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- ItemZerstörungskennlinien für Verbundsicherheitsglasscheiben(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Mayrhofer, Christoph; Kranzer, CarolineFür die Bewertung des Tragverhaltens von Bauteilen bei Explosionsereignissen sind sogenannte „Druck-Impuls-Diagramme" erforderlich. Diese geben in Abhängigkeit vom Druck und dem Impuls der Belastung an, für welche Wertepaare Zerstörung eintritt und welchen Belastungswerten das betrachtete Bauteil standhält. Derartige Zerstörungskennlinien sind am Fraunhofer EMI für eine Vielzahl von Werkstoffen entwickelt worden. Den Zerstörungskennlinien liegt das Rechenmodell des Ein-Massen-Schwingers zugrunde. Voraussetzungen für seine Anwendbarkeit sind Biegetragmechanismen, Bruch- bzw. Zerstörungskriterien (z.B. Grenzdurchbiegung) und die Kenntnis des statischen Last-Verformungsverhaltens. Untersuchungen ergaben, daß Verbundsicherheitsglasscheiben die Voraussetzungen für die Erstellung von Zerstörungskennlinien erfüllen. Es wird eine Näherungsmethode zur Erfassung des statischen Tragverformungsverhaltens unter Berücksichtigung von Membranspannungszuständen dargestellt. Am Beispiel anderer Werkstoffe wird die prinzipielle Vorgehensweise erläutert, da für Verbundsicherheitsscheiben bisher noch keine Bruchkriterien zur Verfügung stehen.
- ItemCollaborative study into the analysis of total selenium and selenium valence states in glass - a general method by hydride generation atomic absorption spectrometry and photometry : Report of the International Commission on Glass (ICG) Technical Committee 2 "Chemical Durability and Analysis"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Guadagnino, Emanuel; Çorumluoğlu, OrhanWhilst the determination of total selenium in glass is of great relevance to environmental purposes, the measurement of the oxidation states of selenium which may arise under different redox conditions may contribute to clarify the mechanisms of colour formation. In the proposed method, the determination of total selenium is carried out by hydride generation atomic absorption spectrometry (HGAAS) on three different glasses covering the range of selenium content between 10 and 130 mg/kg of glass. To prevent losses during the decomposition step, selenium is converted into a nonvolatile form as selenate (Se6+). When the sample is decomposed, the HCl Solution (c(HC1) = 10 mol/l) is made and selenium is pre-reduced to Se4+ by heating for 2 h at 80 °C. The determination of selenium oxidation states requires a stepwise approach. The measurement of Se0 is based on its insolubility in HF. After the sample is decomposed, Se0 is filtered off, dissolved from the filter with a HBr-Br2 mixture and finally measured by HGAAS. Se4+ and Se6+ are recovered in the filtrate of the same sample and determined together after conversion of Se4+ into Se6+. Se4+ is determined in the same filtrate by photometry with o-phenylenediamine (OPDA).
- ItemInfluence of modifier cations on the radiation-induced effects of metaphosphate glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Ebeling, Polina; Ehrt, Doris; Friedrich, ManfredThe influence of different modifying cations on the radiation-induced defect generation in metaphosphate glasses was studied by optical absorption and electron paramagnetic resonance spectroscopy. For this task, several model glasses were prepared. These were simple metaphosphates of alkaline earths, aluminum and zinc. The synthesized glass samples were irradiated with X-rays and with UV light from an Xe/Hg lamp. The cation-dependent differences in the structure of the phosphate glasses were found to have a great influence on the concentration of some radiation-induced defects and thus on the optical absorption. The influence of the different cations became especially distinct under UV light Irradiation due to the selective interaction of the UV light with the glass samples. Some additional phenomena were observed for the irradiated zinc and magnesium metaphosphate glasses which were not found by the previously undertaken study of complex phosphate glasses.
- ItemApplication of electrical heating in forehearth channels(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2003) Grössler, JürgenElectrical heating of forehearth channels can be either indirect with radiant heating elements installed above the glass surface, or direct utilizing immersed electrodes. Two types of heating elements are used, made of either silicon carbide or molybdenum disilicide. Electrodes are normally made of molybdenum, but tin oxide is also used, and platinum alloy may be required for some special applications. Direct electrical heating is also used in forehearths to supplement the traditional gas heating, and can provide a significant improvement in the thermal homogeneity of the glass at the end of the channel. Excellent results can also be obtained with full electrical heating. Whatever type of electrical heating is used, the relevant safety standards must be applied.
- ItemPostmortem analyses of salvaged conventional silica bricks from glass production furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Wereszczak, Andrew; Wang, Hsin; Karakus, Musa; Curtis, Warren; Aume, Victor; VerDow, DennisThe microstructure, phase content, and thermal conductivity of salvaged conventional silica bricks from float glass and TV-panel glass production furnaces were examined as a function of position through the brick, and compared with the original, unaltered brick materials. The silica brick from the float glass furnace was in service for approximately 10 years while that for the TV-panel glass furnace was for approximately 6 1/2 years. The microstructure and phase content in both salvaged bricks showed gradients, from tridymite at the bricks' cold-face ends, to cristobalite at their hot-face end even though both bricks were an initial mixture of tridymite and cristobalite to begin with. The thermal conductivity of both bricks had increased as a consequence of these phase and microstructural changes. Α thermal analysis model predicted that such changes would result in an increase in the bricks' cold-face temperature and heat content during service. The initially-produced temperature gradients and environment caused microstructural changes in the silica brick; however, the cause-and-effect relationship between temperature/environment and microstructural changes in the brick likely became mutually reversible once the microstructural changes initiated and the thermal conductivity of the brick started to change as a consequence.
