Glastechnische Berichte : Zeitschrift für Glaskunde
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- ItemInfluence of the grain size of glass frits on the characteristics of glass enamels(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Paulus, Hildegard; Müller, Siglinde; Oel, Heribert J.Glass enamels, like porcelain decals, consist of a pigment in a glass flux (frit), but must be capable of being fired-on at low temperatures. Susceptibility to chemical attack and a reduction in the mechanical strength of the enamelled body are two disadvantages of enamels. An attempt to improve these properties by altering the fineness to which the glass frit is ground is described in this paper. Several glass frits were used, each ground to three different grades. The effect on colour, lustre, dishwasher durability and mechanical strength was investigated.
- ItemHigh-temperature IR spectra of nioboborate glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Quanzu, Yang; Zhongcai, Wang; Shizhuo, Wang; Donghui, LuThe structure of nioboborate glass melts in the system Nb2O5—B2O3—K2O has been studied for the first time by high-temperature IR spectra. The structure models of the glass melts and the glasses have been established.
- ItemModelling of chemical and morphological changes of silicate fibres used in a Portland cement matrix(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Wojnárovits, Ilona; Fodor, MártaBasalt and glass wool materials were continuously eluated in saturated lime water and in 10^3 mol NaOH/m3 at 70 °C. The alkali resistance of fibres was investigated, in particular its dependence on the chemical composition of the fibres and on the nature of the reaction products formed on the fibre surface. For this purpose wet chemical and x-ray diffraction analysis, as well as scanning electron microscope and microprobe were employed. The higher alkali resistance of basalt fibres against both corrosive agents can be explained by their higher MgO and Fe2O3 as well as lower Na2 and K2O contents.
- ItemTransient ionic conductivity in fused silica(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Varshneya, Arun K.; Jain, Vijay; Bihuniak, Peter P.Transient currents in doped and commercial type-I fused silica glasses were monitored by electrolyzing alkali ions (Na+ , Li+ and K+) through a sample disk in a U-tube dc non-blocking conductivity cell until steady state was achieved. The experiments were carried out either at 600 or 650 °C. Approach to steady state varied from sample to sample depending not only on the electrolyzing ion but also on the alumina/alkali ratio and the concentration of Li+ and Na+ impurity level in the silica. Results indicated that the transient behavior (current versus time) at a particular temperature was best expressed as a lg — lg plot showing two linear regions. The initial slope was attributed to the flushing of more mobile species and the final slope to the disappearance of interdiffusional coupling effects. The nature of the interdiffusional coupling, in some cases, was typical of the mixed-alkali effect in silicate glasses containing much higher levels of mixed alkali.
- ItemGreat son of a great father - On the occasion of the 100th birthday of Erich Schott(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Steiner, JürgenErich Schott was born 100 years ago, on March 29, 1891. He was the son of Otto Schott, the pioneer of modern glass technology, who had founded in 1884 in Jena, together with Ernst Abbe, Carl and Roderich Zeiss, the later-to-be Jenaer Glaswerk Schott & Gen. Erich Schott grew from early on into the tradition of glass making and, in 1927, he succeeded his father in the glassworks. For more than half a century, he controlled decisively the fortunes of the company in eventful times [1 to 4]. After World War II and the loss of the factory in Jena, Erich Schott conducted the "trek of the 41 glass makers" to the western part of Germany. The crowning event of his life's work was the reconstruction of the present Schott Glaswerke in Mainz. He laid the foundations for the development of the company into Europe's leading special-glass manufacturer. The stock of ideas of the Carl-Zeiss-Stiftung has always been the guideline of his scientific, entrepreneurial and social activities. In 1956, he was awarded the Otto-Schott-Denkmünze by the Deutsche Glastechnische Gesellschaft that, in 1971, elected Erich Schott its honorary member.
