2001, Elvers, Achim, Weißmann, Rudolf

In the past, wet chemical methods have been developed for the quantitative analysis of polyvalent elements in glasses. The major disadvantage of these chemical methods is that all structural information is lost during analysis. In addition, the analysis of species by wet chemical methods is unreliable due to possible redox reactions during the decomposition process. Therefore, the emphasis is on the physical methods which can directly detect species in bulk glasses. Especially optical and ESR spectroscopy are suitable methods due to their wide range of applications and sensitivity. Concerning quantitative measurements, no comparison between ESR results and chemical analysis of species has been published so far. This work discusses the possible application of ESR spectroscopy in the glass industry by focussing on routine interpretation, the correlation to chemical procedures and quantitative analysis. Results are presented and discussed for iron and chromium in packaging glasses. For example an excellent correlation was found between the Fe3+ ESR signal and the chemically determined Fe3+ concentration in glass.

2000, Janke, Nikolas, Grassmé, Oliver, Weißmann, Rudolf

Sodium diffusion from flat glass substrates during annealing changes properties of refined flat glass. In the ease of the development of the CuInSe2 thin film solar eell, annealing at 550 °C is necessary for the formation of suitable crystalline phases. Sodium diffusing from the soda-lime-silica glass substrate influences crystal growth and the main electrical parameters of the solar cell. Different possibilities in sodium ion migration control are presented, considering the influence of glass composition on sodium diffusion and its chemical potential as well as passivation of sodium-containing glasses by diffusion barriers. Experimental results in connection with the thin film solar cell show that sodium-free substrates or glass compositions which immobilise sodium at tetrahedral sites of boron oxide or alumina can be used without further surface treatment. Soda-lime-silica glass with sputter-deposited AI2O3 and BiOx thin films or CVD coatings (SiNx: H, SiOx) as diffusion barrier coatings shows promise as a cheap substrate material. Alternatively, dealkalisation of soda-lime-silica glass in HCl atmosphere leads to silica-rich surfaces with excellent barrier properties. The investigations are carried out using various surface analytical tools like Auger Electron Spectroscopy (AES), X-Ray Diffractommetry under Grazing Incidence (GI-XRD), high-resolution Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR).

2001, Beck, Alexandra, Weißmann, Rudolf

Cat scratches have become a chronic quality problem for the container glass industry but there is still controversy about their origin and how to eliminate them. Many tests related to appearance, shape, location, and chemical composition of this type of cord have therefore been made to get more information about them. As a result it can now be said that cat scratches are surface cords containing higher amounts of alumina and especially zirconia than the host glass. The cords form 10 to 20 µm thick bands located 10 to 60 µm below the surface. The origin of the problems is the corrosion of the refractory material. It is impossible to locate exactly the primary source because different mechanisms can create the cords. However, the main source is probably in the hot zone of the melter. The refractory-rich glass accumulates on the bottom of the tank where the overall flow makes it creep along the bottom of the whole furnace to the feeder outlet. The best ways to reduce the frequency of cat scratches are either appropriate drainage or mechanical stirring in the feeder channel.

2002, Hundhammer, Ines, Lenhart, Armin, Pontasch, Daniel, Weißmann, Rudolf

For the manufacturing and application of glass products, knowledge about residual stresses inside the glass plays an important role.With the scattered light method stresses can be measured with high spatial resolution at each point of a glass specimen regardless of its dimensions and without destroying the glass. It enables measurement of the whole stress profile in a specimen and measurement of stresses near edges and holes or investigation of the influence of temperature treatment on a stress profile. Thermal stresses as well as mechanically induced stresses can be measured in glass plates and also in tubular glass products.