Ceramic bushing for glass ≈ fibre production

Ceramic bushings of different geometries and sizes have been developed for drawing continuous glass fibres as reinforcements. Both pure alumina and stabilised zirconia have been used in fabricating such bushings. The characteristics of fibres drawn through these bushings are shown to be similar to those drawn through conventional platinum-rhodium ones. Alumina bushings have poor corrosion resistance properties with respect to E-glass but are satisfactory for A- and C- glass compositions. Stabilised zirconia bushings give superior performance with regard to E-glass.     

Steady state segregation and heat flow in ESR

A combined theoretical and experimental study of steady-state heat flow and segregation in ESR is presented. The segregation model permits prediction of pressure gradients, hence, interdendritic flow velocities responsible for macrosegregation in the “mushy? zone of axisymmetric ESR ingots. The heat flow model considers the solidus isotherm as a moving boundary. The relationships between power and slag temperature as well as power and heat transfer coefficient are experimentally measured and included in the heat balance equation for the slag. Experiments on both a low-temperature simulated ESR apparatus and on a 200 mm diam ESR ingot mold verify both models.     

Light scattering properties of acacia catechuic acid. Effects of urea and temperature

Association of acacia catechuic acid (ACA) molecules was established in ethanol–water medium². This association was further tested in pure aqueous medium as well as by using urea in increasing amounts in aqueous solutions. The 5M urea depressed the molecular weight to 2.82 × 10⁶, as against 5.04 × 10⁶ in aqueous solution of NaCl or KCl. This reduction has been explained as due either to rupture of the molecule itself or dissociation of molecules which normally remain associated in water. The diminution of root-mean-square end-to-end distance in urea from 323 mμ in water³ to 290 mμ has also been attributed to the disaggregation of the associated molecules. To test this point further, the effect of increasing the temperature was next studied. The molecular weight was observed to be lower at higher temperature (actual value at 47°C was nearly half the original value at 28°C). This considerable reduction positively points to a dissociation of the molecule which was first suspected in our study with urea. The root-mean-square end-to-end distance also diminished to a certain extent, but not so much as the molecular weight. This has been explained as due to the stretching of the molecule when the solvent behaves as a better solvent at higher temperature.