- ItemDevelopment of organic-inorganic coatings for strength-preserving of glass bottles(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Mennig, Martin; Gier, Andreas; Anschütz, Dieter; Schmidt, HelmutAn amino-epoxy-silane based coating system (GAMAL) for glass surfaces was developed, which can efficiently protect bottles from the damages of a bottling plant. Testing bottles with a ramp pressure tester show an identical value of about (40 ± 4) bar for conventionally hot- and cold-end coated bottles and bottles coated with the developed organic-inorganic composite (GAMAL) system. After already 2 min of wet line-simulation testing, all species of a conventionally coated probe fall short of the critical limit of 16 bar, whereas bottles coated with GAMAL (thickness about 7 µm) show a value of (21 ± 3) bar. Coating is possible by dip and spray applicadon on cold or hot (80 °C) substrates, the coating is cured at 120 °C for 5 to 10 min. Additional functions such as colour or UV protection can be added easily, without reduction of the protection potential. The low content of carbon (about 0.5 g per 1 l soft drink bottle) should not disturb the recycling process of such coated bottles.
- ItemMicrowave-assisted digestion of ceramic frits for boron and lithium determination by inductively coupled plasma spectrometry (ICP-OES)(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Barba, Antonio; Gazulla, M. Fernanda; Gómez, M. Pilar; Jarque, Juan Carlos; Mestre, SergioBoron and lithium are two elements commonly found in the chemical composition of ceramic frits. They are usually determined by volumetric titration and atomic absorption spectrometry, respectively, after melting the ceramic frit by high-temperature alkaline fusion and dissolving the melt in acid medium. This dissolution procedure is long and tedious, and does not enable determining both elements simultaneously. An alternative ceramic frit dissolution procedure based on microwave-assisted digestion in acid medium has been proposed, which allows jointly determining boron and lithium by inductively coupled plasma-optical emission spectrometry. This procedure is rapid and reproducible, and the results are independent of frit chemical composition.
- ItemMatrix algebra method for deriving oxide factors and its relationship to the principle of least squares(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Rawson, HaroldMultiple regression analysis of glass property-composition data involves the derivadon of 'normal equations', one for each oxide factor. The number of these is, in general, much smaller than the number of initial equations, which, for each composition, relate the property to the glass composition. The normal equations are readily derived by a matrix multiplication process. It is shown, by the use of a simple numerical example, that the method minimizes the sum of squares of the residuals in the initial set of equations. The method is used to derive oxide factors for calculating thermal expansion coefficients of glasses in a number of systems. Good agreement between calculated and measured expansion coefficients was obtained, the best being for a large group of alkaline earth aluminoborosilicate glasses, data for which is given in a recent patent. For oxides of both group I and group II elements, there is a linear dependence of the oxide factor on z/a, where z is the valency and a is the cation-oxygen distance. The method and results are compared with earlier work.
- ItemRedox equilibria of polyvalent elements in binary Na2O · xSiO2 melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Gönna, Gordon von der; Rüssel, ChristianGlass melts with the basic compositions (in mol%) of 15 Na2O ∙ 85 SiO2 and Na2O ∙ 2 SiO2 were doped with oxides of various polyvalent elements. At temperatures in the range of 800 to 1550°C, square-wave voltammograms were recorded, which exhibit distinct maxima attributed to respective reduction processes. The following redox steps were observed: Sb5+/Sb3+, Sb3+/Sb0, As5+/As3+, As3+/As0, Cu+/Cu0, V5+/V4+, V4+/V3+, Cr6+/Cr3+, Cr3+/Cr2+, Fe3+/Fe2+ and Ti4+/Ti3+. Peak potentials measured in the Na2O ∙ 2 SiO2 glass depended linearly on temperature, while those of the 15 Na2O ∙ 85 SiO2 melt were affected by the crystallization of cristobalit at temperatures < 1300°C. Redox equilibria in the alkali-rich Na2O ∙ 2 SiO2 melt were generally shifted to the oxidized state by comparison to those measured in the 15 Na2O ∙ 85 SiO2 melt.
- ItemChemical indexes and in-vitro solubility(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Meringo, Alain de; Lafon, Fabrice; Furtak, Hans; Hanton, DanielDifferent chemical indexes have been proposed in the literature, in order to predict the influence of the chemical composition of mineral fibers on their properties. One of these properties is the acellular in-vitro dissoludon behavior (noted thereafter: solubility) in synthetic lung fluids at pH 7.4, which has been shown to be a reliable predictor of the results of expensive chronic long-term in-vivo tests conducted up to now with fibers [1 and 2]. This in-vitro solubility has been reported as being a function of the chemical composition [3 and 4]. The aim of this investigation was to assess if the in-vitro solubility could easily be predicted through conventional chemical indexes already reported in the literature; such as the following: - nonbridging oxygen (NBO) as calculated by Moore and Brown [5]; - optical basicity (OB) as defined by Baucke and Duffy [6]; - free enthalpy (ΔG°) of hydration as evaluated from tables in Paul [7]; - "Kanzerogenitätsindex" (KI) as defined in [8]. The relationship between the acellular in-vitro solubility expressed as KDISSiO2 or KDISCaO and these four different indexes has been analyzed. Nene of these indexes could be reliably used to prediet the in-vitro solubility at pH 7.4 for a broad range of composidons. KI is an acceptable indicator of in-vivo biopersistence [9], in a narrow range (15 to 40). It is the best of all the analyzed indexes giving a general trend for the solubility. The calculated correlation coefficient between KI and KDISSiO2 is then 0.78. This work shows that calculated indexes derived from the literature are not sufficient to prediet the results of in-vitro dissolution tests; and thus the need for a reliable standardized in-vitro test method is emphasized.