Fachgebiete

Permanent URI for this community

https://oa.tib.eu/renate/handle/123456789/1

Browse

Now showing 1 - 20 of 14309

Short Communication: the Influence of Air-Abrasive Trimming on the Current Noise of Thick Film Resistors
(London [u.a.] : Gordon & Breach, 1984) Wolf, M.
[No abstract available]
On Experimental Data of the Tcr of Tfrs and Their Relation to Theoretical Models of Conduction Mechanism
(London [u.a.] : Gordon & Breach, 1985) Storbeck, I.; Wolf, M.
Any theory of electrical conduction in TFRs encounters mainly two problems: (i) explanation of the dependence of R□ on properties of conducting component (volume fraction, grain size, resistivity), (ii) explanation of the temperature dependence of R□ taking into account (i). In order to achieve this one has to fit some microscopic parameters to experimental R□-and TCR-values, and to check if they are reasonable or not. The aim of the following discussion is to show, that such a fitting by means of experimental TCR-values is not correct. This is due to the fact that TCR-behaviour, as is well known, is determined also by the dependence of resistivity on strain. But any theoretical model neglects strains, also those who are induced by thermal strains. By means of published experiments concerning the strain dependence of resistance, the magnitude is estimated by which the TCR-values have to be corrected for the described fit.
MAGNUS - mehrstufige Analyse grosser Netzwerke und Systeme
(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 1994) Borchardt, Jürgen; Grund, Friedrich; Horn, Dietmar; Uhle, Manfred
[no abstract available]
Glass-ceramics based on phases with NZP-type structure
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Müller, Gerd; Schultz, Sven Gerd; Mildner, Markus
[no abstract available]
Active thermal conductivity of hot glass
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Fotheringham, Ulrich; Lentes, Frank-Thomas
For (semi)transparent glass, it is suggested to distinguish between an active and a passive thermal conductivity. Essentially, the latter is attached to the heat transfer through long-range photons most of which are both emitted and absorbed outside the glass volume, the former to the heat transfer through phonons and short-range photons which have an intense energy exchange with the glass. As the temperature distribution in the glass volume can be influenced only by the heat exchange in which the glass is actively involved, it is determined by the active thermal conductivity. The sum of the active and the passive thermal conductivity, which is identical to the so-called apparent thermal conductivity, indicates the overall heat flux through the glass. Like the apparent thermal conductivity, the active thermal conductivity can be obtained from the prototype of thermal conductivity measurements where the heat flux through a sample between two heat reservoirs of different temperatures is measured. The apparent thermal conductivity follows from the usual reduction o f the measurement data, the active thermal conductivity is derived via a differentation rule. Comparing the calculation and the measurement of the temperature inside a cooling block of glass, this differentiation rule is verified.
Stand des Altglasrecyclings - Verpackungsverordnung und Duales System
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Hoffmann, Werner
[no abstract available]
Polysulfid im Isolierglas-Randverbund - der Umwelt zuliebe
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Lucke, Heinz; Schmidt, Rudolf
[no abstract available]
Anisotropic optical properties and flow behaviour of mechanically deformed single-phase glass melts
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Brückner, Rolf; Habeck, Andreas
Starting from the stress-optical coefficient around and above Tg, the following effects are regarded in order to give a comprehensive picture of the structural response of various glass melts under flow conditions at various temperatures: anisotropy o f glass fibres, the flow birefringence and Maxwell constant of the melt directly and/or indirectly via frozen-in anisotropics by cooling the melt thermally stress-free under mechanical load. Some of the applied various rheological methods allow to study the Newtonian and non-Newtonian viscosity additionally to the birefringence. Four very different glass melts are investigated under these aspects: a potassium-calciumsilicate glass, a float glass, an alkali metasilicate glass and an alkali metaphosphate glass. The results show that there are significant differences in the specific birefringence and in the deviation from Newtonian flow behaviour depending on the special flow units of the glass types. The structure of these anisotropic glasses and melts extends from frozen-in deformations of the network to orientations of chain-like flow units depending on chemical composition, temperature, mechanical stress and deformation rate. Particularly, a close connection between the onset of the non-Newtonian flow behaviour and the alteration o f the specific birefringence was found at certain critical stresses.
Interlaboratory comparison of solar range transmittance and reflectance of coated and uncoated flat glass
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Nicoletti, Fabiano; Polato, Pietro; Roucour, Jean