- ItemTitanium nitride-based Iow-emissive coatings — A stability comparison(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Georgson, Mikael; Roos, Arne; Ribbing, Carl G.Accelerated degradation tests with respect to high temperature and acid exposure have been performed with laboratory samples of TiO2 / TiN / TiO2 transparent low-emissive coatings. The same tests have also been performed with noble metal-based low-emissive coatings presently marketed for energy conservation and solar control. The comparison clearly demonstrates the improvement in stability which is obtained when the soft, diffusive noble metal is replaced with a hard, high temperature stable transition metal compound. Using optical multilayer calculations to simulate the effects of high temperature degradation, clear differences between the degradation mechanisms were identified: The TiN multilayer degrades by successive oxidation while the silver multilayer degrades by diffusion and agglomeration of the entire silver film.
- ItemGlass bowls made on the potter's wheel A new approach to ancient glass technology(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Lierke, RosemarieEarly glass vessels were made by winding a glass thread onto a core which was fixed to a metal rod. This core-forming technique could not be used for the manufacturing of bowls, but a related procedure seems to have been employed. The investigation of spirally wound reticella bowls (3rd century BC to first half 1st century AD) has shown that they probably were made by spinning a reticella thread onto a mold on a potter's wheel. This manufacturing technique was experimentally reproduced. It is a fast and easy method, permitting a continuous production. No finishing by grinding or polishing is required. It is possible that certain other types of glass bowls, today claimed to be "cast and lathe cut" or "molded", have actually also been made on the potter's wheel. This is especially true for the so-called ribbed bowls.
- ItemElectrochemical measurement of oxygen activity in lead glass by means of a stabilized ZrO2 sensor Part 2. Determination of the equilibrium constants in the redox systems arsenic and antimony(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Lafroukhi, Omar; Hertz, Jean; Hilger, Jean-Pierre; Cornier, GérardThe influence of the redox systems Sb3+/Sb5+ and As3+/As5+ on the lead glass refining is shown. This is achieved through the determination of the equilibrium constant, K, and the thermodynamic standard quantities, ΔG^0, ΔH^0, ΔS^0, by means of chemical analysis as well as electrochemical measurement. A discussion of the results yields the thermodynamic standard quantity ΔH^0 as determined by electrochemical measurement and the transition temperature, T, as determined by chemical analysis, in turn resulting in ΔS^0 = ΔH^0/T. For the redox system As2O3/As2O5 the following thermodynamic standard quantities are determined: ΔH^0 = - 193 kJ/mol, ΔS^0 = - 112 J/(mol K) with T = 1725 K. The respective quantities for the system Sb2O3/Sb2O5 are: ΔH^0 = - 325 kJ/mol, ΔS^0 = - 226 J/(mol K) with T = 1435 K.
- ItemInfluence of heat treatment on the crystallization process during melting and drawing of continuous basalt fibres(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Lyubtchev, Lyubtcho; Liptchev, Zhivko; Davarska, Ginka[no abstract available]
- ItemSodium/silver ion exchange between a non-bridging oxygen-free boroaluminosilicate glass and nitrate melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Kaps, Christian; Fliegel, WolframA sodium boroaluminosilicate glass, in which no non-bridging oxygen could be detected, is contacted with AgNO3—NaNO3 melts at 375 °C. A diffusion-controlled Na+/Ag+ exchange has been observed in the bulk of the glass up to a degree of exchange of 70 % (Fickian behaviour). For a higher degree of exchange network-structure relaxation processes appear as a result of the viscosity-lowering effect of silver, causing a change of the diffusion conditions during the ion exchange in the glass (non-Fickian behaviour) . The time-independent equilibrium concentrations at the glass surface refer to a remarkable affinity of the glass for the highly polarisable Ag+ cations (degree of exchange: 98 %). This result can be explained by coordinative binding of silver on the basic bridging oxygen of the AlO4/2 tetrahedrons into the glass network.
- ItemEmission limits of air pollution and their legal background for the glass industry in the 18 EC and EFTA countries with reference to the values in Japan and the USA(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Gutersohn, HeinrichEmission limits for air pollution in the 18 EC and EFTA countries still vary strongly; in fact in most of them even today there is still no legislation at all. But the trend is — with variations — to follow the German "TA Luft" legislation. By contrast emission limits in Japan and the USA in some areas are even stricter than those of the "TA Luft". The paper shows the state of the national legislations at the end of November 1989. These data are still up-to-date with the exception of those of Italy and England which made first steps towards the "TA Luft" legislation in the meantime. A comparison of emission limits is added explaining why EC legislation lags behind national legislations.
