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- ItemCalculations on the dimensioning of plunger cell and feeder head(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Reeßing, Friedrich; Schötz, Eberhard[no abstract available]
- ItemTime resolved fluorescence measurements on Tb3+ and Mn2+ doped glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Herrmann, Andreas; Ehrt, DorisTb3+ (4f8) and Mn2+ (3d5) ions, known as active luminescent centres for blue, green and red fluorescence, were doped in various fluoride, phosphate and Silicate glasses with well known structure. Narrow bands of f-f transitions with strong emission of Tb3+ in the blue, green and red and broad bands of d-d transitions of Mn2+ were measured with green emission in high optical basicity glasses with tetrahedrally coordinated Mn2+. Orange to red Mn2+ emission was found in glasses with low optical basicity where Mn2+ is octahedrally coordinated. Lifetimes, τe, in the range of milliseconds were recorded in dependence of glass composition and dopant concentration for both Tb3+ and Mn2+ doped glasses. Fluorescence lifetimes are as well shortened by higher basicity of the glasses as by increasing dopant concentration.
- ItemPreparation and properties of model glasses of historic enamels of the Green Vault Museum, Dresden(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wagner, Marcel; Frischat, Günther Heinz; Hellmold, PeterMany enamelled art objects of the Green Vauk Museum, Dresden, have been suffering a severe deterioration of the enamel layers during the last 20 to 30 years. The authors obtained three splinters of about 200 mg weight each of green, blue, and opaque turquoise enamel of the Aurangzeb ensemble. Model glasses of these originals were prepared which should match them as closely as possible. The investigations showed that the simple degree of network polymerization related to the SiO2/Na2O ratio is insufficient to understand their chemical properties even if one takes components such as MgO, CaO or AI2O3 also into consideration. To understand further structural influences IR, UV/VIS, and EPR spectroscopy studies were performed on the enamels, and it could be evidenced that components such as MnO, Fe2O3, CuO, CoO, PbO and SnO2 not only act as colorants or opacifiers but also as stabilizers of these materials. Taking this into account the chemical and physical behavior of the respective enamels in the museum can be elucidated.
- ItemSilicon in container glasses, its solution kinetics and dissolving potential in container glass furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Pitzel, Christian; Stachel, Dörte; Ehrig, ReinerThe forming proeess of sihcon stones in differently colored container glasses under the action of different aluminum pieces will be discussed and some special features during the generation reported. The dissolution of formed silicon stones was analyzed in dependence on melting time, temperature and color of the glass. With the knowledge of these parameters the rate constant and the diffusion coefficient of the dissoludon were calculated. The main results are: first, it is not possible to generate large silicon stones anyway, indicated by big aluminum pieces which will be divided when they become liquid. Second, the dissolving of the silicon stones does not go on homogenously about the whole temperature range analyzed. But it can be divided into three fields: an area below, an area around and an area above the melting point of the silicon. The reason for these differences is found in the SiO2-rich layer around the stones which will be formed and dissolved by different rates in colored container glasses. On the basis of these dissolving rates and of the temperature profiles in glass meldng furnaces the dissolving potential in furnaces could be calculated. Three possible routes of silicon stones through special types of furnaces show the respective dissolving potential for silicon. The potential for dissolution of elementary Silicon for the calculated types of Container glass furnaces is nearly the same. The dissolution rates could be improved by raising the temperature of the glass bath in the furnace and by raising the dwell time of the silicon stones in the furnace.
- ItemInfluence of glass/mould interfaces on sticking(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Pech, Jérôme; Berthomé, Gregory; Jeymond, Michel; Eustathopoulos, NicolasThe sticking of glass on mould materials is a critical problem since it can lead to the Interruption of glass Container production. This study is a contribution to understanding the phenomena at the origin of sticking. The experiments involve loading and spreading glass gobs on flat metallic Substrates. They are performed directly on a glassmaking machine, thus the thermal conditions of the processes are simulated as closely as possible. Special attention is paid to characterizing the metal and glass surfaces before and after contact using a surface profilometer, AFM, and SEM with an EDX spectrometer. The influence on sticking of mould temperature, surface roughness and surface chemistry (nonoxidized, pre-oxidized and lubricated) is investigated.
