at approximately 400 K. At the same time, appearance of a new band at 921 cm −1 , related to formation of SiO 2 (c)[35], can be observed. The peaks in the regions d-1018 cm −1 , e-1087 cm −1 are the complex's band from the Si-O-Si stretching vibrations and they are observable only in case of higher initial Pt concentration systems.…”
This paper presents new preparation method of Pt/SnO2, an important catalytic system. Besides of its application as a heterogenic industrial catalyst, it is also used as a catalyst in electrochemical processes, especially in fuel cells. Platinum is commonly used as an anode catalyst in low temperature fuel cells, fuelled with alcohols of low molecular weight such as methanol. Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex was used as a precursor of metallic phase. The aim of the research was to obtain a highly active in electrochemical system Pt/SnO2catalyst with low metal load. Considering small size of Pt crystallites, it should result in high activity of Pt/SnO2system. The presented method of SnO2synthesis allows for obtaining support consisting of nanoparticles. The effect of the thermal treatment on activity of Pt/SnO2gel was demonstrated. The system properties were investigated using TEM, FTIR (ATR), and XRD techniques to describe its thermal structural evolution. The results showed two electrocatalytical activity peaks for drying at a temperature of 430 K and above 650 K.
“…The biggest changes in spectra occur in a 1000 to 1500 cm −1 range after heating at 373-473 K. They result from removal of organic solvents residue from the bulk (isopropyl alcohol, acetic acid, and the corresponding ester). Fainting of bands d-h is correlated with decomposition of Pt complex at approximately 400 K. At the same time, appearance of a new band at 921 cm −1 , related to formation of SiO 2 (c)[35], can be observed. The peaks in the regions d-1018 cm −1 , e-1087 cm −1 are the complex's band from the Si-O-Si stretching vibrations and they are observable only in case of higher initial Pt concentration systems.…”
This paper presents new preparation method of Pt/SnO2, an important catalytic system. Besides of its application as a heterogenic industrial catalyst, it is also used as a catalyst in electrochemical processes, especially in fuel cells. Platinum is commonly used as an anode catalyst in low temperature fuel cells, fuelled with alcohols of low molecular weight such as methanol. Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex was used as a precursor of metallic phase. The aim of the research was to obtain a highly active in electrochemical system Pt/SnO2catalyst with low metal load. Considering small size of Pt crystallites, it should result in high activity of Pt/SnO2system. The presented method of SnO2synthesis allows for obtaining support consisting of nanoparticles. The effect of the thermal treatment on activity of Pt/SnO2gel was demonstrated. The system properties were investigated using TEM, FTIR (ATR), and XRD techniques to describe its thermal structural evolution. The results showed two electrocatalytical activity peaks for drying at a temperature of 430 K and above 650 K.
“…ATR-FTIR can distinguish the different polyanions (CMC vs PSS), but it is still qualitative and somehow speculative, especially because the Si–O broad band (from the silicon substrate) omits important information about the polymers. To solve this problem, we use the XPS high-resolution spectra for carbon and nitrogen.…”
Section: Discussionmentioning
confidence: 99%
“…67 On the other hand, only the PSS/ CHI spectrum presents a peak at 670 cm −1 , assigned to the S− OH group, and a peak at 1525 cm −1 , attributed to the aromatic CC bending, exclusive to the PSS chemical structure. 66 ATR-FTIR can distinguish the different polyanions (CMC vs PSS), but it is still qualitative and somehow speculative, especially because the Si−O broad band 68 (from the silicon substrate) omits important information about the polymers. To solve this problem, we use the XPS high-resolution spectra for carbon and nitrogen.…”
Chitosan-based thin films were assembled using the layer-by-layer technique, and the axial composition was accessed using X-ray photoelectron spectroscopy with depth profiling. Chitosan (CHI) samples possessing different degrees of acetylation ([Formula: see text]) and molecular weight ([Formula: see text]) produced via the ultrasound-assisted deacetylation reaction were used in this study along with two different polyanions, namely, sodium polystyrenesulfonate (PSS) and carboxymethylcellulose (CMC). When chitosan, a positively charged polymer in aqueous acid medium, was combined with a strong polyanion (PSS), the total positive charge of chitosan, directly related to its [Formula: see text], was the key factor affecting the film formation. However, for CMC/CHI films, the pH of the medium and [Formula: see text] of chitosan strongly affected the film structure and composition. Consequently, the structure and the axial composition of chitosan-based films can be finely adjusted by choosing the polyanion and defining the chitosan to be used according to its DA and [Formula: see text] for the desired application, as demonstrated by the antibacterial tests.
“…correlate with Si-O rocking 31 or with the silicon substrate. 32 No evidence for SiNO peak (expected to be at 3375 cm À1 ) following activation and exposure to air was detected.…”
Direct bonding may provide a cheap and reliable alternative to the use of adhesives. While direct bonding of two silicon surfaces is well documented, not much is known about direct bonding between silicon nitride and glass. This is unfortunate since silicon nitride is extensively used as an anti-reflection coating in the PV industry, often in contact with a shielding layer made of glass. A series of bonding experiments between glass and SiN was performed. The highest bonding quality, manifested by the highest bonding energy and lowest void area, was obtained with pairs that had been activated by nitrogen plasma followed by post-contact thermal annealing at 400 C. HRTEM imaging, HRTEM-EDS and EELS measurements performed on the thin films prepared from bonded samples by Focused Ion Beam (FIB) revealed a clear defect-free interface between the silicon nitride and the glass, 4 nm in thickness. ATR FT-IR measurements performed on activated surfaces prior to contact indicated the formation of silanol groups on the activated glass surface and a thin oxide layer on the silicon nitride. An increase in the bearing ratio of the glass following activation was noticed by AFM. A mechanism for bonding silicon nitride and glass is suggested, based on generation of silanol groups on the glass surface and on oxidation of the silicon nitride surface. The results point out the importance of exposure to air, following activation and prior to bringing the two surfaces into contact.
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