- ItemEffect of glass composition on the spectral and other properties of neodymium-doped borophosphate glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Jiang, Shibin; Jiang, YasiLaser glasses of the system R2O(MO)—P2O5—B2O3—Ln2O3 (R = Li, Na, K; M = Ca, Sr, Ba; Ln2O3 = La2O3 + Nd2O3) at high Nd3+ concentrations of 1 ∙ 10^21 ions/cm3 were prepared. By using reactive atmosphere processing to remove hydroxyl groups, the infrared absorption coefficient at 3.5 μm due to OH- groups was below 1 cm^-1 . Absorption and fluorescence spectra, fluorescence lifetimes and thermal expansion coefficients were measured, and the stimulated emission cross-section for the 4F3/2 — 4I11/2 transition and the quantum efficiency were calculated. The results indicate that the borophosphate glass is possessed of a large stimulated emission cross-section, especially for alkali oxide containing borophosphate glass systems in which the stimulated emission cross-section is larger than 4.4 ∙ 10^-20 cm2 , and the effect of alkali and alkaline earth ions depends on the bonding strength between the cation and oxygen. The influence of B2O3 in borophosphate glasses on the fluorescence lifetime is much less than that in silicate glasses, and the quantum efficiency of borophosphate glasses, different from borate and borosilicate glasses, is high. The introduction of B2O3 strengthens the structure resulting in a lower thermal expansion coefficient and an excellent thermal shock resistance.
- ItemOn the polishing of glass, particularly the precision polishing of optical surfaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Kaller, AdolfIn this survey, the views on the mechanism of the polishing of glass to be found in the literature are only dealt with briefly, because extensive summarizing evaluations of reports dealing with the problem are available. The main objective of this paper is the investigation of the causes of hitherto differing views on the processes occurring during the polishing of glass, despite the extensive literature which exists in over 500 publications. The causes for the differing interpretations of the polishing mechanisms result from an incorrect evaluation of the properties of the polishing compounds and of the polishing parameters during precision polishing. Therefrom and from the author's long-term investigations of the properties of model polishing compounds and of the polishing processes with these model polishing compounds under optical production conditions a generally valid theory of the polishing of optical media was developed. This idea — named "tribochemical friction-wear polishing theory" — is totally different from hypotheses presented up to now. The present paper tries to verify the correctness of the new theory.
- ItemProton-induced X-ray emission analysis of early Finnish "Waldglas"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Kuisma-Kursula, Pirkko; Räisänen, Jyrki; Spring, Erik; Matiskainen, HeikkiThe proton-induced X-ray emission method was used to determine the minor and trace elements in glassware originating from early Finnish glassworks. The material analysed consisted of glassworks stamps originating from green bottles as well as pieces of hand-blown window glass cylinders. Several glass standards from the National Bureau of Standards (USA) were used to obtain the absolute concentrations of calcium, titanium, manganese, iron, copper, zinc, lead, arsenic, rubidium, strontium, zirconium and barium. Because the glassworks in the 1600's and 1700's used local raw materials, the possibility of identifying the manufacturer of the glass items by determining their element composition was investigated. It is shown that even if variations in absolute concentrations are not significant, proton-induced X-ray emission data followed by multivariate statistical analysis is a helpful approach for identifying the manufacturer of the earliest Finnish glass items.
- ItemConstruction of an experimental unit for the mechanical colour sorting of non-crushed recycled container glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Gitzhofer, Karl-HeinzThe continuous growth of container glass recycling requires additional measures for the colour separation of waste glass. This paper presents the results of a research programme partly financed by the Umweltbundesamt (Federal Office for the Environment), Berlin, which deals with the mechanical colour separation of recycled container glass. It was the task of this research programme to develop and build a pilot unit which would function under operational conditions. For economic reasons and in order to limit the technological input, the process is designed for the sorting of whole bottles and large pieces of cullet. Before starting colour sorting, small pieces of glass are screened off. The larger material is aligned in the conveyor direction and is fed in single file to the colour recognition and ejector systems. After colour recognition by a light transmission measurement, the bottles or glass pieces are separated according to colour, in free fall, by mechanical ejection of the samples. The colours flint, amber, green and opaque are differentiated.