- ItemEvolution of the compositions of commercial glasses 1830 to 1990. Part II. Container glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Smrček, AntonínThis paper treats container glasses in the same way as an earlier paper reviewed flat glass compositions. Data for more than 970 analyses of container glasses manufactured during 150 years in 37 countries have been collected and analysed. The data obviously include containers made by hand as well as by machine from green, white and amber glasses. Compositions developed along two lines, one being green and brown glasses coloured by manganese; such glasses were characterized by low alkali content compensated by increased RO and higher AI2O3 contents. The other, younger, line includes white glasses historically descended from old "forest glasses" and closely related amber glasses. The compositions of both lines converged gradually, so that from about 1970 all container glasses have fallen within a narrow range of compositions, differing in little but their colouring oxides. Differences between particular producers and countries have decreased a great deal.
- ItemEffect of some nucleating agents on thermal expansion behaviour of Li2O-BaO-Al2O3-SiO2 glasses and glass-ceramics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Khater, Gamal A.; Idris, Maher H.The thermal expansion behaviour of some glasses and glass-ceramics within the system spodumence (LiAlSi2O6)-celsian (BaAl2Si2O8) containing LiF, TiO2 and Cr2O3 as nucleation catalysts was described. LiF and TiO2 were found to increase the thermal expansion of the glasses investigated, whereas Cr2O3 slightly lowered the expansion coefficient. The dilatometric transition and softening points of the glasses showed the reverse behaviour. The thermal expansion of the glass-ceramics was a function of type and amount of nucleating agent and heat treatment which greatly affected the mineralogical constitution of the materials.
- ItemLong-range granular feature of silicate glasses and its relation to glass properties(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wang, ChunNumerous experimental results show that silica and silicate glasses consist of higher density granules about 20 to 50 nm sized and lower density linkages. Such long-range feature should originate from the long-range density fluctuation of the glass-forming liquid. Due to the highly coordinated network structure of glass the lower density regions may be under strain. Following this assumption many phenomena of glass observed here and reported in the literature can be explained well, e.g. anomalous conductivity, brittleness, granular boundary contour of crack, high conductivity on the fracture surface, cloudy damage after dishwashing, corrosion products on glass surface, distribution pattern of Ag colloidal particles in float glass bath side, disproportional large influence of water on glass properties, the unusual increase in expansion coefficient with increasing modifier content, etc.
- ItemMicrostructure formation and surface properties of a rhenanite-type glass-ceramic containing 6.0 wt% P2O5(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Höland, Marlies; Dommann, Alex; Höland, Wolfram; Apel, Elke; Rheinberger, VolkerThe aim of this report was to characterize the microstructure formation of a rhenanite, NaCaPO4, glass-ceramic and to determine its surface properties. The composition of the material was (in wt%) 58.0 SiO2, 6.0 P2O5, 22.8 Na2O, 12.9 CaO, and 0.3 F. Nucleation and crystallization of the monolithic base glass was carried out at temperatures between 650 and 1000°C for one hour. To characterize the different microstructures of the glass-ceramics using scanning electron microscopy (SEM), a special sample with phosphoric acid was prepared. The control of microstructure formation resulted in the precipitation of isolated α-rhenanite crystals with a crystal size of 40 nm up to 1 μm and a crystal number density of 20 to more than 2000 particles per 100 μm2. The α-phase transformed into the β-phase at approximately 690 °C. The surface properties were determined by soaking the specimens in simulated body fluid for up to 10 d. In the process, the glass-ceramics exhibited a high surface activity. Morphological investigations after soaking showed ball-shaped hydroxyapatite-type crystals consisting of two half shells. The authors concluded that rhenanite crystals acted as heterogeneous nuclei for hydroxyapatite on the surface of the bioactive glass-ceramics. Therefore, this material was assumed to have the ability to bond to living bone.
- ItemThree different reasons for surface damages of glasses after machine dishwashing(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Wang, Chun; Krausch, Georg; Decker, Markus; Martinek, Klaus-PeterΑ variety of glass eups has been investigated after treatment in a machine dishwasher. Three types of surface damages were found. The first type consists of clouding on the inner and outer surfaces appearing after about 1000 washing cycles. It can be related to the long range granular structure of glass, which is believed to be formed by thermal density fluctuation. During washing both water and detergents act as weak etchants, first eroding the smooth glass skin, then revealing the granular structure. As soon as the linkages between the granules are entirely broken by the etching, holes will manifest themselves at these sites. When the size of the holes (the hole width) reaches the half of the light wavelength, light scattering occurs and the glass seems cloudy. The second type is the sheet clouding on the outer surface appearing after about 100 washing cycles. It can be related to holes on the surface, which are formed by the loss of the sphere domain phase from the SiO2-rich matrix during washing. These domains result from phase separation induced by round-meldng of the sharp cutting edge, which is responsible for local clouding of glass. The third type is a golden film on the inner surface. These films are probably formed by complex formation between the glass surface and the organic compounds in the drinks. All of the damages studied here are irreversible.