Search Results

Now showing 1 - 10 of 644
  • Item
    Significance of redox reactions in glass refining processes
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Yoshikawa, Hidemi; Kawase, Yoshinori
    The role of the redox reactions due to refining agents in the glass refining processes was examined. Α new approximate model for shrinkage (or growth) of gas bubbles in glassmelts in which redox reactions caused by refining agents were taken into account was developed. The proposed model is a modification of the quasi-stationary model by which the redox reactions due to refining agents can not be considered. It was found that the shrinkage (or growth) of gas bubbles in melts with refining agents is quite faster than that in those without refining agents. Numerical results for single-component and multicomponent gas bubbles indicate that the mechanism of the bubble shrinkage (or growth) in the refining process is significantly controlled by the oxidation of refining agents, which decreases (or increases) the oxygen concentration in the glassmelt and as a result causes the rapid oxygen transfer across the bubble/glassmelt Interface and hence the fast shrinkage (or growth) of the gas bubble. The applicability of the proposed model was examined using the computational results and experimental measurements in the literature. It was also found that the proposed model provides better predictions compared with the quasi-stationary model.
  • Item
    Optical, electrical and chemical properties of PEO:I2 complex composite films
    (Heidelberg [u.a.] : Springer, 2022) Telfah, Ahmad; Al-Bataineh, Qais M.; Tolstik, Elen; Ahmad, Ahmad A.; Alsaad, Ahmad M.; Ababneh, Riad; Tavares, Carlos J.; Hergenröder, Roland
    Synthesized PEO:I2 complex composite films with different I2 concentrations were deposited onto fused silica substrates using a dip-coating method. Incorporation of PEO films with I2 increases the electrical conductivity of the composite, reaching a maximum of 46 mS/cm for 7 wt% I2. The optical and optoelectronic properties of the complex composite films were studied using the transmittance and reflectance spectra in the UV-Vis region. The transmittance of PEO decreases with increasing I2 content. From this study, the optical bandgap energy decreases from 4.42 to 3.28 eV as I2 content increases from 0 to 7 wt%. In addition, the refractive index for PEO films are in the range of 1.66 and 2.00.1H NMR spectra of pure PEO film shows two major peaks at 3.224 ppm and 1.038 ppm, with different widths assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase, respectively. By adding I2 to the PEO, both peaks (amorphous and crystal) are shifted to lower NMR frequencies indicating that I2 is acting as a Lewis acid, and PEO is acting as Lewis base. Hence, molecular iodine reacts favorably with PEO molecules through a charge transfer mechanism, and the formation of triiodide (I3-), the iodite (IO2-) anion, I 2· · · PEO and I2+···PEO complexes. PEO:I2 complex composite films are expected to be suitable for optical, electrical, and optoelectronic applications.
  • Item
    Advanced batch house technology for float glass - the new plant of SAINT-GOBAIN GLASS DEUTSCHLAND in Cologne/Porz
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Drescher, Holger
    [no abstract available]
  • Item
    Evaporation of fluorine, chlorine and selenium from glass melts and emission reducing measures
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Kirchner, Ulrich
    The simultaneous waste gas treatment of inorganic gaseous fluorine and chlorine Compounds as well as of gaseous selenium Compounds is still a big problem for many companies of the German glass industry. With the aid of an HVG/AiF research project investigations were carried out with the aim of characterizing the evaporation behaviour of fluorine, chlorine and selenium from industrially melted soda-lime-silica glasses (container glasses) and of correlating their behaviour with the operating data of the melting furnaces. The main effort, however, was put into investigating the absorption rates on an existing waste gas treatment plant depending on the kind and the quantity of the absorption agent. Moreover, the influence of the absorption temperature on the absorption rates was determined.
  • Item
    Estimation of liquidus temperatures in silicate glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Karlsson, Kaj H.; Backman, Rainer; Cable, Michael; Peelen, Jan; Hermans, Jan
    Two models for estimating liquidus temperature from composition are presented and compared with thermodynamically calculated temperature as well as primary phase. Α simple polynomial model is given for high silica glasses, while a model covering a wide composition range and several primary phase fields is more complex. Thermodynamic calculations generally give too high liquidus temperatures in the devitrite field and too low in the primary field for Na2O · 2 CaO · 3 SiO2. In the wollastonite field the values are scattered, but in general too high.
  • Item
    UV light induced photoreduction in phosphate and fluoridephosphate glasses doped with Ni2+, Ta5+, Pb2+, and Ag+ compounds
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Möncke, Doris; Ehrt, Doris
    The photoreduction of polyvalent ions was studied in high purity fluoride-phosphate and metaphosphate glasses doped with Ni2+ (3d8), Ta5+ (5d0), Pb2+ (6d2), and Ag+ (3d10). Compared to the undoped base glasses all doped samples display different electronic transitions in the UV at the irradiation wavelength. Glass samples containing 50 to 5000 ppm dopants were irradiated with excimer lasers at 193 and 248 nm, respectively. The subsequent defect centers, formed at ppm levels, were characterized by EPR and optical UV-VIS spectroscopy. The observed laser induced transmission losses in the UV and visible range increased in the order Ni, Ta, Pb to Ag. Extrinsic electron centers are formed by photoreduction of the dopants. (Ni2+)- is characterized by an optical transition with a maximum at 355 nm and an EPR signal around g ≈ 2.07. The maxima of the optical transitions of the (Pb2+)- -EC are positioned at 395 and 500 nm, of the (Ta5+)- -EC at 465 nm. The photoionization products of silver depend strongly on the silver concentration. At a silver content of 50 ppm only the (Ag+)- -EC is formed, visible in the optical spectra with a maximum around 450 nm. Α second silver species, (Ag+)2 -, which absorbs at 305 nm, is additionally observed in the sample doped with a silver concentration of 500 ppm. In the sample doped with 5000 ppm silver a third defect, the photooxidized (Ag+)+ -HC, with an optical band maximum at 405 nm and an EPR signal around g ≈ 2.3 is observed as well. The formation of extrinsic electron centers causes in all glasses an increase in the formation of intrinsic hole centers and often a decrease in the formation of intrinsic electron centers. Defect generation curves show that a very rapid darkening in the glasses is initiated by the addition of any of these dopants. The recovery rates of the defeets formed depend strongly on the dopant, not on the glass matrix.