- ItemContribution to basicity of technical glass melts in relation to redox equilibria and gas solubilities(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Krämer, Fritz W.To use the gas solubilities reported in the literature for binary or ternary silicate or borate melts to predict values for industrial glass melts, a basicity number concept was developed. Acidic values derived by cation-oxygen bond strengths multiplied by the mole fractions of the glass oxides were used to form a scale of basicity numbers for glass melts. The origin of this scale is the basicity number of boron oxide. This basicity number concept was successfully applied to gas solubility values for H2O, CO2, and SO2 in binary and ternary glass melts and to the solubility of oxygen in glass melts with multivalent ions, such as iron, arsenic, antimony, cerium, chromium and manganese.
- ItemMicrostructural development of a P2O5-modified cordierite glass ceramic during sintering Part 2. Densification experiments(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Rudolph, Thomas; Weisskopf, Karl-L.; Pannhorst, Wolfgang; Petzow, GünterThe non-isothermal sintering of a P2O5-modified cordierite glass powder was investigated using sintering dilatometry, DTA and x-ray diffractometry. A typical densification curve as obtained by dilatometry with a constant heating rate is discussed. To clarify the dependence of the final degree of porosity on the heating rate additional porosity measurements were carried out on selected specimens using a stereological image processing system. The porosity exhibits a distinct minimum for a heating rate of 15 K/min. This effect is discussed based on a variation of the effective sintering interval which ranges from Tg of the glass to the onset temperature of crystallization. Together with the crystallization behaviour, as given in part 1 of this paper, a schematic description of the microstructural development is presented.
- ItemSensor for oxygen activity measurements in glass melts(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Müller-Simon, Hayo; Mergler, Kurt W.Traditional oxygen activity measurement in glass melts is based on Y2O3-stabilized ZrO2 which, in continuous use in the glassworks, is subjected to considerable wear. The present paper describes an oxygen sensor that is not equipped with wear parts. The new sensor is far less sensitive to temperature gradients in the surrounding area than ZrO2 sensors; the oxygen measurement, however, is greatly disturbed at direct flame irradiation.
- ItemElectrochemical measurement of oxygen activity in Iead glass by means of a stabilized ZrO2 sensor Part 1. Qualitative aspect(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) El Harfoui, Mohammed; Hilger, Jean-PierreA zirconia-based electrochemical cell has been developed to measure the oxygen potential in glass with respect to the following parameters: time, temperature, composition of the glass and the nature of the redox system. After melting the raw materials, the glass is very oxidized and the electromotive force grows up to a maximum before diminishing to a level of equilibrium with the surrounding atmosphere. Two opposing kinetically different systems exist: the appearance of oxygen through shifting of the redox equilibrium to the reduced state, and the disappearance of oxygen so as to come back to equilibrium with the surrounding atmosphere. The amplitude of the electromotive force variation with the temperature is based on the constitution of the glass as well as of the redox system.
- ItemUltrasonic investigation of the structure of heat-treated bentonite glass fibers(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1991) Gogov, DimiterUltrasonic techniques were used to monitor the structural changes that occur in leachable bentonite glass fibers as a result of specially selected thermal treatments. Values of the parameters time, velocity of propagation of ultrasonic waves, and the Young's modulus were determined for fibers that had been subjected to various temperatures (300 to 500 °C) and to various treatment times (1, 3, 5, 7, and 24 h) . It was found that ultrasonic echoscopy offers an effective means for monitoring the structure of leachable bentonite glass fibers. Depending on the desired goal, the ultrasonic echoscopy techniques make it possible to select optimum heat treatments that will lead to the formation of porous structures (adsorbents and catalyst carriers) with specified properties.