11 research outputs found
Echokardiographische,röntgenologische,perfusionsszintigraphi sche und respiratorische Befunde im Langzeitverlauf nach korrigierender Operation einer partiellen Lungenvenenfehlmündung (PAPVC)
Homogeneity of Li20 - Si02Glasses as Prepared Under Microgravity and 1-g Melting Conditions
Homogeneity of Li2O ? SiO2 glasses as prepared under microgravity and 1 -g melting conditions
Change in Refractive Index of a Borosilicate Glass Fiber Annealed Below the Glass Transformation Temperature
Reaktionskinetik in Glasschmelzen Experiment ES 307 Frischat in der 1. Spacelabmission (FSLP)
TIB: AC 9101 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Quantification of Chemical Striae in Inorganic Melts and Glasses through Picture Processing
Internal friction spectroscopy in Li20-2SiO2 partially crystallised glasses.
Oscillatory torsion deformation experiments were performed on partially crystallised Li2O–2SiO2 glasses in the temperature range 350–480 °C and with frequencies between 20 and 0.002 Hz. The experiments were carried out in a torsion deformation apparatus exerting a small strain on cylindrical samples. Data obtained at varying temperatures and frequency were reduced to master plots using a normalised frequency. The frequency shift factor has been taken as a function of temperature in an Arrhenian form, yielding an activation energy of a background Q−1 close to the activation energy of oxygen defect diffusion (=120 kJ/mol). The master curves of real and imaginary components of shear modulus and internal friction indicate a stretched exponential shear stress relaxation with a an exponent of ≈0.45, characteristic of a broadened relaxation spectrum. The dynamic viscosity was estimated at temperatures of 470 and 480 °C. The extrapolation of dynamic viscosity to zero frequency allowed estimation of the relaxed shear viscosity. The presence of crystals increases the relaxed shear viscosity by ≈0.2log(Pa s)/10 vol.% of crystallinity. Dependence of the relative shear viscosity of partially crystallised lithium disilicate melts on crystal content is discussed