9 results
Search Results
Now showing 1 - 9 of 9
- ItemEigenschaften von niedrigschmelzenden Phosphatgläsern(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Vaivads, Janis; Weißmann, Rudolf[no abstract available]
- ItemStress measurement in transparent materials using scattered laser light(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Hundhammer, Ines; Lenhart, Armin; Pontasch, Daniel; Weißmann, RudolfFor 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.
- ItemEnamelling of glass by CO₂ laser treatment(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Buerhop, Claudia; Weißmann, RudolfDecoration of glass using enamel is interesting for hollow glassware as well as for flat glass sheets. Laser radiation can be used advantageously to increase the temperature of the product locally. The reactions which take place during CO₂ laser heat treatment of a conventional PbO-containing frit are discussed intensely. Pyrometrical temperature measurements accompany the experiments to investigate the temperature development during CO₂ laser irradiation. At temperatures above Tg optimal results concerning low surface roughness, high brightness and intensive colouration are obrained without deformation of the shape of the product. Very promising results show that higher temperatures can be achieved by laser application and therefore PbO-free frits can be used.
- ItemESR spectroscopy - an analytical tool for the glass industry(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Elvers, Achim; Weißmann, RudolfIn 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.
- ItemFirimg PbO - free glass enamels using the CW - CO₂ laser(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Hahn, Karlheinz; Buerhop, Claudia; Weißmann, RudolfThe firing of glass enamels, which are applied to decorate glass products, is usually done in a furnace. Α new and suitable technique for firing glass enamels is to make use of the high-power CW-CO₂ laser. Its be am (wavelength 10.6 μm) induces a very fast heating of the enamelled glass within a small surface layer. This makes it possible to fire glass enamels at temperatures above 1000°C, without any deformation of the Substrate glass body In this temperature ränge an amount of the harmful component PbO in t he glass enamel is n o longer necessary The PbO-free glass flux of the enamel is made easily by milhng the Substrate glass (float glass). The gloss and smoothness of the laser-fired enamel are comparable to the conventionally fired enamel. The absence of PbO and the high firing temperatures are very advantageous to the chemical resistance of the enamels, meaning excellent dishwasher durability.
- ItemMachining of silica glasses using excimer laser radiation(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Hornberger, Helga; Weißmann, Rudolf; Lutz, NorbertVarious silica glasses were engraved deliberately by excimer laser radiation using wavelengths of 308 and 248 nm. The ablation of different samples was investigated by systematic Variation of the processing parameters. The ablation rates were determined using profilometry and gravimetric measurements by evaluating the processing quaUty and the morphology of the processed surfaces was considered. The phenomenon of ablation is explained as a non-linear interaction of the laser beam and the glass. The experimental results show that the ablation behaviour of silica glass depends on the wavelength and the intensity of the laser radiation, on the surface quahty and the degree of purity of the glass. Although high ablation rates were obtained, the suitability of excimer lasers for micromachining is restricted due to the rough surface morphology and poorly defmed edges.
- ItemComparative studies of the corrosion and long-term stability of vitrified e-filter dust from waste incinerators, granules from hightemperature waste incineration plants and a model glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Menzler, Norbert H.; Mörtel, Heinrich; Weißmann, RudolfThe objective of this study was to describe the corrosion behaviour of vitrified residues of municipal waste incinerators by using standardized short-term and long-term leaching and corrosion test methods. The results for the vitrified product were compared to the results for granules from high-temperature waste incineration plants and a model glass. The test methods used in this work are, on the one hand, a German and a Swiss test [1 and 2] to describe the possibility for the disposal of waste and, on the other hand, test methods [3 and 4] to characterize the corrosion behaviour of glass products. The results according to the different methods and their changing test parameters like temperature, corrosion time and leaching Solution are presented.
- ItemInvestigation of cat scratches on container glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Beck, Alexandra; Weißmann, RudolfCat 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.
- ItemAlkali ion migration control from flat glass substrates(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Janke, Nikolas; Grassmé, Oliver; Weißmann, RudolfSodium 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).