Characterization of glass surfaces by X-ray reflectivity

Surfaces of soda-lime and borosilicate glasses produced by the float technique as well as polished BK-7, fused silica and aluminosilicate glasses are investigated by means of grazing incidence X-ray reflectometry Thin layers are found at all surfaces with properties which differ significantly from the bulk properties of the respective material. Fused silica surfaces exhibit a hydrated layer with a thickness of approximately 17 nm and a slightly reduced density Α thin leached layer with a density of approximately 2 g*cm⁻³ is analyzed on BK 7 glass. Α variadon in the rms roughness between 0.7 and 1.5 nm is found for aluminosilicate glasses depending on the polishing procedure. Pronounced differences are obtained between the air and the tin bath side of soda-lime float glass, whereas for borosilicate float glass only small differences in density between the two sides of the glass are measurable. The evolution of the initial stages of corrosion is demonstrated on soda-lime glass in dependence on the storage time

Grazing incidence X-ray reflectivity - a Round Robin test : Report of the International Commission on Glass (ICG) Technical Committee 19 "Glass Surface Diagnostics"

Densities and thicknesses of films of five different layer systems were determined in a grazing incidence X-ray analysis (GIXA) Round Robin test carried out by three industrial laboratories. The influence of both the experimental setup and the simulation software on these results is compared for the identical set of samples. Two approaches are adopted; firstly each laboratory measuring and simulating its own data and secondly each laboratory simulating the data that had been measured by another laboratory. The measured data from the three laboratories are analyzed and reasons proposed to explain the relatively minor differences between them. Comparisons are also made between the simulations produced from the two approaches to determine variations and any systematic bias between the three laboratories. Overall, good agreement in film densities and film thicknesses is found, demonstrating the high levels of accuracy that can be obtained from coating analysis using the GIXA technique

Composition of titania coatings deposited by different techniques

Quantitative dement concentrations in titania films produced by different deposition techniques (evaporation, sputtering, ion-assisted deposition, ion plating and dip coating) have been determined by means of Rutherford Backscattering Spectrometry and Nuclear Reaction Analysis with the reaction ¹H(¹⁵N, αγ)¹²C. Large differences of the hydrogen content are found for the various production techniques and the related deposition parameters, which correlate with the refractive index of the respective film. In dependence on the deposition conditions the oxygen/titanium ratio of the investigated titania films varies between 1.95 and 2.09. The impurities detected in the films (tantalum, molybdenum, silicon, argon, carbon, sodium) can be related to specific deposition conditions. Three multilayer interference systems containing TiO₂ and SiO₂ show large variations in hydrogen content resembling those found for single TiO₂ films

Multi-method characterization of soda-lime glass corrosion : Part 2. Corrosion in humidity Report of the International Commissionon Glass (ICG) Subcommittee of Technical Committee 19 "Glass Surface Diagnostics"

As-received and cleaned soda-lime glass surfaces corroded in high relative humidity of 95 % at a temperature of 60 °C for times up to one week are investigated by means of TOF-SIMS, SNMS, XPS, NRA, ERD, RBS, GIXR, AFM, SEM and optical microscopy. Distinct differences in the corrosion behavior are observed for as-received and cleaned glass surfaces. Changes in element concentration in the glass interface and in the topography of the glass surfaces are described for different exposure times in humidity. They are combined with variations in density of the modified surface layer. Cleaning before the corrosion treatment drastically reduces degradation; cleaning after the corrosion treatment can restore the surface

Rates and regulation of nitrogen cycling in seasonally hypoxic sediments during winter (Boknis Eck, SW Baltic Sea): Sensitivity to environmental variables

