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A quantitative XPS examination of UV induced surface modification of TiO2 sorbents for the increased saturation capacity of sulfur heterocycles
摘要： UV pretreatment has proven effective in enhancing the sulfur heterocycle specificity and saturation capacity of TiO2 adsorbents. Previous efforts in our laboratory have shown this effect to persist for over two weeks and were attributed to increased densities of surface hydroxyl groups as assessed by XPS and FTIR evaluations. This paper presents further evidence of the previous assertion by tracking the UV-induced conversion of adsorbed water and lattice oxygen into surface hydroxyls as monitored by XPS. Two different commercial TiO2 adsorbents (@ 163 and 70 m2/g) were investigated at various hydration levels as determined by TGA. Deconvolution of the XPS spectra demonstrated both the qualitative nature and quantitative conversion of adsorbed water and lattice oxygen according to the following stoichiometry, where one lattice oxygen is converted into two surface hydroxyls. Eight different reaction cases were examined using the 163 and 70 m2/g supports at four different hydration levels each. The measured stoichiometry for the above-noted conversion varied from 1.83 to 2.15 with an average value of 1.98 and a standard deviation of 0.10. Samples removed from the XPS chamber and stored in laboratory conditions showed that photo-generated surface hydroxyls could persist for over two weeks with or without handling.
关键词： XPS,TGA,Hydroxyl group,Titanium dioxide,UV,Photo-assisted adsorptive desulfurization
更新于2025-09-10 09:29:36
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Optical bonding of tellurite glass film on silicate glass
摘要： Tellurite glass thin film was successfully bonded on a silicate glass substrate by the direct bonding (DB) method. Glass film (thickness 1-3 μm) was fabricated by the glass blowing technique and the DB process was performed at room temperature at relative humidity (RH) of 62% or 15%. The surface adhesive strengths of the glass films bonded at 15% and 62% RH were measured as 250 and 96 mJ/m2 respectively by the Obreimoff-Metsik method. The hydroxyl (-OH) functional groups on the interface between the film and silicate glass were analyzed by Fourier transform infrared spectroscopy. The major bonding forces between the tellurite thin film and silicate glass were hydrogen bonds at 62% RH and bonds between Te on the tellurite glass and O on the silicate glass were concerned at 15% RH. These forces, contributed by Si-OH, were important for bond formation at 62%. The large amounts of water and OH groups on the silicate glass, determined by thermogravimetric analysis, indicated a weaker bonding process at 62% RH. This work will contribute toward reliable, high-integrity components for integrated optical circuits, which are increasingly needed for high-throughput data transfer.
关键词： glass thin film,tellurite glass,hydroxyl group,adhesive strength,direct bonding
更新于2025-09-04 15:30:14