  • Item
    Weathering of tin oxide coated glass with low IR emissivity
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Rädlein, Edda; Buksak, Anna; Heide, Gerhard; Gläser, Hans Joachim; Frischat, Günther Heinz
    The weathering of K-glass has been studied by measuring transmission and reflection in the visible (VIS), near infrared (NIR) and infrared (IR) wavelength ranges, by chemical depth profiling with secondary neutral mass spectrometry (SNMS) and by atomic force microscopy (AFM) imaging. K-glass is a commercial tin oxide coated glass with low IR emissivity. The SnO2:F-coated side has been exposed to atmospheric conditions for up to 32 weeks and for up to two years. It could be shown that the optical properties are only affected in the VIS range, but the visible contamination does not influence the high IR reflection. This means that the heat-insulating properties of window glazings with the K-glass coating on the surface do not degrade under atmospheric conditions. Chemical depth profiles did not reveal major changes, except for an increase in the signals of minor elements on the surface, namely sodium, carbon and silicon. AFM showed that after 32 weeks the deep valleys of the rather rough crystalline SnO2:F are partially filled up. The high transmission of new K-glass can be regained since contamination or corrosion products can be removed by washing. The coating itself is chemically stable.
  • Item
    Influence of homologous substitutions of chemical components on the rheological properties and on isochomal workability of Silicate glass melts
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Yue, Yuanzheng; Brückner, Rolf
    Glass melts of various homologous Silicate glass series were investigated by means of the cylinder compression method with respect to their flow behaviour (Newtonian and non-Newtonian), stress generadon modulus (stiffness, brittleness) and critical deformadon rate (high-temperature tensile strength, isochomal workability). The experimental results show that decreasing CaO content and increasing basicity lead to the decrease of the brittleness of Silicate glass melts and to the increase of the critical deformadon rate, i.e. to the improvement of the isochomal workability of these melts. The mixed alkali effect of sodium potassium calcium Silicate glass melts at molar fracdon [K₂O]/[Na₂O+K₂O] = 0.5 has a favourable influence on the isochomal workability The correladon between flow behaviour and workability of glass melts is also discussed in the present paper. It could be shown that the ratio β = E2.8/E3.6 (E is the extinction of the hydroxyl band at 2.8 and 3.6 ηm, respectively) indicates the structural origin of the dependence of the mentioned rheological properties on the chemical compositions, at least within the homologous series.
  • Item
    Method for determining in-vitro dissolution rates of man-made vitreous fibres
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Guldberg, Marianne; Christensen, Vermund R.; Krøis, Winni; Sebastian, Klaus
    A "state-of-the-art" method for determining the in-vitro dissolution rate of man-made vitreous fibres (MMVF) is described. The dissolution rate is determined using an artificial lung fluid, adjusted to pH values of 7.5 or of 4.5, reflecting that the dissolution in vivo takes place both in the near-neutral lung fluid and in the acidic environment of the macrophages. The method is based on flow-through equipment and prescribes well-defined conditions using a ratio of the flow rate to surface area of 0.03 µm/s. The results obtained with this method correlate to results from in-vivo tests, and thus the method provides a tool for a comparative evaluation of the biodurability of different fibre types. The described method seems suitable to be estabhshed as a provisional standard test, until further investigations allow the definition of a final standard test. The empirically derived carcinogenicity index (KI) extrapolates the in-vitro results obtained for some fibre types at the neutral pH value to other very different fibre types. The proposed in-vitro method avoids these uncertain generalizations, as it is based on actually measured dissolution rates at pH values 7.5 and 4.5, respectively.
  • Item
    Bioactive coatings of glass-ceramics on metals
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Jana, Carsten; Wange, Peter; Grimm, Gabriele; Götz, Wolfgang; Nisch, Wilfried
    To combine the mechanical properties of high-strength base metals with the biological properties of bioactive materials, coatings of BIOVERIT® glasses and glass-ceramics on CoCr alloys and titanium have been produced. Different kinds of coating processes have been used: dipping, sputtering, plasma spraying, sintering and pasting. Dipping and pasting seem not to be suitable to produce layers because of cracks and low adhesion strength of the coatings (dipping) and the limitations in relation to the implant shape and the thickness of the layers (pasting). Using sputter techniques it is possible to produce dense layers ( < 10µim) with a high adhesion strength. Plasma spraying resuhed in layers with a thickness of 50 to 300µim, but during the plasma spraying process there is a partial evaporation of the highly volatile glass components. Sintering processes are very suitable to produce layers with a high adhesion strength; these layers are long term stable in simulated body fluid.