This study investigates the biogeochemical processes that control the benthic fluxes of dissolved nitrogen (N) species in Boknis Eck - a 28 m deep site in the Eckernförde Bay (southwestern Baltic Sea). Bottom water oxygen concentrations (O2-BW) fluctuate greatly over the year at Boknis Eck, being well-oxygenated in winter and experiencing severe bottom water hypoxia and even anoxia in late summer. The present communication addresses the winter situation (February 2010). Fluxes of ammonium (NH4+), nitrate (NO3-) and nitrite (NO2-) were simulated using a benthic model that accounted for transport andbiogeochemical reactions and constrained with ex situ flux measurements and sediment geochemical analysis. The sediments were a net sink for NO3- (-0.35 mmol m-2 d-1 of NO3-), of which 75% was ascribed to dissimilatory reduction of nitrate to ammonium (DNRA) by sulfide oxidizing bacteria, and 25% to NO3- reduction to NO2- by denitrifying microorganisms. NH4+ fluxes were high (1.74 mmol m-2d-1 of NH4+), mainly due to the degradation of organic nitrogen, and directed out of the sediment. NO2-fluxes were negligible. The sediments in Boknis Eck are, therefore, a net source of dissolved inorganic nitrogen(DIN = NO3- + NO2- + NH4+) during winter. This is in large part due to bioirrigation, which accounts for 76% of the benthic efflux of NH4+, thus reducing the capacity for nitrification of NH4+. The combined rate of fixed N loss by denitrification and anammox was estimated at 0.08 mmol m-2 d-1 of N2, which is at the lower end of previously reported values. A systematic sensitivity analysis revealed that denitrification and anammox respond strongly and positively to the concentration of NO3- in the bottomwater (NO3-BW).Higher O2-BW decreases DNRA and denitrification but stimulates both anammox and the contribution ofanammox to total N2 production (%Ramx). A complete mechanistic explanation of these findings is provided. Our analysis indicates that nitrification is the geochemical driving force behind the observed correlation between %Ramx and water depth in the seminal study of Dalsgaard et al. (2005). Despite remaining uncertainties, the results provide a general mechanistic framework for interpreting the existing knowledge of N-turnover processes and fluxes in continental margin sediments, as well as predicting the types of environment where these reactions are expected to occur prominently

Above- and belowground biodiversity jointly tighten the P cycle in agricultural grasslands

Experiments showed that biodiversity increases grassland productivity and nutrient exploitation, potentially reducing fertiliser needs. Enhancing biodiversity could improve P-use efficiency of grasslands, which is beneficial given that rock-derived P fertilisers are expected to become scarce in the future. Here, we show in a biodiversity experiment that more diverse plant communities were able to exploit P resources more completely than less diverse ones. In the agricultural grasslands that we studied, management effects either overruled or modified the driving role of plant diversity observed in the biodiversity experiment. Nevertheless, we show that greater above- (plants) and belowground (mycorrhizal fungi) biodiversity contributed to tightening the P cycle in agricultural grasslands, as reduced management intensity and the associated increased biodiversity fostered the exploitation of P resources. Our results demonstrate that promoting a high above- and belowground biodiversity has ecological (biodiversity protection) and economical (fertiliser savings) benefits. Such win-win situations for farmers and biodiversity are crucial to convince farmers of the benefits of biodiversity and thus counteract global biodiversity loss

Problem-oriented analysis of oxide layers on glass

Some representative characteristics of oxide coatings deposited on glass by different techniques have been described as well as several relevant methods of thin film analysis to determine their properties. Various special requirements of thin film analysis of oxide layers have briefly been outlined and the problem-solving process has been indicated. The potential of the problem-oriented use of the methods of thin film analysis has been demonstrated on the film properties composition, stress and density. The film density, which is determined by the deposition methods and production parameters, seems to be a key quantity which determines various other corresponding film properties

Mechanical and optical properties of SiO2 thin films deposited on glass

The optical and mechanical properties of amorphous SiO2 films deposited on soda-lime silicate float glass by reactive RF magnetron sputtering at room temperature were investigated in dependence of the process pressure. The densities of the films are strongly influenced by the process pressure and vary between 2.38 and 1.91 g cm(-3) as the pressure changes from 0.27 to 1.33 Pa. The refractive indices of the films shift between 1.52 and 1.37, while the residual compressive stresses in the deposited films vary in the range from 440 to 1 MPa. Hardness and reduced elastic modulus values follow the same trend and decline with the increase of process pressure from 8.5 to 2.2 GPa and from 73.7 to 30.9 GPa, respectively. The abrasive wear resistance decreases with the density of the films

Multi-method characterization of soda-lime glass corrosion : Part 1. Analysis techniques and corrosion in liquid water Report of the International Commission on Glass (ICG) Subcommittee of Technical Committee 19 "Glass Surface Diagnostics"

Corroded soda-lime float glass surfaces prepared in water (room temperature and 60 °C) or air (relative humidity of 95 %, 60 °C) for different times are invesdgated by means of SIMS, SNMS, XPS, NRA, ERD, RBS, GIXR, AFM, SEM, light microscopy and scratch testing. The corrosion effects are studied for as-received and cleaned glass surfaces. Changes in the dement concentration in the glass interfaces with the immersion time in water are described. They are combined with variations in density of the surface layer which exhibits plastic deformation behaviour. Inhomogeneous corrosion leads to changes in the topography and an increase in surface roughness