Transmittance and reflectance measurements on glass for architectural applications using commercial spectrophotometers may be affected by errors resulting from an improperly operated instrument, an inappropriate calibration, etc. Discrepancies between the values of parameters such as light reflectance and solar factor measured on the same glass product by different laboratories can be very pronounced. In order to avoid disputes among glass producers and complaints from glass users the interlaboratory reproducibility and the accuracy of the measurements must be improved. A n intercomparison was organized by Technical Committee 10 "Optical Properties of Glass" of the International Commission on Glass among 15 laboratories and one metrological institute on transmittance and reflectance measurements on commercial coated and uncoated glasses. Good reproducibility and accuracy in transmittance measurements ( ± 0 . 6 %) have been achieved even with each laboratory using its own instrumental procedures. In the case of reflectance, a preliminary round robin performed using the same instruments gave very large discrepancies in the spectral and integrated values. Reproducibility and accuracy of the same order of magnitude as in the transmittance measurements were obtained when each laboratory used a standardized procedure and the same reference standards, the latter having optical characteristics similar to the samples.
Borosilicate glass matrix composites reinforced with short metal fibres
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Boccaccini, Aldo R.; Ondracek, Gerhard; Syhre, Claudia
The reinforcement of a borosihcate glass with Hastelloy X short fibres is discussed. A fabrication process consisting of wet mixing of the glass powder and the metallic fibres and hot pressing of the mixtures was developed. Composites containing 15 vol.% fibres homogeneously distributed in a near fully dense glass matrix were obtained. Both Young's modulus and fracture strength increased with increasing volume fraction of fibres. The experimental values for the Young's modulus are in agreement with theoretical predictions. No fibre pull-out during fracture was detected and there is a good interfacial bond. By means of a rule-of-mixture calculation for the fracture energy, a five-fold increase in fracture toughness for composites containing 15 vol.% fibres can be predicted.
Bewertung von Altglasscherben und Konsequenzen für den Glasschmelzprozeß
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Enneking, Carolus Q. M.
[no abstract available]
Local temperature distribution and primary melt formation in a melting batch heap
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Conrad, Reinhard; Suwannathada, Pichanon; Pimkhaokham, Preeda
The melting behavior of mass glass batches was studied in a gas-fired lab-scale furnace. Batches were adjusted to different redox numbers by additions of sulfate and coal. In each test, 4 kg of batch were charged onto a cullet melt (7 kg, 600 cm² surface area) which was pre-molten at 1200°C. The batch blankets had an initial height of approximately 5 cm. The vertical distribution of temperatures and electrical conductivides were recorded. The occurrence of primary melt was identified by a sudden increase of conductivity by three orders of magnitude. As expected, primary melt occurred latest in the inner zones of the batch. A comparison of conductivities and temperatures, however, showed that primary melt was not formed along any specific isotherm. Thus, the concept of a uniform melting temperature valid for the entire batch heap as used in several theoretical models is not confirmed. Thermal diffusivities derived from a numerical evaluation of the temperature field also displayed a sudden increase, however, at temperatures systematically higher than the temperatures of primary melt formation.
ESR spectroscopy on glasses and glassy-crystalline materials - New opportunities for material scientists
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Stößer, Reinhard; Nofz, Marianne
Analyzing the state of the art of ESR applied to glasses, one can state that all results obtained so far give evidence for the fact that the electron (and nuclear) spin properties are related in a unique manner to the local properties of glassy systems. Therefore, all spin-derived experimental parameters obtained for non-crystalline solids are dispersed around mean values. Suitable theoretical models for an adequate representation of the complex ESR spectra of glasses are reviewed and critically analyzed. The information about the glassy state of matter generated with the help of paramagnetic species offers new opportunities for material sciendsts: criteria for the homogeneity, devitrification and crystallizadon of glasses on a microscopic level; indication of redox processes; localization and function of dopants and their effect on the material properties; evidence for different kinds of internal strain. Some relevant, up to now not commonly used methodical ESR developments like in-situ bending stress experiments, tomography, wide range (4 K ≤ T ≤ 1000 K ) temperature dependence are presented.
Diopside marble-like sintered glass-ceramics
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Karamanov, Alexander; Gutsow, Ivan; Penkov, Ivan; Andreev, Julian; Bogdanov, Bogdan
Experimental results on the synthesis of a new marble-like glass-ceramic material to be used for wall covering are given. The material is prepared by sintering and surface-induced crystallizadon of a precursor frit. In contrast to usual glass-ceramic materials similar to natural marbles and granites, where the major crystalline phase is β-wollastonite (CaO * Si0₂ ) , in the new material diopside (CaO * MgO * 2Si0₂ ) is formed. Due to the enhanced crystallization ability of the initial glasses, the duration of the heat treatment needed for the synthesis of the new materials can be considerably reduced.
Composition of titania coatings deposited by different techniques
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Laube, Michael; Wagner, Wolfgang; Rauch, Friedrich; Ottermann, Clemens; Bange, Klaus; Niederwald, Hansjörg
Quantitative dement concentrations in titania films produced by different deposition techniques (evaporation, sputtering, ion-assisted deposition, ion plating and dip coating) have been determined by means of Rutherford Backscattering Spectrometry and Nuclear Reaction Analysis with the reaction ¹H(¹⁵N, αγ)¹²C. Large differences of the hydrogen content are found for the various production techniques and the related deposition parameters, which correlate with the refractive index of the respective film. In dependence on the deposition conditions the oxygen/titanium ratio of the investigated titania films varies between 1.95 and 2.09. The impurities detected in the films (tantalum, molybdenum, silicon, argon, carbon, sodium) can be related to specific deposition conditions. Three multilayer interference systems containing TiO₂ and SiO₂ show large variations in hydrogen content resembling those found for single TiO₂ films.
Glass connecting elements and constructive glass applications
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Kahlert, Wolfgang
[no abstract available]
Practical strength of glass containers : Part 1. Influence of the type of defect
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Müller-Simon, Hayo; Wagner, Jörg; Lenhart, Armin
The practical strength of container glass depends not only on the stress distribution at the surface, but also on the type and distribution of surface defects. After the elimination of the influence of the container shape by means of finite element methods, different types of defect show a different behaviour in the Weibull plot. Especially seeds and blisters are shown to be twice as dangerous as inhomogeneides caused by handling materials. The accuracy of the stress determination is limited, thus, an identification of different types of inhomogeneities from the Weibull plot is not possible under the present conditions.
Glass-ceramic with preferred orientation of Li2Si205 crystals produced by extrusion below crystallization temperature and subsequent heat treatment
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Durschang, Bernward R.; Carl, Gunter; Rüssel, Christian; Marchetti, Kurt; Roeder, Erwin
Glass-ceramics with oriented crystals have been produced from a lithium disilicate glass system by extruding the nucleated glass below the crystallization temperature, and subsequent heat treatment to achieve high-crystalline glass-ceramics. The extruded glass was found to possess a small amount of ahgned, elongated lithium disilicate crystallites and anisotropic stresses. The resulting glassceramic shows a high orientation of the needle-shaped Li₂Si₂O₅ crystals with their c-axis parallel to the extrusion direction. The degree of crystallographic orientation was found to be decreased for samples with an additional heat treatment slightly above Tg, placed between the extrusion process and the crystallization. The crystal alignment of specimens extruded below crystallization temperature is significantly higher than the alignment o f extruded glass-ceramic.
Ultrasonic measurements and complex elastic moduli of silicate glass melts in the viscoelastic and viscous range
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Bornöft, Hansjörg; Brückner, Rolf
The temperature- and frequency-dependence of the ultrasonic velocity and attenuation in glass melts is investigated up to a temperature of 1400 C by means of an equipment for measuring the longitudinal and transversal ultrasonic waves. The range of dispersion and the attenuation maxima are determined at frequencies 0.5 to 4 MHz completely for the DGG standard glass I and for the glass melts (composidons in mol%): 7 4 Si0₂ , 16Na₂O, 10CaO and 7 4 Si0₂ , 16 K₂O, 10CaO and partly for the glass melt 7 4 Si0₂ , 16CS₂O, 10CaO and for the B₂O₃ melt. The whole number of elastic constants follows from the ultrasonic velocities and from the density in the usual way The properties of these glass melts are compared along the temperature and viscosity. The transition from the elastic solid to the viscous fluid can be characterized by the elastic modul and interpreted as a viscoelasdc response of an unrelaxed to a relaxed dynamic network which depolymerizes reversibly with increasing and polymerizes with decreasing temperature. The internal frieden, Q⁻¹ characterizes the inelastic pordon during the periodical stress of the ultrasonic waves. The activation energy of Q⁻¹ obtained via frequencies and temperature of the maxima of is nearly twice the amount of the viscosity activation energy in the same temperature region.
Statistical analysis of viscosity-composition data in glassmaking
(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Öksoy, Dolun; Pye, L. David; Boulos, Edward N.
The objective of this work is to revisit and expand the methods for calculating viscosities of glass with changes in composition that was pioneered by Lakatos, Johansson, and Simmingsköld. Using the data provided by these authors, an empirical statistical model will be presented. This will illustrate the effect of composition change on viscosity that can be expected in a typical glassmaking process.

Browse

Browsing Fachgebiete by Issue Date

Results Per Page

Sort Options